Research And Preparation Of Sulfide-Based Solid Electrolyte In All-Solid-State Lithium-ion Batteries

Conventional lithium-ion secondary batteries have been widely used in portable electronic devices and are now developed for large-scale applications in hybrid-type electric vehicles and stationary-type distributed power sources. However, there are some safety issues, such as inflammable, leaky, corrodible and so on, associated with thermal management and combustible organic electrolytes in such battery systems.The more market demand for high-power-type-lithium-ion secondary, the higher of demands for batteries with high energy and power densities and make safety issues increasingly important.All-solid-state lithium batteries are kind of the new high-safety lithium ion battery with solid electrolyte instead of traditional liquid electrolyte. The solid electrolytes consist of solid-state polymer solid-state polymer and inorganic electrolytes and inorganic electrolytes. Inorganic solid electrolytes have widely attention and rapid development because of the higher security. Low ionic conductivity is the main drawback of inorganic solid electrolytes and cannot meet the needs of large current discharge of power battery. So the key point of the industrial application is to improve the ionic conductivity of inorganic solid electrolytes.Sulfide solid electrolytes in the Li₂S-P₂S₅ system are considered one of the best candidate electrolytes for the secondary high-energy solid state batteries, with high ionic conductivity, low electronic conductivity, activation energy and high mechanical strength and so on, and all-solid-state lithium batteries are becoming a hot research topic in the field of chemical power source all over the world.Recent development of inorganic sulfide solid electrolytes and all-solid-state rechargeable lithium batteries with them are reviewed. Sulfide solid electrolytes in the Li₂S-P₂S₅ system were classified and discussed in this paper. And some problems in the application of the battery are also discussed. Binary Li₂S-P₂S₅, ternary95?0.7Li₂S–0.3P₂S₅?–5Li₃PO₄ and quaternary 69Li₂S–26P₂S₅–3P₂O₅–2FeS sulfide glass electrolytes were prepared by a mechanical milling technique in this paper.X-ray diffraction, 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 revealed that the glass electrolytes showedelectrical conductivity up to 10-3S cm-1and the glass electrolytes had a wide electrochemical window up to 5V vs. Li/Li+at 100 ?, it means that the glass electrolytes are stable to lithium.The surface of lithium cobalt oxide was coated with Nb₂O₅, TiO₂, ZrO₂ 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.All-solid-state Li/SE/LiCoO₂ batteries were assembled. The results of charge-discharge test indicated that the highest discharge capacity was 150 mAh g-1, and efficiency can be up 95% after 50 cycles.