08-27 solid-state sodium ion battery

[Image above] Lithium is not the only element from which batteries can be made. A sodium-ion battery lights up this LED! Credit: Yamauchi et al.Journal of the American Ceramic Society/Wiley

If you are an avid reader of CTT, you likely saw the news last week that the September issue of the Bulletin is now online.

This month’s theme is energy storage technologies, specifically batteries.

Batteries are an important energy storage technology that will help reduce our dependence on fossil fuels and slow the rate of global climate change.

Fossil fuels have been used in transportation and electricity generation for well over 100 years.  They are relatively inexpensive and dependable, and they have high energy density. But carbon dioxide release into the atmosphere when fossil fuels are burned is linked to retention of thermal energy by the earth.

Harvesting energy from the environment and converting it to electricity or hydrogen has the potential to greatly reduce consumption of fossil fuels. With increased production and usage, the cost of generating electricity from wind and solar are coming down to rival costs of generation from coal and natural gas.

But the wind does not always blow and the sun does not shine at night. So, we must be able to store energy reliably and cost-effectively to be able to maintain our on-demand electricity supply.

And that is the role batteries play.

Batteries store energy generated from these renewable resources for use at a later time. Currently, lithium-ion (Li-ion) is the leading battery technology. However, though these batteries have excellent energy density and cyclability, they are not without their challenges.

One vulnerability of Li-ion batteries is the danger of thermal runaway, a situation in which Li-ion batteries catch fire. There are numerous examples of thermal runaway happening in many consumer and commercial products. Ceramic scientists and engineers are working to improve the safety of Li-ion batteries by replacing polymeric electrolytes with solid-state ceramic electrolytes. Yet even when the safety issues are addressed, batteries made completely from nonlithium materials are needed due to the relatively low global supply of lithium (as reported in a previous CTT).

Sodium-ion (Na-ion) batteries offer a possible solution. Sodium, which is directly below lithium on the periodic table, has high energy density and is a significantly more abundant element. Though current Na-ion batteries operate at high temperatures of 300–350°C, which is not practical for transportation and not desirable for utility-scale electricity storage, operation temperature is expected to decrease as research continues.

Materials for the cathode, electrolyte, and anode of all-solid-state Na-ion batteries are known and the subject of research for quite some time (I researched β” alumina in the 1980s). However, there has been limited success assembling these materials into a practical, low-temperature solid-state battery.

In a recent article in the Journal of the American Ceramic Society, researchers from Nippon Electric Glass and Nagaoka University of Technology report they produced an all solid-state Na-ion battery that operates at atmospheric pressure. Their research is significant on many fronts, including

  1. The electrolyte and glass-ceramic cathode materials are low cost and readily available, and can be co-fired at 550°C (a relatively low temperature) and assembled into a standard button battery format,
  2. The resulting battery is stable with no cathode delamination and minimal capacity loss when tested for over 600 charge-discharge cycles,
  3. The energy density is approaching that of Li-ion batteries in their nonoptimized cell, and
  4. It recovers from overcharging (one of the causes of Li-ion battery fires) with minimal decrease in performance.
Configuration of the all-solid-state battery used in this study. Credit: Yamauchi et al.Journal of the American Ceramic Society/Wiley

The researchers discuss the structure and electrochemistry of their cathode material with respect to firing conditions and cell operating conditions. They also point to future research to determine the mechanisms that lead to the good performance of the cathode and to optimize the battery construction.

If these researchers and others are successful in optimizing Na-ion battery technology and scaling it for transportation and utility-scale applications, it could revolutionize global energy usage.

The paper, published in Journal of the American Ceramic Society, is “Pressureless all-solid-state sodium-ion battery consisting of sodium iron pyrophosphate glass-ceramic cathode and β″‐alumina solid electrolyte composite” (DOI: 10.1111/jace.16607).