What is polarization of lithium-ion batteries?

Resistance

The resistance represents the degree of hindrance of a circuit element to the current transfer, in ohms.

So how does polarization come about?

When the battery is discharged, all of these energies can not be fully converted into electrical energy. Electrochemical reactions are always accompanied by energy losses. These energy losses include:

1) Activated polarization-it causes an electrochemical reaction on the electrode surface

2) Concentration polarization-It is due to the difference in the concentration of reactants and products on the electrode surface and in the body phase, and is the result of material transfer. The existence of polarization consumes part of the energy and releases it in the form of heat.

Polarization

Batteries are polarized during charging and discharging. Lithium-ion batteries can usually be polarized into three types: ohmic polarization, electrochemical polarization, and concentration polarization. Several types of polarization also have different response speeds. There are many factors that affect the degree of polarization, but under normal circumstances, the greater the density of charge and discharge current, the greater the polarization.

Explain the following categories:

(1) Ohm polarization

As the name implies, the polarization caused by the ohmic resistance of a lithium-ion battery is called ohmic polarization and also becomes resistive polarization. The ohmic resistance(R) of the battery consists of electrode material, electrolyte, diaphragm resistance, and contact resistance of various parts(some explanations also include membrane resistance). When a certain current is passed, its polarization potential can be calculated. E = IR(Europe).

Polarization and internal resistance

Ohm polarization occurs instantaneously.

(2) Electrochemical polarization

Refers to the polarization caused by the speed of electrochemical reactions at the positive and negative poles being less than the speed of electronic motion.

Electrochemical polarization is generally considered to be microseconds

(3) Concentration polarization

Refers to the polarization caused by the diffusion speed of lithium ions involved in the reaction in the solid phase is less than the speed of the electrochemical reaction.

Concentration polarization is generally considered to be second level.

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