Fatigue of Li metal anode in solid-state batteries.

Solid-state lithium metal batteries (SSBs) are promising for electric vehicles because of their potential to provide high energy density and enhanced safety. However, these batteries face short-circuit challenges caused by uncontrolled lithium dendrite growth during cycling. Using operando scanning electron microscopy and phase-field simulations, we determined that failure of SSBs is closely linked to the fatigue of the lithium metal anode, which markedly contributes to interface degradation and dendrite growth in SSBs. This fatigue follows the Coffin-Manson equation in mechanics, indicating that it is an innate characteristic. Clarifying the essential role of fatigue provides a physical basis for understanding failures of SSBs and paves the way to extending their lifespan. Editor's summary: Lithium dendrite formation and porosity effects caused by high current density are known reasons for the failure of lithium metal batteries. However, there is an open question of why failure can occur at a current density much lower than the critical current density upon cycling. Wang et al. propose that mechanical fatigue of the lithium metal is the primary cause of cycle degradation (see the Perspective by Nanda and Kalnaus). Using in operando scanning electron microscopy, they showed that reversible plating and stripping of lithium generates cyclic stresses, even at low current densities, and these stresses lead to defects, microcracks, and microvoids that cause interface degradation. In conjunction with simulation, the authors showed that they could determine the cycle life of solid-state batteries as a function of current density. —Marc S. Lavine [ABSTRACT FROM AUTHOR]