The role of lithium metal electrode thickness on cell safety

Neumann, Jonas; Hellweg, Lukas; Bela, Marlena; Hering, Tobias; Stan, Marian; Winter, Martin; Nowak, Sascha; Börner, Markus

Abstract

As rechargeable lithium metal batteries evolve toward commercialization, delivering increased energy and power densities, safety considerations become inevitable. This study combines detailed thermal analysis and imaging techniques to reveal the influence of the lithium metal reservoir and deposition morphology on the safety properties of lithium metal batteries and zero-excess lithium metal batteries. Thermal abuse experimentation confirmed metallic lithium as the most safety-relevant cell component and demonstrated an anode-driven thermal runaway of cyclic-aged lithium metal batteries at 80°C–90°C. Beyond that, increasing lithium metal excess showed enhanced self-heating rates after the lithium melting temperature. Beyond that, lithium deposition morphology had the most detrimental effect on thermal stability, and the formation of high-surface-area lithium was found to be the key driver of thermal failure. These findings provide important insights into the safety characteristics of lithium metal batteries and support the development of safe and commercially successful batteries in the future.