Role of Ferroelectric In2Se3 in Polysulfide Shuttling and Charging/ Discharging Kinetics in Lithium/Sodium-Sulfur Batteries

Lithium-sulfur (Li-S) and sodium-sulfur (Na-S) batteries, with the advantages of ultrahigh energy density, natural abundance, and ecofriendliness, are regarded as next-generation rechargeable batteries. However, polysulfide shuttling and sluggish charging/discharging kinetics in sulfur cathodes severely hamper their practical applications. In this study, via employing first-principles calculations, we investigate two-dimensional ferroelectric In2Se3 as a promising additive to overcome these obstacles. Our studies reveal the following findings: (1) the In2Se3 monolayer has a modest adsorption strength to soluble polysulfides, which not only eliminates the notorious shuttle effect but also prevents polysulfide dissolution; (2) In2Se3 is able to significantly reduce the free energy barriers of sulfur reduction reaction and the decomposition barriers of Li2S and Na2S, thus greatly enhancing the charging and discharging efficiency; and (3) due to the strong binding ability, the polarization downward (P down arrow) surface always outperforms the polarization upward (P up arrow) surface during charging/discharging processes, enabling the effective control of battery performance by ferroelectric switching. Given these advantages, it is expected that ferroelectric In2Se3 and similar ferroelectric additives will open a new route to enhance Li-S and Na-S battery performance.

Automated summary

In this study, two-dimensional ferroelectric In2Se3 was investigated as a promising additive to overcome polysulfide shuttling and sluggish kinetics in sulfur cathodes. The findings show that In2Se3 has modest adsorption strength to soluble polysulfides, reduces energy barriers, and enables control of battery performance through ferroelectric switching, thus potentially enhancing Li-S and Na-S battery performance.