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.