材料期刊网

采用一种较为实用的调浆方法,考察了碳纳米管与乙炔黑的复合物(CNTs/AB)导电剂、乙炔黑(AB)导电剂和碳纳米管(CNTs)导电剂对Li_4Ti_5O_(12)电化学性能的影响,并用恒流充放电、扫描电子显微镜(SEM)和交流阻抗(AC)对添加上述3种导电剂制备得到的电极片进行研究.结果表明,采用该调浆流程能够克服CNTs在使用时出现的团聚问题,CNTs/AB复合物在改善Li_4Ti_5O_(12)电化学性能尤其在容量发挥和倍率性能方面比单一AB和CNTs具有明显优势.CNTs/AB复合物中两者的质量百分比为1:2～1:1时,0.5C时,Li_4Ti_5O_(12)电极的首次放电容量可高达157.0mAh/g,10.0C时,其放电容量可达到128.3mAh/g.与单一导电剂AB和CNTs相比,CNTs与AB复合使用时,由于CNTs的高长径比和良好导电性能使之能够起到"桥梁"作用把部分没有与活性物质充分接触的颗粒状导电剂AB与活性物质连接起来,因此两者的有机结合提高了CNTs/AB与活性材料的接触面积,使电极片能够形成有效的导电网络,有利于Li_4Ti_5O_(12)导电性能的提高.

A practical method of preparation of electrode paste mixture was adopted to evaluated the carbon nanotubes/acetylene black (CNTs/AB) composite,acetylene black (AB) and carbon nanotubes (CNTs) as conductive additives impacting on the electrochemical performance of Li_4Ti_5O_(12) electrode. The obtained Li_4Ti_5O_(12) electrodes were characterized by constant current charge and discharge tests, scanning electron microscopy (SEM) and AC impedance (AC). The results indicate that the adopted method of preparation of electrode paste mixture could make the CNTs have an effectively good dispersion,and the Li_4Ti_5O_(12) electrode with CNTs/AB composite as conductive additive manifested relatively better electrochemical performance,and in particular,high discharge capacity and rate capability than single AB and CNTs. When the weight ratio of CNTs and AB in the CNTs/AB composite was between 1:2 and 1:l,at 0. 5C,the first discharge capacity of the Li_4Ti_5O_(12) electrode was 157 mAh/g,even at 10. 0C,the discharge capacity can reach 128. 3mAh/g. Compared with single conductive additive of AB and CNTs,the CNTs/AB composite can make the Li_4Ti_5O_(12) electrode form more validity of its conductive networks that are preferable to the electronic transfer. The reason is that nano-size AB particles that group around Li_4Ti_5O_(12) particles often make no actual contact with the Li_4Ti_5O_(12) particles,but the CNTs act like bridges that can connect them,so,the CNTs/AB composite has bigger contact area with Li_4Ti_5O_(12) particles than single AB and CNTs, which make Li_4Ti_5O_(12) electrode form valid conductive networks and improve the electronic conductivity of Li_4Ti_5O_(12).