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Thursday, June 11, 2009

IBM Invests in lithium-air battery research



As a good indication of how enormous the future market for EVs will be, IBM has joined the fray and started an R&D project that it hopes will lead to the commercialization of batteries that store 40 times as much energy as today's within the next five years. In partnership with U.S. national labs, they want to develop a new technology that uses energy-dense but highly flammable lithium metal to react with oxygen in the air. The potential payoff will be a lightweight, powerful, and rechargeable battery electric vehicles.

Lithium metal-air batteries can store more than 5,000 watt-hours per kilogram. (A123 M1 cells are around 120 wh/kg) That's more than forty-times as much as today's high-performance lithium-ion batteries, and more than another class of energy-storage devices: fuel cells. The reduction in battery mass is achieved by eliminating the need for a second reactant inside the cell. Lithium metal batteries react with oxygen in the air that is pulled in through a 'breathing' casing, making them lightweight and compact.

lightweight 500-mile range EV battery

IBM is pursuing the risky technology instead of lithium-ion batteries because it has the potential to reach high enough energy densities to vault IBM ahead in the race for EV batteries. IBM say lithium-ion batteries only have enough development potential to double in density. To really make an impact on transportation and on the grid, IBM believe, you need much higher energy density than that. One of the projects stated goals is to build a lightweight battery with 500-mile range for a family car.

One of the main challenges in making lithium metal-air batteries is that air doesn't just contain oxygen alone. Where you have air you also find moisture, and humidity is the death of lithium. Adding further to the challenge, 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.

Battery development is a totally new area of development for IBM which does not currently have battery research programs in place. However, IBM believe they have the expertise needed to tackle the science problems.

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.

Safety problems with lithium-metal batteries can arise when they're recharged. When you charge and discharge, you have to electroplate and strip the metal over and over again. Over time, just as in a lithium-ion battery, the lithium-metal surface becomes rough, which can lead to thermal runaway, when the battery literally burns until all the reactants inside are used up. Lithium-air batteries are inherently safer than previously developed lithium-metal batteries as well as today's lithium-ion batteries because only one of the reactants is contained in the cell. Because a lithium-air cell needs air from outside it can never get a runaway reaction because air is limited.

PolyPlus Battery has been working on lithium metal-air technology for about six years with a theoretical specific energy of 11,600 Wh/kg for Li-Air chemistry (almost 100x A123 cells). Some of the Li-Air engineering is a development of Zinc-Air batteries.

IBM will devote about five years and 50 to 100 people to the project. IBM will probably not make the batteries but will license the technology to manufacturers.

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