Although using aluminum foil as a battery current collector has many advantages, there are still a series of problems that need to be addressed during application. First, the certain rigidity of the aluminum foil results in a limited area when in contact with the cathode material, which in turn affects the internal resistance of the cathode sheet; secondly, the bonding strength of the aluminum foil to the binder and active material is limited, and the electrode volume changes during cycle charge and discharge. The particles are loosely combined and easy to fall off, which accelerates the rapid attenuation of battery capacity and cycle life; finally, the oxidative decomposition products of the electrolyte trigger an electrochemical reaction on the surface of the aluminum foil, causing corrosion of the aluminum foil. To overcome these problems, aluminum foil must be modified.
Surface carbon coating is the main modification treatment method, which can significantly improve the internal resistance of aluminum foil. The main modification methods of aluminum foil include surface treatment (such as chemical etching, electrochemical etching, DC anodization, corona treatment), conductive coating (such as surface carbon coating, graphene coating, carbon nanotube coating, composite coating), 3D porous structure (such as foam structure, nanoribbon structure, nanocone structure, fiber braiding structure) and composite modification treatment. These methods play a key role in improving the performance of aluminum foil and enhancing the connectivity of electrode materials.
The new composite aluminum foil demonstrates excellent comprehensive performance in terms of safety, energy density and cycle life in the battery field. Composite aluminum foil refers to an aluminum-plated composite film prepared by evaporation process and using polyethylene terephthalate (PET) and other materials as the base material. Its advantages include: 1) Improved safety: The composite aluminum foil introduces an organic insulating layer in the middle of the current collector. This layer can provide infinite resistance when thermal runaway occurs, and is non-combustible, thus effectively reducing the risk of battery fire and explosion, significantly reducing the risk of battery fire and explosion. To improve the safety of the battery; 2) Improve the energy density: Because the PET material is lighter, the overall mass of the PET aluminum foil is smaller (equivalent to replacing the middle part of the metal foil with a layer of PET), which reduces the weight of the battery and improves the battery's energy density. Energy Density. According to Xinchen Lithium Battery data, the composite aluminum foil is 50%-80% lighter than the traditional rolled aluminum foil current collector without increasing the overall thickness. Moreover, the composite aluminum foil can be thinner, and the final lithium battery is smaller in size. , the energy density can be increased by 5%-10%; 3) Improved cycle life: According to Gaogong Lithium Battery, the composite aluminum foil uses polymer materials to form a layered annular sponge structure, which can absorb the active material layer of the pole piece produced during the charging and discharging process. Expansion-contraction stress caused by lithium ion intercalation and extraction. This effectively maintains the long-term integrity of the pole piece interface, increasing cycle life by 5%.
