Researchers in China use a one-atom swap to make cheap aluminum fight sodium-sulfur battery decay
Rapid deterioration remains a persistent obstacle for sodium-sulfur batteries, but a team in China has targeted that weakness with a redesigned aluminum catalyst.
Large-scale storage of renewable electricity could benefit from the resulting improvement in battery performance. The change involved replacing just one atom in the catalyst's structure.
Here's what to know
Professors Wang Hui and Zheng Fangcai led the work at the Chinese Academy of Sciences' High Magnetic Field Laboratory in Hefei, according to Interesting Engineering . With their single-atom aluminum catalyst, batteries showed greater stability through repeated charging and discharging, while the reactions inside them proceeded faster.
In laboratory testing, the aluminum-based cathode delivered a storage capacity of 1,196 milliamp-hours per gram after 100 cycles. Across 2,500 consecutive charging and discharging cycles, the loss in capacity was only 0.017% each cycle.
The performance advantage over costlier transition-metal catalysts came from a redesigned form of aluminum, an abundant, inexpensive metal used in ordinary soda cans.
More background
For grid operators, sodium-sulfur batteries could provide a lower-cost alternative to lithium for storing renewable electricity. Sodium's abundance and low price have long made it a candidate for large-scale energy storage.
A sodium-sulfur battery's life can be shortened by the loss of active material from its cathode. That loss can occur when intermediate compounds called sodium polysulfides form inside the battery, dissolve, and migrate away.
Aluminum's low price and lack of toxicity are advantages, but conventional catalysts made from it have not been chemically active enough to hold polysulfides in place. Efforts to control these reactions have also involved metals such as platinum, cobalt, and nickel.
What's being done?
For the Hefei team, improving aluminum's catalytic activity meant redesigning its immediate atomic surroundings.
The resulting Al–O3N structure placed nitrogen alongside three oxygen atoms around each aluminum atom. To create it, the researchers replaced one oxygen atom with nitrogen in the typical single-atom arrangement, which surrounds each aluminum atom with four oxygen atoms.
Inside the battery, sulfur-containing substances interacted more strongly with the aluminum sites. Behind that improvement was the uneven arrangement of neighboring atoms, which redistributed electrons around aluminum and produced a strong localized electric charge.
Combining aluminum's low cost with longer-lasting performance could make renewable-power storage more economical for utilities and companies.
"The findings highlight the importance of the local atomic environment in determining the catalytic activity of single-atom catalysts and offer new possibilities for designing efficient catalysts based on main-group metals," the researchers said.
Where can I learn more?
The push for cheaper, longer-lasting energy storage goes beyond sodium-sulfur batteries to sodium-ion technology and redesigned electrodes.
• A new index shows when cheaper sodium-ion batteries can replace lithium-ion technology.
• Sodium-ion batteries are reaching EVs and home storage without relying on lithium or cobalt.
• In Colorado, a renter exploring salt batteries for solar backup received recommendations favoring safer LiFePO4.
• A Germany-led team developed thicker battery electrodes that could increase energy density by 15%.
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