Co-reporter:Lukas Porz;Tushar Swamy;Brian W. Sheldon;Daniel Rettenwer;Till Frömling;Henry L. Thaman;Stefan Berendts;Reinhard Uecker;W. Craig Carter
Advanced Energy Materials 2017 Volume 7(Issue 20) pp:
Publication Date(Web):2017/10/01
DOI:10.1002/aenm.201701003
AbstractLi deposition is observed and measured on a solid electrolyte in the vicinity of a metallic current collector. Four types of ion-conducting, inorganic solid electrolytes are tested: Amorphous 70/30 mol% Li2S-P2S5, polycrystalline β-Li3PS4, and polycrystalline and single-crystalline Li6La3ZrTaO12 garnet. The nature of lithium plating depends on the proximity of the current collector to defects such as surface cracks and on the current density. Lithium plating penetrates/infiltrates at defects, but only above a critical current density. Eventually, infiltration results in a short circuit between the current collector and the Li-source (anode). These results do not depend on the electrolytes shear modulus and are thus not consistent with the Monroe–Newman model for “dendrites.” The observations suggest that Li-plating in pre-existing flaws produces crack-tip stresses which drive crack propagation, and an electrochemomechanical model of plating-induced Li infiltration is proposed. Lithium short-circuits through solid electrolytes occurs through a fundamentally different process than through liquid electrolytes. The onset of Li infiltration depends on solid-state electrolyte surface morphology, in particular the defect size and density.
Co-reporter:Kai XiangWenting Xing, Dorthe B. Ravnsbæk, Liang Hong, Ming Tang, Zheng Li, Kamila M. Wiaderek, Olaf J. Borkiewicz, Karena W. Chapman, Peter J. Chupas, Yet-Ming Chiang
Nano Letters 2017 Volume 17(Issue 3) pp:
Publication Date(Web):February 21, 2017
DOI:10.1021/acs.nanolett.6b04971
Virtually all intercalation compounds exhibit significant changes in unit cell volume as the working ion concentration varies. NaxFePO4 (0 < x < 1, NFP) olivine, of interest as a cathode for sodium-ion batteries, is a model for topotactic, high-strain systems as it exhibits one of the largest discontinuous volume changes (∼17% by volume) during its first-order transition between two otherwise isostructural phases. Using synchrotron radiation powder X-ray diffraction (PXD) and pair distribution function (PDF) analysis, we discover a new strain-accommodation mechanism wherein a third, amorphous phase forms to buffer the large lattice mismatch between primary phases. The amorphous phase has short-range order over ∼1nm domains that is characterized by a and b parameters matching one crystalline end-member phase and a c parameter matching the other, but is not detectable by powder diffraction alone. We suggest that this strain-accommodation mechanism may generally apply to systems with large transformation strains.Keywords: batteries; olivines; operando; pair-distribution function; Phase transformations; sodium iron phosphate;
Co-reporter:Xinwei Chen, Brandon J. Hopkins, Ahmed Helal, Frank Y. Fan, Kyle C. Smith, Zheng Li, Alexander H. Slocum, Gareth H. McKinley, W. Craig Carter and Yet-Ming Chiang
Energy & Environmental Science 2016 vol. 9(Issue 5) pp:1760-1770
Publication Date(Web):11 Apr 2016
DOI:10.1039/C6EE00874G
Redox flow batteries have the potential to provide low-cost energy storage to enable renewable energy technologies such as wind and solar to overcome their inherent intermittency and to improve the efficiency of electric grids. Conventional flow batteries are complex electromechanical systems designed to simultaneously control flow of redox active fluids and perform electrochemical functions. With the advent of redox active fluids with high capacity density, i.e., Faradaic capacity significantly exceeding the 1–2 M concentration equivalents typical of aqueous redox flow batteries, new flow battery designs become of interest. Here, we design and demonstrate a proof-of-concept prototype for a “gravity-induced flow cell” (GIFcell), representing one of a family of approaches to simpler, more robust, passively driven, lower-cost flow battery architectures. Such designs are particularly appropriate for semi-solid electrodes comprising suspensions of networked conductors and/or electroactive particles, due to their low energy dissipation during flow. Accordingly, we demonstrate the GIFcell using nonaqueous lithium polysulfide solutions containing a nanoscale carbon network in a half-flow-cell configuration and achieve round trip energy efficiency as high as 91%.
Co-reporter:Frank Y. Fan;W. Craig Carter
Advanced Materials 2015 Volume 27( Issue 35) pp:5203-5209
Publication Date(Web):
DOI:10.1002/adma.201501559
Co-reporter:Zheng Li;Kai Xiang;Wenting Xing;W. Craig Carter
Advanced Energy Materials 2015 Volume 5( Issue 5) pp:
Publication Date(Web):
DOI:10.1002/aenm.201401410
Co-reporter:Sarawut Pongha;Boonyarit Seekoaon;Wanwisa Limphirat;Pinit Kidkhunthod;Sutham Srilomsak;Nonglak Meethong
Advanced Energy Materials 2015 Volume 5( Issue 15) pp:
Publication Date(Web):
DOI:10.1002/aenm.201500663
Dynamic phase transformation in olivine LiFePO4 involving formation of one or more intermediate or metastable phases is revealed by an in situ time-resolved X-ray absorption near edge structure (XANES) technique. The XANES spectra measured during relaxation immediately after the application of relatively high overpotentials, where metastable phases are expected, show a continuous shift of the Fe K-edge toward higher energy. Surprisingly, the Fe K-edge relaxes to higher energies after current interrupt regardless of whether the cell is being charged or discharged. This relaxation phenomenon is superimposed upon larger shifts in K-edge due to changes in Fe2+/Fe3+ ratio due to charging and discharging, and implies an intermediate phase of larger FeO bond length than any of the known crystalline phases. No intermediate crystalline phases are observed by X-ray diffraction (XRD). A metastable amorphous phase formed during dynamic cycling and which structurally relaxes to the equilibrium crystalline phases over a time scale of about 10 min after cessation of charging/discharging current is consistent with the experimental observations.
Co-reporter:Teng-Sing Wei;Frank Y. Fan;Ahmed Helal;Kyle C. Smith;Gareth H. McKinley;Jennifer A. Lewis
Advanced Energy Materials 2015 Volume 5( Issue 15) pp:
Publication Date(Web):
DOI:10.1002/aenm.201500535
Co-reporter:Maryam Moradi, Zheng Li, Jifa Qi, Wenting Xing, Kai Xiang, Yet-Ming Chiang, and Angela M. Belcher
Nano Letters 2015 Volume 15(Issue 5) pp:2917-2921
Publication Date(Web):March 26, 2015
DOI:10.1021/nl504676v
In this work we investigated an energy-efficient biotemplated route to synthesize nanostructured FePO4 for sodium-based batteries. Self-assembled M13 viruses and single wall carbon nanotubes (SWCNTs) have been used as a template to grow amorphous FePO4 nanoparticles at room temperature (the active composite is denoted as Bio-FePO4-CNT) to enhance the electronic conductivity of the active material. Preliminary tests demonstrate a discharge capacity as high as 166 mAh/g at C/10 rate, corresponding to composition Na0.9FePO4, which along with higher C-rate tests show this material to have the highest capacity and power performance reported for amorphous FePO4 electrodes to date.
Co-reporter:D. B. Ravnsbæk, K. Xiang, W. Xing, O. J. Borkiewicz, K. M. Wiaderek, P. Gionet, K. W. Chapman, P. J. Chupas, and Y.-M. Chiang
Nano Letters 2014 Volume 14(Issue 3) pp:1484-1491
Publication Date(Web):February 18, 2014
DOI:10.1021/nl404679t
Nanoparticle LiFePO4, the basis for an entire class of high power Li-ion batteries, has recently been shown to exist in binary lithiated/delithiated states at intermediate states of charge. The Mn-bearing version, LiMnyFe1–yPO4, exhibits even higher rate capability as a lithium battery cathode than LiFePO4 of comparable particle size. To gain insight into the cause(s) of this desirable performance, the electrochemically driven phase transformation during battery charge and discharge of nanoscale LiMn0.4Fe0.6PO4 of three different average particle sizes, 52, 106, and 152 nm, is investigated by operando synchrotron radiation powder X-ray diffraction. In stark contrast to the binary lithiation states of pure LiFePO4 revealed in recent investigations, the formations of metastable solid solutions covering a remarkable wide compositional range, including while in two-phase coexistence, are observed. Detailed analysis correlates this behavior with small elastic misfits between phases compared to either pure LiFePO4 or LiMnPO4. On the basis of time- and state-of-charge dependence of the olivine structure parameters, we propose a coherent transformation mechanism. These findings illustrate a second, completely different phase transformation mode for pure well-ordered nanoscale olivines compared to the well-studied case of LiFePO4.
Co-reporter:Frank Y. Fan, William H. Woodford, Zheng Li, Nir Baram, Kyle C. Smith, Ahmed Helal, Gareth H. McKinley, W. Craig Carter, and Yet-Ming Chiang
Nano Letters 2014 Volume 14(Issue 4) pp:2210-2218
Publication Date(Web):March 5, 2014
DOI:10.1021/nl500740t
A new approach to flow battery design is demonstrated wherein diffusion-limited aggregation of nanoscale conductor particles at ∼1 vol % concentration is used to impart mixed electronic-ionic conductivity to redox solutions, forming flow electrodes with embedded current collector networks that self-heal after shear. Lithium polysulfide flow cathodes of this architecture exhibit electrochemical activity that is distributed throughout the volume of flow electrodes rather than being confined to surfaces of stationary current collectors. The nanoscale network architecture enables cycling of polysulfide solutions deep into precipitation regimes that historically have shown poor capacity utilization and reversibility and may thereby enable new flow battery designs of higher energy density and lower system cost. Lithium polysulfide half-flow cells operating in both continuous and intermittent flow mode are demonstrated for the first time.
Co-reporter:Zheng Li, Dorthe B. Ravnsbæk, Kai Xiang, Yet-Ming Chiang
Electrochemistry Communications 2014 Volume 44() pp:12-15
Publication Date(Web):July 2014
DOI:10.1016/j.elecom.2014.04.003
Na3Ti2(PO4)3 synthesized as fine carbon-coated powders is demonstrated for the first time to be a suitable sodium-bearing anode material for rechargeable aqueous sodium-ion batteries (ANaBs). Importantly, Na3Ti2(PO4)3 is found to be stable in deoxygenated water, enabling use of this material in aqueous systems. As a sodiated anode, it allows use of sodium-depleted cathode materials that require supply of sodium-ions from the anode. As an example, we demonstrate for the first time the use of olivine FePO4 as a cathode in an ANaB.
Co-reporter:Zheng Li, Dorthe B. Ravnsbæk, Kai Xiang, Yet-Ming Chiang
Electrochemistry Communications 2014 Volume 44() pp:78
Publication Date(Web):July 2014
DOI:10.1016/j.elecom.2014.05.004
Co-reporter:Chang-Jun Bae;Can K. Erdonmez;John W. Halloran
Advanced Materials 2013 Volume 25( Issue 9) pp:1254-1258
Publication Date(Web):
DOI:10.1002/adma.201204055
Co-reporter:Zheng Li;David Young;Kai Xiang;W. Craig Carter
Advanced Energy Materials 2013 Volume 3( Issue 3) pp:290-294
Publication Date(Web):
DOI:10.1002/aenm.201200598
Co-reporter:David Young;Alan Ransil;Ruhul Amin;Zheng Li
Advanced Energy Materials 2013 Volume 3( Issue 9) pp:1125-1129
Publication Date(Web):
DOI:10.1002/aenm.201300134
Co-reporter:Zheng Li, Kyle C. Smith, Yajie Dong, Nir Baram, Frank Y. Fan, Jing Xie, Pimpa Limthongkul, W. Craig Carter and Yet-Ming Chiang
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 38) pp:15833-15839
Publication Date(Web):16 Aug 2013
DOI:10.1039/C3CP53428F
An aqueous Li-ion flow cell using suspension-based flow electrodes based on the LiTi2(PO4)3–LiFePO4 couple is demonstrated. Unlike conventional flow batteries, the semi-solid approach utilizes fluid electrodes that are electronically conductive. A model of simultaneous advection and electrochemical transport is developed and used to separate flow-induced losses from those due to underlying side reactions. The importance of plug flow to achieving high energy efficiency in flow batteries utilizing highly non-Newtonian flow electrodes is emphasized.
Co-reporter:William H. Woodford, W. Craig Carter and Yet-Ming Chiang
Energy & Environmental Science 2012 vol. 5(Issue 7) pp:8014-8024
Publication Date(Web):04 May 2012
DOI:10.1039/C2EE21874G
Mechanical degradation of electrode active materials (“electrochemical shock”) contributes to impedance growth of battery electrodes, but relatively few design criteria have been developed to mitigate fracture. Using micromechanical models and in situ acoustic emission experiments, we demonstrate and explain C-rate independent electrochemical shock in polycrystalline electrode materials with anisotropic Vegard coefficients. We conclude that minimizing the principal shear strain, rather than minimizing net volume change as previously suggested, is an important new design criterion for crystal chemical engineering of electrode materials for mechanical reliability. Polycrystalline particles of anisotropic Li-storage materials should be synthesized with primary crystallite sizes smaller than a material-specific critical size to avoid fracture along grain boundaries. Finally, we revise the electrochemical shock map construction to incorporate the material-specific critical microstructure feature sizes for C-rate independent electrochemical shock mechanisms, providing a simple tool for designing long-lived battery electrodes.
Co-reporter:Mihai Duduta;Bryan Ho;Vanessa C. Wood;Pimpa Limthongkul;Victor E. Brunini;W. Craig Carter
Advanced Energy Materials 2011 Volume 1( Issue 4) pp:511-516
Publication Date(Web):
DOI:10.1002/aenm.201100152
Co-reporter:Mihai Duduta;Bryan Ho;Vanessa C. Wood;Pimpa Limthongkul;Victor E. Brunini;W. Craig Carter
Advanced Energy Materials 2011 Volume 1( Issue 4) pp:
Publication Date(Web):
DOI:10.1002/aenm.201190017
Co-reporter:Wei Lai;Can K. Erdonmez;Thomas F. Marinis;Caroline K. Bjune;Nancy J. Dudney;Fan Xu;Ryan Wartena
Advanced Materials 2010 Volume 22( Issue 20) pp:E139-E144
Publication Date(Web):
DOI:10.1002/adma.200903650
Co-reporter:Yet-Ming Chiang;Nonglak Meethong;Yu-Hua Kao
Advanced Functional Materials 2010 Volume 20( Issue 2) pp:189-191
Publication Date(Web):
DOI:10.1002/adfm.200901771
No abstract is available for this article.
Co-reporter:Nonglak Meethong, Yu-Hua Kao, W. Craig Carter and Yet-Ming Chiang
Chemistry of Materials 2010 Volume 22(Issue 3) pp:1088
Publication Date(Web):September 29, 2009
DOI:10.1021/cm902118m
Crystallite size and composition effects on the kinetics of lithium storage in olivines are studied using potentiostatic intermittent titration tests (PITT). Here we compare undoped Li1-xFePO4 of 113 nm, 42 nm, and 34 nm average particle size, and three aliovalent solute doped compositions formulated for dopant substitution on the Li (M1) site with charge compensation by Li vacancies: Li0.90Mg0.05FePO4, Li0.80Zr0.05FePO4, and Li0.70Zr0.075FePO4. The results first show that a diffusive component can be measured with reasonable accuracy in all samples, allowing determination of the lithium chemical diffusion coefficient D as a function of potential or state-of-charge. In addition, a method is illustrated for the separation of capacity due to diffusive transport from that due to the first-order phase transition. Using the combined analyses, the effects of particle size reduction and aliovalent doping are readily understood. Both effects contribute to a reduced lithium miscibility gap and a greater contribution to stored capacity of the (faster) diffusive process. Simultaneously, the rate of phase transformation within the miscibility gap is also increased. Highly doped samples exhibit a complete lithium solid solution at room temperature, and have 1−2 orders of magnitude higher D at potentials where significant capacity is stored. This translates to improved capacity retention at high cycling rates, albeit at the expense of reduced absolute capacity due to Li diffusion channel blocking.
Co-reporter:Yu-Hua Kao, Ming Tang, Nonglak Meethong, Jianming Bai, W. Craig Carter, and Yet-Ming Chiang
Chemistry of Materials 2010 Volume 22(Issue 21) pp:5845
Publication Date(Web):October 14, 2010
DOI:10.1021/cm101698b
An objective in battery development for higher storage energy density is the design of compounds that can accommodate maximum changes in ion concentration over useful electrochemical windows. Not surprisingly, many storage compounds undergo phase transitions in situ, including production of metastable phases. Unique to this environment is the frequent application of electrical over- and underpotentials, which are the electrical analogs to undercooling and superheating. Surprisingly, overpotential effects on phase stability and transformation mechanisms have not been studied in detail. Here we use synchrotron X-ray diffraction performed in situ during potentiostatic and galvanostatic cycling, combined with phase-field modeling, to reveal a remarkable dependence of phase transition pathway on overpotential in the model olivine Li1-xFePO4. For a sample of particle size ∼113 nm, at both low (e.g., <20 mV) and high (>75 mV) overpotentials a crystal-to-crystal olivine transformation dominates, whereas at intermediate overpotentials a crystalline-to-amorphous phase transition is preferred. As particle sizes decrease to the nanoscale, amorphization is further emphasized. Implications for battery use and design are considered.
Co-reporter:Nonglak Meethong;Yu-Hua Kao;Scott A. Speakman
Advanced Functional Materials 2009 Volume 19( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/adfm.200990023
Co-reporter:Nonglak Meethong;Yu-Hua Kao;Scott A. Speakman
Advanced Functional Materials 2009 Volume 19( Issue 7) pp:1060-1070
Publication Date(Web):
DOI:10.1002/adfm.200801617
Abstract
Lithium transition metal phosphate olivines are enabling a new generation of high power, thermally stable, long-life rechargeable lithium batteries that may prove instrumental in the worldwide effort to develop cleaner and more sustainable energy. Nanoscale (<100 nm) derivatives of the olivine family LiMPO4 (M = Fe, Mn, Co, Ni) are being adopted in applications ranging in size scale from hybrid and plug-in hybrid electric vehicles to utilities-scale power regulation. Following the previous paradigm set with intercalation oxides, most studies have focused on the pure ordered compounds and isovalent substitutions. In contrast, even the possibility for, and role of, aliovalent doping has been widely debated. Here, critical tests of plausible defect compensation mechanisms using compositions designed to accommodate Mg2+, Al3+, Zr4+, Nb5+ ions on the M1 and/or M2 sites of LiFePO4 with appropriate charge-compensating defects are carried out, and conclusive crystallographic evidence for lattice doping, e.g., up to at least 12 atomic percent added Zr, is obtained. Structural and electrochemical analyses show that doping can reduce the lithium miscibility gap, increase phase transformation kinetics during cycling, and expand Li diffusion channels in the structure. Aliovalent modifications may be effective for introducing controlled atomic disorder into the ordered olivine structure to improve battery performance.
Co-reporter:Vyom Sharma, Qingfeng Yan, C.C. Wong, W. Craig Carter, Yet-Ming Chiang
Journal of Colloid and Interface Science 2009 Volume 333(Issue 1) pp:230-236
Publication Date(Web):1 May 2009
DOI:10.1016/j.jcis.2009.01.047
Oppositely charged colloidal particles in suspension undergo rapid coagulation in the absence of any repulsive component in the interaction potential. With an added steric component serving as the repulsive force it is possible to order oppositely charged particles, which are also weakly charged, in solution. However given the novel features obtainable for an ordered structure from strong oppositely charged particles it becomes imperative to gain a full understanding of methods that can order these particles. Here we report a simple and rapid layer-by-layer method to order strongly and oppositely charged particles. Although this method is in principle scalable to order multiple layers of oppositely charged particles, herein we report ordering of one layer of positively charged particles onto a substrate made of negatively charged particles. This method utilizes a non-ionic surfactant to induce a steric repulsive force between particles and involves spin-coating to disperse and order particles on a very short time scale. The ordered structure obtained through this process is verified as the structure with one of the lowest interaction energies.Ordering of oppositely charged polystyrene (PS) particles with and without a non-ionic, amphiphilic surfactant are presented. Spin coating of positive PS on negative PS without (A) and with (B) Triton X-100.
Co-reporter:Nonglak Meethong, Yu-Hua Kao, Ming Tang, Hsiao-Ying Huang, W. Craig Carter and Yet-Ming Chiang
Chemistry of Materials 2008 Volume 20(Issue 19) pp:6189
Publication Date(Web):September 23, 2008
DOI:10.1021/cm801722f
The phase stability and phase transformation kinetics of Li1−xMPO4 olivines are critical to their performance as lithium storage electrodes. In this work, nanoscale (<100 nm primary particle size) Li1−xFePO4 and Li1−xMnPO4 are chosen as model systems for comparison with a coarser-grained LiFePO4 that exhibits a conventional two-phase reaction. The nanoscale materials first exhibit time and state-of-charge dependences of the electrochemical potential and structural parameters which show that stable two-phase coexistence is not reached. The evolution of structural parameters supports the existence of a coherency stress influenced crystal−crystal transformation. However, an additional response, the preferential formation of amorphous phase at nanosize scale, is identified. In Li1−xFePO4, at 34 nm average particle size, at least one amorphous phase of varying Li content coexists with the crystalline phases. In Li1−xMnPO4 of 78 nm particle size, the electrochemically formed delithiated phase is highly disordered. These phenomena are interpreted from the effect of surface and bulk energetics on phase stability of a nanoscale material.
Co-reporter:Ki Tae Nam;Ryan Wartena;Pil J. Yoo;Paula T. Hammond;Yun Jung Lee;Forrest W. Liau;Angela M. Belcher
PNAS 2008 Volume 105 (Issue 45 ) pp:17227-17231
Publication Date(Web):2008-11-11
DOI:10.1073/pnas.0711620105
The fabrication and spatial positioning of electrodes are becoming central issues in battery technology because of emerging
needs for small scale power sources, including those embedded in flexible substrates and textiles. More generally, novel electrode
positioning methods could enable the use of nanostructured electrodes and multidimensional architectures in new battery designs
having improved electrochemical performance. Here, we demonstrate the synergistic use of biological and nonbiological assembly
methods for fabricating and positioning small battery components that may enable high performance microbatteries with complex
architectures. A self-assembled layer of virus-templated cobalt oxide nanowires serving as the active anode material in the
battery anode was formed on top of microscale islands of polyelectrolyte multilayers serving as the battery electrolyte, and
this assembly was stamped onto platinum microband current collectors. The resulting electrode arrays exhibit full electrochemical
functionality. This versatile approach for fabricating and positioning electrodes may provide greater flexibility for implementing
advanced battery designs such as those with interdigitated microelectrodes or 3D architectures.
Co-reporter:N. Meethong;H.-Y. S. Huang;S. A. Speakman;W. C. Carter;Y.-M. Chiang
Advanced Functional Materials 2007 Volume 17(Issue 7) pp:
Publication Date(Web):21 MAR 2007
DOI:10.1002/adfm.200600938
High energy lithium-ion batteries have improved performance in a wide variety of mobile electronic devices. A new goal in portable power is the achievement of safe and durable high-power batteries for applications such as power tools and electric vehicles. Towards this end, olivine-based positive electrodes are amongst the most important and technologically enabling materials. While certain lithium metal phosphate olivines have been shown to be promising, not all olivines demonstrate beneficial properties. The mechanisms allowing high power in these compounds have been extensively debated. Here we show that certain high rate capability olivines are distinguished by having extended lithium nonstoichiometry (up to ca. 20 %), with which is correlated a reduced lattice misfit as the material undergoes an electrochemically driven, reversible, first-order phase transformation. The rate capability in several other intercalation oxides can also be correlated with lattice strain, and suggests that nanomechanics plays an important and previously unrecognized role in determining battery performance.
Co-reporter:Y. K. Cho;R. Wartena;S. M. Tobias;Y.-M. Chiang
Advanced Functional Materials 2007 Volume 17(Issue 3) pp:
Publication Date(Web):1 FEB 2007
DOI:10.1002/adfm.200600846
A new general approach to the direct formation of bipolar devices from heterogeneous colloids is suggested. By using surface-force theory and direct measurements, combinations of conductive device materials between which short-range repulsive forces exist in the presence of an intervening liquid, and use these interactions to self-form electrochemical junctions are identified. The inclusion of Lifshitz–van der Waals (LW) and acid–base (AB) interactions appears to be generally sufficient for the prediction of short-range interactions. Device concepts using repulsive and attractive short-range interactions to produce self-organizing colloidal-scale devices are proposed and demonstrated. A prototype self-organizing lithium rechargeable battery is demonstrated using lithium cobalt oxide (LiCoO2) and graphite as the active electrode materials.
Co-reporter:Y. Koyama;T. E. Chin;U. Rhyner;R. K. Holman;S. R. Hall;Y.-M. Chiang
Advanced Functional Materials 2006 Volume 16(Issue 4) pp:
Publication Date(Web):10 JAN 2006
DOI:10.1002/adfm.200500633
High-strain, high-force mechanical actuation technologies are desirable for numerous applications ranging from microelectromechanical systems (MEMS) to large-scale “smart structures” that are able to change shape to optimize performance. Here we show that electrochemical intercalation of inorganic compounds of high elastic modulus offers a low-voltage mechanism (less than 5 V) with intrinsic energy density approaching that of hydraulics and more than a hundred times greater than that of existing field-operated mechanisms, such as piezostriction and magnetostriction. Exploitation of the reversible crystallographic strains (several percent) of intercalation compounds while under high stress is key to realization of the available energy. Using a micromachined actuator design, we test the strain capability of oriented graphite due to electrochemical lithiation under stresses up to 200 MPa. We further demonstrate that simultaneous electrochemical expansion of the LiCoO2/graphite cathode/anode couple can be exploited for actuation under stresses up to ∼ 20 MPa in laminated macroscopic composite actuators of similar design to current lithium-ion batteries. While the transport-limited actuation mechanism of these devices results in intrinsically slower actuation compared to most ferroic materials, we demonstrate up to 6.7 mHz (150 s) cyclic actuation in a laminated actuator designed for a high charge/discharge rate. The potential for a new class of high-strain, high-force, moderate-frequency actuators suitable for a broad range of applications is suggested.
Co-reporter:Jian Luo, Ming Tang, Rowland M. Cannon, W. Craig Carter, Yet-Ming Chiang
Materials Science and Engineering: A 2006 Volume 422(1–2) pp:19-28
Publication Date(Web):25 April 2006
DOI:10.1016/j.msea.2006.01.001
Recent observations of nanoscale surficial amorphous films in Bi2O3-doped ZnO are briefly reviewed. The experimental results are modeled with two approaches. A pressure-balance model with the volumetric free energy being the dominant temperature-dependent interaction extended from Clarke's intergranular films model is proposed and numerically evaluated. This quantitative model predicts thicknesses versus temperature behavior for subeutectic films consistent with experimental results. Alternatively, the sequence of adsorption and wetting events as a function of temperature and composition is interpreted as a case of combined surface prewetting and premelting in a two-component system with a bulk eutectic reaction as a generalization of Cahn's critical point wetting model. In this second approach that better represents the through-thickness gradients, diffuse-interface formulation is proposed and analyzed for assessing surficial film stability as well as associated drying and complete wetting transitions. The observation made for Bi2O3 on ZnO can be represented by one of the possible surface prewetting/premelting phase diagrams.
Co-reporter:
Nature Materials 2003 2(11) pp:
Publication Date(Web):
DOI:10.1038/nmat1009b
The 'reproduced' experiments by Ravet et al.1 have, on closer reading, clear differences in procedure from ours2. They do not observe increased conductivity on attempted doping, and therefore attribute our results2 to a variety of conductive secondary-phase artefacts.
Co-reporter:A.N Soukhojak, H Wang, G.W Farrey, Y.-M Chiang
Journal of Physics and Chemistry of Solids 2000 Volume 61(Issue 2) pp:301-304
Publication Date(Web):February 2000
DOI:10.1016/S0022-3697(99)00297-8
Na1/2Bi1/2TiO3 (NBT) doped with BaTiO3 (BT) has recently shown promising piezoelectric properties in single crystal form. The piezoelectric properties appear to be highly dependent on BT concentration, with compositions close to the morphotropic phase boundary (∼6% BT) having the highest piezoelectric coefficients. Previous studies have resulted in conflicting conclusions regarding the presence and nature of the superlattice in NBT. Using HREM and hot-stage TEM electron diffraction, we show that flux-grown single crystals of compositions (1−x)NBT–xBT with x<0.08 exhibit superlattice reflections that are present from room temperature up to 500°C, above which temperature they reversibly vanish. The reflections are consistent with a superstructure due to single-axis in-phase octahedral tilt (a0a0c+). The dependence of the superlattice reflection intensity on temperature and BT content as well as possible mechanisms of superlattice formation are discussed.
Co-reporter:Dorthe B. Ravnsbæk; Kai Xiang; Wenting Xing; Olaf J. Borkiewicz; Kamila M. Wiaderek; Paul Gionet; Karena W. Chapman; Peter J. Chupas; Ming Tang
Nano Letter () pp:
Publication Date(Web):March 1, 2016
DOI:10.1021/acs.nanolett.5b05146
Alkali ion intercalation compounds used as battery electrodes often exhibit first-order phase transitions during electrochemical cycling, accompanied by significant transformation strains. Despite ∼30 years of research into the behavior of such compounds, the relationship between transformation strain and electrode performance, especially the rate at which working ions (e.g., Li) can be intercalated and deintercalated, is still absent. In this work, we use the LiMnyFe1–yPO4 system for a systematic study, and measure using operando synchrotron radiation powder X-ray diffraction (SR-PXD) the dynamic strain behavior as a function of the Mn content (y) in powders of ∼50 nm average diameter. The dynamically produced strain deviates significantly from what is expected from the equilibrium phase diagrams and demonstrates metastability but nonetheless spans a wide range from 0 to 8 vol % with y. For the first time, we show that the discharge capacity at high C-rates (20–50C rate) varies in inverse proportion to the transformation strain, implying that engineering electrode materials for reduced strain can be used to maximize the power capability of batteries.
Co-reporter:Zheng Li, Kyle C. Smith, Yajie Dong, Nir Baram, Frank Y. Fan, Jing Xie, Pimpa Limthongkul, W. Craig Carter and Yet-Ming Chiang
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 38) pp:NaN15839-15839
Publication Date(Web):2013/08/16
DOI:10.1039/C3CP53428F
An aqueous Li-ion flow cell using suspension-based flow electrodes based on the LiTi2(PO4)3–LiFePO4 couple is demonstrated. Unlike conventional flow batteries, the semi-solid approach utilizes fluid electrodes that are electronically conductive. A model of simultaneous advection and electrochemical transport is developed and used to separate flow-induced losses from those due to underlying side reactions. The importance of plug flow to achieving high energy efficiency in flow batteries utilizing highly non-Newtonian flow electrodes is emphasized.
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