Flexible Organic–Inorganic Composite Solid Electrolyte with Asymmetric Structure for Room Temperature Solid-State Li-Ion Batteries

Solid state electrolytes have stimulated research interest due to their promising application in lithium batteries with high safety. In this paper, an asymmetrical structure composite solid electrolyte consisting of Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), poly­(vinylidene fluoride–hexafluoropropylene) (P­(VDF-HFP)), succinonitrile (SN), and a polyimide (PI) film (named ACSE-PI) was fabricated successfully. This solid electrolyte is flexible and can be stable at a high temperature of 150 °C. Moreover, it exhibits a wide electrochemical window of 5 V and high ionic conductivity of over 10^–4 S cm^–1. An all-solid-state battery assembled with this electrolyte exhibits excellent performance at ambient temperature. In particular, the specific discharge capacity of LiFePO₄/ACSE-PI/Li battery is 168.4, 164.4, 154.9, 143.4, 129.5, and 109.4 mAh g^–1 at a rate of 0.1, 0.2, 0.5, 1, 2, and 5 C, respectively. It also delivers a reversible discharge capacity of 156 mAh g^–1 after 200 cycles at 0.2 C. Notably, the battery can also operate at 4 °C, and the discharge capacity is higher than 110 mAh g^–1 after 200 cycles at 0.2 C. Considering the good performances mentioned above, the ACSE-PI electrolyte is appropriate for the practical application of a solid-state Li-ion battery with higher safety.