Controlled Preparation And Electrochemical Performance Of Cobalt-based Metal-oxygen/sulfide Composite Electrode Materials

This paper focuses on the synthesis of cobalt-based metal oxide/sulphide electrode materials with high electrochemical performance,using a simple and easy-to-use synthetic route to achieve structural,morphological and component control.The application to lithium anode materials further explores the relationship between the mechanism of lithium ion embedding/detachment and the electrochemical performance of the electrode materials based on different component phases,which provides an idea for the preparation of high performance lithium anode materials.The main specific research contents and results are as follows:（1）Cobalt-oxide precursor with nanospheres was prepared by one-step hydrothermal method and loaded on GO nanosheets.The carbon layer on the surface of the spheres enhances the overall electrical conductivity and protects the structural stability of the material,avoiding the chalking of the electrode during the cycling process and improving the cycling stability.The Co₃O₄/C@r GO electrode maintains a reversible capacity of 411m Ah g^-1at a current density of 0.2 A g^-1and within a voltage range of 0.01 to 3 V after long cycles of more than 600 revolutions.In addition,a current density of 211 m Ah g^-1was shown at 2 A g^-1.Further by testing the electrochemical impedance of both electrode materials before and after the electrode had been activated.The results show that the R_ctvalues of the graphene-containing nanosheets consistently remain low during constant Li-ion charging and discharging,with or without activation,confirming that the introduction of carbon sheets provides a faster charge transfer for this material with high electrochemical kinetics,which is beneficial for enhancing the electrochemical performance of Li-ion batteries.（2）Heterostructured anode material Co S-Mo S₂@r GO supported by a reduced graphene oxide carbon skeleton structure was prepared by a sequential two-step hydrothermal method.The design of the composite heterostructure allowed for a heterogeneous interfacial electric field at the interface of the two phases of the cobalt-molybdenum bimetallic sulphide,which promoted the transfer rate of Li⁺and more active sites for lithium storage at the phase interface,which contributed to the multiplicative performance and cycling performance of this electrode material The capacity of the electrode material was enhanced to some extent,and even better electrochemical kinetic performance was achieved.At high current densities of 1 A g^-1,it can maintain a reversible specific capacity of 776 m Ah g^-1after 800 cycles.At large multipliers of 5 A g^-1,it exhibits an excellent capacity of 464 m Ah g^-1.On the other hand Cyclic voltammetric curves for five voltage sweep gradients from 0.2 to 1 m V s^-1,pseudocapacitance analysis,and diffusion coefficient calculations from impedance testing of each electrode were carried out,showing that the pseudocapacitance performance contribution,and the improved kinetics of the diffusion coefficient of the electrode material effectively confirm the good multiplicity and cycling electrochemical performance of the electrode material.Further,the study explores the electrode reaction mechanism of the electrode material,conducting in-situ XRD tests,combined with the corresponding CV curve testing techniques,to analyse the structural evolution and material phase changes during the embedding and disembedding of lithium ions during the charge and discharge process,thus providing a clearer grasp and understanding of the lithium storage mechanism of the electrode material.Therefore,this unique heterogeneous structure strategy can further develop lithium storage materials with even better performance.