Towards practically accessible high-voltage solid-state lithium batteries: From fundamental understanding to engineering design

High-voltage all-solid-state lithium batteries (HV-ASSLBs) have attracted enormous attention as ideal next-generation energy storage devices with improved safety and higher energy density. Nevertheless, the practical energy density and cycling life of HV-ASSLBs are limited by relatively low operating voltage (typically ≤ 4.3), the unsatisfied electrochemical stability windows (ESWs) of solid-state electrolyte (SSEs), mismatched interface, Li dendrite growth and serious side interfacial reactions, which slow down the step of HV-ASSLBs to practical application. This review aims to potentially provide a guideline for practically accessible HV-ASSLB design from the combination of fundamental and engineering perspectives. The critical challenges in HV-ASSLBs are first introduced as the basis. Afterward, recent progress on extending the ESWs of SSEs, reducing the interfacial side reactions, solving the issue of mismatched interfaces, and Li dendrite are summarized to provide a library of approaches. Following that, advanced characterization techniques and theoretical analysis are systematically reviewed to deeply understand the underlying mechanism and explore new electrode and electrolyte materials. Finally, the relationship among key parameters (eg. operating voltage, anode/cathode materials, areal capacities) and gravimetric/volumetric energy density will be clarified, which points out future directions to achieve high gravimetric/volumetric energy densities of over 350 Wh kg−1/700 W h L−1.