A “shuttle-relay” lithium metal battery enabled by heteroatom-based gel polymer electrolyte

Abstract

Employing high-energy electrode couples and releasing the capacity of anions in the electrolyte are promising avenues to increase the energy density of existing lithium (Li)-based batteries. Herein, we develop a “shuttle-relay” Li metal battery (SRLMB) based on a hybrid Li-rich oxide cathode with graphite as conductive agent and a heteroatom-based gel polymer electrolyte (HGPE). The HGPE was facilely prepared by polymerizing diethyl allyl phosphate (DAP) monomer in-situ in an all-fluorinated electrolyte, which features high ionic conductivity, high oxidation stability up to 5.5 V vs. Li/Li+, high safety, and superior compatibility with Li metal (a plating/striping Coulombic efficiency of 99.7 %). When applied to SRLMBs, this quasi-solid-state electrolyte enables a reversible insertion of hexafluorophosphate (PF6−) anions into the conductive graphite after the stripping of Li ions from Li-rich oxide, thus improving the overall energy density of batteries. Our findings provide new insights into the upgrading of Li-based battery technology.