Modified Fabrication And Electrochemical Properties Of Hard Carbon Anode For Lithium Ion Batteries

Lithium-ion battery is an environmentally friendly,high energy density chemical power source that greatly alleviates the problems of traditional fossil energy depletion and environmental pollution caused by the use of fossil energy.Lithium-ion batteries are widely used in daily life,and people have higher requirements for the capacity and cycle performance of lithium-ion batteries.Electrode materials have an important impact on the performance of lithium-ion batteries.The development of high-capacity,high-stability electrode materials has an important impact on the performance of lithium-ion batteries.Hard carbon is a carbon-based anode material with high capacity and a long service life.However,hard carbon also has the disadvantages of low coulomb efficiency in the first cycle,which limits the promotion and use of hard carbon.In this paper,the hard carbon is modified by nitrogen doping and composite methods to obtain larger capacity and higher coulombic efficiency.A nitrogen-doped hard carbon anode material was prepared by chemical vapor deposition at a temperature of 300°C,400°C,and 500°C,respectively.When the growth temperature is 500°C,the Coulomb efficiency is 71.18%,which is higher than67.12%of untreated hard carbon.After 80 cycles,the growth temperature of 500°C nitrogen-doped hard carbon anode discharge capacity is 261.8 mAhg-1.is 35.1 mAhg^-1higher than untreated hard carbon.After 7 cycles,the untreated hard carbon and nitrogen-doped hard carbon can achieve a coulombic efficiency of about 99%.The SiO_x/HC composite anode material was prepared by mechanical mixing and heat treatment at a certain temperature.The composite powders with SiO content of 5wt.%,10 wt.%and 20 wt.%were kept at 850°C for 2 h.With the increase of SiO content,the electrochemical performance of SiOx/HC composite anode materials decreased slightly.The composite powder with SiO content of 5 wt%has better performance,the coulombic efficiency of the first circle is 70.6%,and the discharge capacity after looping for 80 cycles is 222.2 mAhg^-1.The SiOx content is kept constant.After the composite powder with SiO content of 20 wt.%is kept at 800°C,950°C and1050°C for 2 h,the Coulomb efficiency of the first circle increases first and then decreases,and the capacity increases slightly.On the whole,the electrochemical performance of the 950°C composite powder is superior,the coulombic efficiency of the first circle is 69.27%,and the discharge capacity is 201.6 mAhg^-1 after 80 cycles.The composite powder containing SiO_x 20 wt.%after 950°C incubation was further subjected to nitrogen doping treatment.The Coulomb efficiency of the nitrogen-doped SiO_x/hard carbon composite anode material with a growth temperature of 500°C remained at about 69%.The discharge capacity decreased slightly after 80 cycles.