What causes the excessive internal resistance of lithium-ion batteries?

July 07, 2021

1. Lithium Cell produce process part

(1) There is too little conductive agent in the positive electrode ingredients (the conductivity between materials is not good, because the conductivity of lithium cobalt itself is very poor)

(2) There are too many binders in the positive electrode ingredients (binders are generally polymer materials with strong insulating properties)

(3) There are too many binders in the negative electrode ingredients (the binders are generally polymer materials with strong insulating properties)

(4) Uneven distribution of ingredients

(5) The binder solvent is incomplete when compounding (not completely soluble in NMP, water)

(6) The surface density of coating and drawing is too large (large ion migration distance)

(7) The compaction density of the lithium ion battery is too large, and the roller is too compact. (Rolling is too dead, and some of the active material structure is destroyed)

(8) The positive lug is not welded firmly, and there is a virtual weld

(9) Welding or riveting of the negative electrode is not strong, resulting in false welding and desoldering

(10) The winding is not tight and the core is loose (to increase the distance between the positive and negative plates)

(11) The positive lug and the shell are not welded firmly

(12) The negative pole lug and the pole are not welded firmly

internal resistance of lithium-ion batteries

2. Materials part

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

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

(3) The influence of lithium ion battery electrolyte material (small conductivity, high viscosity)

(4) The influence of the positive electrode PVDF material. (Large amount or high molecular weight)

(5) Influence of positive electrode conductive agent material. (Poor conductivity, high resistance)

(6) The influence of positive and negative electrode lug materials (thickness is poor, conductivity is poor, thickness is uneven, material purity is poor)

(7) Copper foil and aluminum foil have poor conductivity or oxides on the surface

3. Other aspects

(1) Deviation of Li-ion battery internal resistance test instrument

(2) Human operation

(3) Lithium-ion battery use environment