It took more than seven years for automakers to sell 4 million passenger electric vehicles. It'll take about six months to sell the next million.

That surging demand is transforming the lithium-ion battery business, with more power packs expected to be installed in EVs this year than in consumer electronics, according to Bloomberg NEF. China, where subsidy-toting drivers own a third of the world's passenger EVs, is doing the most to fuel the boom.

The market value of batteries used in electric cars, electric buses and related energy storage should multiply by about 10 times to a potential $500 billion by 2050, according to Sanford C. Bernstein & Co. research. Many of the biggest battery producers aren't benefiting now because they're spending billions of dollars to add manufacturing capacity and form global partnerships with automakers. Down the line, though, the trend changes.