Research on technology for improving battery safety performance using solid electrolytes

　　The solid electrolyte film can confine soluble polysulfides in the cathode chamber, effectively suppressing the shuttle effect, thus improving the cycle stability and Coulombic efficiency of the lithium-sulfur battery system. The solid electrolyte can not only be used to isolate polysulfide ions in the positive electrode area of lithium-sulfur batteries, but also protect the metallic lithium in the negative electrode, thereby improving the safety of the battery.

　　【introduction】

　　Lithium-sulfur batteries have received widespread attention from researchers due to their high theoretical energy density. The introduction of solid electrolytes into lithium-sulfur battery systems can not only suppress the shuttle effect of polysulfides and the resulting decrease in Coulombic efficiency and capacity fading, but also solve potential safety hazards caused by lithium dendrites formed during cycle charge and discharge. To improve the cycle stability of lithium-sulfur batteries, it is necessary to develop solid electrolyte materials with both high ion selectivity and high lithium ion conductivity based on a deep understanding of the formation mechanism and conduction mechanism of solid electrolytes.

　　【Achievements Introduction】

　　Recently, Professor Li Ju and Assistant Professor Akihiro Kushima of the Massachusetts Institute of Technology, Professor Zhang Xiaogang (co-corresponding author) and Dr. Xu Guiyin (first author) of Nanjing Special Space University used ether-based electrolytes (DOL) commonly used in lithium-sulfur batteries. /DME) solution, use nitric acid acidified carbon nanotube paper (hereinafter, CNTP and ACNTP represent the carbon nanotube paper before and after acidification treatment respectively) to induce cationic in-situ polymerization of 1,3-dioxolane (DOL). A flexible, self-healing solid electrolyte film was generated in situ on the surface of ACNTP. This solid electrolyte film is highly ion-selective and can seal soluble polysulfides in the cathode chamber but allows bidirectional passage of lithium ions, effectively suppressing the shuttle effect and improving the cycle life of lithium-sulfur batteries. It uses metallic lithium as the negative electrode, sulfur-loaded activated carbon (AC/S) as the positive electrode, uses commonly used ether-based electrolyte solution (DOL/DME), and uses a PP/ACNTP/PP (PP is polypropylene) sandwich structure as the separator. The button battery showed good cycle stability in electrochemical tests: when the charge and discharge rate was 1C (1675mA/g), its initial specific capacity was 683mAh/g, and it still maintained a certain capacity after 400 cycles of charge and discharge. Discharge specific capacity of 454mAh/g. The Coulombic efficiency of this lithium-sulfur battery is as high as 99%, and the average capacity decay associated with each cycle is only 0.1%.

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