| Sustainable,clean energy is a current global reality and it is vital to develop efficient and practical energy storage systems to meet the energy needs of a growing society.Over the past few decades,electrochemical energy storage devices,including rechargeable batteries and ultracapacitors,have attracted a great deal of attention due to their widespread use in hybrid vehicles,smart portable electronics,as well as industrial power supplies,and energy management.Supercapacitors can meet high power and high energy density application scenarios in comparison to rechargeable batteries.The Faraday-behaved battery-type cobalt-based binary transition metal sulfides have a high theoretical capacity compared to double-layer capacitors.Boosting the capacitance of the material is one of the best ways to be used to increase energy density in addition to the extended potential window approach.The design of bimetallic sulfides with high performance to enhance the energy density and power density of asymmetric supercapacitors（ASC）using the combined contribution of the components and the synergy between the individual elements and modulating the morphological structure of the material during preparation is one of the current research focuses.In the last few years,there has been a greater scientific push to develop asymmetric supercapacitors,which feature two electrodes with different energy storage mechanisms and are relatively superior in terms of energy and power density.In this paper,spinel-structured MCo2S4（M=Ni,Cu）materials were synthesized by hydrothermal and solvent thermal methods,and their physical properties were characterized and tested for their electrochemical performance.The main studies are as follows:（1）A foam structure NiCo2S4（FSNCS）with a specific surface area of 25.4 m2 g-1was synthesized by a simple solvothermal method.The well-dispersed Si O2nanospheres were used as the skeleton to greatly reduce the“dead volume”caused by the accumulation of synthetic products.When the current density is 1 A g-1,the performance of FSNCS is 559.3 C g-1,173.3 C g-1 higher than that of NCS without Si O2.The FSNCS//AC hybrid devices were fabricated with NiCo2S4 and activated carbon as positive and negative electrodes respectively.The maximum energy density in the experimental range is 28.8 Wh kg-1,and the hybrid device exhibited excellent cycle life with a capacity retention of 88.9%after 5000 charge/discharge cycles.The hybrid supercapacitor enables the assembled 3 W motor fan to run for 59s.（2）Nanosheet CuCo2S4 was successfully prepared by a two-step hydrothermal method.the prepared CuCo2S4 was observed by scanning electron microscopy（SEM）to have a well-defined hierarchical sheet structure.Due to its unique layered structure,the nanosheet CuCo2S4 has a large specific surface area(20.65 m2 g-1)and exhibits good energy storage performance,the capacity of nanosheet CuCo2S4 can reach 268.5C g-1 at 0.5 A g-1 current density.（3）To obtain a better energy density for the hybrid supercapacitor,ZIF-L was prepared by co-precipitation,and a derivative carbon cathode with a specific surface area of 1400.27 m2 g-1 was successfully obtained by carbonization and hydrochloric acid washing,and the resulting product was proved by XPS analysis to be N-doped ZIF-L-derived carbon（NZC）,which exhibited a specific capacitance of 288.1 F g-1 at a current density of 0.5 A g-1.The hybrid capacitor CuCo2S4//NZC showed an energy density of 25.7 Wh kg-1 at a specific power of 374.8 W kg-1.In addition,after 5000cycles at a current density of 5 A g-1,the capacitance retention was 87.6%,which has good potential for application. |
