Lithium battery charging circuit diagram

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Lithium battery is the leader in the rechargeable battery family after nickel-cadmium and nickel-hydrogen batteries. Lithium-ion batteries are widely used for their excellent characteristics: mobile phones, camcorders, notebook computers, cordless phones, power tools, remote control. Or in portable electronic devices such as electric toys and cameras.

1. Lithium battery and nickel-cadmium and nickel-hydrogen rechargeable battery: The negative electrode of lithium-ion battery is graphite crystal, and the positive electrode is usually lithium dioxide. Lithium ions move from the positive electrode to the negative electrode during charging and are embedded in the graphite layer. During discharge, lithium ions are detached from the surface of the negative electrode in the graphite crystal and moved toward the positive electrode. Therefore, during the charging and discharging of the battery, lithium always appears in the form of lithium ions, rather than in the form of metallic lithium. Therefore, this type of battery is called a lithium ion battery, or a lithium battery.

The lithium battery has the advantages of small volume, large capacity, light weight, no pollution, high single-section voltage, low self-discharge rate, and many battery cycles, but the price is relatively expensive. Nickel-cadmium batteries are gradually being phased out due to their low capacity, serious self-discharge, and pollution to the environment. Ni-MH batteries have a high performance-price ratio and do not pollute the environment, but the cell voltage is only 1.2V, which is limited in the scope of use.

Second, the characteristics of lithium battery:

1. It has higher weight-to-energy ratio and volume-to-energy ratio;

2, the voltage is high, the single-cell lithium battery voltage is 3.6V, which is equal to the series voltage of 3 nickel-cadmium or nickel-hydrogen rechargeable batteries;

3, self-discharge can be stored for a long time, this is the most outstanding superiority of the battery;

4. No memory effect. Lithium batteries do not have the so-called memory effect of nickel-cadmium batteries, so lithium batteries do not need to be discharged before charging;

5, long life. Under normal working conditions, the number of charge/discharge cycles of the lithium battery is much greater than 500 times;

6, can be quickly charged. The lithium battery can usually be charged with a current of 0.5 to 1 times, so that the charging time is shortened to 1 to 2 hours;

7, can be used in parallel;

8. Because the battery does not contain heavy metal elements such as cadmium, lead and mercury, it is environmentally friendly and is the most advanced green battery in the world;

9, high cost. Lithium batteries are more expensive than other rechargeable batteries.

Third, the internal structure of the lithium battery:

Lithium batteries usually have two shapes: cylindrical and rectangular.

The inside of the battery adopts a spiral wound structure, and is formed by spacing a positive and negative electrode with a very fine and highly permeable polyethylene film insulation material. The positive electrode includes a lithium ion collector composed of lithium and cobalt dioxide and a current collector composed of an aluminum film. The negative electrode is composed of a lithium ion collector composed of a sheet-like carbon material and a current collector composed of a copper film. The battery is filled with an organic electrolyte solution. Safety valves and PTC components are also included to protect the battery from damage during abnormal conditions and output short circuits.

The voltage of a single-cell lithium battery is 3.6V, and the capacity cannot be infinite. Therefore, single-cell lithium batteries are often serially and parallelly processed to meet the requirements of different occasions.