Film resistors are widely used in many applications, especially in battery equipment. It can effectively improve the efficiency of battery usage and can provide feedback battery data in the battery management system. Often, based on the value of the film resistance, the true conductivity of the material can be calculated by linear fitting, providing technical support for product development. When testing resistors in batteries, sampling two-probe and four-probe test methods are the most common and frequently used. These two methods have their own characteristics.

Thin Film Resistor Two-Probe Test Method

When using the two-probe method to test film resistors, the test loading pressure will have a certain effect on the results. In general, as the test loading pressure increases, the electrode film resistance will decrease, but after reaching a certain value, the test results are independent of the pressure. Electrode films with different life cycles, such as those after roll pressing, those fresh after assembling the cell, and those that have gone through different numbers of cycles, show different resistance and sensitivity differences under test loading pressure. By measuring the pressure sensitivity difference of the diaphragm, the expansion thickness change difference of the pole piece with different life cycles can be calculated, which provides a new measurement characterization method for the analysis and evaluation of the pole piece and lithium battery.

Film resistance four-pin test

There are a variety of test methods for film resistance in batteries, of which the most commonly used are using the four-probe method and single-probe method. These methods have their own characteristics in the measurement of film resistance, but there are certain shortcomings. The traditional four-probe instrument is mainly used in the development of the thin metal coating industry, mainly for measuring the resistance of conductive coatings on the surface of insulating substrates. For battery diaphragms where the conductivity of the underlying collector is much higher than the conductivity of the coating, when the resistance is tested using the four-probe method, the direction of electron flow is parallel to the collector, whereas the electrons are transmitted perpendicularly to the direction of the collector during the actual charging and discharging operation. As a result, there is a difference between the resistance tested by this method and the actual operating conditions.

In practice, engineers often use this method to coat the slurry on a non-conductor substrate for testing the slurry film impedance. By quantitatively analyzing the resistivity in the slurry, it is possible to determine how well the slurry is dispersed. There are differences between these two methods of testing film resistance in batteries, but these methods are still the best means of performing thin film battery testing in the battery industry.