402030 polymer battery.Ultra-cheap earth elements drive new battery technology to the industry

　　Most of today's batteries are made of rare lithium cells mined in the mountains of South America. If the world runs out of this source, battery production could grind to a halt. Sodium is a very cheap and land-abundant alternative to using lithium-ion batteries, which also turns purple and burns if exposed to water - even just water in the air. Global efforts to make sodium-ion batteries as functional as lithium-ion batteries have long controlled sodium's tendency to explode, but have yet to solve how to prevent sodium ions from "getting lost" during the first few times a battery is charged and discharged. Now, researchers at Purdue University have created a sodium powder version that solves this problem and charges correctly. "Adding the manufactured sodium powder during electrode processing requires only minor modifications to the battery production process," said Vilas Pol, associate professor of chemical engineering at Purdue. "This is a potential way to bring sodium-ion battery technology to industry." The study was published online in June 2018 and published in the journal Power Source on August 31, 2018. The effort aligns with Purdue's Leap Celebrations, recognizing the university's global advancements in health, space, artificial intelligence and sustainability as part of Purdue's 150th anniversary. These are the four themes of the Festival of Ideas, a yearlong celebration designed to showcase Purdue as a center of knowledge solving real-world problems. Although they are physically heavier than lithium-ion batteries, researchers have been studying sodium-ion batteries because they can store energy at a lower cost for large solar and wind energy facilities. The problem is that the sodium ions stick to the hard carbon end of the battery, called the anode, during the initial charge cycle, instead of traveling to the cathode end. The ions accumulate into a structure called a "solid electrolyte interface." "Typically, the solid electrolyte interface is good because it protects the carbon particles from the battery's acidic electrolyte, where electricity is generated," Pol said. "But too much interface consumes the sodium ions we need to charge the battery." The Purdue researchers suggest using sodium as a powder to provide the solid electrolyte interface with the required amount of sodium to protect the carbon, but not at the expense of Sodium ions accumulate. They did this by making sodium powder in an argon-filled glove box, exposing the sodium to moisture, causing it to burn. To make the powder, they used ultrasound - the same tool used to monitor fetal development - to melt lumps of sodium into a milky purple liquid. The liquid is then cooled into a powder and suspended in a hexane solution to evenly disperse the powder particles. Simply placing a few drops of sodium suspension on the anode or cathode electrode during the manufacturing process makes the sodium-ion battery charge and discharge more stably and have a higher capacity - the minimum requirement for a functional battery.

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