lunes, 26 de marzo de 2012

Nanopower: Avoiding Electrolyte Failure in Nanoscale Lithum Batteries

Researchers from the National Institute of Standards and Technology (NIST), the University of Maryland, College Park, and Sandia National Laboratories built a series of nanowire batteries to demonstrate that the thickness of the electrolyte layer can dramatically affect the performance of the battery, effectively setting a lower limit to the size of the tiny power sources. The results are important because battery size and performance are key to the development of autonomous MEMS -- microelectromechanical machines -- which have potentially revolutionary applications in a wide range of fields.

NIST researcher Alec Talin and his colleagues created a veritable forest of tiny -- about 7 micrometers tall and 800 nanometers wide -- solid-state lithium ion batteries to see just how small they could be made with existing materials and to test their performance.
Starting with silicon nanowires, the researchers deposited layers of metal (for a contact), cathode material, electrolyte, and anode materials with various thicknesses to form the miniature batteries. They used a transmission electron microscope (TEM) to observe the flow of current throughout the batteries and watch the materials inside them change as they charged and discharged.
The team found that when the thickness of the electrolyte film falls below a threshold of about 200 nanometers, the electrons can jump the electrolyte border instead of flowing through the wire to the device and on to the cathode. Electrons taking the short way through the electrolyte cause the electrolyte to break down and the battery to quickly discharge.

Dmitry Ruzmetov, Vladimir P. Oleshko, Paul M. Haney, Henri J. Lezec, Khim Karki, Kamal H. Baloch, Amit K. Agrawal, Albert V. Davydov, Sergiy Krylyuk, Yang Liu, JianY. Huang, Mihaela Tanase, John Cumings, A. Alec Talin. Electrolyte Stability Determines Scaling Limits for Solid-State 3D Li Ion Batteries. Nano Letters, 2012; 12 (1): 505 DOI: 10.1021/nl204047z

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