Subjective And Objective Factors That Cause Excessive Internal Resistance Of Lithium Batteries

The internal resistance, static internal resistance and working internal resistance of lithium batteries are often different. In different environments, the internal resistance of different temperatures also changes. What factors affect the internal resistance of lithium batteries?

1. Technology

There are too few conductive materials for the positive electrode (the conductivity between the materials is not good because the conductivity of lithium cobalt itself is very poor).

There are too many binders for the positive electrode (the binders are generally high-molecular materials and have strong insulating properties).

There are too many binders for the negative electrode (the binders are generally high-molecular materials and have strong insulating properties).

The ingredients are unevenly dispersed.

The binder solvent is not complete when compounding. (Not completely soluble in NMP, water)

The design of the surface density of the coating drawing is too large. (Large ion migration distance)

The compaction density is too high and the roller compaction is too compact. (The roller is over-pressed and some of the active material structure is destroyed)

The positive lug is not welded firmly, and a virtual weld appears.

The welding or riveting of the negative electrode ears is not strong, and there is a virtual welding and desoldering.

The winding is not tight and the winding core is loose. (Increase the distance between the positive and negative plates)

The welding between the positive ear and the casing is not firm.

The negative electrode lug and the pole are not welded well.

The baking temperature of the battery is too high, and the separator shrinks. (Diameter of diaphragm is reduced)

Liquid injection volume is too small (conductivity decreases, internal resistance increases quickly after circulation!)

The shelf time after injection is too short, the electrolyte is not fully wetted

It is not fully activated when it is formed.

There is too much leakage of electrolyte during the formation process.

During the production process, moisture control is not strict, and the battery swells.

The battery charging voltage is set too high, causing overcharging.

The battery storage environment is unreasonable.

2. Materials

The positive electrode material has high resistance. (Poor conductivity, such as lithium iron phosphate)

Influence of diaphragm material (diaphragm thickness, small porosity, small pore size)

Influence of electrolyte material. (Small conductivity, high viscosity)

Positive PVDF material. (Large amount or large molecular weight)

Positive conductive material influence. (Poor conductivity, high resistance)

Influence of positive and negative pole lug materials (thin thickness is poor conductivity, uneven thickness, poor material purity)

Copper foil and aluminum foil materials have poor conductivity or oxide on the surface.

The internal resistance of the cover plate pole riveting contact is too large.

The negative electrode material has high resistance.

3. Other aspects

Internal resistance test instrument deviation.

Man-made operation.

surroundings.