Two-step strategy to optimize interfacial compatibility of polyether sulfone-Li6.75La3Zr1.75Ta0.25O12 composite polymer electrolytes with Li anode for solid lithium battery with a wide working temperature range

Although composite polymer electrolytes (CPEs) are currently regarded as one of the most promising solid electrolyte systems closing to commercial application, some basic problems, including low conductivity at low temperature, serious interfacial compatibility with Li metal anode, inhibit the development of CPEs for solid state lithium batteries (SSLBs). Herein, a “polymer-in-ceramic” CPEs consisting of polyether sulfone (PESF), Li6·75La3Zr1·75Ta0·25O12 (LLZTO) and bis(trifluoromethane) sulfonimide lithium salt (LiTFSI) is reported, and a two-step strategy is proposed to optimize its conductivity and interfacial compatibility with Li metal anode. Benefitting from both the continuous porous structure to provide additional Li+ conducting pathways on internal porous interfaces and the typical heterogeneous bilayer structure to enhance compatibility with Li metal anode, the optimized CPEs delivers promising Li+ conductivities in a wide operating temperature range (>2.0 × 10−4 S cm−1 at −10 °C, >1.4 × 10−3 S cm−1 at 60 °C), improved tolerance against Li dendrites and/or pulverization. Moreover, commercial LiFePO4 cathode based SSLBs show acceptable discharge specific capacities of >160 mA h g−1 and excellent cycling stabilities of over 200 cycles at both room temperature and 60 °C at 0.2C.