Experimental and theoretical investigations of the effect of heteroatom doped Carbon microsphere support on stability and storage capacity of nano-Co3O4 conversion anode for Lithium-ion batteries

Conversion type anode materials are intensely being studied for Li-ion batteries (LIBs) for their potentially higher capacities over current graphite-based anodes. This work describes the development of high capacity and stable anode from a nanocomposite of N and S co-doped Carbon spheres (NSCS) with Co3O4 (NSCS-Co3O4). Hydrothermal reaction of saccharose with L-cysteine has been carried out followed by its carbonization. CSs, when used as support for conversion type materials provide efficient electron/ion transfer channels enhancing the overall electrochemical performance of the electrodes. Additionally, hetero atoms doped in carbon matrix alter the electronic properties, often increasing the reactivity of the carbon surface and reported to be effective for anchoring metal oxide nanoparticles. Consequently, the NSCS-Co3O4 nanocomposites developed in this work exhibit enhanced and stable reversible specific capacity over the cycling. Stable cycling behavior is observed at 1 Ag-1 with 1285 mAhg-1 of specific capacity retained after 350 cycles along with more than 99% of coulombic efficiency. This material shows an excellent rate capability with specific capacity retained to 745 mAhg-1 even at a high current density of 5 Ag-1. Detailed DFT based calculations have revealed the role of doped support in controlling the volume expansion upon lithiation.