A novel thioctic acid-functionalized hybrid network for solid-state batteries

The development of solid electrolytes for solid-state metal batteries is challenging and limited due to low ionic conductivity, poor interface stability, and accompanying side reactions. Herein, a novel thioctic acid-functionalized solid electrolyte based on hybrid heterogeneous 3D cross-linked network covalently tethering thioctic acid is designed and synthesized. Thioctic acid makes soft PEGDA polymerized in hard P(VDF-HFP) matrix to form tough hybrid heterogeneous 3D cross-linked network without initiator, which simultaneously enhances the ion transport and regulates the lithium deposition on the lithium metal surface. Moreover, the C-S bonds formed by polymerization can increase the migration rate of Li+, and this initiator-free polymerization process eliminates residual free radical side reactions and by-products, effectively improving the compatibility of the solid electrolyte with lithium anode. Due to the rational design, the thiotic acid-functionalized hybrid network electrolyte exhibits high ionic conductivity of 0.11 mS cm−1 at ambient temperature. The symmetrical Li//Li cells enable over 1800 h cycling, and the LiFePO4//Li full solid-state batteries deliver high capacity retention (>80%) over 300 cycles at 0.5 C at 25 °C. This work demonstrates a rational design of thicotic acid-functionalized hybrid network with greatly improved ionic conductivity and stability for high performance solid-state batteries.