Evidence of the battery-powered era is all around us. Electric vehicles are cruising down our freeways. Household appliances thrum with stored solar energy that was until recently a daytime-only power source. Governments from California to China and South Korea—even Donald Trump’s Washington—have taken steps that will make battery power more ubiquitous.

There’s just one hitch to this battery boom: The world isn’t making nearly enough. All of the new demand from North America, Europe, and Asia is constrained at the moment by a market that remains heavily dependent on a few producers.

Data on the global supply of batteries is...