Double-walled N-doped carbon@NiCo2S4 hollow capsules as SeS2 hosts for advanced Li–SeS2 batteries

Abstract

Selenium sulfide as a new class of cathode materials can enhance the conductivity of insulating sulfur which causes rapid capacity degradation and low coulombic efficiency of lithium–sulfur (Li–S) batteries. In this work, selenium disulfide (SeS₂) as an active ingredient is encapsulated into double-walled N-doped carbon (NC)@NiCo₂S₄ hollow capsules (NiCo₂S₄@NC) to obtain high-performance Li–SeS₂ batteries. On the basis of ensuring excellent electrical conductivity, the hollow NiCo₂S₄ lining and its NC coating can not only suppress the shuttle effect of polyselenium/sulfide by the combined merits of chemical adsorption and physical constraint, but also are able to buffer the volume expansion of SeS₂. Moreover, the polar NiCo₂S₄ is beneficial for enhancing the redox kinetics of lithium polyselenium/sulfide. As expected, the NiCo₂S₄@NC–SeS₂ cathode delivers high reversible capacities of 1205.1 mA h g⁻¹ at 0.1C and 673.5 mA h g⁻¹ at 2.0C. More importantly, the hybrid cell can show ultralong cycling life up to 800 cycles at 1.0C with the attenuation rate as low as 0.038% per cycle, which is superior to that of NiCo₂S₄–SeS₂ and NC–SeS₂ composites.