Carbon coated LiFePO4 cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances o...Carbon coated LiFePO4 cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances of the material as cathode in lithium-ion battery were investigated at medium and elevated temperature (30 and 55 ℃) by galvanostatic charge-discharge and A.C. impedance tests. The results show that carbon coated LiFePO4 powder exhibits a well-crystallized olivine structure and spherical morphology with an average particle size of about 500 nm. Galvanostatic charge-discharge tests show that the reversible discharge capacity at 1 C and 1.5 C rates was improved from 121 and 105 mAh·g-1 at 30 ℃ to 136 and 123 mAh·g-1 at 55℃, respectively, while the enhancement of high temperature on electrochemical performance is less obvious at a rate lower than 0.5 C. Impedance spectra analyses indicate that the cathode material has a remarkably higher lithium-ion diffusivity at 55 ℃ than that at 30 ℃, which improves the electrochemical performance at high temperature.展开更多
采用氧化物前驱体对磷酸铁锂(LiFePO4)进行少量金属离子掺杂,并用XRD ,SEM 和恒电流充放电对掺杂的LiFePO4 进行了研究。结果表明,少量的掺杂离子在很大程度上提高了LiFePO4 的电化学性能,特别是大电流放电性能。1.0 m ol% 的Nb5+掺杂Li...采用氧化物前驱体对磷酸铁锂(LiFePO4)进行少量金属离子掺杂,并用XRD ,SEM 和恒电流充放电对掺杂的LiFePO4 进行了研究。结果表明,少量的掺杂离子在很大程度上提高了LiFePO4 的电化学性能,特别是大电流放电性能。1.0 m ol% 的Nb5+掺杂LiFePO4 的0.1 C 放电容量约150 m Ah·g-1;即使在3 C 倍率下放电,也有117 m Ah·g-1 的容量。掺杂的效果与掺杂离子的半径、价态密切相关,半径小、价态高的离子对提高LiFePO4 的电化学性能有利。在掺杂量较小时(<2.0 m ol% ),掺杂效果与掺杂离子的浓度关系不大。展开更多
Cathode material LiFePO4 of lithium-ion battery was synthesized by microwave heating. The "carbon-included" LiFePO4 with improved conductivity was synthesized by the addition of graphite. And the influence o...Cathode material LiFePO4 of lithium-ion battery was synthesized by microwave heating. The "carbon-included" LiFePO4 with improved conductivity was synthesized by the addition of graphite. And the influence of microwave-heating time on structure, morphology and charge/discharge performance of the products was discussed. The results of XRD, SEM, XPS, CV and charge/discharge testing measurements showed that the LiFePO4 product after 9 min in microwave oven had more advantages than other products.展开更多
Pure olive-type phased LiFePO4 powders were successfully synthesized b y hydrothermal processes. The samples were investigated by X-ray diffraction, sc anning electron microscopy and so on. Results showed that hydroth...Pure olive-type phased LiFePO4 powders were successfully synthesized b y hydrothermal processes. The samples were investigated by X-ray diffraction, sc anning electron microscopy and so on. Results showed that hydrothermal product w ere of pure olive-type phase with a relatively smaller particle size and regular er morphology compared with the products prepared by solid-state reaction and ba ll milling activation approaches. Charge/discharge curves at 0.5 C rate revealed that the hydrothermal products had a first discharge capacity of 124 mAh·g-1, and the capacity fading rate was only 10.7% after 50 cycles.展开更多
文摘Carbon coated LiFePO4 cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances of the material as cathode in lithium-ion battery were investigated at medium and elevated temperature (30 and 55 ℃) by galvanostatic charge-discharge and A.C. impedance tests. The results show that carbon coated LiFePO4 powder exhibits a well-crystallized olivine structure and spherical morphology with an average particle size of about 500 nm. Galvanostatic charge-discharge tests show that the reversible discharge capacity at 1 C and 1.5 C rates was improved from 121 and 105 mAh·g-1 at 30 ℃ to 136 and 123 mAh·g-1 at 55℃, respectively, while the enhancement of high temperature on electrochemical performance is less obvious at a rate lower than 0.5 C. Impedance spectra analyses indicate that the cathode material has a remarkably higher lithium-ion diffusivity at 55 ℃ than that at 30 ℃, which improves the electrochemical performance at high temperature.
文摘采用氧化物前驱体对磷酸铁锂(LiFePO4)进行少量金属离子掺杂,并用XRD ,SEM 和恒电流充放电对掺杂的LiFePO4 进行了研究。结果表明,少量的掺杂离子在很大程度上提高了LiFePO4 的电化学性能,特别是大电流放电性能。1.0 m ol% 的Nb5+掺杂LiFePO4 的0.1 C 放电容量约150 m Ah·g-1;即使在3 C 倍率下放电,也有117 m Ah·g-1 的容量。掺杂的效果与掺杂离子的半径、价态密切相关,半径小、价态高的离子对提高LiFePO4 的电化学性能有利。在掺杂量较小时(<2.0 m ol% ),掺杂效果与掺杂离子的浓度关系不大。
文摘Cathode material LiFePO4 of lithium-ion battery was synthesized by microwave heating. The "carbon-included" LiFePO4 with improved conductivity was synthesized by the addition of graphite. And the influence of microwave-heating time on structure, morphology and charge/discharge performance of the products was discussed. The results of XRD, SEM, XPS, CV and charge/discharge testing measurements showed that the LiFePO4 product after 9 min in microwave oven had more advantages than other products.
文摘Pure olive-type phased LiFePO4 powders were successfully synthesized b y hydrothermal processes. The samples were investigated by X-ray diffraction, sc anning electron microscopy and so on. Results showed that hydrothermal product w ere of pure olive-type phase with a relatively smaller particle size and regular er morphology compared with the products prepared by solid-state reaction and ba ll milling activation approaches. Charge/discharge curves at 0.5 C rate revealed that the hydrothermal products had a first discharge capacity of 124 mAh·g-1, and the capacity fading rate was only 10.7% after 50 cycles.
