One type of battery that is still under development here on Earth could break into the moon in 2021 aboard a commercial lunar lander. The Japanese start-up plans to be the first to test a solid-state battery on the surface of the Moon in the hope that this emerging technology can help solve the challenge of storing energy outside the world.
Countries and companies like the ispace struggle to send robots and humans back to the moon – and they'll need energy to power their rovers, their habitats, and other electronic devices once they get there. Solar energy is an option, but areas of the lunar surface will be out for weeks without sunlight. In those days without the sun, temperatures drop and solar panels receive no light. Finding a battery that can withstand extreme temperature fluctuations and store energy efficiently could be a great advantage for exploring the moon.
Solid state batteries could be a promising solution. This is a busy version of traditional lithium-ion batteries found in iPhones, Tesla and essentially all batteries. Lithium-ion batteries depend on a flammable liquid, the electrolyte, to transport charged particles, called ions, from one battery side to the other. Unfortunately, this fluid can cause problems even on our planet. At high temperatures, electrolytes can go up in flames and, for example, cause phones to explode. At low temperatures, the liquid freezes to a solid and the battery shuts off completely.
In solid-state batteries, the electrolyte is a solid material that has been carefully designed to support the reciprocation behavior of ions, according to Francesco Pagani, a graduate student of solid-state batteries at the Swiss Federal Laboratories of Materials Science and Technology. Instead of surrounding everything with liquid, the different parts are stacked in solid layers, which also makes the battery more compact.
Solid-state batteries are designed to absorb more energy and charge faster than conventional Li-ion batteries. Theoretically, they could also better withstand the dramatic changes in the temperature of the moon from 260 degrees Fahrenheit (127 degrees Celsius) in the sunlight to -280 degrees Fahrenheit (-173 degrees Celsius) in the shade. The battery does not go up in flames due to heat, and the electrolyte is already designed as a solid that ions can pass through. While the cold charges slower in a cold weather, they have at least the potential to survive in space, whereas a typical lithium-ion battery would never do so.
The proposed Moon battery is manufactured by the Japanese company NGK Spark Plug. The companies have not yet determined the exact specifications of the Moon battery, but say that it will have a ceramic electrolyte. (Ceramics is one of the most popular options for solid electrolytes because it is quite stable.) The plan is to do some basic testing just to see if the battery can survive in the vacuum of space on the moon. Hopefully, the experiment will expand the possibilities of batteries in space, says a spokesman for the NGK spark plug.
The use of solid-state batteries in space, according to Rao Surampudi, manager of the Power Systems program, is nothing new in NASA's Jet Propulsion Laboratory and author of several reports on space energy storage. "We started working on solid-state batteries in 1991," he says. "We are still working on it."
The key challenge is battery life – or how often you can charge a battery before it dies – is incredibly limited in solid-state batteries. This will not be very helpful in space, where things take a long time. "You can replace the battery in your car or cellphone, but you can not reset the battery in a spacecraft," adds Surampudi.
The poor cycle life is also an important reason why solid-state batteries did not hit the ground here on Earth. Many companies are trying to commercialize them, but you still can not buy solid-state batteries for your phone or electric vehicle. At the moment, we can only make small solid-state batteries, and most only last 18 months. They are also incredibly expensive to manufacture, much less mass produced. "It's been promised that over the next two to three years solid-state batteries will hit the market over the next four to five years, and investors are becoming increasingly impatient with solid state progress," analyst analyst McClenny Navigant Research analysts said on battery research, told The Verge . Realistically, McClenny does not believe that solid-state batteries will be a commercial option until the early or mid-2020s.
Similarly skeptical is Surampudi. The technology for solid-state batteries is still fairly immature, and it will probably take five to ten years before they have been sufficiently refined for practical application. It requires us to "save $ 100 million" to invest in further research.
Meanwhile, it is possible to design conventional lithium-ion batteries to work well in space. Numerous lithium-ion batteries are used on board the International Space Station and are manufactured in such a way that unexpected explosions do not injure astronauts or impair safety. According to Surampudi, who helped develop this technology, it was traditional (albeit very sophisticated) lithium ions that drove the recently deceased Opportunity Mars Rover for 15 years. His team developed special thermal management systems to facilitate the handling of batteries with heat and cold and tested them for three years at extreme temperatures.
That does not mean that lithium ions are the end of everything. "It's time to replace lithium-ion," says Surampudi. "This country has to invest and we have to find the next best battery. The development of batteries is not easy, because the low-hanging fruits have long been taken. "
We'll see what happens when NGK's solid-state battery goes into space, and it'll be at least a few years before that. ispace plans to launch its first mission, a lunar orbit, aboard a SpaceX Falcon 9 rocket sometime in 2020. If successful, the company will launch a landing and rover combination (which will carry the battery) on another Falcon 9 in 2021
Ultimately, ispace's long-term vision is to create a thriving, sustainable community on the Moon in which people live and interact with robotic spacecraft. To make this possible, clever energy storage solutions have to be developed. Solid state batteries could be a part of this future, but it may take a while for them to succeed.