Battery adhesive performance requirements and characteristics

Lithium battery paste is a complex multiphase mixed non-Newtonian fluid. The positive electrode slurry is composed of an active material, a conductive agent, a binder, and a solvent. Lithium battery cathode materials currently on the market include lithium cobaltate, lithium manganate, lithium iron phosphate, and ternary materials. The conductive agent mainly includes carbon black, carbon nanotubes, conductive graphite and the like. The binder is divided into a water system and an oil system. The binder, the corresponding solvent is water-based deionized water and oil-based NMP solvent.
The negative electrode slurry is prepared by mixing a multiphase material such as an active material, a conductive agent, a binder, a thickener, and a solvent deionized water. The active material of the negative electrode is mainly various types of graphite, silicon carbon negative electrode, and the conductive agent is similar to the positive electrode conductive agent (carbon black, carbon nanotube, VGCF, etc.). At present, the negative electrode binder on the market generally selects an environmentally friendly anhydrous binder. Such as CMC, SBR, LA132 and so on. When the anode material is lithium titanate, a binder is usually selected from the oil-based PVDF, and NMP is used as a solvent.
The active material, the conductive agent and the solvent have no adhesion to the metal electrode, so the pole piece cannot be made into a lithium battery. The binder is an important component of the slurry which bonds the various particles together to form an adhesive paste that is tightly bonded to the metal foil. A good binder not only helps to increase the energy density of the battery, but also has a significant effect on the internal resistance of the battery, and also has an important influence on the electrochemical performance of the battery.
The performance requirements of battery adhesives from the perspective of pole piece processing are mainly:
The viscosity of the slurry can be maintained for a long time. It does not cause settling and damage due to the placement of mud.
It can be dissolved to form a high concentration solution, and the required heat of vaporization is very low.
It is easy to form when rolling and does not rebound.
It has the flexibility to form no fragments when the electrode breaks.
The binder is not only related to the manufacturing process of the lithium battery, but also has an important influence on the electrochemical performance of the lithium battery. From a battery performance point of view, the battery binder must have the following characteristics:
Can maintain the state of the creature well.
It has good adhesion to metal foil and does not peel off the metal foil due to electrolyte and charge and discharge.
Good electrochemical stability over a wide voltage range.
Has a higher melting point and a lower swelling ratio. Even at high temperatures, the bonded structure of the binder and the active material needs to be kept stable. The binder usually has a swelling phenomenon. When the swelling exceeds a certain level, the electrical conductivity between the active material and the current collector is affected, and the battery capacity is attenuated, so it is necessary to control the degree of swelling.
Has good ion transport and electronic conductivity.