New Electrode for Grid-Scale Batteries
On the small, personal scale, batteries have enabled many technologies, and on the large scale, they could do the same. One of the outstanding issues of solar and wind panel is their variability throughout the day, which massive batteries could address, but such batteries are expensive, dangerous, and do not always survive long. Researchers at the Pacific Northwest National Laboratory however, have found a way to ease these problems for one class of battery.
Sodium-beta batteries are massive batteries the size of cargo containers that use pure sodium as the negative electrode, with a solid, ceramic membrane made of beta alumina separating the electrodes. Ideally the sodium will completely coat the beta alumina, but molten sodium resists the ceramic if temperatures are below 400 ºC, so the batteries operate at 350 ºC. While this is necessary for operation, it also shortens the lifespan of the batteries, and poses a fire risk. The PNNL researchers found a solution by changing the electrode from pure sodium to a sodium-cesium alloy that will wet the ceramic at lower temperatures.
The new battery has an operating temperature of just 150 ºC and keeps the 420 milliampere-hours per gram capacity of traditional sodium-beta batteries. That capacity last longer in the new battery as well, as one hundred cycles only brought it down to 97%, while pure-sodium batteries are at 70% after sixty cycles. Also the reduction in temperature would allow cheaper materials to be used for the battery, as steel could be replaced by polymers.