Mechanistic understanding of the electrochemo-dependent mechanical behaviors of battery anodes

Abstract Safety issues have become one of the most critical bottlenecks for the further wide application of lithium-ion batteries (LIBs) as power sources in electrified vehicles. Specifically, the understanding of the electrochemical integrity of LIBs upon mechanical abuse is in pressing need. To this end, we design and conduct ex-situ experiments on anodes with various state-of-charges (SOCs) to study the coupled electrochemical and mechanical behavior of graphite anode. A multiscale computational model considering the lithium-ion intercalation is established and validated. By exploring the combination of experiments and model computation, we discover that the lithiation process increases the density of the binder material as well as the yield stress such that the anode behaves stiffer with higher SOC. The failure strain decreases as SOC increases, and failure first occurs in the active layer. Such densification of the binder material stems from the elastic and plastic expansion of the active particle and the mechanical property mismatch between the active particles and binder. Results highlight the important role of the binder in the safety behaviors of LIBs upon stress and deepen the understanding of the structure-property relation of the anode materials, facilitating the design for next-generation robust LIBs.