By Irina Slav
While everyone else was worrying about cheap oil and the future of electric cars, sodium batteries just got closer to becoming mainstream. This challenger to lithium ion technology has been around for a while but it has also been plagued by some inherent problems. Now, another one of these has been solved by researchers from the Pacific Northwest National Laboratory and the Washington State University.
The problem with sodium batteries are their limited capacity.
Battery capacity is a top priority for any battery developer, especially in the EV space where a car’s attractiveness to buyers relies heavily on its range, which, in turn, depends on the car’s battery capacity. But like everything, there is a tradeoff. The greater the capacity, the higher the price of the battery and, therefore, the car. This is what makes the search for an alternative to costly lithium ion batteries so urgent.
Sodium batteries are inarguably cheaper than lithium ion. Sodium is found in abundance anywhere there is salt water. Meanwhile, the supply of lithium is limited to a few places in the world.
Then there is the cobalt issue, which is an issue both fundamental—most of the world’s supply is concentrated in one country, the Democratic Republic of the Congo—and ethical, because the DRC is notorious for child labor in its cobalt mines. Sodium batteries dispense with the lithium problem by not using the element altogether. They still use cobalt, however.
Now, according to the team led by WSU professor Yuehe Lin and senior PNNL research scientist Xiaolin Li, sodium batteries could have a capacity comparable to that of lithium ion batteries. What’s more, the durability of their battery was also much better than previous attempts, with 80 percent of capacity remaining after 1,000 charge-recharge cycles.
What the scientists did was make a better cathode to prevent the buildup of sodium crystals that compromised the performance of previous sodium batteries by interfering with the recharging process and eventually leading to the battery’s death. But they also cooked up a saltier liquid electrolyte for the battery: it had more sodium ions than previous batteries to improve interaction with the cathode.
And it worked.
“Our research revealed the essential correlation between cathode structure evolution and surface interaction with the electrolyte,” Professor Lin says in comments on the news as quoted by Science Daily. “These are the best results ever reported for a sodium-ion battery with a layered cathode, showing that this is a viable technology that can be comparable to lithium-ion batteries.”
Sodium batteries are certainly a viable technology: over the last two years several studies have reported solving potentially major problems with such batteries, including costly materials, and the larger size of the ions in sodium and its different chemistry, which made it challenging to swap it for lithium without affecting the performance of the battery significantly.
Now, the WSU and PNNL scientists have set their sights on cobalt. “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,” says one of the lead authors, Junhua Song. “If we can find viable alternatives to both lithium and cobalt, the sodium-ion battery could truly be competitive with lithium-ion batteries. And, that would be a game changer.”
EV sales next year could jump by 36 percent, according to Cairn Energy Research Advisors. This means more than 3 million electric vehicles—a record-high. Now, these more than 3 million EVs will all have lithium ion batteries. But a few years from now, a lot of EVs may be equipped with other, cheaper, but equally reliable batteries made from one of the most abundant elements on the planet: sodium.