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

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 LiNi_0.6Mn_0.2Co_0.2O₂ 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.