Nanoscale elastic changes in 2D Ti3C2Tx (MXene) pseudocapacitive electrodes

Come, Jeremy; Xie, Yu; Naguib, Michael; Jesse, Stephen; Kalinin, Sergei V.; Gogotsi, Yury; Kent, Paul R.  C.; Balke, Nina

doi:10.1002/aenm.201502290

Title: Nanoscale elastic changes in 2D Ti₃C₂T_x (MXene) pseudocapacitive electrodes

Journal Article · Mon Feb 01 00:00:00 EST 2016 · Advanced Energy Materials

DOI:https://doi.org/10.1002/aenm.201502290· OSTI ID:1240569

Come, Jeremy ^[1]; Xie, Yu ^[1]; Naguib, Michael ^[2]; Jesse, Stephen ^[1]; Kalinin, Sergei V. ^[3]; Gogotsi, Yury ^[4]; Kent, Paul R. C. ^[5]; Balke, Nina ^[1]

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, P.O. Box 2008 Oak Ridge TN 37831 USA
Department of Materials Science and Engineering and A.J. Drexel Nanomaterials Institute, Drexel University, Philadelphia PA 19104 USA
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science ; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computer Science and Mathematics Division

Designing sustainable electrodes for next generation energy storage devices relies on the understanding of their fundamental properties at the nanoscale, including the comprehension of ions insertion into the electrode and their interactions with the active material. One consequence of ion storage is the change in the electrode volume resulting in mechanical strain and stress that can strongly affect the cycle life. Therefore, it is important to understand the changes of dimensions and mechanical properties occurring during electrochemical reactions. While the characterization of mechanical properties via macroscopic measurements is well documented, in-situ characterization of their evolution has never been achieved at the nanoscale. Two dimensional (2D) carbides, known as MXenes, are promising materials for supercapacitors and various kinds of batteries, and understating the coupling between their mechanical and electrochemical properties is therefore necessary. Here we report on in-situ imaging, combined with density functional theory of the elastic changes, of a 2D titanium carbide (Ti₃C₂T_x) electrode in direction normal to the basal plane during cation intercalation. The results show a strong correlation between the Li+ ions content and the elastic modulus, whereas little effects of K+ ions are observed. Moreover, this strategy enables identifying the preferential intercalation pathways within a single particle.

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Research Organization:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Energy Frontier Research Centers (EFRC) (United States). Fluid Interface Reactions, Structures and Transport Center (FIRST)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

Grant/Contract Number:: AC02-05CH11231; AC0500OR22725

OSTI ID:: 1240569

Journal Information:: Advanced Energy Materials, Journal Name: Advanced Energy Materials; ISSN 1614-6832

Publisher:: WileyCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 96 works

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References (60)

Resonant internal quantum transitions and femtosecond radiative decay of excitons in monolayer WSe2 Poellmann, C.; Steinleitner, P.; Leierseder, U. Nature Materials, Vol. 14, Issue 9 https://doi.org/10.1038/nmat4356	journal	July 2015
Operation of Graphene Transistors at Gigahertz Frequencies Lin, Yu-Ming; Jenkins, Keith A.; Valdes-Garcia, Alberto Nano Letters, Vol. 9, Issue 1, p. 422-426 https://doi.org/10.1021/nl803316h	journal	January 2009
Liquid-Mediated Dense Integration of Graphene Materials for Compact Capacitive Energy Storage Yang, X.; Cheng, C.; Wang, Y. Science, Vol. 341, Issue 6145 https://doi.org/10.1126/science.1239089	journal	August 2013
Frictional Characteristics of Atomically Thin Sheets Lee, C.; Li, Q.; Kalb, W. Science, Vol. 328, Issue 5974, p. 76-80 https://doi.org/10.1126/science.1184167	journal	April 2010
Room-temperature metastability of multilayer graphene oxide films Kim, Suenne; Zhou, Si; Hu, Yike Nature Materials, Vol. 11, Issue 6 https://doi.org/10.1038/nmat3316	journal	May 2012
Atomic layers of hybridized boron nitride and graphene domains Ci, Lijie; Song, Li; Jin, Chuanhong Nature Materials, Vol. 9, Issue 5, p. 430-435 https://doi.org/10.1038/nmat2711	journal	February 2010
Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene Lee, C.; Wei, X.; Kysar, J. W. Science, Vol. 321, Issue 5887, p. 385-388 https://doi.org/10.1126/science.1157996	journal	July 2008
Theory of the elastic constants of graphite and graphene Michel, K. H.; Verberck, B. physica status solidi (b), Vol. 245, Issue 10 https://doi.org/10.1002/pssb.200879604	journal	August 2008
Elastic coupling between layers in two-dimensional materials Gao, Yang; Kim, Suenne; Zhou, Si Nature Materials, Vol. 14, Issue 7 https://doi.org/10.1038/nmat4322	journal	June 2015
Local elastic properties of a metallic glass Wagner, Hannes; Bedorf, Dennis; Küchemann, Stefan Nature Materials, Vol. 10, Issue 6 https://doi.org/10.1038/nmat3024	journal	May 2011
Non-Invasive In Situ Dynamic Monitoring of Elastic Properties of Composite Battery Electrodes by EQCM-D Shpigel, Netanel; Levi, Mikhael D.; Sigalov, Sergey Angewandte Chemie International Edition, Vol. 54, Issue 42 https://doi.org/10.1002/anie.201501787	journal	April 2015
Partially reduced graphite oxide for supercapacitor electrodes: Effect of graphene layer spacing and huge specific capacitance Hantel, M. M.; Kaspar, T.; Nesper, R. Electrochemistry Communications, Vol. 13, Issue 1 https://doi.org/10.1016/j.elecom.2010.11.021	journal	January 2011
In situ tracking of the nanoscale expansion of porous carbon electrodes Arruda, Thomas M.; Heon, Min; Presser, Volker Energy Environ. Sci., Vol. 6, Issue 1 https://doi.org/10.1039/C2EE23707E	journal	January 2013
In situ electrochemical dilatometry of carbide-derived carbons Hantel, M. M.; Presser, V.; Kötz, R. Electrochemistry Communications, Vol. 13, Issue 11 https://doi.org/10.1016/j.elecom.2011.08.039	journal	November 2011
Parameters determining dimensional changes of porous carbons during capacitive charging Hantel, M. M.; Weingarth, D.; Kötz, R. Carbon, Vol. 69 https://doi.org/10.1016/j.carbon.2013.12.026	journal	April 2014
Real Space Mapping of Li-Ion Transport in Amorphous Si Anodes with Nanometer Resolution Balke, Nina; Jesse, Stephen; Kim, Yoongu Nano Letters, Vol. 10, Issue 9 https://doi.org/10.1021/nl101439x	journal	September 2010
Two-Dimensional Transition Metal Carbides Naguib, Michael; Mashtalir, Olha; Carle, Joshua ACS Nano, Vol. 6, Issue 2 https://doi.org/10.1021/nn204153h	journal	January 2012
Two-Dimensional Nanocrystals Produced by Exfoliation of Ti₃AlC₂ Naguib, Michael; Kurtoglu, Murat; Presser, Volker Advanced Materials, Vol. 23, Issue 37, p. 4248-4253 https://doi.org/10.1002/adma.201102306	journal	August 2011
Synthesis of Two-Dimensional Materials by Selective Extraction Naguib, Michael; Gogotsi, Yury Accounts of Chemical Research, Vol. 48, Issue 1 https://doi.org/10.1021/ar500346b	journal	December 2014
Synthesis and characterization of two-dimensional Nb ₄ C ₃ (MXene) Ghidiu, M.; Naguib, M.; Shi, C. Chem. Commun., Vol. 50, Issue 67 https://doi.org/10.1039/C4CC03366C	journal	January 2014
25th Anniversary Article: MXenes: A New Family of Two-Dimensional Materials Naguib, Michael; Mochalin, Vadym N.; Barsoum, Michel W. Advanced Materials, Vol. 26, Issue 7, p. 992-1005 https://doi.org/10.1002/adma.201304138	journal	December 2013
Achieving Type I, II, and III Heterojunctions Using Functionalized MXene Lee, Youngbin; Hwang, Yubin; Chung, Yong-Chae ACS Applied Materials & Interfaces, Vol. 7, Issue 13 https://doi.org/10.1021/acsami.5b00063	journal	March 2015
Carbon nanofiber bridged two-dimensional titanium carbide as a superior anode for lithium-ion batteries Lin, Zongyuan; Sun, Dongfei; Huang, Qing Journal of Materials Chemistry A, Vol. 3, Issue 27 https://doi.org/10.1039/C5TA01855B	journal	January 2015
Large-area high-quality 2D ultrathin Mo2C superconducting crystals Xu, Chuan; Wang, Libin; Liu, Zhibo Nature Materials, Vol. 14, Issue 11 https://doi.org/10.1038/nmat4374	journal	August 2015
First principles study of two-dimensional early transition metal carbides Kurtoglu, Murat; Naguib, Michael; Gogotsi, Yury MRS Communications, Vol. 2, Issue 4 https://doi.org/10.1557/mrc.2012.25	journal	October 2012
Molecular dynamic study of the mechanical properties of two-dimensional titanium carbides Ti _{n +1} C _n (MXenes) Borysiuk, Vadym N.; Mochalin, Vadym N.; Gogotsi, Yury Nanotechnology, Vol. 26, Issue 26 https://doi.org/10.1088/0957-4484/26/26/265705	journal	June 2015
MXene: a promising transition metal carbide anode for lithium-ion batteries Naguib, Michael; Come, Jérémy; Dyatkin, Boris Electrochemistry Communications, Vol. 16, Issue 1, p. 61-64 https://doi.org/10.1016/j.elecom.2012.01.002	journal	March 2012
A Non-Aqueous Asymmetric Cell with a Ti ₂ C-Based Two-Dimensional Negative Electrode Come, J.; Naguib, M.; Rozier, P. Journal of The Electrochemical Society, Vol. 159, Issue 8 https://doi.org/10.1149/2.003208jes	journal	January 2012
Conductive two-dimensional titanium carbide ‘clay’ with high volumetric capacitance Ghidiu, Michael; Lukatskaya, Maria R.; Zhao, Meng-Qiang Nature, Vol. 516, Issue 7529 https://doi.org/10.1038/nature13970	journal	November 2014
Probing the Mechanism of High Capacitance in 2D Titanium Carbide Using In Situ X-Ray Absorption Spectroscopy Lukatskaya, Maria R.; Bak, Seong-Min; Yu, Xiqian Advanced Energy Materials, Vol. 5, Issue 15 https://doi.org/10.1002/aenm.201500589	journal	May 2015
Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide Lukatskaya, M. R.; Mashtalir, O.; Ren, C. E. Science, Vol. 341, Issue 6153 https://doi.org/10.1126/science.1241488	journal	September 2013
Controlling the actuation properties of MXene paper electrodes upon cation intercalation Come, Jeremy; Black, Jennifer M.; Lukatskaya, Maria R. Nano Energy, Vol. 17 https://doi.org/10.1016/j.nanoen.2015.07.028	journal	October 2015
Solving the Capacitive Paradox of 2D MXene using Electrochemical Quartz-Crystal Admittance and In Situ Electronic Conductance Measurements Levi, Mikhael D.; Lukatskaya, Maria R.; Sigalov, Sergey Advanced Energy Materials, Vol. 5, Issue 1 https://doi.org/10.1002/aenm.201400815	journal	August 2014
Quantitative Viscoelastic Mapping of Polyolefin Blends with Contact Resonance Atomic Force Microscopy Yablon, Dalia G.; Gannepalli, Anil; Proksch, Roger Macromolecules, Vol. 45, Issue 10 https://doi.org/10.1021/ma2028038	journal	May 2012
Mapping nanoscale elasticity and dissipation using dual frequency contact resonance AFM Gannepalli, A.; Yablon, D. G.; Tsou, A. H. Nanotechnology, Vol. 22, Issue 35 https://doi.org/10.1088/0957-4484/22/35/355705	journal	August 2011
Nanomechanical surface characterization by atomic force acoustic microscopy Rabe, U. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, Vol. 15, Issue 4 https://doi.org/10.1116/1.589484	journal	July 1997
Imaging and measurement of local mechanical material properties by atomic force acoustic microscopy: Mechanical materials properties by AFAM Rabe, U.; Amelio, S.; Kopycinska, M. Surface and Interface Analysis, Vol. 33, Issue 2 https://doi.org/10.1002/sia.1163	journal	February 2002
Contact-resonance atomic force microscopy for nanoscale elastic property measurements: Spectroscopy and imaging Stan, G.; Krylyuk, S.; Davydov, A. V. Ultramicroscopy, Vol. 109, Issue 8 https://doi.org/10.1016/j.ultramic.2009.03.025	journal	July 2009
Probing Local Bias-Induced Transitions Using Photothermal Excitation Contact Resonance Atomic Force Microscopy and Voltage Spectroscopy Li, Qian; Jesse, Stephen; Tselev, Alexander ACS Nano, Vol. 9, Issue 2 https://doi.org/10.1021/nn506753u	journal	January 2015
Contact resonance atomic force microscopy imaging in air and water using photothermal excitation Kocun, Marta; Labuda, Aleksander; Gannepalli, Anil Review of Scientific Instruments, Vol. 86, Issue 8 https://doi.org/10.1063/1.4928105	journal	August 2015
The band excitation method in scanning probe microscopy for rapid mapping of energy dissipation on the nanoscale Jesse, Stephen; Kalinin, Sergei V.; Proksch, Roger Nanotechnology, Vol. 18, Issue 43 https://doi.org/10.1088/0957-4484/18/43/435503	journal	September 2007
Quantitative determination of contact stiffness using atomic force acoustic microscopy Rabe, U.; Amelio, S.; Kester, E. Ultrasonics, Vol. 38, Issue 1-8, p. 430-437 https://doi.org/10.1016/S0041-624X(99)00207-3	journal	March 2000
Liquid contact resonance AFM: analytical models, experiments, and limitations Parlak, Zehra; Tu, Qing; Zauscher, Stefan Nanotechnology, Vol. 25, Issue 44 https://doi.org/10.1088/0957-4484/25/44/445703	journal	October 2014
Liquid contact resonance atomic force microscopy via experimental reconstruction of the hydrodynamic function Tung, Ryan C.; Killgore, Jason P.; Hurley, Donna C. Journal of Applied Physics, Vol. 115, Issue 22 https://doi.org/10.1063/1.4882755	journal	June 2014
X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes) Halim, Joseph; Cook, Kevin M.; Naguib, Michael Applied Surface Science, Vol. 362 https://doi.org/10.1016/j.apsusc.2015.11.089	journal	January 2016
Role of Surface Structure on Li-Ion Energy Storage Capacity of Two-Dimensional Transition-Metal Carbides Xie, Yu; Naguib, Michael; Mochalin, Vadym N. Journal of the American Chemical Society, Vol. 136, Issue 17 https://doi.org/10.1021/ja501520b	journal	April 2014
Resolving the Structure of Ti ₃ C ₂ T _x MXenes through Multilevel Structural Modeling of the Atomic Pair Distribution Function Wang, Hsiu-Wen; Naguib, Michael; Page, Katharine Chemistry of Materials, Vol. 28, Issue 1 https://doi.org/10.1021/acs.chemmater.5b04250	journal	December 2015
High capacitance of surface-modified 2D titanium carbide in acidic electrolyte Dall'Agnese, Yohan; Lukatskaya, Maria R.; Cook, Kevin M. Electrochemistry Communications, Vol. 48 https://doi.org/10.1016/j.elecom.2014.09.002	journal	November 2014
Kinetics of aluminum extraction from Ti3AlC2 in hydrofluoric acid Mashtalir, Olha; Naguib, Michael; Dyatkin, Boris Materials Chemistry and Physics, Vol. 139, Issue 1 https://doi.org/10.1016/j.matchemphys.2013.01.008	journal	April 2013
Self-Consistent Equations Including Exchange and Correlation Effects Kohn, W.; Sham, L. J. Physical Review, Vol. 140, Issue 4A, p. A1133-A1138 https://doi.org/10.1103/PhysRev.140.A1133	journal	November 1965
Projector augmented-wave method Blöchl, P. E. Physical Review B, Vol. 50, Issue 24, p. 17953-17979 https://doi.org/10.1103/PhysRevB.50.17953	journal	December 1994
Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set Kresse, G.; Furthmüller, J. Physical Review B, Vol. 54, Issue 16, p. 11169-11186 https://doi.org/10.1103/PhysRevB.54.11169	journal	October 1996
Van der Waals density functionals applied to solids Klimeš, Jiří; Bowler, David R.; Michaelides, Angelos Physical Review B, Vol. 83, Issue 19 https://doi.org/10.1103/PhysRevB.83.195131	journal	May 2011
Special points for Brillouin-zone integrations Monkhorst, Hendrik J.; Pack, James D. Physical Review B, Vol. 13, Issue 12, p. 5188-5192 https://doi.org/10.1103/PhysRevB.13.5188	journal	June 1976
Non-Invasive In Situ Dynamic Monitoring of Elastic Properties of Composite Battery Electrodes by EQCM-D Shpigel, Netanel; Levi, Mikhael D.; Sigalov, Sergey Angewandte Chemie, Vol. 127, Issue 42 https://doi.org/10.1002/ange.201501787	journal	April 2015
Electronic structure of AlFeN films exhibiting crystallographic orientation change from c- to a-axis with Fe concentrations and annealing effect Tatemizo, Nobuyuki; Imada, Saki; Okahara, Kizuna Scientific Reports, Vol. 10, Issue 1 https://doi.org/10.1038/s41598-020-58835-5	journal	February 2020
Double transition metal MXene (TixTa4−xC3) 2D materials as anodes for Li-ion batteries Syamsai, Ravuri; Rodriguez, Jassiel R.; Pol, Vilas G. Scientific Reports, Vol. 11, Issue 1 https://doi.org/10.1038/s41598-020-79991-8	journal	January 2021
In situ tracking of the nanoscale expansion of porous carbon electrodes Arruda, Thomas M.; Heon, Min; Presser, Volker Cambridge : Royal Society of Chemistry https://doi.org/10.34657/535	other	January 2013
Resonant internal Quantum transitions and femtosecond radiative decay of excitons in monolayer WSe2 Pöllmann, Christoph; Steinleitner, Philipp; Leierseder, Ursula Universität Regensburg https://doi.org/10.5283/epub.32244	text	January 2015
Van der Waals density functionals applied to solids Klimeš, Jiří; Bowler, David R.; Michaelides, Angelos arXiv https://doi.org/10.48550/arxiv.1102.1358	text	January 2011

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Title: Nanoscale elastic changes in 2D Ti₃C₂T_x (MXene) pseudocapacitive electrodes