Lithium ion batteries are a type of rechargeable battery composed of a positive electrode, negative electrode, separator, and electrolyte. Lithium ion batteries refer to batteries that use lithium ion intercalation compounds as positive electrode materials. It has the characteristics of high voltage, high energy density, high output power, long cycle life, small self discharge, fast charging, safety and environmental protection
The composition and structure of lithium-ion batteries:
Positive electrode - The active substance is generally lithium manganese oxide or lithium cobalt oxide, with nickel cobalt manganese oxide materials. Electric bicycles generally use nickel cobalt manganese oxide lithium (commonly known as ternary) or ternary+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.
Diaphragm - a specially formed polymer film with a microporous structure that allows lithium ions to pass freely, while electrons cannot.
Negative electrode - The active material is graphite or carbon with a similar graphite structure, and the conductive current collector uses electrolytic copper foil with a thickness of 7-15 microns.
Organic electrolyte - carbonate solvent dissolved with lithium hexafluorophosphate, and gel electrolyte used for polymer.
Battery shell - divided into steel shell (rarely used in square shape), aluminum shell, nickel plated iron shell (used in cylindrical batteries), aluminum-plastic film (soft packaging), etc., as well as the battery cover, which is also the positive and negative terminals of the battery.
The working principle of lithium-ion batteries:
The charging and discharging process of lithium batteries is the process of lithium ion insertion and extraction. In the process of lithium ion insertion and removal, there is also the insertion and removal of equivalent electrons with lithium ions (traditionally, the positive electrode is represented by insertion or removal, while the negative electrode is represented by insertion or removal). During the charging and discharging process, lithium ions are intercalated/deintercaled and intercalated/deintercaled back and forth between the positive and negative electrodes, commonly referred to as "rocking chair batteries".
When charging the battery, lithium ions are generated on the positive electrode of the lithium battery, and the generated lithium ions move through the electrolyte to the negative electrode. As the negative electrode, carbon has a layered structure with many micropores, and the lithium ions that reach the negative electrode are embedded into the micropores of the carbon layer. The more lithium ions embedded, the higher the charging capacity. Similarly, when discharging the battery, the lithium ions embedded in the negative carbon layer detach and move back to the positive electrode. The more lithium ions are returned to the positive electrode, the higher the discharge capacity.
The above is an introduction to the principles of lithium-ion batteries provided by lithium-ion battery manufacturer Youchuangwei.