The improvements we’ve seen in battery technologies are not limited to lower costs. As Ziegler and Trancik show, the energy density of cells has also been increasing. Energy density measures the amount of electrical energy you can store in a liter (or unit) of battery. In 1991 you could only get 200 watt-hours (Wh) of capacity per liter of battery.
Now, MIT researchers have carried out an exhaustive analysis of the studies that have looked at the decline in the prices these batteries, which are the dominant rechargeable technology in today’s world.
The price of lithium-ion battery cells declined by 97% in the last three decades. A battery with a capacity of one kilowatt-hour that cost $7500 in 1991 was just $181 in 2018. That’s 41 times less. What’s promising is that prices are still falling steeply: the cost halved between 2014 and 2018. A halving in only four years.
While it was common knowledge that the decline in battery costs was an enabler of the recent growth in sales of electric vehicles, for example, it was unclear just how great that decline had been.
The new study looks back over three decades, including analyzing the original underlying datasets and documents whenever possible, to arrive at a clear picture of the technology’s trajectory. The researchers found that the cost of these batteries has dropped by 97 percent since they were first commercially introduced in 1991.
The work was supported by the Alfred P. Sloan Foundation. The cost of lithium-ion batteries for phones, laptops, and cars has plunged over the years, and an MIT study shows just how dramatic that drop has been. The change is akin to that of solar and wind energy, and further declines may yet be possible, the researchers say.