As the world moves towards clean energy production, the need for clean batteries for transportation will undoubtedly increase. So far, the most efficient solution we have are lithium-ion batteries, but they have many disadvantages.
Sodium ion batteries have tremendous potential as an alternative, but their technology is giving scientists a lot of headaches. Now researchers at the University of Geneva believe they've solved them.
Lithium-ion battery problems were discussed many times. They are not very safe because their liquid electrolyte can ignite in various accidents. In addition, lithium itself is found in a fairly small part of the Earth. Scientists say this will pose the same geopolitical problems in the future as oil does now. Finally, as technology advances, we must always look for better solutions.
Sodium, a neighbor of lithium on the periodic table of elements, is a good candidate to replace this rare and precious metal. We have a lot of sodium everywhere. At least in theory, sodium ion batteries could be safer and more powerful if a solid electrolyte was used. However, there is one problem - sodium is heavier than lithium, which makes it difficult for it to pass through the electrolyte.
Back in 2013-2014, Japanese and American scientists discovered that hydroborates can be excellent electrolytes for sodium batteries, but only after reaching a temperature of 120 C. These temperatures are simply unacceptably high for everyday batteries, but researchers in Geneva who have been working with hydroborates for decades have seen a solution to this problem.
Geneva crystallographers (crystal chemists) began to improve the hydroborate electrolyte and achieved excellent results.
“We were able to use the hydroborate electrolyte in the temperature range from room temperature to 250 C without any safety concerns,” said Radovan Cerny, project manager.
The researchers also welcomed the fact that the sodium ion batteries they are developing will be even more powerful.
How did the researchers do this? The answer to this riddle was found in the chaos. Crystallographers have confused the usually neat composition of hydroborates, creating spheres of boron and negatively charged hydrogen. The gaps between them were large enough for positively charged sodium ions to move between one electrode and the other. The mixed formulation, although ineffective, allows sodium ions to move freely.
The researchers say they are developing an ideal battery based on a solid electrolyte with an imperfect structure. There is still a lot of work to be done before such batteries are manufactured and tested. But the first results are really good.
Sodium ion batteries can replace lithium-ion cells, making them safer, cheaper and more environmentally friendly.