杂质对高压LiCoPO_4电极电化学性能的影响(英文)

Effect of the Impurities on Electrochemical Performance of High-Voltage LiCoPO_4 Electrode

研究了高温固相法合成的高压LiCoPO4电极的电化学性能。结果表明,杂质碳和Co2P的存在使LiCoPO4电极的放电容量降低,纯橄榄石相无杂质的LiCoPO4具有最大的放电容量,达到135mAh/g。循环伏安测试结果显示,碳杂质的存在可能改变了锂脱嵌的机理。碳含量比较低时存在2个氧化峰,而碳含量比较高时只有1个氧化峰。阻抗测试结果显示,界面电容为16.9μF/cm2,表观固相质子扩散系数是(2.0～3.4)10-9m2/s。

The electrochemical performance of high-voltage LiCoPO4 electrode synthesized by high-temperature solid-state reaction was investigated. It is found that the existence of the carbon and Co2P decreases the discharge capacity; the LiCoPO4 with pure olivine phase has a maximum discharge capacity and it can reach 135 mAh/g. The cyclic voltammetric measurements have shown that the impurity of carbon and Co2P can change the Li-deintercalation reaction mechanism. There are two oxidation peaks when the impurity content is relatively low; however, there is only on oxidation peak with the larger amount of impurities in the cyclic voltammetry. The interface capacitance between the LiCoPO4 electrode and the electrolyte is about 16.9 μF/cm2 and the apparent diffusion coefficient of the lithium ion in the solid phase is （2.0～3.4）×10-9 m2/s, based on the impedance measurements.