Preparation And Electrochemical Properties Of Cobalt–based Composites As Anode Materials For Lithium Ion Battery

High performance lithium ion batteries are urgently needed by high power electronic devices（such as electric cars）. Recently, graphite and other carbon materials are the main anode materials for lithium ion battery. However, the lithium storage capacity of these carbon anode materials is not high, consequently, limits the lithium ion battery to further improve the energy density to a certain extent. Therefore, the development of the high capacity lithium ion electrode materials is very urgent. Inorganic compounds which contain cobalt, such as sulfide cobalt and cobalt sulfate, etc., have been applied in lithium ion batteries because of their unique physical and chemical properties. Futher, with the protection of the carbon materials, such as grapheme and amorphous porous carbon, their capacity might be improved.In this paper, we have synthesized dually protected and hollow structure a-C@GNs@Co₉S₈nanocomposites and three-dimensional structure a-C@CoSO₄@GNs nanocomposites. Through XRD, Raman, XPS, TGA, SEM, TEM and CV, EIS and constant current charge and discharge tests, we observed these nanocomposite compositions, morphologies, sizes, microstructures and electrochemical properties.（1） GNs@Co₉S₈ hollow structure nanocomposites were obtained by heat injection method.We get the dual protection nanocomposites of a-C@GNs@Co₉S₈ by the thermal decomposition method with the assistant of Arabic gum. As the nanocomposites were used as anode materials, the electrochemical performanceswere explored under the temperature range from-20℃ to 70℃. When the temperature is 70℃, the electrode materials showed excellent reversible specific capacity of 910mAhg-1at the current density of 500mAg-1 after 100 cycles.（2） a-C@CoSO₄@GNswith 3D structure nanocomposites were yielded through hydrothermal and thermal decomposition processes with the assistant of Arabic gum. Compared with graphite anode materials with the theoretical specific capacity of 372 mAh g-1, a-C@CoSO₄@GNs nanocomposites achieved higher reversible specific capacity of 532.4mAh g-1under the current density of 1.5A g-1; When the current density came back to 200mAg-1, the reversible specific capacity were back to 823.5mAh g-1after six cycles. During the rate capabilities test, the coulomb efficiency of a-C@CoSO₄@GNs electrode materials remained nearly 100%.