Facile preparation of Co@Co3O4@Nitrogen doped carbon composite from ionic liquid as anode material for high performance lithium-ion batteries

Co@Co3O4@Nitrogen doped carbon (Co@Co3O4@NDC) composite is synthesized by high temperature carbonization of ionic liquids followed by low temperature thermal oxidation. In the process of high temperature carbonization, cobalt ions are reduced to metallic cobalt, producing Co@Nitrogen doped carbon (Co@NDC). Co@Co3O4@NDC composite is obtained after low temperature oxidation, in which a part of the metallic cobalt is oxidized to Co3O4. The structural characterizations indicate that the composite is composed of three crystalline phases (carbon, Co and Co3O4). The results of transmission electron microscopy study show that the carbon materials not only coat the Co@Co3O4 nanoparticles, but also form carbon network that connects the Co@Co3O4 nanoparticles. This conductive carbon network is beneficial to improve the electrochemical performance of the composite. The electrochemical test results show that the Co@Co3O4@NDC composite exhibits excellent electrochemical performance, delivering the discharge capacities of 790 and 304 mAh·g−1 after 1500 cycles at 5 C and 10 C. This excellent electrochemical performance is due to synergistic effects of Co3O4, cobalt nanoparticles embedded in carbon which has high conductivity, and nitrogen functional groups.

Preparation of metallic cobalt powders by thermolysis of cobalt (II) acetate, oxalate and formate

The thermal decomposition of cobalt (II) formate, acetate, and oxalate was studied by synchronous thermal analysis. It is established that in all cases the final product is metallic cobalt. Thermogravi- metric analysis combined with differential scanning calorimetry and mass spectroscopy made it possi- ble to establish thermolysis schemes and gaseous products of salt decomposition. The conditions for obtaining powdered metallic cobalt from carboxylic acid salts are determined. It was determined by electron microscopy that the particle size and structure of metal powders depend on the type of initial salt.

REGULARITIES OF SYNTHESIS OF COBALT PARTICLES DURING REDUCTION OF COBALT IONS IN THE PRESENCE OF POLY-N-VINYLPYRROLIDONE

The reduction of cobalt ions in the presence of poly-N-vinylpyrrolidone in aqueous solutions has been studied by spectrophotometric analysis, scanning electron microscopy, and transmission electron microscopy. It was shown that at the initial stage of the reduction of cobalt ions, the formation of metal particles of cobalt with a size of 2-5 nm occurs. A day later, aggregates of 28-45 nm in size are formed, which are a mixture of metallic cobalt, its oxide and hydroxide.