The polymer solid electrolyte has a simple preparation method, good film-forming performance, and good electrode-electrolyte interface contact. However, the low room temperature ionic conductivity, poor electrochemical stability, and the inability to match the cathode material with a wide voltage window limit the large-scale commercial application of polymer solid electrolytes; graphene has excellent mechanical, mechanical properties, photoelectric thermal properties and a large specific surface area, high ion conductivity and electron migration number, so it has strong electrical conductivity. In this paper, a typical polymer solid electrolyte polyethylene oxide (PEO) and graphene composite are selected to further enhance the electrochemical performance of the composite material. Experiments have found that the polymer/graphene composite solid electrolyte membrane with graphene added does not decompose significantly before 5 V, which clarifies that it has good electrochemical stability. And the first charge-discharge specific capacity of the composite solid electrolyte membrane is higher than that of the single polymer solid electrolyte membrane. Neither the diffraction peak nor the reduction peak shifted after 5 cycles, and the cycle life was still 99.449% after 100 cycles, indicating that it has good cycle stability. Therefore, the application of polymer/graphene composite solid electrolyte membranes in all-solid-state lithium batteries is feasible.

A quasi-solid-state lithium battery is assembled by plasma sprayed amorphous Li₄Ti₅O₁₂ (LTO) electrode and ceramic/polymer composite electrolyte with a little liquid electrolyte (10 μL/cm²) to provide the outstanding electrochemical stability and better normal interface contact. Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscopy (STEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectrometer (EDS) were used to analyze the structural evolution and performance of plasma sprayed amorphous LTO electrode and ceramic/polymer composite electrolyte before and after electrochemical experiments. By comparing the electrochemical performance of the amorphous LTO electrode and the traditional LTO electrode, the electrochemical behavior of different electrodes is studied. The results show that plasma spraying can prepare an amorphous LTO electrode coating of about 8 μm. After 200 electrochemical cycles, the structure of the electrode evolved, and the inside of the electrode fractured and cracks expanded, because of recrystallization at the interface between the rich fluorine compounds and the amorphous LTO electrode. Similarly, the ceramic/polymer composite electrolyte has undergone structural evolution after 200 test cycles. The electrochemical cycle results show that the cycle stability, capacity retention rate, coulomb efficiency, and internal impedance of amorphous LTO electrode are better than traditional LTO electrode. This innovative and facile quasi-solid-state strategy is aimed to promote the intrinsic safety and stability of working lithium battery, shedding light on the development of next-generation high-performance solid-state lithium batteries.