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Boffins step into the Li-ion's den with sodium-ion battery that's potentially as good as a lithium cousin

Electrolyte breakthrough preserves charge capacity

The world's mobile electronics, from phones to cars, largely run on batteries containing lithium, which is relatively expensive. Sodium-ion batteries are cheaper to make, but they rapidly wear out compared to their Li-ion cousins.

Now scientists in America and China have created a sodium-ion-based battery that can potentially perform at close to the levels of Li-ion, paving the way for a cheaper, commercially viable alternative to lithium.

The key challenge in creating this battery is that sodium-ion cells tend to break down faster than their lithium-ion cousins. Sodium crystals collect on the cathode, made of O3-layered metal oxide, preventing sodium ions from flowing, and thus knackering the operation of the battery.

A solution for this is what the Washington State University-based team – led by Jianming Zheng (Pacific Northwest National Laboratory), Yuehe Lin (WSU), Pengfei Yan (Beijing University of Technology), and Xiaolin Li (Pacific Northwest National Laboratory) – sought to figure out.

They eventually came up with a liquid electrolyte with a high concentration of sodium ions, which prevented the build up of inactive crystals, thus preserving 80 per cent of the cell's charge capacity after 1,000 cycles.

Not only were the new cells observed as having a higher capacity and better lifespan than older sodium-ion cell designs, but they were able to hit levels closer to those of lithium-ion.

"Our study showed that sodium-ion can be as good as some lithium-ion chemistries and thus make them more competitive and versatile," The Register was told by Junhua Song, a contributing author to the paper based out of Lawrence Berkeley Labs.

"We are hopeful that a deployable high energy and long cycle life sodium-ion battery can be realised in five years with enough funding resources."

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Song explained that while there could be other advantages to using sodium over lithium other than availability of materials and extraction costs, it is too soon to say that the sodium power cells would be, for example, safer or more environmentally friendly.

"Environmental friendliness relies on many factors because the battery is essentially a complicated system involving more than just electrode materials," he explained.

"Sodium does provide better environmental benignity due to its resource abundance and accessibility, which might do less harm to the environment during extraction, compared to the geologically constrained lithium counterpart. Similar to environmental friendliness, safety depends on many components (materials, electrolyte, cell architecture, etc), more systematic studies are on the way to tackle the safety aspect of sodium-ion batteries."

To that end, Song noted that the next steps in development of sodium-ion batteries will involve investigating the cathode and anode materials, and the actual reaction process within the electrolyte.

The team's paper, "Controlling Surface Phase Transition and Chemical Reactivity of O3-Layered Metal Oxide Cathodes for High-Performance Na-Ion Batteries", was published in the journal ACS Energy Letters.

In addition to the four lead authors, the team also included Junhua Song (Pacific Northwest National Laboratory, now at Lawrence Berkeley National Labs), Kuan Wang (Beijing University of Technology), Mark Engelhard (Pacific Northwest National Laboratory), Biwei Xiao (Pacific Northwest National Laboratory), Enyuan Hu (Brookhaven National Laboratory), Zihua Zhu (Pacific Northwest National Laboratory), Chongmin Wang (Pacific Northwest National Laboratory), Manling Sui (Beijing University of Technology), David Reed (Pacific Northwest National Laboratory), and Vincent L. Sprenkle (Pacific Northwest National Laboratory). ®


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