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Lithium battery positive and negative plates

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.

 

 
 
 

5.Pole production process - coating & rolling

5.1. Coating

 

Coating method: The slurry is squeezed and sprayed along the gap of the coating mold at a certain pressure and flow rate and transferred to the substrate.

 

Coating purpose: to evenly coat the slurry on the substrate to ensure the uniformity of the slurry coating;

Control points:

 

1.The slurry is evenly coated, otherwise the battery cell consistency is poor, lithium is deposited, and the performance does not meet the standards;

 

2.The coating size is accurate and without misalignment, otherwise the capacity fluctuation range is large and the capacity is insufficient;

 

3.The coating slurry does not contain oversized particles, otherwise it will pierce the diaphragm and cause the battery cell to short-circuit.

 

5.2. Roller pressing

Rolling method: Through the rotation of two steel round rollers, the pole piece is rolled up in a fixed direction and pressed to the specified thickness;

 

Rolling purpose:

 

1. Ensure that the surface of the electrode is smooth and flat to prevent the burrs on the coating surface from piercing the diaphragm and causing a short circuit;

 

2. Compact the pole piece coating material to reduce the volume of the pole piece to increase the energy density of the battery;

 

3. Enhance the bonding strength between the coating material and the current collector, and reduce the occurrence of powder loss of the battery pole during the cycle;

 

4. Make the active material and conductive agent particles contact more closely and improve the electronic conductivity;

 

Key points for control: Control the thickness of the rolled electrode. If the thickness exceeds the upper limit, the purpose of rolling cannot be achieved, and powder will fall off. If the thickness exceeds the lower limit, the electrode will be crushed and the electrolyte cannot penetrate.

 

6.Canrd Brief Introduce

Canrd use high battery R&D technology(core members are from CATL) and strong Chinese supply chain to help many foreign companies with fast R&D. We provide lab materials, electrodes, custom dry cells, material evaluation, perfomance and test, coin/pouch/cylindrical cell equipment line, and other R&D services.

Email： contact@canrd.com    Phone/Wechat/WhatsApp： +86 19867737979

Canrd Official Web     Canrd Company Vedio     Canrd Company profile

Website : www.canrud.com

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