三种方法测定电极材料的扩散系数  

Characterizing diffusion coefficient of electrode materials by three methods

作　　者：邵素霞 朱振东 王蓉蓉 彭文 SHAO Su-xia;ZHU Zhen-dong;WANG Rong-rong;PENG Wen(Hefei Gotion High-tech Power Energy Co.,Ltd.,Hefei,Anhui 230012,China)

机构地区：[1]合肥国轩高科动力能源有限公司,安徽合肥230012

出　　处：《电池》2021年第6期577-581,共5页Battery Bimonthly

基　　金：国家重点研发计划(2016YFB0100304)。

摘　　要：采用电化学阻抗谱(EIS)、恒流间歇滴定技术(GITT)和恒电位间歇滴定技术(PITT),测定锂离子电池正极LiNi_(0.65)Co_(0.15)Mn_(0.2)O_(2)及负极石墨的表观化学扩散系数D。通过dU/dQ及阻抗,研究充放电过程中材料相变对D的影响。3种方法测得的正、负极在充放电过程中的D变化趋势一致。正极的D随脱锂量的增加而增加;当过充时,D逐渐降低。负极的D随着嵌锂量的增加,出现两个最小值,整体表现为“W”形。正极LiNi_(0.65)Co_(0.15)Mn_(0.2)O_(2)的D大于负极石墨。3种方法测得的正、负极的D,数量级上存在一定差异,其中PITT测得的最大,EIS测得的最小。正极材料在充电过程中,c轴先增加、后减小,D具有相同的变化趋势;负极材料单相区的D较大,两相共存区的D较小。Electrochemical impedance spectroscopy(EIS),galvanostatic intermittent titration technique(GITT)and potentiostatic intermittent titration technique(PITT)were used to measure the apparent chemical diffusion coefficient D of LiNi_(0.65)Co_(0.15)Mn_(0.2)O_(2) cathode and graphite anode in Li-ion battery.The effects of phase transition of materials during charging and discharging on the D were studied by dU/dQ and impedance.The D of cathode and anode measured by three methods presented the similar trend during charging and discharging.The D of cathode increased with the increase of delithiation,decreased gradually when overcharged.The D of anode decreased with the increase of Li-intercalation,two minimum values were appeared,showing a“W”shape.The D of cathode LiNi_(0.65)Co_(0.15)Mn_(0.2)O_(2) was greater than that of anode graphite,the value obtained by the three methods had different orders of magnitude,in which PITT was the largest and EIS was the smallest.The c axis increased first and then decreased,the D showed the same trend.For the anode material,the D was larger in the single-phase region and smaller in the two-phase coexisting region.

关 键 词：锂离子电池 扩散系数 电化学阻抗谱(EIS) 恒流间歇滴定技术(GITT) 恒电位间歇滴定技术(PITT) 

分 类 号：TM912.9[电气工程—电力电子与电力传动]