Modification And Lithium Storage Performance Of ZnO As Anode Materials For Lithium-ion Batteries

At present,reducing the use of fossil fuels and developing new energy sources is the direction of the whole society.However,many renewable energy sources are volatile in nature,and energy reserves can solve this problem well.Lithium-ion battery is the fastest growing compared with other energy storage systems.The important role of negative electrode in lithium battery is well known.Zinc oxide has many advantages in various negative materials.Although it has lower redox potential and higher Li⁺diffusion coefficient compared with other metal oxides,its volume expansion and poor conductivity also make ZnO limited in application.This paper mainly starts with the modification theory of negative electrode material,and takes zinc oxide as the research object to modify it to overcome the problem of volume expansion and poor conductivity.The main research work is as follows:1.ZnO with different morphology was successfully prepared by simple hydrothermal method by controlling the types of soluble ion salts,and the electrochemical properties of ZnO were tested.XRD and SEM test results show that ZnO is needle like when no soluble ions are added.When Na₃C₆H₅O₇·2H₂O is added to adjust the p H value of the solution,the solution presents bath flower shape,and then changes it to Na OH,the morphology changes to flake,while when KOH is replaced,the morphology is uniform and regular.The results show that the first discharge capacity of ZnO electrode material is 1892.5m Ah g^-1,and the specific discharge capacity cycle is reduced to 125.7m Ah g^-1 after 50 cycles.The specific discharge capacity of ZnO increases to 0.2C and only 125.7m Ah g^-1.It can be seen that the electrochemical performance of ZnO is 125.7m Ah g^-1 without changing its name not very ideal.2.The spherical ZnO was modified by carbon coating.Based on the analysis of the content of carbon coating,the influence of different carbon sources on the microstructure and phase structure of ZnO,the electrochemical properties of ZnO/C electrode materials were further studied.The results showed that the spherical morphology of ZnO/C was good,the grain size was uniform,and the crystallinity and dispersion of ZnO/C were better.The electrochemical test shows that when the carbon content is 10%and citric acid is chosen as the carbon source,the first discharge specific capacity of ZnO/c electrode material at 0.1C is 1295m Ah g^-1.After 50 cycles,the discharge specific capacity is 750.2m Ah g^-1 and the capacity retention rate is 98%,which shows excellent cycle stability and ratio performance;the second step is to recover ZnO and ZIF-8 by spherical ZnO and ZIF-8 Well,it was successfully prepared ZnO@ZIF-8 The composite materials can be characterized by good crystallinity and complete crystal structure,and the grain size is uniform;ZnO@ZIF-8 The first discharge capacity of composite is 1136.3m Ah g^-1 at 0.1C ratio,and the discharge specific capacity is 412.3m Ah g^-1 after 50 cycles.3.The effects of carbonization temperature on the phase structure and morphology of ZnO were studied by using MOF as self-sacrificial template.The results show that ZnO can be prepared by high temperature carbonization method when the carbonization temperature is 650℃,and the MOF derived ZnO has standard hexagonal structure and uniform morphology rules.When the temperature changes,the morphology of ZnO changes.When used as lithium-ion battery,the first discharge specific capacity is 790.08m Ah g^-1.When the ratio increases to 2C,the specific discharge capacity is 307.65m Ah g^-1,and 417.6m Ah g^-1 after 50 cycles.Compared with other carbonization temperature at 650℃,the electrode material has better cycle stability and ratio performance.