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In a matter of decades, lithium has transformed the world of convenience, giving us practical-size mobile electronics and introducing the possibility of affordable electric vehicles in just a few years. All of this has happened with just a sprinkling of the metal in batteries, because lithium's pure, concentrated version is extraordinarily volatile, causes shorts and often catches fire.

For about a year, though, people working on batteries and EVs have been tantalized by reported breakthroughs in the pursuit of electrodes made of pure lithium-metal—batteries containing not the usual dash of it, but a veritable dollop. Last week, SES, a General Motors-backed startup, pushed hopes further, exhibiting what it called the first lithium-metal cell scaled up to a size required to power an EV. SES said it aimed to have a finished version powering the electric GMC Hummer by the middle of this decade.

SES’s reveal coincides with a moment of truth for the handful of companies attempting to commercialize lithium-metal batteries, and for automakers backing them financially in hopes of more affordable, longer-range EVs. Already, the steep challenge of readying lithium metal for EVs has exposed important limits to what performance can probably be achieved from such electrodes this decade. And it has forced at least one startup out of the race, at least for now (scroll down for details).