Synthesis And Lithium Storage Properties Of Transition Metal Carbonate As Anode Materials

Reform and opening up have accelerated the process of industrialization in China,while the demand for energy is also increasing rapidly.However,fossil fuels are the main energy materials used for industries.However,as a non-renewable resource,fossil fuels are inevitably depleted,and the problems caused by it need to be solved urgently.Therefore,the development and application of green energy is an issue that needs to be addressed urgently.Lithium ion battery(LIB)has been used in mobile communication and portable electronic devices widely due to its advantages of high output voltage,high energy density,low self-discharge rate and no memory effect.In order to realize the application of lithium ion battery in the field of higher energy density,new electrode materials with higher capacity,longer service life and lower cost must be developed.Transition metal carbonate(MCO3,M=Mn,Fe,Co or Ni)is a new type of high performance anode material for lithium ion batteries,its theoretical capacity anomaly is superior,however,the synthetic method is simple and the cost is low.In this project,different types of carbonates were synthesized by hydrothermal method,and their electrochemical properties were investigated.Meanwhile,their microstructure was modified by graphene to improve their electrochemical properties such as cyclic stability.The specific research is as follows.1.Fe1-xCdxCO3(x=0,0.2,0.4,0.6,0.8,1)was synthesized by hydrothermal method,and the morphological evolution of Fe1-xCdxCO3 carbonate from microspheres(x=0,0.2 and 0.4)to agglomerated nanoparticles(x=0.6 and 0.8)to nanocubes(x=1.0)was observed by characterization,and Cd doping was found to be an effective method for improving charge transport and ion diffusion of FeCO3,which is beneficial for improving the cycling stability and rate capability of FeCO3.In addition,the Fe0.8Cd0.2CO3 exhibits high capacity and good cycling stability,which is a potential electrode anode material.2.Ni(HCO3)2/CNF based on carbon nanofibers was synthesized by hydrothermal method.Ni(HCO3)2 was coated in the fiber structure in the form of nanometer sheets by the combination of Ni(HCO3)2 and carbon nanofibers,which solved the problem that Ni(HCO3)2 was agglomerated into nanoparticles.In the electrochemical performance test,Ni(HCO3)2/CNF showed excellent performance.At the current density of 200 mA g-1,Ni(HCO3)2/CNF still had the reversible capacity of 1261.1 mAh g-1 after 100 cycles.Compared with pure Ni(HCO3)2,the capacity and cycling stability of Ni(HCO3)2/CNF were significantly improved.3.The CdCO3 cubic particles were prepared by hydrothermal method.To improve its electrochemical performance,CdCO3@rGO was obtained by graphene modification,due to the high electrical conductivity,small volume change and low charge transfer resistance of the graphene modified material,the initial charge/discharge capacity of CdCO3@rGO was much higher than that of CdCO3 in the electrochemical test,after 100 cycles at 200 mA g-1,CdCO3@rGO could maintain a reversible capacity of 423.1 mAh g-1,which was better than the 142.0 mAh g-1 of original CdCO3.