Imagine a smartphone that can be completely charged in mere minutes; lasts longer on that charge than any phone you've ever seen; is made from cleaner materials; and costs less than existing devices, to boot.
This is all possible—but first, the world needs a better way to power that gadget. Rechargeable lithium-ion batteries have served us well, but we can do better. When we find the replacement, it will revolutionize the way we think about energy. But the ideal power source will need to satisfy a host of commercial and industrial uses—everything from electric vehicles and airplanes to phones and cameras—even power grids. Not to mention, it needs to be compact and environmentally friendly. That’s a heavy challenge, indeed.
This is the good news: Researchers around the world are on the hunt to find just such a device, and they have plenty of promising leads. Here's a look at four of the top contenders.
Tin Nanocrystal Lithium-Ion Battery
Lithium-ion is the standard bearer of chargeable battery technology. It’s energy-dense, relatively cheap, and used in everything from tablet computers and cameras to airplanes and power drills. Elemental lithium is also the lightest metal on the periodic table and boasts the greatest electrochemical potential.
The lithium-ion battery generates power by sending lithium ions from a negative electrode to a positive electrode, and does the reverse during a charge. But the electrodes themselves—typically made of cobalt, nickel, manganese, or graphite—are not as absorbent of these ions as many would like them to be. Accordingly, demand has risen for an electrode nanomaterial that will boost the energy-storing capacity of lithium-ion batteries.
Many scientists see tin as the perfect element for the job. Tin crystal, specifically, expands up to three times its normal size when it absorbs lithium ions, and then shrinks again after releasing them—just like a sponge. This doubles the energy capacity of the battery, according to the Laboratory of Inorganic Chemistry at ETH Zurich.
Aside from being an awesome band name, "metal-air" is a nonspecific category of batteries whose metal electrodes react with air instead of liquid. These electrodes may be built from a number of different metals, each of which interacts with oxygen in the air to produce an electrical current. A variety of metals can be used for the electrode, but the most promising ones are lithium and sodium.
Some experts see lithium-air as the Holy Grail of electric car batteries, as it promises to extend the battery life of these vehicles to a whopping 1,000 miles—much higher than the existing average of 125 miles. Right now the technology is unstable, but research and investment are not. IBM, for example, is currently working on a prototype lithium-air battery for Boeing's Dreamliner airplane.
An alternative to lithium-air is sodium-air. It has a lower theoretical energy capacity but is more stable and easier to build—and still more efficient than today's lithium-ion batteries. In fact, tests have shown sodium-air batteries with a higher practical energy storage capacity than lithium-air. So for the time being, this technology is arguably superior to the supposed “Holy Grail,” lithium-air. Researchers have also made strides with aluminum- and zinc-air devices, the latter of which is already on the market and can be found in hearing aids.
Liquid Metal Battery
Imagine: a battery like the T-1000 that can shape-shift into whatever kind of energy source you need. Well that's probably never going to happen, but liquid metal might help make power grids more efficient. Currently, grids aren't capable of storing electricity, so power utilities have to play a sort of guessing game when it comes to supply and demand, which makes for a highly inefficient system. But imagine a grid-scale power cell capable of sequestering energy for on-demand delivery by utilities. That is one of the ideas behind the so-called "smart grid", which relies on IT to anticipate fluctuations in demand—and some experts see liquid-metal as the key ingredient.
Here’s how it works: Two liquid-metal electrodes—one low-density negative and one high-density positive—are separated by a molten-salt electrolyte. The difference in composition between the two liquid metals gives rise to a voltage.
MIT Professor Donald Sadoway, who fathered the concept, told the BBC that such a battery would require 50-100 fewer individual cells than a standard battery cell array, making it commercially practical. Sadoway expects a prototype to be ready in 2014.
Okay, so it isn't actually a battery, but aside from sounding like some kind of doomsday device, the graphene supercapacitor is the most exciting emerging technology in the field of power cells—and could ultimately render batteries obsolete. Unlike batteries, which produce current through an electrochemical reaction, capacitors merely store energy. The challenge so far has been to develop a capacitor that is compact, inexpensive, and more energy-dense than a battery—hence, the term "supercapacitor."
Recent research has pointed to graphene, a sheet of carbon that is just one atom thick. It greatly increases the energy density of capacitors. A recent “accidental” discovery by a student in the Kaner Lab at UCLA showed how graphene can be cheaply manufactured using existing consumer technology. The discovery prompted the creation of a short documentary that went viral and became a finalist in GE’s Focus Forward competition. According to Slate’s Farhad Manjoo, widespread applications of the technology may be less than 10 years away. The Kaner Lab asserts that this discovery may have “changed the world,” which is pretty exciting.
Which One Will Succeed?
We aren't chemists, but if we had to pick one new technology to root for, the graphene supercapacitor looks really, really (super?) exciting. Graphene alone is capturing the imaginations of scientists, researchers, and basement tech gurus, with some speculating that the nanomaterial is the next plastic. Add to the mix a new way of thinking about capacitors and you have a textbook example of revolutionary innovation.
Of course, the history of technology is fraught with instances of “miracle” inventions turning out to be little more than examples of what not to do. In a way, technology is the history of failure. But even the biggest mistakes always seem to be the seed of something greater—like MySpace to Facebook or the PDA to the smartphone. The brightest minds have a way of honing in on what works and removing that which doesn’t.
Perhaps one of the above batteries will be the inspiration for a radically new way of thinking about power. But it seems like the graphene supercapacitor is that insight.