Good flexibility
- PET base film conductivity relies on the surface of the metal, the middle of the polymer material has better flexibility compared to metal; this is because the physical properties of the composite material are in the middle (such as polymer flexibility to 100, metal flexibility is 50, then the flexibility of the two composite materials can reach 75), so the composite fluid PET also has better flexibility, more practical.
High compressive strength
- Mainly to measure the tension performance, collector fluid in the production process of the battery needs to go through the "shrink roll pulling and releasing" process, in this process needs to bear greater tension, and polymer compressive strength is also better than the metal, so the tensile strength of composite materials will be better than pure metal, meaning that the compressive strength is improved, can be used in the production of This means that the compressive strength is improved and the production process can use greater tensile strength to improve the production efficiency; battery factories are now expanding their new production lines, so if they use PET material, they can speed up the original production line.
low density, low weight, high specific capacity
- In order to improve the energy density of the battery, one can directly improve the material energy, and the second is to reduce the weight of the material, the active material of the battery is nano-level, and the collector fluid thinning can make the electrical energy release more uniform, about 1GWh of battery need positive and negative collector fluid of 10 million square meters each, so the area ratio is fixed, the best collector fluid of the current lithium system is aluminum and copper, the material is relatively fixed, the density will not change. Density will not change, but can only be reduced through the thickness to reduce the volume, and reduce weight, to achieve greater energy density. Therefore, the PET collector provides a two-pronged approach to increase battery energy density without sacrificing load-bearing capacity, safety, and cycle life reduction by excessive thinning.
The weight of PET composite copper foil is lighter, and the proportion of collector to battery weight is 15% at present. PET technology can improve the energy density of battery cells by 5%-10% and achieve high specific capacity.
Good homogeneity
- Two problems will be encountered in the conventional production process, one is the uniformity of the performance of both sides of the film. From the process point of view, the coating needs to use a binder of active substances to stick it on the surface of PET film and then go through a rolling process, which can ensure the uniform thickness of the surface and no pits and pits to prevent peeling. Another is the asymmetry of contact resistance. The resistance of the active material is not the same as copper, some places are more, and some places are less so that the uneven energy will affect the overall discharge, which in turn will affect the cycle life and accelerate the decay of the battery. As you can see, the current preparation of copper foil is processed with single-sided gross, double-sided gross, and surface roughening, indicating that the front and back sides of the copper foil are not the same and there is a problem of unevenness.
PET collector is processed in this problem. First of all, the PET material itself is more uniform on both sides, and in the process of coating the active material, we mainly use aspects including physical deposition and water plating to achieve a more uniform surface. Due to the more uniform surface of PET, the polymer material has a lower swelling rate, is easier to vacate, maintains surface integrity, and has the advantage of long life.
High safety
- Battery spontaneous combustion is due to internal short circuits caused by uncontrolled heat generation. The structure of the battery is that the positive and negative poles are metal, and there is a layer of the diaphragm in the middle, the metal material will be fatigue fracture due to repeated use, and the metal material will form small spikes at the edge after fracture, the direction of the small spikes is random, it is easy to squeeze on the diaphragm and pierce the diaphragm, the positive and negative poles are added together, and the active material for releasing electricity is in the electrolyte, the liquid form plus the power battery is bumped in the electric vehicle It is easy to occur internal short circuit, releasing a lot of heat. The solution of PET copper foil to this problem is that the polymer is not easy to break, even if it breaks, the strength of 1-micron copper plating cannot reach the standard of piercing the diaphragm, so the risk of internal short circuits is avoided.
Low cost
- According to the current copper price, we estimate that the unit production cost of composite copper foil after the mass production is about 3.1 yuan/m2, which is lower than the cost of electrolytic copper foil, and with the technological progress of equipment, there is still more room for cost reduction.
