Development of cyano-containing polymer electrolyte for solid-state lithium metal batteries operating at high voltage

Abstract

Solid-state polymer electrolytes (SPE) is a promising candidate that substitutes for contemporary liquid electrolyte in Li metal battery (LMB). However, their low oxidation stability generally makes it difficult to operate at high-voltage for enhancing energy density due to the decomposition of electrolytes. To tackle the challenges, cyanoethyl acrylate (CEA) is used to elevate oxidation stability by the electron-withdrawing property of cyano functional group. Furthermore, CEA can inhibit transition metal (TM) dissolution and cathode structure degradation through coordination with TM, which is commonly caused under high-voltage cycling. Herein, CEA and butyl acrylate (BA) are together used with different mol ratio to form a copolymer electrolyte via random co-polymerization for optimal mechanical and electrochemical properties. As a result, the well-tailored B9C1, representing that mole ratio of BA to CEA is 9, shows optimal mechanical/electrochemical properties and high performance under high 4.7V operation in lithium metal battery. This study can give a direction for accomplishing long mileage of polymer electrolyte by achieving durable ultra-high-voltage operation using Ni-rich cathode forward.