The role of NMP in lithium ion battery production

Lithium ion battery is today's ideal chemical energy, with small size, large capacity, high voltage advantages, is widely used in mobile phones, laptops and other electronic products, the expanding field of electric vehicles in the future to lithium ion battery to bring greater space for development. Our country and the major developed countries have many policies to support new-energy vehicles. The development planning of seven strategic emerging industries, such as new energy vehicles, will further promote our electric vehicles from the policy level. In 2009, the output of lithium-ion batteries was about 3.05 billion, with a total battery capacity of about 15,000Wmh. Data shows that the capacity of lithium-ion batteries for electric vehicles reached 14,000wMH in 2013, equivalent to 93% of the capacity of small lithium batteries in 2009: In 2018, the capacity of lithium batteries for electric vehicles reached 45000WMh, nearly three times the capacity of small lithium batteries in 2009.

NMP belongs to nitrogen heterocyclic compounds, which has a series of excellent physical and chemical properties. It is a non-toxic, high boiling point, strong polarity, low viscosity, low corrosion, high solubility, low volatility, good stability and easy recovery of selective solvents. Widely used in petrochemical, pesticide, medicine, electronic materials and other fields.

NMP is a very important auxiliary material for the production of lithium ion battery electrodes. It is commonly used as a solvent in the topping process of lithium ion batteries. It is commonly known as methyl, and its scientific name is N-methylpyrrolidone, with the molecular formula C5H9NO

In the battering stage: as a PVDF solvent, participate in the slurry dispersion, forming a uniform medium, in a certain range of viscosity for a long time to maintain stable slurry

In the coating stage: as the main liquid carrier of slurry, uniform coating on the metal substrate with stable thickness, and the metal substrate has very good wettability and fluidity

In the coating and baking stage: wet film in the oven at uniform speed, the solvent volatilized regularly, NMP assumes the poremaking function, NMP volatilized from the wet film at a stable speed, forming a porous microelectrode structure with uniform pore size and distribution.

Coatingmachine NMP waste gas recovery treatment system and waste heat return device through the recovery of NMP waste gas, air after purification treatment, to achieve "zero" emission requirements, waste heat recycling according to customer requirements to achieve energy saving efficiency 65-80%, small investment, low energy consumption, small power, is about 10% of the import machine, * Without the runner can also reach and exceed the Japanese NICHIAS hydrophobic zeolite ketone adsorption honeycomb wheel performance indicators, is a cost-effective product.

The working principle is as follows:

First, NMP waste gas recovery system can be designed to be 50-100% fully closed cycle, solvent recovery -- using freeze-internal cycle adsorption concentration technology to recover organic solvents in waste gas, organic solvent recovery is greater than 85-95% : Because of the large exhaust air volume and low concentration of coater, the internal circulation is used to continuously release the organic solvent in the waste gas to a certain concentration, and then condensate recovery is carried out to reduce the recovery cost. At the same time, the product has the following advantages:

1. Solvent recovery efficiency is 85-95%, heat saving efficiency is 60-80%. For example: For 10,000 air volume, ZN-FSQ-10000-1 combined solvent unit (including heat recovery unit) was adopted to recover 46kg/h solvent (each index of the electrode plate design was within the NMP concentration range of 10,000 air volume, saving 187kw/h electric energy. The value of solvent recovery plus energy saving is RMB 2 million yuan a year (calculated as 10,000 yuan of solvent recovery/ton and 0.7 yuan of electricity cost/ton).

2. After solvent recovery treatment, the content of organic solvent in the gas can be below 39ppm, or to the "zero" emission requirements. The emission of NMP refers to the discharge rate standard requirements calculated in accordance with the implementation of the "Large allowable concentration of harmful organic matter in the air of the Working environment of the former Soviet Union" and in accordance with the "Technical Method for the Establishment of Local Emission Standards of Atmospheric Pollutants" (GB/T3840-91). *ISO14000 requirements and in line with the national "air pollutant comprehensive emission standards" GB16297-1996.

3. The air in the coater adopts closed circulation, and the influence of ambient temperature, humidity and air quality on the coater quality is reduced.

Two, waste heat recovery - the use of energy saving technology to reduce the heat consumption of the coater 60-80% : under normal circumstances, there is a lot of gas discharge in the coater process, the temperature is generally about 110, and a lot of fresh air is added to the coater. Our company adopts advanced internal circulation sensible heat exchange heat transfer technology will exhaust and add to the coater fresh air for a small part of the heat exchange, most do not exchange after purification treatment immediately added to the coater, so that the air added to the coater preheating to about 85.5, so that the coater heating energy down about 60-80%, At the same time, the air temperature entering the surface cold drops to 55.

At present, the vast majority of domestic users are using Chuyi NMP solution concentration detector to detect the concentration of NMP solution in real time. Generally, the concentration of NMP liquid recovery is between 75-85%. After reaching the set concentration value, the waste liquid is discharged into the liquid storage tank by PLC automatic control pneumatic ball valve. In order to facilitate the next process of rectification to form a high purity NMP solution, directly used as a solvent for production. Domestic comparison users are: Lishen battery, star source material, Guoxuan high-tech, etc.