Nanoscale N-Doped Carbon/NiCl₂ Nanocomposite as High Conductivity Cathode for Thermal Battery

Nickel chloride (NiCl2) is considered an excellent cathode material for thermal batteries because of its high specific capacity and operating voltage. However, low conductivity and the melt overflow of the electrode material greatly limit the practical application of NiCl2 cathode material. Herein, in this work, a NiCl2-based cathode material featuring a structurally disordered nanoscale nitrogen-doped carbon (N–C) skin structure, synthesized through high-temperature carbonization of melamine and sucrose. The N–C surface-modified NiCl2 nanocomposite demonstrates a specific energy of up to 630.63 W h·kg–1 and low internal resistance of 0.157 Ω at 300 mA·cm–2, with an effective reduction in average internal resistance of 40.00% compared to NiCl2. This improvement is attributed to the doping of heteroatomic nitrogen, which results in the formation of vacancy defects and active sites within the carbon material, thereby effectively improving the electrical conductivity of NiCl2. Furthermore, the nanoscale N–C modification layer acts as a protective barrier to inhibit the adverse reactions between NiCl2 and electrolyte, thus reducing melt overflow from the electrode. This strategy of nanoscale heteroatom-doped carbon surface modification was inaugural applied to NiCl2 cathode materials, yielding promising outcomes, providing a potential reference for optimizing the performance of other electrode materials.