Aliphatic Hyperbranched Polycarbonates Solid Polymer Electrolytes with High Li‐Ion Transference Number for Lithium Metal Batteries

Abstract

AbstractIn this work, hyperbranched polycarbonate‐poly(ethylene oxide) (PEO)‐based solid polymer electrolytes (HBPC‐SEs) are successfully synthesized via a straightforward organo‐catalyzed “A1”+“B2”‐ring‐opening polymerization approach. The temperature‐dependent ionic conductivity of HBPC‐SEs, composed of different polycarbonate linkages and various LiTFSI concentrations, is investigated. The results demonstrate that HBPC‐SE with an ether‐carbonate alternating structure exhibits superior ionic conductivity, attributed to the solubility of Li salts in the polymer matrix and the mobility of the polymer segments. The HBPC1‐SE with 30 wt% LiTFSI presents the highest ionic conductivities of 2.15  × 10−5, 1.78 × 10−4, and 6.07 × 10−4 Scm−1 at 30, 60, and 80 °C, respectively. Compared to traditional PEO‐based electrolytes, the incorporation of polycarbonate segments significantly enhances the electrochemical stability window (5 V) and Li+ transference number (0.53) of HBPC‐SEs. Furthermore, the LiFePO4/HBPC1‐SE‐3/Li cell exhibits exceptional rate capability and long‐cycling performance, maintaining a discharge capacity of 130 mAh g−1 at 0.5C with a capacity retention of 95% after 300 cycles.