{"148411":{"#nid":"148411","#data":{"type":"news","title":"Self-Charging Power Cell Converts and Stores Energy in a Single Unit","body":[{"value":"\u003Cp\u003EResearchers have developed a self-charging power cell that directly converts mechanical energy to chemical energy, storing the power until it is released as electrical current. By eliminating the need to convert mechanical energy to electrical energy for charging a battery, the new hybrid generator-storage cell utilizes mechanical energy more efficiently than systems using separate generators and batteries.\u003C\/p\u003E\u003Cp\u003EAt the heart of the self-charging power cell is a piezoelectric membrane that drives lithium ions from one side of the cell to the other when the membrane is deformed by mechanical stress. The lithium ions driven through the polarized membrane by the piezoelectric potential are directly stored as chemical energy using an electrochemical process.\u003C\/p\u003E\u003Cp\u003EBy harnessing a compressive force, such as a shoe heel hitting the pavement from a person walking, the power cell generates enough current to power a small calculator. A hybrid power cell the size of a conventional coin battery can power small electronic devices \u2013 and could have military applications for soldiers who might one day recharge battery-powered equipment as they walked.\u003C\/p\u003E\u003Cp\u003E\u201cPeople are accustomed to considering electrical generation and storage as two separate operations done in two separate units,\u201d said \u003Ca href=\u0022http:\/\/www.mse.gatech.edu\/faculty-staff\/faculty\/zhong-lin-wang\u0022\u003EZhong Lin Wang\u003C\/a\u003E, a Regents professor in the \u003Ca href=\u0022http:\/\/www.mse.gatech.edu\/\u0022\u003ESchool of Materials Science and Engineering\u003C\/a\u003E at the Georgia Institute of Technology. \u201cWe have put them together in a single hybrid unit to create a self-charging power cell, demonstrating a new technique for charge conversion and storage in one integrated unit.\u201d\u003C\/p\u003E\u003Cp\u003EThe research was reported Aug. 9, 2012 in the journal \u003Cem\u003ENano Letters\u003C\/em\u003E. The research was supported by the Defense Advanced Research Projects Agency (DARPA), the U.S. Air Force, the U.S. Department of Energy, the National Science Foundation, and the Knowledge Innovation Program of the Chinese Academy of Sciences.\u003C\/p\u003E\u003Cp\u003EThe power cell consists of a cathode made from lithium-cobalt oxide (LiCoO\u003Csub\u003E2\u003C\/sub\u003E) and an anode consisting of titanium dioxide (TiO\u003Csub\u003E2\u003C\/sub\u003E) nanotubes grown atop a titanium film. The two electrodes are separated by a membrane made from poly(vinylidene fluoride) (PVDF) film, which generates a piezoelectric charge when placed under strain. When the power cell is mechanically compressed, the PVDF film generates a piezoelectric potential that serves as a charge pump to drive the lithium ions from the cathode side to the anode side. The energy is then stored in the anode as lithium-titanium oxide.\u003C\/p\u003E\u003Cp\u003ECharging occurs in cycles with the compression of the power cell creating a piezopotential that drives the migration of lithium ions until a point at which the chemical equilibrium of the two electrodes are re-established and the distribution of lithium ions can balance the piezoelectric fields in the PVDF film. When the force applied to the power cell is released, the piezoelectric field in the PVDF disappears, and the lithium ions are kept at the anode through a chemical process.\u003C\/p\u003E\u003Cp\u003EThe charging cycle is completed through an electrochemical process that oxidizes a small amount of lithium-cobalt oxide at the cathode to Li\u003Csub\u003E1-x\u003C\/sub\u003ECoO\u003Csub\u003E2\u003C\/sub\u003E and reduces a small amount of titanium dioxide to Li\u003Csub\u003Ex\u003C\/sub\u003ETiO\u003Csub\u003E2\u003C\/sub\u003E at the anode. Compressing the power cell again repeats the cycle. When an electrical load is connected between the anode and cathode, electrons flow to the load, and the lithium ions within the cell flow back from the anode side to the cathode side.\u003C\/p\u003E\u003Cp\u003EUsing a mechanical compressive force with a frequency of 2.3 Hertz, the researchers increased the voltage in the power cell from 327 to 395 millivolts in just four minutes. The device was then discharged back to its original voltage with a current of one milliamp for about two minutes. The researchers estimated the stored electric capacity of the power cell to be approximately 0.036 milliamp-hours.\u003C\/p\u003E\u003Cp\u003ESo far, Wang and his research team \u2013 which included Xinyu Xue, Sihong Wang, Wenxi Guo and Yan Zhang \u2013 have built and tested more than 500 of the power cells. Wang estimates that the generator-storage cell will be as much as five times more efficient at converting mechanical energy to chemical energy for as a two-cell generator-storage system.\u003C\/p\u003E\u003Cp\u003EMuch of the mechanical energy applied to the cells is now consumed in deforming the stainless steel case the researchers are using to house their power cell. Wang believes the power storage could be boosted by using an improved case.\u003C\/p\u003E\u003Cp\u003E\u201cWhen we improve the packaging materials, we anticipate improving the overall efficiency,\u201d he said. \u201cThe amount of energy actually going into the cell is relatively small at this stage because so much of it is consumed by the shell.\u201d\u003C\/p\u003E\u003Cp\u003EBeyond the efficiencies that come from directly converting mechanical energy to chemical energy, the power cell could also reduce weight and space required by separate generators and batteries. The mechanical energy could come from walking, the tires of a vehicle hitting the pavement, or by harnessing ocean waves or mechanical vibrations.\u003C\/p\u003E\u003Cp\u003E\u201cOne day we could have a power package ready to use that takes advantage of this hybrid approach,\u201d Wang said. \u201cAlmost anything that involves mechanical action could provide the strain needed for charging. People walking could be generating electricity as they move.\u201d\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by DARPA (HR0011-09-C-0142); the U.S. Air Force, the U.S. Department of Energy, Office of Basic Energy Sciences (DE-FG02-07ER46394), the National Science Foundation (CMMI-0403671), and the Knowledge Innovation Program of the Chinese Academy of Sciences (KJCX2-YW-M13). The content is solely the responsibility of the authors and does not necessarily represent the official views of DARPA, the U.S. Air Force, the Department of Energy or the National Science Foundation.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECitation\u003C\/strong\u003E: Xinyu Xue, Sihong Wang, Wenxi Guo, Yan Zhang and Zhong Lin Wang, \u003Cem\u003EHybridizing Energy Conversion and Storage in a Mechanical-to-Electrochemical Process for Self-Charging Power Cell\u003C\/em\u003E, Nano Letters. DOI: 10.1021\/nl302879t\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E75 Fifth Street, N.W., Suite 309\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia\u0026nbsp; 30308\u0026nbsp; USA\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@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\u003EResearchers have developed a self-charging power cell that directly converts mechanical energy to chemical energy, storing the power until it is released as electrical current. The development avoids converting mechanical energy to electrical energy for charging a battery.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers have developed a self-charging power cell that directly converts mechanical energy to chemical energy."}],"uid":"27303","created_gmt":"2012-08-21 16:34:14","changed_gmt":"2016-10-08 03:12:43","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2012-08-21T00:00:00-04:00","iso_date":"2012-08-21T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"148341":{"id":"148341","type":"image","title":"Self-Charging Power Cell","body":null,"created":"1449178763","gmt_created":"2015-12-03 21:39:23","changed":"1475894782","gmt_changed":"2016-10-08 02:46:22","alt":"Self-Charging Power Cell","file":{"fid":"195132","name":"self-charging60.jpg","image_path":"\/sites\/default\/files\/images\/self-charging60_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/self-charging60_0.jpg","mime":"image\/jpeg","size":870717,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/self-charging60_0.jpg?itok=6-MFNEQT"}},"148371":{"id":"148371","type":"image","title":"Self-Charging Power Cell3","body":null,"created":"1449178763","gmt_created":"2015-12-03 21:39:23","changed":"1475894782","gmt_changed":"2016-10-08 02:46:22","alt":"Self-Charging Power Cell3","file":{"fid":"195134","name":"self-charging157.jpg","image_path":"\/sites\/default\/files\/images\/self-charging157_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/self-charging157_0.jpg","mime":"image\/jpeg","size":1282836,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/self-charging157_0.jpg?itok=SGbpB1Bm"}},"148361":{"id":"148361","type":"image","title":"Self-Charging Power Cell2","body":null,"created":"1449178763","gmt_created":"2015-12-03 21:39:23","changed":"1475894782","gmt_changed":"2016-10-08 02:46:22","alt":"Self-Charging Power Cell2","file":{"fid":"195133","name":"self-charging93.jpg","image_path":"\/sites\/default\/files\/images\/self-charging93_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/self-charging93_0.jpg","mime":"image\/jpeg","size":805202,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/self-charging93_0.jpg?itok=t0qJZveU"}}},"media_ids":["148341","148371","148361"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"135","name":"Research"}],"keywords":[{"id":"41281","name":"charging"},{"id":"7699","name":"piezoelectric"},{"id":"41271","name":"power cell"},{"id":"167735","name":"School of Materials Science \u0026 Engineering"},{"id":"171221","name":"self-charging"},{"id":"14924","name":"Zhong Wang"}],"core_research_areas":[{"id":"39451","name":"Electronics and Nanotechnology"},{"id":"39531","name":"Energy and Sustainable Infrastructure"},{"id":"39471","name":"Materials"}],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News \u0026amp; Publications Office\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}