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Song, Taeseup,Choung, Jae Woong,Park, Jea-Gun,Park, Won Il,Rogers, John A.,Paik, Ungyu WILEY-VCH Verlag 2008 Advanced Materials Vol.20 No.23
<B>Graphic Abstract</B> <P>Surface polarity and shape-controlled ZnO nanostructures are synthesized on GaN thin films using metalorganic vapor phase epitaxy (MOVPE). By adjusting the growth parameters from Zn-rich at low temperature to O-rich at high temperature, morphology of ZnO nanostructures was tuned from nonpolar, smooth-surfaced ZnO nanorod nanowall networks to O-polar, stacked pyramid-structured ZnO nanorods. <img src='wiley_img/09359648-2008-20-23-ADMA200801190-content.gif' alt='wiley_img/09359648-2008-20-23-ADMA200801190-content'> </P>
A Ge inverse opal with porous walls as an anode for lithium ion batteries
Song, Taeseup,Jeon, Yeryung,Samal, Monica,Han, Hyungkyu,Park, Hyunjung,Ha, Jaehwan,Yi, Dong Kee,Choi, Jae-Man,Chang, Hyuk,Choi, Young-Min,Paik, Ungyu The Royal Society of Chemistry 2012 ENERGY AND ENVIRONMENTAL SCIENCE Vol.5 No.10
<P>Germanium holds great potential as an anode material for lithium ion batteries due to its large theoretical energy density and excellent intrinsic properties related to its kinetics associated with lithium and electrons. However, the problem related to the tremendous volume change of Ge during cycling is the dominant obstacle for its practical use. The previous research has focused on the improvement in mechanics associated with lithium without consideration of the kinetics. In this study, we demonstrate that the configuration engineering of the Ge electrode enables the improvement in kinetics as well as favorable mechanics. Two types of Ge inverse opal structures with porous walls and dense walls were prepared using a confined convective assembly method and by adjusting Ge deposition parameters in a chemical vapor deposition system. The Ge inverse opal electrode with porous walls shows much improved electrochemical performances, especially cycle performance and rate capability, than the electrode with dense walls. These improvements are attributed to a large free surface, which offers a facile strain relaxation pathway and a large lithium flux from the electrolyte to the active material.</P> <P>Graphic Abstract</P><P>A Ge inverse opal with porous walls shows excellent electrochemical performances due to a large free surface, which offers a facile strain relaxation pathway and a large lithium flux from the electrolyte to the active material. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2ee22358a'> </P>
Silicon nanowires with a carbon nanofiber branch as lithium-ion anode material
Song, Taeseup,Lee, Dong Hyun,Kwon, Moon Seok,Choi, Jae Man,Han, Hyungkyu,Doo, Seok Gwang,Chang, Hyuk,Park, Won Il,Sigmund, Wolfgang,Kim, Hansu,Paik, Ungyu Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.34
<P>Si nanowires (SiNWs)–carbon nanofibers (CNFs) branched structures with variation in carbon densities were synthesized. SiNWs with critical density of CNFs show the best electrochemical performance, which is attributed to increase in free volume around the SiNWs as well as a buffering role of the branched CNFs against large volumetric change during cycling.</P> <P>Graphic Abstract</P><P>Si nanowires branched with different densities of carbon nanofibers were synthesized and the effect of geometrical features on electrochemical performances was studied. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm12511g'> </P>
Arrays of Sealed Silicon Nanotubes As Anodes for Lithium Ion Batteries
Song, Taeseup,Xia, Jianliang,Lee, Jin-Hyon,Lee, Dong Hyun,Kwon, Moon-Seok,Choi, Jae-Man,Wu, Jian,Doo, Seok Kwang,Chang, Hyuk,Park, Won Il,Zang, Dong Sik,Kim, Hansu,Huang, Yonggang,Hwang, Keh-Chih,Roge American Chemical Society 2010 NANO LETTERS Vol.10 No.5
<P>Silicon is a promising candidate for electrodes in lithium ion batteries due to its large theoretical energy density. Poor capacity retention, caused by pulverization of Si during cycling, frustrates its practical application. We have developed a nanostructured form of silicon, consisting of arrays of sealed, tubular geometries that is capable of accommodating large volume changes associated with lithiation in battery applications. Such electrodes exhibit high initial Coulombic efficiencies (i.e., >85%) and stable capacity-retention (>80% after 50 cycles), due to an unusual, underlying mechanics that is dominated by free surfaces. This physics is manifested by a strongly anisotropic expansion in which 400% volumetric increases are accomplished with only relatively small (<35%) changes in the axial dimension. These experimental results and associated theoretical mechanics models demonstrate the extent to which nanoscale engineering of electrode geometry can be used to advantage in the design of rechargeable batteries with highly reversible capacity and long-term cycle stability.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-5/nl100086e/production/images/medium/nl-2010-00086e_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl100086e'>ACS Electronic Supporting Info</A></P>
Si/Ge Double-Layered Nanotube Array as a Lithium Ion Battery Anode
Song, Taeseup,Cheng, Huanyu,Choi, Heechae,Lee, Jin-Hyon,Han, Hyungkyu,Lee, Dong Hyun,Yoo, Dong Su,Kwon, Moon-Seok,Choi, Jae-Man,Doo, Seok Gwang,Chang, Hyuk,Xiao, Jianliang,Huang, Yonggang,Park, Won Il American Chemical Society 2012 ACS NANO Vol.6 No.1
<P>Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3<I>C</I> rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-1/nn203572n/production/images/medium/nn-2011-03572n_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203572n'>ACS Electronic Supporting Info</A></P>
Sb-based electrode materials for rechargeable batteries
Liu, Zhiming,Song, Taeseup,Paik, Ungyu The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.18
<P>The demand for green energy conversion and storage for various applications, such as portable electronics, electric vehicles, and large-scale power stations, has boosted the exploration of advanced energy storage technologies. Lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and liquid-metal batteries (LMBs) meet the different requirements of high-energy density, low cost, and large-scale energy storage, respectively. Currently, designing and synthesizing appropriate electrode materials with high performance, abundant natural availability, and low cost are the main challenges for rechargeable battery technology. Recent studies have demonstrated that Sb-based materials are promising electrode candidates for LIBs, SIBs, and LMBs because of their relatively low cost and high electrochemical performance. This review critically presents recent developments in Sb-based electrode materials, including storage mechanisms, synthesis strategies, and applications in LIBs, SIBs, and LMBs. It also presents challenges and prospects on further improving Sb-based electrode materials for real applications.</P>
Germanium coating boosts lithium uptake in Si nanotube battery anodes
Haro, Marta,Song, Taeseup,Guerrero, Antonio,Bertoluzzi, Luca,Bisquert, Juan,Paik, Ungyu,Garcia-Belmonte, Germà The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.33
<P>Si nanotubes for reversible alloying reaction with lithium are able to accommodate large volume changes and offer improved cycle retention and reliable response when incorporated into battery anodes. However, Si nanotube electrodes exhibit poor rate capability because of their inherently low electron conductivity and Li ion diffusivity. Si/Ge double-layered nanotube electrodes show promise to improve structural stability and electrochemical kinetics, as compared to homogeneous Si nanotube arrays. The mechanism explaining the enhancement in the rate capabilities is revealed here by means of electrochemical impedance methods. The Ge shell efficiently provides electrons to the active materials, which increase the semiconductor conductivity thereby assisting Li<SUP>+</SUP> ion incorporation. The charge transfer resistance which accounts for the interfacial Li<SUP>+</SUP> ion intake from the electrolyte is reduced by two orders of magnitude, indicating the key role of the Ge layer as an electron supplier. Other resistive processes hindering the electrode charge–discharge process are observed to show comparable values for Si and Si/Ge array electrodes.</P> <P>Graphic Abstract</P><P>Interfacial charge transfer resistance accounting for Li intake extremely reduced by conductive germanium coating of Si nanotubes. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp02377c'> </P>