Preparation Of Transition Bimetallic Oxide/Sulfide Composite Electrode Materials And Its Supercapacitor Performance

Transition bimetallic oxide/sulfide composite has become a very promising electrode material for supercapacitors due to these advantages such as low toxicity,low cost,abundant oxidation state,no pollution,high natural abundance,high theoretical capacitance,more flexible structure and so on.In this paper,a series of transition bimetal oxide/sulfide composite electrode materials were synthesized and their electrochemical properties were investigated.The specific works are as follows:（1）A novel NiMoO₄@NiMoS₄/NF core-shell nanocomposite is facilely grown on nickel foam（NF）via hydrothermal reaction and high-temperature calcination methods.The NiMoO₄@NiMoS₄/NF shows excellent electrochemical performance.When the current density is 1 A g^-1,the specific capacity of NiMoO₄@NiMoS₄/NF reaches 1996 C g^-1,which is 7 times that of single NiMoO₄/NF at the same current density.This phenomenon can be explained that a loose and porous core-shell structure was formed after vulcanization,and this structure possesses a high specific surface area and abundant electrochemically active sites,which can greatly promote the transport and transfer of electrons and ions.Moreover,the NiMoO₄@NiMoS₄/NF has a long cycling life,and the capacity retention rate reaches 83.1%after 5000cycles at a large current density of 20 A g^-1.The hybrid supercapacitor with AC as the negative electrode and NiMoO₄@NiMoS₄/NF as the positive electrode has an energy density of 32.75 Wh kg^-1when a power density is 725.09 W kg^-1.（2）A novel 3D MnNi₂O₄@MnNi₂S₄ core-shell nano array was successfully grown on nickel foam（NF）via in-situ growth method,which omitted the addition of binder and conductive additive and the complicated electrode preparation process.The MnNi₂O₄@MnNi₂S₄ possesses a unique nanorod@nanosheet core-shell structure,which can provide abundant active sites near the electrode interface for rapid electrochemical reaction,so the MnNi₂O₄@MnNi₂S₄ electrode materials exhibit high specific capacitance and excellent electrochemical properties.It is worth noting that the specific capacitance of the MnNi₂O₄@MnNi₂S₄ reaches 3578.57 F g^-1 at the current density of 1 A g^-1,and 1009.52 F g^-1 at the current density of 20 A g^-1.When the current density is 15 A g^-1,the specific capacitance retention rate reaches 93.1%after 5000 cycles,showing good cycling performance.Moreover,the MnNi₂O₄@MnNi₂S₄//AC asymmetric device also exihibits low leakage current and excellent self-discharge characteristics.So,the MnNi₂O₄@MnNi₂S₄ is an excellent electrode material for supercapacitors.（3）Novel CoMn₂O₄@CoMn₂S₄ core-shell nanosheets@nanoclusters are successfully grown on nickel foam（NF）via hydrothermal reaction,which omits the addition of binder and conductive additive and the complicated electrode preparation process.CoMn₂S₄ nanosheets as"shell"are uniformly distributed on the surface of CoMn₂O₄ nanoclusters as"cores"to form a typical core-shell structure,and such structures possess high specific surface area and abundant active sites,which can not only shorten the transmission path of electrons and ions,but also prevent the collapse of the structure,thus improving its cycling stability.When the current density is 1 A g^-1,the specific capacity of CoMn₂O₄@CoMn₂S₄ is 1542.0 C g^-1,and the specific capacity of CoMn₂O₄@CoMn₂S₄ is 3.1 times higher than that of CoMn₂O₄.Additionally,CoMn₂O₄@CoMn₂S₄ has excellent electrochemical cycling performance,and the specific capacity retention rate of CoMn₂O₄@CoMn₂S₄ reaches95.81%after 5000 cycles at the current density of 20 A g^-1.Moreover,the CoMn₂O₄@CoMn₂S₄//AC device shows excellent practical application capability,when the specific power is 774.98 W kg^-1,the specific energy for CoMn₂O₄@CoMn₂S₄//AC reaches 44.30 Wh kg^-1.（4）CoMn₂S₄ electrode materials with different morphologies（0D sphere,1D cuboid,2D slice,3D flower）were synthesized by simple hydrothermal/solvothermal reactions and used as battery-type electrode for hybrid supercapacitors.The particle morphology and size of the CoMn₂S₄ were controlled by adding different coordination agents and solvents.The effects of morphology and size of electrode materials on electrochemical properties were studied.When the current density is 1 A g^-1,the specific capacities of 0D CoMn₂S₄,1D CoMn₂S₄,2D CoMn₂S₄ and 3D CoMn₂S₄ is 812,1677,1783 and 1866 C g^-1,respectively.The specific capacity of 3D CoMn₂S₄ is 2.3 times that of 0D CoMn₂S₄,which is mainly attributed to the larger specific surface area,more electrochemical active sites and higher conductivity for3D CoMn₂S₄.Moreover,CoMn₂S₄ has excellent electrochemical cycling performance,and the retention rates of specific capacity for 0D CoMn₂S₄,1D CoMn₂S₄,2D CoMn₂S₄ and 3D CoMn₂S₄ reach 92.91%,94.43%,94.54%and 96.01%after 5000cycles at 10 A g^-1,respectively.When the specific powers are 775,775,768.69 and775 W kg^-1,respectively,the specific energies for 0D CoMn₂S₄//AC,1D CoMn₂S₄//AC,2D CoMn₂S₄//AC and 3D CoMn₂S₄//AC devices reach 44.30,55.05,99.72 and 100.53 Wh kg^-1.