I. Lithium-ion battery charging principle
The working principle of a lithium-ion battery refers to its charging and discharging principle. When the battery is charged, lithium ions are generated at the positive electrode, and these lithium ions move through the electrolyte to the negative electrode.
The carbon used as the negative electrode has a layered structure with many micropores. Lithium ions that reach the negative electrode are embedded in the micropores of the carbon layer. The more lithium ions embedded, the higher the charging capacity.
Similarly, when a battery is discharged (i.e., when we use the battery), lithium ions embedded in the carbon layer of the negative electrode are released and move back to the positive electrode. The more lithium ions return to the positive electrode, the higher the discharge capacity. The battery capacity we usually refer to is the discharge capacity.
Lithium-ion batteries generally require the charging process to be controlled in four stages: trickle charging (low-voltage pre-charging), constant current charging, constant voltage charging, and charging termination.
When a lithium-ion battery is directly connected to a power source without a charging management chip, the sudden influx of a large current when the battery is low can damage it. This is because the large current generates heat quickly, shortening the battery's lifespan.
The basic requirements for charging lithium-ion batteries are specific charging current and voltage to ensure safe charging. The charging method for lithium-ion batteries is voltage-limited constant current, both controlled by an IC chip.
II. What is the charging current of a lithium-ion battery?
The maximum charging current that lithium-ion batteries can accept is usually 1C or even less, with laptop batteries having a maximum charging rate of 0.9C. A 1C charging rate refers to charging at 1x the capacity with a current of 1x, taking 1 hour to charge. In practice, to extend battery life, it's generally recommended to charge at 0.1-0.3C for 10-4 hours.
The national standard stipulates that the charging current of lithium-ion batteries is 0.2C-1C, and the charging current of a 100AH battery can be 20A-100A. That is to say, if a battery with a capacity of 1500mAh is charged at 0.2C, the charging current will be 0.2 × 1500 = 300mA, and it will take 5 hours to charge.
Lithium iron phosphate batteries can generally use charge and discharge currents of 1C or higher (15C), making them suitable as power lithium batteries.
Generally, the charging current for lithium-ion batteries is set between 0.2C and 1C. The higher the current, the faster the charging, but the greater the heat generated by the battery. Moreover, charging with too high a current will not fully charge the battery because the electrochemical reaction inside the battery takes time.
