After Decades of Explosions, Battery Startups Give the Green Light to Liquid and Lithium-Metal

This article orignally appeared in The Mobilist.

Steve LeVine – Forecasts of a revolution in batteries — ushering in much cheaper electric vehicles with far greater range — have rested largely on the promise of a coming technological breakthrough: an electrode made of pure lithium metal, delivering much more energy than current lithium-ion. The prognostications have even foreshadowed what that leap would look like: Since lithium is exceedingly reactive and can explode when in contact with liquid, the much-sought battery would feature a “solid-state” separator that allows ions to shuttle quickly while preventing the two electrodes from shorting out.

But two big announcements this week suggest that the decadeslong quest for a magical solid-state battery material may have been unnecessary. A liquid electrolyte, both suggested, works just fine with lithium metal.

What makes lithium-metal seductive to battery-makers is the energy it produces while weighing relatively little. Lithium-metal can pack in about 50% more energy than lithium-ion in the same space, allowing automakers to charge much less for electric vehicles (EVs) than they currently do.

Work on such batteries began in the 1970s but with disastrous results. Researchers favored liquid as the electrolyte — the part of the battery lying between the two electrodes — because ions move quickly through it. In an EV, fast-moving ions equate to rapid acceleration. In addition, virtually all current EV battery systems use a liquid electrolyte so that a lithium-metal battery using liquid can be manufactured using the same factory equipment. But the explosions created a mindset that, if you were thinking lithium-metal, you had to exclude liquid, and today’s best-known lithium-metal companies — such as QuantumScape and Solid Power — use solid separators.

But in an interview yesterday on Washington Post Live, GM president Mark Reuss said that the Detroit giant would build a pilot manufacturing plant with SES, a Massachusetts-based developer of a liquid-based lithium-metal battery. Reuss said the plant, to be finished by 2023, will manufacture battery prototypes.

That would coincide with GM’s plans to deploy 30 EV models by 2025 and go completely electric by 2035. Toward its sales goals, GM seeks to halve the cost of its batteries and double their energy density by the middle of the decade.

GM has released little data validating its futuristic battery work, and while saying it has received 49 patents for lithium metal discoveries, it has not clearly described where SES’s IP ends and its begins. SES did not respond to requests for comment. But in an interview last November, GM described the shape of a system that sounds substantially [like SES’s](https://www.technologyreview.com/2016/08/23/157961/better-lithium-batteries-to-get-a-test-flight/. The battery, using a liquid electrolyte, applies a special protective coating over the anode, thus defending it from explosions. GM said the system was already producing 500 charge-discharge cycles, more than halfway to the minimum required 800 or so.

In the other announcement, Northvolt, a Sweden-based company that’s attempting to create a European battery cell industry from scratch, on Wednesday said it had acquired a Silicon Valley lithium-metal startup called Cuberg. In an interview yesterday, Cuberg CEO Richard Wang told me that his prototypes were currently being tested by several aviation customers. The eventual idea, however, said Northvolt spokesman Jesper Wigardt, is to have Cuberg’s battery ready for EVs by 2025.

Wang said it turns out that the trick with lithium-metal is not whether you are using a liquid or solid electrolyte. It’s about how whatever you do use reacts with the surface of the lithium-metal. In the case of liquid, the aim is “to make really good electrolyte” so that it forms a smooth layer over the anode — what he called an artificial equivalent of a solid-state separator. Wang said that Cuberg will meet the deadline for an EV battery by 2025. “We may still have to drive down the cost,” he said, “but it will be in the market.”