The working principle and structure of power lithium-ion battery
(1) Working principle
Lithium-ion batteries are generally batteries that use lithium alloy metal oxide as the positive electrode material, graphite as the negative electrode material, and non-aqueous electrolyte. The charging and discharging process of lithium ion batteries is the process of intercalation and deintercalation of lithium ions. In the process of intercalation and deintercalation of lithium ions, it is accompanied by the intercalation and deintercalation of electrons equivalent to that of lithium ions (the positive electrode is usually represented by insertion or deintercalation, and the negative electrode is represented by insertion or deintercalation). In the process of charging and discharging, lithium ions are intercalated/deintercalated and intercalated/deintercalated back and forth between the positive and negative electrodes, which is vividly called the “rocking chair battery”
When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte (electrolyte). The carbon as the negative electrode has a layered structure with many micropores. The lithium ions reaching the negative electrode are inserted into the micropores of the carbon layer. The more lithium ions are inserted, the higher the charging capacity. In the same way, when the battery is discharged (that is, during use of the battery), the lithium ions embedded in the carbon layer of the negative electrode are released and move back to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity.
(2) Battery composition
Lithium-ion batteries are generally composed of a positive electrode, a negative electrode, an electrolyte (electrolyte), a separator, and a casing. The common materials and the proportion of the cost.
positive electrode:
Lithium-inserting transition metal oxides: lithium cobalt oxide, lithium manganate, nickel diamond manganese composite materials, lithium iron phosphate: 40% to 46% of the total cost
negative electrode:
Lithium compounds with potential close to lithium potential: artificial graphite, natural graphite, graphitized carbon materials, graphitized mesophase carbon beads and metal oxides: 5% to 15% of the total cost
Electrolyte (electrolyte):
LiPF6 alkyl carbonate with polymer materials: ethylene carbonate (EC), propylene carbonate (PC) and low-viscosity diethyl carbonate (DEC), etc.: 5% to 11% of the total cost
Diaphragm:
Polyene microporous membrane: PE, PP or their composite membrane, PP/PE/PP three-layer diaphragm: 10%~14% of the total cost
shell:
Metal: steel, aluminum: 18%~36% of total cost
