By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium-ion rechargeable batteries, which could be a cheaper alternative for large-scale uses, such as storing energy on the electrical grid.

To connect solar- and wind-energy sources to the electrical grid, batteries that can store large amounts of energy are necessary at the source. Lithium-ion rechargeable batteries—common in consumer electronics and electric vehicles—perform well but are too expensive for widespread use on the grid because it would require many large batteries. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300°C, which is three times water’s boiling point, making them more dangerous and less energy-efficient than batteries that run at ambient temperatures.

The idea was to use the best of both processes, but the conflict the researchers had to overcome was that sodium ions are 70 percent bigger than lithium ions, preventing them from moving as efficiently.

A team of scientists at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) and visiting researchers from China’s Wuhan University solved the problem by using nanomaterials to make electrodes that can work with sodium.

“The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer,” said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The result is a high-performance battery that may take the heat off an already taxed electrical power grid.

Grid batteries need to charge quickly, so they can collect as much newly made energy coming from renewable sources as possible. They also need to discharge quickly when demand shoots up as consumers turn on their air conditioners and television sets and plug in their electric vehicles at home. These new sodium-ion batteries may be just what the electrical grid is looking for.