A bifunctional NiS2@MXene (Ti3C2Tx) composite separator for high-performance lithium–sulfur batteries with enhanced polysulfide inhibition and uniform lithium-ion transport

Abstract

Capacity degradation from uncontrolled polysulfide diffusion and dendrite growth at the anode are key challenges in lithium–sulfur batteries. A NiS₂@MXene (Ti₃C₂T_x) composite separator is designed to anchor polysulfides and facilitate uniform Li⁺ transport, aiming to effectively tackle these challenges. Finite element simulations were conducted to analyze the Li⁺ transport mechanisms in high-density MXene and NiS₂@MXene channels, with the aim of gaining insights into dendrite growth and Li nucleation. Additionally, an innovative in situ optical visualization cell is developed to observe the polysulfide anchoring of NiS₂@MXene composite separators during cycling. Electrochemical testing results show effective suppression of the shuttle effect with NiS₂ and MXene synergy, as evidenced by the Li⁺ diffusion coefficient and Li₂S deposition. The NiS₂@MXene modified separator exhibits outstanding performance in capacity tests and demonstrates potential for high sulfur loading, while highlighting its practical applicability. Overall, in the NiS₂@MXene composite separator, which is developed in this work, NiS₂ particles adsorb polysulfides to hinder the shuttle effect, while MXene offers multiple ion diffusion channels. The composite separator is anticipated to reduce polysulfide shuttling and promote uniform Li⁺ transport through the combined effects of NiS₂ nanoparticles and the MXene matrix.