Battery foil is becoming well-known to the public as an independent aluminum foil variety. Lithium aluminum foil is used as a collector for lithium-ion batteries, which can be divided into power lithium battery foil, consumer battery foil, and energy storage battery foil. Currently, the demand for power lithium battery foil is the highest, and the consumer battery aluminum foil market is basically saturated. In the future, the proportion of demand for aluminum foil for power lithium batteries will further increase, and aluminum foil for energy storage batteries will also gradually increase.
Aluminum foil is the main positive current collector for commercial lithium-ion batteries. The conventional aluminum foil positive electrode current collector has some problems, such as the contact impedance at the interface between the rigid aluminum foil and the positive electrode active unit, and the high internal resistance at the interface with the active substance; The bonding with the positive electrode active unit is weak, and the volume of the electrode constantly changes with the charging and discharging process. The particulate matter is prone to powder shedding, thereby accelerating the attenuation of capacity and lifespan; The products of electrolyte oxidation and decomposition will undergo electrochemical reactions on the aluminum foil, leading to accelerated corrosion of the aluminum foil. For this reason, people have carried out research on the modification of aluminum foil, including chemical etching, electrochemical etching, DC anodic oxidation, corona treatment and conductive coating substrate surface carbon coating (Graphene coating, carbon nanotube coating and composite coating) and other modification methods.
With the development of the lithium battery industry, customers have increasingly higher requirements for the surface quality of lithium battery aluminum foil, especially for the surface wetting tension.
Factors affecting the surface wetting tension value of aluminum foil
Reason analysis: In the production process of lithium battery aluminum foil, the viscosity of rolling oil and the ratio of additives can affect the surface oil content of lithium battery aluminum foil. That is, the oil content on the surface of lithium battery aluminum foil directly affects the dyne value when the finished product is taken offline.
Comparison of aluminum foil before and after corona treatment:
As shown in Figure 1, the dyne values of different foil materials tested with dyne pens are as follows: normal aluminum foil (30), normal copper foil (30), 2000W corona aluminum foil (34), 2500W corona aluminum foil (34) from left to right. The highest dyne value we can test for corona aluminum foil can reach (66). From the measured dyne values, it can be seen that the surface tension of the foil material is: corona aluminum foil>normal aluminum foil
Comparison of aluminum foil before and after corona treatment
Due to the significant improvement in surface roughness of the aluminum foil after corona treatment, more adhesive can penetrate into the surface voids, eliminate the air adsorbed on the interface, and generate bonding effect. For the material treatment surface, we often use dyne water to apply it to the treatment surface for identification. Of course, butanone or distilled water can also be used to achieve the same effect.
Changes after corona treatment
surface topography 
Corona treatment can increase the surface roughness of aluminum foil. The main reasons for the increase in surface roughness after corona treatment are: (1) the erosion effect of plasma gas generated during corona discharge; (2) The ozone generated by discharge oxidizes some surface molecules into low-level small molecules and evaporates them; (3) The etching effect of plasma causes the weak physical binding on the material surface to dissipate, while the broken molecular chains combine with each other to form "peaks" and "valleys".
Surface generated free radicals
Corona treatment has a certain destructive effect on the surface structure of aluminum foil materials. After corona modification, the introduction of