Ionic liquid-derived Co.sub.3O.sub.4/carbon nano-onions composite and its enhanced performance as anode for lithium-ion batteries

In this work, a novel composite of Co.sub.3O.sub.4 nanoparticle and carbon nano-onions (CNOs) is synthesized by using ionic liquid as carbon and nitrogen source through a facile carbothermic reduction followed by low-temperature oxidation method. The SEM and HRTEM images reveal that the Co.sub.3O.sub.4 particles are homogenously embedded in the CNOs. Due to the unique nano-structure, the electrolyte contacts well with the active materials, leading to a better transfer of lithium ions. Moreover, the unique nano-structure not only buffers the volume changes but also facilitates the shuttling of electrons during the cycling process. As a result, the electrode made up of Co.sub.3O.sub.4/CNOs composite delivers favorable cycling performance (676 mAh g.sup.-1 after 200 cycles) and rate capability (557 mAh g.sup.-1 at the current of 1 C), showing a promising prospect for lithium-ion batteries as anode materials.