A Solid Sodium Battery with Better Performance and Improved Safety

Researchers from Empa and the University of Geneva have developed an initial prototype of a solid sodium battery with the potential to store extra energy.

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Batteries are everywhere including in your mobile phones, cameras, laptops, electric cars etc. And to meet customer’s requirement, they are designed lightweight, more powerful and efficient.

Most of the batteries are designed using lithium-ions which consists of a flammable liquid, which may represent a safety hazard when the battery is abused.

Now to fulfill growing demand for batteries and to overcome safety demand of conventional batteries, scientists at the University of Geneva (UNIGE), Switzerland have developed a new battery prototype. Scientists dubbed their battery as all-solid-state.

It has the potential to store more energy while maintaining high safety and reliability levels. Moreover, it is based on sodium, thus cheap in cost than lithium-based batteries.

Here, scientists focused on the advantages of a “solid” battery to cope with the heightened demand from emerging markets and to make batteries with even better performance. Unlike lithium-based batteries, this new solid sodium battery uses the solid electrolyte that enables the use of a metal anode by blocking the formation of dendrites. This makes it possible to store more energy while guaranteeing safety.

Hans Hagemann, professor in the Physical Chemistry Department in UNIGE said, “But we still had to find a suitable solid ionic conductor that, as well as being non-toxic, was chemically and thermally stable, and that would allow the sodium to move easily between the anode and the cathode.”

A boron-based substance, a closo-borane inside the battery enabled the sodium ions to circulate freely. And as the closo-borane is an inorganic conductor, it removes the risk of the battery catching fire while recharging.

Léo Duchêne, a researcher at Empa’s Materials for Energy Conversion Laboratory said, “The difficulty was establishing close contact between the battery’s three layers: the anode, consisting of solid metallic sodium; the cathode, a mixed sodium chromium oxide; and the electrolyte, the closo-borane.”

During experiments, scientists dissolved part of the battery electrolyte in a solvent before adding the sodium chromium oxide powder. Once the dissolvable had vanished, they stacked the cathode powder composite with the electrolyte and anode, packing the different layers to frame the battery.

They found that the electrochemical stability of the electrolyte is able to withstand three volts, whereas many solid electrolytes previously studied are damaged at the same voltage. In addition, 85% of its energy capacity was functional.

Scientists suggest that they still have to test this solid sodium battery at room temperature so we can confirm whether or not dendrites form while increasing the voltage even more. Our experiments are still ongoing.