All-Solid-State Batteries Batteries With Sulfide-Based Solid Electrolyte

All-solid-state lithium-ion batteries have become research hotsport because of series of advantages, such as high security, long cycle life, high charge-discharge efficiency, high temperature performance, easy to assemble large-scale, and have a broad application prospects.However, all-solid batteries using no organic electrolyte solutions have the following problems: first, the lithium sulfide material must has high purity, so the manufacturing process is complicated and expensive; Secondly, the preparation process of sulfur-based solid electrolyte Li2S-P2S5 shoud be optimized, the lithium ion conductivity need to be improved through reducing the interface impedance, the compatibility between cathode material and anode material is poor, and even result in the occurrence of side effects, which reduce the energy density of the solid-state lithium-ion battery; Thirdly, there is a large interfacial resistance between cathode material and solid electrolyte, and the presence of mutual diffusion of elements during the reaction will destroy the structure of solid electrolyte and cathode material, decreasing the charge-discharge efficiency and cycle stability.This paper aims to prepare high purity lithium sulfide by co-precipitation, and using high energy mechanical milling to prepare 70Li2S-30P2S5 with higher lithium ion conductivity, meanwhile, to improve the electrochemical performance of all-solid-state cells using Li Co O2, a nano-sized coating is employed to modify the surface of Li Co O2 via a sol–gel process. Finally, X-ray diffraction, UV, IR, Differential scanning calorimetry, impedance spectroscopy, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and constant current charge-discharge test methods were used to characterize the properties of all the products.The results showed that:(1) the process of preparing lithium sulfide vis co-precipitation primarily through the reaction S8→S82-→S62-→S42-→S32-→S22-→S2-without other side reaction, and obtained a higher purity lithium sulfide by centrifugal washing and high temperature heat treatment at 300 ℃,(2) the 70Li2S-30P2S5 glass was obtained by high-energy mechanical milling after 60 hours, a glass–ceramic electrolyte with high ionic conductivity was prepared by crystallizing the glass at 280 ℃ for 2 hours.(3) the surface of lithium cobalt oxide was coated with Nb2O5, Ti O2, Zr O2 by the sol-gel method, coating amount was about 5 wt%. Surface Coating significantly improved the discharge capacity and discharge voltage platform of solid-state battery, at room temperature, the maximum discharge capacity up to 112.7 m Ah/g, capacity retention rate was 75.6 % after after 10 laps cycle, furthermore, the maximum discharge capacity up to 138 m Ah/g under 100 ℃, and the capacity retention rate was 91.3 % after 30 laps cycle. Which were significantly higher than pure lithium cobalt oxide.