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Conversion-type anode materials have been intensely studied for application in Li-ion batteries (LIBs) due to their potentially higher capacities than current graphite-based anodes. This work reports the development of a high-capacity and stable anode from a nanocomposite of N and S co-doped carbon spheres (NSCSs) with Co 3 O 4 (NSCS-Co 3 O 4 ). A hydrothermal reaction of saccharose with l-cysteine was carried out, followed by its carbonization. CSs when used as supports for conversion-type materials provide efficient electron/ion transfer channels, enhancing the overall electrochemical performance of the electrodes. Additionally, the heteroatoms doped in a carbon matrix alter the electronic properties, often increasing the reactivity of the carbon surface, and they are reported to be effective for anchoring metal oxide nanoparticles. Consequently, the NSCS-Co 3 O 4 nanocomposites developed in this work exhibit enhanced and stable reversible specific capacity over several cycles. Stable cycling behavior was observed at 1 A g -1 with 1285 mA h g -1 of specific capacity retained after 350 cycles along with more than 99% of coulombic efficiency. This material shows excellent rate capability with a specific capacity of 745 mA h g -1 retained even at a high current density of 5 A g -1 . Detailed DFT-based calculations revealed the role of doped supports in controlling the volume expansion upon lithiation., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)