Homogeneous polymer-ionic solvate electrolyte with weak dipole-dipole interaction enabling long cycling pouch lithium metal battery
Likun Chen, Tian Gu, Jinshuo Mi, Yuhang Li, Ke Yang, Jiabin Ma, Xufei An, Yuyuan Jiang, Danfeng Zhang, Xing Cheng, Shaoke Guo, Zhuo Han, Tingzheng Hou, Yidan Cao, Ming Liu, Wei Lv, Yan‐Bing He, Feiyu Kang
Abstract
Solid polymer electrolytes (SPEs) are considered as promising electrolytes for high-voltage lithium metal batteries. Whereas, the strong dipole-dipole interaction in polymer electrolytes limits the enhancement of the ionic conductivity. Here, we propose the 1,1,2,2-Tetrafluoroethyl-2,2,3,3-Tetrafluoropropylether (TTE) diluent to significantly regulate the dipole-dipole interaction in polymer-ionic solvate electrolytes (TPISEs). The TTE encapsulates ionic solvate to reduce the dipole-dipole interaction of ionic solvate with the polymer matrix, which promotes their homogeneous distribution, creating a continuous ion percolating network among the polymer matrix. The ion conductivity of TPISEs is therefore enhanced to 1.27×10−3 S cm−1 at 25 °C. Meanwhile, the TTE induces the ionic solvate to transform from contact ion pairs to aggregates, contributing to a stable lithium/electrolyte interface with exchange current density 190 times larger than that without TTE. The Li||LiNi0.8Co0.1Mn0.1O2 full cells exhibit good cycling stability from −30 °C to 60 °C. The practical pouch cells consisting of a thin Li metal foil (50 μm) and a high-areal-capacity positive electrode (3.58 mAh cm−2) achieve a high specific energy of 354.4 Wh·kg−1 and maintain 78.1% capacity after 450 cycles at 54 mA g−1 and 25 °C. This work provides a design strategy for SPEs beyond the bottleneck of ionic conductivity for practical solid-state batteries. Solid polymer electrolytes suffer from limited ionic conductivity and poor interfacial stability for lithium batteries. Here, authors propose a fluorinated ether diluent to reduce the dipole-dipole interaction of ionic solvate with the polymer matrix and induce the formation of aggregates.