Self-crosslinking polymer electrolyte based on single-ion for high-performance lithium metal batteries

Poly (ethylene oxide) based polymer electrolytes have garnered significant attention because of their high lithium-ion transference number and favorable flexibility in lithium metal batteries. However, their developments are constrained by low ionic conductivity, poor interfacial stability and inadequate mechanical strength. Here, we synthesized fluorine-containing single-ion polymer electrolytes with enhanced conductivity and interfacial compatibility using the reversible addition-fragmentation chain transfer polymerization method, incorporating strong electron-withdrawing groups. The PF₃V₇₅₀-4% electrolytes show the high ionic conductivity of 2.04 × 10⁻⁵ S cm⁻¹ at room temperature, outperforming other PFV₇₅₀-4% and PF₃OV₇₅₀-4% with conductivities of 1.54 × 10⁻⁵ and 1.89 × 10⁻⁵ S cm⁻¹. Density-functional theory calculations indicated that the anionic groups in the monomer containing –CF₃ group require the least energy (640.1 kJ mol⁻¹) to dissociate from lithium ions, compared to 668.58 kJ mol⁻¹ for its fluorine-free counterpart. This suggests that the introduction of the strong electron-absorbing group increases the release of lithium ions from the anionic group, thereby reducing the interaction strength facilitating lithium-ion transport. Moreover, cells constructed with LFP|PF₃V₇₅₀-4%|Li exhibited excellent discharge specific capacities of 158.7 mAh·g⁻¹ at 0.2 C, maintaining a remarkable capacity retention rate of 87.9 % after 600 cycles. These findings underscore the potential of fluorine-containing SSPEs to significantly enhance the performance of lithium metal batteries.