Co3O4 negative electrode material for rechargeable sodium ion batteries: An investigation of conversion reaction mechanism and morphology-performances correlations

Transition metal oxides have recently aroused a renewed and increasing interest as conversion anode materials for sodium ion batteries. Being their electrochemical performances strongly dependent on morphological aspects, has been here proposed a straightforward approach to modulate morphological characteristics of a transition metal oxide (Co3O4) using a low cost synthetic route. The as obtained optimized morphology allows the realization of high practical specific capacities, higher than 500 mAh g−1 after 50 cycles, and represents a valid candidate for further optimization. In addition to the morphology-performance correlations, the reaction mechanism beyond the electrochemical behavior was also investigated revealing the role of the CoO phase in the charge/discharge process. Finally, an electrode pre-sodiation treatment for conversion materials is presented: it has been indeed demonstrated that it sensibly decreases the irreversible capacity correlated to the first cycle and improves cycle ability.