Three different groups are five to six years out from fielding solid-state lithium batteries that vastly outperform existing ones, making electric vehicles much more competitive and potentially spurring all sorts of other technological break throughs that have been held up by lagging battery technology.
Despite steady improvements over the past decade in the energy density and lifetimes of lithium-ion batteries, the cells in new EVs still lag behind internal combustion engines on pretty much every performance metric. Most EVs have a range of less than 300 miles, it takes more than an hour to recharge their battery packs, the cells lose nearly a third of their capacity within a decade, and they pose a serious safety risk because of their flammable materials.The solution to these problems has been known for decades: It’s called a solid-state battery, and it’s based on a deceptively simple idea. Instead of a conventional liquid electrolyte—the stuff that ferries lithium ions between electrodes—it uses a solid eloctrolyte. Also, the battery’s negative terminal, called its anode, is made from pure lithium metal. This combination would send its energy density through the roof, enable ultra-fast charging, and would eliminate the risk of battery fires. But for the past 40 years, no one has been able to make a solid-state battery that delivers on this promise—until earlier this year, when a secretive startup called QuantumScape claimed to have solved the problem. Now it has the data to prove it.On Tuesday [December 8, 2020], for the first time, QuantumScape’s cofounder and CEO, Jagdeep Singh, publicly revealed test results for the company’s solid-state battery. Singh says the battery resolved all of the core challenges that have plagued solid-state batteries in the past, such as incredibly short lifetimes and slow charging rate. According to QuantumScape’s data, its cell can charge to 80 percent of capacity in 15 minutes, it retains more than 80 percent of its capacity after 800 charging cycles, it’s noncombustible, and it has a volumetric energy density of more than 1,000 watt-hours per liter at the cell level, which is nearly double the energy density of top-shelf commercial lithium-ion cells.
The article discussed the scientific and engineering basis of the breakthrough at some length.
QuantumScape’s battery cell is about the size and thickness of a playing card. Its cathode, or positive terminal, is made of nickel manganese cobalt oxide, or NMC, a common chemistry in EV batteries today. Its negative electrode, or anode, is made from pure lithium metal—but it's more accurate to say that it doesn’t have an anode at all, since it’s manufactured without one. When the battery discharges during use, all of the lithium flows from the anode to the cathode. The vacancy left on the anode side—thinner than a human hair—is temporarily compressed like an accordion. The process reverses when the battery is charged, and the lithium ions flood into the anode space again. . . .
the key to QuantumScape’s solid-state breakthrough is the flexible ceramic separator that sits between the cathode and the anode. This is the material that puts the “solid” in solid-state. Like the liquid electrolyte that sits between the electrodes in a conventional cell, its main function is to ferry lithium ions from one terminal to the other when the battery charges and discharges. The difference is that the solid separator also acts as a barrier that keeps lithium dendrites—metallic tendrils that form on lithium metal anodes during charge cycles—from snaking between the electrodes and causing a short circuit.
Previous efforts have used a similar strategy but not found a material with the right properties to use where they use a ceramic separator. This company spent 10 years and ore than $300 million in R&D to come up with it in a guided, but also relentless brute force Edison-style trial and error approach.
Bill Gates, a co-founder of Tesla, and representatives of Volkswagon are investors.
Volkswagen, the world’s largest car manufacturer, which has plowed more than $300 million into QuantumScape and plans to start using the solid-state cells in some of its own EVs as soon as 2025.
Independent parallel efforts to develop solid-state batteries are underway at Toyota, which had planned a reveal at this year's postponed Tokyo Olympics with a 2025 release date planned, but their approach is struggling with a limited lifespan problem that QuantumScape thinks it has overcome.
A six-year-old startup called Solid Power has also made a functioning solid-state cell and begun producing prototype batteries with 10 stacked layers at a pilot plant in Colorado. Like QuantumScape, these cells have a lithium-metal anode and a ceramic solid-state electrolyte. Solid Power’s electrolyte is sulfide-based, a chemistry that is desirable for solid-state batteries because of its high conductivity and compatibility with existing manufacturing processes. The company has partnerships with a number of auto manufacturers, including Ford, BMW, and Hyundai, although its executives don’t expect to see their cells on the road before 2026 because of the lengthy automotive qualification process. Solid Power hasn’t released data on its cell yet, but the company is expected to unveil a larger cell and publish its performance data for the first time this Thursday.“The solid-state battery competitive landscape is becoming increasingly crowded due to the huge potential that solid-state batteries have in enabling vehicle electrification,” says Doug Campbell, Solid Power’s CEO. “This ultimately leads to EVs with greater range, greater reliability, and lower cost.”QuantumScape’s performance data is impressive, but it comes with an important caveat. All of the test data was generated in individual cells that, technically speaking, aren’t complete batteries. The thin cell unveiled by QuantumScape is destined to be stacked together with about 100 others to form a full cell that is about the size of a deck of cards. Powering an EV will require hundreds of those stacked batteries, but so far the company hasn’t tested a fully stacked cell.Scaling a battery from a subunit of a single cell to a full cell and eventually to a full battery pack can create a lot of problems, says Srinivasan. When batteries are made in small batches, he says, it’s easier to eliminate defects that crop up during the production process. But once you start manufacturing batteries at scale, it can be difficult to control defects, which can quickly sap a battery’s performance. “Even though a material may look really promising at the small scale, in the scale-up these defects could become a bigger problem,” says Srinivasan. “Real-world operation is very different from lab-scale operation.”Jeff Sakamoto, a mechanical engineer focused on energy storage at the University of Michigan who was not involved with QuantumScape, agrees. He says there are still significant knowledge gaps about the fundamental mechanical properties of lithium-metal solid-state batteries, which could create problems when it comes to commercializing the technology. . . .
Earlier this year, QuantumScape went public through a special acquisition company and added around $700 million to its already sizable balance sheet. Singh says the company now has more than $1 billion in its war chest, which is more than enough to carry it into production.