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

In this work, hyperbranched polycarbonate-poly(ethylene oxide) (PEO)-based solid polymer electrolytes (HBPC-SEs) are successfully synthesized via a straightforward organo-catalyzed “A 1 ”+“B 2 ”-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 LiFePO 4 /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.