Brief introduction of Li ion battery

　　Rechargeable lithium-ion battery is the most widely used battery in mobile phones, laptops and other modern digital products, but it is "delicate" and cannot be overcharged or discharged (it will damage the battery or make it obsolete). Therefore, there are protective components or circuits on the battery to prevent expensive battery damage. The charging requirements of lithium ion batteries are very high. To ensure the accuracy of terminal voltage within ± 1%, major 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. The correct use of lithium ion batteries is very important for prolonging battery life. According to the requirements of different electronic products, it can be made into flat rectangular, cylindrical, rectangular and button type, and has a battery pack composed of several batteries connected in series and in parallel. The rated voltage of lithium ion battery is generally 3.7V due to material changes, and 3.2V for lithium iron phosphate cathode. When fully charged, the terminal charging voltage is generally 4.2V, and lithium iron phosphate is 3.65V. The terminal discharge voltage of lithium ion battery is 2.75V ～ 3.0V (the battery manufacturer gives the working voltage range or terminal discharge voltage, and the parameters are slightly different, generally 3.0V, and 2.5V for ferrophosphate). Continuous discharge below 2.5V (lithium iron phosphate 2.0V) is called overdischarge, which will damage the battery.

　　Lithium ion batteries made of lithium cobalate as cathode materials are not suitable for high current discharge. Excessive current discharge will reduce the discharge time (higher temperature will be generated internally and energy will be lost), and may cause danger; However, lithium battery made of lithium iron phosphate cathode material can be charged and discharged with a large current of 20C or more (C is the battery capacity, such as C=800mAh, and the charging rate of 1C is 800mA), which is particularly suitable for electric vehicles. Therefore, the maximum discharge current given by the battery manufacturer 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 lithium ion batteries. The charging current of lithium ion battery shall be in accordance with the battery manufacturer's recommendations, and the current limiting circuit shall be required to avoid overcurrent (overheating). The commonly used charging rate is 0.25C~1C. When charging with high current, it is often necessary to detect the battery temperature to prevent overheating damage to the battery or explosion.

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