A borate-rich, cross-linked gel polymer electrolyte with near-single ion conduction for lithium metal batteries

Lithium metal batteries (LMBs) show tremendous potential in energy storage due to ultrahigh energy densities. Nevertheless, maintaining a stable solid electrolyte interphase (SEI) and suppressing the growth of dendrites are hard to achieve with conventional liquid electrolytes. Gel/solid polymer electrolytes are sought-after candidates to block dendrite growth, while they still suffer from poor ionic conductivity and an incompatible interphase. Herein, a borate-rich gel polymer electrolyte with a 3D cross-linked structure (3D-BGPE) is designed to settle these problems. By incorporating anion-trapping boron moieties into a 3D configuration via an in situ strategy, the 3D-BGPE presents high ionic conductivity (8.4 × 10−4 S cm−1), near single ion conduction (Li+ transference number of 0.76) and constructs a stable and conductive SEI layer on the lithium anode. Accordingly, the LMBs employing the 3D-BGPE can effectively inhibit the dendrite growth and maintain 89.73% capacity retention after 400 cycles. A promising approach to design highly effective electrolytes for safe and long-life LMBs is provided in this work.