Cell-to-Cell Thermal Propagation
Cell-to-cell thermal propagation is the spread of a battery failure when energy released by one cell causes one or more neighbouring cells to enter thermal runaway.
How propagation occurs
Propagation can transfer through direct heat conduction, flames, hot gases, or ejected material. Pack-level measures such as cell spacing, thermal barriers, cooling structures, controlled venting, and electrical protection aim to delay or prevent that transfer.
The term does not describe the initiating failure inside the first cell. A cell can enter Thermal Runaway without the event propagating, and a single-cell event does not by itself mean that an entire battery pack will burn. Test results therefore need to distinguish initiation, propagation between cells, and consequences at module or pack level.
For the broader failure sequence and protection layers, see EV Battery Safety and Failure Management.