Researchers at NASA are chasing a dream — advanced solid-state batteries that can power electric aircraft. Its Solid State Architecture Batteries for Enhanced Rechargeability and Safety (SABERS) program is centered at the agency’s Glenn Research Center in Cleveland, but is collaborating with researchers at Georgia Tech, Argonne National Laboratory, and Pacific Northwest National Laboratory.
In a press release, NASA says that unlike conventional lithium-ion batteries, solid-state batteries do not contain the liquids that can lead to overheating, fire, and loss of charge over time — issues that may sound familiar to anyone who uses large electronics. In addition, solid-state batteries can hold more energy and perform better in stressful environments than conventional lithium ion batteries.
“SABERS continues to exceed its goals,” says Rocco Viggiano, principal investigator for SABERS. “We’re starting to approach this new frontier of battery research that could do so much more than lithium ion batteries can. The possibilities are pretty incredible.”
Battery performance is a key aspect in the development of more sustainable electric aircraft, whose batteries must be able to store the huge amounts of energy required to power an aircraft while being as light at possible. The amount of energy a battery can store is only one side of the equation, however. In addition, a battery that is suitable for aviation purposes must be able to discharge its stored energy at a rate sufficient to power an electric aircraft or unmanned aerial vehicle.
NASA says a battery is like a bucket. Its capacity is how much the bucket can hold while its power is how fast the bucket can be emptied. To power an electric aircraft, the battery must discharge its energy, or empty its bucket, at an extraordinarily fast rate.
SABERS has been experimenting with innovative new materials not previously used in batteries, such as sulfur and selenium, which have produced significant progress in power discharge. During the past year, the team successfully increased their battery’s discharge rate by a factor of 10 and then by another factor of 5 again.
Those new materials led to additional design changes. The SABERS team realized solid-state architecture allowed them to change the construction and packaging of their battery to save weight and increase the energy it can store. A bigger bucket, in other words.
Instead of housing each individual battery cell inside its own steel casing the way conventional lithium-ion batteries do, all the cells in SABERS’s battery can be stacked vertically inside one casing. Thanks in part to this novel design, SABERS has demonstrated that its solid-state batteries can power have an energy density of 500 watt-hours per kilogram — double that of a traditional electric car battery. [It should be noted that Samsung say it also has a solid-state battery with a high energy density.]
“Not only does this design eliminate 30 to 40 percent of the battery’s weight, it also allows us to double or even triple the energy it can store, far exceeding the capabilities of lithium-ion batteries that are considered to be the state of the art,” Viggiano said.
Safety is another key requirement for the use of batteries in electric aircraft. Unlike liquid batteries, solid-state batteries do not catch fire when they malfunction and can still operate when damaged, making them attractive for use in aviation.
SABERS researchers have tested their battery under different pressures and temperatures, and have found it can operate in temperatures nearly twice as hot as lithium-ion batteries without as much cooling technology. The team is continuing to test it under even hotter conditions. Not surprisingly, this research has generated substantial interest from government, industry, and academia.
This year, the main objective for SABERS was to show the properties of its solid-state battery meet its energy and safety targets while demonstrating it can safely operate under realistic conditions and at maximum power. Its research partners at Georgia Tech help pioneer different methodologies that can improve the solid-state batteries and make them more for practical for use in aviation applications.
“Georgia Tech has a big focus on micro-mechanics of how the cell changes during operation. That helped us look at the pressures inside the battery, which then helped us improve the battery even more,” said Viggiano. “It also led us to understand from a practical standpoint how to manufacture a cell like this, and it led us to some other improved design configurations.”
SABERS has also engaged the expertise of multiple NASA centers and projects to achieve its objectives. In addition, its work has piqued the interest of the Subsonic Single Aft Engine program, which is working toward the development of an advanced hybrid-electric concept aircraft.
“We’ve had a lot of productive discussions on how others at NASA could leverage our work and potentially use our battery,” said Viggiano. “It’s been extremely rewarding to think about what could possibly come from it. We’ve seen SABERS grow from an idea we had a lunch one day to, potentially, an energy solution for aeronautics.”
SABERS is part of the Convergent Aeronautics Solutions project, which is designed to give NASA researchers the resources they need to determine whether their ideas to solve some of aviation’s biggest technical challenges are feasible, and perhaps worthy of additional pursuit within NASA or by industry.
To hear reactionaries tell it, nothing government does is any good. Private industry is always better, smarter, faster, cheaper, and more efficient. And yet, research such as that being pursued by the SABERS program often leads to breakthroughs which are later shared with private industry and become part of commercial products.
It is convenient to overlook the role that pure research operations like SABERS plays in making discoveries that are too costly or too massive for private industry, with its focus on the bottom line and the next quarterly report, to accomplish on its own.
While the NASA work focuses on aircraft, the lessons learned will have enormous implications for society at large. Imagine a battery for an electric car that has double the energy density of today’s batteries and weighs 40% less. How might that change the equation when it comes to moving the EV revolution forward?
Then consider the NASA battery uses no cobalt, nickel, or manganese — all components of most conventional lithium-ion batteries that are in short supply and rising steadily in cost. America needs more basic scientific research. The SABERS program shows the reason why.
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