Key Advances of High-voltage Solid-state Lithium Metal Batteries Based on Poly(ethylene oxide) Polymer Electrolytes

Abstract

Traditional lithium-ion batteries employing carbonate-based liquid electrolytes might suffer from safety hazards such as leakage, combustion and explosion under abused conditions. In comparison, poly(ethylene oxide) (PEO) based solid-state polymer electrolytes can significantly enhance the safety performance of lithium batteries owing to their intrinsic safety. In addition, PEO can also be made into specific shapes to meet the harsh requirements of special fields owing of their excellent plasticity. More importantly, PEO-based solid-state polymer electrolytes possess superior interfacial compatibility with lithium metal anodes, endowing PEO a very promising solid polymer electrolyte (SPE) for solid-state lithium metal batteries. However, the low electrochemical oxidation potential of PEO-based solid polymer electrolytes makes them challenge to accommodate high-voltage cathodes (≥4 V), which greatly limits the energy density of solid-state polymer lithium metal batteries. Recently, through the unremitting efforts of researchers, PEO based solid-state polymer electrolytes have made a series of significant scientific progress in the field of high-voltage solid-state lithium metal batteries. Herein, this review presents an overview on the scientific challenges, fundamental mechanisms, and design strategies for high-voltage solid-state lithium batteries based on poly(ethylene oxide) all-solid-state polymer electrolytes: (1) constructing a ultra-thin layer on high-voltage cathodes, (2) surface coating of high-voltage cathode particles, (3) surface coating of carbon black, (4) employing carboxyl-rich polymer binders, (5) the design of asymmetric SPE architecture, (6) in-situ formation of high-concentration polymeric interlayer, (7) the introduction of -OCH3 group into PEO, (8) (oxalato)borate salts as additive. At the end of this review, the potential challenges and development trend of PEO-based solid-state polymer electrolytes in high-voltage lithium metal batteries are also elaborated.