How a LiFePO4 Battery Is Made: From Cell to Pack on One Line

A factory walkthrough of LiFePO4 battery production: slurry mixing and coating, rolling and slitting, winding, electrolyte filling, formation and capacity grading, then pack assembly and burn-in testing.

Most buyers only ever see the finished battery. This walkthrough follows one line from raw powder to a tested pack.

Step 1: Mixing and coating the cathode

We blend LiFePO4 cathode powder with a conductive additive (usually carbon black) and a PVDF binder into a slurry, coat it on both sides of aluminium foil, then run it through an oven to drive off the solvent. Coating thickness and uniformity decide how closely the finished cells match each other.

Step 2: Rolling and slitting

The coated electrode goes through a roller press to hit a set thickness, then gets slit to width. Uneven rolling leaves thick and thin spots, and those show up as problems later at winding.

Step 3: Winding or stacking

Winding rolls the cathode, separator, and anode into a cylindrical or prismatic jelly roll. Stacking lays the electrode sheets one by one, which gives more even internal resistance but runs slower. Small cylindrical cells such as 32650 are wound.

Step 4: Can assembly and electrolyte filling

The jelly roll goes into its can, the terminals get welded, and electrolyte is injected. Filling happens in a dry room held at a low dew point. Moisture inside the cell generates gas and the cell swells.

Step 5: Formation and capacity grading

After filling, the cell gets its first charge to activate it (formation), then a full charge and discharge to measure real capacity (grading). We use grading data to sort cells into matched groups. This is the step that tells you whether a contract manufacturer is serious.

PACK: from cells to a battery

A single cell is 3.2V. To build a 12V, 24V, or 48V battery, cells move to the pack line: matching and grouping, module assembly, laser welding the nickel strips, fitting the BMS, potting or framing, then burn-in testing. The burn-in room runs each pack long enough to catch early failures before shipping.

What to look for on a factory line

Watch for three things: grading equipment, a burn-in room, and whether incoming inspection actually happens. A plant with all three can usually ship consistently.

FAQ

• What are the main stages of LiFePO4 battery manufacturing?
  Two stages: cell production and pack assembly. Cell work covers slurry mixing and coating, rolling and slitting, winding or stacking, can assembly, electrolyte filling, formation, and capacity grading. Pack work covers cell matching, module assembly, laser welding, BMS fitting, and burn-in testing.
• Why can't capacity grading be skipped?
  Grading measures each cell's real capacity and internal resistance, then groups cells by how closely they match. Skip it or fake the numbers and the weakest cell drags the whole pack down, cutting both cycle life and safety margin.

Want the factory walkthrough video or a quote? Contact us with your application and our engineers will spec a system.