Take a look at any consumer electronic device made in the last decade and there’s a good chance that it’s powered by a lithium-ion (Li-Ion) battery. Small and compact, lithium-ion batteries are amongst the best energy storage solutions when considering cost, energy storage, and size.
Lithium-ion batteries in consumer devices can be susceptible to combustion. Image used courtesy of Shmuel De-Leon and Battery University
Li-Ion batteries, however, are not suited for many situations because their chemical makeup makes them dangerously susceptible to combustion. Certain applications, like space exploration, can only use LiBs with special equipment, which can create a safe operating environment for the battery.
JAXA is now looking at ways to get around this shortcoming for space exploration, announcing that it will begin experimentation with all solid-state lithium-ion batteries (ASSLBs) in space in 2021.
All Solid-state Lithium-Ion Batteries
Conventional lithium-ion batteries consist of an anode, cathode, separator, and liquid electrolyte solution, which is generally a solvent meant to facilitate the flow of ions between the anode and the cathode. As AAC contributor Robin Mitchell explains, this liquid electrolyte is precisely the part of the battery that makes lithium-ion dangerous: it is susceptible to swelling due to temperature changes and eventually combustion if the anode and cathode short.
Architectural differences between lithium-ion batteries and solid-state lithium-ion batteries. Image used courtesy of Samsung
ASSLBs, on the other hand, work with a similar configuration, but the electrolyte is a solid structure. The solid structure of the electrolyte leads to improved stability and better safety. Even if the electrolyte is damaged, it still maintains form, making it less susceptible to a short.
Li-ion batteries have the same capacity as smaller solid-state batteries. Image used courtesy of Samsung
Beyond this, solid-state batteries also boast higher energy densities than conventional solutions. Stanford researchers have found that liquid-electrolyte batteries are unable to use metal anodes as the metal and the liquid react, forming microstructures on the anode that can lead to combustion.
Solid-state batteries, on the other hand, have been called the “holy grail” for transportation technology because they don’t experience this problem. Using a metal anode theoretically allows for energy densities up to three times higher than conventional solutions.
JAXA Plans to Send ASSLBs to Space
In an environment as harsh as space, safety in electronics is absolutely paramount, meaning that conventional lithium-ion batteries are not necessarily the best choice. JAXA is well aware of this and made headlines this week when it announced that it is looking to test the feasibility of solid-state batteries in space as early as fall 2021.
Sample of an ASSLB. Image used courtesy of Hitachi Zosen Corporation and JAXA
To study the efficacy of ASSLBs in space, JAXA will be conducting an on-orbit experiment to evaluate and verify a prototype of the battery’s behavior. For the experiment, JAXA engineers will install an ASSLB in a support system payload on the ISS and observe the battery’s behavior, capacity, and output over the course of six months.
Rendering of the i-SEEP/SPySE, pointing out where an ASSLB would be installed. Image used courtesy of JAXA
The battery itself will be about 25 g with a form factor of 65 mm x 52 mm x 2.7 mm with each cell having a capacity of about 140 mAh. The engineers will arrange fifteen of these cells in parallel to achieve about 2.1 Ah of capacity.
Powering Space Exploration
Developing new, safer, and higher-capacity energy storage solutions can have huge benefits both in space and here on earth. In addition to their higher capacity, ASSLBs are less susceptible to catching fire, meaning they can be installed in much tighter areas without worry. In this way, designs have the two-pronged benefit of fitting more cells in the same area while also experiencing more capacity.
Should JAXA’s experiments prove fruitful, the agency hopes that ASSLBs can be used in future planetary rovers for the next generation of space exploration.