The resistance indicates the degree of resistance of a circuit element to current transfer. The unit is Ohm.
So how does polarization come about?
When the battery is discharged, all these energy can not be completely converted into electric energy. The electrochemical reaction is always accompanied by the loss of energy, which includes: 1) activation polarization -- it causes the electrochemical reaction on the electrode surface; 2) concentration polarization -- it is due to the different concentrations of reactants and products on the electrode surface and in the bulk phase, and it is the result of material transfer. The existence of polarization consumes part of the energy and emits it in the form of heat.
In the process of charge and discharge, the polarization of lithium-ion battery can be divided into three types: ohmic polarization, electrochemical polarization and concentration polarization. The response speed of each kind of polarization is different. There are many factors that affect the degree of polarization, but in general, the greater the charge discharge current density is, the greater the polarization is.
The following categories are explained:
(1) Ohmic polarization
As the name implies, the polarization caused by the ohmic internal resistance of lithium-ion batteries is called ohmic polarization, which is also called resistance polarization. The ohmic internal resistance (R) of the battery consists of electrode material, electrolyte, diaphragm resistance and contact resistance of all parts (some explanations also include membrane resistance). When a certain current is passed, its polarization potential can be calculated, e = IR (Ohm).
Ohmic polarization occurs instantaneously.
(2) Electrochemical polarization
It refers to the polarization caused by the speed of electrochemical reaction on the positive and negative electrodes is less than the speed of electron movement. Electrochemical polarization is generally considered to be microsecond
(3) Concentration polarization
It refers to the polarization caused by the diffusion speed of lithium ion in solid phase is less than that of electrochemical reaction. Concentration polarization is generally considered to be second level.