THE IDEA

Swap the liquid for a solid

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Safer

No flammable liquid solvent

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Lithium metal

A solid might stop dendrites and allow a lithium-metal anode

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More energy

Lithium metal could raise energy density substantially

The prize is lithium metal, made safe.

THREE FAMILIES

Which solid electrolyte?

Oxide ceramics, sulfide glasses and crystals, and polymers each have strengths and a serious weakness.

No solid electrolyte is perfect yet.

THE HARD PARTS

Why it isn't in every car yet

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Contact Solids don't flow into gaps like a liquid, so layers lose touch as they swell and shrink

Pressure Many designs need the cell squeezed hard to keep contact

Dendrites Lithium can still push through cracks and grain boundaries

Manufacturing Thin, flawless ceramic or sulfide sheets at scale are hard and costly

The chemistry works in the lab; making millions is the challenge.

ANODE-FREE

Making the anode in place

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In an anode-free cell, the cell is built with just a bare copper foil. On the first charge, lithium from the cathode plates onto the foil to form the anode. That saves weight and avoids handling lithium metal in the factory, but every bit of lithium lost is gone for good.

The lightest anode is no anode at all, until the first charge.

WHERE THINGS STAND

From buses to pilot lines

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Polymer solid-state packs have run in some electric buses and car-sharing cars. Many companies are working on oxide and sulfide cells on pilot lines, with semi-solid cells (a little liquid kept) arriving first in some cars. Claims change fast, so check the latest news.

Solid-state is arriving in steps, not all at once.

UNIT 18 STUDY COMPLETE

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Ready for the Fab Challenge?

You've seen what solid-state batteries promise, the three electrolyte families, and why they are hard to make.