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In-Situ Prepared Fireproof Gel Polymer Electrolyte to Improve the Safety of Lithium Ion Battery

Update time:2019-05-10
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The research team led by Prof. WEN Zhaoyin from the Shanghai Institute of Ceramics, Chinese Academy of Sciences successfully prepared a fireproof gel polymer electrolyte with ion-conductive initiator. The lithium battery assembled with the obtained gel polymer electrolyte could light on the diode array assembled with 82 diodes upon cutting and burning tests (fire temperature is 528?C). The safety property of the lithium battery was remarkably improved. The result was published in Advanced Energy Materials ( IF=21.875, DOI10.1038/s41526-019-0068-1).

To settle the safety problems of the commercial lithium-ion batteries, solid electrolytes based on nonflammable polymers (SPEs) were introduced. However, the low ionic conductivities of SPEs and the related interfacial problems frustrate their applications. Thus, gel polymer electrolytes (GPEs) were proposed to combine the high ionic conductivities of liquid electrolytes with good safety performance of solid polymer electrolytes (SPEs). In this way, GPEs are recognized as one of the most promising electrolytes for practical applications.

Poly vinylidene fluoride (PVDF) and its derivatives are the matrices in GPEs. To improve the electrochemical and safety performance of GPEs, PVDF is investigated in different methods such as organic-organic composite, organic-inorganic composite and physical or chemical crosslinking. However, GPEs are still facing the risks of catching fire. Moreover, the phase reversion and tape-casting methods, which is the common way to prepare GPEs, causes pollution and increases the cost with complex preparation. On the contrary, deleterious organic solvents can avoid the above problems through in-situ method.

Garnet type solid state electrolyte (Li6.4Ga0.2La3Zr2O12) was applied as initiator and ion-conductive filler to form a Lewis base environment, which induced the defluorination and crosslinking of PVDF-HFP chains. Therefore, it realized in-situ preparation of the composite gel polymer electrolyte with high ionic conductivity as well as the further research on the gelation mechanism. The optimal gel polymer electrolyte exhibits an ionic conductivity as high as 1.84×10-3 S cm-1 at 20 ℃ with a high electrochemical window up to 4.75 V at room temperature. Furthermore, lithium batteries assembled with the gel polymer electrolyte possesses superb safety properties upon cutting and burning tests. The batteries demonstrate high discharge retention rate. It shows the great potential of the fire-retardant gel polymer electrolyte to achieve high safety lithium batteries.

The research was funded by National Key R&D Program of China and National Natural Science Foundation of China.

Schematic of the possible composite structure of PLxTF-GPE; Cutting and burning tests of the assembled lithium battery.






Prof. WEN Zhaoyin

Shanghai Institute of Ceramics