用乙炔碳作为碳源,采用机械活化辅助碳热还原两步法合成xLi_3V_2(PO_4)_3·LiVPO_4F/C复合正极材料。采用XRD、SEM、TEM等技术对样品的晶体结构和微观形貌进行了表征,采用循环伏安法和恒流充放电等测试方法对合成样品的电化学性能...用乙炔碳作为碳源,采用机械活化辅助碳热还原两步法合成xLi_3V_2(PO_4)_3·LiVPO_4F/C复合正极材料。采用XRD、SEM、TEM等技术对样品的晶体结构和微观形貌进行了表征,采用循环伏安法和恒流充放电等测试方法对合成样品的电化学性能进行分析研究。结果表明:xLi_3V_2(PO_4)_3·LiVPO_4F/C复合正极材料兼备了Li_3V_2(PO_4)_3的循环稳定性好、倍率性能佳的优点和LiVPO_4F能量密度高的优势,此外还弥补了Li_3V_2(PO_4)_3在3～4.7 V电压范围充放电时放电电压平台缺失的缺陷。该材料在3～4.7 V之间的循环稳定性较好,在1C倍率下最高放电比容量为119.7 m A·h/g,循环300圈后为97.5 m A·h/g。其倍率性能较好,在0.1C倍率下充放电可获得高达152 m A·h/g的放电比容量,倍率升高到8C时仍能保持100 mA·h/g的放电比容量。展开更多
Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indica...Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indicating high crystalline and phase purity.The SEM and TEM images reveal that diameter of the spherical-like Na2FePO4F/C particles ranges from 50 to 300 nm,and HRTEM image shows that the surface of Na2FePO4F/C composite is uniformly coated by carbon layer with a average thickness of about 3.6 nm.The carbon coating constrains the growth of the particles and effectively reduces the agglomeration of nanoparticles.Using lithium metal as anode,the composite delivers a discharge capacities of 102.8,96.4 and 90.3 mA·h/g at rates of 0.5C,1C and 2C,respectively.After 100 cycles at 0.5C,a discharge capacity of 98.9 mA·h/g is maintained with capacity retention of 96.2%.The Li+diffusion coefficient(D)of Na2FePO4F/C composite is calculated as 1.71×10^–9 cm^2/s.This study reveals that the simple solid state reaction could be a practical and effective synthetic route for the industrial production of Na2FePO4F/C material.展开更多
LiVPO_(4) F has attracted increasing research interest in the field of Li-ion batteries due to its high working voltage platform and high theoretical energy density.However,the construction of stable LiVPO_(4) F catho...LiVPO_(4) F has attracted increasing research interest in the field of Li-ion batteries due to its high working voltage platform and high theoretical energy density.However,the construction of stable LiVPO_(4) F cathode material with excellent electrochemical properties is still a major challenge.Herein,we successfully synthesized spherically shaped LiVPO_(4) F/C via a spray dryingroasting method.X-ray diffraction(XRD)and scanning electron microscopy(SEM)results indicate that the well crystallized LiVPO_(4) F/C with triclinic structure shows spherical morphology with an average diameter of 1-3μm.The spherically shaped LiVPO_(4) F/C delivers a discharge capacity of 137.9 mAh·g^(-1) at 0.1 C rate in the range of3.0-4.5 V and remains 91.4%capacity retention of its initial discharge capacity after 50 cycles.These results reveal that spray drying-roasting method is a promising approach to synthesize spherically shaped LiVPO_(4) F/C cathode material with stable crystal structure and excellent performance.展开更多
文摘用乙炔碳作为碳源,采用机械活化辅助碳热还原两步法合成xLi_3V_2(PO_4)_3·LiVPO_4F/C复合正极材料。采用XRD、SEM、TEM等技术对样品的晶体结构和微观形貌进行了表征,采用循环伏安法和恒流充放电等测试方法对合成样品的电化学性能进行分析研究。结果表明:xLi_3V_2(PO_4)_3·LiVPO_4F/C复合正极材料兼备了Li_3V_2(PO_4)_3的循环稳定性好、倍率性能佳的优点和LiVPO_4F能量密度高的优势,此外还弥补了Li_3V_2(PO_4)_3在3～4.7 V电压范围充放电时放电电压平台缺失的缺陷。该材料在3～4.7 V之间的循环稳定性较好,在1C倍率下最高放电比容量为119.7 m A·h/g,循环300圈后为97.5 m A·h/g。其倍率性能较好,在0.1C倍率下充放电可获得高达152 m A·h/g的放电比容量,倍率升高到8C时仍能保持100 mA·h/g的放电比容量。
基金Projects(51472211,51502256)supported by the National Natural Science Foundation of ChinaProjects(2016GK4005,2016GK4030)supported by the Strategic New Industry of Hunan Province,ChinaProject(13C925)supported by the Research Foundation of Education Bureau of Hunan Province,China
文摘Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indicating high crystalline and phase purity.The SEM and TEM images reveal that diameter of the spherical-like Na2FePO4F/C particles ranges from 50 to 300 nm,and HRTEM image shows that the surface of Na2FePO4F/C composite is uniformly coated by carbon layer with a average thickness of about 3.6 nm.The carbon coating constrains the growth of the particles and effectively reduces the agglomeration of nanoparticles.Using lithium metal as anode,the composite delivers a discharge capacities of 102.8,96.4 and 90.3 mA·h/g at rates of 0.5C,1C and 2C,respectively.After 100 cycles at 0.5C,a discharge capacity of 98.9 mA·h/g is maintained with capacity retention of 96.2%.The Li+diffusion coefficient(D)of Na2FePO4F/C composite is calculated as 1.71×10^–9 cm^2/s.This study reveals that the simple solid state reaction could be a practical and effective synthetic route for the industrial production of Na2FePO4F/C material.
基金financially supported by the National Natural Science Foundation of China(51774207,51774210 and 51904194)the Prospective Applied Research from the Technological Innovation Project of Key Industry of Suzhou(SYG201931)+1 种基金Natural Science Research of Jiangsu Higher Education Institutions of China(19KJB450001)Guangxi Key Laboratory of Electrochemical and Magnetochemical Functional Materials(EMFM20182202)。
文摘LiVPO_(4) F has attracted increasing research interest in the field of Li-ion batteries due to its high working voltage platform and high theoretical energy density.However,the construction of stable LiVPO_(4) F cathode material with excellent electrochemical properties is still a major challenge.Herein,we successfully synthesized spherically shaped LiVPO_(4) F/C via a spray dryingroasting method.X-ray diffraction(XRD)and scanning electron microscopy(SEM)results indicate that the well crystallized LiVPO_(4) F/C with triclinic structure shows spherical morphology with an average diameter of 1-3μm.The spherically shaped LiVPO_(4) F/C delivers a discharge capacity of 137.9 mAh·g^(-1) at 0.1 C rate in the range of3.0-4.5 V and remains 91.4%capacity retention of its initial discharge capacity after 50 cycles.These results reveal that spray drying-roasting method is a promising approach to synthesize spherically shaped LiVPO_(4) F/C cathode material with stable crystal structure and excellent performance.
