Overview of Lithium-ion Batteries

1. Lithium-ion battery components

Steel shell/aluminum shell/cylindrical/soft packaging series:

(1) Positive electrode-The active material is generally Lithium Manganate or Lithium cobaltate, and NMC materials. The conductive current collector uses electrolytic aluminum foil with a thickness of 10-20 microns.

(2) Diaphragm-a specially formed polymer film with a microporous structure that allows lithium ions to pass freely, but electrons cannot pass.

(3) Negative electrode-the active material is graphite, or carbon with a similar graphite structure, and the electrolytic copper foil with a thickness of 7-15 microns is used as the conductive current collector.

(4) Organic electrolyte—carbonic acid ester solvent dissolved with Lithium Hexafluorophosphate, while gel electrolyte is used for polymer.

(5) Battery shell-divided into steel shell (square type is rarely used), aluminum shell, nickel-plated iron shell (for cylindrical batteries), aluminum plastic film (soft packaging), etc., as well as battery caps, which are also the terminal of the battery positive and negative .

2. Classification of lithium-ion batteries

According to the different electrolyte materials used in lithium-ion batteries, lithium-ion batteries are divided into Liquified Lithium-Ion Battery (abbreviated as LIB) and Polymer Lithium-Ion Battery (abbreviated as PLB).

Lithium ion battery (Li-ion)

Rechargeable lithium battery packs are the most widely used batteries in modern digital products such as mobile phones and notebook computers, but they are more "finicky" which cannot be overcharged or overdischarged during use (it will damage the battery or cause it to be scrapped). Therefore, there are protective components or protective circuits on the battery to prevent expensive battery damage. Lithium-ion battery charging requirements are very high, it must be ensured that the termination voltage accuracy is within ±1%. Major semiconductor device manufacturers have developed a variety of lithium-ion battery charging ICs to ensure safe, reliable, and fast charging.

Proper use of lithium-ion batteries is very important to extend battery life. It can be made into flat rectangle, cylinder, rectangle and button type according to the requirements of different electronic products, and has a battery pack composed of several batteries connected in series and parallel. The rated voltage of lithium-ion batteries is generally 3.7V due to changes in materials, and 3.2V for ferrous lithium phosphate cathodes. The final charging voltage when fully charged is generally 4.2V, and ferrous lithium phosphate 3.65V. The final discharge voltage of lithium-ion batteries is 2.75V~3.0V (the battery factory gives the working voltage range or the final discharge voltage, the parameters are slightly different, generally 3.0V, 2.5V for ferrous lithium phosphate). To continue to discharge below 2.5V (ferrous lithium phosphate 2.0V) is called over discharge, and over discharge will damage the battery.

Lithium-ion battery charging is divided into two stages: first constant current charging and changing to constant voltage charging when it is close to the termination voltage. For example, a battery with a capacity of 800mAh has a final charging voltage of 4.2V. The battery is charged with a constant current of 800mA (the C-rate is 1C). At the beginning, the battery voltage is boosted with a larger slope. When the battery voltage is close to 4.2V, it is changed to 4.2V constant voltage charging. The current gradually drops and the voltage changes little. When the charging current drops to 1/10-50C (various factory settings, it does not affect the use), it is considered that it is nearly full and the charging can be terminated (some chargers start the timer after 1/10C, and end charging after a certain time).