改性多壁碳纳米管导电剂对锂电池正极性能影响

The Effect of Modified Multi-walled Carbon Nanotube Conductive Agents on the Positive Electrode Performance of Lithium Batteries

实验室合成的多壁碳纳米管,经酸洗化学改性后可作锂离子电池导电剂,用于制备正极极片并组装扣式半电池。通过扫描电子显微镜观察导电剂改性后在正极浆料中的分散情况,通过红外能谱判断官能团嫁接效果,利用四探针电导率测试仪、电化学工作站及充放电循环平台测试电池正极的电化学性能。结果表明:多壁碳纳米管在化学改性后能均匀分散在正极浆料中,较改性前锂电池正极片电导率提升率约为486.30%,内部电阻值下降率约为88.96%;扣式半电池电荷转移阻抗下降率约为89.00%,电池放电容量高、循环稳定性高、波动小。经化学改性的多壁碳纳米管导电剂相较于传统导电剂具有更优异的电化学性能,导电剂纯度较高且不易团聚,在表面官能团的作用下与活性物质颗粒间有良好的界面结合力,从活性物质颗粒到导电剂再到集流体之间形成了多条电子通道,从而提升了锂离子电池正极电化学性能。

Multi-walled carbon nanotube synthesized in laboratory may be used as lithium-ion battery’s conductive agents after chemical modification by acid pickling.They are used to prepare positive electrode plates and assemble button half cells.The dispersion of modified conductive agents in the positive slurry was observed by means of electron microscope scanning.The grafting effect of functional groups was judged according to infrared energy spectrum.The electrochemical performance of the positive electrode of batteries was tested by using a four-point probe conductivity tester,electrochemical workstation and charge-discharge cycle platform.The results showed that the multi-walled carbon nanotube could be uniformly dispersed in the positive slurry after chemical modification;the conductivity of the lithium-ion battery’s positive electrode increased by about 486.30%,the internal resistance decreased by about 88.96%,and the button half cell’s charge transfer impedance decreased by about 89.00 compared with the same before modification;and the battery’s discharge capacity was high,with a high cycle stability and small fluctuation.After chemical modification,multi-walled carbon nanotube conductive agents have better electrochemical performance than traditional conductive agents.The conductive agent is of high purity and is not easy to become agglomerated.Under the action of surface functional groups,the conductive agent has a good interface bonding force with active material particles,and multiple electronic channels take shape from active material particles to conductive agents and then to current collectors.Thus,the electrochemical performance of a lithium-ion battery’s positive electrode is improved.