Strategies to Explore and Develop Reversible Redox Reactions of Li–S in Electrode Architectures Using Silver-Polyoxometalate Clusters

Investigations of the Ag (I)-substituted Keggin K₃[H₃Ag^IPW₁₁O₃₉] as a bifunctional Lewis acidic and basic catalyst are reported that explore the stabilization of Li₂S_n moieties so that reversible redox reactions in S-based electrodes would be possible. Spectroscopic investigations showed that the Li₂S_n-moieties can be strongly adsorbed on the {Ag^IPW₁₁O₃₉} cluster, where the Ag(I) ion can act as a Lewis acid site to further enhance the adsorption of the S-moieties, and these interactions were investigated and rationalized using DFT. These results were used to construct an electrode for use in a Li-S battery with a very high S utilization of 94%, and a coulometric capacity of 1580 mAh g^-1. This means, as a result of using the AgPOM, both a high active S content, as well as a high areal S mass loading, is achieved in the composite electrode giving a highly stable battery with cycling performance at high rates (1050 and 810 mAh g^-1 at 1C and 2C over 100 to 300 cycles, respectively).