Abstract: Solid state lithium-ion batteries (SLIBs) have been considered as one of the most promising sustainable next-generation technologies for energy storage. However, the poor interfacial compatibility and low ion conductivity of solid electrolytes still remain a major challenge for SLIBs. Herein, a free-standing flexible solid polymer LA-PAM-PEO electrolyte is constructed through the electrospinning technology featuring with high Li⁺ conductivity (6.1 × 10^-4 S cm^-1), strong mechanical strength and high Li⁺ migration number (0.32), which breaks the restriction between ionic conductivity and mechanical strength in polymer solid electrolyte. The cross-linking between LA, PAM and PEO is verified to decrease the crystalline of PEO, thus increasing the Li⁺ conductivity. Moreover, benefiting from the 3D network composed of interconnected nanofibers and the covalent bonds between LA, PAM and PEO, the mechanical strength of LA-PAM-PEO SPE was also effectively improved. The LA-PAM-PEO SPE also delivers a high electrochemical window (4.95 V), and low interface resistance (243.8 Ω). As a result, the Li/Li symmetrical cell with the LA-PAM-PEO displayed outstanding stability after 1000 h with the uniform Li deposition on the interface of Li electrode, in sharp contrast to the PEO SPE. In addition, the Li/LA-PAM-PEO SPE/LFP displays a discharge capacity of 135 mA h g^-1 after 1000 cycles at the rate of 1 C, with a capacity retention of 93.5%. The proposed LA-PAM-PEO SPE thus opens new possibilities for the fabrication and engineering of solid-state Li-ion batteries.

Key words: Solid state battery, Solid electrolyte, PEO, Electrospinning, Li-ion battery