Enabling high-capacity Li metal battery with PVDF sandwiched type polymer electrolyte

Abstract

Polyvinylidene difluoride (PVDF) is one of the most attractive electrolyte materials for solid-state batteries due to its high ionic conductivity, however, the battery performance is limited by the high electrolyte–electrode interfacial resistance. Herein, PVDF polymer mixed with ceramic Li7La3Zr2O12 is coated on cellulose support membrane (PLCSM) through a simple slurry-casting method. The ionic transport of PLCSM is originated from dimethyl formamide (DMF)-Li+ solvation structure, which plays a critical role in conducting lithium ions. β-PVDF after dehydrofluorination offers a high dielectric constant and enhances the dissociation of lithium salt. As a result, PLCSM with a total thickness of 85 µm presents an oxidation voltage of 4.9 V. Li-Li symmetric cells by employing PLCSM reveal that the critical current density (CCD) is increased to 1 mA cm−2. A full cell of LiFePO4 |PLCSM |Li with high mass loading (1.2 mA h cm−2) shows a first-cycle discharge capacity of 160 mA h g−1. With LiNi0.6Mn0.2Co0.2O2 as the cathode, the initial discharge capacity is 153 mA h g−1, and the capacity retention after 80 cycles is 80 %. The sandwiched PLCSM provides an effective strategy to achieve high-performance dendrite-free Li metal batteries.