Prismatic Cell Battery Production Process: A Comprehensive Guide

Introduction

Prismatic aluminum-case batteries have become increasingly popular in electric vehicles (EVs) and energy storage systems (ESS) due to their high volumetric efficiency, mechanical robustness, and ease of modular assembly. Compared to cylindrical and pouch cells, prismatic cells offer a balance between energy density, thermal performance, and mechanical strength. This article outlines the full production process, from raw materials to the final assembled battery pack.

Cathode Materials

Common cathode materials include:

Lithium Iron Phosphate (LFP)

Nickel Manganese Cobalt Oxide (NMC)

Lithium Nickel Cobalt Aluminum Oxide (NCA)

These materials are synthesized via solid-state reactions at high temperatures (typically 700-900°C) to achieve high crystallinity.

Anode Materials

The anode is usually made from:

Graphite (Artificial or Natural)

Silicon-Carbon Composite (for high energy cells)

The raw materials are processed to achieve optimized particle size, surface area, and tap density.

Electrolyte

The electrolyte is typically a lithium salt (LiPF6) dissolved in a mixture of organic solvents such as EC (ethylene carbonate), DMC (dimethyl carbonate), and additives to enhance stability and performance.

Separator

Prismatic cells typically use multi-layer polypropylene (PP) or polyethylene (PE) separators, with thickness ranging from 12μm to 20μm, ensuring mechanical strength and thermal stability.

Slurry Preparation

Cathode: Active material + Conductive agent (carbon black) + Binder (PVDF) mixed with NMP solvent.

Anode: Graphite + Conductive agent + Binder (CMC+SBR) mixed with deionized water.

Slurry Mixing Equipment: High-shear mixer, planetary mixer.

Coating

The prepared slurry is evenly coated onto metal foils:

Cathode: Coated on aluminum foil.

Anode: Coated on copper foil.

Coating Method: Slot die coating or comma bar coating.

Drying

The coated foils are dried in continuous drying ovens, removing solvents (NMP or water) under precisely controlled temperatures.

Cathode drying: 120-140°C

Anode drying: 80-120°C

Calendaring

Both electrodes pass through a pair of precision rollers to compress the coating, ensuring:

Uniform thickness.

Higher electrode density.

Better contact between active material and current collector.

Calendaring Density Targets:

Cathode: 2.8-3.5 g/cm³

Anode: 1.4-1.8 g/cm³

Slitting

After calendaring, the electrodes are slit into narrow strips, matching the cell design.

Tab Welding

Current collector tabs (aluminum for cathode, copper for anode) are welded to the electrodes.

Stacking

Prismatic cells typically use Z-fold stacking or lamination stacking, where cathode, separator, and anode are alternately stacked into a compact sandwich structure.

Case Insertion

The stacked electrode assembly is inserted into a pre-formed aluminum case, made from aluminum alloy (usually 3003 or 1060).

Electrolyte Injection

The electrolyte is injected into the case under vacuum to ensure full wetting of all internal surfaces.

Electrolyte Filling Precision: ±0.5g per cell.

Pre-Sealing

After electrolyte filling, the cell is pre-sealed to temporarily protect the internal environment during the formation process.

The cells undergo an initial charge and discharge process called formation, which allows the SEI (Solid Electrolyte Interphase) layer to form on the anode surface.

Formation Temperature: 25-45°C.

Formation Current: 0.05-0.1C (slow to ensure uniform SEI).

After formation, gas produced during SEI formation is removed through a vacuum degassing process, ensuring cell internal pressure is optimized.

The aluminum case is hermetically sealed using laser welding or ultrasonic welding, ensuring:

Excellent hermeticity.

Mechanical strength.

Some designs also add a safety vent to release pressure if internal gas builds up during abnormal operation.

Each cell undergoes comprehensive testing, including:

Capacity test: Full charge/discharge cycle.

Internal resistance: AC impedance test (typically at 1 kHz).

Leakage test: Helium leak detection.

Open circuit voltage (OCV): Monitoring for self-discharge.

Dimension check: Ensuring size tolerance within spec.

Tested prismatic cells are combined into modules using:

Laser welding or ultrasonic welding for busbars.

Integration of Battery Management System (BMS) for monitoring voltage, temperature, and balancing.

Thermal management systems (TMS) are also integrated, typically using:

Cooling plates (liquid cooling).

Thermal interface materials (TIM) for better heat dissipation.

Prismatic cell batteries combine high safety, mechanical strength, and flexible design, making them ideal for demanding applications such as electric vehicles and stationary storage. While the production process shares commonalities with cylindrical and pouch cells, the precise handling of the aluminum case, electrolyte filling, and sealing process are critical factors affecting performance and reliability.