A Boost for Battery Life and Capacity

Electric cars could benefit from a new manufacturing method.

A new chemical trick for making nanostructured materials could help increase the range and reliability of electric cars and lead to better batteries that could help stabilize the power grid.

Serving energy: When lithium-manganese phosphate is grown using a new process, it forms microscopic plates (shown here). These plates conduct both electrons and lithium ions, turning it into a useful material for storing electricity. Credit: Daiwon Choi / PNNL

Researchers at the Pacific Northwest National Laboratory (PNNL) in Richland, WA, have developed the technique, which can turn a potential electrode material that cannot normally store electricity into one that stores more energy than similar battery materials already on the market.

In work published in the journal Nano Letters, the PNNL researchers show that paraffin wax and oleic acid encourages the growth of platelike nanostructures of lithium-manganese phosphate. These "nanoplates" are small and thin, allowing electrons and ions (atoms or molecules with a positive or negative charge) to move in and out of them easily. This turns the material--which ordinarily doesn't work as a battery material because of its very poor conductivity--into one that stores large amounts of electricity.

When the researchers measured the performance of the material, they discovered that it could store 10 percent more energy than the theoretical maximum energy capacity of a comparable commercial electrode material--lithium-iron phosphate, which is used in power tools and some hybrid and electric vehicles.

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The approach could open the door to using a wide range of candidate battery materials that are now limited by their ability to conduct electricity and lithium ions. Research in the area has reached the point at which most of the battery materials left to be studied have bad conductivity, says Daiwon Choi, an energy materials researcher at PNNL. The new method provides a simple way to increase their conductivity. He says the method could also be compatible with conventional battery-manufacturing techniques.

Both lithium-iron phosphate and lithium-manganese phosphate are attractive at battery electrodes because they have a stable atomic structure. This crystalline structure--called olivine--is far more stable than the crystal structure of electrode materials used in laptop and cell-phone batteries. As a result, olivine materials can last much longer than the three years that cell-phone battery materials typically last. Some manufacturers claim that lithium-iron phosphate batteries could last for over 30,000 complete charge and discharge cycles without losing much of their capacity to store energy--enough for the battery to last 50 years, Choi says.