Preparation And Properties Of Anode Materials For Lithium Ion Batteries

Lithium ion batteries have been widely used in portable electronic devices owing to their high energy density,long cycle life and environment friendly performance.However,the lower theoretical specific capacity?372mAh/g?of the commercialized graphite negative materials has been unable to meet the increasing demand for energy,especially in the electric vehicle fields.Therefore,many researches have concentrated on the developing of the novel anode materials.The electrochemical properties of porous nanosilicon anode materials and transition metal carbonate materials were studied in this paper.Porous nanosilicon materials were prepared through the magnesiothermic reduction,and porous nanosilicon/carbon composites were obtained by wrapping carbon with bituminous powder as carbon source.At the same time,the optimum preparation process of transition metal carbonate was studied by hydrothermal synthesis.The electrochemical performance of the novel anode material for lithium ion batteries was also explored in the experiment.The porous nanosilicon/carbon composite material is a circular particle,and the particle size is about 200nm.The composite material has a mesoporous structure,the pore size is 3.733nm,and the specific surface area of the particles reaches 77.114m²/g.The larger specific surface area and internal pore structure can effectively alleviate the volume expansion effect during the charging/discharging cycling process.This material shows a good electrochemical performance.Under the current density of200mA/g,the discharge specific capacity of this material can up to 1848.6mAh/g in the first cycle,the relevant charge specific capacity is 1411.5mAh/g,and the reversible specific capacity of the material can still be maintained at 915mAh/g after100 cycles,which shows a good charging and discharging performance.The transition metal carbonate Fe CO₃,which was prepared by hydrothermal method,is a circular particle.The surface is composed of many microlayer structures.After adding surfactants or doped graphene,the material has the same shape,the morphology is uniform but the component of the particle changed from lamellar to triangulation.After adding the surfactant of sodium lauryl sulfate?SDS?,the initial discharge specific capacity of the FeCO₃ is 1067.6mAh/g at the current density of200mA/g,the charge specific capacity is 950.5mAh/g,after 50 cycles,the reversible specific capacity of the material can still be stabled at 771.8mAh/g.This material shows a good electrochemical performance.On the basis of the Fe CO₃ samples,Fe_0.6Co_0.2Mn_0.2CO₃ samples were prepared by hydrothermal synthesis.The sample has a similar morphology with FeCO₃,all of which are circular particles,and the surface of the particles is composed of many triangular microstructures.This material shows a high discharge specific capacity?973.7mAh/g?and the charge specific capacity is 674.2mA/g under the current density of 200m A/g,the reversible specific capacity of the sample can still up to711.2mAh/g after 50 cycles.This multielement transition metal carbonate can show a good electrochemical performance.