1. What is the coating substrate?
In lithium-ion batteries, the positive and negative active materials are coated on the substrate to make the pole pieces, which are then wound or stacked to form the battery cell. The substrates used here are mainly copper foil and aluminum foil. The current lithium battery positive electrode is aluminum foil and the negative electrode is copper foil. This is because copper is easily oxidized at the positive electrode with a higher potential. At the same time, there is a dense oxide layer on the surface of the aluminum foil, which protects the internal aluminum at high potential.
2.What is the electrolyte for injection?
Lithium battery electrolyte is the carrier of ion transmission in the battery, generally composed of lithium salt and organic solvent.
3.What are the positive and negative active materials of lithium batteries? What is the difference between positive and negative active materials?
The mainstream positive and negative electrode materials of lithium batteries in new energy vehicles are mainly divided into the following types according to different battery types:
3.1. Ternary lithium battery
Positive electrode material: Lithium nickel cobalt manganese oxide ( Li(NiCoMn)O2 ), which is mainly composed of nickel, cobalt and manganese. Increasing the nickel content can improve the battery life, increasing the cobalt content can improve the battery stability, and increasing the manganese content can enhance the battery safety;
Negative electrode material: mainly graphite, which has a multi-layer structure and can accommodate the lithium atoms of lithium batteries.
3.2. Lithium iron phosphate battery
Positive electrode material: lithium iron phosphate ( LiFePO4 ), this positive electrode material has an olivine structure and is very chemically stable, so lithium iron phosphate batteries are very safe;
Negative electrode material: Like the ternary lithium battery, the negative electrode material is mainly graphite to accommodate lithium atoms.
3.3. Lithium cobalt oxide battery
Positive electrode material: Lithium cobalt oxide LiCoO2, which is gray-black powder in appearance, has the characteristics of high cost, high energy density and poor safety;
Negative electrode materials: soft carbon and hard carbon, good compatibility with the electrolyte, low output voltage, and no obvious charging and discharging platform potential.
3.4. Lithium manganese oxide battery
Positive electrode material: Lithium manganate LiMn2O4 , usually black-gray powder, easily soluble in water, with the advantages of low price, no pollution and high safety;
Negative electrode material: graphite, which has good conductivity and a layered structure suitable for the embedding and de-embedding of lithium atoms.
3.5. Differences
In addition to the different raw materials used, the biggest difference between the positive electrode material and the negative electrode material lies in the different potentials. The potential of the positive electrode material is higher, and the potential of the negative electrode material is lower. Only in this way can a potential difference be formed at both ends of the battery and the effect of energy storage and discharge can be achieved.
4.Ultra-thin composite copper foil
Ultra-thin composite copper foil is a new type of negative electrode material for lithium battery current collector. Compared with traditional electrolytic copper foil, composite copper foil has the advantages of low cost, high safety and high energy density. As lithium batteries develop towards high energy density and high safety, lithium battery copper foil is developing towards thinner, microporous, high tensile strength and high elongation.
Ultra-thin composite copper foil is a new type of lithium battery copper foil material made of a sandwich structure of "metal copper layer - polymer support layer - metal copper layer". Magnetron sputtering is used on the surface of PET/PP substrates with a thickness of 2-4.5um to coat a 20-70nm copper film on both sides with a square resistance of about 0.5-2Ω to achieve film surface metallization. Then, the copper film is thickened to 1um by water electroplating, and a 6-8um composite copper foil is used to replace the 4.5-9um electrolytic copper foil.