Synthesis of CoTe nanowires: a new electrode material for supercapacitor with high stability and high performance.

Highly dispersed CoTe electrode material were successfully prepared by using a facile one-step solvothermal process without any surfactants. Compared with the conventional hydrothermally prepared irregularly-shaped CoTe, a regular nanowire-formed CoTe can be obtained by a solvothermal process using ethylene glycol as a solvent. The prepared CoTe nanowire electrode can exhibit a relatively high specific capacity of 643.6 F g at a current density of 1 A g and remarkable cyclic stability with 76.9% of its specific capacitance retention after 5000 cycles at a high current density of 5 A g. Besides, even at the high current density of 20 A g, the specific capacitance of CoTe nanowire electrode still has 90.2% retention relative to 1 A g, showing an excellent rate performance. In order to enlarge the potential window to increase the energy density, an asymmetric supercapacitor (ASC) is assembled by applying CoTe nanowires and activated carbon as the positive electrode and the negative electrode in 3 M KOH, which can enlarge the operating voltage to as high as 1.6 V, and shows a specific capacity of 92.5 F g with an energy density of 32.9 Wh kg and power density of 800.27 W kg at 1 A g, and even after 5000 cycles of charge/discharge at 5 A g, the ASC still retains 90.5% of its initial specific capacitance, showing excellent cycle stability.