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

Abstract

Unfavorable factors such as the shuttle effect caused by soluble lithium polysulfides, insulation of S and Li 2 S, 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 longterm 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 MO 2 (TiO 2 , SnO 2 , and RuO 2 ) 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 + , TiO 2 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.

Non-Negligible Role of Multifunctional MXene Hosts for Li–S Batteries: Anchoring and Electrocatalysis

“…The following reduction steps, from Li 2 S 8 to Li 2 S, are almost all endothermic. The previous researches showed that the step with the largest positive Gibbs free energy barrier (Δ G barrier ) is the most difficult step for SRR in Li–S batteries. , According to the calculated equation of Δ G , , the Δ G barrier of SRR varies significantly depending on the difference in anchoring ability to Li 2 S n . Such as LiPSs adsorbed on Cr 2 CO 2 , Li 2 S 8 has the strongest adsorption energy, while Li 2 S 6 has a relatively weak interaction energy, resulting in a high barrier for Li 2 S 8 → Li 2 S 6 (1.338 eV).…”