CoNi Alloy Modified\nSeparators for High-Capacity and\nLong Cycle Lithium–Sulfur Batteries

The main challenges faced by lithium sulfur (Li–S)\nbatteries\nare severe shuttle reactions and the promotion of delayed reaction\nkinetics within the battery. To address these issues, this study synthesized\nan alloy material (CoNi). This material has excellent and abundant\npolysulfide adsorption active sites, thereby improving the reaction\nkinetics inside the battery. It is worth noting that the unique properties\nof metal atoms are conducive to suppressing the shuttle effect. Without\nadding a carbon substrate and using only the CoNi alloy as the separator\ncoating layer, the battery can achieve excellent performance. The\nbattery modified with a CoNi separator exhibited an initial discharge\ncapacity of up to 935 mAh g<sup>–1</sup> in a long 1 C cycle,\nwith small attenuation (0.058%) single cycle after 1000 cycles. Even\nat a high rate of 2 C, it can remain stable for 350 cycles, with an\ninitial discharge capacity of 821 mAh g<sup>–1</sup> and a\nsingle cycle attenuation of 0.098%. Under a high sulfur load (3.65\nmg cm<sup>–2</sup>) and a current density of 0.1 C, the initial\ncapacity is 1064 mAh g<sup>–1</sup>, and the battery remains\nstable over 30 cycles. In addition, this study directly demonstrated\nthe significant catalytic effect of CoNi material on the internal\nreactions of batteries through Li<sub>2</sub>S nucleation experiments,\nthereby improving the reaction kinetics. This study provides a new\nmethod for promoting the practical application of Li–S batteries\nand narrows the gap between theoretical and experimental results through\nlong cycles and high sulfur loads.