Technology | What role does NMP play in lithium batteries?

What are NMPs?

NMP is a very important auxiliary teaching material for the production and development of working electrodes of lithium-ion power batteries nmp solvent. It is the most basic and commonly used solvent in the management of the front-end calculation process of lithium-ion batteries. It is a colorless and transparent liquid, commonly known as methyl, and its scientific name is N-methylpyrrolidone, molecular formula C5H9NO.

Generally speaking, auxiliary materials for lithium batteries mainly include solvents and binders nmp. The main function of the solvent is to dissolve the positive and negative active materials, and the main function of the binder is to bond the active materials to the collector. The amount of auxiliary materials is generally It is 2% -5%. Compared with the positive electrode, negative electrode, electrolyte and separator, the cost is relatively small, but the effect cannot be ignored.

Among them, PVDF (polyvinylidene fluoride) is the most commonly used cathode binder, and NMP is the most commonly used solvent, and they are usually used together.

NMP is soluble in water, PVDF, and positive and negative materials, so it is widely used in the preparation of lithium batteries 1 methyl 2 pyrrolidone. It can connect the required materials such as binders, positive active materials, and conductive agents with electrodes, so that the binders and other substances can fully Contact, evenly distributed.

Therefore, the quality of NMP will directly affect the quality of the slurry coating for lithium-ion batteries.

What important role does NMP play in the production of lithium-ion power batteries?

Lithium-ion batteries are now internationally recognized as ideal chemical energy sources. It has the advantages of small size, high capacitance and high voltage. It is widely used in electronic products such as mobile phones and laptop computers, and the continuous development of the electric vehicle field will provide more room for growth of lithium-ion batteries.

NMP is a polar solvent with strong selectivity and stability, which has the characteristics of high boiling point, strong solubility, good stability, biodegradability and recyclability. NMP is widely used in lithium batteries, polymer materials, electronics, cleaning agents, pharmaceuticals, pesticides, pigments and other industries, among which NMP is the largest country in the lithium battery industry.

In the preparation of lithium batteries, NMP is mainly used as a solvent for cathode materials. The structure of lithium batteries and the application of NMP in lithium batteries are briefly introduced:

A lithium battery is a device that converts chemical energy into electrical energy through the intercalation and deintercalation of lithium ions between the positive and negative electrodes. It is mainly composed of five parts: positive electrode, negative electrode, separator, electrolyte and battery case. The positive electrode is the core part of the lithium-ion battery and a key component that determines the performance of the battery, and has a direct impact on the final energy density, voltage, service life and safety of the product. It is also the most expensive part of lithium batteries, accounting for more than 40% of the cost of lithium batteries.

When the battery is used as the positive electrode in the preparation process, students need to control key technical links such as slurry preparation, coating, and drying. NMP is the lithium-ion power plant because of its strong solvency, low corrosion, and good stability. The mainstream solvent for battery positive electrode coating; at the same time, because NMP has a relatively high boiling point and is easy to condense, after drying, the exhaust gas containing NMP can be recovered by condensation, rectification and purification before use. The use analysis of NMP in each link is as follows:

In the batching stage, the binder, conductive agent, positive electrode active material and other materials required by the electrode in the polyvinylidene fluoride (PVDF) solvent are mixed, dissolved, stirred and dispersed to form a uniform slurry. The mass after dispersion Directly affect the quality and performance of lithium-ion batteries.

In the coating stage: as the main liquid carrier of the slurry, it is uniformly coated on the metal substrate with a stable thickness, and requires very good wettability and fluidity with the metal substrate. The coating process is of great significance to the capacity, service life and safety of lithium-ion batteries.

In the coating baking stage: the wet film runs at a constant speed in the oven, the solvent volatilizes regularly, NMP has a pore-forming function, and NMP volatilizes from the wet film at a constant speed, with a uniform pore size and a uniformly distributed porous microelectrode structure.

Coating machine NMP waste gas recovery treatment system and waste heat recovery device recycle NMP waste gas, and after the air is purified, it meets the "zero" emission requirement, and waste heat recycling achieves a thermal energy saving efficiency of 65-80%, with small investment and energy consumption Low power and small power, which is about 10% of the imported machine. It can reach and exceed the performance indicators of the Japanese NICHIAS hydrophobic zeolite ketone adsorption honeycomb runner without a runner at all. It is a cost-effective product.

The basic working principle is analyzed as follows: The NMP waste gas recovery data processing information system can be designed as a 50-100% fully closed cycle, and the solvent can be recovered-using different refrigeration-internal circulation utilization adsorption and concentration network technology. The recovery rate of the solvent is greater than 85-95%: due to the large exhaust air volume and low concentration of the coating machine, the internal circulation economy is used to continuously dilute the organic solvent in the exhaust gas to a certain concentration, and then develop controlled condensation recovery to reduce the product Recover logistics costs.

At the same time, the product has the following advantages:

The solvent recovery efficiency is 85-95%, and the heat energy saving efficiency is 60-80%. For example, if the air volume is 10,000, use Zn-FSQ-10000-1 combined solvent device (including heat recovery device), recover solvent 46kg/h (the design index of the pole piece is within the reasonable NMP concentration range of 10,000 air volume, saving 187 kwu002Fh of electric energy, Recycling solvent saves electricity worth 2 million yuan a year (based on recycling solvent 10,000 yuan)

The organic solvent content of the gas after solvent treatment can be lower than 9ppm or meet the "zero" emission requirement. The exhaust gas emission fully complies with the requirements of ISO14000 and the national air pollutant comprehensive emission standard GB16297-1996.

The air in the coating machine adopts closed circulation, which reduces the influence of ambient temperature, humidity and air quality on the coating quality. Waste heat recovery - use high-efficiency energy-saving technology to reduce the heat consumption of the coating machine by 60-80%: under normal circumstances, a large amount of gas is discharged during the coating process, and its temperature is generally around 110 ° C, and a large amount of fresh air is supplied to the coating machine . Adopting advanced internal circulation sensible heat exchange and heat transfer technology, a small amount of heat is exchanged between the exhaust gas supplied to the coating machine and fresh air, and most of the heat is not exchanged. After purification, it is immediately supplied to the coating machine, so that the air supplied to the coating machine is pre-heated Heat to about 85.5°C, thereby reducing the thermal energy of the coating machine by about 60-80%, and at the same time reducing the temperature of the air entering the surface for cooling to 55°C.

At present, most of the student user information of domestic enterprises in my country can use the Chuyi Measurement and Control NMP Solution Concentration Detector to carry out systematic real-time detection of the recovered NMP solution concentration data. Generally, the recovered concentration of NMP liquid is between 75-85%. After setting the concentration value, the liquid discharge pneumatic ball valve is automatically managed and controlled by PLC, and the waste liquid is discharged into the liquid storage tank, so that we can enter the next process content for research and rectification to form a high-purity NMP solution, which is directly invested in social production. The solvent used.