Finding
Cell factories are limited by a few physics- and time-bound steps - electrode coating and drying, dry-room area, and formation and aging - so yield and ramp speed decide cost
Cell production runs in three phases: electrode making, cell assembly, and formation and finishing. Coating and drying set line speed and quality; dry rooms held near a -40 C dew point or drier set floor area and energy use; formation and aging tie up chargers, racks and inventory for days to weeks. CATL, BYD, CALB, EVE and Gotion run the largest lines and make about 80% of the world's cells; LG Energy Solution, Panasonic, Samsung SDI and SK On lead outside China.
Yield, more than nameplate, separates winners from failures. Northvolt filed for bankruptcy in Sweden in March 2025 after years of low yield at Skelleftea; Chinese plants ramp to high yield in months. Process changes target the bottlenecks directly: dry-electrode coating, which removes the solvent and the dryer, is in production for Tesla's 4680 cathode at Giga Texas; water-based cathode binders cut NMP recovery; and faster formation protocols reduce rack time. Cell format and chemistry choices, set out below, decide which steps dominate.
Chemistry and format
Chemistries and formats
Format sets assembly method; chemistry sets materials and formation.
| Item | Examples | Advantages | Constraints |
|---|---|---|---|
| NMC and NCA | LG Energy Solution, Samsung SDI, SK On, Panasonic, CATL | Highest energy density; long-range EVs | Nickel and cobalt cost; thermal margins |
| LFP and LMFP | CATL, BYD, CALB, Gotion, EVE | Low cost, long life, thermally stable; about half of EV cells | Lower energy density |
| Sodium-ion | CATL Naxtra, BYD, HiNa | No lithium; good cold performance | Low energy density; early volume |
| Cylindrical | 18650, 2170, 4680, 46-series (Tesla, Panasonic, LG Energy Solution, BMW suppliers) | Fast winding; mature automation; robust can | More cells per pack; lower packing efficiency |
| Prismatic | CATL, BYD Blade, CALB, Samsung SDI | Large format; easy cell-to-pack integration | Swelling management; stacking or winding speed |
| Pouch | LG Energy Solution (GM Ultium), SK On | Light; high energy density | Needs external compression; sealing yield |
Process steps
Process steps end to end
Sequence varies by format; these steps are common to modern gigafactories.
| Step | What happens | Yield killers | Throughput note |
|---|---|---|---|
| Incoming materials | CAM, AAM, binders, solvents, foil and separator sampled and tested | Moisture, impurities, particle-size drift | Upstream defects become downstream scrap |
| Slurry mixing | Active material, binder, conductive carbon and solvent mixed to target rheology | Agglomerates, viscosity drift, contamination | Controllable; poor control propagates into coating |
| Electrode coating | Slot-die coating of cathode on aluminum and anode on copper foil | Thickness variation, streaks, pinholes, edge defects | Hardest step to scale; sets energy density and safety |
| Drying and solvent recovery | Long ovens remove solvent; NMP is recovered and recycled | Residual solvent, cracking, moisture pickup | Common line-speed limiter; large energy load |
| Calendering | Rollers compress electrodes to target density and porosity | Over- or under-compression, cracking | Sets the power-energy tradeoff |
| Slitting and notching | Rolls slit to width; tabs laser-notched | Burrs, particles, edge damage | Edge quality is safety-critical |
| Dry room handling | Moisture-controlled rooms for electrodes, separator and fill | Moisture ingress, particles, static | Floor area and HVAC cost cap expansion |
| Stacking or winding | Electrodes and separator wound (cylindrical) or stacked (prismatic, pouch) | Misalignment, separator wrinkles, particles | Precision-bound; stacking slower than winding |
| Tab welding | Laser or ultrasonic welds to collectors and terminals | High-resistance joints, heat damage | High scrap risk; inline inspection required |
| Enclosure sealing | Jelly roll or stack into can, prismatic case or pouch | Leaks, weak seals, dimensional drift | Usually not reworkable |
| Electrolyte filling | Vacuum injection of electrolyte | Moisture, wrong fill volume, poor wetting | Humidity- and cleanliness-sensitive |
| Wetting rest | Electrolyte infiltrates pores before first charge | Dry spots, trapped gas | Adds queue time |
| Formation | First controlled charge cycles build the SEI and expose early defects | Gassing, lithium plating, high self-discharge | Time-bound bottleneck; racks and inventory tie up capital |
| Aging | Cells rest at controlled temperature so latent defects appear | Impedance or capacity drift, swelling, leaks | Second time-bound limiter |
| Degas and final seal | Formation gas removed (pouch, prismatic); final seal | Leakage, trapped gas | Quality gate before pack lines |
| Testing and grading | Capacity, impedance and self-discharge measured; cells binned | Out-of-family cells, latent defects | Variability lowers usable output |
| Packaging and shipment | Serialized cells packed with traceability | Handling damage, traceability gaps | Not a bottleneck; matters for recalls |
Equipment
Equipment by step
Chinese toolmakers now supply most new lines, including many outside China.
| Tool class | Steps served | Leading suppliers |
|---|---|---|
| Mixers | Slurry mixing | Buhler, Shangshui, Hosokawa |
| Coaters and dryers | Coating, drying, solvent recovery | Wuxi Lead, Yinghe, Hirano Tecseed, Toray Engineering, Durr |
| Calenders and slitters | Calendering, slitting | Naknor, Hitachi Zosen, Wuxi Lead |
| Winding and stacking machines | Cell assembly | Wuxi Lead, Geesun, CIS, Hymson |
| Laser welders | Tab welding, sealing | Hymson, Han's Laser, Trumpf |
| Dry room systems | Humidity control | Munters, Seibu Giken |
| Formation and test systems | Formation, aging, grading | Hangke, Chroma, PNE Solution, Hioki |
Sources
Sources and scope
- Scope
- Battery Cell Manufacturing
- Sources
- IEA Global EV Outlook; company disclosures; equipment maker filings
- Updated
- October 2026