Preparation Of Transition Metal Sulfide And Study Of The Supercapacitor Performance

Supercapacitor is a new type of energy storage component with high power density,long cycle life,and environmental friendliness.With its unique advantages,supercapacitor has received extensive attention by researchers.And electrode material that is the most critical part of supercapacitors can directly determine the performance.Among them,transition metal sulfides have been extensively studied for virtues of their higher capacitance than carbon materials and better electrical conductivity than transition metal oxides.At the same time,good micro-structure and reasonable construction methods can be used to improve the performance of supercapacitors.In this paper,transition metal sulfides electrode materials were prepared by a simple method,and the physical properties such as crystal structure and microstructure of the prepared materials were analyzed by X-ray diffractometer,scanning electron microscope,X-ray energy spectrometer,transmission electron microscope and so on.At the same time,the supercapacitor performance was investigated using cyclic voltammetry,galvanostatic charge/discharge and electrochemical impedance spectroscopy.The CuCo2S4 nanowire arrays with an average diameter of about 80 nm were directly grown on the nickel foam by a two-step hydrothermal method,and its optimum vulcanization concentration was explored.The ultra-high specific capacitance was obtained due to its good microstructure.At the current density of 1 A·g^-1,the CuCo₂S₄ electrode has a high specific capacitance of 2466.6 F·g^-1,and it has good cycle stability（after 10,000 cycles,the specific capacitance can still maintain at 82%）.At the same time,the asymmetric supercapacitor assembled with activated carbon（AC）achieved a high energy density of 33.4 Wh·kg^-1 at a power density of 751.5 W·kg^-1.And at a current density of 4 A·g^-1,the specific capacitance can maintain at 78%after 10,000 cycles.Nitrogen-doped carbon foam（NCF）was prepared by temperature-programmed direct high-temperature carbonization of melamine foam（MF）,and its supercapacitor performance as a carbon material was tested.The NCF has a specific capacitance of 236 F·g^-1 at a current density of 1 A·g^-1,and after 10,000 cycles,the specific capacitance retention is 95%.The assembled NCF//NCF symmetric supercapacitor achieved a high energy density of 22.5Wh·kg^-1 at a power density of 1000 W·kg^-1,and at a current density of 4 A·g^-1,the capacitor retention rate is 83%after 10,000 cycles.The Ni₃Co₆S₈ nanowire arrays with an average diameter of around 70 nm were grown directly on the nitrogen-doped carbon foam（NCF）by combining the first two experiments.At a current density of 1 A·g^-1,the Ni₃Co₆S₈ electrode has a high specific capacitance of 2507.14F·g^-1,and at a current density of 10 A·g^-1,the specific capacitance can still reach 1914.3 F·g^-1,after 10,000 charge and discharge cycles,the specific capacitance retention rate is 89%,which shows its excellent rate performance and cycle stability.At the same time,an all-solid-state asymmetric supercapacitor was assembled with NCF as the negative electrode,achieving a high energy density of 28.31 Wh·kg^-1 at a power density of 675 W·kg^-1.At a current density of 4 A·g^-1,the specific capacitance retention rate is 84%after 10,000 cycles,which verified the abilities of NCF as a negative electrode and a matrix,and the performance of the mixture of the two materials was also obtained.These indicate that the prepared electrode has the potential to be an excellent material for supercapacitors and wearable flexible energy storage devices.