Technologue Might this solid-state battery finally democratize EVs?

Frank Markus Technologue

Might this solid-state battery finally democratize EVs?

ichael Faraday discovered solid electrolytes

Min 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 “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 10-year-old Stanford University battery startup QuantumScape appears to have hit a “home run 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 lithiumion 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, there’s 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 lithiumnickel-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 graphitebased 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 those of 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 it easier and cheaper to manufacture.

Perhaps the best indication of QuantumScape’s viability is the fact that Volkswagen has invested $300 million of the $1.5 billion in committed capital the company has raised. On the call unveiling the technology, Jürgen Leohold, QuantumScape 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. Q

The “ceramic” separator shown above is obviously flexible. It also represents the size envisioned for production. Individual cells are roughly sized like a playing card, with the battery module consisting of a stack about as thick as a deck of cards. They’ll need to be packed with room to expand, as the lithium plating causes each cell to grow, but only in the direction perpendicular to the “card” face.