A team at the Pacific Northwest National Laboratory (PNNL) has developed a dormant battery that can store its energy for months. When cooled to room temperature, the charged electrolyte in it solidifies, conserving energy in itself until the battery is reheated.

The device consists of an aluminum anode, a nickel cathode, and a molten salt electrolyte alloyed with sulfur to further increase the capacity. The battery is charged by heating up to 180°C, where ions pass through a liquid electrolyte to generate power. When cooled, the ions in the electrolyte “fall into a deep sleep.”

The first prototype is no larger than a hockey puck and has a density of 260 Wh per kilogram, which is higher than current lead-acid and flow batteries. In testing, the battery retained 92% of its capacity for 12 weeks. Now the cost of 1 kWh in such a battery is $23, and due to the use of iron, it can be reduced to $6.

“Imagine a big battery on a 40-foot tractor-trailer parked at a wind farm. The battery is charged in the spring and then the truck drives down the road to the substation where it can be used in the heat of the summer,” said Vince Sprenkle, one of the developers.

Scientists have already patented the technology and published their study in the journal Cell Reports Physical Science.