It’s hard to write about battery research around these parts without hearing certain comments echo before they’re even posted: It’ll never see the market. Cold fusion is eternally 20 years away, and new battery technology is eternally five years away.

That skepticism is understandable when a new battery design promises a revolution, but it risks missing the fact that batteries have gotten better. Lithium-ion batteries have reigned for a while now—that’s true. But “lithium-ion” is a category of batteries that includes a wide variety of technologies, both in terms of batteries in service today and the ones we've used previously. A lot can be done—and a lot has been done—to make a better lithium-ion battery. In fact, gains in the amount of energy they can store have been on the order of five percent per year. That means that the capacity of your current batteries is over 1.5 times what they would have held a decade ago. //

Energy density has a prominent trend. The original commercial lithium-ion battery, produced by Sony in the early 1990s, had an energy density of under 100 watt-hours per kilogram. That number has climbed over time, with the familiar cylindrical 18650 cells on the market hitting 200 watt-hours per kilogram by 2010. According to BloombergNEF, batteries used in electric vehicles have gotten as high as 300 watt-hours per kilogram in the last couple of years. //

The cost of lithium-ion batteries has fallen dramatically—with huge effects on electric vehicles. A recent study noted that “the real price of lithium-ion cells, scaled by their energy capacity, has declined by about 97 percent since their commercial introduction in 1991.” The early lithium-ion cells in the 1990s were around $3,000 per kilowatt-hour. By the early 2000s, that was nearer to $500 per kilowatt-hour.

In terms of electric vehicles, BloombergNEF estimates that the average price of a complete battery pack was about $1,180 per kilowatt-hour in 2010. By 2020, it was down to around $130 per kilowatt-hour. Ultimately, this is what makes it possible to produce a car with 300-mile range that someone not named “Jeff Bezos” can plausibly afford.