{"54920":{"#nid":"54920","#data":{"type":"news","title":"Self-Assembled Nanocomposites Boost Lithium-Ion Battery Anodes","body":[{"value":"\u003Cp\u003EA new high-performance anode structure based on silicon-carbon nanocomposite materials could significantly improve the performance of lithium-ion batteries used in a wide range of applications from hybrid vehicles to portable electronics. \u003C\/p\u003E\u003Cp\u003EProduced with a \u0022bottom-up\u0022 self-assembly technique, the new structure takes advantage of nanotechnology to fine-tune its materials properties, addressing the shortcomings of earlier silicon-based battery anodes. The simple, low-cost fabrication technique was designed to be easily scaled up and compatible with existing battery manufacturing. \u003C\/p\u003E\u003Cp\u003EDetails of the new self-assembly approach were published online in the journal \u003Cem\u003ENature Materials \u003C\/em\u003Eon March 14. \u003C\/p\u003E\u003Cp\u003E\u0022Development of a novel approach to producing hierarchical anode or cathode particles with controlled properties opens the door to many new directions for lithium-ion battery technology,\u0022 said Gleb Yushin, an assistant professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. \u0022This is a significant step toward commercial production of silicon-based anode materials for lithium-ion batteries.\u0022 \u003C\/p\u003E\u003Cp\u003EThe popular and lightweight batteries work by transferring lithium ions between two electrodes -- a cathode and an anode -- through a liquid electrolyte. The more efficiently the lithium ions can enter the two electrodes during charge and discharge cycles, the larger the battery\u0027s capacity will be. \u003C\/p\u003E\u003Cp\u003EExisting lithium-ion batteries rely on anodes made from graphite, a form of carbon. Silicon-based anodes theoretically offer as much as a ten-fold capacity improvement over graphite, but silicon-based anodes have so far not been stable enough for practical use. \u003C\/p\u003E\u003Cp\u003EGraphite anodes use particles ranging in size from 15 to 20 microns. If silicon particles of that size are simply substituted for the graphite, expansion and contraction as the lithium ions enter and leave the silicon creates cracks that quickly cause the anode to fail. \u003C\/p\u003E\u003Cp\u003EThe new nanocomposite material solves that degradation problem, potentially allowing battery designers to tap the capacity advantages of silicon. That could facilitate higher power output from a given battery size -- or allow a smaller battery to produce a required amount of power. \u003C\/p\u003E\u003Cp\u003E\u0022At the nanoscale, we can tune materials properties with much better precision than we can at traditional size scales,\u0022 said Yushin. \u0022This is an example of where having nanoscale fabrication techniques leads to better materials.\u0022 \u003C\/p\u003E\u003Cp\u003EElectrical measurements of the new composite anodes in small coin cells showed they had a capacity more than five times greater than the theoretical capacity of graphite. \u003C\/p\u003E\u003Cp\u003EFabrication of the composite anode begins with formation of highly conductive branching structures -- similar to the branches of a tree -- made from carbon black nanoparticles annealed in a high-temperature tube furnace. Silicon nanospheres with diameters of less than 30 nanometers are then formed within the carbon structures using a chemical vapor deposition process. The silicon-carbon composite structures resemble \u0022apples hanging on a tree.\u0022 \u003C\/p\u003E\u003Cp\u003EUsing graphitic carbon as an electrically-conductive binder, the silicon-carbon composites are then self-assembled into rigid spheres that have open, interconnected internal pore channels. The spheres, formed in sizes ranging from 10 to 30 microns, are used to form battery anodes. The relatively large composite powder size -- a thousand times larger than individual silicon nanoparticles -- allows easy powder processing for anode fabrication. \u003C\/p\u003E\u003Cp\u003EThe internal channels in the silicon-carbon spheres serve two purposes. They admit liquid electrolyte to allow rapid entry of lithium ions for quick battery charging, and they provide space to accommodate expansion and contraction of the silicon without cracking the anode. The internal channels and nanometer-scale particles also provide short lithium diffusion paths into the anode, boosting battery power characteristics. \u003C\/p\u003E\u003Cp\u003EThe size of the silicon particles is controlled by the duration of the chemical vapor deposition process and the pressure applied to the deposition system. The size of the carbon nanostructure branches and the size of the silicon spheres determine the pore size in the composite. \u003C\/p\u003E\u003Cp\u003EProduction of the silicon-carbon composites could be scaled up as a continuous process amenable to ultra high-volume powder manufacturing, Yushin said. Because the final composite spheres are relatively large when they are fabricated into anodes, the self-assembly technique avoids the potential health risks of handling nanoscale powders, he added. \u003C\/p\u003E\u003Cp\u003EOnce fabricated, the nanocomposite anodes would be used in batteries just like conventional graphite structures. That would allow battery manufacturers to adopt the new anode material without making dramatic changes in production processes. \u003C\/p\u003E\u003Cp\u003ESo far, the researchers have tested the new anode through more than a hundred charge-discharge cycles. Yushin believes the material would remain stable for thousands of cycles because no degradation mechanisms have become apparent. \u003C\/p\u003E\u003Cp\u003E\u0022If this technology can offer a lower cost on a capacity basis, or lighter weight compared to current techniques, this will help advance the market for lithium batteries,\u0022 he said. \u0022If we are able to produce less expensive batteries that last for a long time, this could also facilitate the adoption of many \u0027green\u0027 technologies, such as electric vehicles or solar cells.\u0022 \u003C\/p\u003E\u003Cp\u003EIn addition to Yushin, the paper\u0027s authors included Alexandre Magasinki, Patrick Dixon and Benjamin Hertzberg -- all from Georgia Tech -- and Alexander Kvit from the Materials Science Center and Materials Science Department at the University of Wisconsin-Madison, and Jorge Ayala from Superior Graphite. The paper also acknowledges the contributions of Alexander Alexeev at Georgia Tech and Igor Luzinov from Clemson University. \u003C\/p\u003E\u003Cp\u003EThe research was partially supported by a Small Business Innovation Research (SBIR) grant from the National Aeronautics and Space Administration (NASA) to Chicago-based Superior Graphite and Atlanta-based Streamline Nanotechnologies, Inc. \u003C\/p\u003E\u003Cp\u003E\u003Cem\u003E\u003Cstrong\u003EThis research was partially supported by the National Aeronautics and Space Administration (NASA) through SBIR grant NNX09CD29P 2008-1. The statements and opinions expressed in the article are those of the researcher and do not necessarily represent the official position of NASA.\u003C\/strong\u003E\u003C\/em\u003E \u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003EGeorgia Institute of Technology\u003Cbr \/\u003E75 Fifth Street, N.W., Suite 314\u003Cbr \/\u003EAtlanta, Georgia 30308 USA\u003C\/strong\u003E \u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Abby Vogel (404-385-3364)(\u003Ca href=\u0022mailto:avogel@gatech.edu\u0022\u003Eavogel@gatech.edu\u003C\/a\u003E). \u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon \u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA new high-performance anode structure based on silicon-carbon nanocomposite materials could significantly improve the performance of lithium-ion batteries used in a wide range of applications from hybrid vehicles to portable electronics.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"High-capacity anode could boost lithium-ion battery performance"}],"uid":"27303","created_gmt":"2010-03-15 00:00:00","changed_gmt":"2016-10-08 03:04:08","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2010-03-15T00:00:00-04:00","iso_date":"2010-03-15T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"54921":{"id":"54921","type":"image","title":"Schematic of nanocomposite","body":null,"created":"1449175379","gmt_created":"2015-12-03 20:42:59","changed":"1475894455","gmt_changed":"2016-10-08 02:40:55"},"54922":{"id":"54922","type":"image","title":"Nanocomposite microscope image","body":null,"created":"1449175408","gmt_created":"2015-12-03 20:43:28","changed":"1475894463","gmt_changed":"2016-10-08 02:41:03"}},"media_ids":["54921","54922"],"related_links":[{"url":"http:\/\/www.mse.gatech.edu\/","title":"Georgia Tech School of Materials Science and Engineering"},{"url":"http:\/\/www.mse.gatech.edu\/FacultyStaff\/MSE_Faculty_researchbios\/Yushin\/yushin.html","title":"Gleb Yushin"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"144","name":"Energy"},{"id":"145","name":"Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"}],"keywords":[{"id":"1292","name":"battery"},{"id":"8948","name":"lithium-ion"},{"id":"1692","name":"materials"},{"id":"7563","name":"nanocomposite"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}