A quasi-solid-state electrolyte with high ionic conductivity for stable lithium-ion batteries

The practical applications of solid-state electrolytes in lithium-ion batteries (LIBs) are hindered by their low ionic conductivity and high interfacial resistance. Herein, an ethoxylated trimethylolpropane triacrylate based quasi-solid-state electrolyte (ETPTA-QSSE) with a three-dimensional (3D) network is prepared by a one-step in-situ photopolymerization method. The 3D network is designed to overcome the contradiction between the plasticizer-related ionic conductivity and the thickness-dependent mechanical property of quasi-solid-state electrolytes. The ETPTA-QSSE achieves superb room-temperature ionic conductivity up to 4.55×10−3 S cm−1, a high lithium ion transference number of 0.57, along with a wide electrochemical window of 5.3 V (vs. Li+/Li), which outperforms most ever of the reported solid-state electrolytes. Owing to the robust network structure and the cathode-electrolyte integrated electrode design, Li metal symmetrical cells show reduced interface resistance and reinforced electrode/ electrolyte interface stability. When applying the ETPTA-QSSE in LiFePO4∥Li cells, the quasi-solid-state cell demonstrates an enhanced initial discharge capacity (155.5 mAh g−1 at 0.2 C) accompanied by a high average Coulombic efficiency of greater than 99.3%, offering capacity retention of 92% after 200 cycles. Accordingly, this work sheds light on the strategy of enhancing ionic conductivity and reducing interfacial resistance of quasi-solid-state electrolytes, which is promising for high-voltage LIBs.