Chemical Crossover Accelerates Degradation of Lithium Electrode in High Energy Density Rechargeable Lithium–Oxygen Batteries

摘要

Lithium-oxygen batteries (LOBs) are promising next-generation rechargeablebattery candidates due to theoretical energy densities that exceed those ofconventional lithium-ion batteries. Although LOB with high cell level energydensity has been demonstrated under lean electrolyte and high areal capacityconditions, their cycle life is still poor, and the cell degradation mechanismremains unclear. In the present study, by use of a three-electrode electrochemicalsetup and in situ MS analytical techniques, it is revealed that the reactionefficiency of the negative lithium electrode largely decreases due to chemicalcrossover from the positive oxygen electrode side, such as H_2O and CO_2.Based on this mechanistic understanding, a LOB with an ultra-lightweightflexible ceramic-based solid-state separator with 6 μm thickness that effectivelyprotects the lithium electrode against chemical crossover withoutdiminishing the energy density of LOBs is fabricated. Notably, a 400 Wh kg~(?1)class LOB exhibits a stable discharge/charged process for >20 cycles. Thestrategy demonstrated in this study sheds light on the direction for the practicalimplementation of LOBs with high energy densities and long cycle lives.