An insight into the sodium-ion and lithium-ion storage properties of CuS/graphitic carbon nitride nanocomposite

Metal sulfides are gaining prominence as conversion anode materials for lithium/sodium ion batteries due to their higher specific capacities but suffers from low stability and reversibility issues. In this work, the electrochemical properties of CuS anode material has been successfully enhanced by its composite formation using graphitic carbon nitride (g-C₃N₄). The CuS nanoparticles are distributed evenly in the exfoliated g-C₃N₄ matrix rendering higher electronic conductivity and space for volume alterations during the repeated discharge/charge cycles. The 0.8CuS:0.2g-C₃N₄ composite when used as an anode for lithium ion coin cell exhibits a reversible capacity of 478.4 mA h g^-1 at a current rate of 2.0 A g^-1 after a run of 1000 cycles which is better than that reported for CuS composites with any other carbon-based matrix. The performance is equally impressive when 0.8CuS:0.2g-C₃N₄ composite is used as an anode in a sodium ion coin cell and a reversible capacity of 408 mA h g^-1 is obtained at a current rate of 2.0 A g^-1 after a run of 800 cycles. A sodium ion full cell with NVP cathode and 0.8CuS:0.2g-C₃N₄ composite anode has been fabricated and cycled for 100 runs at a current rate of 0.1 A g^-1. It can be inferred that the g-C₃N₄ matrix improves the ion transfer properties, alleviates the volume alteration happening in the anode during the discharge/charge process and also helps in preventing the leaching of polysulfides generated during the electrochemical process.