Construction Of 2D Atomic Crystal Composites As Electrode Materials For Supercapacitors

As a new type of energy storage device,supercapacitors have important application prospects in hybrid electric vehicles,renewable energy applications and so on.It has attracted wide attention due to its advantages such as fast charge and discharge speed,high power density,and long cycle life.Two-dimensional materials play an important role in the research and development of electrode materials for supercapacitors due to their unique structure and excellent electrical properties.In this dissertation,two-dimensional atomic crystal materials MoS₂ and graphene were used as substrates,composite materials based on two-dimensional atomic crystals were prepared by hydrothermal and electrostatic adsorption methods.The composite materials were used as active materials of supercapacitors,and their electrochemical properties were systematically studied.The specific content is as follows:1.Using ZIF-8 as a template and starting material,ZnS with a polyhedral structure was prepared by reflow,and MoS₂ was grown on this substrate to prepare a graded ZnS@MoS₂ composite material assembled with 2D nanosheets.The electrochemical test shows that the ZnS@MoS₂ composite material has a specific capacitance of 291 F·g^-1 at a current density of 1 A·g^-1,and has good rate performance and cycle stability?87.14%after 3000cycles?.The ZnS@MoS₂ composite material prepared by this work exhibits a unique morphology and a large specific surface area,shortens the path of electron transport,facilitates the rapid transfer of electrons,and thus makes the composite material exhibit excellent electrochemical activity.2.By electrostatic interaction,the positively charged MoS₂ nanosheets and negatively charged GO nanosheets are self-assembled layer by layer,and highly dispersed Co₃O₄particle-supported layered graphene oxide/molybdenum disulfide composite?GO-MoS₂-Co₃O₄?was prepared by in-situ reduction of metal salts.When the current density is 1 A·g^-1,the specific capacitance of GO-MoS₂-Co₃O₄ is 277 F·g^-1.Using graphene as the negative electrode and GO-MoS₂-Co₃O₄ as the positive electrode,the assembled asymmetric supercapacitor has a stable potential window up to 1.65 V.A high specific capacitance of 130.3 F·g^-1 can be obtained at the current density is 1 A·g^-1,and also shows good cycle stability.3.In order to effectively increase the specific surface area of two-dimensional layered materials,it is proposed to introduce PPy as a spacer in graphene and Ni Co-LDH nanosheets.Pyrrole polymerizes in situ on the surface of graphene,and further coats the Ni Co-LDH double metal hydroxide by a hydrothermal method.The prepared sample formed a unique sandwich-type structure,which reduced the aggregation of the nanosheets.The composite material provides a specific capacitance of 2534 F·g^-1at a current density of1 A·g^-1,and a capacitance retention rate of 78%after 5000 cycles.When the power density of the prepared asymmetric supercapacitor is 698 W·kg^-1,the energy density is 41.9Wh·kg^-1,and when the power density is 8141 W·kg^-1,it remains 29.4 Wh·kg^-1,showing good application prospect.