A new battery might have what it takes to overcome the extremely cold conditions of space and other remote regions of Earth.
Researchers from China have produced a battery with organic compound electrodes that can function at -70 degrees Celsius (-94 degrees Fahrenheit)—significantly colder than the temperature at which lithium-ion batteries lose most of their ability to conduct and store energy.
Most batteries perform at only 50 percent of their optimal level when temperatures reach -20° C(-4° F). By -40° C, lithium-ion batteries only have about 12 percent of their room temperature capacity.
“It is well known that both the electrolyte [the chemical medium that carries ions between electrodes] and electrodes [the positively charged cathode and negatively charged anode] have great influence on the battery performance,” Yong-yao Xia, PhD, a battery researcher at the Department of Chemistry of Fudan University in Shanghai, said in a statement.
According to the study, extremely cold conditions cause insufficient ionic conductivity and the electrolytes eventually freeze.
“Over the past years, various approaches have been developed to overcome this issue, such as developing additives to improve the low-temperature behavior of electrolytes and externally/internally heating and insulating the cells,” the study states. “Although some electrolyte additives can efficiently improve the discharge behavior of LIBs at the low temperature from −20°C to −40°C, the corresponding recharge processes at such temperature are still very difficult.”
To overcome the conditions of the cold, the researchers used an ethyl acetate or ester-based electrolyte, which has a low freezing point that enables it to conduct a charge at extremely low temperatures without losing ionic conductivity.
The team used two organic compounds—a polytriphenylamine cathode and a 1,4,5,8-naphthalenetetracarboxylic dianhydride-derived polymide anode for the electrodes.
The organic compounds used do not rely on intercalation—the process of continuously integrating ions into their molecular matrix, which slows down as the temperature drops.
“Benefitting from the ethyl acetate-based electrolyte and organic polymers electrodes, the rechargeable battery can work well at the ultra-low temperature of -70 degrees Celsius,” Xia said.
Xia said before the battery is ready for industrial use, the specific energy still needs to increase and the assembly process needs to be optimized.
The ester-based conventional electrolytes that lithium-ion batteries usually use become sluggish conductors when it gets cold and the electrochemical reactions that occur at the interface of the electrolyte.
The new batteries could be particularly useful because compared to the transition-metal containing electrodes materials used for conventional lithium-ion batteries, organic materials are more abundant. They are also about a third of the price and environmentally friendly.