Abstract:

The application of solid electrolyte instead of flammable liquid electrolyte can effectively solve the safety issues of lithium-ion batteries nowadays.However，the solid-solid contact of electrodes/electrolytes in solid state batteries usually lead to large interfacial impedance，resulting in high polarization.The polyvinylidene difluoride（PVDF） based solid electrolyte was used as cathode and anode interface buffer layer，which effectively solved the problem of high impedance of titanium-aluminum-lithium phosphate solid electrolyte with electrode，reducing the positive interface impedance from 1 716 Ω/cm² to 213 Ω/cm².At the anode interface，PVDF provided a good elastic support，so that the interfacial impedance was reduced from 1 135 Ω/cm² to 109 Ω/cm².In addition，the direct current polarization of lithium symmetric battery showed that the stability of the anode interface was significantly improved after PVDF modification.Finally，the lithium cobalt oxide/lithium pouch battery was assembled.With PVDF modification on both cathode and anode interface，the energy density of the battery reached to 336 W·h/kg.The capacity retention rate was increased from 30.7% to 83.3% after 300 cycles at 1C.

Key words: polyvinylidene fluoride, Li_1.3Al_0.3Ti_1.7（PO₄）₃, all-solid-state, interface, metal lithium