How are Batteries Made: The Role of Vacuum in Production
As the world slowly transitions from fossil fuel to emissions-free electrification, batteries become an indispensable storage tool for energy transfer. In particular, lithium-ion batteries are the preferred option for powering everything from mobile phones to electric vehicles.
On top of that, studies suggest that global battery demand will increase from 185 GWh in 2020 to over 2,000 GWh by 2030. This skyrocketing demand for batteries also pressures manufacturers to ramp up their production.
The growing demand for batteries is almost inevitable. So, organizations that heavily rely on batteries need to ask an important question to determine whether to have a position in battery manufacturing: How are batteries made, and what materials are necessary for production?
This article will help you learn more about the battery manufacturing process, including how it's done and how essential vacuums are in producing batteries.
The Battery Manufacturing Process
1. Electrode Manufacturing
Electrode manufacturing is the first stage in the battery manufacturing process. In this stage, the electrode materials and a conductive binder mix to form a uniform slurry. Then, depending on the battery specifications, the slurry will either be continuously or intermittently coated on both sides of the current collector. A coating machine adjusts the thickness of the slurry coating.
The coated foil will then be fed into a long drying oven to vaporize the solvent, followed by a calendaring process. This is where a rotating pair of rollers compress the coated foils to help adjust the physical properties of the electrodes, such as bonding, conductivity, density, porosity, etc.
After the calendaring process, the finished electrodes will go to slitting machines for cutting and recoiling. Then, the coils are sent to a vacuum oven to clear out any residual moisture and solvent.
2. Cell Assembly
After preparation, the electrodes will be transferred to a dry room for a sub-assembly process. This process will layer a separator between the anode and cathode, forming the battery cell's internal structure.
After assembly, ultrasonic or laser welding will connect the cell structure to cell tabs and safety devices. Next, the sub-assembly will be inserted into the cell housing. The assembly will be sealed using laser welding or tube furnace heating, leaving an opening for the electrolyte's injection.
Electrolyte injection involves using a high-precision dosing needle inside a dry room to prevent moisture from damaging the housed cell. A serial number label will mark the finished cell's case.
3. Cell Finishing
After injecting the electrolyte into the battery cell, the formation process will facilitate the cell's first charge and discharge. This is done by placing the cells in information racks for contact with spring-loaded pins. Charging and discharging the cells will proceed according to precise current and voltage curves.
Lithium ions will be embedded on the anode side of the graphite crystal structure during cell charging and discharging. The ions will form a protective layer between the electrolyte and the electrode known as the solid electrolyte interface (SEI). This protective film causes a low self-discharge of Li-ion batteries, contributing to battery life and performance.
After the formation process, the cells must undergo the aging process for quality control. The cell characteristics and performance will be monitored by measuring the open-circuit voltage (OCV). Cells will undergo this process for up to three weeks.
Following the aging process, the cells will be tested in an end-of-line test rig. They will be taken from the aging racks to the testing station and set to the shipping state of charge. Further pulse tests and other production-related battery research, such as internal resistance measurements (DC), optical inspections, and leakage tests, may also be carried out.
Once the cells have successfully passed the tests, they will be assembled into battery packs.
How is Vacuum Technology Used in Battery Manufacturing?
Vacuum ovens and chambers play a vital role in the different stages of battery manufacturing. Here are their primary uses in battery production.
Mixing the slurry with binding agents, solvents, and lithium metal oxides takes a lot of time. In this method, air bubbles commonly build up and become an obstacle to making quality lithium-ion batteries.
A vacuum pump is effective in sucking the bubbles out of mixing chambers. With the help of a vacuum pump, you can help these chambers produce a uniform and homogeneous paste. This uniformity is crucial because it helps maintain the batteries' quality, performance, and longevity.
A vacuum is also necessary for drying, as it helps remove moisture and solvents like N-methyl pyrrolidone. Depending on the machine's in-line drying system, a vacuum drying oven is generally compatible for continuous and batch processing.
Vacuum pumps can perform without a problem, even if you subject them to harsh conditions like temperature and terrain. The conditions rarely matter when using a vacuum pump because it can consistently maintain its vacuum level and deliver premium quality electrodes. As such, you can ensure the production of the best lithium-ion batteries every time.
3. Filling and Degassing
In filling and degassing, a vacuum evacuates the cells by gradually taking them out one at a time and filling the chamber with electrolytes. A vacuum also allows lithium ions to move independently. This free movement will enable the lithium-ions to charge and discharge quickly.
Degassing is laborious, so you must ensure that the vacuum pump is robust enough to produce the electrolyte purity required to create long-lasting lithium-ion batteries.
In addition to filling and degassing, you will need a vacuum to seal the lithium-ion batteries. With a vacuum, removing moisture, air, and any contaminants in the battery is easier before packing and sealing.
Vacuum pumps are responsible for the tightly wrapped plastic around lithium-ion batteries. Once batteries reach their desired figure, they go through a vacuum chamber that removes all impurities within seconds. Battery technologies constantly evolve, but in the meantime, the batteries must have a plastic coating that prevents the ingredients from touching the user's skin.
Batteries and Vacuum: A Powerful Duo
Batteries accept, store, and release electricity on demand, making them crucial in transitioning to a renewable-energy-fueled world.
Here, knowing the battery manufacturing process can be valuable for your team in understanding how to align your strategies better. It's equally vital to know the tools that make battery manufacturing possible, including vacuum chambers and ovens.
Across International carries a wide range of lab equipment and tools essential in battery manufacturing. For more information, check out Across International's vacuum ovens and tube furnaces with vacuum flanges.