The synergy mechanism of CsSnI3 and LiTFSI enhancing the electrochemical performance of PEO-based solid-state batteries

Lithium metal solid-state battery is the first choice of batteries for electromobiles and consumer electronic products because of the specific capacity of 3860 mAh g⁻¹ and high electrochemical potential (−3.04 V) of Li metal. Flexible polymer solid electrolytes have become the optimal solution to produce high energy density lithium batteries with arbitrary size and shape. In this work, we introduce a halide perovskite, CsSnI_3, into the polyethylene oxide/lithium bis-(trifluoromethanesuphone)imide (PEO–LiTFSI) polymer matrix. The CsSnI₃ could form a Li_xSn alloy with Li, leading to homogenization of the electric field and Li⁺-flux at the interface, Sn atom also bonds with the TFSI⁻ anion to provide more dissociated Li⁺. Besides that, the I atom could interact with Li to form an electronic insulation with a strong blocking effect on electron tunneling. As a proof of concept, the synergy mechanism of the PEO–LiTFSI–CsSnI₃ electrolyte improves the stable cycle life of the symmetric battery to more than 500 h, and the Li⁺ conductivity raised to 6.1 × 10⁻⁴S cm⁻¹ at 60°C. The application of the “zwitter ions analog” halide perovskite in PEO–LiTFSI provides a new choice among various methods to improve the electrochemical performance of polymer solid-state batteries.