|
 |
| Waterproof power: This protective casing envelops a functioning lithium-metal battery electrode, excluding water but letting oxygen pass. It's part of a prototype battery made by PolyPlus Battery of Berkeley, CA. Credit: PolyPlus |
IBM Research is beginning an ambitious project that it hopes will lead to the commercialization of batteries that store 10 times as much energy as today's within the next five years. The company will partner with U.S. national labs to develop a promising but controversial technology that uses energy-dense but highly flammable lithium metal to react with oxygen in the air. The payoff, says the company, will be a lightweight, powerful, and rechargeable battery for the electrical grid and the electrification of transportation.
Lithium metal-air batteries can store a tremendous amount of energy--in theory, more than 5,000 watt-hours per kilogram. That's more than ten-times as much as today's high-performance lithium-ion batteries, and more than another class of energy-storage devices: fuel cells. Instead of containing a second reactant inside the cell, these batteries react with oxygen in the air that's pulled in as needed, making them lightweight and compact.
IBM is pursuing the risky technology instead of lithium-ion batteries because it has the potential to reach high enough energy densities to change the transportation system, says Chandrasekhar Narayan, manager of science and technology at IBM's Almaden Research Center, in San Jose, CA. "With all foreseeable developments, lithium-ion batteries are only going to get about two times better than they are today," he says. "To really make an impact on transportation and on the grid, you need higher energy density than that." One of the project's goals, says Narayan, is a lightweight 500-mile battery for a family car. The Chevy Volt can go 40 miles before using the gas tank, and Tesla Motors' Model S line can travel up to 300 miles without a recharge.
One of the main challenges in making lithium metal-air batteries is that "air isn't just oxygen," says Jeff Dahn, a professor of materials science at Dalhousie University, in Nova Scotia. Where there's air there's moisture, and "humidity is the death of lithium," says Dahn. When lithium metal meets water, an explosive reaction ensues. These batteries will require protective membranes that exclude water but let in oxygen, and are stable over time.
IBM does not currently have battery research programs in place. However, Narayan says that IBM has the expertise needed to tackle the science problems. In addition to Oak Ridge, IBM will partner with Lawrence Berkeley, Lawrence Livermore, Argonne, and Pacific Northwest national labs. The company and its collaborators are currently working on a proposal for funding from the U.S. Department of Energy under the Advanced Research Projects Agency-Energy.
Research on lithium-metal batteries stalled about 20 years ago. In 1989, Canadian company Moli Energy recalled its rechargeable lithium-metal batteries, which used not air but a more traditional cathode, after one caught fire; the incident led to legal action, and the company declared bankruptcy. Soon after, Sony brought to market the first rechargeable lithium-ion batteries, which were safer, and research on lithium-metal electrodes slowed nearly to a halt. (After restructuring, Moli Energy refocused its research efforts and is now selling lithium-ion batteries under the name Molicel.) Only a handful of labs around the world, including those at PolyPlus Battery, in Berkeley, CA, Japan's AIST, and St. Andrews University, in Scotland, are currently working on lithium-air batteries.