I. What Is Fabric Crease Recovery?

Fabric crease recovery (also known as wrinkle recovery) refers to a fabric’s ability to automatically return to a smooth, flat state after creases are formed by external folding forces. This property directly affects a garment’s ability to maintain its appearance and its wrinkle-resistant qualities, making it one of the key indicators of fabric quality.

In everyday life, the core technical indicator behind concepts such as “non-iron shirts” and “low-maintenance fabrics” is crease recovery. Excellent crease recovery performance means:

Fabrics do not develop noticeable wrinkles easily after wearing; they require little or no ironing after washing; and they maintain a smooth, crisp appearance over the long term.

II. Testing Principles of Crease Recovery

2.1 Testing Mechanism

Crease recovery testing simulates the folding-recovery process of fabric during actual use:

1. Applying deformation: Fold the fabric sample according to specified procedures, apply a standard pressure (typically 500g), and maintain it for a set duration (typically 5 minutes)

2. Releasing stress: After removing the pressure, allow the sample to recover freely

3. Measure the recovery angle: Measure the angle between the sample’s folded surface and the horizontal plane (recovery angle); a larger angle indicates better recovery.

2.2 Two Main Testing Methods

Horizontal Method: The sample is folded horizontally, and vertical pressure is applied; this is the method commonly used in international standards.

Vertical Method: The sample is folded while suspended vertically; this method is required by specific standards.

III. Detailed Explanation of Testing Standards

BS EN 22313 / ISO 2313

- Specifies the test procedure for the horizontal method

- Applicable to all types of woven fabrics

- Test conditions: 500 g pressure, 5-minute loading time

AATCC 66

- Uses the vertical method for testing

- Widely used in the North American market

- Data differs from the ISO method; direct comparison is not possible

GB/T 3819

- Equivalent to ISO 2313

- Applicable to crease recovery testing of all types of textiles

- The mainstream method in China’s textile testing laboratories

IV. Testing Equipment and Operating Procedures

4.1 Core Equipment

Components of the Crease Recovery Tester

Pressure Application Device: Precision pressure weight (500 g ± 5 g)

Timing System: Precise control of pressure application and recovery times

Angle Measurement: Dedicated protractor or digital measurement system

Environmental Control: Standard atmospheric conditions (20 ± 2°C, 65 ± 2% RH)

4.2 Standard Test Procedure

Step 1: Sample Preparation

Cut test specimens of specified dimensions from the sample; take several specimens in both the warp and weft directions (typically 5 each); condition them under standard atmospheric conditions for at least 24 hours.

Step 2: Folding and Pressing

Fold the specimen in half with the right side facing inward (or as required by the standard); place it in the pressing device and apply a pressure of 500 g; maintain this pressure for 5 minutes ± 5 seconds.

Step 3: Free Recovery

Quickly release the pressure and transfer the test specimens to the recovery device; allow the specimens to recover freely for 5 minutes ± 5 seconds

Step 4: Angle Measurement

Measure the angle between the two surfaces using a dedicated protractor; record the recovery angle value (accurate to 1 degree)

Step 5: Result Calculation

Calculate the average recovery angle for the warp and weft directions separately; calculate the total recovery angle (warp + weft) if necessary

V. Key Factors Affecting Crease Recovery

5.1 Fiber Factors

Polyester (polyester fiber): Excellent recovery, high elastic modulus, and molecular chains that readily return to their original shape

Wool: Good recovery, excellent elastic recovery properties

Nylon: Moderate recovery, performance decreases significantly after moisture absorption

Cotton: Poor recovery, high rigidity of cellulose molecules, prone to forming hydrogen bonds that fix creases

Rayon: Poor recovery, low wet modulus, extremely prone to wrinkling

5.2 Fabric Structure Factors

Fabric Density: Denser fabrics generally exhibit better recovery

Yarn Twist: High-twist yarns help improve recovery

Fabric Weave: Plain < Twill < Satin (recovery increases in this order)

Fabric Thickness: Thinner fabrics are more prone to permanent wrinkles

VI. Application and Interpretation of Test Results

6.1 Classification of Recovery Angle Grades (for reference)

6.2 Anisotropy Analysis

The recovery angles of a fabric’s warp and weft directions often differ:

1. High warp recovery angle: Indicates good wrinkle resistance in the longitudinal direction.

2. High weft recovery angle: Indicates good wrinkle resistance in the transverse direction.

3. Significant difference between the two: Suggests that the fabric may have uneven weaving or finishing.

6.3 Practical Application Guidelines

Recommendations for apparel manufacturers:

1. Business shirt fabrics: Recommended total recovery angle (warp + weft) ≥ 250°

2. Casual pants fabrics: Recommended total recovery angle ≥ 220°

3. Home textile products: Recovery angle requirements may be appropriately relaxed

VII. Frequently Asked Questions and Solutions

Q1: Why do test results for the same fabric vary when tested multiple times?

Possible causes:

1. Insufficient acclimatization of the test specimen

2. Differences in sampling location (performance varies between the fabric edge and the center)

3. Inconsistent testing procedures (application and release speeds)

Solution: Strictly adhere to standard conditions, increase the number of test specimens, and calculate the average

Q2: How should data from ISO methods be converted to AATCC methods?

Note: The two methods are based on different principles, so there is no exact conversion formula. Recommendations:

1. For exports to Europe and the U.S.: Prioritize AATCC 66 testing

2. For general trade: Use ISO 2313 or GB/T 3819

3. For internal quality control: Use a single method consistently and establish a company database

Q3: How can fabric crease recovery be improved?

Technical approaches:

1. Select fibers with inherent elasticity (e.g., polyester-spandex blends)

2. Optimize fabric structure (appropriately increase density)

3. Apply resin finishing or liquid ammonia finishing

4. Develop new types of elastic composite yarns

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In the textile industry, flame-retardant textiles are being used in an increasingly wide range of applications—from industrial protective workwear and decorative fabrics in public spaces to infant and children’s clothing and vehicle interiors. Their flame-retardant properties directly impact personal safety and environmental safety. This article outlines the testing methods, core standards, and key considerations during the testing process for flame-retardant textiles, providing a reference for industry professionals.

I. Testing Methods for Flame-Retardant Textiles

The core of testing flame-retardant textiles lies in evaluating the fabric’s combustion behavior when exposed to a flame source, including key indicators such as flame spread rate, after-flame time, smoldering time, degree of damage, and smoke emission. Currently, mainstream testing methods are primarily divided into five categories, each tailored to different application scenarios with distinct testing principles and focuses.

(1) Vertical Burning Test

The vertical burning test is the most commonly used and fundamental flame-retardant testing method, suitable for most apparel textiles, protective clothing, bedding, and similar products. Its core principle is to simulate the combustion characteristics of fabric in a vertically suspended state. The testing principle involves clamping the test specimen vertically in place and applying a standard ignition source (typically a Bunsen burner with a flame height of 40 mm) to the lower edge of the specimen for a specified duration (usually 12 seconds) before removing the flame. The specimen’s after-flame time, smoldering time, and the length of damage after combustion are then recorded to assess the fabric’s flame-retardant performance.

The advantages of this method include its simplicity and broad applicability. It provides an intuitive reflection of the fabric’s flame-retardant performance under actual wearing or hanging conditions, making it the preferred method for factory-exit inspections and routine laboratory testing. Relevant standards include GB/T 5455-2014, ISO 15025, and ASTM D6413, among others; specifications regarding flame height, ignition duration, and pass criteria vary slightly across different standards.

(2) Horizontal Burning Test

The horizontal burning test is primarily suitable for lightweight textiles, decorative fabrics (such as curtains and tablecloths), and plastic-coated fabrics, simulating the burning scenario when the fabric is placed horizontally. The test principle involves placing the specimen horizontally on a specific stand, igniting it from one end with a flame source, observing the spread of the flame, and measuring the flame spread rate and the length of damage. Some standards also require recording whether molten droplets are produced during combustion.

Compared to the vertical burning method, the horizontal burning method places greater emphasis on evaluating a fabric’s flame spread capability when laid flat, making it particularly suitable for textiles that are typically placed horizontally during daily use. Common standards include GB/T 2408-2021, ASTM D635, and ISO 6941. Among these, GB/T 2408-2021 accommodates both vertical and horizontal combustion modes, meeting the testing requirements for a wide range of fabrics.

(3) 45-Degree Combustion Method

The 45-degree combustion method is primarily designed for hanging textiles, such as curtains, drapes, and stage curtains. It simulates the combustion characteristics of these fabrics when hung at an angle. The testing principle involves securing the test specimen at a 45-degree angle to the horizontal plane, igniting it from the bottom, measuring the burn time and extent of damage, and evaluating the flame spread rate along the inclined surface of the fabric.

This method closely mirrors the actual usage scenarios of hanging textiles, accurately reflecting the diffusion patterns of flames on inclined surfaces and avoiding result discrepancies caused by mismatched testing angles. Common standards include the U.S. NFPA 701 (divided into the stricter Class 1 and the general Class 2) and China’s GB/T 5456-2015. Among these, NFPA 701 serves as the core reference standard for flame-retardant testing of hanging textiles worldwide and is widely used in the inspection of export products.

(4) Limiting Oxygen Index (LOI) Method

The Limiting Oxygen Index (LOI) method is a quantitative testing method suitable for the precise evaluation of textile flame-retardant performance, particularly for quality control during the R&D phase and for high-end products. The testing principle involves placing the sample in an environment of a nitrogen-oxygen mixture and gradually adjusting the oxygen concentration until the minimum oxygen concentration required for the sample to sustain combustion (i.e., the Limiting Oxygen Index, LOI) is determined. A higher value indicates stronger flame-retardant performance of the fabric.

Generally, an LOI ≥ 28% is classified as flame-retardant fabric, while an LOI ≤ 20% indicates flammable fabric. The advantage of this method lies in its precise and quantifiable test results, which provide scientific data support for product development and standard formulation. Relevant standards include the international ISO 4589-2, China’s GB/T 5454-1997, and the U.S. ASTM D2863, among others. This method serves as a crucial testing tool for textile enterprises to enhance product quality.

(5) Supplementary Testing for Special Applications

In addition to the four basic methods described above, flame-retardant textiles intended for special applications must undergo specific testing:

1. Smoke Density Testing: Simulates the smoke emission from burning fabrics in enclosed spaces (such as subways and airplanes). Smoke density (Ds value) is measured using the light attenuation method to prevent asphyxiation caused by smoke during a fire. Common standards include GB/T 8627-2007 and ISO 5659-2;

2. Thermal Radiation Test: Designed for industrial protective clothing and fabrics used in high-temperature environments, this test simulates high-temperature radiation scenarios to evaluate the fabric’s thermal protection performance (TPP value). Relevant standards include GB 8965.1-2023 and ISO 13506;

3. Wash fastness testing: Evaluates the durability of flame-retardant properties in fabrics after repeated washing. Typically, fabrics are processed according to the washing procedures specified in GB/T 8629-2017, followed by basic flame-retardant testing to ensure the fabric remains compliant even after long-term use;

4. Smoke toxicity testing: For interior fabrics used in buildings and vehicles, this test measures the release of toxic gases during combustion to prevent secondary harm. Common standards include GB/T 20284-2006 and BS 6853.

II. Standards for Flame-Retardant Textiles

(1) GB Series

GB/T 17591-2025, implemented in 2025, is the latest core standard. It replaces the 2006 edition and further refines testing criteria and classification requirements.

1. GB/T 17591-2025 “Flame-Retardant Fabrics”: A core recommended standard covering flame-retardant fabrics for apparel, decoration, and industrial use. It introduces eight new terms, including burn length, smoke density, and thermal protection performance values. It adjusts test items and performance requirements for different applications—such as interior decoration, vehicle interiors, and flame-retardant protective clothing—including the addition of Class B3 requirements for interior decoration fabrics and smoke density grading for automotive interior fabrics.

2. GB/T 5455-2014 “Textiles—Flame Resistance—Determination of Vertical Burn Length, Smoldering Time, and Afterglow Time”: A recommended standard corresponding to the vertical burning method, applicable to routine flame-retardant testing of various textiles. It specifies sample preparation, testing procedures, and acceptance criteria, and is a commonly used standard for factory-exit testing;

3. GB 8965.1-2023 “Protective Clothing—Flame-Retardant Protection—Part 1: Flame-Retardant Clothing”: A mandatory standard for industrial flame-retardant protective clothing. It specifies test items such as vertical burning and thermal radiation, introduces new Class B2 and B3 requirements, and adjusts metrics such as burn length and after-flame time. It applies to protective workwear used in open-flame and high-temperature environments, such as firefighter uniforms and welding workwear;

4. GB 31701-2015 “Technical Specifications for the Safety of Textile Products for Infants and Children”: A mandatory standard for infant and children’s clothing. It requires flame-retardant performance to meet Class B standards (burn length ≤ 200 mm, after-flame time ≤ 5 s) and strictly prohibits the use of flammable fabrics to ensure children’s safety;

5. GB 8624-2012 “Classification of Fire Performance of Building Materials and Products”: Applicable to flame-retardant textiles used in construction (such as curtains and carpets), this standard classifies fire performance into four levels: A (non-combustible), B1 (difficult to ignite), B2 (combustible), and B3 (flammable), and specifies the testing requirements and acceptance criteria for each level.

(2) International and Regional Standards

1. ISO Series Standards (Internationally Recognized): Core standards include ISO 4589-2 (Limiting Oxygen Index Method), ISO 6940 (Vertical Burning), ISO 6941 (Horizontal Burning), and ISO 15025 (Vertical Burning, applicable to apparel fabrics), with relatively universal performance requirements;

2. ASTM Series Standards (U.S. Standards): Published by the American Society for Testing and Materials (ASTM), these standards are highly targeted. Commonly used standards include ASTM D6413 (Vertical Burning of Textiles), ASTM D3801 (Flame Retardancy of Children’s Sleepwear), ASTM E84 (Smoke Density of Textiles for Construction), and ASTM F1959 (Arc Flash Protection Testing). Among these, 16 CFR 1615/1616 is the mandatory flame retardancy standard for children’s sleepwear, with extremely strict requirements: it must pass the vertical burning test with a burn length ≤ 17.8 cm;

3. EN Series Standards (European Union Standards): Unified European standards applicable to products sold in the EU market. Key standards include EN 13501-1 (classification of combustion performance of construction products, rated from Class A to Class F based on a combined assessment of smoke generation and melting droplets), EN ISO 11925-2 (small flame test), and EN 13773 (curtain fabrics). These standards impose more detailed requirements regarding smoke density and toxic gas emissions, which companies exporting to the EU must strictly adhere to;

4. Standards for Other Regions: The UK BS series (BS 5852 for flame-retardant testing of furniture fabrics, BS EN 11611 for welding protective clothing) and the Japanese JIS series (JIS L 1091 for flame-retardant testing of textiles). Select the appropriate standards based on the requirements of the target market.

III. Applicable Scenarios and Precautions

(1) Selection of Applicable Scenarios

1. Worn textiles (clothing, sleepwear): The vertical burning test (GB/T 5455, ASTM D6413) should be prioritized. Children’s clothing must additionally comply with mandatory standards such as GB 31701 and 16 CFR 1615/1616;

2. Hanging decorative fabrics (curtains, drapes): Prioritize the 45-degree burn test (NFPA 701, GB/T 5456). Fabrics for architectural use must also meet the classification requirements of GB 8624 and EN 13501-1;

3. Industrial protective clothing: Select the vertical burn test combined with thermal radiation testing (GB 8965.1, ASTM F1959) to ensure protective performance in high-temperature and open-flame environments;

4. Vehicle interiors (automobiles, aircraft, trains): Combine the vertical burning test, smoke density test, and smoke toxicity test to comply with standards such as GB/T 17591-2025 and EN 45545-2; for aircraft and train interior fabrics, additional smoke density rating assessments are required;

5. Product R&D/High-End Customization: Prioritize the limiting oxygen index method (ISO 4589-2, GB/T 5454) to precisely quantify flame-retardant performance and optimize product formulations.

(2) Key Testing Considerations

1. Sample Preparation: Samples must be representative, drawn from different batches and locations, and meet standard dimensional requirements; They must also undergo standard pre-treatment (e.g., conditioning) to ensure the samples are in a stable state;

2. Environmental Control: Test environment temperature and humidity must comply with standard specifications;

3. Equipment Calibration: Testing instruments (e.g., combustion testers, oxygen index analyzers) must be calibrated regularly to ensure the accuracy of parameters such as flame height, oxygen concentration, and temperature measurements;

IV. The Importance of Flame Retardant Testing Instruments

Professional flame retardant testing instruments must be compatible with various testing methods and standards. They can accurately measure key indicators such as after-flame time, smoldering time, limiting oxygen index, and smoke density. Characterized by ease of operation, data accuracy, and high stability, these instruments not only meet the needs of enterprises for factory-exit inspections and R&D testing but also provide reliable testing equipment support for third-party testing institutions.

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As the global lithium battery industry enters 2026, it is becoming increasingly clear that manufacturing capability—not laboratory-level electrochemical breakthroughs alone—will determine which technologies succeed at scale. Over the past decade, lithium-ion battery performance improvements were primarily driven by materials innovation: higher-nickel cathodes, silicon-doped anodes, improved electrolytes, and optimized additives. However, as energy density gains begin to slow and safety, cost, and sustainability pressures intensify, the industry’s center of gravity is shifting. From my perspective as a manufacturing engineer and system integrator with more than 23 years of experience, the next phase of competition will be defined by equipment architecture, process stability, and factory-level scalability. Technologies such as dry electrode processing and solid-state batteries are often discussed in terms of materials science, yet their real barriers lie in manufacturability. Without corresponding upgrades in production equipment and process control, these technologies cannot move beyond pilot-scale demonstrations.

This article analyzes the 2026 lithium battery manufacturing technology trends from an equipment and process engineering standpoint. It focuses on how dry electrode and solid-state battery technologies are reshaping production line requirements, and it provides a practical equipment upgrade roadmap for manufacturers planning their next-generation factories.

Why Equipment Upgrades Are Now the Critical Bottleneck

In traditional lithium-ion battery production, the industry has achieved a relatively mature balance between materials, process parameters, and equipment reliability. Conventional wet-process electrode manufacturing, liquid electrolyte filling, and formation protocols are well understood, and yield optimization follows established methodologies.

However, emerging battery technologies disrupt this balance in three fundamental ways:

1. Process windows become narrower – New materials and structures are less tolerant of variation.

2. Legacy equipment reaches physical limits – Machines designed for slurry-based coating or liquid electrolytes cannot be easily adapted.

3. Scale-up risks increase exponentially – Laboratory success does not translate linearly into mass production.

As a result, equipment design is no longer a downstream consideration. It must be co-developed with the battery technology itself, particularly for dry electrode and solid-state systems.

Dry Electrode Technology: Redefining Electrode Manufacturing Equipment

1. From Slurry Coating to Solid-State Film Forming

Dry electrode technology eliminates solvents and slurry mixing, replacing them with powder-based compaction, fibrillation, and film forming processes. While this approach offers clear advantages—lower energy consumption, reduced environmental impact, and shorter production cycles—it fundamentally changes equipment requirements.

Traditional coating lines rely on: - Slurry mixing systems - Slot-die or comma coaters - Long drying ovens - Solvent recovery units

Dry electrode lines, by contrast, require: - High-precision powder feeding systems - Controlled fibrillation or binder activation mechanisms - High-pressure calendering and film densification equipment - Inline thickness and density monitoring

2. New Equipment Challenges

From an engineering standpoint, dry electrode processing introduces several non-trivial challenges:

• Powder uniformity control: Unlike liquids, powders exhibit segregation, agglomeration, and flow instability.

• Mechanical stress management: Excessive compaction can damage active materials or conductive networks.

• Process repeatability: Small variations in pressure or temperature can lead to large performance deviations.

At TOB New Energy, our engineering teams have observed that many early dry electrode pilot lines fail not because of material chemistry, but because equipment lacks sufficient process control resolution.

Solid-State Batteries: Equipment Must Enable Interfaces, Not Just Assembly

1. The Manufacturing Reality of Solid-State Cells

Solid-state batteries promise improved safety and potentially higher energy density, yet they also impose unprecedented demands on manufacturing equipment. Unlike liquid electrolyte systems, solid-state cells are interface-dominated systems. The quality of contact between solid electrolyte and electrodes determines ionic conductivity, cycle life, and reliability.

This shifts the role of equipment from simple assembly to interface engineering.

2. Key Equipment Requirements for Solid-State Production

Solid-state battery manufacturing requires equipment capable of:

• High-precision layer stacking and alignment

• Uniform pressure application during lamination

• Controlled atmosphere handling for moisture-sensitive materials

• Low-damage densification and sintering processes (where applicable)

Many existing lithium-ion assembly machines cannot meet these requirements without substantial redesign. For example, standard lamination equipment may lack the pressure uniformity or feedback control needed for solid electrolyte layers.

Traditional vs. New-Generation Manufacturing Processes

The following table summarizes the key differences between conventional lithium-ion battery manufacturing and emerging dry electrode and solid-state processes from an equipment perspective.

This comparison highlights a critical point: new battery technologies demand disproportionately higher equipment sophistication, even when overall process steps appear simpler.

Equipment Upgrade Roadmap for 2026–2028

Based on our internal projects and customer collaborations, TOB New Energy recommends a phased equipment upgrade strategy rather than abrupt technology replacement.

Phase 1: Hybrid Lines and Modular Upgrades

Manufacturers should begin with hybrid production lines that retain proven downstream processes (assembly, formation, aging) while selectively upgrading upstream equipment such as:

• Dry electrode pilot modules

• Advanced calendering systems with closed-loop control

• Enhanced metrology and inline inspection

This approach reduces capital risk while allowing teams to accumulate process data.

Phase 2: Dedicated Pilot Lines

Once process stability is demonstrated, dedicated pilot lines should be deployed with:

• Fully customized electrode fabrication equipment

• Solid-state compatible lamination and stacking systems

• Expanded environmental control (humidity, particulate levels)

At this stage, the focus shifts from feasibility to yield optimization and reproducibility.

Phase 3: Mass Production Line Engineering

For full-scale deployment, equipment design must prioritize:

• Long-term mechanical stability

• Maintainability and spare part standardization

• Integration with MES and quality traceability systems

In our experience, many scale-up failures occur because pilot-line equipment is directly copied into mass production without redesign for continuous operation.

Expert Insight: TOB Engineers’ View on Future Capacity

According to internal projections by TOB New Energy’s engineering team, by 2030, more than 30% of newly built lithium battery production capacity will incorporate dry electrode or solid-state–compatible equipment architectures.

However, this does not imply an immediate replacement of conventional lines. Instead, we expect a prolonged period of coexistence, where traditional wet processes dominate high-volume applications, while advanced equipment-enabled technologies serve high-performance, safety-critical, or sustainability-driven markets.

Our engineers also anticipate that equipment suppliers capable of customization, rapid iteration, and cross-technology integration will play a decisive role in enabling this transition.

Conclusion: Manufacturing Capability as Strategic Advantage

As we look beyond 2026, it is evident that the lithium battery industry is entering a manufacturing-driven era. Dry electrode and solid-state technologies will not succeed solely on the basis of materials innovation. Their success depends on whether equipment systems can deliver process stability, scalability, and economic viability.

For battery manufacturers, the key strategic question is no longer “Which chemistry is best?” but rather “Which technology can we manufacture reliably at scale?” The answer to this question will be shaped by equipment upgrade decisions made today.

At TOB New Energy, we believe that engineering depth, customization capability, and real-world factory experience are essential to navigating this transition. By aligning technology ambition with manufacturing reality, the industry can move from promising concepts to sustainable, large-scale energy storage solutions.

In all-solid-state batteries, the liquid electrolyte is replaced by a solid-state electrolyte membrane. Consequently, the front-end production process requires the preparation of this solid electrolyte film in addition to the traditional positive and negative electrode sheets. This process is a critical link in the battery manufacturing workflow, directly determining the performance and quality of the final cell. While the wet process currently dominates solid-state battery production lines, the dry process is increasingly becoming the mainstream direction for next-generation solid-state battery front-end technology, thanks to its combined advantages in cost, process efficiency, and material compatibility.

01. Key Upgrades in Solid-State Battery Pre-Forming Production

The manufacturing process for solid-state batteries fundamentally differs from that of traditional liquid batteries. The front-end film preparation segment is the critical, transitional phase in the battery manufacturing process. This stage directly dictates the finished cell's energy density, rate performance, and cycle life. In all-solid-state batteries, the solid-state electrolyte membrane replaces the liquid electrolyte. Therefore, front-end preparation must include not only the conventional positive and negative electrode sheets but also the solid-state electrolyte film. This fundamental change introduces new challenges and simultaneously presents opportunities for process upgrading.

02. Technological Transformation: The Leap from Wet to Dry Process

Current solid-state battery front-end preparation processes are mainly categorized into two technical routes: wet and dry. The wet process still relies on the solvent system of traditional liquid batteries, where electrode or electrolyte materials are mixed with a binder to form a slurry, coated, and then dried to complete film formation.

While this process is relatively mature, it has inherent drawbacks: it requires the use of large amounts of toxic organic solvents (such as NMP), necessitates high-energy-consumption steps for drying and solvent recovery, and restricts the application of certain cutting-edge materials sensitive to solvents.

In contrast, the dry process innovates electrode manufacturing by eliminating the use of solvents and the subsequent drying step. The dry process relies more heavily on high-shear dry mixing and fibrillation equipment to achieve uniform material dispersion and pre-forming, followed by multi-roll pressing to complete the film formation directly.

The core advantages of dry film formation technology are evident across three dimensions:

• Cost Efficiency: By omitting the coating, drying, and solvent recovery stages, equipment investment is lower, energy consumption is reduced, and overall cell manufacturing costs can be reduced by approximately 18%.

• Performance Enhancement: The dry process effectively increases the active material's compaction density, leading to an energy density increase of about 20%. SAIC Group's semi-solid-state battery, integrated into its MG4 model, has achieved a system energy density of 400Wh/kg, supporting a 12-minute fast charge for 400 km.

• Environmental and Material Compatibility: The dry process eliminates the need for toxic solvents, solving the environmental pollution issues of the traditional wet process. Concurrently, it enables the application of more cost-effective materials (such as manganese-based cathodes).

03. Technology Matrix: Diversified Paths for Dry Film Formation

Dry film formation is not a single process but a matrix encompassing various technical routes. Currently, the more representative dry electrode preparation technologies primarily include six types:

• Fibrillation Method: Uses high shear force to fibrillate the binder, enabling it to tightly encapsulate active materials and conductive agents, forming a self-supporting electrode film. This process demands extremely high shear force and temperature control capabilities from the equipment.

• Dry Spray Deposition: Utilizes charged powder, which is uniformly deposited onto the current collector under an electric field, followed by hot pressing to melt and fix the binder, forming a self-supporting film.

• Other Methods: Vapor deposition, hot-melt extrusion, direct pressing, and 3D printing are applied based on different material characteristics and application scenarios.

These different paths vary in technical principles, applicable materials, film-forming capability, and equipment complexity, and are suited for different applications such as large-scale, flexible electrodes, small-sized devices, and thick electrode sheets.

Comparison of Major Dry Film Formation Technical Routes

The industry generally considers the Binder Fibrillation Method to exhibit superior performance stability and processability, positioning it as the emerging mainstream route.

04. Industrialization Challenges: Bridging the Gap from Laboratory to Mass Production

Despite the clear advantages of dry film formation, scaling from the laboratory to mass production faces numerous hurdles. Capacity and efficiency are paramount concerns. Dry coating capacity and speed still lag behind traditional wet processes, and uniformity and adhesion performance during wide-format spraying require significant improvement.

Coating uniformity and quality control present another major challenge. Non-uniform dry electrode coatings can create "hot spots" within the electrode, leading to accelerated battery performance degradation and potential safety risks.

Binder and material compatibility also need further optimization. Achieving uniform distribution of PTFE fibrils within the mixture while preventing damage to active material particles is essential. Furthermore, PTFE is unstable at low potentials and reacts irreversibly with lithium, which limits its application in negative electrodes.

Challenges on the equipment side are equally severe. The dry process imposes higher demands on core roller-pressing machinery. The performance and production efficiency of the calendaring machine as the core equipment are central to determining the dry process's viability for mass production.

TOB NEW ENERGY is actively working to address these challenges, aiming to control the binder content in the negative electrode to 0.7% and the positive electrode below 1.5% to achieve more efficient, low-cost film-forming performance.

05. Equipment Innovation: The Critical Force Driving Dry Process Implementation

Equipment typically spearheads the industrialization of solid-state batteries. In the realm of dry film formation, equipment innovation is the key driver for technological implementation.

• Front-End Process Equipment: Accounts for approximately 32% of the entire production line's value, including core equipment for high-efficiency mixing, material dispersion, coating, and high-shear treatment.

• Mid-End Process Equipment: Accounts for approximately 45% of the line's value, centered around high-efficiency stacking machine (25% of the line's value) and horizontal isostatic presses (13% of the line's value), covering the entire process from shaping to densification.

• Back-End Process Equipment: Accounts for approximately 23% of the line's value, including dry powder comprehensive testers and horizontal high-temperature fixture solutions for solid-state battery integrated cabinets, achieving high-voltage formation and capacity grading and assembly.

06. TOB NEW ENERGY: Providing Comprehensive Solutions from Laboratory to Mass Production

Addressing the industrialization opportunities and challenges of dry film formation technology, TOB NEW ENERGY leverages years of technical accumulation in battery manufacturing to offer customers a complete solution spanning from the laboratory to mass production.

Solutions for Laboratory-Scale Dry Electrode Lines

We provide a full suite of customized equipment and services for dry electrode experimental lines. Our developed Laboratory Jet Mill integrates miniaturization, intelligence, and high precision, suitable for experimental-grade powder preparation needed for the fibrillation of lithium battery dry electrode materials. The Lab Dry Electrode Film Forming Machine is a laboratory dry electrode research equipment that can be used for the powder to film forming process.

Solutions for Pilot-Scale Production

We offer Dry Electrode Film Forming Machines that support various production line requirements, including equipment for GWh-level mass production capacity. Through precise tension control and thickness adjustment, we can achieve the preparation of dry electrode sheets as thin as 27μm or even thinner.

Solutions for Industrial Mass Production

For industrial mass production needs, we provide complete dry electrode production line solutions. Our system covers all processes, including controllable feeding, film formation, thinning, current collector compounding, and quality inspection. Product width can reach 1000mm, with a thickness range of 40-300μm, and is compatible with 2 to 6 dry electrode sheets operating in parallel for high-efficiency production.

Our technical team deeply understands every aspect of the dry film formation process and can provide customized process optimization solutions based on the client’s specific material systems (such as graphite/silicon-carbon negative electrodes, ternary/LFP positive electrodes, and various all-solid-state electrode materials) and equipment needs. On the materials front, we support our clients with cutting-edge battery materials, including specialized binders and modified conductive agents suitable for the dry process, ensuring optimal compatibility between materials and process.

Formation and capacity grading are among the final and most critical stages in lithium-ion battery manufacturing. Although these steps occur after electrode fabrication and cell assembly, they strongly influence the electrochemical stability, safety performance, consistency, and lifetime of the final product. In industrial battery production lines, the formation process activates the battery for the first time, while the grading process evaluates and classifies the cells based on measurable electrical parameters.

From an engineering perspective, these operations are not simple charging and testing procedures. Each step — electrolyte filling, aging, formation, secondary filling, K-value evaluation, and capacity grading — is designed based on electrochemical mechanisms, mass transport behavior, gas evolution, and quality control requirements. In modern battery factories, the design of these processes must be integrated with the overall production line layout, equipment capability, and target performance specifications. For manufacturers building new facilities, these steps are typically implemented as part of a complete lithium battery production line solution, where formation systems, aging rooms, and grading machines are configured according to capacity and chemistry requirements.

This article provides a detailed engineering explanation of each step in the formation and capacity grading process, together with the physical and chemical reasons behind the operations.

1. First Electrolyte Filling After Cell Assembly

During the first filling, the assembled cell is placed in a vacuum filling chamber. The chamber is evacuated to create negative pressure inside the cell. Once the internal pressure is sufficiently low, the electrolyte valve is opened, and the electrolyte flows into the cell due to the pressure difference. This method ensures that the electrolyte penetrates into the separator pores and electrode structure more efficiently than simple atmospheric filling.

The purpose of the first filling is not only to introduce electrolyte, but also to ensure uniform wetting of porous electrodes. Poor wetting can lead to high internal resistance, non-uniform SEI formation, and capacity loss in later stages.

2. High-Temperature Aging for Electrolyte Wetting

The cells are placed in a controlled high-temperature aging room for a specified period to accelerate electrolyte diffusion into the electrode pores. Proper wetting is essential for stable SEI formation during the subsequent formation process.

During aging, the cell is not yet permanently sealed. Therefore, a temporary sealing pin must be used to close the filling port. Without temporary sealing, high temperature may cause electrolyte evaporation, leading to concentration change, performance instability, and potential safety hazards.

Table 1 — Purpose of High-Temperature Aging

3. Formation Process and SEI Film Generation

During the first charge, the electrolyte decomposes at the graphite surface, forming a thin but dense SEI layer. This layer allows lithium ions to pass while preventing further electrolyte decomposition. The quality of the SEI film directly determines cycle life, internal resistance, and safety.

To obtain a high-quality SEI film, formation is usually performed using a multi-step current profile.

Gas generation occurs during formation because electrolyte decomposition produces gases such as CO₂and hydrocarbons. To avoid gas accumulation at the electrode interface, industrial production often usesnegative-pressure formation, where gas is removed during the process.

Gas trapped between electrode layers can block lithium-ion transport paths, leading to non-uniform SEI formation and performance variation between cells.

In modern factories, formation systems are designed together with the
battery formation and grading equipment, ensuring precise current control, temperature stability, and gas management.

4. Secondary Electrolyte Filling

Two main reasons require this step:

As a result, the electrolyte amount inside the cell becomes lower than the designed value. Secondary filling compensates for the loss and ensures correct electrolyte volume.

The operation is similar to the first filling, but the filling quantity is smaller. After the second filling, the filling port is welded to permanently seal the cell.

Table 2 — Comparison of First and Second Filling

5. OCV Measurement and High-Temperature K-Value Test

The purpose is to calculate thehigh-temperature K-value, which describes the self-discharge rate of the battery.

The formula is:

K = (OCV1−OCV2) / (T2−T1)

Unit: mV/h

The cell is stored at elevated temperature between the two measurements. A large K-value indicates abnormal voltage drop, which may be caused by internal leakage, contamination, or micro-short circuits.

Cells with excessive K-value must be removed before grading.

Table 3 — Interpretation of High-Temperature K-Value

6. Capacity Grading (Formation Test Cycling)

In industrial production, grading is usually performed at relatively high current (0.5C–1C) to simulate actual operating conditions.

Cells are then sorted into different grades according to measured capacity.

Example classification:

Grading machines must provide accurate current control, temperature management, and high channel consistency, which is why they are normally integrated into a
battery pilot line or production line solution rather than used as standalone equipment.

7. Room-Temperature K-Value Test After Depolarization

Right after charge and discharge, the voltage drops quickly due to relaxation of the electrode potential. If OCV is measured immediately, the calculated K-value will be artificially high.

Therefore, cells are stored for a period until voltage becomes stable, then a second K-value test is performed at room temperature.

This test further removes defective cells before shipment.

8. Final Release of Qualified Cells

- First filling

- Aging

- Formation

- Second filling

- High-temperature K test

- Capacity grading

- Room-temperature K test

the cells can be released from the factory.

Although these steps occur at the end of the process, they determine whether the battery will meet its design specifications. Incomplete formation, poor wetting, insufficient electrolyte, or inaccurate grading will directly reduce cycle life and consistency.

For this reason, the formation and grading section is often the most power-consuming, time-consuming, and equipment-intensive part of a battery factory, and must be considered at the early stage of plant design.

About TOB NEW ENERGY

Learn more about complete solutions: TOB NEW ENERGY Battery Production Solutions

Electrode slurry preparation is one of the most critical yet underestimated steps in lithium-ion and sodium-ion battery manufacturing. Problems such as particle sedimentation, agglomeration, poor dispersion uniformity, and unstable viscosity often originate at the slurry stage, but their consequences propagate downstream into coating defects, capacity inconsistency, and yield loss.

This article systematically explains why slurry sedimentation and agglomeration occur, how key process parameters such as mixing speed and vacuum level influence slurry quality, and how to select a suitable vacuum mixer from an engineering perspective. The content is written for battery manufacturers, R&D centers, and pilot-line engineers seeking stable, scalable, and reproducible slurry preparation.

1. Why Do Electrode Slurries Sediment and Agglomerate During Mixing?

1.1 Sedimentation Caused by Density Differences and Insufficient Shear

Electrode slurries consist of high-density solid materials (active materials, conductive additives) dispersed in relatively low-density liquid phases (NMP or water-based solvents). Typical cathode and anode powders-such as NCM, LFP, graphite, silicon–graphite composites, or hard carbon-have densities several times higher than the solvent system.

If the shear force generated during mixing is insufficient, gravitational forces dominate over suspension forces, causing heavier particles to gradually settle. This phenomenon becomes more severe under the following conditions:

• High solid loading formulations (>50–60 wt%)
• Large batch volumes with limited flow circulation
• Long dwell times between process steps

Sedimentation leads to vertical composition gradients in the slurry. The bottom layer becomes over-concentrated with solids, while the upper layer becomes binder- and solvent-rich. Once such gradients form, they are difficult to eliminate and directly affect coating thickness uniformity, electrode density, and electrochemical consistency.

1.2 Agglomeration Driven by Surface Energy and Binder Bridging

Agglomeration originates from the high surface energy of fine powders. Nano- or micron-scale particles tend to cluster together to minimize total surface energy. In battery slurries, this natural tendency is amplified by process-related factors.

Common causes include:

• Rapid powder feeding without sufficient pre-wetting
• Binder added too early, forming localized polymer bridges
• Inadequate shear stress to break initial clusters

Once agglomerates form, they behave as large pseudo-particles that are resistant to dispersion. These hard clusters often survive the entire mixing process and later appear as pinholes, streaks, or localized resistance anomalies in coated electrodes.

1.3 Air Entrapment as a Hidden Root Cause

Air introduced during powder addition or high-speed atmospheric mixing becomes trapped inside particle clusters. These air pockets prevent solvent penetration and block effective wetting of internal particle surfaces.

Without degassing, trapped air stabilizes agglomerates and worsens sedimentation behavior. This is why slurries mixed under atmospheric conditions often show acceptable appearance initially but degrade rapidly during storage or transfer.

2. How Do Mixing Speed and Vacuum Level Affect Slurry Fineness and Stability?

2.1 Mixing Speed: Controlling Shear and Dispersion Efficiency

Mixing speed directly determines the magnitude of shear stress applied to particle clusters. As rotational speed increases:

• Agglomerates experience stronger mechanical forces
• Binder and conductive additives distribute more uniformly
• Solid–liquid contact efficiency improves

However, increasing speed alone has limitations. Excessive speed under atmospheric conditions can introduce new air, raise slurry temperature, and accelerate binder degradation. Therefore, mixing speed must be optimized rather than maximized.

2.2 Vacuum Level: Enhancing Wetting and Degassing

Vacuum fundamentally changes slurry behavior. Under reduced pressure, entrapped air expands and escapes from the slurry, allowing solvent to penetrate particle clusters more effectively.

At high vacuum levels (typically −0.08 to −0.095 MPa):

• Air bubbles are rapidly removed
• Powder wetting becomes more complete
• Binder penetrates micro-pores within agglomerates

This results in finer dispersion, lower apparent viscosity fluctuation, and improved long-term slurry stability.

2.3 Synergistic Effect of Speed and Vacuum

Engineering data consistently show that:

• Increasing speed alone improves fineness but quickly reaches a plateau
• Vacuum alone improves wetting but requires shear to break clusters
• Vacuum combined with appropriate speed delivers the best dispersion efficiency

In practice, vacuum acts as a multiplier for shear effectiveness, enabling high-quality dispersion without excessive mechanical stress.

3. How to Select the Right Vacuum Mixer for Electrode Slurry Preparation?

3.1 Limitations of Conventional Atmospheric Mixers

Traditional planetary or paddle mixers operating at atmospheric pressure are limited by:

• Incomplete air removal
• Poor repeatability at high solid loadings
• Long mixing cycles with inconsistent results

These limitations become critical when scaling from laboratory formulations to pilot and mass production.

3.2 Key Equipment Features Required for Stable Slurry Production

A vacuum mixer designed for battery electrode slurries should meet the following engineering requirements:

3.3 Typical Application Scenarios

Vacuum mixers are widely used in:

• High-energy-density cathode slurry preparation (NCM, NCA)
• High-viscosity silicon–graphite anode systems
• Sodium-ion battery electrode development
• R&D and pilot lines requiring high formulation repeatability

In production environments, vacuum mixers enable process standardization, which is essential for yield control, scale-up, and quality assurance.

Conclusion

Sedimentation and agglomeration in electrode slurries are not random defects but predictable physical phenomena driven by density differences, surface energy, and air entrapment.

From an engineering perspective:

• Mixing speed controls shear force
• Vacuum level controls wetting and degassing efficiency
• Proper vacuum mixer selection allows both factors to work synergistically

By understanding these mechanisms and selecting appropriate equipment, battery manufacturers can achieve stable, reproducible, and scalable slurry preparation-laying a solid foundation for high-quality electrode production.

About TOB NEW ENERGY
TOB NEW ENERGY is a one-stop solution provider for battery laboratory lines, pilot lines, and mass production lines. With deep expertise in electrode slurry preparation, mixing process design, and customized battery equipment, TOB supports global battery manufacturers, research institutes, and universities in building stable, scalable, and reproducible electrode manufacturing systems.
Learn more about TOB NEW ENERGY’s battery equipment and engineering solutions

Introduction: Why Battery Laboratory Design Matters More Than Ever in 2026

In 2026, lithium battery laboratories are no longer isolated research spaces dedicated only to material discovery. They have become critical engineering bridges between fundamental electrochemistry and industrial-scale manufacturing.

Over the past five years, battery innovation cycles have shortened significantly. New chemistries-such as sodium-ion systems, high-silicon anodes, solid-state electrolytes, and dry electrode processes-are now expected to move from laboratory validation to pilot-scale demonstration within 18–36 months.

As a result, laboratory infrastructure must meet three simultaneous requirements:

● Support high-variability experimental research

● Maintain process consistency and reproducibility

● Enable direct transfer to pilot and mass production environments

This 2026 laboratory checklist is structured to reflect these realities. Rather than listing equipment randomly, it organizes laboratory construction around budget tiers, cell formats, and engineering objectives, ensuring that every investment contributes to long-term scalability.

I. Low-Budget Laboratory Setup

Positioning: Fundamental research and feasibility validation

 1. Core Infrastructure (All Cell Types)

2. Coin Cell Laboratory (CR20xx)

3. Cylindrical Cell (18650 / 21700 – Feasibility Level)

4. Pouch Cell (Single-layer)

II. Mid-Budget Laboratory Setup

Positioning: Process optimization and pilot validation

1. Infrastructure Upgrade

2. Coin Cell (High-Throughput)

3. Cylindrical Cell (18650 / 21700 / 32140)

4. Pouch Cell (Multi-layer)

III. High-Budget Laboratory / Pilot Facility

Positioning: Direct production transfer

1. Production-Grade Infrastructure

2. Cylindrical Cell (Pilot Level)

3. Pouch Cell Pilot Line

4. Advanced Safety & Analysis

Conclusion

A lithium battery laboratory in 2026 must be designed as a scalable engineering system, not a collection of isolated tools.

From low-budget research labs to pilot-scale facilities, each equipment decision should serve a clear engineering purpose: enabling reliable data, reducing scale-up risk, and accelerating the transition to production.

At TOB NEW ENERGY, laboratory systems are engineered as the first controllable stage of manufacturing, ensuring that innovation can move efficiently from concept to commercialization.

Lithium-ion battery manufacturing is a multidisciplinary engineering process that integrates electrochemistry, materials science, precision machinery, thermal engineering, automation control, and factory-level system design. Although the basic working principle of lithium-ion batteries is well known, the industrial realization of stable, high-yield, and high-performance cell production requires far more than simply following a laboratory recipe. In real manufacturing environments, product consistency depends on the interaction between process parameters, equipment accuracy, environmental control, and line integration. Even small deviations in coating thickness, slurry viscosity, electrode density, or moisture level can result in significant differences in capacity, internal resistance, safety performance, and cycle life.

For this reason, companies planning to enter battery manufacturing must understand the complete production workflow before purchasing equipment or designing a factory. In large projects, the manufacturing process cannot be treated as a series of independent machines. Instead, it must be designed as a continuous engineering system covering electrode preparation, cell assembly, electrolyte filling, formation, aging, and testing. Professional planning of the production line, utility systems, and cleanroom environment is essential to avoid costly redesign later. In practical projects, many failures occur not because of material chemistry, but because the manufacturing process was not properly engineered from the beginning.

As a one-stop provider of battery equipment and factory solutions, TOB NEW ENERGY lithium-ion battery production line solutions are developed to support the complete life-cycle from laboratory research to pilot scale and full mass production, ensuring that equipment compatibility, process scalability, and future expansion are considered during the initial design stage.

This article provides a detailed engineering-level explanation of the lithium-ion battery manufacturing process, focusing on real industrial workflow rather than simplified laboratory descriptions.

1. Overall Structure of Lithium-Ion Battery Manufacturing

Although different cell formats such as cylindrical, pouch, and prismatic require different assembly methods, the overall production flow of lithium-ion batteries follows a similar structure. The entire manufacturing system can be divided into three major stages: electrode preparation, cell assembly, and electrochemical activation with testing. Each stage contains multiple processes that must be precisely controlled to ensure final product quality.

In industrial projects, these stages must be designed together rather than separately. A well-engineered production line requires correct matching of machine capacity, material flow, drying length, cleanroom level, and power supply capability. For this reason, professional battery factory layout and line design solutions are usually required before equipment procurement begins.

2. Electrode Preparation: Foundation of Battery Performance

Electrode preparation is the most critical part of lithium-ion battery manufacturing because the microstructure formed during this stage directly determines energy density, cycle life, internal resistance, and safety characteristics. Once electrodes are produced, most performance parameters cannot be corrected in later steps, which is why industrial factories invest heavily in high-precision coating and calendering systems.

2.1 Slurry Mixing Engineering

The first step is preparing cathode and anode slurry by mixing active materials, conductive additives, binder, and solvent. In laboratory scale, mixing may appear simple, but in industrial production the slurry must maintain stable viscosity, uniform particle distribution, and repeatable rheological behavior over long production runs. Variations in dispersion quality will lead to coating defects, uneven thickness, and capacity variation between cells.

Modern production lines use vacuum planetary mixers or double-planetary mixers with precise temperature and speed control. For research institutes and pilot plants, flexible parameter adjustment is essential, which is why battery slurry mixing equipment for R&D applications must support multiple material systems and small batch sizes.

2.2 Precision Coating Process

After mixing, the slurry is coated onto current collectors. The coating process must control thickness, weight, and uniformity across the entire width of the electrode. Even slight thickness variation may cause capacity imbalance during formation. Industrial lines usually use slot-die coating technology because it allows continuous production with high precision and low material waste, while doctor-blade coating is still widely used in laboratory and pilot environments due to its flexibility.

In high-capacity factories, coating machines are often integrated with multi-zone drying ovens to maintain continuous production without interrupting material flow.

2.3 Drying and Solvent Removal

The drying process removes solvent from the coated electrode while preserving the designed microstructure. This step requires careful control of temperature gradient, air flow speed, and solvent recovery system. If drying is too fast, cracks may form in the coating layer. If drying is insufficient, residual solvent may remain, leading to gas generation during formation.

Industrial coating lines usually include long convection ovens with multiple heating zones. In addition to temperature control, modern factories must also consider energy efficiency and solvent recycling to reduce operating cost.

2.4 Calendering and Density Control

Calendering compresses the dried electrode to achieve the target density and porosity. Higher density increases energy density, but excessive compression reduces ionic transport and may shorten cycle life. Therefore, calendering parameters must be optimized according to the material system and cell design.

Pilot lines often require adjustable roll pressure and temperature to support different research projects, which is why scalable equipment design is important when building a battery pilot line.

2.5 Slitting and Dust Control

After calendering, the wide electrode roll is cut into narrow strips. This process must avoid burrs and particles because metal dust can cause internal short circuits. Industrial slitting machines include tension control systems, edge trimming, and dust collection units to maintain clean electrode surfaces.

3. Cell Assembly: Mechanical Structure Formation

Once electrodes are prepared, the next stage is assembling the cell structure. The assembly method depends on cell format, but the engineering principles are similar. The process must ensure accurate alignment, clean environment, and reliable electrical connections.

Stacking machines require high positioning accuracy, while winding machines must maintain stable tension to avoid wrinkles. Welding of tabs is another critical step because poor welding increases internal resistance and heat generation during cycling. Industrial production usually uses ultrasonic welding or laser welding depending on tab material and thickness.

Packaging must be performed in cleanroom conditions to prevent dust contamination. Electrolyte filling requires vacuum equipment to ensure complete penetration into the electrode pores. Finally, sealing must guarantee long-term hermeticity to prevent moisture ingress.

Proper cleanroom design is part of factory engineering and should be considered together with equipment layout.

4. Formation, Aging, and Testing

Formation is the electrochemical activation process in which the solid electrolyte interface (SEI) is formed on the anode surface. This step requires precise current control and temperature management. It is also one of the most expensive sections of a battery factory because thousands of channels must operate simultaneously for long periods.

Formation equipment occupies a large area and requires strong power supply capacity, which must be considered during factory planning. Incorrect estimation of formation capacity is a common mistake in new battery projects.

5. Importance of Production Line Integration

In industrial battery manufacturing, process stability depends not only on individual machines but also on how the entire line is integrated. The coating speed must match the drying length, the slitting speed must match assembly capacity, and formation channels must match daily output. Utility systems such as compressed air, chilled water, vacuum, and power supply must also be designed according to production scale.

For this reason, many companies prefer working with a one-stop battery equipment supplier that can provide process design, equipment manufacturing, installation, and commissioning as a complete package instead of purchasing machines from multiple vendors.

6. From Laboratory Research to Mass Production

Most battery projects start from laboratory research, then move to pilot scale, and finally to mass production. Equipment selection should consider this transition. Laboratory machines should allow parameter flexibility, pilot lines should support small-batch stability, and production lines must focus on automation and yield. Choosing scalable equipment reduces development time and avoids repeated investment.

TOB NEW ENERGY provides complete solutions covering laboratory equipment, pilot lines, and turnkey production lines, allowing customers to maintain consistent process parameters while increasing production capacity.

About TOB NEW ENERGY

TOB NEW ENERGY is a professional supplier of lithium-ion battery equipment and complete production line solutions serving battery manufacturers, universities, research institutes, and new energy companies worldwide. The company provides full support from laboratory research to pilot scale and mass production, including factory layout design, equipment manufacturing, installation, commissioning, and operator training.

With extensive experience in lithium-ion, sodium-ion, solid-state, lithium-sulfur, and dry electrode technologies, TOB NEW ENERGY delivers customized engineering solutions that help customers build reliable, scalable, and future-ready battery manufacturing facilities.

Pouch cell batteries are widely used in consumer electronics, electric vehicles, and energy storage systems because of their high energy density, lightweight structure, and flexible design. Compared with cylindrical and prismatic cells, pouch cells use laminated aluminum laminated film as the outer packaging instead of a rigid metal case. This structure allows better space utilization and lower weight, but it also makes the sealing process much more critical. Any defect in the sealing area may lead to electrolyte leakage, moisture ingress, gas escape, or internal contamination, which can seriously affect battery performance, safety, and cycle life. For this reason, sealing quality control is one of the most important steps in pouch cell manufacturing.

Sealing leakage in pouch cells is rarely caused by a single factor. In most cases, it is the result of interactions between process parameters, material properties, equipment condition, and environmental factors. Even when each parameter appears to be within specification, small deviations can combine to create weak sealing interfaces or microscopic leakage paths. From an engineering perspective, leakage causes can be broadly categorized into three groups: process-related issues, material-related defects, and contamination or handling problems. Understanding how these factors affect the sealing interface is essential for identifying root causes and implementing effective countermeasures.

1. Process-Related Causes

The heat sealing process is highly sensitive to temperature, pressure, and time. These three parameters determine whether the inner polymer layer of the pouch film can fully melt, flow, and bond into a continuous interface. If any of these parameters are not properly controlled, sealing defects can occur.
One common issue is insufficient sealing temperature. When the temperature is too low, the inner sealing layer does not melt completely, resulting in weak bonding and poor adhesion. Although the seal may appear intact visually, the interface may contain micro-voids that can later develop into leakage paths. Conversely, excessive temperature can degrade the polymer or damage the adhesive layer between the aluminum foil and the outer film, reducing mechanical strength and causing delamination over time.
Pressure is equally important. Insufficient pressure prevents the molten polymer from fully contacting and filling surface irregularities, while excessive pressure can squeeze out the molten layer, reduce sealing thickness, or even damage the aluminum layer. Uneven pressure distribution across the sealing area can create regions of inconsistent bonding strength, which are particularly prone to leakage under mechanical stress.
Sealing time also plays a critical role. If the dwell time is too short, the polymer may not have enough time to flow and bond properly. If it is too long, overheating or material deformation may occur. In high-speed production lines, maintaining consistent sealing time across all cells becomes more challenging, increasing the risk of variability in seal quality.

2. Material-Related Causes

The quality and consistency of the aluminum laminated film directly affect sealing performance. Variations in film thickness, coating uniformity, or adhesive bonding between layers can lead to inconsistent sealing behavior. For example, if the inner sealing layer has uneven thickness, some areas may melt and bond properly while others remain under-sealed.
Defects in the film, such as pinholes, scratches, or micro-cracks, can also create leakage paths. These defects may originate during film manufacturing, transportation, or handling. Even if the sealing process is well controlled, a defective film cannot provide reliable barrier performance.
Material compatibility is another important factor. The sealing behavior depends on the melting characteristics of the inner polymer layer. If different batches of film have slightly different melting temperatures or compositions, the same sealing parameters may not produce consistent results. This is particularly critical in large-scale production, where small variations in material properties can lead to significant differences in yield.
Electrode and tab materials can also influence sealing quality. The presence of metal tabs in the sealing area introduces discontinuities in the interface. If the sealing parameters are not optimized for these regions, gaps or weak bonding may occur around the tabs, making them a common source of leakage.

3. Contamination and Handling Issues

Contamination in the sealing area is one of the most frequent causes of leakage in real production environments. Substances such as electrolyte residue, dust particles, or electrode debris can prevent proper bonding between the polymer layers. Even a small amount of contamination can create a micro-channel that allows gas or liquid to pass through the seal.
Electrolyte contamination is particularly problematic. During filling and handling, small amounts of electrolyte may spread to the sealing area. Because electrolyte components can interfere with polymer bonding, their presence can significantly reduce sealing strength. In some cases, the seal may initially appear acceptable but fail during storage or cycling due to chemical interaction at the interface.
Improper handling can also damage the pouch film before sealing. Scratches, folds, or mechanical deformation can weaken the film structure, making it more susceptible to leakage. Misalignment during sealing may result in uneven pressure distribution or incomplete sealing width, further increasing the risk of defects.

4. Equipment and Tooling Factors

The condition and design of sealing equipment also play a significant role. Worn or contaminated sealing heads can lead to uneven temperature distribution or inconsistent pressure. If the heating element does not maintain a stable temperature across the entire sealing width, some areas may be under-sealed while others are overheated.
Tooling alignment is another critical factor. Misaligned sealing jaws can create uneven pressure distribution, leading to weak bonding in certain regions. In addition, insufficient control of cooling after sealing can affect the crystallization and solidification of the polymer layer, influencing final seal strength.

5. Summary of Leakage Causes

The main causes of pouch cell sealing leakage can be summarized as follows:

• Improper heat sealing parameters (temperature, pressure, time)
• Variations or defects in aluminum laminated film
• Contamination in the sealing area (electrolyte, dust, particles)
• Mechanical damage or misalignment during handling
• Equipment instability or poor maintenance

In practice, leakage is often the result of multiple factors acting together rather than a single isolated issue. For example, a slightly low sealing temperature combined with minor contamination may be enough to create a leakage path that would not occur if either factor were controlled independently.

About TOB NEW ENERGY

TOB NEW ENERGY is a leading provider of one-stop battery manufacturing solutions, covering pouch cell lab lines, pilot lines, and pouch cell production lines. Our services include customized battery equipment supply, process optimization, battery material support, and technical training for battery engineers and R&D teams worldwide.

As the global battery industry seeks alternatives to lithium-based chemistries, sodium-ion batteries have steadily moved from academic research into early-stage commercialization. Among various cathode candidates, NFPP (Na₃Fe₂(PO₄)₃) has gained increasing attention due to its balanced performance, structural stability, and supply-chain advantages. Rather than pursuing extreme energy density, NFPP represents a pragmatic materials strategy aimed at cost control, safety, and long service life.

This article explores NFPP from a materials and manufacturing perspective, examining why it is considered one of the most realistic cathode options for near-term sodium-ion battery deployment.

01. Why NFPP Matters in Sodium-Ion Battery Development

Sodium-ion batteries differ fundamentally from lithium-ion systems in ionic radius, diffusion kinetics, and electrode–electrolyte compatibility. These differences impose stricter requirements on cathode structure and chemical stability.

NFPP belongs to the NASICON-type phosphate framework, a structure known for its three-dimensional sodium-ion diffusion channels. This framework provides:

● Stable crystal structure during repeated Na⁺insertion and extraction

● Moderate operating voltage around 3.0–3.2 V vs. Na/Na⁺

● Good thermal and chemical stability compared with layered oxides

From an industrial perspective, NFPP does not rely on nickel, cobalt, or other high-cost metals. Iron and phosphate-based chemistries offer predictable pricing and lower geopolitical risk, which aligns well with large-scale stationary energy storage and low-cost mobility applications.

02. Structural Characteristics: NASICON Framework as a Stability Anchor

The electrochemical behavior of NFPP is closely linked to its crystal structure. The NASICON framework consists of rigid PO₄tetrahedra and FeO₆octahedra, forming interconnected channels for sodium-ion transport.

Key structural advantages include:

● Low volume change during cycling, reducing mechanical stress

● Stable Fe³⁺/Fe²⁺redox couple with limited side reactions

● Inherent resistance to oxygen release at elevated temperatures

While NFPP does not match layered oxide cathodes in theoretical energy density, its structural robustness translates into long cycle life, especially under high-temperature or high-rate operating conditions.

03. Electrochemical Performance: Trade-Offs That Favor Reliability

In practical sodium-ion cells, NFPP typically delivers:

● Specific capacity in the range of 110–120 mAh/g

● Excellent capacity retention over extended cycling

● Stable performance under moderate to high C-rates

The relatively flat voltage plateau simplifies battery management system (BMS) design and improves state-of-charge estimation accuracy. For applications where predictability and durability outweigh peak energy density, NFPP offers a compelling balance.

It is worth noting that ongoing research focuses on particle size control, carbon coating, and dopant modification to further enhance rate capability and electronic conductivity.

04. Manufacturing Compatibility: Designed for Process Stability

One often-overlooked advantage of NFPP is its process friendliness. Compared with moisture-sensitive layered oxides, phosphate-based materials demonstrate higher tolerance to ambient processing conditions.

From electrode manufacturing to cell assembly, NFPP shows:

● Good compatibility with conventional slurry-based coating processes

● Potential adaptability to emerging dry electrode technologies

● Stable behavior during calendaring and electrode densification

These characteristics reduce manufacturing risk when scaling from laboratory cells to pilot and mass production lines.

05. Application Scenarios: Where NFPP Fits Best

NFPP is not positioned as a universal replacement for lithium-ion cathodes. Instead, it targets specific scenarios where sodium-ion technology offers system-level advantages:

● Grid-scale and distributed energy storage systems

● Low-speed electric vehicles and two-/three-wheel mobility

● Backup power and industrial energy storage solutions

In these applications, cost per cycle, safety margin, and supply stability often outweigh volumetric energy density.

06. From Materials to Manufacturing: An Integrated Perspective

Successful deployment of NFPP-based sodium-ion batteries depends not only on material performance but also on the integration of equipment, process control, and quality assurance.

Companies such as TOB NEW ENERGY support this transition by providing integrated solutions covering material preparation, electrode processing, and complete sodium-ion battery production lines. By aligning material characteristics with manufacturing capabilities, NFPP-based systems can move more efficiently from development to commercialization.

Conclusion

NFPP is not a breakthrough material defined by extremes. Instead, it represents a well-engineered compromise—offering stability, safety, and economic feasibility in a rapidly evolving battery landscape. As sodium-ion batteries continue to mature, NFPP stands out as one of the most industrially realistic cathode materials available today.