Engineers develop lithium-ion batteries that perform well in extreme cold and heat

When it comes to battery developments, there is no shortage of news. From a battery design that can last up to 100 years to a water-based battery that’s produced at half the cost of lithium-ion batteries, it seems like there’s always something new and exciting happening. exciting on the pitch.

Now thEngineers at the University of California, San Diego have designed new energy-packed lithium-ion batteries that perform optimally in freezing and scorching temperatures, according to a statement by the institution released on Monday.

Extreme temperature operations

“You need high-temperature operation in areas where the ambient temperature can reach triple digits and the roads get even hotter. In electric vehicles, the batteries are usually under the floor near those hot roads,” explained Zheng Chen, professor of nanoengineering at UC San Diego Jacobs School of Engineering and lead author of the study.

“Furthermore, the batteries heat up simply because current is flowing through them during operation. If the batteries cannot tolerate this high temperature rise, their performance will degrade rapidly.

Chen’s team conducted tests with the prototype batteries and found that they retained 87.5% and 115.9% of their energy capacity at -40 and 122 F (-40 and 50 C), respectively. Even better, the researchers reported that the prototypes had high Coulomb efficiencies of 98.2% and 98.7% at these temperatures, meaning the batteries can experience more charge and discharge cycles before they stop working. .

However, the development of the new batteries was not an easy task.

“If you want a high energy density battery, you usually have to use very harsh and complicated chemistry,” Chen said. “High energy means more reactions occur, which means less stability, more degradation. Making a stable high-energy battery is a difficult task in itself – trying to do it over a wide temperature range is even harder. hard.

Engineering of a dibutyl ether electrolyte

In order to circumvent these obstacles, the team invented a dibutyl ether electrolyte and engineered the sulfur cathode to be more stable by grafting it to a polymer that prevented more sulfur from dissolving into the electrolyte.

The end result was batteries with much longer lifespans than a typical lithium-sulfur battery. “Our electrolyte helps improve both the cathode side and the anode side while providing high conductivity and interfacial stability,” Chen said.

The new batteries could now allow electric vehicles to travel further on a single charge in cold climates while reducing the need for cooling systems to prevent vehicle batteries from overheating in hot climates. But first, the team needs to increase the battery’s chemistry, optimize it to operate at even higher temperatures and further extend its life.

The study is published in the Proceedings of the National Academy of Sciences (PNAS).

Summary:

Room temperature operability and increased energy density have been recognized as two crucial goals, but they are rarely achieved together in rechargeable lithium (Li) batteries. Here we demonstrate an electrolyte system using monodentate dibutyl ether with both low melting points and high boiling points as the sole solvent. Its low solvation imparts an overall solvation structure and low solubility towards polysulfide species in a relatively low electrolyte concentration (2 mol L−1). These features have been shown to be critical in preventing dendrite growth and enabling Coulomb Li metal efficiencies of 99.0%, 98.2%, and 98.7% at 23°C, -40°C, and 50°C, respectively. . Pocket cells using thin Li metal (50 μm) and high charge sulfur polyacrylonitrile (3.3 mAh cm−2) cathodes (negative to positive capacitance ratio = 2) produce 87.5% and 115.9% of their ambient capacitance at -40°C and 50°C, respectively. This work provides solvent-based design criteria for a wide temperature range of Li-sulfur pocket cells.