Cellulose-Br-initiated imidazolium cation and ether linkage regulation of all-solid-state polymer electrolyte for advanced lithium transfer and battery performance

The all-solid-state polymer electrolyte (SPE) with superior electrochemical performance and stability is the most significant part for the development of high safety and reliable batteries. In this work, the ether linkage and imidazolium ionic liquid are incorporated into the modified macromolecular cellulose network via atom transfer radical polymerization for the construction of brush-like cellulose bromide-poly(ethylene glycol) methyl ether methacrylate@1-vinylimidazole ionic liquid (CB-PEGMA@IL) and cellulose bromide-1-vinylimidazole ionic liquid@poly(ethylene glycol) methyl ether methacrylate (CB-IL@PEGMA) composite polymers. The crystallinity of pristine CB is largely decreased on account of the synergistic effect of ionic liquids and ether linkage. In particular, CB-PEGMA@IL presents a lower crystallinity and superior electrochemical performances than that of the CB-IL@PEGMA. With a wide electrochemical stability window (5.3 V vs Li/Li+), the CB-PEGMA@IL based SPE presents a high ionic conductivity (1.2 × 10−4 S cm−1) and record Li+ transference number (0.32). LiFePO4/Li battery assembled with CB-PEGMA@IL-SPE shows excellent cycling performance (beyond 150 cycles at 0.2 C) and good rate capacity. Moreover, the overpotential of CB-PEGMA@IL-SPE based symmetric battery can keep ∼0.03 V even after 200 h cycling (100 μA cm−2). The soft-packed battery based on CB-PEGMA@IL-SPE can withstand bending and present stable voltage output upon folding at various angles. This rigid-flexible hybrid SPE provides a unique candidate for the fabrication of wearable high-tech electronic devices.