Metal-Organic Framework Derived CoS₂ Wrapped with Nitrogen-Doped Carbon for Enhanced Lithium/Sodium Storage Performance

Transition metal sulfides are attractive electrode materials for both lithium-ion (LIBs) and sodium-ion batteries (SIBs). Starting from micron-sized Co(IPC)·H₂O (IPC: 4-(imidazole-1-yl) phthalic acid) and polydopamine as the metal-organic framework (MOF) precursor and carbon source, respectively, we produced a CoS₂/C/C composite constituting CoS₂ nanoparticles decorated with N-doped carbon layers and subjected to sulfurization. N-doped carbon layers provided a robust network for the CoS₂ nanoparticles, enhancing the structural integrity and electronic conductivity of the resulting CoS₂/C/C composite, which exhibited electrochemical performance superior to most existing CoS₂ composites, and was one of the best among all MOF derived CoS₂ anodes for LIBs and SIBs. The use of nanosized CoS₂ particles reduced the diffusion length for the transfer of Li⁺/Na⁺ ions, resulting in a high specific capacity at a higher current rate. N-doped carbon layers derived from the MOF precursor and polydopamine provided an electrically conductive network between the CoS₂ nanoparticles, thus preventing their aggregation and inhibiting adverse side reactions between the electrolyte and the surface of the electrode, and the high pseudocapacitive contribution resulted in the enhanced rate performance of the CoS₂/C/C electrodes.