Self-Assembling Batteries

Yet-Ming Chiang, a professor of materials science at MIT, and his colleagues have designed a rechargeable Li-ion battery that assembles itself out of microscopic materials. Self-assembly could reduce manufacturing costs and allow molecular-level control of the structure of the batteries, leading to materials and devices difficult to make using conventional manufacturing methods. This also could lead to ultra-small power sources for sensors, micro-machines the size of a head of a pin, and battery materials packed in unused space inside electronic devices. Chiang and his colleagues selected electrode and electrolyte materials that, when combined, organize themselves into the structure of a working battery. After measuring forces between materials using ultra-precise atomic-force microscope probes, materials were selected with the right combination of attractive and repulsive forces. At a couple dozen nanometers, the two electrode materials had surface repulsive forces greater than their attractive forces. As a result, there is always a space left between the electrodes. The lithium cobalt oxide and microbeads of graphite – materials commonly used in lithium-ion batteries – were paired with a carefully selected liquid electrolyte. The electrolyte serves as an insulator, allowing ions to shuttle between the electrodes but forcing electrons to move through an external circuit, where they can be used to power a device.