Experimental batteries based on an unusual form of iron deliver 50% more energy than regular batteries and decompose to nothing more threatening than rust, researchers in Israel reported Friday.
The researchers also developed a modified version of the cell that is 75% rechargeable. Experts hailed the discoveries as intriguing but remain uncertain about the practical applications.
Batteries now on the shelves always run out of one of three important components while they still have plenty of the other two. Researchers at the Technion Israel Institute of Technology solved that problem by using a different material for that one limiting component.
Batteries provide convenience and mobility, powering everything from flashlights and stereos to hearing aids and talking toys. Consumers in the United States used 4 billion batteries last year, according to statistics from the makers of the Energizer battery. This translates to about $1.3 billion in non-rechargeable batteries in this country.
With such a large market, the drive to develop new battery technologies is strong, and has resulted in such advances as batteries that can be reused. But non-rechargeable batteries still power the bulk of consumer electronics and, surprisingly, the dominant battery type (the alkaline battery) relies on the same chemistry that has been used for more than a century.
The secret of the new battery's extra power, reported in Friday's issue of the journal Science, is a new chemistry.
A battery's three components are the anode, the cathode and the electrolyte, which allows current to flow between the anode and cathode. Electrons build up on the anode; when the battery is installed in a device, those electrons flow through the device to the cathode, powering the device. As this happens, the material at the anode changes to a form that cannot give up more electrons, and the material at the cathode changes to a form that cannot take any more electrons. Typically, the cathode is exhausted long before the anode or electrolyte.
Whereas traditional cathodes contain a chemical called manganese dioxide, the new batteries rely on what head researcher Stuart Licht dubbed a "super iron" because of its enhanced ability to store a charge and provide more juice.
Another advantage, Licht said, is that a spent super-iron battery contains relatively harmless materials. As the battery is used, the super-iron is processed into a form of ferric oxide: rust. For traditional batteries, the manganese dioxide turns into a somewhat poisonous chemical called manganese sesquioxide, though the material is trapped within the battery shell.
