Facile fabrication of PEG-PPG block copolymer via Michael addition reaction and its successful application as all-solid-state electrolyte for rechargeable lithium metal batteries

Polyethylene glycol (PEG) is one of the most popular polymer matrices for fabricating solid polymer electrolytes (SPEs), and the derived lithium metal batteries (LMBs) exhibit a charming application potential in the field of energy storage and conversion materials. Nevertheless, the semicrystalline nature at ambient temperature of PEG poses significant challenges for its direct utilization in SPEs, thereby impeding its feasibility for commercial application. Herein, a copolymer backbone composed of PEG and polypropylene glycol (PPG) was successfully synthesized via aza-Michael addition reaction, and the SPEs were obtained by introducing stoichiometric content of lithium salt by means of a solution casting process. Benefiting from the doping effect of PPG in the system, the regularity of PEG chain is perturbed, which promotes the room-temperature ionic conductivity of SPEs to 3.62 × 10${}^{-4}$S cm${}^{-1}$, while its electrochemical oxidation potential is as high as 5.73 V. Consequently, the SPEs have a good compatibility with both LiFePO₄ and LiNi${}_{0.8}$Co${}_{0.1}$Mn${}_{0.1}$O₂, and the assembled all-solid-state LMBs demonstrate good cycling performance.