One‐Step Polymerizations Enable Facile Construction and Structural Optimization of Graft Copolymer Electrolytes

The development of poly(ethylene oxide) (PEO)‐based solid polymer electrolytes (SPEs) is limited by the semi‐crystalline nature of PEO and the extremely strong EO‐Li+ interactions. To promote the rapid migration of Li+, a one‐step method combining radical polymerization and ring‐opening polymerization catalyzed simultaneously by lithium carboxylate is proposed to construct multi‐component graft copolymer electrolytes (GCPEs) in this study. Tailored macroinitiator with catalytic and initiated sites (PAALi(OH‐Br)) realizes one‐step polymerizations of vinyl monomers and cyclic monomers, and provides GCPEs with poly(ethylene glycol) (PEG) and poly(ε‐caprolactone) (PCL) side chains. The grafted structure of GCPE greatly facilitates the intra‐chain hopping of Li+, resulting in excellent ionic conductivity. The introduction of PCL further improves the tLi+ of GCPE. The three‐component graft copolymer electrolyte constructed by polystyrene (PS), PEO, and PCL exhibits high tensile stress (1.62 MPa), a high ionic conductivity (2.4 × 10−5 S cm−1, 30 °C), and a high tLi+ of 0.47 and high electrochemical stability. Graft copolymer electrolytes (GCPEs) are achieved in one‐step by combining lithium salt‐catalyzed orthogonal polymerizations (radical polymerization and ring‐opening polymerization). The resulting GCPEs show good thermal stability, high room‐temperature ionic conductivity, improved lithium‐ion transference number, and outstanding electrochemical stability window.