Application Advantages and Control Points of Microporous Copper Foil Aluminum Foil in Lithium Batteries

As we all know, regardless of 3C digital batteries or new energy vehicle power batteries, the requirements for contrast energy and charge and discharge rate performance are getting higher and higher. **The national subsidy policy stipulates that the energy density of the pure electric bus system is greater than 95 watt-hours/kg, in order to get the threshold of 100% national compensation and 95 watt hours, it is estimated that many R&D personnel of lithium iron phosphate battery manufacturers It’s full of face, “What about the difference of 5 watts/kg? Come to a few pieces of tender tofu, I will go~~~ I will go~~”.

Closer to home, the way to improve the specific energy of lithium-ion batteries is to use higher-capacity positive and negative materials, thinner diaphragm paper, thinner copper foil aluminum foil, and reduce other auxiliary additives as much as possible. See below:

The focus of research and development is undoubtedly on the positive and negative materials of higher gram capacity (total weight accounted for more than 50%). Lithium iron phosphate has no potential to be dug, and the ternary is on the way to the high nickel (nickel-cobalt-manganese 111-523-622-811-NCA?), but the safety is the Damansley sword hanging in the air, there are always It may pierce the heart of the lithium battery enterprise. Every time you go forward, the sweat and cold sweat alternate, and the brothers who do the ternary research and development are really hard.

In terms of the negative electrode, we can only passively wait for the maturity of the silicon-carbon material. What should I do if the expansion coefficient of silicon-carbon is too high? What should I do if I have a short life? I have heard a wow------- and there is a trick to use a thinner diaphragm. Paper! But the diaphragm only accounts for 4~5% of the weight of the battery. If the diaphragm is too thin, the risk of short circuit between the positive and negative electrodes will increase, and the result will often be worth the loss.

At this stage, the thickness of conventional copper foil used in the production of lithium-ion batteries is 8μm~12μm (the copper foil for 3C digital battery has been used 6~7μm copper foil), and the thickness of aluminum foil is 12μm~20μm, which is used as the positive and negative conductive substrate. The weight of the ion battery is 15%~20%. How to further reduce the weight ratio of copper and aluminum foil to increase the specific energy? Therefore, the microporous copper foil aluminum foil is born under such environmental stimulation, and it is born! B blows up?)

Existing specifications of microporous copper foil aluminum foil (Machining method to make holes, maintaining the original physical properties of the foil, coating is not broken, 0 burrs are not leaking):

1. What are the advantages of microporous foil in the application of lithium ion batteries? (taking microporous foil with a porosity of 17% as an example)

1. Directly and effectively increase the specific energy of the lithium battery;

The foil of the same specification, the microporous foil with a porosity of 17%, the weight is reduced by 17%; the same areal density, the positive and negative compaction is improved (some materials are filled into the pores).

2. Effectively improve the performance of lithium battery rate;

In the lithium battery of conventional foil, the migration of lithium ions diffuses into the tip end of the foil through the two-dimensional direction of the foil. After the through-hole of the foil, the diffusion path of lithium ions can be converted into stereoscopic omnidirectional penetration, and can enter through the pores. The contact surface between the positive and negative materials and the foil increases, the lithium ion migration radius is reduced, and the conductivity is improved. (Personal opinion that the bottleneck of lithium ion rate performance is not in the conduction of electrons, but in the efficiency of lithium ion transfer, such as the effect of porous Ketchen carbon black on the rate-type battery is more effective than the non-porous conductive agent. it is good)

3. Effectively reduce the internal resistance of the lithium battery;

The comparison of the same foil shows that the use of punched copper foil and aluminum foil can effectively reduce the internal resistance by 8% to 20%.

The theoretical basis is presumed to be due to the double effect of the increase in the contact surface between the conductive foil and the positive and negative electrodes, and the decrease in the internal resistance of the foil itself. (uncertain)

The personal point of view is that if the thickness of the positive and negative pole piece coating is smaller than the radius of the micropores of the foil, the internal resistance will increase, and vice versa, the internal resistance will decrease. The contact distance between the outermost lithium ion of the coating and the surface of the foil is related to the rate performance. In the cell design, the surface density is high, and the performance of the rate performance may be lower. (welcome industry friends to discuss)

4. The infiltration efficiency of the lithium battery electrolyte can be greatly improved after injection, and the infiltration consistency can be ensured 100%.

In the lithium battery of the conventional foil, the electrolyte diffuses and diffuses from the longitudinal direction to the center, and after the drilling, it is a three-dimensional diffusion and diffusion, completely eliminating the problem that some of the battery poles are not infiltrated at the center. One of the reasons for the lack of consistency in the feedback cell cores in the industry is caused by the consistency of the infiltration.

5. The surface adhesion of the foil material is improved. Through the material between the pores, the positive and negative pole coatings of the positive and negative pole pieces form a "work" type occlusion state, and the probability of the pole piece falling off can be greatly reduced.

6, improve the bending softness of the pole piece, more suitable for flexible battery applications. (The company has been used in batches to make wearable lithium batteries, and the performance has improved significantly)

7, other advantages, still need users to further explore.

Second, the control points of microporous copper foil aluminum foil on lithium ion battery

1. Coating anti-leakage;

During the coating process, the microporous copper foil aluminum foil should prevent the slurry from being too low in viscosity, causing the slurry to leak from the pores of the foil during the extrusion coating process. The foils with different pore sizes and porosity have different viscosity requirements for the slurry. . Taking a microporous aluminum foil with a porosity of 17% and a pore diameter of 0.35 mm as an example, the test shows that the viscosity of the positive electrode material is about 8000, ** should not be lower than 6000, and the transmission speed needs to be properly adjusted during the extrusion coating process. (The slurry is allowed to stand for too long, and it is easy to infiltrate to the other side. Rapid flooding can be solved)

2. The burr control of the pole piece cutting;

Finally, I hope that my friends who have completed microporous copper foil or aluminum foil for lithium-ion battery experiments can share data and communicate.

Another: Microporous copper foil is used for lithium capacitors, supercapacitors, nickel-cadmium, nickel-metal hydride batteries, the performance improvement is very obvious, the reason for the non-scale promotion is the cost. The machining method is used to make holes, and the production efficiency is extremely high. It is expected that the cost after mass production is limited compared with the conventional double-light copper foil (the estimated final price is around 130,000/ton).