充放电过程液相锂离子浓度变化及机理

doi:10.19799/j.cnki.2095-4239.2021.0001

摘要/Abstract

摘要：

采用三电极电池实时监测不同倍率充放电过程中全电池、正极对锂、负极对锂以及浓差电池电压变化，得到不同倍率下充放电过程中正负极之间液相锂离子浓度变化规律，与此同时还研究了不同层数隔膜三电极电池正负极之间液相锂离子浓度的变化趋势。本工作通过恒电流间歇滴定法(GITT)测试了三电极电池中正极Li(Ni_0.65Co_0.2Mn_0.15)O₂(NCM65)电极表观化学扩散系数和负极石墨电极表观化学扩散系数。结果表明，充放电过程中正负极之间液相锂离子浓度变化与负极对锂电位有关，且充电过程正负极之间液相锂离子浓度大于放电过程正负极之间液相锂离子浓度。充电过程中，倍率越大，正负极之间液相锂离子浓度越大，放电过程则相反。通过增加正负极之间隔膜层数以此增加扩散路径，隔膜层数增加正负极之间液相锂离子浓度有所降低，总体锂离子浓度变化趋势保持不变，但靠近正负极侧液相锂离子浓度有一定差异。GITT测试正极NCM65电极表观化学扩散系数(3.57×10^-9～5.63×10^-8cm²/s)大于负极石墨电极表观化学扩散系数(1.16×10^-10～8.21×10^-8cm²/s)，且负极石墨表观化学扩散系数的变化趋势也与负极对锂电位有关，因此得出正极脱嵌锂速度大于负极，液相锂离子浓度变化受负极扩散的影响。

关键词: 锂离子电池, 液相锂离子浓度, 浓差电池, 三电极电池, 扩散系数

Abstract:

The change of concentration of lithium-ion in the liquid phase between the cathode and anode was monitored through the potential of battery, cathode, and anode with different charge and discharge rates using a three-electrode battery in this article. The trend of concentration variation of lithium-ion in liquid phase between the cathode and anode was also investigated using a three-electrode battery with different layers separator. The apparent chemical diffusion coefficient of the cathode and anode in a three-electrode battery was tested by GITT. The results are as follows: the concentration change of lithium-ion in the liquid phase between the cathode and anode during charging and discharging is related to the potential of an anode (vs. Li), and the concentration of lithium-ion in the liquid phase between the cathode and anode during charging is larger than the discharging. During charging, the higher the rate, the larger the concentration of lithium-ion in the liquid phase between the cathode and anode, and the opposite for discharging. Increasing the diffusion path by increasing the number of separator layers between the cathode and anode, the concentration of lithium-ion in the liquid phase between the cathode and anode decreases with the increase in layers, and the changing trend of the concentration of lithium-ion in the liquid phase remains unchanged. However, the concentration of lithium-ion in the liquid phase near the side of the cathode and anode is still different. The apparent chemical diffusion coefficient of lithium-ion in cathode (3.57×10^-9～5.63×10^-8cm²·s^-1) is greater than that in the anode (1.16×10^-10～8.21×10^-8cm²·s^-1). The trend of the diffusion coefficient of lithium-ion in an anode is related to the potential of an anode (vs. Li). The results showed that the deintercalation rate of lithium-ion in cathode is faster than that in anode, and the concentration change of lithium-ion in the liquid phase between the cathode and anode was controlled by the anode.

Key words: lithium-ion battery, liquid phase lithium ion concentration, concentration battery, three-electrode battery, diffusion coefficient

中图分类号:

TM 912.9

邵素霞, 朱振东, 彭文, 代娟, 吴浩. 充放电过程液相锂离子浓度变化及机理[J]. 储能科学与技术, 2021, 10(3): 1187-1195.

Suxia SHAO, Zhendong ZHU, Wen PENG, Juan DAI, Hao WU. Variation and mechanism of lithium-ion concentration in the liquid phase during charging and discharging cycles[J]. Energy Storage Science and Technology, 2021, 10(3): 1187-1195.

图/表 6

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浓差电池	浓度C_high/mol·L^-1	Inc_high	电压/V	dU/dInc_high
Li(1 mol/L LiPF₆)\|\|(1.00 mol/L LiPF₆)Li	1.00	0	0	0.0904
Li(1 mol/L LiPF₆)\|\|(1.25 mol/L LiPF₆)Li	1.25	0.223144	0.016
Li(1 mol/L LiPF₆)\|\|(1.50 mol/L LiPF₆)Li	1.50	0.405465	0.032
Li(1 mol/L LiPF₆)\|\|(1.75 mol/L LiPF₆)Li	1.75	0.559616	0.049
Li(1 mol/L LiPF₆)\|\|(2.00 mol/L LiPF₆)Li	2.00	0.693147	0.062

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