Tag Archives: Sodium Ion

The Battery of the Future — Sodium Ion

Currently, Lithium-ion batteries rule the roost. However, there are several disadvantages to this technology. The first is that Lithium is not an abundant material. Compared to this, Sodium is one of the most abundantly available materials on the earth, therefore it is cheap. That makes it the most prime promising candidate for new battery technology. So far, however, the limited performance of Sodium-ion batteries has not allowed them a large-scale integration into the industry.

PNNL, or the Pacific Northwest National Laboratory, of the Department of Energy, is about to turn the tides in favor of Sodium-ion technology. They are in the process of developing a Sodium-ion battery that has excelled in laboratory tests for extended longevity. By ingeniously changing the ingredients of the liquid core of the battery, they have been able to overcome the performance issues that have plagued this technology so far. They have described their findings in the journal Nature Energy, and it is a promising recipe for a battery type that may one day replace Lithium-ion.

According to the lead author of the team at PNNL, they have shown in principle that Sodium-ion battery technology can be long-lasting and environmentally friendly. And all this is due to the use of the right salt for the electrolyte.

Batteries require an electrolyte that helps in keeping the energy flowing. By dissolving salts in a solvent, the electrolyte forms charged ions that flow between the two electrodes. As time passes, the charged ions and electrochemical reactions helping to keep the energy flowing get slower, and the battery is unable to recharge anymore. In the present Sodium-ion battery technologies, this process was happening much faster than in Lithium-ion batteries of similar construction.

A battery loses its ability to charge itself through repeated cycles of charging and discharging. The new battery technology developed by PNNL can hold its ability to be charged far longer than the present Sodium-ion batteries can.

The team at PNNL approached the problem by first removing the liquid solution and the salt solution in it and replacing it with a new electrolyte recipe. Laboratory tests proved the design to be durable, being able to hold up to 90 percent of its cell capacity even after 300 cycles of charges and discharges. This is significantly higher than the present chemistry of Sodium-ion batteries available today.

The present chemistry of the Sodium-ion batteries causes the dissolution of the protective film on the anode or the negative electrode over time. The film allows Sodium ions to pass through while preserving the life of the battery, and therefore, quite significantly critical. The PNNL technology protects this film by stabilizing it. Additionally, the new electrolyte places an ultra-thin protective layer on the cathode or positive electrode, thereby helping to further contribute to the stability of the entire unit.

The new electrolyte that PNNL has developed for the Sodium-ion batteries is a natural fire-extinguishing solution. It also remains non-changing with temperature excursions, making the battery operable at high temperatures. The key to this feature is the ultra-thin protection layer the electrolyte forms on the anode. Once formed, the thin layer remains a durable cover, allowing the long cycle life of the battery.

A Cheaper Alternative for Batteries—Sodium Ion

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.