What role does NMP play in lithium batteries? How do you tell the mass of NMP?

According to BDO Research Institute, NMP is a polar solvent with strong selectivity and good stability, with high boiling point, strong solubility, good stability, biodegradable, recyclable and other characteristics. It is widely used in lithium battery, polymer materials, electronics, cleaning agents, medicine, pesticides, pigments and other industries, among which the lithium battery industry has the largest application scale of NMP.

Lithium-ion battery is a device that converts chemical energy into electric energy by embedding and deembedding lithium ions back and forth between positive and negative electrodes. It is mainly composed of five parts: positive electrode, negative electrode, diaphragm, electrolyte and battery shell. The positive electrode is the core part of lithium-ion battery and the key component that determines battery performance. It has a direct impact on the final energy density, voltage, service life and safety of the product, and is also the most expensive part of lithium battery, accounting for more than 40% of the cost of lithium battery.

When preparing the positive electrode of the battery, it is necessary to carry out slurry preparation, coating, drying and other key links. NMP is the mainstream solvent for the positive electrode coating of lithium ion batteries because of its strong dissolution ability, low corrosion, good stability and other advantages. At the same time, because NMP has a high boiling point and is easy to condense, the waste gas containing NMP can be condensed and recovered after drying, and then used after distillation and purification. The uses of NMP in each link are as follows:

a. Slurry preparation: NMP, as the solvent of binder (PVDF), mixes, dissolves, agitates and disperses various electrode materials such as binder, conductive agent and positive active substance to form uniform slurry. The dispersion quality of slurry directly affects the quality and performance of lithium-ion battery.

b. Coating: It is the next process after the preparation of the slurry. The slurry with good stability, high viscosity and good fluidity is evenly coated on the positive metal foil. As the liquid carrier of the slurry, NMP is the mainstream solvent for coating. The coating process is of great significance to the capacity, service life and safety of lithium ion batteries.

c. Drying: After coating, the positive electrode sheet is baked and dried in a vacuum dryer at a baking temperature of 120±5 degrees Celsius. NMP in the electrode paste is removed, so that the adhesive, conductive agent and positive electrode material in the paste form a porous film with uniform aperture and distribution, which is covered on the electrode sheet.

Therefore, NMP as a solvent participates in the core of lithium battery production, and its quality directly affects the coating quality of lithium battery. With the rapid expansion of power and energy storage batteries, the demand for NMP in lithium battery industry increases sharply, which brings space for the expansion of NMP production.

NMP is a common solvent for cathode materials of lithium ion batteries and a necessary solvent for carbon nanotubes, a new conductive agent. According to the data of the research report, 1700 tons of NMP are needed for the production of lithium batteries per GWh. It is understood that the demand of NMP is expected to exceed 2 million tons by 2025, and the future development prospect of NMP market is broad.

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