2025 lithium battery cell manufacturing methods

Lithium battery cell is the core unit of new energy industry, and the precision of its manufacturing process directly determines the energy density, safety performance and cycle life of the battery. Despite China’s leading position in the global lithium battery production capacity, the manufacturing process of the battery cell is still facing multiple challenges such as material compatibility, process consistency and equipment precision. This article will be from the manufacturing process, quality control system, technology bottlenecks and innovation direction of the three dimensions, systematic analysis of 2025 years of lithium battery core manufacturing complexity and key technologies.

I. Core manufacturing process: multi-process precision synergy

Lithium battery core manufacturing covers the three core links of electrode preparation, core assembly and post-processing, involving the control of hundreds of key process parameters. Small deviations in any one of the links may lead to battery performance degradation or safety hazards, and there is also a close coupling between the various links.

(i) Electrode preparation: material molding with micron-level precision

Electrode manufacturing is the foundation of battery cell performance, and the core lies in realizing uniform dispersion and stable combination of active materials, spanning chemistry, materials, machinery and other multidisciplinary technologies.

1. Batching and mixing

Positive electrodes are mostly made of ternary or lithium iron phosphate materials, with conductive agents, binders and solvents; negative electrodes are mainly made of graphite and use water-based solvents.

Mixing requires strict control of speed, time and temperature to avoid excessive mixing leading to molecular chain breakage or uneven dispersion.

2. Coating and drying 

The coating is done by slit extrusion, and the thickness deviation should be controlled within ±2% to avoid edge thickening or pinhole defects.

Drying requires a gradient temperature rise to prevent surface crusting or solvent residue. Emerging microwave and infrared drying technologies are improving efficiency and consistency.

3. Roller pressing and slitting 

Roller pressing improves electrode density and affects volumetric energy density, and needs to be balanced with compaction and rebound control.

Slitting needs to control burrs and cut surface quality, and laser cutting is gradually replacing mechanical blades to improve precision and reliability.

(ii) Battery cell battery core assembly: the structure and process of the high degree of adaptability

According to the type of battery (cylindrical, square, soft pack) to choose the winding or stacking process, the equipment positioning accuracy and automation level puts forward very high requirements.

1. Battery cell winding/stacking 

High winding efficiency, suitable for mass production, but extremely sensitive to the alignment of the pole piece; 

Stacking high space utilization, more suitable for high-energy-density battery cells, Z-stacking and thermal composite technology is promoting efficiency breakthroughs.

2. Battery cell welding and encapsulation 

The welding of lugs mostly adopts ultrasonic or laser process, which needs to control the resistance and heat-affected zone; 

Laser sealing of hard-shell batteries needs to accurately control the depth of fusion, and heat sealing of soft packs needs to match the temperature-pressure-time, so as to ensure the sealing is reliable.

(iii) Post-processing: activation and consistency screening

Activating the battery cells and realizing consistent performance through liquid injection, chemical formation and capacity separation will directly determine the quality level of the batch.

1. Liquid injection and formation 

Liquid injection should be carried out in an environment with dew point <-40℃, and vacuum assistance can improve the infiltration efficiency; 

Formation forms a stable SEI film by charging and discharging with small current, which affects the first-time efficiency and lifespan.

2. Capacity Separation and Inspection 

Capacity Separation test the actual capacity, according to the performance classification, to provide a basis for module assembly; 

Final inspection including appearance, size, voltage, internal resistance, etc., AI vision system significantly improve the defect detection rate and efficiency.

II. Quality control system: the whole chain parameter synergy

Core manufacturing not only needs to control a single point of the process, but also needs to realize the multi-dimensional synergy of materials, processes, and environment, and build a traceable and early warning quality system.

(i) Key quality control points and standards

1. Material quality control 

Positive and negative electrode materials should be strictly screened for purity, particle size and crystal structure, and the impurity content should be controlled at ppm level; 

Diaphragm puncture strength and porosity should be matched with electrochemical performance, and the thickness and surface condition of substrate foils should directly affect the coating quality.

2. Process control 

The fluctuation of coating thickness and surface density should be <±2%, and the precision of roll thickness should be ±1µm; 

SPC (Statistical Process Control) is adopted to monitor the key parameters in real time, and early warning of process drift.

3. Environmental control 

Drying room dew point to maintain <-40 ℃, cleanliness up to Class 100, to prevent water and oxygen interference; 

temperature and humidity according to the process customization, such as mixing needs to be a constant temperature, welding needs to be controlled humidity.

(ii) Digitalization and Intelligent Quality System

• Manufacturing Execution System (MES) realizes the whole process of data collection and traceability, and builds the “digital twin” of electric core.;
• Machine vision is applied to detect defects, welding quality and size of pole piece, and the deep learning algorithm continuously improves the recognition accuracy;
• Process Simulation and Optimization Through digital twin, we can verify the process plan in advance, shorten the trial production cycle and reduce the risk of innovation.

III.Technical bottlenecks and innovation direction

Despite the continuous progress of lithium battery manufacturing, the balance between high energy density, high safety and low cost is still facing a number of challenges to promote technological innovation to the deep development.

(I) Current Core Challenges

1. Material compatibility 

High-nickel positive electrode is sensitive to moisture and oxygen, and the whole manufacturing process requires atmosphere control; 

Silicon based negative electrode has a large volume expansion rate, and is prone to cracking and pulverization in the cycle.

2. Lack of process maturity 

Although dry electrode eliminates solvent, coating uniformity and adhesion still need to be improved; 

Solid-state battery electrolyte film formation, interface regulation and traditional liquid system have big differences, so both equipment and process need to be reconstructed.

3. Equipment precision bottleneck 

Thinning of electrodes (<5µm) puts forward higher requirements for coating and rolling equipment; 

The existing production line is not flexible enough, and the cost of transferring production is high, which slows down the technology iteration.

(II) Frontier Innovation Trends

1. Material system innovation 

Lithium manganese iron phosphate to improve cycle life through doping; 

Silicon-carbon composite anode to alleviate volume expansion, with pre-lithiation to improve the first efficiency; 

solid electrolyte R&D to focus on improving conductivity and interface stability.

2. Process and equipment upgrading 

Dry electrode, inkjet printing and other solvent-free technologies to reduce energy consumption and costs; 

Intelligent welding and robot vision guidance to improve assembly precision and flexibility; 

X-ray, EIS and other non-destructive testing technologies to provide deep information for quality judgment.

3. Green and Intelligent Manufacturing 

Solvent recovery rate >95%, the regeneration efficiency of decommissioned battery materials exceeds 80%; 

Digital twin and industrial Internet integration to achieve process self-optimization and predictive quality control.

Conclusion

Lithium battery cell manufacturing is a precision project that integrates materials, processes, equipment and system control, and its complexity not only constitutes industry barriers, but also drives continuous technological innovation. In the future, the core manufacturing will pay more attention to the whole chain synergy, data-driven and green low-carbon, and only by striking a balance between high consistency, high technology maturity and cost control, can we continue to lead in the global new energy competition.