A Synergistic Na-Mn-O Composite Cathodes for High-Capacity Na-Ion Storage

Searching for new-type cathodes to enhance the capacity of Na-ion batteries is one of the hot spots in energy storage systems. Many sodium insertion transition metal oxides, i.e., Na-Mn-O compounds, are intensively studied owing to their high voltage, abundant resources, and low toxicity. However, its relatively low capacity greatly limits its application. Here, a new synergistic composite, 0.44Na(4)Mn(2)O(5)center dot 0.56Na(0.7)MnO(2), is developed by a feasible method of organic-acid-assisted drying and heat treatment. This synergistic composite cathode delivers a reversible sodium storage capacity as high as 278.0 mAh g(-1) and stable framework structure due to the synergistic effect. It is achieved by the synergistic effect of high capacity Na4Mn2O5 with multiple Na+ ions insert/extract sites and stable Na0.7MnO2 with layered structure. Even when tested at a high mass loading of 7.42 mg cm(-2), this composite cathode demonstrates stable cycling over 400 cycles for sodium storage. Moreover, when coupled with hard carbon anode, Na-ion full battery delivers excellent charge/discharge performance with capacity retention of 84.0%, showing great application potential in the large-scale energy storage field.