Working principle of 18650 lithium battery.
1、 Lithium battery structure
The components of lithium-ion batteries are as follows:
(1) Positive electrode - The active material is generally lithium manganese oxide or lithium cobalt oxide, nickel cobalt lithium manganese oxide material. Electric bicycles commonly use nickel cobalt lithium manganese oxide (commonly known as ternary) or ternary+a small amount of lithium manganese oxide. Pure lithium manganese oxide and lithium iron phosphate gradually fade out due to their large volume, poor performance, or high cost. The conductive electrode fluid uses electrolytic aluminum foil with a thickness of 10-20 microns.
(2) Diaphragm - a specially formed polymer film with a microporous structure that allows lithium ions to freely pass through, while electrons cannot.
(3) Negative electrode - the active material is graphite or carbon with a graphite like structure, and the conductive current collector uses electrolytic copper foil with a thickness of 7-15 microns.
(4) Organic electrolyte - carbonate solvent dissolved with lithium hexafluorophosphate, and gel electrolyte used for polymer.
(5) Battery shell - divided into steel shell (rarely used in square shape), aluminum shell, nickel plated iron shell (used for cylindrical batteries), aluminum-plastic film (flexible packaging), etc., as well as the battery cap, which is also the positive and negative terminal of the battery.
2、 Schematic diagram of the working principle of lithium batteries
Below, we will introduce the working principle of lithium batteries from three main parts: charging process, discharging process, and battery protection board:
The components of lithium-ion batteries are as follows:
(1) Positive electrode - The active material is generally lithium manganese oxide or lithium cobalt oxide, nickel cobalt lithium manganese oxide material. Electric bicycles commonly use nickel cobalt lithium manganese oxide (commonly known as ternary) or ternary+a small amount of lithium manganese oxide. Pure lithium manganese oxide and lithium iron phosphate gradually fade out due to their large volume, poor performance, or high cost. The conductive electrode fluid uses electrolytic aluminum foil with a thickness of 10-20 microns.
(2) Diaphragm - a specially formed polymer film with a microporous structure that allows lithium ions to freely pass through, while electrons cannot.
(3) Negative electrode - the active material is graphite or carbon with a graphite like structure, and the conductive current collector uses electrolytic copper foil with a thickness of 7-15 microns.
(4) Organic electrolyte - carbonate solvent dissolved with lithium hexafluorophosphate, and gel electrolyte used for polymer.
(5) Battery shell - divided into steel shell (rarely used in square shape), aluminum shell, nickel plated iron shell (used for cylindrical batteries), aluminum-plastic film (flexible packaging), etc., as well as the battery cap, which is also the positive and negative terminal of the battery.
2、 Schematic diagram of the working principle of lithium batteries
Below, we will introduce the working principle of lithium batteries from three main parts: charging process, discharging process, and battery protection board:
The components of lithium-ion batteries are as follows:
(1) Positive electrode - The active material is generally lithium manganese oxide or lithium cobalt oxide, nickel cobalt lithium manganese oxide material. Electric bicycles commonly use nickel cobalt lithium manganese oxide (commonly known as ternary) or ternary+a small amount of lithium manganese oxide. Pure lithium manganese oxide and lithium iron phosphate gradually fade out due to their large volume, poor performance, or high cost. The conductive electrode fluid uses electrolytic aluminum foil with a thickness of 10-20 microns.
(2) Diaphragm - a specially formed polymer film with a microporous structure that allows lithium ions to freely pass through, while electrons cannot.
(3) Negative electrode - the active material is graphite or carbon with a graphite like structure, and the conductive current collector uses electrolytic copper foil with a thickness of 7-15 microns.
(4) Organic electrolyte - carbonate solvent dissolved with lithium hexafluorophosphate, and gel electrolyte used for polymer.
(5) Battery shell - divided into steel shell (rarely used in square shape), aluminum shell, nickel plated iron shell (used for cylindrical batteries), aluminum-plastic film (flexible packaging), etc., as well as the battery cap, which is also the positive and negative terminal of the battery.
2、 Working principle of lithium battery
Below, we will introduce the working principle of lithium batteries from three main parts: charging process, discharging process, and battery protection board:
The positive electrode of the battery is generated from lithium ions, which jump into the electrolyte and climb through the winding holes on the separator to move to the negative electrode, where they combine with electrons that have already run to the negative electrode through an external circuit. The reaction that occurs on the positive electrode is: LiCoO2==Charging==Li1-xCoO2+Xli++Xe (electron). 2. Discharge process of lithium battery
During discharge, both electrons and Li+move simultaneously, with the same direction but different paths. Electrons run from the negative electrode to the positive electrode through an external circuit; Lithium ion Li+"jumps" into the electrolyte from the negative electrode, "crawls" through the winding small holes on the separator, "swims" to reach the positive electrode, and combines with the electrons that have already run over. The battery capacity we usually refer to is the discharge capacity.
3. Battery protection board
As the name suggests, a battery protection board is mainly an integrated circuit board that provides protection for rechargeable batteries (generally referring to lithium batteries). The reason why lithium batteries (rechargeable type) need protection is that the material of the lithium battery itself determines that it cannot be overcharged, overdischarged, overcurrent, short circuited, or charged and discharged at ultra-high temperatures. Therefore, lithium batteries always have protective plates and a current fuse. The following figure shows the battery board protection circuit. PTC： Positive temperature coefficient thermistor; NTC： Negative temperature coefficient thermistor, when the ambient temperature rises, its resistance decreases, and when using electrical or charging equipment, it can respond in a timely manner, control internal interruption and stop charging and discharging; U1 is a circuit protection chip, and U2 is two reverse connected MOSFET switches. Under normal conditions, both CO and DO of battery board U1 output high voltage, and both MOSFETs are in the open state, allowing the battery to charge and discharge freely.
