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
LiFePO4 and carbon-doped LiFePO4were prepared by a novel solid-phase synthesis.The samples were characterized by X-ray diffraction,SEM,elemental analysis and electrochemical performances.These test results showed that...LiFePO4 and carbon-doped LiFePO4were prepared by a novel solid-phase synthesis.The samples were characterized by X-ray diffraction,SEM,elemental analysis and electrochemical performances.These test results showed that the reaction conditions favored stabilization of samples as well as offered some control of the product morphology.Carbon-doped LiFePO4 retained olivine structure and had good electrochemical performance.The results of electrochemical evaluation of the doped product showed a lithium insertion plateau around 3.5 V（vs.Li/Li+） together with the initial charge specific capacity of 159.9 mAh·g-1 at 0.1C rate and with little specific capacity decay after 20 cycle at room temperature.展开更多
以Fe SO4·7H2O、NH4H2PO4、H2O2、Li2CO3、C6H12O6和自制的氧化石墨烯（GO）为原料,分别采用原位包覆法和非原位包覆法制备了石墨烯磷酸铁锂样品：Li Fe PO4/C/G-1和Li Fe PO4/C/G-2。用X射线衍射（XRD）、扫描电镜（SEM）、透射...以Fe SO4·7H2O、NH4H2PO4、H2O2、Li2CO3、C6H12O6和自制的氧化石墨烯（GO）为原料,分别采用原位包覆法和非原位包覆法制备了石墨烯磷酸铁锂样品：Li Fe PO4/C/G-1和Li Fe PO4/C/G-2。用X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、交流阻抗（EIS）和充放电测试研究了两种包覆方法制备的样品的晶体结构、形貌和电化学性能。结果表明原位法包覆所得复合材料Li Fe PO4/C/G-1具有更优秀的电性能：在2.5～4.1 V充放电,0.1C和1C首次放电比容量分别为158.15和150.5 m Ah·g-1,在1C倍率下循环500次后容量保持率达到98.3%。展开更多
采用高温固相法合成了LiFePO_4/C和Al、Mg共掺杂的LiFe_(0.95)Al_(0.03)Mg_(0.02)PO_4/C复合材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、能量仪(EDS)、恒流充放电测试、循环伏安法(CV)等手段对材料的结构、形貌及电化学性能进行...采用高温固相法合成了LiFePO_4/C和Al、Mg共掺杂的LiFe_(0.95)Al_(0.03)Mg_(0.02)PO_4/C复合材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、能量仪(EDS)、恒流充放电测试、循环伏安法(CV)等手段对材料的结构、形貌及电化学性能进行了表征。XRD结果表明,Al、Mg共掺杂后的样品并没有破坏LiFePO_4的橄榄石结构,同时还增强了LiFePO_4结构的稳定性、提高了电子导电性和Li+扩散速度;通过SEM和EDS观测到LiFePO_4呈球形颗粒,并在复合样品中检测到有Al和Mg元素存在。分别以0.5C、1C、3C和5C倍率充放电,LiFe_(0.95)Al_(0.03)Mg_(0.02)PO_4/C的放电比容量分别为145.1、142.6、133.2和124.9 m Ah/g; 1C倍率下循环30次后仍保持99.2%的初始容量,显示出良好的循环寿命。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LiFePO4 and carbon-doped LiFePO4were prepared by a novel solid-phase synthesis.The samples were characterized by X-ray diffraction,SEM,elemental analysis and electrochemical performances.These test results showed that the reaction conditions favored stabilization of samples as well as offered some control of the product morphology.Carbon-doped LiFePO4 retained olivine structure and had good electrochemical performance.The results of electrochemical evaluation of the doped product showed a lithium insertion plateau around 3.5 V（vs.Li/Li+） together with the initial charge specific capacity of 159.9 mAh·g-1 at 0.1C rate and with little specific capacity decay after 20 cycle at room temperature.
文摘以Fe SO4·7H2O、NH4H2PO4、H2O2、Li2CO3、C6H12O6和自制的氧化石墨烯（GO）为原料,分别采用原位包覆法和非原位包覆法制备了石墨烯磷酸铁锂样品：Li Fe PO4/C/G-1和Li Fe PO4/C/G-2。用X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、交流阻抗（EIS）和充放电测试研究了两种包覆方法制备的样品的晶体结构、形貌和电化学性能。结果表明原位法包覆所得复合材料Li Fe PO4/C/G-1具有更优秀的电性能：在2.5～4.1 V充放电,0.1C和1C首次放电比容量分别为158.15和150.5 m Ah·g-1,在1C倍率下循环500次后容量保持率达到98.3%。
文摘采用高温固相法合成了LiFePO_4/C和Al、Mg共掺杂的LiFe_(0.95)Al_(0.03)Mg_(0.02)PO_4/C复合材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、能量仪(EDS)、恒流充放电测试、循环伏安法(CV)等手段对材料的结构、形貌及电化学性能进行了表征。XRD结果表明,Al、Mg共掺杂后的样品并没有破坏LiFePO_4的橄榄石结构,同时还增强了LiFePO_4结构的稳定性、提高了电子导电性和Li+扩散速度;通过SEM和EDS观测到LiFePO_4呈球形颗粒,并在复合样品中检测到有Al和Mg元素存在。分别以0.5C、1C、3C和5C倍率充放电,LiFe_(0.95)Al_(0.03)Mg_(0.02)PO_4/C的放电比容量分别为145.1、142.6、133.2和124.9 m Ah/g; 1C倍率下循环30次后仍保持99.2%的初始容量,显示出良好的循环寿命。
