LiVPO4F suffers problems of difficulty in synthesis and poor conductivity. To solve these,herein sub-micro spherical LiVPO4F/C is synthesized from a highly-reactive hollow VPO4/C sphere that is derived from a facile a...LiVPO4F suffers problems of difficulty in synthesis and poor conductivity. To solve these,herein sub-micro spherical LiVPO4F/C is synthesized from a highly-reactive hollow VPO4/C sphere that is derived from a facile and fast spray pyrolysis for the first time. Uniform carbon coating layer with a thickness of 5–8 nm is observed on the surface of the particles,helping to improve the electronic conductivity,suppress the particle growth and protect the particles from corrosion by the electrolyte. The particles are shaped as fine sub-micro spheres,which are beneficial for shortening the distance for Li+ transport. Rietveld refinement for the X-ray diffraction pattern of as-prepared sample shows high-purity triclinic LiVPO4F with an enlarged lattice volume,enabling faster Li+ transport in the prepared material. Accordingly,the resulted LiVPO4F/C demonstrates superior electrochemical properties,delivering 135.4,91.1 mA hg-1 at 1,40 C respectively,and remaining the capacity of 93.3 mA hg-1 after 500 cycles at 20 C with the retention of 95.0%. The method introduced here provides an efficient way to address the serious problems of preparing high-purity Li VPO4F with good conductivity.展开更多
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
A new cathode material, LiVPO4F, has been synthesized through two steps of solid-state reactions. In the first step, vanadium pentoxide, ammonium dihydrogen phosphate, and a high surface area carbon were pre-heated at...A new cathode material, LiVPO4F, has been synthesized through two steps of solid-state reactions. In the first step, vanadium pentoxide, ammonium dihydrogen phosphate, and a high surface area carbon were pre-heated at 300 ℃ and reacted at 750 ℃ under an inert atmosphere to yield the trivalent vanadium phosphate VPO4. In the second step, the product LiVPO4F was synthesized by the reaction with VPO4 and LiF. The LiVPO4F was characterized by X-ray diffraction, scanning electron microscopy, cyclic voltammetry and charge/discharge testing measurements. The LiVPO4F is triclinic crystalline system. At 0.1 C rate, the first charge/discharge capacities were 150.1 mAh·g-1 and 132.6 mAh·g-1; At 0.2 C rate, the first charge/discharge capacities were 142.9 mAh·g-1 and 125.2 mAh·g-1. The LiVPO4F from this work has higher charge/discharge voltage 4.3 V and 4.1 V, respectively.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51704332,51874360 and 51804344)the Program of Huxiang Young Talents(Grant No.2019RS2002)the Innovation and Entrepreneurship Project of Hunan Province,China(Grant No.2018GK5026)。
文摘LiVPO4F suffers problems of difficulty in synthesis and poor conductivity. To solve these,herein sub-micro spherical LiVPO4F/C is synthesized from a highly-reactive hollow VPO4/C sphere that is derived from a facile and fast spray pyrolysis for the first time. Uniform carbon coating layer with a thickness of 5–8 nm is observed on the surface of the particles,helping to improve the electronic conductivity,suppress the particle growth and protect the particles from corrosion by the electrolyte. The particles are shaped as fine sub-micro spheres,which are beneficial for shortening the distance for Li+ transport. Rietveld refinement for the X-ray diffraction pattern of as-prepared sample shows high-purity triclinic LiVPO4F with an enlarged lattice volume,enabling faster Li+ transport in the prepared material. Accordingly,the resulted LiVPO4F/C demonstrates superior electrochemical properties,delivering 135.4,91.1 mA hg-1 at 1,40 C respectively,and remaining the capacity of 93.3 mA hg-1 after 500 cycles at 20 C with the retention of 95.0%. The method introduced here provides an efficient way to address the serious problems of preparing high-purity Li VPO4F with good conductivity.
基金Project(2011FJ1005)supported by Science and Technology Major Projects of Hunan Province,ChinaProject supported by Hunan Provincial Innovation Foundation for Postgraduate,China
基金Project (51164007) supported by the National Natural Science Foundation of ChinaProject (2011M501288) supported by China Postdoctoral Science Foundation
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。
文摘A new cathode material, LiVPO4F, has been synthesized through two steps of solid-state reactions. In the first step, vanadium pentoxide, ammonium dihydrogen phosphate, and a high surface area carbon were pre-heated at 300 ℃ and reacted at 750 ℃ under an inert atmosphere to yield the trivalent vanadium phosphate VPO4. In the second step, the product LiVPO4F was synthesized by the reaction with VPO4 and LiF. The LiVPO4F was characterized by X-ray diffraction, scanning electron microscopy, cyclic voltammetry and charge/discharge testing measurements. The LiVPO4F is triclinic crystalline system. At 0.1 C rate, the first charge/discharge capacities were 150.1 mAh·g-1 and 132.6 mAh·g-1; At 0.2 C rate, the first charge/discharge capacities were 142.9 mAh·g-1 and 125.2 mAh·g-1. The LiVPO4F from this work has higher charge/discharge voltage 4.3 V and 4.1 V, respectively.
