Ultrathin poly(cyclocarbonate-ether)-based composite electrolyte reinforced with high-strength functional skeleton

Composite polymer electrolytes (CPEs) are considered to be the most promising to break through the performance and safety limitations of traditional lithium-ion batteries because of their excellent electrochemical and mechanical properties. Aiming at the performance limitations of the most common polyether matrix such as poly(ethylene oxide) (PEO), a novel poly(cyclocarbonate-ether) polymer matrix was prepared by in-situ thermal curing, the weaker interaction between its C = O bond and Li+ can promote the rapid transport of Li+. Adding ionic liquid and active filler LLZTO to the matrix can synergistically reduce the crystallinity of matrix and promote the dissociation of lithium salts. In addition, a 3D functional skeleton made of polyacrylonitrile (PAN) and lithium fluoride (LiF) can greatly improve the mechanical strength of polymer matrix after cold pressing, and LiF is also conducive to interface stability. The thickness of the optimal sample (VP6L/CPL) was only 25 μm, and its ionic conductivity, lithium ion transference number, and electrochemical stability window were as high as 7.17 × 10−4 S cm−1 (25 °C), 0.54 and 5.4 V, respectively, while the mechanical strength reaches 6.1 MPa, which can fully inhibit the growth of lithium dendrites. The excellent electrochemical performance and mechanical strength enable the assembled Li|VP6L/CPL|Li battery to be continuously charged for over 200 h and cycled stably for more than 2300 h, and Li|VP6L/CPL|LFP battery can be stably cycled for more than 400 and 550 cycles at 1 C (40 °C) and 0.5 C (25 °C), respectively.