What are the materials for lithium-ion batteries?

Writer： admin Time：2019-09-18 03:19:09 Browse：145℃

Lithium ion batteries are composed of the following components: positive electrode, negative electrode, electrolyte, electrolyte salt, adhesive, separator, positive lead, negative lead, center terminal, insulation material, safety valve, positive temperature coefficient terminal (PTC terminal), negative current collector, positive current collector, conductive agent, and battery shell.

1. Positive electrode material

The cathode materials are lithium containing transition metal oxides, phosphides such as LiCoO2, LiFePO4, and conductive polymers such as polyacetylene, polyphenylene, polypyrrole, Polythiophene, and active polysulfide compounds; Lithium intercalated compound cathode materials are an important component of lithium-ion batteries.

The positive electrode material accounts for a large proportion in lithium-ion batteries (the mass ratio of positive and negative electrode materials is 3:1 to 4:1), so the performance of the positive electrode material will greatly affect the performance of the battery, and its cost directly determines the cost of the battery.

2. Negative electrode material

Negative electrode materials are carbon materials, nitrides, silicon based materials, tin based materials, new alloys, etc. that can store a large amount of lithium; The biggest difference between lithium-ion batteries and secondary lithium-ion batteries is that the former uses lithium intercalation compounds instead of metal lithium as the negative electrode of the battery. Therefore, the research and development of lithium-ion batteries is largely the research and development of negative electrode lithium intercalation compounds.

3. Electrolytes

Electrolytes are organic solutions, polymers, and inorganic solids of lithium salts; Electrolytes, as an important component of batteries, play a role in transporting ions and conducting current between the positive and negative electrodes. Choosing a suitable electrolyte is the key to obtaining a lithium-ion battery with high energy density and power density, long cycle life, and good safety performance.

4. Adhesive

The adhesive is fluoropolymer, ethylene propylene rubber, carbon based material, silica gel based gel, radioactive cross-linked polymer, etc; The main function of adhesives is to adhere active substances; Adhesion between the active substance and the collecting fluid; During the charging and discharging process, preserve and adhere to the active substance and cause the active substance to adhere to the collector; Forming a slurry during the production process to facilitate coating; Alleviate the volume expansion of carbon negative electrodes during lithium insertion.

5. Diaphragm material

The membrane material is porous polyolefin, polyamide non-woven fabric, etc; The function of lithium-ion battery separator paper in lithium-ion batteries is to isolate the positive and negative electrode materials. The quality of separator paper directly affects the safety performance and capacity of batteries.

6. Positive temperature coefficient terminal

The positive temperature coefficient terminal (PTC terminal) is a composite material of conductive fillers and polymers; The positive temperature coefficient terminal can prevent excessive battery current. Under normal temperature, the resistance of the positive temperature coefficient terminal is very small, but when the temperature reaches around 120 ℃, the resistance suddenly increases, leading to a rapid decrease in current. After the temperature drops, the resistance of the positive temperature coefficient terminal decreases again and can be charged and discharged normally.

7. Negative current collector material

The negative current collector material is copper foil, copper mesh, stainless steel mesh, and other metal mesh; The negative current collector material is generally copper foil (10 μ m～20 μ M thick). Copper foil, as a non-ferrous metal foil material, is mainly required for the negative current collector of lithium batteries, with the following three technical indicators: (1) thickness (8 μ m～12 μ m)； (2) Tensile strength (>30kg/mm2); (3) Elongation rate (>5%)

8. Positive electrode current collector material: The positive electrode current collector material is aluminum foil, etc; The positive electrode current collector material is generally made of aluminum foil (20 μ M thick).

9. Conductive agent: Due to the low conductivity of active materials, conductive agents are generally added to accelerate electron transfer and effectively improve the migration rate of lithium ions in electrode materials. The commonly used conductive agents are graphite, carbon black, acetylene black, and colloidal carbon.

10. Battery case: The battery case is made of steel, aluminum, and other materials.