Nickel vacancy tuning to tame polysulfide for Li–S batteries

Abstract

Li–S batteries have attracted tremendous attention due to their relatively high theoretical energy density and low-cost raw materials. Unfortunately, their commercial market has always been challenged by the infamous/notorious shuttle effect of soluble lithium polysulfides. Defect engineering, like vacancy adjustment, which can change the surface adsorption and catalytic processes, has been acknowledged as an efficient strategy for taming the above issue. However, how vacancies affect the adsorptive and catalytic activity of transition metal carbides used in Li–S batteries has been rarely reported. Herein, first-principles calculations are performed to reveal that the introduction of Ni vacancies (NiVs) in Ni₃ZnC_0.7 can trigger the redistribution of electrons and improve the surface polarity, promoting chemisorption and thus effectively restraining the shuttle effect. More importantly, the upshift of the p-band center and the enhanced diffusion of Li⁺ can accelerate redox kinetics. Li–S batteries using commercial polypropylene separators decorated with NiVs–Ni₃ZnC_0.7 exhibit an outstanding cycling performance. This work provides a unique perspective on manufacturing high-performance Li–S batteries.