As a carrier that conducts electrons and carries active materials inside a lithium-ion battery, the current collector plays an important role in the final performance of the battery cell. Aluminum foil is the most commonly used cathode current collector. In order to improve the rate, cycle and service life of the electrode, some conductive coatings are coated on the surface of the aluminum foil, which can effectively improve the interface contact resistance between the current collector and the active particles, and improve the relationship between the active material and the current collector. The bonding strength reduces the problem of active particle peeling during electrode cycling. The coating of carbon-coated aluminum foil generally includes conductive carbon black, graphene, carbon nanotubes, etc. The formula of the carbon coating layer, coating thickness, coating uniformity, etc. will also affect the primer effect.
This article uses the pole piece resistance test method to compare the resistance differences of carbon-coated aluminum foils with different formulas and different coating thicknesses, and analyze the uniformity of the undercoated pole pieces.
In short, adding an effective intermediate layer between the active material and the metal current collector not only improves the interface contact resistance, but also has the following potential synergistic benefits:
(1) The chemically and electrochemically stable conductive layer can serve as an effective diffusion barrier to prevent the diffusion of oxygen produced due to side reactions during electrolyte decomposition and/or lithium ion intercalation reactions, effectively preventing the formation on the surface of metal current collectors. oxide layer, thus preventing degradation;
(2) The conductive layer with a reasonable formula has good conductivity and can form a large area of contact. The interface resistance between the current collector and the active coating is low, which is conducive to the rapid charge transfer process;
(3) The flexibility and mechanical buffering of the conductive layer can enhance the adhesion of the physical interface, thereby minimizing problems related to the gradual loss of contact area caused by the stress generated at the interface during long-term cyclic reactions. By designing and developing unique conductive coatings, experiments have proven that conductive interface layers can significantly improve electrochemical properties, such as specific reversible capacity, capacity retention, rate performance, etc.
