NASA and Nissan team up to develop solid-state batteries

Recently, NASA and Nissan announced that they have teamed up to make solid-state batteries a commercial reality. What are solid-state batteries, why are NASA and Nissan teaming up, and is the safety of solid-state batteries a myth?

What are solid-state batteries?

If there is one fact that remains true for almost all batteries in existence, it’s that batteries use a liquid electrolyte. While this liquid may be in the form of a paste, a gel, or an actual pourable fluid, the need for a liquid comes down to how chemical batteries work.

To put it simply, different metals have different electrical potentials which can be paired to create a large potential (such as copper and tin). If these two metals are submerged in acid, electrons will build upon the metal with the lower potential, and this is aided by the use of the acidic electrolyte (this allows for ions to transport between the two metals). When the two metals are connected (completing a circuit), the electrons from the lower potential metal will rush to the higher potential through the external circuit to the higher potential metal. This allows for more electrons to build upon the lower potential metal, and thus the cycle continues. In this example, the energy stored in the battery is the metals and the electrolyte.

However, a solid-state battery is constructed entirely using solid compounds with no liquid electrolyte needed. Contrary to belief, solid-state batteries have been known since the 19th century, but they have historically been fragile, have very low energy densities, and are extremely complex to manufacture.

Using a solid electrolyte presents multiple advantages over liquid electrolyte batteries including improved safety and decreased weight. Regarding safety, the lack of a liquid electrolyte means that breaking the battery does not result in a spillage of an acidic solution. Furthermore, using a solid electrolyte also prevents easy to form short-circuits where one electrode is compressed into the other electrode. Many solid-state batteries currently being researched focus on ceramic materials. They typically crack and shatter instead of bending and deforming, meaning they pose a lower risk of electrode shorting.

If researchers can increase the energy density of solid-state batteries, then they pose a very viable option for EVs as not only would they be considered “more safe”, but they would also be lighter. This would help increase the range of vehicles while also decreasing charging times (liquid electrolytic batteries can grow metal fingers between electrodes if charged too quickly resulting in internal short circuits).

NASA and Nissan team up to develop solid-state batteries

Realising the benefits of solid-state battery technologies, NASA has teamed up with the automotive manufacturer Nissan to try and develop batteries ideal for commercial and aerospace use. The technology being developed by the joint venture will allow for their solid-state lithium battery to be fully recharged in 15 minutes which is significantly faster than current liquid electrolytic lithium batteries. Furthermore, the new battery will be able to handle far more charging cycles that current lithium-ion batteries can handle. The new battery is expected to be launched to the public by 2024 with full-scale production beginning in 2028.

The need for Nissan to produce a solid-state battery is obvious when considering that they are moving into the electric vehicle market, but how would such batteries benefit NASA projects? As it turns out, solid-state batteries would provide an immense amount of use to NASA for most of their projects when considering the environments, they operate in and what they need.

For example, equipment in space that is required to store energy can easily do so with solid-state batteries as they are not affected by the vacuum of space (whereas a liquid electrolyte battery would swell and expand). Secondly, NASA's plans to revisit the moon will need to make the most of each trip, and solid-state batteries allow moon buggies to have extended ranges. The use of such batteries can also reduce the need for more dangerous energy sources such as radioisotope thermoelectric generators which would pose a risk to manned missions.

Is the safety of solid-state batteries a myth?

One hype that solid-state batteries get often is that they are far safer than current battery technologies using liquid electrolytes. This opinion is given weight by demonstrating how piercing a lithium battery causes a stream of hydrogen gas to form that eventually catches fire. In contrast, a pierced solid-state battery appears to show no reaction.

While this may be true, there is one fact about all batteries that will never change: energy is energy. The construction of a battery can contribute to a more catastrophic failure (such as how lithium-ion batteries degrade and catch fire). Still, no matter how a battery is constructed, the energy that it can deliver will be released during a failure one way or another.

This has been demonstrated in one research paper describing how a short-circuit in a solid-state battery will see its temperature increase far beyond that of typical lithium-ion batteries. While the battery itself is not flammable, the surrounding materials may be, leading to a very hot fire.

Thus, solid-state batteries may be safer with regard to puncture damage, but the short-circuit of a high capacity battery will result in extremely large current flow, overheating components, and fires from the extreme rise in temperature of the battery.