Sodium battery: A possible game-changer  

Power storage is as much of a headache for scientists as providing clean sources of power is. And while most of the world chases after rare metal for batteries, Iowa looks to sodium for storage solution. 

The Iowa Economic Development Authority has been funding and encouraging research into various forms of battery storage for months. In July, it gave Steve Martin, a materials science and engineering professor at Iowa State University, a $480,000 grant to continue work aimed at making a battery based on solid sodium. They aim to use it for storing wind energy.

Should Martin succeed in devising a feasible way to store large amounts of power in a solid-state sodium battery, it could be "a game-changer," said Brian Selinger, who directs the Economic Development Authority's energy office. 

Most batteries use lithium, which is much more expensive and rare than sodium, the seventh most common mineral. Batteries use liquid lithium or sulfuric acid to shuttle ions back and forth between the battery's positive and negative poles. A few use a liquid form of sodium. Although lithium-ion is the prevalent technology in cell phones and electric vehicles, it has important limitations, according to Martin.

In its liquid form, lithium is volatile and vulnerable to exploding when heated. Also, it is a fairly expensive soft metal whose cost will "skyrocket" as the demand for battery storage escalates, Steve Martin predicts.

That would make it a pricey technology. However, he and a few others from around the world are working on the technical issues, to make sure sodium batteries are available for commercial use and and can provide storage on a massive scale.

"This is a very large problem," Martin said. "If you're going to build gigawatts of batteries for storing wind energy, it takes tons and tons and tons of sodium."

In Iowa, about 10,000 megawatts of wind power are now installed or under development. The National Renewable Energy Laboratory puts the state's potential at roughly another 100,000 MW. But much of the potential will remain just that until there's a way to move it or store it, according to Mike Carberry, vice president of the Iowa Wind Energy Association. And moving it has proven difficult. Scientists are hoping battery storage could replace some of the need for transmission. 

However, achieving a solid sodium battery will not be easy. Martin compares pushing and pulling ions through a solid hunk of sodium to dissolving sugar with ice cubes. Most battery technologies move ions back and forth through a liquid electrolyte, whether it's lithium or sulfuric acid. "In the solid state, things slow down," he said. 

Even though Martin is working with solid sodium, he is trying "to make it, at the atomic level, act like a liquid." He's been working on this problem for decades. The federal Department of Energy found the work important enough to give him $3 million in 2015.

"We're five, 10, 15 years away from a marketable, safe, rugged, reliable sodium battery," Martin hopes.