According to different electrolyte materials used in lithium ion batteries, lithium ion batteries are classified into liquid lithium ion batteries (Liquified Lithium-Ion Battery, referred to as LIB) and polymer lithium ion batteries (Polymer Lithium-Ion Battery, referred to as PLB).

Lithium ion battery (Li--ion)

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

Mobile phones basically use lithium-ion batteries. Proper use of lithium-ion batteries is very important to extend battery life. According to the requirements of different electronic products, it can be made into flat rectangular, cylindrical, rectangular and button type, and there are battery packs composed of several batteries connected in series and connected in parallel. The rated voltage of a lithium ion battery is generally 3.7V due to changes in materials, and 3.2V for a lithium iron phosphate (hereinafter referred to as ferrophosphorus) positive electrode. When fully charged, the termination charging voltage is generally 4.2V and ferrophosphorus 3.65V. The terminal discharge voltage of lithium ion batteries is 2.75V ~ 3.0V (the battery factory gives the working voltage range or the terminal discharge voltage, each parameter is slightly different, generally 3.0V, ferrophosphorus 2.5V). Continued discharge below 2.5V (FeP 2.0V) is called over-discharge, which will damage the battery.

Lithium ion batteries with lithium cobaltate type as the positive electrode are not suitable for high current discharge, and discharge time will be reduced when excessive current is discharged (higher temperature will be generated inside and energy will be lost), and may be dangerous; but lithium iron phosphate The positive electrode material lithium battery can be charged and discharged with a large current of 20C or more (C is the capacity of the battery, such as C=800mAh, 1C charge rate, ie, charging current is 800mA), which is especially suitable for electric vehicles. Therefore, the maximum discharge current given by the battery production plant should be less than the maximum discharge current in use. Lithium-ion batteries have certain requirements for temperature. The factory provides the charging temperature range, discharge temperature range and storage temperature range. Overvoltage charging will cause permanent damage to the lithium-ion battery. Lithium-ion battery charging current should be in accordance with the battery manufacturer's recommendations and require a current-limiting circuit to avoid overcurrent (overheating). The commonly used charging rate is 0.25C ~ 1C. It is often necessary to detect the battery temperature during high current charging to prevent overheating damage to the battery or explosion.

Lithium-ion battery charging is divided into two stages: first constant current charging, when it is near the end voltage, it is changed to constant voltage charging. For example, an 800mAh battery has a termination charging voltage of 4.2V. The battery is charged at a constant current of 800mA (the charging rate is 1C). At the beginning, the battery voltage is boosted with a large slope. When the battery voltage is close to 4.2V, it is changed to 4.2V constant voltage charging, the current gradually decreases, and the voltage does not change much. When the charging current drops to 1/10-50C (the setting value of each factory is different, does not affect the use), it is considered to be close to full, and the charging can be terminated (some chargers start the timer after 1/10C, ​​after a certain time End charging).