Hierarchically structured Co ₃ O ₄ nanoparticles as lithium-ion battery anodes

Lithium-ion battery (LIB) performance is often limited by the relatively low capacity of graphite anodes, motivating the development of alternative materials with higher energy storage capabilities. Spinel cobalt oxide (Co3O4) has emerged as a promising conversion-type anode due to its high theoretical capacity. However, its practical application is hindered by capacity fading and an incomplete understanding of its reaction mechanisms. In this study, hierarchically structured Co3O4 nanoparticles were synthesised via a controlled precipitation-calcination route, yielding phase-pure spinel structure. The synthesized material was thoroughly characterised using X-ray diffraction, electron microscopy, and surface analysis to confirm their spinel phase and nanoscale morphology. Electrochemical evaluations demonstrate that the Co3O4 anode delivers an initial discharge capacity of approximately 1700 mAh g−1 and retains about 600 mAh g−1 after 1000 cycles at a 4C rate, indicating long-term stability even under fast charge-discharge conditions. Beyond conventional conversion reactions, analyses reveal a multi-stage lithiation mechanism involving intermediate Li-Co-O phases and significant interfacial lithium storage contributions. The observed capacity exceeding the theoretical limit is attributed to synergistic effects of surface-related lithium storage and nanoscale structural dynamics. These findings provide new insights into lithium storage mechanisms in Co3O4 and highlight its potential as a durable, high-capacity anode for next-generation LIBs.