Preparation And Electrochemical Properties Of Transition Metal Sulfide-based Electrode Materials

Metal sulfides,as the electrode material of supercapacitors,have high conductivity and high capacitance,but the large volume change during charge and discharge process will result in the low cycle life of supercapacitors.In view of these problems,this paper prepares high-performance supercapacitor electrode materials by constructing composite materials,selecting appropriate substrates,and rationally regulating the synthesis route.The main research contents are as follows:（1）A binder-free MnCo-S@Ni（OH）₂ arrays are synthesized on carbon cloth by electrodeposition.Due to the excellent structural design,nanosheet arrays can provide more active sites,shorter ion diffusion paths,and excellent conductivity.The specific capacitance of MnCo-S@Ni（OH）₂ arrays are 1746.1 F·g^-1 at 1 A·g^-1,which are higher than MnCo-S and Ni（OH）₂ electrodes.Meanwhile,the MnCo-S@Ni（OH）₂ arrays also exhibit excellent rate performance.In addition,the MnCo-S@Ni（OH）₂ arrays and activated carbon are constructed into asymmetric supercapacitors,which exhibit energy density of 38.5 Wh·kg^-1and power density of 811.7 W·kg^-1,implying satisfactory energy storage ability and long cycle stability.（2）Templates of carbon spheres are synthesized by glucose through the hydrothermal method.Nickel manganese sulfide is prepared on the surface of carbon spheres.The three-dimensional spherical structure can prevent the agglomeration of nickel manganese sulfide during preparation.The support structure of carbon spheres can alleviate the volume change of the electrochemical reaction process of the electrode material and improve the cycle stability of the material.In addition,the spherical structure makes the electrode material fully contact with the electrolyte.Electrochemical tests exhibit that the electrode material has specific capacitance of 1089.6 F·g^-1 at 1 A·g^-1.The asymmetric supercapacitor is constructed by the optimized electrode material obtains an energy density of 27.1 Wh·kg^-1 and a power density of 807.4 W·kg^-1,and can obtain excellent cycle performance and rate performance.（3）Cubic Cu₂O nanoparticles are synthesized by the coprecipitation method and used as precursors to synthesize rough CuCo₂S₄ particles.Meanwhile,the electrochemical performance of the product was compared with that of the product synthesized with copper salt.The results show that the CuCo₂S₄ particles synthesized with Cu₂O as precursor have larger specific capacitance(1410.5 F·g^-1),better rate performance（76%）and stronger conductivity.It is confirmed that CuCo₂S₄ synthesized with Cu₂O as the precursor avoids the agglomeration and alleviates the volume change of the electrode material.The maximum energy density of the asymmetric supercapacitor is 32.5 Wh·kg^-1.The capacitance retention rate is 90.3%after 3000 cycles at 10 A·g^-1,implying great cycling stability.