NiCo Nanoparticles Encapsulated in Nitrogen-Doped Carbon Tubes as Anode Materials for High-Performance Lithium-Ion Batteries

A novel solution has been proposed in this study to address electrode chalking and capacity degradation issues associated with transition metals as anodic materials in Li-ion batteries. The new strategy is based on constructing nitrogen-doped carbon shell-covered transition metal nanoparticles. In this study, the design of one-dimensional nanotubes and the introduction of nitrogen atoms improve electronic conductivity and electrode integrity and also provide abundant active sites for lithium-ion battery reactions. In the first step, carbon-coated NiCo compounds were synthesized by using acetate ions as the carbon source and Ni and Co as the metal sources. Subsequently, nitrogen-doped carbon CNT-encapsulated NiCo nanoparticles (NiCo-N-C-1, NiCo-N-C-2, and NiCo-N-C-3) were successfully prepared by utilizing the precursors from the first step and using melamine as the nitrogen source for introducing nitrogen atoms. The unique one-dimensional nanotube structure of NiCo-N-C-2 anodes demonstrated a discharge capacity equal to 639.4 mAh g^-1 following 300 cycles at a current density (I_d) equal to 0.5 A g^-1 with an extended reversible capacity equal to 442.5 mAh g^-1 following 1400 cycles at I_d = 2 A g^-1, demonstrating the potential application of NiCo-N-C-2 nanotubes in Li-ion batteries with a high power density and an extended cycle life. Moreover, as it was coupled with the LiFePO₄ cathode, the prepared Li-ion full cell demonstrated a capacity retention equal to 91.4% following 500 cycles at I_d = 1 C (0.1 C=170 mA h g^-1), further highlighting the high capacity, excellent multiplication, and cycling performance of the NiCo-N-C electrode. This simple synthesis strategy offers a new approach to fabricating high-performance carbon and nitrogen-clad metal particle composites with promising applications in various energy-related fields.