The development of the impedance spectroscopy method to measure the particle dispersion degree in Lithium-ion battery (LIB) slurry

本文采用实验和模拟相结合的方法，对LiB料浆的介电特性进行了研究。在实验中，从阴极料浆中提取了三种料浆。同时，以不同的转速搅拌阴极浆料。在模拟中，将三种不同的模型与实验浆液进行了比较。改变了介质电导率和颗粒电导率。用圆拟合法对得到的奈奎斯特曲线进行了拟合。将圆拟合法与EEC法拟合出的特性电阻进行了比较。同时，将圆拟合法拟合出的松弛频率与实验值进行了定量比较。主要结论如下：首先，在较低的n值下，可以得到CB聚集和CB裸露LiCoO2两种粒子分散行为，而在较高n的情况下，可以得到CB路径和CB包覆的LiCoO2粒子两种粒子分散行为。炭黑路径和炭黑包覆的LiCoO2粒子分别具有较高的介质电导率和较高的粒子电导率。然而，与颗粒导电性相比，介质导电性在决定颗粒分散性方面起着重要作用，因为介质导电性与n具有相似的作用。因此，CB路径比CB包覆的LiCoO2颗粒更能控制阴极浆料的导电性。

I combined both experiment and simulation methods to clarify the dielectric characteristics of LIB slurry. In the experiment, three slurries are extracted from cathode slurry. Meanwhile, cathode slurry is stirred at different rotational speeds. In the simulation, three different models are compared with the experimental slurries. The medium conductivity and particle conductivity are changed. The obtained Nyquist plots are fitted by circle fitting method. The characteristic resistances fitted by the circle fitting method are compared with those fitted by EEC. Meanwhile, the relaxation frequencies fitted by using the circle fitting method are quantitatively compared with those of experiment. Three main conclusions are shown as follows. Firstly, two particle dispersion behaviours which are CB aggregation and CB-bare LiCoO2 particles are able to be obtained in the case of lower n, while another two particle dispersion behaviours which are CB path and CB-coated LiCoO2 particles are able to be obtained in the case of higher n. In dielectric simulation, CB aggregation and CB-bare LiCoO2 particles are verified by lower medium conductivity and lower particle conductivity. CB path and CB-coated LiCoO2 particles are verefied;ed by higher medium conductivity and higher particle conductivity, respectively. However, compared with particle conductivity, medium conductivity plays important roles in determining particle dispersion because medium conductivity has the similar functions as n. Hence, CB path dominates the conductivity of cathode slurry than CB-coated LiCoO2 particles.