Higher energy density, lower environmental impact, longer lifetime, orders of magnitude shorter charging time, less flammable, cheaper production, to name just a few of the futuristic goals of dozens of battery technology research labs. But the basic research is still going on.
Lithium-ion batteries are made of materials such as cobalt and lithium, which are rare and expensive. With the growing demand for electricity storage, these materials are becoming increasingly difficult to obtain and are likely to become more expensive. In addition, lithium-based battery technology is struggling to meet the vastly increasing energy storage needs of the power grid. In contrast, sodium-ion batteries using sodium, which can be extracted from the Earth’s oceans or from the crust in abundant and sustainable quantities, could provide a viable alternative for large-scale energy storage. Unfortunately, they cannot yet store as much energy as lithium batteries.
The critical challenge is for the battery to have high energy density and excellent cycle times. Now researchers at Washington State University (WSU) and the Pacific Northwest National Laboratory (PNNL) have developed a new sodium-ion battery that can store as much energy and operate as efficiently as some commercially available lithium-ion batteries. The new battery technology can be successfully recharged while retaining more than 80 percent of its charge after 1000 cycles.
The scientists created a layered metal oxide cathode and liquid electrolyte containing extra sodium ions, creating a saltier medium that interacted better with the cathode. The cathode design and electrolyte system allowed for a continuous flow of sodium ions, preventing the accumulation of inert surface crystals, allowing for unlimited current production.
Yuehe Lin, Professor at WSU School of Mechanical and Materials Engineering, said, “Our research has revealed the fundamental relationship between the evolution of the cathode structure and the surface interaction between the electrolyte. This is the best result ever reported in experiments with layered cathode sodium-ion batteries, showing that it is a viable technology comparable to lithium-ion batteries.”
Junhua Song, the lead author of the study from Lawrence Berkeley National Laboratory, added: “This work paves the way towards practical sodium-ion batteries, and our understanding of the fundamental process of cathode-electrolyte interactions sheds light on how we can develop cobalt-free or low-cobalt cathode materials for sodium-ion batteries, as well as other types of battery chemistry in the future.
If viable alternatives to both lithium and cobalt can be found, the sodium-ion battery could be truly competitive with lithium-ion batteries.”