You hear a lot about the shortcomings of lithium-ion batteries, mostly related to the slow rate of capacity improvements. However, they’re also pretty expensive because of the required lithium for cathodes. Sodium-ion batteries have shown some promise as a vastly cheaper alternative, but the performance hasn’t been comparable. With the aid of lasers and graphene, researchers may have developed a new type of sodium-ion battery that works better and could reduce the cost of battery technology by an order of magnitude.
The research comes from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. Much of the country’s water comes from desalination, so there’s a lot of excess sodium left over. Worldwide, sodium is about 30 times cheaper than lithium, so it would be nice if we could use that as a battery cathode. The issue is that standard graphite anodes don’t hold onto sodium ions as well as they do lithium.
The KAUST team looked at a way to create a material called hard carbon to boost sodium-ion effectiveness. Producing hard carbon usually requires a complex multi-step process that involves heating samples to more than 1,800 degrees Fahrenheit (1,000 Celsius). That effectively eliminates the cost advantage of using sodium in batteries. The KAUST team managed to create something like hard carbon with relative ease using graphene and lasers.
It all starts with a piece of copper foil. The team applied a polymer layer composed of urea polymides. Researchers blasted this material with a high-intensity laser to create graphene by a process called carbonization. Regular graphene isn’t enough, though. While the laser fired, nitrogen was added to the reaction chamber. Nitrogen atoms end up integrated into the material, replacing some of the carbon atoms. In the end, the material is about 13 percent nitrogen with the remainder carbon.
Making anodes out of this “3D graphene” material offers several advantages. For one, it’s highly conductive. The larger atomic spacing makes it better for capturing sodium ions in a sodium-ion battery, too. Finally, the copper base can be used as a current collector in the battery, saving additional fabrication steps.
The researchers tested a sodium-ion battery with 3D graphene anodes, finding the system outperformed existing sodium-ion systems. It’s still not as potent as lithium-ion, but these lower cost cells could become popular for applications where high-performance lithium-ion tech isn’t necessary. Your phone will run on lithium batteries for a bit longer.
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