Hierarchical Co3O4 anode for high-performance Na-ion battery

Despite excellent theoretical perditions, sodium-ion batteries have not yet evolved as a reliable replacement of current lithium-ion technology, mostly due to a lack of high capacity-long cycling electrodes. Among the various candidates cobalt(II,III)oxide, Co₃O₄, is expected to deliver an excellent electrochemical characteristics, owing to its multi-electron conversion type nature, however, usually fails in terms of performance due to the electrode inconsistencies, associated with the poor conductivity and volumetric fluctuations. Herein, we report morphology and crystallinity engineering of the Co₃O₄ nanostructure to substantially improve the charge storage as well as cycling performance. Largely interconnected hierarchical Co₃O₄ synthesized via highly reproducible and industrially viable approach demonstrated efficient charge transport kinetics and excellent volume expansion buffering under the de/sodiation cycles. With its unique structural properties hierarchical electrode delivered an excellent reversible capacity (70 % of theoretical limit @25 mAg^-1), rate performance (123 mAhg^-1 @1Ag^-1) and stable cycling (82 % after 250 cycles @1Ag^-1). In-situ Raman analysis of the electrode reactions revealed conversion type Na-ion storage in the hierarchical type of electrodes.