The basic chemical composition of lithium batteries was discovered in the early 1900s, and the technology was commercialized in 1991, when Sony introduced the first rechargeable battery for camcorders. Since then, the application of lithium-ion batteries in mobile phones, notebook computers and electric vehicles has rapidly spread. Rechargeable lithium batteries produce 6 times the watt-hour (WH) per kilogram of nickel-cadmium (NiMH) batteries than lead-acid batteries.
The fastest-growing applications of lithium-ion batteries come from automakers in the United States and Europe, especially China, where there are more than 60 electric vehicles of different brands. As the manufacture of electric vehicles (EV) increases, so does the demand for pumps that transport chemicals, polymers, and catalysts needed to make batteries.
The key components of lithium-ion batteries include:
The current collector on the electrode has a specially designed surface coating made by pumping a slurry mixture of polyvinylidene fluoride (PVDF) and n-methylpyrrolidone (NMP). These two polymers hold the particles together in a way that promotes the electrochemical reactions required to generate voltage and current.
NMP is extremely demanding in nature, but it plays a vital role in this process. Just like a key on a lock, NMP provides the keys needed to mix and dissolve PVDF in a way optimized for this process. Once the electrode is coated, the NMP solvent will completely evaporate. The supply chain refers to NMP as indirect material because it is needed during the production process, but it is not included in the final product.
The production of lithium batteries and other hybrid batteries requires large amounts of NMP (which can be purchased from several different chemical manufacturers). In 2020, the global automotive industry will consume 360,000 tons of NMP, of which China is about 200,000 tons.
The flammability of NMP requires that pumps, pump motors, and all processing equipment must be explosion-proof. NMP is a highly toxic Class 3 flammable liquid with flammable vapor. Even the slightest contact can irritate the eyes, skin, nose, and throat. NMP affects the central nervous system and brain, causing dizziness. Long-term exposure can also cause kidney and liver damage. The U.S. Occupational Safety and Health Administration (OSHA) limits workers’ NMP exposure to 10 parts per million (ppm) during an eight-hour day.
For these reasons, sealless pumps are the first choice for handling NMP. Sealless pumps eliminate seals and related support systems, providing a reliable and leak-free solution for handling hazardous liquids.
Although safety is always the primary consideration when selecting pumps for chemical processing applications, another factor is durability and resistance to harsh and corrosive chemicals.
Years ago, when one of the world's most popular electric car manufacturers began to ramp up operations, they purchased various metal American National Standards Institute (ANSI) sealed pumps for battery cells. As NMP corroded the internal structure of the pump, they experienced pump failures one after another. The local pump distributor contacted the chemical manufacturer that provided the NMP to learn more about how they produced the chemicals and to determine which pumps they used in the production process. The NMP manufacturer uses magnetic drive pumps and has not experienced any pump failures. This information has been shared with the car manufacturer. The conversion was carried out and a magnetic drive pump was installed in the car manufacturer’s facility to handle NMP. Since then, there have been no problems, no leaks, and no pump failures.
For these types of pumping applications, durability is as important as safety. Magnetic drive pumps are specifically designed to handle corrosive or acidic applications. All wetted parts of the pump are molded ethylene tetrafluoroethylene (ETFE) components, which can safely handle various corrosive substances and solvents (up to 250 F/121 C) without corrosion. The fully encapsulated magnetic force drives the sealless pump to seal the internal magnets, isolate them from the process fluid, and maintain the integrity of the magnets throughout the life of the device. Most importantly, the Kevlar fiber-reinforced vinyl ester casing protects the inside of the pump, and a secondary stainless steel layer is also provided to improve durability.
Given the scale of operations of this electric vehicle manufacturing plant, it is important to facilitate a quick and direct replacement process to install new pumps. The installed sealless pump supports all ASME/ANSI B73.3 and ISO 2858 standards. These pumps cover a variety of sizes and standard external dimensions. This flexibility allows the installation of new pumps without extensive changes to the piping or bottom plate.
Maintenance is an important consideration for pumps that handle toxic chemical applications. Sealless pumps have no seals and no seal support system. They provide longer maintenance intervals (MTBM) intervals, thereby reducing the amount of work required to maintain the pump. Sealless pumps are easy to install, and the US Environmental Protection Agency (EPA) has fewer monitoring and related documents, which further saves time.
Routine maintenance can be performed without special tools or training. Pump designs with fewer parts are easier to repair. The sealless magnetic drive pump has only 9 wetted parts, which can be quickly repaired on site. The single-piece replaceable impeller is connected to the internal magnetic drive through a tongue and groove system. This makes it easy to replace the impeller as process conditions change, and it also simplifies warehouse parts management.
Energy efficiency is a theme that runs through all aspects of the brand of electric car manufacturers, so it is not surprising that electric car manufacturers seek energy-saving technologies to manufacture their products. Sealless magnetic drive pumps are known for their energy efficiency, but some pumps further reduce energy costs. They have carbon-filled ETFE-lined rear shells and other functions, which can minimize heat generation through zero hysteresis loss during operation.
Today, there are more than 7 million electric vehicles driving on roads around the world every day. One-third of these vehicles (more than 2.2 million) were produced last year alone, and every electric car manufacturer predicts exponential growth in the next few years. This means that the world needs more lithium-ion batteries, and all this production requires thousands (to millions) of tons of chemicals, such as NMP, which must be handled carefully by pumps specifically designed for the task.
Whether it’s safety, durability, maintenance or energy efficiency, the world’s leading electric vehicle manufacturers have sufficient evidence and good track records to show that sealless magnetic drive pumps can effectively handle the irritating chemicals needed to manufacture lithium-ion batteries .
Tom Helmreich is Sundyne's senior director of product line development. For more than 30 years, he has held various positions, including operating unit, factory design and construction, and pump design and manufacturing. You can contact him at t homas.helmreich@sundyne.com. For more information, please visit www.sundyne.com/products/ansimag-pumps.