Abstract
Severe shuttle effect will deteriorate electrochemical performances of alkali metal-sulfur batteries involving lithium- or sodium-sulfur batteries. In this paper, the interaction mechanism between Co9S8 and polysulfides (Li2Sn/Na2Sn) has been investigated thoroughly via the first-principles calculations. Both band structure and density of state show the metallicity of Co9S8, implying its positive role in conductivity improvement for cathodes. The adsorption energies of Co9S8 towards long-chain Na2Sn are larger than those towards Li2Sn, indicating a more effective suppression of Co9S8 on shuttle effect in Na-S than Li-S system. Co9S8 also exhibits a catalytic property to beneficially decrease the Gibbs free energy barrier and thus speed up electrochemical reactions. Co9S8 has been verified theoretically to be a promising cathode material for alkali metal-sulfur batteries.
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