A vast majority of electronic equipment running on batteries rely on the Lithium-ion technology for their electrode material. Since Lithium is relatively rare, its mining and refining make it an expensive material to use. This has led scientists to search for a cheaper alternative, and they have turned to the cheapest substance available, the common salt. A team from Stanford has developed a battery based on Sodium-ion whose cost per storage capacity is far lower than that of the existing batteries based on Lithium-ion.
Salt, being nearly omni-present in our oceans, together with its ability to carry charge, is a near-perfect candidate for low-cost energy storage. Many forms of Sodium-based batteries are now available, some with a unique design of anode made from a carbonized oak leaf to a more standard format for use in laptops. According to the lead researcher of the Stanford study, Zhenan Bao, although Lithium offers a superior performance, its rarity and high cost is leading people to search for materials such as Sodium to build low-cost but high performance batteries.
The research team uses a battery with Sodium salt cathode and a Phosphorous anode—materials that are abundant in nature. Near the cathode, Sodium ions combine with oppositely charged myo-inositol ions. To improve the charge-recharge cycle, the researchers had to study the forces at work at atomic-level, when Sodium ions detach and attach from the cathode.
The newly developed Sodium-ion battery has a reversible capacity of 484 mAh/gm, which translates to an energy density of 726 Wh/Kg. The research team claims the energy efficiency of the new batteries to be greater than 87%. Regarding the cost comparison between similar storage capacity batteries, the team says the new Sodium-ion battery will cost less than 80% of the cost of a Lithium-ion battery of similar storage capacity.
To obtain more performance from the Sodium-ion battery, the research team is planning to work more on its phosphorous anode. In addition, to be able to dictate the size of the Sodium-ion battery necessary to store a certain amount of energy, the team also plans to examine the volumetric energy density in comparison to that of Lithium-ion batteries.
Faradion Limited, of Sheffield, UK, has developed Sodium-ion technology that offers energy densities in batteries far exceeding those of other known Sodium-ion technologies. In addition, their new technology produces energy densities that exceed those from popular Lithium-ion materials such as Lithium iron phosphate. Faradion makes current collectors in their Sodium-ion batteries from Aluminum rather than from the more expensive copper that Lithium cells use.
According to electrochemical tests Faradion has conducted, they list the advantages of the Sodium-ion materials over conventional Lithium-ion materials as follows—better rate capability, better thermal stability (safer), improved transport safety, improved cycle life, and similar shelf life. Further, Sodium-ion material processing is similar to that followed for Lithium-ion materials at every step, beginning from synthesis of the active materials to the processing of electrodes.
Innovate UK co-funds a project for Williams Advanced Engineering, where the novel Sodium-ion technology from Faradion is currently being employed to build 3 Ah prismatic cells. Williams is further incorporating these cells into batteries for commercial use.