Influence of Ga2O3, CuGa2O4 and Cu4O3 phases on the Sodium-ion Storage behaviour of CuO and its Gallium composites
CuO and its gallium composites with various compositions are successfully fabricated by using hydrothermal technique followed by calcination at 900°C. The added Ga precursor in the composites formed as oxides such as Ga2O3, CuGa2O4 and Cu4O3 are confirmed through X-ray diffraction patterns as well as from HRTEM and SAED patterns. Further HRTEM analysis also confirmed that Cu4O3 and CuGa2O4 phases reside on the surface of CuO in the composites with CuO and Ga composition is 90:10. The content of the various oxide phases are varied when we increase the Ga composition in the CuO composites. The change of the ratio of CuO and Ga precursor in the composites is quite effective in tailoring the sodium-ion storage behaviour of CuO. The resultant CuO/Ga composites exhibit remarkable electrochemical performance for sodium-ion batteries in terms of capacity, rate capability and cycling performance. The composite CuO-90% and Cu/Ga oxides-10% delivers the highest charge capacity of 661 mAhg-1 at the current density of 0.07 Ag-1 with the capacity retention of 73.1% even after 500 cycles. The structure and morphology of the composite (CuO-90% and Cu/Ga oxides-10%) is successfully retained after 500 cycles which are confirmed through ex-situ XRD and HRTEM analysis. The composite also exhibit remarkable rate capability in which it delivers 96 mAhg-1 even at the high current density of 6.6 Ag-1. The enhanced electrochemical performance of CuO and its gallium composites are attributed to the presence of Cu4O3 and CuGa2O4 phases in which Cu4O3 phase actively involved in the redox reaction as well as CuGa2O4 phase stabilize the CuO phase and buffering the volume expansion of CuO during cycling. The present approach explores great opportunities for improving the electrochemical performance of oxide based anode materials for sodium-ion batteries.