【摘要】 采用溶胶-凝胶法制备锂离子电池正极材料Li₃V₂（PO₄）₃/C.通过恒电流充放电测试、循环伏安（CV）、电化学阻抗谱（EIS）等方法,研究了Li₃V₂（PO₄）₃/C在不同电压区间的电化学行为（3.0-4.5 V和3.0-4.8 V）.结果表明,3.0-4.8 V电压区间的循环性能和倍率性能均不及3.0-4.5 V电压区间的.3.0-4.5 V区间0.1C(1C=150m A·g^-1)倍率首次放电比容量为127.0 mAh·g^-1,循环50次后容量保持率为99.5%,而3.0-4.8 V区间的分别为168.2 mAh·g^-1和78.5%.经过高倍率测试后再回到0.1C倍率充放电,3.0-4.5 V和3.0-4.8 V的放电比容量分别为初始0.1C倍率的99.0%和80.7%.经过3.0-4.8 V电压区间测试后,少部分第三个锂离子能够在低于4.5V的电压脱出,使3.0-4.5 V电压区间的放电比容量提升了7.4%.CV结果表明3.0-4.8 V区间的容量损失主要表现为第一个锂离子的不可逆损失.极片的X射线衍射（XRD）和X射线光电子能谱（XPS）分析测试结果表明经过3.0-4.8 V测试后,Li₃V₂（PO₄）₃的结构发生了轻微的改变.电感耦合等离子体（ICP）测试结果表明循环后的电解液中含有少量的V.结构变形和V溶解可能是Li₃V₂（PO₄）₃在3.0-4.8 V区间容量衰减的主要原因.更多还原

【Abstract】 Li₃V₂（PO₄）₃/C cathode material was synthesized by the sol- gel method. The electrochemical properties of the sample in different voltage ranges（3.0- 4.5 V and 3.0- 4.8 V） were investigated by galvanostatic charge/discharge tests, cyclic voltammetry（CV）, and electrochemical impedance spectroscopy（EIS）. Results show that the cycling performance and rate capability of Li₃V₂（PO₄）₃/C in voltage range of 3.0-4.8 V are worse than those in voltage range of 3.0-4.5 V. The initial specific discharge capacity in voltage range of 3.0-4.5 V at 0.1C rate(1C=150 mA·g^-1) is 127.0 mAh·g^-1, and 99.5% of the initial capacity was maintained after 50 cycles in contrast to 168.2 mAh·g^-1and 78.5% in voltage range of 3.0-4.8 V. The discharge capacities in voltage ranges of 3.0-4.5 V and 3.0-4.8 V are 99.0% and 80.7% of the initial 0.1C rate respectively when the charge/discharge rate recovered to 0.1C rate after the high rate test. Part of the third lithium ion may be extracted at less than 4.5 V after several cycles in voltage range of 3.0-4.8 V with a capacity increase of 7.4%.CV results indicate that the irreversible capacity fading between 3.0 and 4.8 V may be attributed to irreversible behavior of the first lithium ion. X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS） results show that the structure of Li₃V₂（PO₄）₃changes slightly after operating between 3.0 and 4.8 V. Inductively coupled plasma（ICP） results indicate the presence of dissolved V in the cycled electrolytes. The structural distortion and the V dissolved in the electrolyte may be the main reasons for the decrease in capacity.更多还原