摘要
锂/氟化碳电池具有能量密度高(2190 Wh kg~(-1))、使用温度范围宽、工作电压平稳、储存寿命长和自放电率低等优点,但在大电流放电时存在电压滞后等问题~([1-2]),放电初期的功率特性待提高。本文以石墨烯和多壁碳纳米管的复合NMP浆料(G-MWCNTs=20:80)作为导电添加剂制备锂/氟化碳电池。实验结果表明,添加10 wt%G-MWCNTs的电池,在2C放电时CFx比容量可达657 mAh·g~(-1),相比于(5%石墨+5%Super P)导电剂的电池克容量提高了11.9%,初始电压提高了0.23 V。Li/CFx电池的放电容量随G-MWCNTs的添加量增加而增加,添加量5wt%、8wt%和10wt%时1C放电克容量分别为592、693和731 mAh·g~(-1),而5wt%即可改善初始电压"滞后"。EIS测试表明,G-MWCNTs的加入可以明显提高锂离子扩散速率。SEM表明,石墨烯和碳纳米管覆均匀盖在氟化碳颗粒表面,形成纵横交错的复合导电网络,扩大了相间的导电接触面积,增强了正极的电子导电性,从而改善Li/CFx放电初期的电压"滞后"现象。
The electrochemical performances of fluorinated graphite have been improved by using graphene and multi-walled carbon nanotubes composite(G-MWCNTs,wt%,20:80) in N,N-dimethyl formamide(NMP) slurry as conductive in lithium battery.The fluorinated graphite electrode delivered a specific capacity of 657 mAh·g~(-1) at 2C with 10wt%G-MWCNTs conductive,where capacity of the battery was increased by 11.9%compared with graphite and super P(wt%,5:5) hybrid conductive.Furthermore,the initial voltage plateau was increased by 0.23 V indicating that less polarity of electrode by using G-MWCNTs composite conductive.Electrochemical Impedance Spectroscopy(EIS) tests indicated that Li~+ diffusion rate can be significantly improved by adding G-MWCNTs.The SEM result show that the carbon fluoride particles were coated by G-MWCNTs,forming a cross composite conductive network,which increasing the conductivity of positive electrode with excellent the interphase contact and modified the voltage "delay" phenomenon of Li/CFx at initial discharge.
引文
[1]Reddy,M.A.;Breitung,B.;Fichtner,M.ACS Appl Mater Interfaces 2013,5(21):11207-11211.
[2]Ahmad,Y.;Disa,E.;Guerin,K.;et al.J Fluorine Chem 2014,168:163-172.
