What are the advantages of using laser-perforated foil in lithium-ion batteries?

Lithium battery is the green energy question in the charging energy storage in the 21st century. It has the advantages of high voltage, high energy density, good cycle performance, small discharge and no memory effect. It has developed rapidly in the past 10 years. In the field of mobile electronic terminal equipment such as laptops, mobile phones, cameras, weapons and equipment, it is considered to be an important high-tech industry for the national economy and people's lives in the 21st century.

Using higher capacity positive and negative electrode materials, thinner separator paper, thinner copper foil and aluminum foil is a method to improve the specific energy of lithium-ion batteries, with the principle of minimizing other auxiliary additives.

1. What are the advantages of using laser-perforated foil in lithium-ion batteries?

1. The specific energy of lithium batteries is directly and effectively improved;

(For the same specification of foil, the microporous foil with a porosity of 17% has a 17% weight reduction; the surface density is the same, and the positive and negative compaction increases the part of the material filling the pores).

2. Effectively improve the rate performance of lithium batteries;

In traditional foil lithium batteries, the migration of lithium ions diffuses to the extreme ear end through the two-dimensional direction of the foil. After the foil is perforated, the diffusion path of lithium ions can be transformed into a three-dimensional full penetration. The migration radius of lithium ions can be reduced by increasing the contact surface between the positive and negative electrode materials and the foil, and the conductive efficiency can be improved. (Personally, the bottleneck of lithium-ion rate performance is not electron conduction, but the transfer efficiency of lithium ions.

3. Effectively reduce the internal resistance of lithium batteries;

Comparison of the same foil shows that the use of punched copper foil and aluminum foil at the same time can effectively reduce the internal resistance by 8%~20%.

Theoretically, it is speculated that the contact area between the conductive foil and the positive and negative electrodes is increased, and the internal resistance of the foil itself is reduced. (Not necessarily)

Personally, I think that if the thickness of the positive and negative electrode coating is smaller than the micropore radius of the foil, the internal resistance will increase, otherwise the internal resistance will decrease. The contact distance between the lithium ions outside the coating and the foil surface is related to the rate performance. In battery design, if the surface density is high, the rate performance may be lower.

4. After injecting the lithium battery electrolyte, the wetting efficiency can be greatly improved, and the wetting consistency is 100% guaranteed.

For traditional foil lithium batteries, the electrolyte diffuses from the longitudinal direction to the center, and drilling is a three-dimensional penetration diffusion, which completely eliminates the problem that the center of some battery chips cannot penetrate. In the industry, one of the reasons for the insufficient consistency of individual batteries is the penetration consistency.

5. Improve the surface adhesion of the foil. Through the material between the pores, the positive and negative sides of the positive and negative electrode coatings form an industrial bite state, which greatly reduces the probability of pole shedding.

6. Improve the bending softness of the pole piece, which is more suitable for the use of flexible batteries. (Existing companies mass-produce wearable lithium batteries, and the performance is significantly improved)

7. Users still need to further explore other advantages.

2. Control points for laser microporous copper foil and aluminum foil for lithium-ion batteries.

1. Leakage prevention of coating;

During the coating process of laser microporous copper foil and aluminum foil, the viscosity of the slurry should be prevented from being too low, which will cause the slurry to leak from the foil holes during extrusion and spraying. The pore size is different. The foil with different porosity has different requirements for the viscosity of the slurry. Take the microporous aluminum foil with a porosity of 17% and a pore size of 0.35mm as an example. The test shows that the viscosity requirement of the positive electrode material is about 8000, and the minimum is not less than 6000. During the extrusion and spraying process, the transmission speed needs to be adjusted appropriately. (If the slurry is left standing for too long, it is easy to penetrate into the other side in small amounts, which can solve the problem of rapid drying.

2. Pole segmentation burr control;

Finally, I hope that colleagues who have completed the microporous copper foil or aluminum foil experiment of lithium-ion batteries can share data and communicate together.

In addition, the performance of lithium capacitors, supercapacitors, nickel-cadmium and nickel-metal hydride batteries using laser microporous copper foil has been significantly improved. The reason for not being promoted on a large scale is the cost issue. The use of mechanical processing holes has extremely high production efficiency.