Cobalt atoms dispersed on hierarchical carbon nitride support as the cathode electrocatalyst for high-performance lithium-polysulfide batteries

Lithium-sulfur batteries are promising candidates for next-generation energy storage but are confronted with several challenges. One of the possible solutions is to design proper cathode electrocatalysts to accelerate the redox interconversion of solvated polysulfide intermediates. Herein, we report cobalt atoms dispersed on hierarchical carbon nitride support as an effective cathode electrocatalyst for lithium-polysulfide batteries. The electrocatalyst material is prepared from the simple reaction between melamine and cyanuric acid in the presence of Co2+, followed by the Ar annealing. The product has a unique hierarchical structure consisting of many thin and porous C3N4 nanosheets finely dispersed with Co atoms. The atomic dispersion of Co species is confirmed by X-ray absorption experiments. Electrochemical measurements reveal that it can promote the interconversion of polysulfides. As a result, batteries using this cathode electrocatalyst achieve large capacity (∼1400 mAh/g at 1.6 mA/cm2), good rate performance (∼800 mAh/g at 12.8 mA/cm2) and impressive cycling stability under different current densities and different sulfur loadings.