Boron-containing cross-linker assisted single-ion conducting polymer electrolytes for high-performance and dendrite-free Li-metal batteries

Abstract

Nowadays, single-ion conducting polymer electrolytes for high efficiency, stable, safe and dendrite-free Li-metal batteries are in great need to protect lithium metal anode. In this work, a boron-containing single-ion polymer electrolyte (BSPE), prepared by the copolymerization of allyl diglycol carbonate (ADC), lithium bis((trifluoromethyl)sulfonyl)amide (LiTFSI), and diisopropyl allylboronate (DPAB). The weak coordination interaction between Li⁺ and polar carbonate enhances Li⁺ transport ability. Further, the boron-containing cross-linker fixes the counter anions on the polymer backbones, limiting the movement of the anions and promoting the rapid and uniform Li⁺ transference. The BSPE with 3 wt% DPAB exhibits higher Li⁺ transference number (t₊ = 0.77) and better ionic conductivity (1.36 × 10⁻⁴ S cm⁻¹ at 25 °C) compared with that without DPAB. The wider electrochemical window (5.6 V vs. Li⁺/Li), stable polarization and suppressed lithium dendrites during the plating/stripping cycle at a current density of 0.2 mAcm⁻² for 600 h provide the metal-lithium batteries with better safety and higher efficiency. In addition, the initial discharge capacity of LiFePO₄/BSPE/Li is 140.7 mAh g⁻¹ with 95.2 % coulombic efficiency, and the capacity retention still remains 98.7 % after 200 cycles at 0.1C. The excellent performance endows the BSPE with the potential application in high-performance lithium metal batteries.