Abstract
CoTe@reduced graphene oxide (CoTe@rGO) electrode materials for supercapacitors were prepared by a one-step hydrothermal method in this paper. Compared with that of pure CoTe, the electrochemical performance of CoTe@rGO was significantly improved. The results showed that the optimal CoTe@rGO electrode material has a remarkably high specific capacitance of 810.6 F/g at a current density of 1 A/g. At 5 A/g, the synthesized material retained 77.2% of its initial capacitance even after 5000 charge/discharge cycles, thereby demonstrating good cycling stability. Moreover, even at a high current density of 20 A/g, the composite electrode retained 79.0% of its specific capacitance at 1 A/g, thus confirming its excellent rate performance. An asymmetric supercapacitor (ASC) with a wider potential window and higher energy density was assembled by using 3 M KOH as the electrolyte, the CoTe@rGO electrode as the positive electrode, and active carbon as the negative electrode. The operating voltage of the supercapacitor could be increased to 1.6 V, and its specific capacitance could reach 112.6 F/g at 1 A/g. The specific capacitance retention rate of the fabricated supercapacitor after 5000 charge/discharge cycles at 5 A/g was 87.1%, which confirms its excellent cycling stability. In addition, the ASC revealed a high energy density of 40.04 W·h/kg at a power density of 799.91 W/kg and a high power density of 4004.93 W/kg at an energy density of 33.43 W·h/kg. These results collectively show that CoTe@rGO materials have broad application prospects.
Highlights
Continuous developments in the economy and society have led to the exhaustion of traditional non-renewable energy sources, including fossil fuels
Where Cm (F/g) is the mass specific capacitance; I (A) and Δt (s) are the discharge current and time, respectively; m (g) is the mass of the active substance loaded onto the electrode; Fig. 4 Electrochemical properties of CoTe@rGO samples with different masses of reduced graphene oxide: a Galvanostatic charge/discharge curves and b specific capacitance curve
CoTe@rGO composite materials were successfully synthesized by adding GO to the reaction materials
Summary
Continuous developments in the economy and society have led to the exhaustion of traditional non-renewable energy sources, including fossil fuels. As a new type of energy storage device, supercapacitors can fill the gap between traditional capacitors and chemical batteries on account of its many advantages, which include high power density, high energy density, and long cycle life [5,6,7,8]. One of the most important methods to improve the performance of supercapacitors is to develop new types of electrode materials. In 2007, Tao et al [9] obtained CoS electrode materials with a specific capacitance of 475 F/g at a current density of 5 mA/ cm via the hydrothermal reaction by using NaS·9H2O as a sulfur source and Co(CH3COO)2·4H2O as a cobalt source. In 2013, Wang et al [11]prepared CoSe nanotube-based electrode materials via a one-step hydrothermal method using Co(CO3)0.35Cl0.20(OH)1.10 as the cobalt source and NaHSe as the selenium source; the authors obtained a specific capacitance of 238 F/g at 1 A/g.
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