An Ultrathin, Flexible Solid Electrolyte with High Ionic Conductivity Enhanced by a Mutual Promotion Mechanism
Yingjie Gao, Zhuang Sun, Chenghao Cui, Haoran Wang, Wenzheng Cao, Zhiqian Hou, Deming Zhu, Yanan Yang, Tao Zhang
Abstract
The pursuit of strong endurance and nonflammable performances has promoted demand for solid-state batteries (SSBs). Meanwhile, the reduction of electrolytes’ thickness is the key to improving battery performance. However, a large-scale feasible method to fabricate an ultrathin solid electrolyte exhibiting high ionic conductivities is still a challenge. Here, we show a large-scale feasible method to prepare a succinonitrile/polyacrylonitrile(SN/PAN)-coated Li6.4La3Zr1.4Ta0.6O12 (LLZTO) with flexibility and high ionic conductivity by tape-casting. The unique dual polymer-coated garnet electrolytes exhibit structural stability through mutual promotion, constructing soft interparticle contact that provides fast lithium-ion transfer channels. In essence, the mutual promotion mechanism is that SN can improve the Li+ conductivity of PAN, while PAN can protect SN from aggregation. Therefore, the flexible SN/PAN-coated LLZTO provides high structural stability and satisfactory electrochemical performance, contributing to a high ionic conductivity of 4 × 10–4 S cm–1 at room temperature (RT). In this way, a long lifespan of over 500 cycles and a high discharge capacity (163 mAh g–1) are achieved based on LiFePO4 (LFP) cathodes at 0.2 C.