Better batteries through chemistry

The cathodes of current lithium-ion batteries are made of lithium-cobalt metal oxide (LiCoO₂). This material is pricey, and it can become unstable and release oxygen if the cell is overcharged. One alternative is to replace the cobalt in the cathodes with iron phosphates, which won’t release oxygen under any charge and therefore will not burn.

A123Systems, in Watertown, Mass., first launched a lithium-ion phosphate battery this past fall in Black & Decker’s DeWalt power tools. A123Systems claims its batteries can be recharged 10 times as often as conventional lithium-ion designs, charge to 90 percent capacity in 5 minutes, and charge fully in less than 15 minutes. Conventional lithium-ion models, by contrast, can take twice as long.

In May, the company unveiled a battery pack it said could be ready for electric vehicle use within three years. It’s smaller than a carton of cigarettes and weighs barely 4.5 kg (10 lbs.), one-fifth as heavy as an equivalent NiMH battery. A123 is taking part in one of the two joint ventures to which GM has awarded battery development contracts. Its partner is Cobasys, of Orion, Michigan, itself a joint venture of Chevron Technology Ventures and Energy Conversion Devices Inc. GM's other contract is with a joint venture between Johnson Controls, of Milwaukee, and Saft Advanced Power Systems, of Paris.

Austin, Texas–based Valence Technology also uses iron-phosphate cathodes for its Saphion battery. The technology is used in the Segway, the self-stabilizing scooter, and in unofficial conversions that aim to increase the range of a Toyota Prius.

Customarily, the anode of a lithium-ion battery is made of graphite, which can store only a limited amount of energy. Researchers at Sandia National Laboratories, in Livermore, Calif., have developed anodes using a composite of graphite and silicon that can quadruple storage capacity.

Late this year, 3M Co., in St. Paul, Minn., will deliver still another kind of anode, based on amorphous silicon, which the company says will store twice the energy of today’s lithium batteries. Other researchers are trying to make anodes of alloys of lithium and two other metals, generally antimony mixed with either copper, manganese, or indium. Such three-metal alloys should also increase storage capacity.

Cells now being developed by Altair Nanotechnologies, based in Reno, Nev., switch the lithium from the cathode to the anode, forming a compound called lithium-titanate spinel (Li₄Ti₅O₁₂). The company says that the cells recharge in 3 minutes and deliver three times as much power as the conventional design, and at a great operating range of temperatures: –30 °C to 249 °C (–22 °F to 480 °F). It also says that its batteries can keep on ticking after 9000 recharging cycles, compared with 1000 for conventional cells. Altair’s battery, however, is not yet in production.

The big gamble

Once lithium batteries have met energy-storage, power-delivery, durability, and cost goals, a massive investment in manufacturing capacity will be needed to produce them in bulk for use in cars. But the market is crowded and competitive; close to a dozen manufacturers have announced new lithium battery technologies—with no guarantees that automakers will buy. And that number omits the in-house battery research that the major automakers themselves are conducting.

Take Toyota, which builds the lion’s share of hybrid vehicles globally. In 2005 it purchased General Motors’ share of Fuji Heavy Industries Ltd. (which manufactures Subarus)—in part, analysts suggest, to get Fuji’s share of its joint venture with Tokyo Electric Power to develop automotive lithium batteries. Subaru has already announced that in 2009 it will build and sell the R1e, an electric version of its tiny R1 urban car that will use lithium-ion batteries. Mitsubishi Motors, in Tokyo, will do much the same with its “i” urban car, most likely using batteries from Litcel, its joint venture with TDK Corp.

Analysts estimate the price premium for today’s hybrids at roughly US $5000, some $3000 of which goes to cover the cost of a NiMH battery pack. At today’s gasoline and electricity prices, you’d need six to 10 years of operation to pay it back. But the analysts also say the hybrid premium could fall to $2000 in five years ($1200 or more of it the cost of lithium-ion batteries), which would allow for a three-year payback.

The payback period could be longer for a plug-in hybrid, because it would have larger, costlier batteries—though fuel mileage is hard to calculate. It all depends on how much of the mileage is covered in electric mode, with power taken from the grid, and how much in gasoline mode.

Powerful forces—global warming, possible carbon taxes, global political instability—seem to be lining up in ways that will bring us electric-drive cars that will be feasible and affordable for the first time ever. They won’t arrive this year, or next year…but they’ll be here sooner than you might think. It all comes down to one question: when will the lithium-ion batteries be ready?