导电剂对锂离子电池负极材料钛酸锂电化学性能的影响

Effect of Different Kinds of Conductive Additives on Electrochemical Character of Li_4Ti_5O_(12)

研究了乙炔黑、碳纤维和两者的混合物这3种导电剂及用量对锂离子电池负极材料钛酸锂大电流充放电性能的影响.结果表明:导电剂的种类对电极的电化学性能影响较大.粒状乙炔黑表面积丰富但不利于导电网络的形成,电极的极化严重;线性导电剂碳纤维具有较好的导电性和较高的长径比,但与活性物质接触面积小;线性导电剂碳纤维与粒状导电剂乙炔黑相配合,在电极中不但能够形成良好的导电网络,还与活性物质具有较大接触面积,减轻了电极的极化,提高了锂离子二次电池的大电流充放电性能.

The effect of three kinds of conductive additives,namely,carbon black,chemical vapor deposit carbon fibers and the mixture of the above two carbon material,on the Li4Ti5O12 cathode,were investigated in this paper.The results indicated that the kind of conductive additives plays an important role in the electrochemical behavior of the Li4Ti5O12 cathode.Spherical carbon black prevents the formation of conductive network and therefore leads to a serious polarization.In contrast,wire-like conductive additives exhibit better electron-transfer ability,but contacting areas with the active materials is low.Adopting the mixture of the carbon black and the carbon fibers as the conductive additives,it forms better conductive network and is larger contacting area in the cathode,and hence alleviates the degree of cathode polarization.Therefore large capacity and high cycle efficiency can be kept at high charge rate.The content of conductive additive also has an influence on the high charge/discharge rate performance.