Stanford researchers have invented a transparent lithium-ion battery that is also highly flexible. It is comparable in cost to regular batteries on the market today, with great potential for applications in consumer electronics.
Transparent devices have recently attracted substantial attention. Various applications have been demonstrated, including displays, touch screens, and solar cells; however, transparent batteries, a key component in fully integrated transparent devices, have not yet been reported. As battery electrode materials are not transpar- ent and have to be thick enough to store energy, the traditional approach of using thin films for transparent devices is not suitable. Here we demonstrate a grid-structured electrode to solve this dilemma, which is fabricated by a microfluidics-assisted method. The feature dimension in the electrode is below the resolution limit of human eyes, and, thus, the electrode appears transparent. More- over, by aligning multiple electrodes together, the amount of en- ergy stored increases readily without sacrificing the transparency. This results in a battery with energy density of 10 Wh∕L at a trans- parency of 60%. The device is also flexible, further broadening their potential applications. The transparent device configuration also allows in situ Raman study of fundamental electrochemical reactions in batteries.