From smartphones to electric cars and even the Tesla Powerwall, rechargeable batteries power our modern lives. But have you ever stopped to wonder what’s inside these devices that allow us to send emojis, drive around town and so much more? If so, check out the Advanced Battery Facility at Pacific Northwest National Laboratory (PNNL), one of the few experimental battery manufacturing labs that are open to the public.
The facility enables scientists to test out all kinds of new materials -- including lithium, sulfur, sodium and magnesium -- to make batteries last longer and store more juice. The tests are helping scientists from National Labs, universities and industry find more powerful and safer replacements for today’s most common rechargeable battery, the lithium-ion battery.
At the Advanced Battery Facility, scientists test-drive new materials by assembling them into cell phone-sized experimental batteries, which are called “pouch cells” because they’re enclosed in a vacuum-sealed plastic pouch. Like full-sized batteries, each pouch cell has three main parts: two electrodes and an electrolyte that separates them.
When the battery stores and later releases electricity, tiny charged particles move back and forth between each electrode, passing through the electrolyte along the way. This process provides the electricity we need to watch cat videos on our phones, zip around town in electric cars and even store renewable energy when the sun isn’t shining or the wind isn’t blowing.
So how do all these parts get assembled? Here are the seven most important steps in the process, which takes about two weeks to complete:
- Electrode slurry: Powders containing the active materials in electrodes such as lithium are mixed in a big bowl with binding materials, which act like a glue to create what scientists call a slurry, or a gooey batter.
- Electrode coating: The slurry is then spread out onto a very long (up to a few hundred feet) piece of foil, which slowly rolls through high heat (up to 300 degrees Fahrenheit) to bake the electrode into a solid.
- Electrode stamping: The baked electrode roll is cut into smaller pieces, which are placed under a super-sharp, rectangular die. With a sudden movement, the die quickly pushes down on the electrode sheet and cuts out an individual electrode battery piece.
- Electrode stacking: An automated machine uses suction to pick up and release sheets of cut-out electrode material and wrap an insulating layer in between each sheet. The result is a credit card-sized electrode stack, which is spit out of the machine with the turn of a metal arm.
- Pouch making: A special, moisture-resistant barrier material is pressed to create rectangular forms. An electrode stack is inserted into the resulting form to create a pouch cell.
- Electrolyte injection: Liquid electrolyte is injected into an open battery pouch.
- Battery sealing: The electrolyte-soaked battery pouch is heat-sealed and placed in a vacuum chamber, which removes excess air from inside the pouch.
Pouch cells are then put through the paces, continually charged and discharged within environmentally controlled chambers that mimic extreme temperatures between 20 and -140 degrees Fahrenheit.
If a test pouch cell performs well, its unique combination of different materials could enable all of us to power our lives longer and better. When a promising battery concoction is identified, National Labs work with private companies to license the technology, which the companies develop into a product that can be brought to the marketplace so all of us can buy and benefit from it.
Editor’s Note: This post is a shorter version of an article written by Pacific Northwest National Laboratory, one of the Department of Energy’s 17 National Labs. Learn more about PNNL’s energy storage work on batteries for electric vehicles and the power grid.