The Interaction of Ternary Components of Ionic Liquid Gel Polymer Electrolytes for Lithium Metal Batteries

Authors

Xiao-na PAN, 1. School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001,Heilongjiang;
Li-lai LIU, 2. School of Environment and Chemical Engineering, Heilongjiang University of Science and Technology, Harbin 150001, Heilongjiang;
Zhi-pu WANG, 1. School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001,Heilongjiang;
Dan WANG, 1. School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001,Heilongjiang;
Yun LI, 1. School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001,Heilongjiang;
Pei-xia YANG, 1. Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China;Follow
Jin-qiu ZHANG, 1. School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001,Heilongjiang;
Mao-zhong AN, 1. School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001,Heilongjiang;

Corresponding Author

Pei-xia YANG(yangpeixia@hit.edu.com)

Abstract

Ionically conductive gel polymer electrolyte is an excellent candidate due to its inflammable, nonvolatile and high thermal stability as compared to commercial liquid electrolytes which are usually flammable, volatile, and containing toxic organic solution as solvent, The synthesis and application of ionic gel polymer electrolytes in lithium ion/metal batteries have been previously reported. However, the interaction effects of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI) ionic liquid (as plasticizer) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on PVDF-HFP polymer remain unclear. In this work, the molecular structure of ionic liquid gel polymer electrolyte (ILGPE) composed of PP13TFSI, LiTFSI and PVDF-HFP was studied by Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR). Meanwhile, X-ray diffraction (XRD) analysis was performed to qualify the crystallization of PVDF-HFP polymer in the ILGPE with or without PP13TFSI or/and LiTFSI to investigate ionic liquid or/and LiTFSI impact on PVDF-HFP polymer. The results showed that PP13TFSI, LiTFSI and PVDF-HFP were physical-blending without chemical reaction, but with molecular coordination with PVDF-HFP polymer chain. In addition, the crystallization of PVDF-HFP could be changed by additions of PP13TFSI and LiTFSI at the same time, and the ionic conductivity could be improved with increasing amorphous phase in polymer matrix. The electrochemical stability window and thermal stability of ILGPE became worse with the N-methyl-2-pyrrolidone (NMP) residue inside the ILGPE. The LiFePO₄/Li battery with the optimized ILGPE (the weight ratio of ionic liquid, LiTFSI, and PVDF-HFP polymer was 3/1/1) showed a good C-rate capability at room temperature. In summary, PP13TFSI and LiTFSI could coordinate with PVDF-HFP polymer chain, and no chemical reaction took place among the three compounds during preparing ILGPE. Furthermore, it is necessary to remove NMP solvent from ILGPE during drying process to improve the electrochemical stability window and thermal stability of ILGPE.

Graphical Abstract

Keywords

ionic liquid gel polymer electrolyte, electrochemical stability, thermal stability

DOI Link

https://doi.org/10.13208/j.electrochem.191120

Publication Date

2020-06-28

Online Available Date

2020-02-14

Revised Date

2020-01-05

Received Date

2019-11-20

Recommended Citation

Xiao-na PAN, Li-lai LIU, Zhi-pu WANG, Dan WANG, Yun LI, Pei-xia YANG, Jin-qiu ZHANG, Mao-zhong AN. The Interaction of Ternary Components of Ionic Liquid Gel Polymer Electrolytes for Lithium Metal Batteries[J]. Journal of Electrochemistry, 2020 , 26(3): 406-412.
DOI: 10.13208/j.electrochem.191120
Available at: https://jelectrochem.xmu.edu.cn/journal/vol26/iss3/3