Anode-Free, Solid-State Sodium Battery Debuts

Our need for smaller, safer, more energy dense, faster charging batteries has led to some of the most interesting innovation in the world today While some researchers are working on innovations that will iron out the last remaining hold-ups sodium batteries, others are working on developing solid-state batteries, others are attempting to bring anodeless batteries to market. However, one team of scientists is working on all three of those innovations at the same time.

The researchers are from the Laboratory for Energy Storage and Conversion (LESC), based at the University of California San Diego Nanoengineering department, is a collaboration between the University of Chicago’s Pritzker School of Molecular Engineering and the University of California San Diego’s Aiiso Yufeng Li Family Department of Chemical and Nano Engineering.

“Although there have been previous sodium, solid-state, and anode-free batteries, no one has been able to successfully combine these three ideas until now,” said UC San Diego PhD candidate Grayson Deysher, first author of a new paper outlining the team’s work.

To prove their concept, the scientists have developed a new sodium battery architecture that can offer stable cycling for several hundred cycles. Sodium has been chosen instead of lithium to reduce cost and the environmental impact. Sodium is common in ocean water and soda ash mining, and an inherently more environmentally friendly battery material. Using a solid-state design will ensure it is safe and powerful.

A completely new sodium battery architecture was required to develop a sodium battery with the energy density of a lithium battery. To achieve this, the researchers decided on an anode-free design. Anode-free batteries remove the anode and store the ions on an electrochemical deposition of alkali metal directly on the current collector. The benefits of this approach include higher cell voltage, lower cell cost and increased energy density, but there have been drawbacks in the past.

“In any anode-free battery there needs to be good contact between the electrolyte and the current collector,” Deysher said. “This is typically very easy when using a liquid electrolyte, as the liquid can flow everywhere and wet every surface. A solid electrolyte cannot do this.”

Liquid electrolytes create a build-up called solid electrolyte interphase while steadily consuming the active materials, which reduces the battery’s usefulness over time. To get around this problem, the team created a current collector that surrounds the electrolyte, rather than the opposite way around. The new current collector was fabricated from aluminum powder, which is a solid that can flow like a liquid. When the battery was assembled, the powder was densified under high pressure to form a solid current collector while maintaining a liquid-like contact with the electrolyte. This technique allows low-cost and high-efficiency cycling.

Meng and Deysher have filed a patent application for their work through UC San Diego’s Office of Innovation and Commercialization. The paper, published today in Nature Energy “Design principles for enabling an anode-free sodium all-solid-state battery,” Deysher et al, Nature Energy, July 3, 2024. DOI: 10.1038/s41560-024-01569-9

http://smeng.ucsd.edu/