| Lithium-ion batteries have been successfully commercialized in various electronic products due to their advantages such as higher energy density,better cycle performance,and environmental friendliness.At present,the anode material of lithium-ion batteries on the market is mainly graphite,but its low deintercalation lithium potential forms a dendritic structure of lithium,which poses great safety risks.The volume collapse during the deintercalation of lithium ion also seriously affects the service life of batteries.Therefore,the development of new lithium-ion battery anode materials with high energy density,long cycle life,and high safety performance has become a research hotspot.Titanium dioxide as a transition metal?Ti O2?,has good structural stability,which makes it exhibit good cycle stability.In addition,the higher lithium deintercalation potential improves the safety performance of the battery,so it is considered as a potential anode material for lithium-ion batteries.However,it is constrained given its poor theoretical specific capacity(335m Ah?g-1)and low conductivity(10-7-10-9 S·cm-1).This paper mainly studies the doping of transition group elements with higher theoretical specific capacity or better conductivity in nanostructured Ti O2 anode materials,and explores the effects of doping on the morphology,phase transition and electrochemical performance of Ti O2 nanofibers.The research content is as follows:1.One-dimensional structure Ti O2 nanofibers doped with different concentrations of nickel were prepared by electrospinning method and annealing process.The effects of nickel doping on the phase transition and electrochemical performance of Ti O2 nanofibers were investigated.Phase analysis shows that as the doping content of Ni increases from 0wt.%to 4 wt.%,the content of Ni O and the ratio of the anatase phase to the rutile phase in Ti O2 first increase and then decrease.When the doping content of Ni is 3 wt.%,the Ni O and anatase content reach the maximum.The electrochemical test results show that the electrochemical performance of the 3 wt.%Ni-doped Ti O2 nanofibers also show a trend of rising first and then decreasing.The 3 wt.%Ni-doped Ti O2 anode material has the best electrochemical performance:at a current density of 100 m A?g-1,the first discharge specific capacity is 576.8 m Ah?g-1,the capacity retention rate of 3 wt.%Ni-doped Ti O2was 48%which is better than other samples after 100 cycles.In addition,as the current density increases from 40 m A?g-1 to 1000 m A?g-1,the average discharge specific capacity of the 3 wt.%Ni-doped Ti O2 is 48 m Ah?g-1 and the capacity retention rate is 22%which is also better than other samples.2.On the basis of 3 wt.%Ni-doped Ti O2 nanofibers,Ag/Ni co-doped Ti O2 nanofiber anode materials were successfully prepared by adding silver nitrate?Ag NO3?as a silver source to the precursor solution and electrospinning technology.To investigate the effect of Ag/Ni co-doping on the electrochemical performance of Ti O2 anode materials.The charge/discharge test results show that as the doping content of Ag increases,the electrochemical performance of the material continues to improve.When the 5 wt.%Ag is introduced,the electrochemical performance of the Ti O2 nanofiber anode material is the best:the coulomb efficiency of 5%Ag/Ni-Ti O2 nanofibers can reach 64.8%,which is much higher than that of 3 wt.%Ni-doped Ti O2 nanofibers?44.7%?;at a current density of 100m A?g-1,the first discharge specific capacity of 5%Ag/Ni-Ti O2 nanofibers is 402.8 m Ah?g-1,which is higher than other samples;after 100 charge/discharge cycles,the capacity retention rate of this sample is 33.6%,which is higher than that of 3 wt.%Ni-doped Ti O2nanofibers.The rate performance test results show that after 40,100,200,400,1000 and40 m A?g-1 recovery,the average capacity retention rate of 5%Ag/Ni-Ti O2 nanofibers is 76%which is much higher than that of 3 wt.%Ni-doped Ti O2 nanofibers?49.6%?.It may be attributed to the higher electrical conductivity of Ag which has played a positive role in improving the electrochemical performance of Ti O2 anode materials. |
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