Lithium-ion batteries are classified into a liquid lithium ion battery (Liquified Lithium-Ion Battery, LIB for short) and a polymer lithium ion battery (Polymer Lithium-Ion Battery, abbreviated as PLB), depending on the electrolyte material used in the lithium ion battery.
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 "squeaky" and cannot be overcharged or over-discharged during use (which can damage the battery or cause it to be scrapped). Therefore, there are protective components or protection circuits on the battery to prevent expensive battery damage. Lithium-ion battery charging requirements are very high, to ensure that the termination voltage accuracy is within ±1%, major semiconductor device manufacturers have developed a variety of lithium-ion battery charging IC to ensure safe, reliable and fast charging.
Mobile phones basically use lithium-ion batteries. Proper use of lithium-ion batteries is important to extend battery life. It can be made into flat rectangular, cylindrical, rectangular and button type according to the requirements of different electronic products, and has a battery pack 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 a change in material, and 3.2V is a lithium iron phosphate (hereinafter referred to as a ferrophosphorus) positive electrode. The termination charging voltage when fully charged is generally 4.2V and the phosphorus iron is 3.65V. The termination discharge voltage of the lithium ion battery is 2.75V to 3.0V (the battery factory gives the working voltage range or gives the termination discharge voltage, and the parameters are slightly different, generally 3.0V, and the phosphorus iron is 2.5V). Continued discharge below 2.5V (phosphorus iron 2.0V) is called overdischarge, and overdischarge will damage the battery.
A lithium ion battery in which the lithium cobaltate type material is a positive electrode is not suitable for use as a large current discharge, and an excessive current discharge reduces the discharge time (a high temperature is generated internally to lose energy), and may be dangerous; but lithium iron phosphate The cathode 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 charging rate, ie, charging current is 800mA), and is particularly suitable for electric vehicles. Therefore, the battery production plant gives the maximum discharge current, which should be less than the maximum discharge current in use. Lithium-ion batteries have certain requirements on temperature. The factory gives the charging temperature range, discharge temperature range and storage temperature range. Over-voltage charging will cause permanent damage to the lithium-ion battery. Lithium-ion battery charging current should be based on the recommendations of the battery manufacturer and require a limited current circuit to avoid overcurrent (overheating). The commonly used charging ratio is 0.25C to 1C. It is often necessary to detect the battery temperature during high current charging to prevent overheating from damaging the battery or exploding.
Lithium-ion battery charging is divided into two phases: first constant current charging, and changing to constant voltage charging when it is close to the termination voltage. For example, a battery of 800 mAh capacity has a termination charging voltage of 4.2V. The battery is charged at a constant current of 800 mA (charging rate 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, it 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).
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