Lithium cobalt oxide （LiCoO2） was synthesized by carbon combustion synthesis （CCS） using carbon as fuel. X-ray diffraction （XRD） and scanning electron microscope （SEM） measurements showed that carbon combustio...Lithium cobalt oxide （LiCoO2） was synthesized by carbon combustion synthesis （CCS） using carbon as fuel. X-ray diffraction （XRD） and scanning electron microscope （SEM） measurements showed that carbon combustion led to the formation of layered structure of LiCoO2 and the particle size could be controlled by carbon content. For the LiCoO2 sample prepared at 800℃ for 2 h, at molar ratio of C/Co = 0.5, the particle-size distribution fell in the narrow range of 3-5 μm. Electrochemical tests indicated this LiCoO2 sample delivered an initial discharge capacity of 148 mAh/g with capacity retention rate higher than 97% after 10 cycles.展开更多
LiNi0.5Mn1.5O4 was synthesized by combustion synthesis （UCS） using urea as fuel. X-ray diffraction and scanning electron microscope measurements showed that the spinel structure LiNio.sMnl.504 with the space group F...LiNi0.5Mn1.5O4 was synthesized by combustion synthesis （UCS） using urea as fuel. X-ray diffraction and scanning electron microscope measurements showed that the spinel structure LiNio.sMnl.504 with the space group Fd3m was formed during urea combustion. Both structure and particle size could be adjusted by the amount of urea and the heat treatment temperature used in the UCS. For the LiNi0.5Mn1.5O4 sample prepared with a urea/Li molar ratio of 0.57 and a heat treatment temperature of 900℃, the particle-size distribution fell in a narrow range of 1-2 Dm. Electrochemical tests indicated that this LiNi0.sMnl.504 sample delivered a discharge capacity of 133.6 mAh/g with a capacity retention rate of 99.6% after 20 cycles at 0.5 C.展开更多
Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is p...Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances.However,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2.The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,respectively.Furthermore,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode.The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,respectively.Room-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.展开更多
Li4Ti5O12 was synthesized by a facile gel-combustion method（GCM） with polyvinylpyrrolidone（PVP） as the polymer chelating agent and fuel.The structural and electrochemical properties of the sample were compared wit...Li4Ti5O12 was synthesized by a facile gel-combustion method（GCM） with polyvinylpyrrolidone（PVP） as the polymer chelating agent and fuel.The structural and electrochemical properties of the sample were compared with the one prepared by the conventional solid-state reaction（SSR） through X-ray diffraction（XRD）,scanning electron microscopy（SEM）,cyclic voltammetry（CV）,charge-discharge measurements,and electrochemical impedance spectroscopy（EIS）,respectively.The sub-microscale Li4Ti5O12 oxides,with a high phase purity and good stoichiometry,can be obtained by annealing at 800℃.The grain size is smaller than that of the samples that were power prepared by SSR.Lithium-ion batteries with a GCM Li4Ti5O12 anode exhibit excellent reversible capacities of 167.6,160.7,152.9,and 144.2 mAh/g,at the current densities of 0.5 C,1 C,3 C and 5 C,respectively.The excellent cycling and rate performance can be attributed to the smaller particle size,lower charge-transfer resistance and larger lithium ion diffusion coefficient.It is therefore concluded that GCM Li4Ti5O12 is a promising candidate for applications in highrate lithium ion batteries.展开更多
基金The authors appreciate the financial support of Natural Science Foundation of Guangxi （No. 0731010）.
文摘Lithium cobalt oxide （LiCoO2） was synthesized by carbon combustion synthesis （CCS） using carbon as fuel. X-ray diffraction （XRD） and scanning electron microscope （SEM） measurements showed that carbon combustion led to the formation of layered structure of LiCoO2 and the particle size could be controlled by carbon content. For the LiCoO2 sample prepared at 800℃ for 2 h, at molar ratio of C/Co = 0.5, the particle-size distribution fell in the narrow range of 3-5 μm. Electrochemical tests indicated this LiCoO2 sample delivered an initial discharge capacity of 148 mAh/g with capacity retention rate higher than 97% after 10 cycles.
基金the financial support of the Natural Science Foundation of Guangxi,China (No. 0731010,2011GXNSFA018015)the Cooperative Network of Large-scale Instrument of Guangxi,China (No. 701-2008-114)
文摘LiNi0.5Mn1.5O4 was synthesized by combustion synthesis （UCS） using urea as fuel. X-ray diffraction and scanning electron microscope measurements showed that the spinel structure LiNio.sMnl.504 with the space group Fd3m was formed during urea combustion. Both structure and particle size could be adjusted by the amount of urea and the heat treatment temperature used in the UCS. For the LiNi0.5Mn1.5O4 sample prepared with a urea/Li molar ratio of 0.57 and a heat treatment temperature of 900℃, the particle-size distribution fell in a narrow range of 1-2 Dm. Electrochemical tests indicated that this LiNi0.sMnl.504 sample delivered a discharge capacity of 133.6 mAh/g with a capacity retention rate of 99.6% after 20 cycles at 0.5 C.
基金Science and Engineering Research Board,India,for the Ramanujan Fellowship(Ref:SB/S2/RJN-100/2014)Department of Science and Technology,India,for the financial support(Ref:DST/TMD/MES/2k17/11)BG acknowledges Amrita Vishwa Vidyapeetham for the fellowship
文摘Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances.However,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2.The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,respectively.Furthermore,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode.The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,respectively.Room-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.
基金supported by the National Natural Science Foundation of China(No.51374056)the support program for hundreds of outstanding innovative talents in Higher Education Institutions of Hebei Province(Ⅱ)(No.BR2-127)+2 种基金Natural Science Foundation of Hebei Province(No.E2013501135)program for New Century Excellent Talents in University(No.NCET-10-0304)The Special Fund for Basic Scientific Research of Central Colleges, Northeastern University(Nos.N100123003 and N120523001)
文摘Li4Ti5O12 was synthesized by a facile gel-combustion method（GCM） with polyvinylpyrrolidone（PVP） as the polymer chelating agent and fuel.The structural and electrochemical properties of the sample were compared with the one prepared by the conventional solid-state reaction（SSR） through X-ray diffraction（XRD）,scanning electron microscopy（SEM）,cyclic voltammetry（CV）,charge-discharge measurements,and electrochemical impedance spectroscopy（EIS）,respectively.The sub-microscale Li4Ti5O12 oxides,with a high phase purity and good stoichiometry,can be obtained by annealing at 800℃.The grain size is smaller than that of the samples that were power prepared by SSR.Lithium-ion batteries with a GCM Li4Ti5O12 anode exhibit excellent reversible capacities of 167.6,160.7,152.9,and 144.2 mAh/g,at the current densities of 0.5 C,1 C,3 C and 5 C,respectively.The excellent cycling and rate performance can be attributed to the smaller particle size,lower charge-transfer resistance and larger lithium ion diffusion coefficient.It is therefore concluded that GCM Li4Ti5O12 is a promising candidate for applications in highrate lithium ion batteries.
文摘以醋酸锂和醋酸锰为原料,浓硝酸为辅助氧化剂,在温度600℃、时间3 h下采用无焰燃烧合成尖晶石型Li Mn2O4锂离子电池正极材料,研究了不同浓度硝酸对制备尖晶石型Li Mn2O4的影响.通过XRD和SEM分别研究了产物的物相组成及微观形貌;通过电性能测试研究了产物的比容量变化.实验结果表明,当n(Li)∶n(Mn)=1∶2(mol/mol)时,可得到Li Mn2O4单相,硝酸浓度对燃烧产物颗粒影响也较大;硝酸浓度为15 mol/L时产物初始放电比容量为112.1 m Ah/g,40次充放电循环后,放电比容量为99.0 m Ah/g,容量保持率为88.3%,具有较好的容量及存储性能.
