In Situ Preparation of 1D Co@C Composite Nanorods as Negative Materials for Alkaline Secondary Batteries

Cobalt-based coordination compounds were successfully prepared via employing nitrilotriacetic acid (NTA) as a complexing agent through a mild surfactant-free solvothermal process. Cobalt ions are linked with the amino group or carboxyl groups of NTA to become one-dimensional nanorods that can be proved by Fourier transform infrared measurement findings. The morphologies of the precursor Co-NTA highly depend on the solvent composition, the reaction time and temperature. The probable growth mechanism has been proposed. After heat treatment, the Co-NTA precursor can be completely converted into Co@C nanorods assembled by numerous core-shell-like Co@C nanoparticles, which preserved the rodlike morphology. The as-prepared Co@C composites display a rodlike morphology with 4 μm length and 100 nm diameter. The electrochemical performances of this novel Co@C material as the alkaline secondary Ni/Co battery negative electrode have been systematically researched. The discharge capacity of the Co@C-1 composite electrode can attain 609 mAh g(-1) and retains about 383.3 mAh g(-1) after 120 cycles (the discharge current density of 500 mA g(-1)). The novel material exhibits a high discharge capacity of 610 and 470 mAh g(-1) at discharge currents of 100 and 1000 mA g(-1), respectively. This suggests that approximately 77% of the discharge capacity is kept when the discharge current density is increased to 1000 mA g(-1) (10 times the initial current density of 100 mA g(-1)). The excellent electrochemical properties could be ascribed to the porous channels of the novel Co@C materials, which is beneficial to electrolyte diffusion and electrons and ions transportation.