Polycarbonate Copolymer Solid Electrolyte for Stable Cycling of a Li∥LiCoO<sub>2</sub> Cell via In Situ Ultraviolet Irradiation
Yonghao Huang, Zhangyating Xie, Weiya Zhu, Changyong Mo, Weishan Li, Youhao Liao
Abstract
To solve the problems of narrow oxidation decomposition potential and low room temperature ionic conductivity of the traditional poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE), a polycarbonate-based SPE is developed by facile in situ ultraviolet-irradiated polymerization for high-energy-density lithium metal batteries (LMBs). Since the weak complexation between carbonate groups and Li + -ions in the vinyl ethylene carbonate (VEC) section provides the ionic transport capability, while the rigid hydroxyethyl methacrylate (HEMA) segment facilitates the mechanical strengths, the prepared P(VEC-HEMA) copolymer-based SPE exhibits a high ionic conductivity of 0.8 × 10 –3 S cm –1 at room temperature, an antioxidation potential exceeding 5.0 V, and a high Young’s modulus value of 2.3 GPa that can effectively prevent the puncture of lithium dendrites. Notably, the P(VEC-HEMA) copolymer presents a stronger binding energy with TFSI – than that of the PVEC oligomer, ascribed to the hydroxyl group in HEMA section that also gives a fast transport pathway for Li + -ions through hydrogen bonds. Contributed by the advanced functional groups inhered from distinct monomers, the assembled Li∥SPE∥LiCoO 2 full cell using P(VEC-HEMA) electrolyte exhibits excellent rate capacity and long cyclic stability, which shows the specific discharge capacity of 138.1 mA h g –1 at 0.1 C rate in the voltage range of 3.0–4.2 V, maintaining 93.5% of initial capacity after 100 cycles. For comparison, the full cell using PVEC electrolyte has a short circuit after 13 cycles. Therefore, the proposed polycarbonate solid electrolyte gives a bright future to revitalize the development of high-energy-density LMBs.