Battery prototype: Two sludge-like electrode materials are fed into the device shown here. The anode material flows into the top half, and the cathode flows into the bottom. Lithium ions pass from one material to the other, and electrons flow through the black and red leads.
Credit: Yet-Ming Chiang
MIT Technology Review – A big problem with the lithium-ion batteries used in electric vehicles and plug-in hybrids is that only about 25 percent of the battery’s volume is taken up by materials that store energy. The rest is made up of inactive materials, such as packaging, conductive foils, and glues, which make the batteries bulky and account for a significant part of the cost.
24M intends to greatly reduce the inactive material in a battery. According to estimates in the new paper, its batteries could achieve almost twice the energy densities of today’s vehicle battery packs. Batteries with a higher energy density would be smaller and cheaper, which means electric and hybrid cars would be less expensive. The paper estimates that the batteries could cost as little as $250 per kilowatt hour—less than half what they cost now.
A conventional battery pack is made up of hundreds of cells. Each cell contains a stack of many thin, solid electrodes. These electrodes are paired with metal foil current collectors and separated from each other by plastic films. Increasing the energy storagerequires adding more layers of electrode material—which in turn requires more layers of metal foil and plastic film.
24M’s design makes it possible to increase energy storage without the extra metal foil and plastic film. The key difference is that the electrodes are not solid films stacked in a cell, but sludge-like materials stored in tanks—one for the positive electrode material and another for the negative electrode.