In-situ measurement of internal gas pressure within cylindrical lithium-ion cells

Internal gas pressure is a key parameter that varies depending on cell heating and gas formation over the lifetime of a lithium-ion cell under dynamic load conditions and ageing. In our research, for the first time, we present a methodology to directly measure internal gas pressure during pre-instrumentation, cell operation and ageing via an embedded sensor system. Cylindrical format cells (LG-INR21700M50) are instrumented using our proven instrumentation technique. Our study demonstrates that the performance and degradation of instrumented cells are not adversely affected by the instrumentation process. In this study, the effect of state-of-charge (SOC), degradation and temperature on internal gas pressure is evaluated. Initial results highlight a nonlinear relationship between gas pressure and SOC of the cells during charging and discharging and, gas pressure and temperature when the cells are operated under no-load conditions. Our study further highlights that gas pressure accumulation can be correlated with capacity fade or state-of-health (SOH). Monitoring of internal gas pressure could therefore become a useful additional indicator of SOC and SOH and provide new insights into degradation and the safety of lithium-ion cells.