Take LiCoO, the lithium ion secondary battery of the system as an example to illustrate its working principle.
Generally, a lithium ion secondary battery is composed of a positive electrode, an electrolyte, a separator, and a negative electrode.
When charging, the lithium ions in the positive electrode are extracted from the LiCoO layered structure, the valence of the Co element increases from +Ⅲ to +Ⅳ, the positive electrode material undergoes oxidation reaction, and the lithium ions migrate through the electrolyte to the negative electrode of the battery.
The layered structure of the carbon material combines with carbon to form LiCx. When the battery is connected to a load, the reactions that occur on the two electrodes are the reverse reactions of the reactions that occur during charging.
The diaphragm is located between the positive and negative reaction electrodes. The diaphragm can permeate ions, but does not allow electrons to permeate.
At the same time, when a certain degree of micro-short circuit occurs between the positive and negative electrodes of the battery, the diaphragm also plays a role in blocking protection.
The rated voltage of the lithium ion battery is 3.6V. The voltage when the battery is fully charged (called the termination charge voltage) is generally 4.2V; the termination discharge voltage of the lithium-ion battery is 2.5V. If the lithium-ion battery continues to be used after the voltage has dropped to 2.5V during use, it is called overdischarge, which will damage the battery.
Lithium-ion batteries are more expensive. If it does not meet its charging and use requirements, it is easy to explode and life-span phenomenon. Because lithium-ion batteries are sensitive to temperature, overvoltage, overcurrent, and overdischarge, all batteries have integrated thermistors (monitor charging temperature) and protection circuits against overvoltage, overcurrent, and overdischarge.