Abstract
The ternary transitional metal oxide NiCo2O4 is a promising anode material for sodium ion batteries due to its high theoretical capacity and superior electrical conductivity. However, its sodium storage capability is severely limited by the sluggish sodiation/desodiation reaction kinetics. Herein, NiCo2O4 double-shelled hollow spheres were synthesized via a microwave-assisted, fast solvothermal synthetic procedure in a mixture of isopropanol and glycerol, followed by annealing. Isopropanol played a vital role in the precipitation of nickel and cobalt, and the shrinkage of the glycerol quasi-emulsion under heat treatment was responsible for the formation of the double-shelled nanostructure. The as-synthesized product was tested as an anode material in a sodium ion battery, was found to exhibit a high reversible specific capacity of 511 mAh g−1 at 100 mA g−1, and deliver high capacity retention after 100 cycles.
Highlights
Due to increasing energy consumption, there is an increasing demand for energy storage materials
Many other carbonaceous materials have been intensively investigated as anode materials for sodium ion batteries (SIBs), their sodium storage capabilities are too low to meet the demands of practical applications
We developed a synthesis method for NiCo2O4 double-shelled hollow spheres, using a fast microwave-assisted solvothermal treatment followed by annealing
Summary
Due to increasing energy consumption, there is an increasing demand for energy storage materials. The depletion of lithium resources and the consequent high cost of lithium hinder the application of LIBs in several emerging areas, such as largescale grid energy storage [2]. Sodium, another Group I element, is much more abundant and has a much lower cost. Due to the sluggish sodiation/desodiation reaction kinetics, as well as the large volume change during the charging/discharging process induced by the large ionic radius of Na?, the reported NiCo2O4 materials exhibit greatly inferior capacities for sodium storage. Double-shelled hollow nanostructures are beneficial in facilitating a high specific surface area to expose more active materials for reaction, as well as in buffering the volume change during the charging/discharging process. The as-synthesized product was further tested as an anode material in SIBs and showed excellent sodium storage capability
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