QuantumScape releases performance data for its solid-state battery technology

09 December 2020

QuantumScape Corporation, a Volkswagen Group-backed developer of next-generation solid-state lithium-metal batteries for use in electric vehicles (EVs), released performance data demonstrating that its technology addresses fundamental issues holding back widespread adoption of high-energy density solid-state batteries, including charge time (current density), cycle life, safety, and operating temperature.

A commercially viable solid-state lithium-metal battery is an advancement that the battery industry has pursued for decades, as it holds the promise of a step function increase in energy density over conventional lithium-ion batteries, enabling electric vehicles with a driving range comparable to combustion engine-based vehicles. QuantumScape’s solid-state battery is designed to enable up to 80% longer range compared to today’s lithium-ion batteries.

Previous attempts to create a solid-state separator capable of working with lithium metal at high rates of power generally required compromising other aspects of the cell (cycle life, operating temperature, safety, cathode loading, or excess lithium in the anode). QuantumScape’s newly-released results, based on testing of single-layer battery cells, show its solid-state separators are capable of working at very high rates of power, enabling a 15-minute charge to 80% capacity, faster than either conventional battery or alternative solid-state approaches are capable of delivering.

QuantumScape single-layer solid-state pouch cell.

In addition, the data shows QuantumScape battery technology is capable of lasting hundreds of thousands of miles, and is designed to operate at a wide range of temperatures, including results that show operation at -30 degrees Celsius.

The tested cells were large-area single-layer pouch cells in the target commercial form factor with zero excess lithium on the anode and thick cathodes (>3mAh/cm2), running at rates of one-hour charge and discharge (1C charge and 1C discharge) at 30 degrees Celsius. These tests demonstrated robust performance of these single layer pouch cells even at these high rates, resulting in retained capacity of greater than 80% after 800 cycles (demonstrating high columbic efficiency of greater than 99.97%).

QuantumScape ceramic solid-state separator.

The hardest part about making a working solid-state battery is the need to simultaneously meet the requirements of high energy density (1,000 Wh/L), fast charge (i.e., high current density), long cycle life (greater than 800 cycles), and wide temperature-range operation. This data shows QuantumScape’s cells meet all of these requirements, something that has never before been reported. If QuantumScape can get this technology into mass production, it holds the potential to transform the industry.

—Dr. Stan Whittingham, co-inventor of the lithium-ion battery and winner of the 2019 Nobel prize in chemistry

These results blow away what was previously thought to be possible in a solid-state battery. Supporting high enough current density to enable fast charge without forming dendrites has long been a holy grail of the industry. This data shows the capability to charge to 80% capacity in 15 minutes, corresponding to an astonishingly high rate of lithium deposition of up to a micron per minute.

—Venkat Viswanathan, battery expert and professor of materials science at Carnegie-Mellon University

QuantumScape’s team of scientists have worked over the past decade to create the next generation of battery technology: solid-state batteries with lithium-metal anodes. With processes and materials protected by over 200 patents and applications, QuantumScape’s proprietary solid-state separator replaces the organic separator used in conventional cells, enabling the elimination of the carbon or carbon/silicon anode and the realization of an “anode-less” architecture, with zero excess lithium.

In such an architecture, an anode of pure metallic lithium is formed in situ when the finished cell is charged, rather than when the cell is produced. Unlike conventional lithium-ion batteries or some other solid-state designs, this architecture delivers high energy density while enabling lower material costs and simplified manufacturing.

Beyond its ability to function at high rates of power while delivering high energy density, other key characteristics of QuantumScape’s solid-state lithium-metal battery technology include:

• Zero excess lithium: In addition to eliminating the carbon or carbon/silicon anode, QuantumScape’s solid-state design further increases energy density because it uses no excess lithium on the anode. Some previous attempts at solid-state batteries used a lithium foil or other deposited-lithium anode, which reduces energy density.

• Long life: Because it eliminates the side reaction between the liquid electrolyte and the carbon in the anode of conventional lithium-ion cells, QuantumScape’s battery technology is designed to last hundreds of thousands of miles of driving. Alternative solid-state approaches with a lithium metal anode typically have not demonstrated the ability to work reliably at close to room temperatures (30 degrees Celsius) with zero excess lithium at high current densities (>3mAh/cm2) for more than a few hundred cycles, and result in a short-circuit or capacity loss before the life target is met. By contrast, today’s test results show that QuantumScape’s battery technology is capable of running for over 800 cycles with greater than 80% capacity retention.

• Low-temperature operation: QuantumScape’s solid-state separator is designed to operate at a wide range of temperatures, and it has been tested to -30 degrees Celsius, temperatures that render some other solid-state designs inoperable.

• Safety: QuantumScape’s solid-state separator is noncombustible and isolates the anode from the cathode even at very high temperatures—much higher than conventional organic separators used in lithium-ion batteries.

Volkswagen has made a corporate funding commitment of $300+ million to date with QuantumScape to promote the joint development of solid-state battery technology. The two established a joint venture in 2018 to prepare for the mass production of solid-state batteries for Volkswagen. Comments Wonderful, if it works. Given VW's history, and the extreme secrecy of Quantumscape, I want to see the pudding before ordering it. No info on wh/kg or metals used? The specs are not that impressive, and without that information they are just uninteresting. That's what I'd call a "just in time Christmas gift". Once scaled up to mass production, this will be the final death blow (coup de grâce) to the gas hogs and diesel. I think it will be a lot slower than anyone thinks. When they come out with mass production in 2027 they won't be so far away in energy density to competitors, especially when you account the battery pack level density including structural rigidity. But that said they probably have much more margin for improvement from that point, but they will need another ~5 years to master that. This means that for at least 15 years current Li-ion tech will still be the dominant production capacity. If it's all that much better than the current Li cells, why not create a manhattan project with the U.S. government and let's get on with it? I worry, as others do, that the energy density, yet to be disclosed, isn't that great. The battery in current pre commercial form has 400 wh/kg but is on a path to 600 wh/kg. The technology and specs have been verified by the top scientists in the field including Dr. Paul Albertus former head to the U.S. DOE ARPA-E, and on the board of directors sits J.B. Strauble of Tesla fame. This is one of the projects funded originally by the DOE ARPA-E to advance battery technology and is the only one to meet their goals. So it is part of a Manhattan Project. This is the real thing. Full video presentation here: https://www.youtube.com/watch?v=dGnPSkXKb0I&feature=youtu.be I have just watched the video presentation, and in my view this is the real deal. I have previously said that in my view simple progress in current lithium batteries would not be sufficient, and that breakthroughs were needed. This is that breakthrough as far as can be determined at this stage. Dr Paul Albertus at around 45:00 into the video gives an indication of some of the ways seemingly decent performance on one or more criteria can be deceptive, as critical metrics are not mentioned, but he and for instance Dr Stan Whittingham on the panel were happy that the data seems comprehensive. A brief summary: They have demonstrated this at the cell level, in about the area of a playing card, and using multiple cells, not just one, to show their data for cycle life, over 800 cycles still well over 80% capacity remaining, temperature, including cold weather, and fast charging at 4C and above. The cathode can be any existing one, they are starting with NMC, but any of the others including cobalt free ones can be used. Remaining is to put this into stacks, around the size of a deck of cards, and to go to production, with the VW group aiming for 1GWh initially, rising to 20GWh in the first wave. Existing battery factories and equipment can be used. The proprietory separator is from inexpensive materials, and there is no anode, the lithium forms that as the cathode discharges. The battery cells do not have to be 'run in' at the factory, which can save substantial amounts of the costs. Nice but do not see anything that LG, SK, CATL ... will not be able to develop in due time. @zorg QuantumScape took five years to work through and alternatives and find their ceramic separator. Since existing equipment in battery production can be used, presumably the plan is to licence out to battery manufacturers, although I have not had a chance to look into their business set up yet. @Davemart Thanks for the video post. Quite a bit of information in the long presentation. My take: they need to expedite this if possible, needed before 2024. The separator looks like it is an engineered, annealed garnet made from lithium, germanium, phosphorous, and sulfur (the video mentions four precursor materials). Based on patent US 20200251741. So the "engineering recipe" is the real trade secret. The prototype battery cell is 85x70 mm, close to the Sion Power cell size (80x91x10mm). As Jagdeep pointed out in the video, these batteries would start at high end applications (expensive autos, SUV, and large trucks). A mixed chemistry battery: part Cobalt free, long life (4000 cycles+) for 20-30 kWh daily use battery and a higher density range extender 40 kWh (still using low cost cathodes) might work for$40k vehicles.

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