Click chemistry-initiated highly uniform semi-interpenetrating polymer electrolyte with dual salts for high-performance lithium metal batteries

Solid-state lithium metal batteries built with polymer electrolytes are attractive owing to their high energy density, easy manufacturing, and high safety. However, polymer electrolytes' low ionic conductivity and poor interfacial stability seriously restrict their practical application. Herein, we designed a highly uniform semi-interpenetrating polymer network electrolyte (SIPE) based on thiol–ene click chemistry. This SIPE embedded with linear poly(ethylene glycol) dimethyl (PEGDME) short chains achieves good ionic conductivity (1.78 × 10−4 S cm−1 at 30 °C), low activation energy (0.21 eV), and high lithium-ion transference number (0.53). The thiol–ene click reaction-initiated network effectively promotes homogenous distribution of PEGDME nanodomain in polymer matrix. Therefore, short PEG chains can activate the segmental motion of polymer matrix, provide strong Li+-coordination for fast diffusion, and thus facilitate the dissociation of more lithium salts. We demonstrate a dual-salt of LiTFSI and LiDFOB salt in SIPE (D-SIPE), which contributes to a rigid and stable LiF-rich solid electrolyte interphase towards electrodes. The D-SIPE-based cell achieves improved specific capacity and cyclability when tested in solid-state Li metal batteries with LiFePO4 cathode. This work provides a strategy for rationally designing polymer electrolytes and broadening the application of click chemistry in solid-state lithium metal batteries.