The cold climate battery developed. Source: Fudan University A new battery has been developed that uses organic compound electrodes that can still function at negative 70 degrees Celsius — much colder than any previous battery.

A group of researchers from Fudan University in Shanghai, China made the discovery that could help engineers develop technology that can withstand the coldest reaches of outer space or the most frigid regions on Earth.

Batteries can operate in cold climates but most have limits and generally perform about half of their optimal level when the temperature hits negative 20 degrees Celsius. By negative 40 degrees Celsius, cold climate lithium-ion batteries only operate at about 12 percent of their room temperature capacity. This severely limits what can be done to battery-operated devices in space where temperatures are negative 157 degrees Celsius or in parts of Canada or Russia where temperatures can be lower than negative 50 degrees Celsius.

When it gets cold, the conventional electrolytes (the chemical that carries ions between electrodes) that lithium-ion batteries often use become sluggish conductors and the electrochemical reactions struggle.

Researchers used ester-based electrolyte, which has a low freezing point and enables it to conduct a charge even at extremely low temperatures. Two organic compounds were used for the electrodes — a polytriphenylamine (PTPAn) cathode and 1,4,5,80 naphthalenentetracarboxylic dianhydride (NTCDA)-derived polyimide (PNTCDA) anode. These organic compounds don’t rely on intercalation, or the process of continuously integrating ions into a molecular matrix, which slows down as the temperature drops.

"Benefitting from the ethyl acetate-based electrolyte and organic polymer electrodes, the rechargeable battery can work well at the ultra-low temperature of -70 degrees Celsius," says Dr. Yong-yao Xia, a battery researcher at the Department of Chemistry of Fudan University in Shanghai, China.

Because the battery is based on organic materials, which are abundant, inexpensive and environmentally friendly, the battery could cost about one-third the price of conventional lithium-ion batteries.

Researchers warn that the battery still needs some tweaking before it is ready for commercialization and the specific energy of the battery is still low compared with current lithium-ion batteries.

"But even though it has low specific energy, it provides the most promising potential in special field applications," Xia says.

The full research can be found in the journal Joule.