| Since human beings entered the industrial age,the productivity of human society has been further developed.The use of fossil fuels in industrial production has made the non-renewable resources on the earth like fossil fuels gradually exhausted.At the same time,the deterioration of ecological environment and the global warming are caused for the burning of fossil fuels.Therefore,people are in urgent need to find renewable and clean energy to replace fossil energy.New energy resources,such as nuclear,wind,hydro,solar,and tidal energy,have been paid more and more attention by governments around the world.However,the promotion and the use of these new energy resources are inseparable from the development of energy storage technology.Therefore,energy storage power sources have increasingly become the focus of attention.Lithium-ion batteries have the advantages of light weight,high energy density,and no memory effect,so they are favored by many researchers.The anode materials of lithium-ion batteries have great influence on the overall performance of lithium-ion battery.Recently,rock salt-type LiTiO2 has attracted people's attention,but it is a semiconductor material with low conductivity.For the low conductivity electrode active material,it is a good method to modify it with metal ions doping.In this paper,iron,nickel and copper doped LiTi02 were prepared by hydrothermal method,and the phase composition,microstructure,band gap and electrochemical properties of the products were analyzed.The main research contents are as follows:(1)Using iron(?)nitrate nonahydrate[Fe(NO3)3·9H2O],anatase(TiO2)and lithium hydroxide monohydrate(LiOH·H2O)as raw materials to synthesize samples with hydrothermal method.The reaction conditions were as follows:alkali concentration was 1.8 mol/L,reaction temperature was 120?180?,titanium dioxide concentration was 0.1 mol/L,0.2 mol/L,0.4 mol/L,respectively,reaction time was 12 h.The effects of the concentration of titanium dioxide and the molar ratio of iron and titanium on the phase,crystal morphology,grain size and other properties(electrochemical performance,battery performance)of the synthesized samples are mainly studied.It is found that when the iron content is small,LiTiO2 is the only phase.When the iron content increases,LiFeTiO4 phase appears.When the titania concentration is 0.4 mol/L and the molar ratio of iron to titanium is 1.3,LiTiO2 phase disappears and principal phases are LiFeTiO4 and TiO2;Pure LiTiO2 nanoparticles have an octahedral diamond shape with good dispersibility.When the iron content increases,particle size changes and agglomeration occurs.UV-vis diffuse reflectance spectra show that the sample is a direct band gap n-type semiconductor.As the amount of iron doped increases,the band gap value gradually decreases;Magnetic properties show that the samples doped with iron have antiferromagnetism;The catalytic performance of pure LiTiO2 is better than the sample with low iron content,and the adsorption performance of the sample doped with iron is better.Electrochemical measurements revealed that the sample with Fe to Ti molar ratio of 1.3 deliveres a high initial specific capacity of 832.0 mAh/g,which is about 4 times the first discharge specific capacity of pure LiTiO2.(2)Using nickel nitrate hexahydrate[Ni(NO3)2·6H2O],anatase(TiO2)and lithium hydroxide monohydrate(LiOH·H2O)as raw materials to synthesize samples with hydrothermal method.The reaction conditions were as follows:alkali concentration was 1.8 mol/L,reaction temperature was 200?,titanium dioxide concentration was 0.4 mol/L,reaction time was 12 h.The effects of the molar ratio of nickel and titanium on the phase,crystal morphology,grain size and other properties(electrochemical performance,battery performance)of the synthesized samples are mainly studied.It is found that when the amount of nickel is low,nickel can be successfully doped into the lattice of LiTiO2 without changing the phase structure of LiTiO2.When the molar ratio of Ni to Ti increases gradually,Ni(OH)2 phase appears.By changing the alkali concentration,it is found that the alkali concentration has little effect on the phase in a small range;Compared with pure LiTiO2 nanoparticles,the particle size of the sample doped with nickel becomes smaller and the agglomeration phenomenon is obvious;UV-vis diffuse reflectance spectra show that the sample is a direct band gap n-type semiconductor.As the amount of nickel doped increases,the band gap value gradually decreases;The first discharge capacity of the samples increases with the increase of nickel content;When the amount of nickel doped is 0.05,0.1,0.2,the charge-discharge specific capacity of the sample increases slightly after 60 cycles.The sample with Ni to Ti molar ratio of 0.3 deliveres a high initial specific capacity of 432.6 mAh/g.(3)Using copper nitrate trihydrate[Cu(NO3)2·3H2O],anatase(TiO2)and lithium hydroxide monohydrate(LiOH·H2O,Sinopharm)as raw materials to synthesize samples with hydrothermal method.The reaction conditions were as follows:alkali concentration was 1.8 mol/L,reaction temperature was 200?,titanium dioxide concentration was 0.4 mol/L,reaction time was 12 h.The effects of the molar ratio of copper and titanium on the phase,crystal morphology,grain size and other properties(electrochemical performance,battery performance)of the synthesized samples are mainly studied.It is found that when the amount of copper is low,nickel can be successfully doped into the lattice of LiTiO2 without changing the phase structure of LiTiO2.When the molar ratio of Cu to Ti increases gradually,CuO phase appears.By changing the alkali concentration,it is found that the alkali concentration has little effect on the phase in a small range;Compared with pure LiTiO2 nanoparticles,the particle size of the sample doped with nickel becomes smaller and the agglomeration phenomenon is obvious.When the molar ratio of Cu to Ti is large,the particle size increases with the increase of Cu content,and octagonal flakes appear,which is the morphology of CuO;UV-vis diffuse reflectance spectra show that the sample is a direct band gap n-type semiconductor.When the molar ratio of Cu to Ti is 0.15,the first discharge capacity of the sample is the highest,and there is a discharge plateau at about 0.9 V.The results show that the sample with the molar ratio of Cu to Ti of 0.15 has the best cycle stability,and the discharge specific capacity is 66.3 mAh/g after 100 cycles.The rate performance of the sample with Cu to Ti molar ratio of 0.5 is better.When the current density is 100 mA/g,the discharge specific capacity after 10 cycles is 83.6 mAh/g. |
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