The Preparation Of Three-dementional Transition Metal Compound Electrode Materials For Supercapacitor

Supercapacitors,a new type of electrochemical energy storage device between secondary batteries and electrostatic capacitors,have received more attention in recent years due to their advantages in rapid charge and discharge capabilities.As the most important component of supercapacitors,electrode materials directly determine the mainly indicators of supercapacitors.Therefore,it is necessary to find some ideal electrode materials to improve the performance of supercapacitors and solve the practical application requirements.Transition metal oxygen and sulfur compounds are ideal electrode materials due to their high theoretical specific capacitance and controllable morphology.However,they are prone to volume expansion and difficult ion diffusion during the process of charge and discharge.In this paper,according to excellent performance of the transition metal oxidation and sulfide,several transition metal oxy(sulfide)composites were synthesized with different morphologies,through selecting appropriate substrate materials and optimizing reaction conditions.They all show great performance.The details contents are as follows:(1)Co₃O₄-NiO/GO composite was prepared by low-temperature calcination method.Among them,Co₃O₄ and NiO played a synergistic coupling role,which increased the electron transport capacity and improves the electrochemical properties of the materials.Electrochemical tests showed that the specific capacitance of the Co₃O₄-NiO/GO composite was 716 F·g^-1at a current density of 2 A·g^-1.And It was assembled into an asymmetric supercapacitor.The specific capacitance at 1 A·g^-1current density is 133 F·g^-1.The power density is 825 W·kg^-1 and the correspond energy density is 50.2 Wh·kg^-1.After 3000 cycles,the capacitance still maintained 82% of the initial capacitance and showed excellent cycle stability.(2)Partial hollow porous carbon spheres were obtained by pyrolysis of yeast cells at high temperature.Then NiCo₂S₄ nanosheets were grown on the surface of carbon spheres to prepare YC/NiCo₂S₄ composite electrode materials.The existence of hollow carbon spheres,on the one hand,can increase the contact area between NiCo₂S₄nanosheets and electrolyte,and increase the active sites;on the other hand,the hollow structure can reduce the internal resistance and further improve the electrochemical performance.The specific capacitance of the composite remains at 454 F·g^-1 at 10A·g^-1.After 3000 cycles,the capacitance retention rate of YC/NiCo₂S₄ still maintained at 81%.This work provided a new strategy for the use of microorganisms in electrochemical energy storage.The asymmetric supercapacitor with YC/NiCo₂S₄ as positive electrode and AC as negative electrode has a specific capacitance of95 F·g^-1at 4 A·g^-1.At the energy density of 43.7 Wh·kg^-1,the power density is 400W·kg^-1.(3)Innovatively dopamine in-situ nitrogen-doped MXenes to obtain a new type of N-doped two-dimension sheet.f-Ti₃C₂-PDA-Ni Mo S₄ was prepared by coating Ni Mo S₄beads on f-Ti₃C₂-PDA by two-step hydrothermal method.f-Ti₃C₂ has a graphene like structure with excellent conductivity and redox activity.At the same time,it also has high specific surface area and electronegativity.Ni Mo S₄ can be attached to its surface forming sandwich biscuit structure.This structure makes good use of f-Ti₃C₂,which ensures that Ni Mo S₄ can be fully utilized.What's more,the addition of dopamine not only increases the hydrophilic property,but also provides pseudo-capacitance.