CoNi Alloy Modified Separators for High-Capacity and Long Cycle Lithium–Sulfur Batteries

Abstract

The main challenges faced by lithium sulfur (Li–S) batteries are severe shuttle reactions and the promotion of delayed reaction kinetics within the battery. To address these issues, this study synthesized an alloy material (CoNi). This material has excellent and abundant polysulfide adsorption active sites, thereby improving the reaction kinetics inside the battery. It is worth noting that the unique properties of metal atoms are conducive to suppressing the shuttle effect. Without adding a carbon substrate and using only the CoNi alloy as the separator coating layer, the battery can achieve excellent performance. The battery modified with a CoNi separator exhibited an initial discharge capacity of up to 935 mAh g^–1 in a long 1 C cycle, with small attenuation (0.058%) single cycle after 1000 cycles. Even at a high rate of 2 C, it can remain stable for 350 cycles, with an initial discharge capacity of 821 mAh g^–1 and a single cycle attenuation of 0.098%. Under a high sulfur load (3.65 mg cm^–2) and a current density of 0.1 C, the initial capacity is 1064 mAh g^–1, and the battery remains stable over 30 cycles. In addition, this study directly demonstrated the significant catalytic effect of CoNi material on the internal reactions of batteries through Li₂S nucleation experiments, thereby improving the reaction kinetics. This study provides a new method for promoting the practical application of Li–S batteries and narrows the gap between theoretical and experimental results through long cycles and high sulfur loads.