- A new "saltier" sodium-ion battery design showed marked improvement in capacity over time.
- Researchers are racing to make competitive sodium-ion batteries using a variety of new materials.
- Using more sodium in the liquid electrolyte helps to prevent capacity-destroying crystals.
Researchers from Washington State University (WSU) and the Department of Energy’s Pacific Northwest National Laboratory (PNNL) have released new data on a sodium-ion battery breakthrough. Their design avoids some classic sodium-ion battery problems, making for the best results ever achieved with this technology—almost on par with lithium-ion batteries.
Sodium-ion batteries have long been held back by one major obstacle: salt crystals accumulate within the structures and eventually ruin them. To solve that, these researchers added even more salt. By choosing a liquid electrolyte with more room for sodium ions, the scientists helped ensure that sodium kept circulating and didn’t “latch on” to start to form crystals.
As a result, WSU said in a statement, “It is able to deliver a capacity similar to some lithium-ion batteries and to recharge successfully, keeping more than 80 percent of its charge after 1,000 cycles.” That’s comparable to lithium-ion batteries and on par with guidelines for Mac laptops, for example. All batteries experience capacity fade, which is the umbrella term for the way rechargeable batteries lose total energy storage over time.
In their new paper in American Chemical Society’s journal ACS Energy Letters, the scientists write, “Here, we develop a high-performance cathode for SIBs toward practical applications by suppressing the formation of a rock salt layer at the cathode surface with an advanced electrolyte.”
Indeed, they hope future research will take the same overall blueprint for a saltier electrolyte and prepared cathode and find even better combinations of ingredients for further improvements.
Research on sodium-ion batteries in general is motivated by both the high cost and rarity of ingredients in lithium-ion batteries. As major players like Elon Musk start to invest in battery storage infrastructure, our need for these batteries will only increase, and cheap and plentiful sodium makes for a huge savings. But that only makes sense if the batteries are at least almost as good.
"The key challenge is for the battery to have both high energy density and a good cycle life," lead author Junhua Song, of WSU, said in the statement. "If we can find viable alternatives to both lithium and cobalt, the sodium-ion battery could truly be competitive with lithium-ion batteries.”
For now, the scientists would like to further study what’s happening inside their more successful battery. By analyzing each part and the whole interaction in more detail, they can speculate on different materials or changes that will improve outcomes even more. The sodium-doped electrolyte could make existing experimental battery designs better. And it all means that a viable sodium-ion battery is within our reach.
"This work paves the way toward practical sodium-ion batteries, and the fundamental insights we gained about the cathode-electrolyte interaction shed light on how we might develop future cobalt-free or low cobalt cathode materials in sodium-ion batteries as well as in other types of battery chemistries," Song said.