Gel Polymer Electrolyte Enhances Safety Of Solid Lithium Battery

- Jul 01, 2019-

Recently, the team of Wen Zhaoyin, a researcher at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, achieved the in-situ preparation of a gel polymer electrolyte with an ion-conducting initiator. The gel polymer electrolyte has excellent fire resistance and solid lithium assembled based on the electrolyte. The battery can still supply power to the LED array while being subjected to shearing and fire conditions (flame temperature of 528 ° C), so that the safety of the lithium battery is greatly improved.

The relevant work applied for Chinese invention patents. The main research results were published in the top international journal Advanced Energy Materials (IF=21.875) under the title of “In Situ Generated Fireproof Gel Polymer Electrolyte with Li6.4Ga0.2La3Zr2O12. As Initiator and Ion-Conductive Filler”. The first author of the thesis is Xu Dong, a doctoral student at Shanghai Silicate, and the instructor is a researcher at Wen Zhaoyin.

Gel polymer electrolyte (GPE) has the advantages of high safety of solid polymer electrolyte (SPE) and high ionic conductivity of liquid electrolyte to some extent, and is considered to be the most suitable electrolyte system at present. At present, more research is on gel polymer electrolyte systems based on polyvinylidene fluoride (PVDF) and its derivatives.

However, the gel electrolyte still contains a certain amount of flammable liquid electrolyte, which poses a safety hazard. In order to further improve their safety performance and electrochemical performance, researchers have done a lot of research work, including organic-organic blending modification, organic-inorganic composite modification, physical/chemical crosslinking modification.

However, most of the literature does not report on the safety performance of gel polymer electrolytes. On the other hand, in the preparation process of a gel polymer electrolyte such as a phase conversion method which is currently used, a large amount of volatile organic solvent is used, which pollutes the environment and increases the cost, and the preparation process is cumbersome. The above problems can be avoided or alleviated by the method prepared by in-situ cross-linking polymerization.

Wen Zhaoyin's team of researchers uses a garnet-type solid electrolyte (Li6.4Ga0.2La3Zr2O12) as an initiator and an ion-conducting filler and a triethyl phosphate/fluorocarbonate in a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). The defluorination and cross-linking process of PVDF-HFP was initiated in a vinyl acetate (TEP/FEC) mixed solution to realize the in-situ preparation of the gel polymer electrolyte, and the mechanism of the gel transformation process was further studied.

The optimized gel polymer electrolyte has an ionic conductivity of 1.83×10-3 S cm-1 at 20 ° C and an electrochemical stability window of 4.75V at room temperature. The gel polymer electrolyte has excellent fire resistance, and the solid lithium battery assembled therefrom has high safety. A ternary lithium battery based on the gel polymer electrolyte exhibits better cycle stability. This work provides new research ideas for obtaining excellent ionic conductivity using a fire-resistant gel electrolyte and ensuring high safety of the gel polymer electrolyte and the corresponding lithium battery.