Michael Faraday discovered solid electrolytes in the 1830s, and the solid-state battery has promised to be the Next Big Electrical Thing almost ever since.
The idea frequently makes news that I resist reporting because, to borrow a baseball metaphor, these battery “batters” too often start their home run trot before realizing it’s just a fly ball to the warning track. But noted scientist Paul Albertus says that 10-year-old Stanford University battery startup QuantumScape appears to have hit a “homerun in terms of their solid-state battery performance data.”
Here’s the deal with solid-state: These batteries have long promised to solve the thorniest issues preventing widespread battery-electric vehicle adoption while providing better performance on many metrics.
Liquid or gel electrolytes in today’s batteries are flammable and can freeze, so they require costly, heavy warming, cooling, and safety monitoring systems. Graphite-based anode materials engineered to capture the lithium ions during charging are bulky and heavy, and side reactions within this material compromise performance over time. Charge a lithium-ion battery too fast for too long, and lithium metal spikes (dendrites) can form on the anode and pierce the permeable “separator” through which the ions flow, short-circuiting the cell. Solid-state does away with the liquid electrolyte, removing the fire risk.
So why hasn’t solid-state happened? All of the approaches so far have either required high temperatures to operate or (more frequently) haven’t survived the required 800 cycles while retaining 80 percent capacity, or they have required pricey and delicate metallic lithium on the anode, which kills cost, makes the batteries heavy, and doesn’t contribute to energy storage. So, a lot to overcome.
QuantumScape sought Albertus’ opinion because the former head of the Department of Energy’s ARPA-E solid-state battery program is now a professional skeptic on the subject.
QuantumScape impressed Albertus by reporting performance results from multiple samples that were commercially sized like a playing card, not tiny single specimens. They also provided charge/discharge cycling data from complete cells, not individual layers, and tested them at significant current density (3 milliamps/square centimeter).
The test cells were also operating under light pressure (3 atmospheres versus the 20 required for Samsung’s solid-state design to work) and at 30 degrees C (they work down to -25 and up to 80, while rivals only work at high temperatures). Even better, QuantumScape’s batteries appear to be demonstrating just 10-15 percent capacity fade after 800 cycles (240,000 miles)—quadrupling rivals’ performance.
What’s more, QuantumScape’s design eliminates the anode entirely, reducing size and mass to achieve upward of 400 Wh/kg and more than 1,000 Wh/liter. Using a conventional lithium-nickel-manganese-cobalt (NMC811) cathode and a flexible ceramic separator of undisclosed chemistry, lithium ions from the cathode form a metal film directly on the current collector when charging. This causes the cell to expand, so the battery pack must allow for this.
Lithium forms on the current collector faster than it can on a graphite-based anode, and the ceramic separator resists dendrite formation, making higher charging rates safe. Charging to 80 percent capacity in 15 minutes is easily doable, as the ceramic separator can tolerate high current densities. Ready for the biggest news? A full charge in two minutes seems feasible because the separator has been shown to tolerate even more extreme current densities than some of today’s fastest-charging lithium-ion batteries tolerate. That’s quicker than pumping gas, for you playing at home.
More promising news: That ceramic separator can be produced using existing roll-to-roll coating technology, and eliminating the metallic lithium anode required in some solid-state concepts makes them easier and cheaper to manufacture.
Perhaps the best indication of QuantumScape’s viability is the fact that VW has invested $300 million of the $1.5 billion in committed capital the company has raised. On the call unveiling the technology, Jürgen Leohold, QS board member and former head of research at VW, opined that the batteries will enter production in 2024-2025 on premium products first. We presume the Audi E-Tron GT, Porsche Taycan, and a promised 2025 EV from Bentley are prime candidates, with costs coming down as solid-state battery manufacturing matures.
To recap: Five years ago, QuantumScape quietly hit a solid single by identifying its ceramic separator and anodeless design that enables an 80 percent increase in range for a given size battery. In the years since, it’s been plugging away to perfect fast charging, long life, and operation across a wide temperature range while also focusing on manufacturability. Whether you count that as a towering Babe Ruth grand slam or a bases-loaded double to the gap, this battery might mark a tipping point.
Solid-State Batteries FAQ
What Is a Solid-State Battery? Technically it’s a battery that doesn’t use a liquid electrolyte. You may also see them referred to as all-solid-state batteries, or ASSBs, to differentiate them from quasi-solid electrolyte batteries with separators that involve some gel or liquid. Materials that have been proposed for use as solid electrolytes in ASSBs include ceramics (a broad definition for oxides, sulfides, phosphates), and solid polymers.
What companies are developing solid state batteries? Recent headlines have been made by QuantumScape and the Toyota/Panasonic venture. Solid Power is a spinoff from Colorado University Boulder that has been working with Ford and BMW on an iron-sulfur chemistry ASSB. Sakti3 spun out of research from the University of Michigan and was purchased by Dyson, but later abandoned licensing of patents. Its founder, however, has turned up working on solid-state batteries for Fisker. Samsung has also made news fairly recently, with a solid-state battery using a silver-carbon anode.
Does Tesla use solid state batteries? Not yet. And we’ve heard few specifics about the 400 Wh/kg battery technology alluded coming within three to four years during his battery-day announcement back in September 2020. He’s hinted at silicon nanowire technology, but this is not a solid-state solution.
Is QuantumScape publicly traded? Yes, the New York Stock Exchange welcomed ticker symbol QS on November 30 in an initial public offering (IPO) following a merger with the investment company Kensington Capital Acquisition. Revenues from this merger are reported at $680 million.