Balancing Anchoring and Diffusion for Screening of Metal Oxide Cathode Materials in Lithium–Sulfur Batteries

Unfavorable factors such as the shuttle effect caused by soluble lithium polysulfides, insulation of S and Li2S, and large volume expansion of S have greatly hindered the practical application of lithium–sulfur batteries. Using sulfur cathodes based on metal oxide nanocomposite materials has been proven to be an effective method to overcome the abovementioned problems and accomplish long-term cycle stability, excellent conductivity, and high-rate capacity. However, there is still a lack of clear mechanism research to balance between adsorption and diffusion and speedy selection method for oxides. Herein, we systematically studied the anchoring and diffusion properties of metal oxide MO2 (TiO2, SnO2, and RuO2) as cathode materials and then screened the materials through the equilibrium mechanism of adsorption and diffusion. According to the abovementioned research, due to its strong interaction with lithium polysulfides and low diffusion barrier for Li+, TiO2 exhibits excellent electrochemical performance and is considered to have great potential as an anchor material for lithium–sulfur batteries. Therefore, a comprehensive metal oxide selection criterion with stronger bonding strength (3–5 eV) and a lower diffusion barrier (<0.4 eV) is proposed. This work provides general guidance for the construction and screening of cathode materials to attain high-performance batteries in the future.