Rapid lithium ion transfer of crosslinked electrolyte through the coordination of C-O-C/C=O segments for LiNi_0.8Co_0.15Al_0.05O₂ lithium metal batteries

Given the high combustion or explosion potential of liquid electrolyte, polymer electrolytes have attracted intensive attention due to high safety, compatible interface and flexible processability. However, the related low ionic mobility remains an issue for related wide application. Herein, a crosslinked polymer electrolyte (abbreviated as PMEP) comprising abundant oxygen-contained groups (C-O-C/C=O) is developed. With the crosslinking agent of ethoxylated trimethylolpropane triacrylate (ETPTA), a high transference number (t_Li⁺=0.69) is obtained since C-O/C=O are conducive to the transfer of Li ions. Specifically, C=O group exists in individual monomers in order to be applicable to high voltage cathode, therefore, a criss-cross network containing abundant sites conducive to ion transport is constructed and rapid ion transfer as well as enhanced mechanical strength can be realized even in high potential system. With the coordination effect of C-O and C=O, PMEP exhibits rapid Li ion transfer and a wide electrochemical stability window of 5.1 V. As for Li//Li symmetrical cell, a stable voltage profile with slight polarization of 60 mV is displayed for over 550 h at 1 mA cm⁻². After assembled with LiNi_0.8Co_0.15Al_0.05O₂ cathode, a high discharge specific capacity of 190.6 mAh g⁻¹ is delivered and the capacity retention reaches 86 % at 0.1C for 100 cycles. This work provides a promising method for designing high-performance polymer electrolytes for lithium metal batteries.