Multilayer structure solid-state electrolyte composite membranes for long-life quasi-solid-state battery

To reduce the impedance of the interface between solid electrolytes and electrodes and improve the interfacial stability, the liquid electrolyte (LE) is added between solid-state electrolytes and electrodes. We design LE containing different lithium salts, additives and a solid-state electrolyte membrane containing polyvinylidene fluoride (PVDF), Li1.3Al0.3Ti1.7(PO4)3 (LATP) and polypropylene membrane (PP) (LATP membrane), and systematically investigate the interfacial wettability, stability and safety through contact angle analysis, interfacial impedance measurements, and linear scanning voltammetry. The results show that the LE containing 1 M lithium hexafluorophosphate (LiPF6) salt, 1.3-propane sultone (1.3-PS) additive, adiponitrile, fluoroethylene carbonate (FEC), and that containing 0.575 M lithium bis(trifluoromethane sulfonimide) (LiTFSI)/0.575 M LiPF6 salt, trimethyl phosphate, FEC, and PS exhibit superior performance. The interfacial impedance of the Li|LE-LATP membrane-LE|Li coin cell is only ∼50 Ω. The LiNi0.6Co0.2Mn0.2O2 (NCM622)|LE-LATP membrane-LE|Si/C coin cell exhibits an initial specific discharge capacity of ∼163 mAh g−1 at 0.5 C and 25 °C, and the capacity retention rate is ∼87% after 100 cycles. Furthermore, the 5 Ah NCM622|LE–LATP membrane–LE|Si/C pouch battery exhibits a capacity retention rate of> 90% after 400 cycles at 25 °C and 1 C.