Batteries are everywhere. They’re in our phones, our airplanes, our gasoline-powered cars, even—in the case of people with pacemakers or other implanted medical devices—our bodies.
The batteries that are really going to matter in the future, though, aren’t the ones that will help you play Angry Birds on your phone for 12 straight hours or start your vehicle on a frigid winter’s morning. The batteries with the potential to transform the world’s energy outlook will power electric vehicles and provide storage for the power grid.
“If you could wave a magic wand and solve the world’s energy problems, you’d only need to change one thing: batteries,” says Ralph Eads, vice chairman of the investment banking firm Jeffries LLC, which invests in new energy technologies.
The problem with energy is not that we don’t have enough of it; new technologies like horizontal drilling and hydraulic fracturing, or “fracking,” have recently unlocked quantities of fossil fuels unimaginable only a decade ago. The problem is that our reliance on those fossil fuels for the majority of our energy is gravely unhealthful, causing millions of premature deaths annually and altering the climate in ways both drastic and unpredictable.
But fossil fuels aren’t a popular source of energy just because they’re so abundant. They’re popular because they can store a lot of energy in a small amount of space. Batteries also store energy, but in a pound-for-pound comparison, they just can’t compete. The easiest place to demonstrate this difference is in a car:
The battery in the hybrid Toyota Prius has around 225 watt-hours of energy per pound. That’s the car battery’s energy density--the amount of energy that can be stored per unit of volume or weight. The gasoline in that Prius contains 6,000 watt-hours per pound. The energy-density difference between liquid petroleum fuels and even the most advanced batteries creates a scenario in which a 7,200-pound Chevrolet Suburban can go 650 miles on a tank of gas and an all-electric Nissan Leaf, which weighs less than half as much, has a a range of only about 100 miles.
And even though around 80 percent of Americans’ automobile trips go fewer than 40 miles, consumer research has shown that drivers suffer from “range anxiety.” They want cars that are able to go on long road trips as well as commute to work and do errands around town.
Energy density has remained the bête noire of batteries for 100 years. Whenever a new technology or design comes along that increases energy density, another crucial aspect of the battery’s performance—say, stability at high temperature, or the number of times it can be drained and recharged—suffers. And when one of those aspects is improved, energy density suffers.
Lithium-iron phosphate technology is a good example. These batteries, from Chinese maker BYD, are widely used in both electric and hybrid vehicles in southern China. They charge more quickly than the lithium-ion batteries that are common in other electric vehicles, such as the Leaf, but they’re less energy-dense.
Another highly valued aspect in battery design is how many times batteries can be charged and drained without losing their ability to store energy. Nickel-metal hydride, or NiMH, batteries, which have been the workhorse for hybrid vehicles including the Prius and Ford’s Escape hybrid for more than a decade, do well in this category. Ted J. Miller, who works on advanced battery technology for Ford Motor Company, says that Ford has pulled the batteries out of Escape hybrids in use for 260,000 miles of taxi service in San Francisco and found they still have 85 percent of their original power capability. That durability is an advantage, but for purely electric vehicles, NiMH batteries are much heavier for the same amount of energy stored by a lithium-ion battery; the extra weight lowers the vehicle’s range. NiMH batteries are also toxic—so no chucking them in the trash bin when they run out of juice—they have to be recycled. And because nickel may be more scarce in the future than lithium, these batteries could get more expensive.