The Research On Modification And Lithium Storage Performance Of Co-based Oxides Electrode Materials

Lithium ion batteries play a key role in the application of electric vehicles and portable electronic devices due to their advantages such as high energy density and light weight.However,the power density and energy density of lithium ion battery still cannot meet the growing demand of production and life,and the structure and thermal stability of current electrode materials are relatively low,which is prone to result in a series of side reactions and safety hazards.It is an effective measure to improve the stability and chemical reaction kinetics of lithium ion batteries by selecting suitable cathode and anode materials and surface modifying or structure designing.Co-based oxide is considered as a potential next generation electrode material for lithium ion battery due to its high theoretical specific capacity and ideal rate performance.In this work,surface modification and metal elements mixing design are used to prepare LiBO₂（LBO）surface modified LiNi_0.80Co_0.15Al_0.05O₂（NCA）materials and ZnCo₂O₄ octahedrons,and their electrochemical performance are studied when they are used as cathode and anode materials for lithium ion batteries,respectively.The specific research contents are divided into the following two parts:1.The surface structure rearrangement of NCA cathode is carried out by in-situ forming a solid electrolyte LBO.First,the LBO is obtained through the chemical reaction of LiOH and H₃BO₃,and then the optimal load is obtained through the gradient experiments with different coating loads.Finally,the surface structure rearrangement of electrode materials is realized through the secondary sintering.As a result,the electrochemical performance of 0.5%LBO modified NCA materials is optimized.This electrode material delivers a high reversible discharge capacity of 200.2 mA h g^-1 at 0.1 C,and exhibits excellent cycle stability with discharge capacity retaining 136.4 mAh g^-1 after 200 cycles at 2 C.This surface structure rearrangement method provides a new research perspective for the design of high-performance lithium ion batteries.2.Hollow ZnCo₂O₄ octahedron electrode material is synthesized by using Cu₂O octahedron as the template,and combining rapid and coordinated erosion method and high temperature calcining strategy.Firstly,Cu₂O template is synthesized,and then CoCl₂·6H₂O and ZnCl₂ are used as cobalt and zinc sources to synthesize（ZnCo_x）O（OH）precursor under the facilitation of Na₂S₂O₃.Then,ZnCo₂O₄ octahedron is finally obtained by calcining at high temperature.The hollow octahedron nanomaterials show excellent electrochemical performance when they are used as anode materials for lithium ion batteries.The reversible discharge specific capacity is 1025 mA h g^-1 over 200 cycles under 200 mA g^-1 current density.This method is simple,rapid and low cost.It can also be used for the preparation of other new energy hollow materials.