The Structure and Principle of Lithium Ion Battery

1. The main components of lithium ion battery

• Positive electrode: The active material mainly refers to lithium cobalt oxide, lithium manganate, lithium iron phosphate, lithium nickelate, lithium nickel cobalt manganate, etc. The conductive current collector generally uses aluminum foil with a thickness of 10--20 microns;

  
  

• Diaphragm: Diaphragm refers to a special plastic film that allows lithium ions to pass through but insulates electronics. At present, there are mainly three types of diaphragms, that is, PE, PP and their combination. There is also a type of inorganic solid diaphragm. For instance, alumina diaphragm coating is an inorganic solid diaphragm;

  
  

• Negative electrode: The active material for negative electrode mainly refers to graphite, lithium titanate, or carbon materials with a similar graphite structure. The conductive current collector generally uses copper foil with a thickness of 7-15 microns;

  
  

• Electrolyte: The electrolyte used in lithium ion batteries is generally an organic system, such as the carbonate solvent with lithium hexafluorophosphate dissolved in it. Some polymer batteries also use gel-like electrolyte;

  
  

• Battery case: The battery cases of the lithium ion batteries can be mainly divided into hard cases (steel case, aluminum case, nickel-plated iron case, etc.) and soft cases (aluminum plastic film).

2. The principle of lithium ion batteries

Can you recharge lithium ion batteries? Absolutely yes. When the battery is being charged, lithium ions will be first extracted from the positive electrode and then embedded to the negative electrode, and vice versa during discharge. And this requires an electrode to be in a lithium-intercalation state before assembly. Generally, lithium-intercalating transition metal oxides, such as LiCoO₂, LiNiO₂, and LiMn₂O₄, that have a potential greater than 3V relative to lithium and are stable in the air will be used as positive electrodes.

As for the materials of the negative electrode, the lithium compound that can be inserted as close as possible to the lithium potential will usually be selected. For example, carbon materials like natural graphite, synthetic graphite, carbon fiber, and mesophase carbon and metal oxides, including SnO, SnO₂, and tin composite oxide SnBxPyOz (x=0.4～0.6, y=0.6～0.4, z=(2 +3x+5y)/2) can all be used as negative electrode materials.

The electrolyte normally adopts a mixed solvent system for LiPF6 of ethylene carbonate (EC), propylene carbonate (PC) and low viscosity diethyl carbonate (DEC) and other alkyl carbonates.

The membrane generally adopts polyolefin microporous membranes such as PE, PP or their composite membranes. Among all of the used membranes, the PP/PE/PP three-layer membrane is the most popular one. Not only does it have a lower melting point, but it also has a higher puncture resistance, which plays a great role in heat insurance.

The shell of lithium ion battery is normally made of steel or aluminum, and the cover assembly has the functions of explosion-proof and power-off.

As one of the professional lithium ion battery manufacturers in China, KIJO sells lithium-ion batteries that have the advantages of fast charging, long cycle life, and wide working temperature range from -20°C to 50°C. Moreover, our lithium batteries can also be disassembled easily with their ow handles. Thus, if you are still looking for high-quality lithium ion batteries, KIJO's ion battery series can be a good choice!