Sodium batteries match standard lithium-ion batteries for the first time

New sodium-based solid-state battery could mean competition for the common lithium-ion battery

In today's world, lithium-ion batteries dominate the battery market and over 70% of rechargeable batteries are lithium-ion. However, their key ingredient, lithium, is rare and expensive, and mining it often means serious environmental consequences. To address this problem, a group of scientists led by Y. Shirley Meng at the University of Chicago Pritzker School of Molecular Engineering have developed a new sodium battery that matches its competitor.

Batteries work by maintaining a electric potential difference, or voltage, between its two positive and negative terminals (electrodes). This keeps the electrons (or current) flowing which is the basis of all electrically-powered devices today, from electric cars to phones. Lithium-ion batteries work by exchanging positively-charged lithium ions between a positive and negative terminal, causing one side to be negatively charged, forcing electrons through the conductor connecting the two terminals externally. A separator prevents electrons from directly flowing to the other terminal through the electrolyte (solvent between the terminals that allows positive ions to transfer). The direction the lithium ions flow and hence the electrons depends on whether you are powering a device with the battery or charging it. Though sodium is cheaper, more abundant, and less environmentally harmful to extract than lithium, it has not developed much in the battery industry because it struggles to keep up with lithium-ion batteries' performance at typical temperatures.

To create the battery, the scientists used sodium hydridoborate (NaBH4). They heated this metastable form until it began to crystallize (to develop a repeating, organized pattern in its 3D lattice structure). Metastable describes a state of a system that is not in its lowest-energy configuration, but which remains stable when subject to minor disturbances (think of a ball momentarily stopping in a divot while rolling down a hill). Then, to preserve this structure, they rapidly cooled the sodium. Because this entire process is well-known in the manufacturing sector, this could allow these batteries to be quickly manufactured, an additional plus. Finally, the scientists combined this metastable phase with a special O3-type cathode (positive terminal) to create a thick, more bulky cathode that increases the theoretical energy density of the battery.

Though this was a significant step forward for the sodium battery, there still remains research and testing to do before it can begin to be manufactured and implemented. As one of the scientists said, "It's still a long journey, but what we have done with this research will help open up this opportunity."

Watch: