NMP Overview lithium excipients subdivision

1. Basic introduction of NMP
NMP, full name N-methylpyrrolidone, molecular formula C5H9NO, a colorless transparent liquid, is one of the most commonly used lithium battery accessories. When making electrode sheets, NMP is used as a solvent to fuse various materials required for electrodes, such as binder, positive active substance, conductive agent, etc., so that the binder is fully in contact with other substances and evenly distributed. As a high-boiling solvent with excellent properties, NMP is completely mixed with almost all solvents (ethanol, acetaldehyde, ketones, aromatic hydrocarbons, etc.).

NMP products have the characteristics of high boiling point, strong polarity, low viscosity, strong dissolution ability, no corrosion, little toxicity, strong biodegradation ability, low volatility, excellent chemical stability and thermal stability.
NMP is a special chemical product, according to metal impurities, control particle size, particle number and application range is divided into four grades, respectively, micro electrical grade, electronic grade, pharmaceutical grade and industrial grade. Among them, the micro-electric level requires the highest level, which is used in the cleaning of photoresist and liquid crystal packaging in integrated circuits; The electronic grade can be used in new materials such as lithium-ion batteries and aramid.
NMP is still in the growth stage in the domestic market, especially with the rapid development of the new energy vehicle market, which will promote the steady growth of the market demand for NMP.
Second, NMP industrial chain analysis
Upstream:
The upstream industry of NMP is the coal chemical industry, which provides NMP with raw materials based on BDO. BDO (1, 4-butandiol) is a common chemical raw material in coal chemical industry and petrochemical industry. With the adjustment of national macroeconomic policies and the integration of resources in China’s coal chemical industry, BDO industrial technology is becoming more and more mature, and its production capacity is growing rapidly and expanding.
Midstream:
NMP industrialization time is long, the technology is mature, its production process mainly has two kinds: one is the synthesis process, from 1,4 butanediol (BDO) dehydrogenation to produce gamma-butanolactone (GBL), and then gamma-butanolactone and monomethylamine amination reaction to produce crude products, then distillation and purification to finished NMP; The second is the distillation and purification process, the NMP waste liquid used by the power battery manufacturer is recycled to the NMP manufacturer, NMP is mainly through physical purification, and the new NMP solution is produced after the loss of about 10%, and a part of the new liquid may also be added for blending.
The current production process of NMP has developed into a reliable and mature process production route, and the process methods of several major manufacturers at home and abroad are not much different, and a few differences are mainly reflected in the use of dehydrogenation catalysts and the details of rectification fillers.
Downstream:
NMP is a very important auxiliary material for the production of lithium-ion battery electrodes, and is the most commonly used solvent in the batching process of lithium-ion batteries. NMP is used to dissolve the positive binder PVDF, and as the diffusion liquid of carbon nanotube conductive slurry (CNT) for lithium batteries, respectively affecting the coating quality/effect, improve the energy density of lithium batteries, with high boiling point, outstanding solubility, low volatility, strong selectivity, good thermal stability, strong moisture absorption and other characteristics. Generally, NMP accounts for 3%-6% of the manufacturing cost of lithium batteries.
Third, what role does NMP play in lithium-ion battery production
NMP is a very important auxiliary material for the production of lithium ion battery electrodes, the most commonly used solvent in the first part of the lithium ion battery dosing process, scientific name N-methylpyrrolidone, molecular formula C5H9NO, is one of the most commonly used lithium battery auxiliary materials.
Usually, lithium auxiliary materials mainly include solvents and binders, the main role of the solvent is to dissolve positive and negative active substances, and the main role of the binder is to bond the active substances on the fluid collector, the amount of auxiliary materials is generally 2%-5%, compared with the positive, negative, electrolyte and diaphragm, the cost is relatively small, but the role can not be ignored.
PVDF (polyvinylidene fluoride) is the most commonly used positive electrode binder, NMP is the most commonly used solvent, and the two are usually used together.
NMP can be miscible with water, PVDF, positive and negative electrode materials, so it is widely used in the preparation of lithium batteries. When making electrode sheets, NMP, as a solvent, can fuse the binder, positive active material, conductive agent and other materials required for electrodes together, so that the binder is fully in contact with other substances and evenly distributed.
In the batching stage: as a PVDF solvent, participate in the dispersion of the slurry, forming a uniform medium and a stable slurry within a certain viscosity range for a long time.
In the coating stage: as the main liquid carrier of the slurry, it is evenly coated on the metal substrate with a stable thickness, which requires very good wettability and fluidity of the metal substrate.
In the coating and baking stage, the wet film runs at a constant speed in the oven, the solvent volatilizes regularly, NMP performs the function of poremaking, and NMP volatilizes from the wet film at a stable speed to form a porous microelectrode structure with uniform pore size and uniform distribution.
Therefore, the quality of NMP will directly affect the quality of lithium ion battery pulping coating.