"Hibernation" batteries for seasonal storage that release energy when heated

　　Humans are inseparable from batteries. Scientists have developed many types of batteries for us, such as disposable dry batteries, button batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-chromium batteries, lithium-ion batteries, lithium titanate batteries, and aluminum-air batteries. and many more. Numerous types of batteries have penetrated into every aspect of our lives. Without batteries, we can't even use the remote control.

　　Continuing to explore advanced battery technology to unleash the full potential of renewable energy and work hard to solve the intermittent problem of electricity from the sun and wind is one of the directions scientists are developing for new types of batteries in the new era. Although SES Power takes customized lithium-ion batteries as our main operation direction, such as products using EVE, CATL, BYD square aluminum-shell lithium iron phosphate batteries (single 100Ah-280Ah), which can work at -40 degrees Celsius Special lithium iron phosphate batteries, of course, there are also large-scale lithium battery energy storage systems, home energy storage systems and other products. But we're still curious about future battery research. Let us introduce you to a new type of battery in the afternoon.

　　A team at the Pacific Northwest National Laboratory (PNNL) has come up with a new design in which researchers demonstrate a "hibernating" battery that can preserve its energy for months at a time. It's called a molten salt battery, and it's been around in various forms for over 50 years.

　　It is considered a suitable renewable energy storage solution for use in large grid systems due to its low cost and the use of common materials. It uses molten salt as the electrolyte, and the battery's two electrodes (cathode and anode) are filled with a solution that carries an electric charge. At high temperatures, the electrolyte, the salt, is molten and sees it flowing like a liquid, but at room temperature it becomes a solid.

　　The PNNL team has used these properties to produce what are known as hibernation batteries. The device consists of an aluminum anode and nickel cathode, which are soaked in a molten salt electrolyte doped with sulfur for additional capacity. The principle is very simple, the battery is charged by heating to 180°C (356°F), when ions flow through the liquid electrolyte to generate chemical energy. Cooling the battery to room temperature solidifies the electrolyte and freezes the ions in place, locking in the energy until the battery is reheated, allowing the energy to flow again. For this reason, scientists also refer to the device as a "freeze-thaw battery."

　　Its theoretical density is 260Wh per kilogram, which is higher than today's lead-acid and flow batteries, and the material cost for energy storage is about $23 per kilowatt-hour, which the team hopes to bring down to that per kilowatt by adding iron to the design about $6. In testing, the battery maintained 92 percent of its capacity for 12 weeks. "It's a lot like growing food in your garden in the spring, putting the excess in a container in the refrigerator, and then thawing it out for dinner in the winter," said lead author Minyuan "Miller" Li.

　　Typically, molten salt batteries use a ceramic separator between the anode and cathode to control which molecules can pass through. In 2018, an MIT team showed how to use a more durable steel mesh instead. Last year, a team at Sandia also demonstrated a cheaper version that could operate at temperatures far lower than traditional designs. The PNNL team also opted to use fiberglass instead, which they say is cheaper and more durable.

　　Scientists hope the technology could provide a seasonal energy storage, where energy is harvested at one time of the year and used at another. And, because the battery can sit idle while maintaining most of its stored energy, it will only need to be charged and discharged a few times a year.

　　"You can start envisioning something like a large battery on a 40-foot tractor trailer parked in a wind farm," said co-author Vince Sprenkle. "The battery is charged in the spring and the truck is driven to an electrical substation on the road where it can be used if needed in the summer heat."