Single ion conducting polymer as a dual-functional membrane for lithium electrode protection

Abstract

Artificial solid electrolyte interlayer (SEI) with high lithium transference number and enhanced mechanical performance is believed to be highly preferred for high-performance Li metal batteries with required cyclic stability and dendrite suppression. Here we report our finding of a “rigid-flexible” single-ion conducting (SIC) artificial SEI, LPEB, via the “structural self-assembly” strategy, and then present a demonstration of the high performance of such a Li/LPEB membrane anode stacked with Li foil and LPEB. In particular, the homogeneously dispersed charge-delocalized -N(SO₂)₂ anion group makes a rapid Li-ion transport pathway accessible, while the polymer-based microstructure allows sufficiently good mechanical properties of this membrane against Li-dendrite invasion. Subsequently, a largely improved Li-ion battery cell consisting of this modified Li/LPEB anode, LiFePO₄ (LFP) active cathode, and commercial 1 M LiPF₆ electrolyte is assembled. It is shown that this improved cell, called the Li||LFP cell, exhibits the excellent rate capability over a wide C-rate window from 1C to 8C. Very importantly, this Li||LFP cell displays remarkably stable cycling performance at such 8C high rate without formation of visible Li-dendrites. The consequently fabricated symmetrical Li/LPEB|Li/LPEB cell is demonstrated to operate stably at current densities of 1 mA cm^-2 and 2.5 mA cm^-2 respectively for more than 2500 h with absence of Li-dendrites growth.