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EETE JUN 2014

A42E_EETIMES2_37x10_87_Layout 1 4/29/14 10:55 AM Battery electrode material mystery is Transformers and Inductors visualized for first time think PICO small! By Paul Buckley ...think... A MIT-led team of researchers has produced the first detailed visualization - down to the level of individual atoms - of exactly how sodium manganese dioxide, a promising low profile from .18" ht. Over 5000 Std. Ultra Miniature Surface Mount (and Plug-In) Models Audio / 400Hz / Pulse Multiplex Data Bus / DC-DC Converter Transformers / Power & EMI Inductors S ee Pi co’s full Catalog immedia te ly ww w. p i c o e l e c t ro n i c s . c o m PICO units manufactured and tested to MIL-PRF-27 requirements. QPL units are available. Delivery stock to one week for sample quantities. PICO Electronics,Inc. 143 Sparks Ave. Pelham, N.Y. 10803 E Mail: info@picoelectronics.com www.picoelectronics.com Pico Representatives Germany ELBV/Electra Bauemente Vertrieb E mail: info@elbv.de Phone: 49 089 460205442 Fax: 49 089 460205442 England Ginsbury Electronics Ltd E-mail: rbennett@ginsbury.co.uk Phone: 44 163 429800 Fax: 44 163 4290904 electrode used in rechargeable batteries, behaves during charging and discharging. The visualization discovery helps to elucidate an exotic molecular state that may help a greater understanding of superconductivity. The findings are reported in the journal Nature Materials, in a paper by MIT researcher Xin Li, professors Young Lee and Gerbrand Ceder, also of MIT, and 12 others. The phenomenon the team investigated - known as the cooperative Jahn-Teller effect - “is a basic piece of physics that has been well-known historically”, explained Ceder, the R.P. Simmons Professor of Materials Science and Engineering. The effect describes how the positions of atoms in certain compounds can be slightly distorted, changing the materials electrical and magnetic properties. It is associated with a lot of interesting phenomena, said Ceder and enables a better understanding that could be useful both in advancing our knowledge of physics and in potential applications, from improved batteries to new kinds of electronics. While the Jahn-Teller phenomenon is well-known, Ceder says it is a bit unusual to see it in battery compounds such as the sodium manganese dioxide now under investigation as a possible lower-cost substitute for the lithium-based electrodes in lithium-ion batteries. Such rechargeable batteries work when an electrical current pulls ions out of an electrode during charging, then returns them to the electrode as the battery is used. The arrangement of atoms within the material is very ordered, and normally the ordering is driven by fairly standard physics, expalined Ceder. But in this material, the order is completely driven by the Jahn-Teller effect. Understanding how that difference affects charging and discharging could be important in guiding teams around the world who are seeking to improve the performance of such batteries. The team combined density functional theory with technologies including electron diffraction; synchrotron X-ray diffraction; neutron diffraction; and aberration-corrected atomic-resolution scanning microscopy for direct visualization. Using these methods, the researchers showed that the material produces a ‘superstructure’ governed by the Jahn-Teller effect; at low temperatures, it produces a kind of ‘magnetic stripe sandwich’, with alternating stripes of ferrimagnetic and antiferromagnetic atomic chains. This is fundamental work, said Li, to determine any intrinsic capacity limits to sodium manganese dioxide - such as how much charge it can hold, or how many times it can go through the charge-discharge cycle without degradation. The ultimate goal is to find out how to make a higher-capacity sodium-ion battery electrode. In addition to possible battery applications, the work led to the finding that sodium manganese dioxide forms bands of magnetic domains at temperatures of 60 kelvins or less. The finding, Li said, may be important to the emerging field of spin electronics, where the spin states of electrons, rather than their electrical charges, carry and store information. www.electronics-eetimes.com Electronic Engineering Times Europe June 2014 51


EETE JUN 2014
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