Working principle of lithium-ion battery packs:
A lithium-ion battery is a type of rechargeable battery that relies on the intercalation and deintercalation of lithium ions between the positive and negative electrodes to store and release energy.
1. Charging process
Driven by an electric field, lithium ions are extracted from the positive electrode lattice, pass through the electrolyte, and are inserted into the negative electrode lattice.
At the start of charging, the voltage of the battery to be charged should be checked first. If the voltage is below 3V, pre-charging should be performed first, with the charging current being 1/10 of the set current, generally around 0.05C. After the voltage rises to 3V, the standard charging process begins. The standard charging process is as follows: constant current charging is performed at the set current. When the battery voltage rises to 4.20V, constant voltage charging is switched to maintain the charging voltage at 4.20V. At this time, the charging current gradually decreases. When the current drops to 1/10 of the set charging current, charging ends.
2. Discharge process
The process is exactly the opposite. Lithium ions return to the positive electrode, while electrons travel through the external circuit via electrical appliances to the positive electrode and recombine with lithium ions. When the battery discharges, electrons e from the negative electrode travel through the external circuit to the positive electrode, while positive lithium ions Li+ jump from the negative electrode into the electrolyte, crawl through the winding holes in the separator, swim to the positive electrode, and recombine with the electrons that have already arrived.
The higher the battery discharge current, the smaller the discharge capacity and the faster the voltage drops.
Methods for manufacturing lithium-ion batteries
Step 1: Ingredients
The materials are stirred in a high-vacuum, fully automated system for 10 hours to ensure uniform dispersion of the materials required for lithium-ion batteries, thereby improving battery consistency and overall performance. Why is this necessary? Because material preparation is a core aspect of lithium-ion battery manufacturing; poor material preparation directly impacts battery performance.
Step 2: Coating
An automated feeding system, an automated blade adjustment system, and an online thickness measurement system are used to ensure uniform coating of the positive and negative electrode sheets. Why is this necessary? Because coating is fundamental to lithium-ion battery manufacturing; it determines the battery's consistency.
Step 3: Adjusting the rollers
After the positive and negative electrode sheets are coated, the positive and negative materials are relatively loose. A certain amount of pressure needs to be applied to the electrode sheets to compact the positive and negative electrode materials to a certain range.
Step 4: Slice into strips
Depending on the battery model, the positive and negative electrode plates need to be cut to the required width. For example, for an 18650 lithium-ion battery, the electrode plate width is within 56-58mm.
Step 5: Film preparation and winding
A fully automated sheet-making machine is used to weld the positive and negative tabs onto the positive and negative electrode sheets. A fully automated winding machine is then used to wind the positive and negative electrode sheets and the separator together into a cylindrical shape.
Step 6: Bottom grooving and vacuum drying
The core is placed inside the steel casing, and the negative electrode tab is automatically welded and automatically grooved. Additionally, it undergoes high-vacuum, high-temperature baking to dry out any remaining moisture, ensuring the performance of the lithium-ion battery.
Step 7: Dissolve in water
Lithium-ion batteries undergo charge-discharge testing before shipment; they are charged before leaving the factory.
Step 8: Assemble the lithium-ion battery
The fully automatic welding machine welds multiple batteries together using connecting pieces, then mounts them onto a circuit board, performs aging tests, and inspects them before shipping.
