Sep 28,2022.
In electrodes, binders are polymer compounds used to adhere electrode active materials to current collectors. Its main function is to bond and maintain the active material, enhance the electronic contact between the electrode active material and the conductive agent and the active material and the current collector, and better stabilize the structure of the pole piece. For the positive and negative electrodes of lithium-ion batteries that expand and contract in volume during charging and discharging, the binder is required to play a certain buffering role. To choose a suitable lithium-ion battery binder, it is required that its ohmic resistance should be small, its performance is stable in the electrolyte, and it will not expand, loosen, or remove powder. Generally speaking, the performance of the binder, such as adhesion, flexibility, alkali resistance, hydrophilicity, etc., directly affects the performance of the battery. By adding the optimal amount of binder, larger capacity, longer cycle life and lower internal resistance can be obtained, which can promote the improvement of battery cycle performance, rapid charge and discharge capability, and reduction of battery internal pressure. . Therefore, it is very important to choose a suitable binder. 1. The role and performance of the adhesive (1) Ensure the uniformity and safety of the active substance during pulping; (2) It has a bonding effect on the active material particles; (3) bonding the active material on the current collector; (4) Maintain the bonding between active substances and between current collectors; (5) It is beneficial to form the SEI film on the surface of the carbon material (graphite). 2. Performance requirements for adhesives (1) It can maintain thermal stability when heated to 130-180℃ during drying and dewatering; (2) can be wetted by organic lithium battery electrolyte; (3) It has good processing performance; (4) Not easy to burn; (5) It has relatively high electronic ion conductivity; (6) The dosage is small and the price is low; In lithium-ion batteries, due to the use of organic electrolytes with low electrical conductivity, the electrode area is required to be large, and the battery assembly adopts a roll structure. The improvement of battery performance not only puts forward new requirements for electrode materials, Also, new requirements are placed on the adhesives used in the electrode manufacturing process. At present, polyvinylidene fluoride (lithium battery material PVDF) is widely used in industry as a binder for lithium-ion batteries, and N-methylpyrrolidone (NMP) is used.
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