Weak-Interaction Environment in a Composite Electrolyte Enabling Ultralong-Cycling High-Voltage Solid-State Lithium Batteries
Ke Yang, Jiabin Ma, Yuhang Li, Junyu Jiao, Shizhe Jiao, Xufei An, Guiming Zhong, Likun Chen, Yuyuan Jiang, Yang Liu, Danfeng Zhang, Jinshuo Mi, Jie Biao, Boyu Li, Xing Cheng, Shaoke Guo, Yuetao Ma, Wei Hu, Shichao Wu, Jiaxin Zheng, Ming Liu, Yan‐Bing He, Feiyu Kang
Abstract
Poly(vinylidene fluoride) (PVDF)-based solid electrolytes with a Li salt-polymer-little residual solvent configuration are promising candidates for solid-state batteries. Herein, we clarify the microstructure of PVDF-based composite electrolyte at the atomic level and demonstrate that the Li + -interaction environment determines both interfacial stability and ion-transport capability. The polymer works as a “solid diluent” and the filler realizes a uniform solvent distribution. We propose a universal strategy of constructing a weak-interaction environment by replacing the conventional N, N -dimethylformamide (DMF) solvent with the designed 2,2,2-trifluoroacetamide (TFA). The lower Li + binding energy of TFA forms abundant aggregates to generate inorganic-rich interphases for interfacial compatibility. The weaker interactions of TFA with PVDF and filler achieve high ionic conductivity (7.0 × 10 –4 S cm –1 ) of the electrolyte. The solid-state Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 cells stably cycle 4900 and 3000 times with cutoff voltages of 4.3 and 4.5 V, respectively, as well as deliver superior stability at −20 to 45 °C and a high energy density of 300 Wh kg –1 in pouch cells.