Chinese scientists produce a powerful winter-proof lithium battery

Lithium-ion batteries have been limited for use in low-temperature environments because it is “virtually impossible” to create a battery that can simultaneously have high energy density, have a wide operating temperature and be fast charging.

One of the reasons is because an electrolyte – a battery component that transfers ions between electrodes – enabling all of these aspects requires contradictory properties.

But such a battery could become a reality using a new electrolyte detailed in a paper published on Wednesday in the peer-reviewed journal Nature.

Researchers at Zhejiang University along with collaborators from the United States developed an electrolyte, made up of very small solvent molecules, which enables battery properties that are “unattainable” with existing electrolyte designs.

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Their findings showed the electrolyte allowed lithium-ion cells to perform with high capacity and stability in temperatures ranging from 60 degrees down to minus 80 degrees, and enabled ultra-fast charging in cold conditions.

In ultra-low temperatures, the battery “can be charged in 10 minutes to reach 80 per cent of charge capacity”, Fan told the Chinese-language news site Science Times.

Lithium-ion battery electrolytes are typically made of lithium salts dissolved in an organic solvent. Electrolytes are a limiting factor on ionic conductivity – or ion transport – in a battery.

But after four years of research, which involved screening different solvents in a wide temperature range, the team developed an electrolyte using a solvent called fluoroacetonitrile.

Using soft pack lithium-ion batteries – or flat-pouch battery cells – for testing, the team found the electrolyte enabled a previously unknown method of structural transport within batteries.

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Small solvent molecules in the electrolyte form two sheath layers around lithium ions and create channels for the ions to be transported through, called ligand-channel transport, according to Nature.

“The ligand-channel-facilitated conduction mechanism paves the way for high-energy batteries operating at extreme conditions,” the paper said.

Compared to conventional electrolytes, at minus 70 degrees this mechanism allowed for their electrolyte to have an ionic conductivity that was 10,000 times higher, Nature reported.

Beyond lithium-ion batteries, the team found that their electrolyte design principle “is also very effective for sodium-ion batteries and potassium-ion batteries”, Fan told Science Times.

There are still limits to this research, as further work may be needed to ensure the electrolyte can operate effectively within a conventional battery design, according to Nature.

While the present work serves as a model for the validity of their electrolyte design principle, “we believe this electrolyte can reach commercial use in the future”, Fan said, noting that a potential limiting factor for commercialisation was the cost of the solvent.

South China Morning Post