Lithium-ion Battery Electrode Resistance Tester Device For Cylindrical Cell Electrode Analyse 

The importance of electrode resistance

Electrode resistance (conductivity) influences the basic performance of batteries, not only on the power capability (internal resistance), but also on the reliability or safety performance. Through the measurement of electrode resistance the property of electric conductive, micro-structural uniformity of electrodes can be evaluated during die electrode many&manu&cture process in advance, thus help us to research and improve the formulation of composite electrodes as well as the control parameters of mixing, coating and calenderii^; processes.

In the composite electrodes, the electric conductivity is determined by several primary factory, such as the inter&cial resistance between the coating layer and the conductive foil, the distributions of conductive agents, die intrixisic resistance of active material and the contact areas between particles.

The functions of BER multi-function electrode resistance analysis method for electrode process monitoring are listed as follows:

Comprehensively assessment of the slurry stability from the stirring, coating to the calendering process, which helps to recognize die anomaly aggregation of conductive agents in advance;

Recognition of uneven mixing on mixture silicon—carbon cathode;

Assessment of dectric conductivity offonnulas for diferent active materials;

Assessment of electric conductivity of formulas for diferent conductive agents;

Assessment of electric conductivity of the functional pre—coating lays of current collector;

Failure analysis for the electric conductive networic failure of batteries;

Analysis of contact resistance of the positive or negative electrode sur&ce after formation. 

The limitations of traditional test methods

Currently, there are several methods have been used to test the electrode resistance, such as four point probe method or multi point probe method and single point probe method. Though these traditional methods may have been maturely used in di&rent types of film industry areas, for the evaluation of the composite electrode films in lithium ion batteries, there are still several deficiencies that can not be ignored.

The four point probe film resistance test method has been wildly used in thin films industries, which use four or even more probes array to test the film resistance form film sur&ce. Its test procedure is easy and simple, and it can reveal the anisotropic resistance components of thin film by a simple equivalent circuit model fitting. However, considering its test principle and model fitting process, this mediod can only be suitable for a uniform thin film with smooth sur&ce, and the test sample should be loaded on an insulating substrate for ideal resistance fitting. Unfortunately, the electrodes ofliduum ion batteries are composite electrode with complex compositions, rough sur&ce and loadit^ on a low resistance current collector, so their four point probe test data, are often inconsistent and difficult to analyze the result by theoretical models. Increasing die probe number and using more complicate models can improve the test reliability to a certain extent, but that need more complex structures, and again the result analysis is still difficult.

The single point test method was another wildly used method in the lithium ion batteries industry, which use a fixed probe on the end of the curtent collector and a mobile probe on the surface of the electrode to directly measure the electrode resistance. This is a very simple way of electrode resistance test often carry out by a homebuilt system for difierent users, but it is still a rough empirical test method without considering the influence of press pressure, conductive path length, substrate materul and so on. As a result, the single point probe method can not provide a reliable and consistent electrode resistance data as well.

* Developed with CATL the top power battery company and Authorized exclusively for the Patent.

The TMAX’s creative solution

The BER series Battery electrode resistance analyzer uses the upper and lower plane controllable pressure probes to directly measure the electrode to obtain the overall resistance and resistivity in the thickness direction of the electrode, including the contact resistance between the probe and the coating, the coating resistance, and the contact resistance between the coating and the current collector. Current collector resistance; The BER series is the first Battery electrode resistance analyzer for the lithium battery industry .

The dual—plane controllable—pressure high—conductivity probe designed for composite electrode diaphragms and micron—level flat surface treatment ensure measurement accuracy; the high-precision resistance resolution and the attached calibration module ensure stable and reliable measurement results.

Introduction of principles

Multi-function

One — stop data collection of key parameters including pressure, film resistance, film thickness, temperature, humidity, etc.; guarantee the reliability and traceability of measurement result.

Automatic measurement

Automatic measurement of the resistance under different pressure, thickness, temperature and humidity, etc.; provide a real time data display.

Professional processing software

*Provides various resistance measurement and analysis methods, including

Single point test, continuous test,

*Fixed pressure mode, variable pressure mode (ForBER1300)

Show data curve

*Different presented modes of data analysis and statistics.

Integrated design

Complete integration of pressure control module, resistance and voltage measurement module, thickness measurement module and the chamber illuminating module

*Developed with CATL the top power battery company and Authorized exclusively for the Patent

Software

Measurement system analyze

*Part of the data comes from the partners, and the copyright belongs to the relevant parties. It can not be reproduced or used without consent.

Applications

Material evaluation

1.Correlation between powder conductivity and electrode conductivity

Results Analyze

Adjust the Ni content in the NCM material, and test the powder conductivity. It can be found that as the Ni content increases, the powder conductivity increases;

Comparing three NCM pieces with different Ni content, it can also be obtained that as the Ni content increases, the conductivity of the electrode piece increases;

Powder resistivity and electrode have the same trend!

2.Evaluate the resistivity of uncalendered electrode pieces under different compaction densities

Conditions: 5-60MPa, step 10MpPa, keep 25s

Results Analyze

♦ For graphite electrode, with the increase of compaction density, the resistivity continues to decrease. The reason is that the contact between active materials increases, and the overall conductivity of the electrode becomes better;

♦ For NCM electrode, with the compaction density increases, the resistivity of the pole piece continues to decrease. The main reason is that as the pressure increases, the contact between terminals and the active material becomes better;

Process evaluation

1.Evaluation of electrode primer technology

<a> The thicker the primer, the greater the resistance of the current collector;

<b> The thicker the primer, the greater the cathode resistance;

<c> After determining the best primer coating process based on the correlation between the two, the electrode resistance test can be used as a method for long-term monitoring of process stability.

2.Conductive agent distribution uniformity evaluation

By monitoring the change use the resistance of the battery electrode, an abnormal battery electrode can be quickly identified, to prevent the bad battery electrode from flowing into the next process, and to save production costs.

Cell evaluation

1.Analysis of electrode resistance during high temperature cycle&storage

*The resistance of the cathode continues to increase with the increase in the number of cycles, indicating that a large change has taken place on the cathode side after the high temperature cycle, which may be related to the byproducts on the surface of the cathode particles or the contact between the particles;

*The resistance of the anode membrane increases with the storage time, which indicates that the anode side has changed a lot during the storage process, which may be related to the increase of side reactions on the anode material surface

*Part of the data comes from the partners, and the copyright belongs to the relevant parties. It can not be reproduced or used without consent.

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