The most critical step in lithium-ion cell manufacturing is formation: cells are charged for the first time and their internal structure stabilises. Thermal runaway risk is at its highest during this process. FM Global DS 7-112 sets specific rules for the formation area.
Risk Profile of the Formation Process
- Electrolyte reactions during first charge form the solid electrolyte interphase layer
- Temperature rises as part of normal operation, but crossing a defined threshold becomes critical
- Cell defects can produce an internal short circuit and initiate runaway
- Cumulative risk: hundreds of cells are being processed in parallel
Facility Design
- The formation area is isolated from other production stages
- Fire-rated separating construction
- Mechanical ventilation at a high air change rate
- Explosion relief panels in the roof or side walls
- An emergency protocol that takes all cells to a safe state
Sprinklers and Early Warning
- Foam-water or high-K sprinklers
- Aspirating smoke detection sampling at cell level
- Gas detection for carbon monoxide and hydrogen as an early indicator
- Thermal imaging for continuous cell temperature monitoring
- A battery management system tracking voltage, current and temperature
Isolation and Reignition Prevention
- After a fire, affected cells are held in an isolated area for an extended period
- Reignition monitoring by continuous thermal imaging and gas detection
- Damaged cells are removed in dedicated containers, submerged or covered
- Personnel re-entry only once gas readings and temperatures are confirmed clear
Quick Checklist
- Formation area isolated behind fire-rated construction
- High ventilation rate with explosion relief
- Layered warning: aspirating detection, gas detection and thermal imaging
- Foam-water or high-K sprinkler protection
- Battery management system monitoring at cell level
- Extended isolation period for reignition control
Frequently Asked Questions
Why is the formation stage the highest risk step in cell manufacturing?
Formation is the first time the cell is charged, and it is when the internal chemistry stabilises. Any manufacturing defect that will cause an internal short circuit tends to reveal itself here, while hundreds of cells are being processed in parallel. That combination of first energisation and high cell density is what makes it the critical area.
Why does a formation area need explosion relief?
Cells in thermal runaway vent flammable gases including hydrogen. In an enclosed process area those gases can accumulate and ignite, producing a pressure rise the structure cannot contain. Explosion relief panels give that pressure a controlled path out, protecting the building envelope and the rest of the plant.
What detection is used in a battery formation area?
A layered arrangement: aspirating smoke detection sampling close to the cells for very early warning, gas detection for carbon monoxide and hydrogen, thermal imaging for continuous temperature monitoring, and the battery management system itself tracking voltage, current and cell temperature. No single method is relied on alone.
Why must damaged cells be isolated for so long after a fire?
A cell that has been through a thermal event can retain enough stored energy and internal damage to re-enter runaway hours or days later. Holding affected cells in an isolated area with continuous thermal and gas monitoring prevents a second event inside the plant, which is why re-entry is governed by measurements rather than by elapsed time alone.
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Download MEP Calc on the App StoreFM Global Property Loss Prevention Data Sheet DS 7-112 (Lithium-Ion Battery Manufacturing and Storage); NFPA 855, Standard for the Installation of Stationary Energy Storage Systems.