Alloying Enhanced Supercapacitor Performance Based on Oxygen-Deficient Tin Oxide Nanorod Array Electrodes

Tin dioxide (SnO2) nanostructures are potential, excellent candidates for pseudocapacitive electrodes. However, the performances are seriously limited by their low electrical conductivities. Here, we report a product of homogeneous, ordered, partially Ni–Sn alloyed, and oxygen-deficient tin oxide nanorod array on Ni foam, which was fabricated by an easy solvothermal synthesis method followed by facile thermal treatment in a safe reductive atmosphere. Such a product can directly be applied as the electrode of supercapacitors. With an increasing degree of alloying, the electrochemical behavior of the electrodes is controlled from pseudocapacitive to battery-type energy storage mechanism. The recorded maximum specific capacitance at a significantly large current density of 5 A·g–1 could reach 101.1 mAh·g–1 (or 652 F·g–1), a quite high value in battery-type supercapacitors and also very large one in tin oxide-based pseudocapacitors. More astonishingly, the optimal electrode will possess a dramatically enhanced specific capacitance after long-time charge–discharge cycling, attaining 11.4 times higher than its original value after cycling for 4000 times at 25 A·g–1, showing very excellent durability. Therefore, the present methodology would provide a simple, feasible, and safe strategy of fabricating various metal oxide-based electrodes for high-performance supercapacitors.