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12-03 :: March/April 2012
nanotimes News in Brief Batteries //
Avoiding Electrolyte Failure in Nanoscale Lithum Batteries © Based on Material by NIST, USA
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Using a TEM, NIST researchers were able to watch individual nanosized batteries with electrolytes of different thicknesses charge and discharge. The NIST team discovered that there is likely a lower limit to how thin an electrolyte layer can be made before it causes the battery to malfunction. © Talin/NIST
N
IST researcher Alec Talin and his colleagues created a veritable forest of tiny – about 7µm
tall and 800nm wide – solid-state lithium ion batte- ries. Starting with silicon nanowires, the researchers deposited layers of metal (for a contact), cathode ma- terial, 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 batte- ries 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 200nm, 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 – a short circuit –cause the electrolyte to break down and the battery to quickly discharge.
“What isn’t clear is exactly why the electrolyte breaks down,” says researcher Talin. “But what is clear is that we need to develop a new electrolyte if we are going to construct smaller batteries. The predominant material, LiPON, just won’t work at the thicknesses necessary to make practical high-energy-density rechargeable batteries for autonomous MEMS.”
D. Ruzmetov, V.P. Oleshko, P.M. Haney, H.J. Lezec, K. Karki, K.H. Baloch, A.K. Agrawal, A.V. Davydov, S. Kryly- uk, Y. Liu, J. Huang, M. Tanase, J. Cumings and A.A. Talin: Electrolyte stability determines scaling limits for solid-state 3D Li-ion batteries, In: NANO Letters, Vol. 12, Issue 1, January 11, 2012, Pages 505-511, DOI:10.1021/ nl204047z: