Prussian blue analog Co₃[Co(CN)₆]₂ as a cathode material for lithium–sulfur batteries

In this work, the authors proposed a unique strategy to prepare a high performance Lithium–Sulfur (Li–S) battery cathode by an N-rich nano-graphene hollow sphere from the Prussian blue analog Co₃[Co(CN)₆]₂. The one-pot solution method with low cost materials was designed to synthesize the cathode by annealing with different temperatures and consistent HCl etching steps for the precursor. The Li–S batteries made by this precursor showed remarkable charge–discharge stability (570.4 mA h g⁻¹ after 500 cycles at a 1 C current density) and outstanding rate performance (1145.5, 717.9, and 672.5 mA hg⁻¹ at 0.1, 1.0, and 2.0 Ag⁻¹ current densities) at 800 °C. The results indicated that the stable three-dimensional multi-layer hollow sphere structure relieved the volume expansion of sulfur, which had a significant impact on the polysulfide adsorption, inhibiting the “shuttle effect.” Also, the rich doping of nitrogen in this structure produced many defects and active sites that improved the interfacial adsorption of polysulfides. While Co₃[Co(CN)₆]₂ shows its potential as a cathode material, the material design method used in this paper provides a unique approach to realizing a high performance sulfur cathode for Li–S batteries.