By Irina Slav
Sodium, an element far more abundant than lithium, is expanding its claim to fame in the battery field. A new study from a Japanese university has suggested that a sodium compound could relatively easily replace lithium in batteries.
The study, by researchers from the Nagoya Institute of Technology, found a way around the main obstacle for swapping lithium with sodium: the larger size of the ions in sodium and its different chemistry, Phys.org reports. They did this by finding a sodium compound that displayed a crystal structure that was compatible with battery use, along with a favorable electric structure and electrochemical properties. The compound yielded shorter charging times than lithium-ion batteries and a potentially longer battery life.
As great as this may sound, the researchers have run into a challenge: the compound, Na2V3O7, began deteriorating in the final stages of the charging process and that represented a cap on its theoretical energy storage capacity by as much as 50 percent. The research team, according to lead author Naoto Tanibata, will now focus on overcoming this obstacle.
Sodium batteries are not all in the laboratory stage of development, however. The allure of sodium—cheap, abundant, and has the right chemistry for batteries—has been growing and there are already functioning projects.
Last year, scientists from the Australian University of Wollongong announced they had solved a problem with sodium batteries that made them too expensive to produce, namely a lot of the other materials used in such an installation besides the sodium itself. Some of these materials were sensitive to air, which made it challenging to produce the batteries cheaply enough to make them commercially viable and guarantee a certain level of performance.
After the Wollongong researchers solved this problem by developing a material that was not sensitive to air, they launched a pilot sodium-ion battery project at a sewage pumping station in Sydney. The sodium batteries are yet to be delivered to the project, which also features solar panels for energy generation, so its performance has yet to be tested in real-life conditions.
However, according to researchers involved in sodium batteries, these would be best suited to stationary energy storage installations: sodium batteries tend to have a substantially lower energy density, which means they have yet to evolve enough to compete with lithium-ion batteries on size. In energy storage, however, they could make a real splash since size is not as important as it is for, say, car batteries or consumer electronics.
Even so, sodium batteries are turning into a hot area of research seeking to remove the main obstacles to larger sodium battery adoption. A team from the University of Birmingham last year joined the Australian and Japanese scientists in solving sodium battery problems, coming up with an alternative to the graphite anode that is used in lithium batteries, but is problematic for sodium batteries since the larger sodium ions cannot travel between graphite’s carbon layers. Replacing graphite with phosphorus, based on calculations by supercomputers, the University of Birmingham researchers succeeded in achieving charge carrier capacity seven times that of batteries featuring a graphite anode.
The implications of these accomplishments could be significant as the world gradually realizes it would need a lot of energy storage capacity built in the coming years as we shift towards more renewable-derived and less fossil fuel-derived power. Sodium batteries seem to have a legitimate claim to fame alongside lithium ion technology, and they could greatly boost energy storage capacity-building, which would in turn benefit greater renewable power adoption as this would solve the intermittency problem.