Co-reporter:Shou-Hang Bo, Xin Li, Alexandra J. Toumar, and Gerbrand Ceder
Chemistry of Materials 2016 Volume 28(Issue 5) pp:1419
Publication Date(Web):February 1, 2016
DOI:10.1021/acs.chemmater.5b04626
O3 layered sodium transition metal oxides (i.e., NaMO2, M = Ti, V, Cr, Mn, Fe, Co, Ni) are a promising class of cathode materials for Na-ion battery applications. These materials, however, all suffer from severe capacity decay when the extraction of Na exceeds certain capacity limits. Understanding the causes of this capacity decay is critical to unlocking the potential of these materials for battery applications. In this work, we investigate the structural origins of capacity decay for one of the compounds in this class, NaCrO2. The (de)sodiation processes of NaCrO2 were studied both in situ and ex situ through X-ray and electron diffraction measurements. We demonstrate that NaxCrO2 (0 < x < 1) remains in the layered structural framework without Cr migration up to a composition of Na0.4CrO2. Further removal of Na beyond this composition triggers a layered-to-rock-salt transformation, which converts P′3-Na0.4CrO2 into the rock-salt CrO2 phase. This structural transformation proceeds via the formation of an intermediate O3 NaδCrO2 phase that contains Cr in both Na and Cr slabs and shares very similar lattice dimensions with those of rock-salt CrO2. It is intriguing to note that intercalation of alkaline ions (i.e., Na+ and Li+) into the rock-salt CrO2 and O3 NaδCrO2 structures is actually possible, albeit in a limited amount (∼0.2 per formula unit). When these results were analyzed under the context of electrochemistry data, it was apparent that preventing the layered-to-rock-salt transformation is crucial to improve the cyclability of NaCrO2. Possible strategies for mitigating this detrimental phase transition are proposed.
Co-reporter:Hong Zhu, Geoffroy Hautier, Umut Aydemir, Zachary M. Gibbs, Guodong Li, Saurabh Bajaj, Jan-Hendrik Pöhls, Danny Broberg, Wei Chen, Anubhav Jain, Mary Anne White, Mark Asta, G. Jeffrey Snyder, Kristin Persson and Gerbrand Ceder
Journal of Materials Chemistry A 2016 vol. 4(Issue 19) pp:4331-4331
Publication Date(Web):27 Apr 2016
DOI:10.1039/C6TC90077A
Correction for ‘Computational and experimental investigation of TmAgTe2 and XYZ2 compounds, a new group of thermoelectric materials identified by first-principles high-throughput screening’ by Hong Zhu et al., J. Mater. Chem. C, 2015, 3, 10554–10565.
Co-reporter:Jae Chul Kim, Dong-Hwa Seo and Gerbrand Ceder
Energy & Environmental Science 2015 vol. 8(Issue 6) pp:1790-1798
Publication Date(Web):13 May 2015
DOI:10.1039/C5EE00930H
Simple borates are attractive cathodes for lithium-ion batteries due to two main reasons: covalently bonded anions provide operating stability through suppressed oxygen loss, and the borate group (BO3) possesses the highest theoretical specific capacity for one-electron polyanion systems. In this work, we demonstrate an electrochemically superior lithium borate (LiMn0.5Fe0.4Mg0.1BO3) that delivers a near theoretical capacity (98%) of 201 mA h g−1 at C/50, an improved rate capability of 120 mA h g−1 at 1 C, and good capacity retention. Using ab initio modeling, the superior Li intercalation activity is explained by both stabilization of the delithiated state and increased topological cation disorder, which counter-intuitively facilitates Li transport. Our results indicate that through engineering of defect chemistry, the basic mechanism can be modified from one-dimensional to three-dimensional conduction, thereby improving kinetics. Combined with the inherent stability of the borate group, the enhanced electrochemical properties should reinvigorate search in borate chemistry for new safe and high-energy cathode materials.
Co-reporter:Di Wu, Xin Li, Bo Xu, Nancy Twu, Lei Liu and Gerbrand Ceder
Energy & Environmental Science 2015 vol. 8(Issue 1) pp:195-202
Publication Date(Web):28 Oct 2014
DOI:10.1039/C4EE03045A
We report on layered NaTiO2 as a potential anode material for Na-ion batteries. The material is prepared from only earth-abundant elements, delivers 152 mA h g−1 of reversible capacity at C/10 rate, shows excellent cyclability with capacity retention over 98% after 60 cycles, and high rate capability. Furthermore, in situ X-ray diffraction analysis reveals a reversible O3–O′3 phase transition, including an unusual lattice parameter variation coupled to complicated Na vacancy orderings in a series of 2nd order phase transitions.
Co-reporter:Jae Chul Kim;Dong-Hwa Seo;Hailong Chen;Gerbr Ceder
Advanced Energy Materials 2015 Volume 5( Issue 8) pp:
Publication Date(Web):
DOI:10.1002/aenm.201401916
In materials containing 1D lithium diffusion channels, cation disorder can strongly affect lithium intercalation processes. This work presents a model to explain the unusual transport properties of monoclinic LiMnBO3, a material determined by scanning electron microscopy and synchrotron X-ray diffraction to contain a wide particle size distribution and Mn/Li antisite disorder. First-principles calculations indicate that Mn occupying Li sites obstruct the 1D lithium diffusion channel along the [001] direction. While channel blockage by the antisites significantly lowers Li mobility in large particles, Li kinetics in small particles and particle surfaces are found to be less sensitive to the presence of antisite disorder. Thus, in an electrode containing a large particle size distribution, smaller particles have higher Li mobility, and the measured Li diffusivity as determined by potentiostatic intermittent titration test varies as a function of particle size. The Li capacity in monoclinic LiMnBO3 is kinetically controlled by the fraction of large particles with antisite disorder, but is not intrinsically limited. These results strongly suggest that particle nanosizing will significantly enhance the electrochemical performance of LiMnBO3.
Co-reporter:Lei Liu;Xin Li;Shou-Hang Bo;Yan Wang;Hailong Chen;Nancy Twu;Di Wu;Gerbr Ceder
Advanced Energy Materials 2015 Volume 5( Issue 22) pp:
Publication Date(Web):
DOI:10.1002/aenm.201500944
Co-reporter:Gopalakrishnan Sai Gautam, Pieremanuele Canepa, Aziz Abdellahi, Alexander Urban, Rahul Malik, and Gerbrand Ceder
Chemistry of Materials 2015 Volume 27(Issue 10) pp:3733
Publication Date(Web):April 28, 2015
DOI:10.1021/acs.chemmater.5b00957
We have investigated Mg intercalation into orthorhombic V2O5, one of only three cathodes known to reversibly intercalate Mg ions. By calculating the ground-state MgxV2O5 configurations and by developing a cluster expansion for the configurational disorder in δ-V2O5, a full temperature–composition phase diagram is derived. Our calculations indicate an equilibrium phase-separating behavior between fully demagnesiated α-V2O5 and fully magnesiated δ-V2O5, but also motivate the existence of potentially metastable solid solution transformation paths in both phases. We find significantly better mobility for Mg in the δ polymorph, suggesting that better performance can be achieved by cycling Mg in the δ phase.
Co-reporter:Ziqin Rong, Rahul Malik, Pieremanuele Canepa, Gopalakrishnan Sai Gautam, Miao Liu, Anubhav Jain, Kristin Persson, and Gerbrand Ceder
Chemistry of Materials 2015 Volume 27(Issue 17) pp:6016
Publication Date(Web):August 5, 2015
DOI:10.1021/acs.chemmater.5b02342
The diffusion of ions in solid materials plays an important role in many aspects of materials science such as the geological evolution of minerals, materials synthesis, and in device performance across several technologies. For example, the realization of multivalent (MV) batteries, which offer a realistic route to superseding the electrochemical performance of Li-ion batteries, hinges on the discovery of host materials that possess adequate mobility of the MV intercalant to support reasonable charge and discharge times. This has proven especially challenging, motivating the current investigation of ion mobility (Li+, Mg2+, Zn2+, Ca2+, and Al3+) in spinel Mn2O4, olivine FePO4, layered NiO2, and orthorhombic δ-V2O5. In this study, we not only quantitatively assess these structures as candidate cathode materials, but also isolate the chemical and structural descriptors that govern MV diffusion. Our finding that matching the intercalant site preference to the diffusion path topology of the host structure controls mobility more than any other factor leads to practical and implementable guidelines to find fast-diffusing MV ion conductors.
Co-reporter:Ian L. Matts, Stephen Dacek, Tomasz K. Pietrzak, Rahul Malik, and Gerbrand Ceder
Chemistry of Materials 2015 Volume 27(Issue 17) pp:6008
Publication Date(Web):August 7, 2015
DOI:10.1021/acs.chemmater.5b02299
Fluorophosphate cathodes are currently one of the most promising polyanionic sodium-ion battery cathodes and exhibit specific energies not far below oxide cathodes. To further improve fluorophosphate cathodes, their capacity must be increased, which might be possible since some sodium (Na) remains unextracted in these cathodes during cycling. In this study we attempt to answer the question of what specific mechanism limits fluorophosphate cathode capacity, which could stem from either redox-limiting or site-limiting behavior. This paper reports the synthesis, electrochemical characterization, and computational examination of Na3GaV(PO4)2F3. This test system, which was designed explicitly for uncovering the limiting factors in these structures, exhibits reversible insertion of Na+ and redox activity for V2+ through V5+ during electrochemical cycling, indicating that fluorophosphate cathodes are not fundamentally redox-limited and must be site-limited. First-principles calculations indicate that large diffusion barriers at high sodiations impose a kinetic limit on Na+ insertion in fluorophosphate cathodes, but further investigation is needed to determine capacity limits on Na+ extraction. From our combined results we also propose possible routes to improve future fluorophosphate cathodes.
Co-reporter:Pieremanuele Canepa, Gopalakrishnan Sai Gautam, Rahul Malik, Saivenkataraman Jayaraman, Ziqin Rong, Kevin R. Zavadil, Kristin Persson, and Gerbrand Ceder
Chemistry of Materials 2015 Volume 27(Issue 9) pp:3317
Publication Date(Web):April 8, 2015
DOI:10.1021/acs.chemmater.5b00389
Multivalent (MV) battery architectures based on pairing a Mg metal anode with a high-voltage (∼3 V) intercalation cathode offer a realistic design pathway toward significantly surpassing the energy storage performance of traditional Li-ion-based batteries, but there are currently only few electrolyte systems that support reversible Mg deposition. Using both static first-principles calculations and ab initio molecular dynamics, we perform a comprehensive adsorption study of several salt and solvent species at the interface of Mg metal with an electrolyte of Mg2+ and Cl– dissolved in liquid tetrahydrofuran (THF). Our findings not only provide a picture of the stable species at the interface but also explain how this system can support reversible Mg deposition, and as such, we provide insights in how to design other electrolytes for Mg plating and stripping. The active depositing species are identified to be (MgCl)+ monomers coordinated by THF, which exhibit preferential adsorption on Mg compared to possible passivating species (such as THF solvent or neutral MgCl2 complexes). Upon deposition, the energy to desolvate these adsorbed complexes and facilitate charge transfer is shown to be small (∼61–46.2 kJ mol–1 to remove three THF from the strongest adsorbing complex), and the stable orientations of the adsorbed but desolvated (MgCl)+ complexes appear to be favorable for charge transfer. Finally, observations of Mg–Cl dissociation at the Mg surface at very low THF coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode may occur upon plating. In the stripping process, this is beneficial by further facilitating the Mg removal reaction.
Co-reporter:Hong Zhu, Geoffroy Hautier, Umut Aydemir, Zachary M. Gibbs, Guodong Li, Saurabh Bajaj, Jan-Hendrik Pöhls, Danny Broberg, Wei Chen, Anubhav Jain, Mary Anne White, Mark Asta, G. Jeffrey Snyder, Kristin Persson and Gerbrand Ceder
Journal of Materials Chemistry A 2015 vol. 3(Issue 40) pp:10554-10565
Publication Date(Web):13 Aug 2015
DOI:10.1039/C5TC01440A
A new group of thermoelectric materials, trigonal and tetragonal XYZ2 (X, Y: rare earth or transition metals, Z: group VI elements), the prototype of which is TmAgTe2, is identified by means of high-throughput computational screening and experiment. Based on density functional theory calculations, this group of materials is predicted to attain high zT (i.e. ∼1.8 for p-type trigonal TmAgTe2 at 600 K). Among approximately 500 chemical variants of XYZ2 explored, many candidates with good stability and favorable electronic band structures (with high band degeneracy leading to high power factor) are presented. Trigonal TmAgTe2 has been synthesized and exhibits an extremely low measured thermal conductivity of 0.2–0.3 W m−1 K−1 for T > 600 K. The zT value achieved thus far for p-type trigonal TmAgTe2 is approximately 0.35, and is limited by a low hole concentration (∼1017 cm−3 at room temperature). Defect calculations indicate that TmAg antisite defects are very likely to form and act as hole killers. Further defect engineering to reduce such XY antisites is deemed important to optimize the zT value of the p-type TmAgTe2.
Co-reporter:Anubhav Jain, Geoffroy Hautier, Shyue Ping Ong, Stephen Dacek and Gerbrand Ceder
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 8) pp:5942-5953
Publication Date(Web):30 Jan 2015
DOI:10.1039/C5CP00250H
High voltage and high thermal safety are desirable characteristics of cathode materials, but difficult to achieve simultaneously. This work uses high-throughput density functional theory computations to evaluate the link between voltage and safety (as estimated by thermodynamic O2 release temperatures) for over 1400 cathode materials. Our study indicates that a strong inverse relationship exists between voltage and safety: just over half the variance in O2 release temperature can be explained by voltage alone. We examine the effect of polyanion group, redox couple, and ratio of oxygen to counter-cation on both voltage and safety. As expected, our data demonstrates that polyanion groups improve safety when comparing compounds with similar voltages. However, a counterintuitive result of our study is that polyanion groups produce either no benefit or reduce safety when comparing compounds with the same redox couple. Using our data set, we tabulate voltages and oxidation potentials for over 105 combinations of redox couple/anion, which can be used towards the design and rationalization of new cathode materials. Overall, only a few compounds in our study, representing limited redox couple/polyanion combinations, exhibit both high voltage and high safety. We discuss these compounds in more detail as well as the opportunities for designing safe, high-voltage cathodes.
Co-reporter:Shyue Ping Ong, Shreyas Cholia, Anubhav Jain, Miriam Brafman, Dan Gunter, Gerbrand Ceder, Kristin A. Persson
Computational Materials Science 2015 Volume 97() pp:209-215
Publication Date(Web):1 February 2015
DOI:10.1016/j.commatsci.2014.10.037
In this paper, we describe the Materials Application Programming Interface (API), a simple, flexible and efficient interface to programmatically query and interact with the Materials Project database based on the REpresentational State Transfer (REST) pattern for the web. Since its creation in Aug 2012, the Materials API has been the Materials Project’s de facto platform for data access, supporting not only the Materials Project’s many collaborative efforts but also enabling new applications and analyses. We will highlight some of these analyses enabled by the Materials API, particularly those requiring consolidation of data on a large number of materials, such as data mining of structural and property trends, and generation of phase diagrams. We will conclude with a discussion of the role of the API in building a community that is developing novel applications and analyses based on Materials Project data.
Co-reporter:Alexer Urban;Jinhyuk Lee ;Gerbr Ceder
Advanced Energy Materials 2014 Volume 4( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/aenm.201400478
A unifying theory is presented to explain the lithium exchange capacity of rocksalt-like structures with any degree of cation ordering, and how lithium percolation properties can be used as a guideline for the development of novel high-capacity electrode materials is demonstrated. The lithium percolation properties of the three most common lithium metal oxide phases, the layered α-NaFeO2 structure, the spinel-like LT-LiCoO2 structure, and the γ-LiFeO2 structure, are demonstrated and a strong dependence of the percolation thresholds on the cation ordering and the lithium content is observed. The poor performance of γ-LiFeO2-type structures is explained by their lack of percolation of good Li migration channels. The spinel-like structure exhibits excellent percolation properties that are robust with respect to off-stoichiometry and some amount of cation disorder. The layered structure is unique, as it possesses two different types of lithium diffusion channels, one of which is, however, strongly dependent on the lattice parameters, and therefore very sensitive to disorder. In general it is found that a critical Li-excess concentration exists at which Li percolation occurs, although the amount of Li excess needed depends on the partial cation ordering. In fully cation-disordered materials, macroscopic lithium diffusion is enabled by ≈10% excess lithium.
Co-reporter:ShinYoung Kang, Yifei Mo, Shyue Ping Ong, and Gerbrand Ceder
Nano Letters 2014 Volume 14(Issue 2) pp:1016-1020
Publication Date(Web):January 13, 2014
DOI:10.1021/nl404557w
The thermodynamic stability of materials can depend on particle size due to the competition between surface and bulk energy. In this Letter, we show that, while sodium peroxide (Na2O2) is the stable bulk phase of Na in an oxygen environment at standard conditions, sodium superoxide (NaO2) is considerably more stable at the nanoscale. As a consequence, the superoxide requires a much lower nucleation energy than the peroxide, explaining why it can be observed as the discharge product in some Na–O2 batteries. As the superoxide can be recharged (decomposed) at much lower overpotentials than the peroxide, these findings are important to create highly reversible Na–O2 batteries. We derive the specific electrochemical conditions to nucleate and retain Na-superoxides and comment on the importance of considering the nanophase thermodynamics when optimizing an electrochemical system.
Co-reporter:Jae Chul Kim, Xin Li, Charles J. Moore, Shou-Hang Bo, Peter G. Khalifah, Clare P. Grey, and Gerbrand Ceder
Chemistry of Materials 2014 Volume 26(Issue 14) pp:4200
Publication Date(Web):June 30, 2014
DOI:10.1021/cm5014174
The stability of the charged state of monoclinic LiMnBO3 has been analyzed to better understand its electrochemical cycling behavior in this work. First-principles calculations indicate that delithiated monoclinic Li1–xMnBO3 becomes unstable for x ≥ 0.625. Results obtained from ex-situ X-ray diffraction on charged electrodes and chemically oxidized powder confirm the phase decomposition of the LiMnBO3 phase when a significant amount of Li is extracted. Energy-dispersive X-ray spectroscopy and X-ray diffraction analysis also reveal Mn dissolution from the cycled LiMnBO3 cathodes and chemically delithiated LiMnBO3 specimen. Based on these results, we consider the cycling performance of monoclinic LiMnBO3 to be primarily limited by its charged state instability. To overcome this limitation, we partially substituted Mn with Mg to maintain structural integrity of the phase and reduce capacity fading over multiple cycles.
Co-reporter:Yuechuan Lei, Xin Li, Lei Liu, and Gerbrand Ceder
Chemistry of Materials 2014 Volume 26(Issue 18) pp:5288-5296
Publication Date(Web):September 3, 2014
DOI:10.1021/cm5021788
Layered Na–metal oxides can form in different crystal structures, each with different electrochemical behavior. As a prototype system to better understand how each phase can be formed, we present the conditions under which different layered phases of NaxCoO2 can be stabilized in solid-state synthesis. Using a novel combination of ex situ XRD on as-synthesized samples, with in situ XRD to monitor the relation between Na content and lattice parameters, we are able to construct a phase diagram of NaxCoO2 between 450 to 750 °C in air and for Na:Co sample ratios ranging from 0.60 to 1.05. Four single phase domains of O3, O′3, P′3, and P2 are revealed based on the XRD analysis. In contrast to previous reports it is found that pure O3, O′3 and P′3 phase can only form at a fixed stoichiometry of x = 1.00, 0.83, and 0.67, respectively, while the P2 phase forms in a slightly larger composition range from 0.68 to 0.76. Galvanostatic charging of O3–Na1.00CoO2 shows several flat and sloping regions on the voltage profile, which follows the sequence of O3–O′3–P′3–P3–P′3, with increasing interslab distances. Our results indicate that the electrochemically important P2 structure is likely stabilized by entropy.
Co-reporter:Aziz Abdellahi, Oncu Akyildiz, Rahul Malik, Katsuyo Thornton and Gerbrand Ceder
Journal of Materials Chemistry A 2014 vol. 2(Issue 37) pp:15437-15447
Publication Date(Web):25 Jul 2014
DOI:10.1039/C4TA02935F
We gain new insights into the equilibrium properties and potential two-phase lithiation mechanisms in LiFePO4 nano-particles by conducting a first-principles investigation of the anisotropic chemical interfacial energy landscape in LiFePO4. The chemical interfacial energy per unit area along the ac plane is found to be remarkably low (7 mJ m−2) with respect to the bc (115 mJ m−2) and ab (95 mJ m−2) chemical interfacial energies. Because chemical interfacial energy and coherency strain energy have different anisotropies, the thermodynamically stable interface orientation is shown to depend both on the particle size and on the particle morphology. In particular, ac interfaces are favored for isotropic particles below 40 nm. This indicates that, if experimentally-relevant nano-particles were to (de)lithiate under a thermodynamic two-phase mechanism, the resulting front would be orientated along the ac plane, and not along the bc plane as is assumed in most lithiation models in the literature.
Co-reporter:Xin Li, Di Wu, Yong-Ning Zhou, Lei Liu, Xiao-Qing Yang, Gerbrand Ceder
Electrochemistry Communications 2014 Volume 49() pp:51-54
Publication Date(Web):December 2014
DOI:10.1016/j.elecom.2014.10.003
•We report a new layered quaternary Na(Mn0.25Fe0.25Co0.25Ni0.25)O2 compound with O3 oxygen stacking.•It delivers 180 mAh/g initial discharge capacity and 578 Wh/kg specific energy density with good cycling capability at high cutoff voltage.•In situ X-ray diffraction (XRD) shows a reversible structure evolution of O3-P3-O3′-O3″ upon Na deintercalation.•The excellent capacity and cycling performance at high cutoff voltage makes it an important model system for studying the general issue of capacity fading in layered Na cathode compounds.We report a new layered Na(Mn0.25Fe0.25Co0.25Ni0.25)O2 compound with O3 oxygen stacking. It delivers 180 mAh/g initial discharge capacity and 578 Wh/kg specific energy density with good cycling capability at high cutoff voltage. In situ X-ray diffraction (XRD) shows a reversible structure evolution of O3-P3-O3′-O3″ upon Na de-intercalation. The excellent capacity and cycling performance at high cutoff voltage make it an important model system for studying the general issue of capacity fading in layered Na cathode compounds.
Co-reporter:Plousia Vassilaras, Alexandra J. Toumar, Gerbrand Ceder
Electrochemistry Communications 2014 Volume 38() pp:79-81
Publication Date(Web):January 2014
DOI:10.1016/j.elecom.2013.11.015
•Synthesis and characterizations of layered NaNi1/3Co1/3Fe1/3O2.•NaNi1/3Co1/3Fe1/3O2is one of the highest power layered oxide cathode materials.•First principles calculations determine the order of transition metal oxidation.•Calculated lattice parameters and average voltages agree with the experimental.NaNi1/3Fe1/3Co1/3O2 is synthesized by solid-state methods and investigated as a positive electrode material for sodium ion batteries. Galvanostatic cycling of NaNi1/3Fe1/3Co1/3O2 between 2.0 and 4.2 V provides ~ 165 mAh/g of reversible capacity at C/20. This material also demonstrates great rate-capability and is able to de-intercalate 80 mAh/g even at 30C. First principles calculations are used to determine the order of transition metal oxidation within the system and provide lattice parameters with close proximity to the experimental.
Co-reporter:Jinhyuk Lee;Alexander Urban;Xin Li;Dong Su;Geoffroy Hautier
Science 2014 Volume 343(Issue 6170) pp:519-522
Publication Date(Web):31 Jan 2014
DOI:10.1126/science.1246432
Disorderly Flow
Lithium batteries are becoming ever more important in society. While their application used to be confined to portable electronics, they are now becoming the enabling technology for electric vehicles and grid storage for renewables. Generally, the flow of lithium ions into and out of battery electrodes is thought to require ordered materials. Lee et al. (p. 519, published online 9 January) used a combination of experimental work and computations to identify disordered electrode materials with high Li diffusion. The improved energy density properties could be attributed to compositions with excess lithium beyond the stoichiometric limit, leading to intermixing between the lithium and transition metal sublattices and the formation of a percolation network providing specific lithium transport pathways.
Co-reporter:Shyue Ping Ong, Yifei Mo, William Davidson Richards, Lincoln Miara, Hyo Sug Lee and Gerbrand Ceder
Energy & Environmental Science 2013 vol. 6(Issue 1) pp:148-156
Publication Date(Web):02 Oct 2012
DOI:10.1039/C2EE23355J
We present an investigation of the phase stability, electrochemical stability and Li+ conductivity of the Li10±1MP2X12 (M = Ge, Si, Sn, Al or P, and X = O, S or Se) family of superionic conductors using first principles calculations. The Li10GeP2S12 (LGPS) superionic conductor has the highest Li+ conductivity reported to date, with excellent electrochemical performance demonstrated in a Li-ion rechargeable battery. Our results show that isovalent cation substitutions of Ge4+ have a small effect on the relevant intrinsic properties, with Li10SiP2S12 and Li10SnP2S12 having similar phase stability, electrochemical stability and Li+ conductivity as LGPS. Aliovalent cation substitutions (M = Al or P) with compensating changes in the Li+ concentration also have a small effect on the Li+ conductivity in this structure. Anion substitutions, however, have a much larger effect on these properties. The oxygen-substituted Li10MP2O12 compounds are predicted not to be stable (with equilibrium decomposition energies >90 meV per atom) and have much lower Li+ conductivities than their sulfide counterparts. The selenium-substituted Li10MP2Se12 compounds, on the other hand, show a marginal improvement in conductivity, but at the expense of reduced electrochemical stability. We also studied the effect of lattice parameter changes on the Li+ conductivity and found the same asymmetry in behavior between increases and decreases in the lattice parameters, i.e., decreases in the lattice parameters lower the Li+ conductivity significantly, while increases in the lattice parameters increase the Li+ conductivity only marginally. Based on these results, we conclude that the size of the S2− is near optimal for Li+ conduction in this structural framework.
Co-reporter:Geoffroy Hautier, Anubhav Jain, Tim Mueller, Charles Moore, Shyue Ping Ong, and Gerbrand Ceder
Chemistry of Materials 2013 Volume 25(Issue 10) pp:2064
Publication Date(Web):April 24, 2013
DOI:10.1021/cm400199j
Finding new polyanionic Li-ion battery cathodes with higher capacities than LiFePO4 is currently a major target of battery research. One approach toward this goal is to develop materials capable of exchanging more than one Li atom per transition metal. However, constraints on operating voltage due to organic electrolyte stability as well as cathode structural stability have made this target difficult to reach. More specifically, it is very challenging to develop a phosphate-based cathode in which a single element provides +2 to +4 redox activity in a reasonable voltage window: Either the voltage for the +2/+3 couple is too low (e.g., V) or the voltage for the +3/+4 couple is too high (e.g., Fe). This makes several appealing structural frameworks such as tavorites difficult to use as practical two-electron systems. Here, we propose a voltage design strategy based on the mixing of different transition metals in crystal structures known to be able to accommodate lithium in insertion and delithiation. By mixing a metal active on the +2/+3 couple (e.g., Fe) with an element active on the +3/+5 or +3/+6 couples (e.g., V or Mo), we show that high-capacity multielectron cathodes can be designed in an adequate voltage window. We illustrate our mixing strategy on LiMP2O7 pyrophosphates as well as LiMPO4(OH) and LiM(PO4)F tavorites, and we use density functional theory (DFT) computations to evaluate the theoretical capacity, voltage profile, and stability of the compounds proposed by our design rules. From this analysis, we identify several new compounds of potential interest as cathode materials.Keywords: ab initio; cathode; DFT; Li-ion battery; multielectron cathode; phosphates; pyrophosphate; tavorite;
Co-reporter:Hailong Chen, Qing Hao, Olivera Zivkovic, Geoffroy Hautier, Lin-Shu Du, Yuanzhi Tang, Yan-Yan Hu, Xiaohua Ma, Clare P. Grey, and Gerbrand Ceder
Chemistry of Materials 2013 Volume 25(Issue 14) pp:2777
Publication Date(Web):July 11, 2013
DOI:10.1021/cm400805q
Na-ion batteries represent an effective energy storage technology with slightly lower energy and power densities but potentially lower material costs than Li-ion batteries. Here, we report a new polyanionic intercalation cathode material of an unusual chemical class: sidorenkite (Na3MnPO4CO3). This carbonophosphate compound shows a high discharge capacity (∼125 mAh/g) and specific energy (374 Wh/kg). In situ X-ray diffraction measurement suggests that sidorenkite undergoes a solid solution type reversible topotactic structural evolution upon electrochemical cycling. Ex situ solid state NMR investigation reveals that more than one Na per formula unit can be deintercalated from the structure, indicating a rarely observed two-electron intercalation reaction in which both Mn2+/Mn3+ and Mn3+/Mn4+ redox couples are electrochemically active.Keywords: 23Na NMR; batteries; carbonophosphates; cathode; hydrothermal; intercalation; MAS NMR; Na-ion batteries; phosphocarbonates;
Co-reporter:ShinYoung Kang, Yifei Mo, Shyue Ping Ong, and Gerbrand Ceder
Chemistry of Materials 2013 Volume 25(Issue 16) pp:3328
Publication Date(Web):July 31, 2013
DOI:10.1021/cm401720n
Li–air is a novel battery technology with the potential to offer very high specific energy, but which currently suffers from a large charging overpotential and low power density. In this work, we use ab initio calculations to demonstrate that a facile mechanism for recharging Li2O2 exists. Rather than the direct decomposition pathway of Li2O2 into Li and O2 suggested by equilibrium thermodynamics, we find an alternative reaction pathway based on topotactic delithiation of Li2O2 to form off-stoichiometric Li2–xO2 compounds akin to the charging mechanism in typical Li-ion intercalation electrodes. The low formation energy of bulk Li2–xO2 phases confirms that this topotactic delithiation mechanism is rendered accessible at relatively small overpotentials of ∼0.3–0.4 V and is likely to be kinetically favored over Li2O2 decomposition. Our findings indicate that at the Li2O2 particle level there are no obstacles to increase the current density, and point to an exciting opportunity to create fast charging Li–air systems.Keywords: charging mechanism; lithium superoxide (LiO2); Li−air batteries; oxygen evolution reaction;
Co-reporter:Wenhao Sun, Gerbrand Ceder
Surface Science 2013 Volume 617() pp:53-59
Publication Date(Web):November 2013
DOI:10.1016/j.susc.2013.05.016
•We present an approach for efficient high-throughput DFT surface calculations.•Algorithm to create surface slabs of any orientation from any crystal structure.•DFT parameters important for efficient and accurate surface modeling is discussed.•Bulk energy calculated from surface oriented bulk converges surface energy rapidly.The supercell slab is the structural model used in first-principles simulations to determine thermodynamic, kinetic, and electronic properties of surfaces and interfaces. We present a general algorithm to reorient bulk unit cells using basis and covariant transformations — the first step for constructing surface slabs of any Miller index from bulk unit cells of any Bravais lattice. We further review and discuss subtleties of surface slab creation relevant for performing efficient and accurate calculations of surface properties. We also demonstrate that the nonconvergence of surface energy with respect to slab thickness can be mitigated if the bulk reference energy is calculated from a surface-oriented bulk unit cell, which eliminates Brillouin zone integration errors between the slab and the bulk. Using Pt(111) and Si(111) surfaces as examples, this technique converges the surface energy with respect to slab thickness requiring only one bulk and one relatively thin slab calculation, with moderate k-point densities. This process is about an order of magnitude more efficient than popular surface energy convergence techniques involving multiple slab calculations.
Co-reporter:Shyue Ping Ong, William Davidson Richards, Anubhav Jain, Geoffroy Hautier, Michael Kocher, Shreyas Cholia, Dan Gunter, Vincent L. Chevrier, Kristin A. Persson, Gerbrand Ceder
Computational Materials Science 2013 Volume 68() pp:314-319
Publication Date(Web):February 2013
DOI:10.1016/j.commatsci.2012.10.028
We present the Python Materials Genomics (pymatgen) library, a robust, open-source Python library for materials analysis. A key enabler in high-throughput computational materials science efforts is a robust set of software tools to perform initial setup for the calculations (e.g., generation of structures and necessary input files) and post-calculation analysis to derive useful material properties from raw calculated data. The pymatgen library aims to meet these needs by (1) defining core Python objects for materials data representation, (2) providing a well-tested set of structure and thermodynamic analyses relevant to many applications, and (3) establishing an open platform for researchers to collaboratively develop sophisticated analyses of materials data obtained both from first principles calculations and experiments. The pymatgen library also provides convenient tools to obtain useful materials data via the Materials Project’s REpresentational State Transfer (REST) Application Programming Interface (API). As an example, using pymatgen’s interface to the Materials Project’s RESTful API and phasediagram package, we demonstrate how the phase and electrochemical stability of a recently synthesized material, Li4SnS4, can be analyzed using a minimum of computing resources. We find that Li4SnS4 is a stable phase in the Li–Sn–S phase diagram (consistent with the fact that it can be synthesized), but the narrow range of lithium chemical potentials for which it is predicted to be stable would suggest that it is not intrinsically stable against typical electrodes used in lithium-ion batteries.Highlights► Python Materials Genomics (pymatgen) is a robust, open-source library for materials analysis. ► Well-tested set of structure and thermodynamic analyses relevant to many applications. ► Open platform for researchers to collaboratively develop sophisticated analyses of materials. ► Convenient tools to obtain useful materials data via the Materials Project’s RESTful API. ► Evaluated phase and electrochemical stability of recently synthesized material Li4SnS4.
Co-reporter:Yabi Wu and Gerbrand Ceder
The Journal of Physical Chemistry C 2013 Volume 117(Issue 47) pp:24710-24715
Publication Date(Web):October 28, 2013
DOI:10.1021/jp407911g
In this paper, we propose the new Ta3N5:Ti3O3N2 solid solution as a promising water-splitting photocatalyst. Using first principles computations, we study the phase stability, band gap, and band edge positions of the solid solution. The results suggest that the solid solution can likely be synthesized, and has a band gap lower than both its end members. The minimal band gap may be around 2.0 eV for a composition around 50%:50%, indicating that good efficiency under solar illumination may be achieved. In addition, the CB and VB of the solid solution are predicted to be bracketing the water redox levels, so the photocatalysis process is energetically favorable and bias voltage may not be required.
Co-reporter:Sung-Wook Kim;Dong-Hwa Seo;Xiaohua Ma;Gerbr Ceder;Kisuk Kang
Advanced Energy Materials 2012 Volume 2( Issue 7) pp:710-721
Publication Date(Web):
DOI:10.1002/aenm.201200026
Abstract
Lithium (Li)-ion batteries (LIB) have governed the current worldwide rechargeable battery market due to their outstanding energy and power capability. In particular, the LIB's role in enabling electric vehicles (EVs) has been highlighted to replace the current oil-driven vehicles in order to reduce the usage of oil resources and generation of CO2 gases. Unlike Li, sodium is one of the more abundant elements on Earth and exhibits similar chemical properties to Li, indicating that Na chemistry could be applied to a similar battery system. In the 1970s-80s, both Na-ion and Li-ion electrodes were investigated, but the higher energy density of Li-ion cells made them more applicable to small, portable electronic devices, and research efforts for rechargeable batteries have been mainly concentrated on LIB since then. Recently, research interest in Na-ion batteries (NIB) has been resurrected, driven by new applications with requirements different from those in portable electronics, and to address the concern on Li abundance. In this article, both negative and positive electrode materials in NIB are briefly reviewed. While the voltage is generally lower and the volume change upon Na removal or insertion is larger for Na-intercalation electrodes, compared to their Li equivalents, the power capability can vary depending on the crystal structures. It is concluded that cost-effective NIB can partially replace LIB, but requires further investigation and improvement.
Co-reporter:Hailong Chen ; Geoffroy Hautier
Journal of the American Chemical Society 2012 Volume 134(Issue 48) pp:19619-19627
Publication Date(Web):October 19, 2012
DOI:10.1021/ja3040834
Ab initio-based high-throughput computing and screening are now being used to search and predict new functional materials and novel compounds. However, systematic experimental validation on the predictions remains highly challenging, yet desired. Careful comparison between computational predictions and experimental results is sparse in the literature. Here we report on a systematic experimental validation on previously presented computational predictions of a novel alkali carbonophosphate family of compounds. We report the successful hydrothermal synthesis and structural characterization of multiple sodium carbonophosphates. The experimental conditions for formation of the carbonophosphates and the computational results are compared and discussed. We also demonstrate topotactic chemical de-sodiation of one of the compounds, indicating the potential use of this novel class of compounds as Li+ or Na+ insertion electrodes.
Co-reporter:Yifei Mo, Shyue Ping Ong, and Gerbrand Ceder
Chemistry of Materials 2012 Volume 24(Issue 1) pp:15
Publication Date(Web):December 9, 2011
DOI:10.1021/cm203303y
Co-reporter:Hailong Chen, Geoffroy Hautier, Anubhav Jain, Charles Moore, Byoungwoo Kang, Robert Doe, Lijun Wu, Yimei Zhu, Yuanzhi Tang, and Gerbrand Ceder
Chemistry of Materials 2012 Volume 24(Issue 11) pp:2009
Publication Date(Web):May 31, 2012
DOI:10.1021/cm203243x
The tremendous growth of Li-ion batteries into a wide variety of applications is setting new requirements in terms of cost, energy density, safety, and power density. One route toward meeting these objectives consists in finding alternative chemistries to current cathode materials. In this Article, we describe a new class of materials discovered through a novel high-throughput ab initio computational approach and which can intercalate lithium reversibly. We report on the synthesis, characterization, and electrochemical testing of this novel lithium-carbonophosphate chemistry. This work demonstrates how the novel high-throughput computing approach can identify promising chemistries for next-generation cathode materials.Keywords: ab initio; carbonophosphate; cathode; high-throughput; hydrothermal; ion-exchange; lithium battery;
Co-reporter:Sangtae Kim, Xiaohua Ma, Shyue Ping Ong and Gerbrand Ceder
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 44) pp:15571-15578
Publication Date(Web):01 Oct 2012
DOI:10.1039/C2CP43377J
To understand the difference in reversible energy storage capacity between the O3-type layered Na and Li compounds, we use first principles calculations to study and contrast the effect of two well-known destabilization mechanisms, transformation into the spinel-type structures and cation mixing due to transition metal migration. This study is performed on the layered oxides at the A0.5MO2 composition, where A = (Na, Li) and M is a 3d transition metal. We find that while all Li0.5MO2 compounds have strong driving forces and low energy kinetic paths to transform to the spinel structure, Na0.5MO2 compounds do not have thermodynamic driving forces to transform to spinel type structures. We also find that transition metal mobility is higher in Li layered compounds than in Na layered compounds because of the unusual activated state for transition metal hopping. For many compounds, migration goes along an oct–tet–oct path, but transition metal migration needs to be assisted by alkali migration into a tetrahedral site forming activated Atet–Mtet defects; substituting Na for Li in the layered structure results in increased transition metal migration barriers due to the larger size of Na+ ions. Overall, our findings indicate that Na compounds in the layered O3 structure have fundamentally different destabilization mechanisms to those of Li compounds. This distinction allows superior battery electrode performance in many Na compounds and offers optimistic perspective on finding many high energy density Na electrodes that cycle with stable high capacity.
Co-reporter:Shyue Ping Ong, Vincent L. Chevrier, Geoffroy Hautier, Anubhav Jain, Charles Moore, Sangtae Kim, Xiaohua Ma and Gerbrand Ceder
Energy & Environmental Science 2011 vol. 4(Issue 9) pp:3680-3688
Publication Date(Web):02 Aug 2011
DOI:10.1039/C1EE01782A
To evaluate the potential of Na-ion batteries, we contrast in this work the difference between Na-ion and Li-ion based intercalation chemistries in terms of three key battery properties—voltage, phase stability and diffusion barriers. The compounds investigated comprise the layered AMO2 and AMS2 structures, the olivine and maricite AMPO4 structures, and the NASICON A3V2(PO4)3 structures. The calculated Na voltages for the compounds investigated are 0.18–0.57 V lower than that of the corresponding Li voltages, in agreement with previous experimental data. We believe the observed lower voltages for Na compounds are predominantly a cathodic effect related to the much smaller energy gain from inserting Na into the host structure compared to inserting Li. We also found a relatively strong dependence of battery properties on structural features. In general, the difference between the Na and Li voltage of the same structure, ΔVNa–Li, is less negative for the maricite structures preferred by Na, and more negative for the olivine structures preferred by Li. The layered compounds have the most negative ΔVNa–Li. In terms of phase stability, we found that open structures, such as the layered and NASICON structures, that are better able to accommodate the larger Na+ ion generally have both Na and Li versions of the same compound. For the close-packed AMPO4 structures, our results show that Na generally prefers the maricite structure, while Li prefers the olivine structure, in agreement with previous experimental work. We also found surprising evidence that the barriers for Na+ migration can potentially be lower than that for Li+ migration in the layered structures. Overall, our findings indicate that Na-ion systems can be competitive with Li-ion systems.
Co-reporter:Tim Mueller, Geoffroy Hautier, Anubhav Jain, and Gerbrand Ceder
Chemistry of Materials 2011 Volume 23(Issue 17) pp:3854
Publication Date(Web):August 17, 2011
DOI:10.1021/cm200753g
Cathode materials with structure similar to the mineral tavorite have shown promise for use in lithium-ion batteries, but this class of materials is relatively unexplored. We use high-throughput density-functional-theory calculations to evaluate tavorite-structured oxyphosphates, fluorophosphates, oxysulfates, and fluorosulfates for use as cathode materials in lithium-ion batteries. For each material we consider the insertion of both one and two lithium ions per redox-active metal, calculating average voltages and stability relative to a database of nearly 100,000 previously calculated compounds. To evaluate lithium mobility, we calculate the activation energies for lithium diffusion through the known tavorite cathode materials LiVO(PO4), LiV(PO4)F, and LiFe(SO4)F. Our calculations indicate that tavorite-structured materials are capable of very high rates of one-dimensional lithium diffusion, and several tavorite-structured materials may be capable of reversibly inserting two lithium ions per redox-active metal.Keywords: cathode material; computational; density functional theory; high-throughput; lithium-ion battery; tavorite;
Co-reporter:Shyue Ping Ong, Oliviero Andreussi, Yabi Wu, Nicola Marzari, and Gerbrand Ceder
Chemistry of Materials 2011 Volume 23(Issue 11) pp:2979
Publication Date(Web):May 10, 2011
DOI:10.1021/cm200679y
We investigated the cathodic and anodic limits of six room-temperature ionic liquids (ILs) formed from a combination of two common cations, 1-butyl-3-methylimidazolium (BMIM) and N,N-propylmethylpyrrolidinium (P13), and three common anions, PF6, BF4, and bis(trifluoromethylsulfonyl)imide (TFSI), using an approach that combines molecular dynamics (MD) simulations and density functional theory (DFT) calculations. All interion interactions were taken into account by explicitly modeling the entire liquid structure using classical MD, followed by DFT computations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies. The relative cathodic and anodic limits of BMIM PF6, BMIM BF4, BMIM TFSI, and P13 TFSI obtained from our approach are in fairly good agreement with existing experimental data. From our DFT calculations, we also obtained the cation- and anion-projected density of states (DOS), which provide information on the likely species contributing to reductive and oxidative decomposition. Our predictions support Howlett et al.’s earlier finding(1) that the TFSI anion is less stable than the P13 cation against reduction. In addition, our results provide surprising evidence of possible cation anodic instability; we predict the aromatic BMIM cation to be less stable against oxidation than the respective anions in BMIM PF6 and BMIM BF4, and the P13 cation to be less stable against oxidation than the PF6 anion in P13 PF6. We also present a comparison of the predictions of our approach with that of simpler approximations based on in vacuo or polarizable continuum model calculations.Keywords: BF4; bis(trifluoromethylsulfonyl)imide; density functional theory; electrochemical windows; imidazolium; ionic liquids; molecular dynamics; PF6; polarizable continuum model; pyrrolidinium; room temperature;
Co-reporter:Geoffroy Hautier, Anubhav Jain, Shyue Ping Ong, Byoungwoo Kang, Charles Moore, Robert Doe, and Gerbrand Ceder
Chemistry of Materials 2011 Volume 23(Issue 15) pp:3495
Publication Date(Web):July 13, 2011
DOI:10.1021/cm200949v
Phosphate materials are being extensively studied as lithium-ion battery electrodes. In this work, we present a high-throughput ab initio analysis of phosphates as cathode materials. Capacity, voltage, specific energy, energy density, and thermal stability are evaluated computationally on thousands of compounds. The limits in terms of gravimetric and volumetric capacity inherent to the phosphate chemistry are determined. Voltage ranges for all redox couples in phosphates are provided, and the structural factors influencing the voltages are analyzed. We reinvestigate whether phosphate materials are inherently safe and find that, for the same oxidation state, oxygen release happens thermodynamically at lower temperature for phosphates than for oxides. These findings are used to recommend specific chemistries within the phosphate class and to show the intrinsic limits of certain materials of current interest (e.g., LiCoPO4 and LiNiPO4).Keywords: ab initio; cathode; DFT; high-throughput; Li-ion battery; phosphates; safety; thermal stability;
Co-reporter:Geoffroy Hautier, Anubhav Jain, Hailong Chen, Charles Moore, Shyue Ping Ong and Gerbrand Ceder
Journal of Materials Chemistry A 2011 vol. 21(Issue 43) pp:17147-17153
Publication Date(Web):06 Oct 2011
DOI:10.1039/C1JM12216A
The discovery of new chemistries outperforming current lithium intercalation cathodes is of major technological importance. In this context, polyanionic systems with the potential to exchange multiple electrons per transition metal are particularly interesting because they could combine the safety of polyanion systems with higher specific energy. In this paper, we report on a series of new mixed polyanions compounds of formula AxM(YO3)(XO4) (with A = Na, Li; X = Si, As, P; Y = C, B; M = a redox active metal; and x = 0 to 3) identified by high-throughput ab initio computing. The computed stability of both lithium and sodium-based compounds is analyzed along with the voltage, specific energy and energy density of the lithium-based compounds. This analysis suggests several novel carbonophosphates and carbonosilicates as potential high capacity (>200 mAh/g) and specific energy (>700 Wh/kg) cathode materials for lithium-ion batteries.
Co-reporter:Geoffroy Hautier ; Chris Fischer ; Virginie Ehrlacher ; Anubhav Jain
Inorganic Chemistry 2011 Volume 50(Issue 2) pp:656-663
Publication Date(Web):December 13, 2010
DOI:10.1021/ic102031h
The existence of new compounds is often postulated by solid state chemists by replacing an ion in the crystal structure of a known compound by a chemically similar ion. In this work, we present how this new compound discovery process through ionic substitutions can be formulated in a mathematical framework. We propose a probabilistic model assessing the likelihood for ionic species to substitute for each other while retaining the crystal structure. This model is trained on an experimental database of crystal structures, and can be used to quantitatively suggest novel compounds and their structures. The predictive power of the model is demonstrated using cross-validation on quaternary ionic compounds. The different substitution rules embedded in the model are analyzed and compared to some of the traditional rules used by solid state chemists to propose new compounds (e.g., ionic size).
Co-reporter:Yun Jung Lee, Youjin Lee, Dahyun Oh, Tiffany Chen, Gerbrand Ceder and Angela M. Belcher
Nano Letters 2010 Volume 10(Issue 7) pp:2433-2440
Publication Date(Web):May 27, 2010
DOI:10.1021/nl1005993
We report the synthesis and electrochemical activity of gold and silver noble metals and their alloy nanowires using multiple virus clones as anode materials for lithium ion batteries. Using two clones, one for specificity (p8#9 virus) and one versatility (E4 virus), noble metal nanowires of high-aspect ratio with diameters below 50 nm were successfully synthesized with control over particle sizes, morphologies, and compositions. The biologically derived noble metal alloy nanowires showed electrochemical activities toward lithium even when the electrodes were prepared from bulk powder forms. The improvement in capacity retention was accomplished by alloy formation and surface stabilization. Although the cost of noble metals renders them a less ideal choice for lithium ion batteries, these noble metal/alloy nanowires serve as great model systems to study electrochemically induced transformation at the nanoscale. Given the demonstration of the electrochemical activity of noble metal alloy nanowires with various compositions, the M13 biological toolkit extended its utility for the study on the basic electrochemical property of materials.
Co-reporter:Rahul Malik, Damian Burch, Martin Bazant, and Gerbrand Ceder
Nano Letters 2010 Volume 10(Issue 10) pp:4123-4127
Publication Date(Web):August 26, 2010
DOI:10.1021/nl1023595
Diffusion constants are typically considered to be independent of particle size with the benefit of nanosizing materials arising solely from shortened transport paths. We show that for materials with one-dimensional atomic migration channels, the diffusion constant depends on particle size with diffusion in bulk being much slower than in nanoparticles. This model accounts for conflicting data on LiFePO4, an important material for rechargeable lithium batteries, specifically explaining why it functions exclusively on the nanoscale.
Co-reporter:Geoffroy Hautier, Christopher C. Fischer, Anubhav Jain, Tim Mueller and Gerbrand Ceder
Chemistry of Materials 2010 Volume 22(Issue 12) pp:3762
Publication Date(Web):May 27, 2010
DOI:10.1021/cm100795d
Finding new compounds and their crystal structures is an essential step to new materials discoveries. We demonstrate how this search can be accelerated using a combination of machine learning techniques and high-throughput ab initio computations. Using a probabilistic model built on an experimental crystal structure database, novel compositions that are most likely to form a compound, and their most-probable crystal structures, are identified and tested for stability by ab initio computations. We performed such a large-scale search for new ternary oxides, discovering 209 new compounds with a limited computational budget. A list of these predicted compounds is provided, and we discuss the chemistries in which high discovery rates can be expected.
Co-reporter:Shyue Ping Ong, Anubhav Jain, Geoffroy Hautier, Byoungwoo Kang, Gerbrand Ceder
Electrochemistry Communications 2010 Volume 12(Issue 3) pp:427-430
Publication Date(Web):March 2010
DOI:10.1016/j.elecom.2010.01.010
We present an analysis of the thermal reduction of delithiated LiMnPO4 and LiFePO4 based on the quarternary phase diagrams as calculated from first principles. Our results confirm the recent experimental findings that MnPO4 decomposes at a much lower temperature than FePO4, thereby potentially posing larger safety issues for LiMnPO4 cathodes. We find that while substantial oxygen is released as MnPO4 reduces to Mn2P2O7, the mixed valence phases that form in the decomposition process of FePO4 limit the amount of oxygen evolved.
Co-reporter:Shyue Ping Ong, Gerbrand Ceder
Electrochimica Acta 2010 Volume 55(Issue 11) pp:3804-3811
Publication Date(Web):15 April 2010
DOI:10.1016/j.electacta.2010.01.091
The cathodic and anodic stabilities of room-temperature ionic liquids (ILs) are important factors in their applications in electrochemical devices. In this work, we investigated the electron affinities of cations and ionization energies of anions for ionic liquids by density functional theory (DFT) calculations at the B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d) level. Over 200 unique cations and anions, formed from a set of six base cation structures, three base anion structures, and seven functional groups, were investigated. We find the trends in calculated EAs of alkylated cations and IEs of alkylated anions to be in good agreement with observed experimental trends in relative cathodic and anodic stabilities of various ILs. In addition, we also investigated the effect that functional group substitution at distinct positions in the ions have on the EA of the 1,2,3-trimethylimidazolium cation and the IE of the PF5CF3 anion. The overall impact on the EA or IE can be explained by the known electron-donating and electron-withdrawing inductive and resonance effects of the attached functional group, and the relative strength of the effect depends on the substitution position.
Co-reporter:Tim Mueller and Gerbrand Ceder
ACS Nano 2010 Volume 4(Issue 10) pp:5647
Publication Date(Web):September 17, 2010
DOI:10.1021/nn101224j
Density functional theory and the cluster expansion method are used to model 2−10 nm sodium alanate (NaAlH4) nanoparticles and related decomposition products Na3AlH6, NaH, and Al. While bulk sodium alanate releases hydrogen in a two-step process, our calculations predict that below a certain size sodium alanate nanoparticles decompose in a single step directly to NaH, Al, and H2 due to the effect of particle size on decomposition thermodynamics. This may explain why sodium alanate nanoparticles, unlike bulk sodium alanate, have been observed to release hydrogen in the operating temperature range of proton exchange membrane fuel cells. In addition, we identify low-energy surfaces that may be important for the dynamics of hydrogen storage and release from sodium alanate nanoparticles.Keywords: Al; aluminum; cluster expansion; density functional theory; fuel cell; hydrogen storage; Na3AlH6; NaAlH4; NaH; nanoparticle; sodium alanate; sodium hydride; surface energy
Co-reporter:Denis Kramer and Gerbrand Ceder
Chemistry of Materials 2009 Volume 21(Issue 16) pp:3799
Publication Date(Web):July 30, 2009
DOI:10.1021/cm9008943
Surface energies of several low-index surfaces of layered LiCoO2 are investigated as a function of the external lithium and oxygen chemical potentials by means of First Principles calculations in the generalized gradient approximation (GGA) to density functional theory (DFT), treating on-site electron correlation within the DFT+U framework. We find the set of surfaces contained in the equilibrium shape to be depending on environment. The (0001) and (101̅4) surfaces are present for all reasonable values of the Li and O chemical potentials. The (011̅2) surface, however, is stable only under oxidizing conditions. The equilibrium shape is sensitive to the equilibration environment because the thermodynamically favorable surface terminations and surface energies of the polar (0001) and (011̅2) surfaces are a function of environment. This provides a lever to tailor the crystal shape according to application requirements (e.g., as active material in lithium-ion batteries).
Co-reporter:G. Ceder, B. Kang
Journal of Power Sources 2009 Volume 194(Issue 2) pp:1024-1028
Publication Date(Web):1 December 2009
DOI:10.1016/j.jpowsour.2009.07.004
Co-reporter:Byoungwoo Kang
&
Gerbrand Ceder
Nature 2009 458(7235) pp:190
Publication Date(Web):2009-03-12
DOI:10.1038/nature07853
The storage of electrical energy at high charge and discharge rate is an important technology in today’s society, and can enable hybrid and plug-in hybrid electric vehicles and provide back-up for wind and solar energy. It is typically believed that in electrochemical systems very high power rates can only be achieved with supercapacitors, which trade high power for low energy density as they only store energy by surface adsorption reactions of charged species on an electrode material1, 2, 3. Here we show that batteries4, 5 which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors. We realize this in LiFePO4 (ref. 6), a material with high lithium bulk mobility7, 8, by creating a fast ion-conducting surface phase through controlled off-stoichiometry. A rate capability equivalent to full battery discharge in 10–20 s can be achieved.
Co-reporter:Robert E. Doe, Kristin A. Persson, Y. Shirley Meng and Gerbrand Ceder
Chemistry of Materials 2008 Volume 20(Issue 16) pp:5274
Publication Date(Web):July 25, 2008
DOI:10.1021/cm801105p
We have used density functional theory (DFT) to investigate the ternary phase diagram of the Li−Fe−F system and the reactions of Li with iron fluorides. Several novel compounds, not previously identified in the Li−Fe−F system, are predicted to be stable. Electrochemical voltage profiles, derived from the evolution of the Li chemical potential in the calculated phase diagram, are in reasonable agreement with experimental trends. The effect of particle size on the Fe that precipitates when LixFeF3 reacts with Li is also investigated. We find that when 1 nm Fe particles form, the potential for this reaction is considerably reduced from its bulk value and relate this to the experimental observations. Furthermore, we formulate a model for the significant hysteresis that is observed in the lithiation and delithiation of FeF3. Nonequilibrium paths derived by assuming much faster diffusion of Li than Fe are in reasonable agreement with experimental profiles. Our kinetic model predicts that the iron fluoride reaction follows a different path through the phase diagram during conversion (discharge) and reconversion (charge), which results in the voltage profile hysteresis observed during experiment. The proposed kinetic model also explains why upon extraction of Li from a 3/1 mixture of LiF and Fe a rutile FeF2-like structure can form, even when iron should be oxidized to Fe3+ by extraction of three Li+ per Fe.
Co-reporter:Shyue Ping Ong, Lei Wang, Byoungwoo Kang and Gerbrand Ceder
Chemistry of Materials 2008 Volume 20(Issue 5) pp:1798
Publication Date(Web):February 7, 2008
DOI:10.1021/cm702327g
We present an efficient way to calculate the phase diagram of the quaternary Li−Fe−P−O2 system using ab initio methods. The ground-state energies of all known compounds in the Li−Fe−P−O2 system were calculated using the generalized gradient approximation (GGA) approximation to density functional theory (DFT) and the DFT+U extension to it. Considering only the entropy of gaseous phases, the phase diagram was constructed as a function of oxidation conditions, with the oxygen chemical potential, μO2, capturing both temperature and oxygen partial pressure dependence. A modified Ellingham diagram was also developed by incorporating the experimental entropy data of gaseous phases. The phase diagram shows LiFePO4 to be stable over a wide range of oxidation environments, being the first Fe2+-containing phase to appear upon reduction at μO2 = −11.52 eV and the last of the Fe-containing phosphates to be reduced at μO2 = −16.74 eV. Lower μO2 represents more reducing conditions, which generally correspond to higher temperatures and/or lower oxygen partial pressures and/or the presence of reducing agents. The predicted phase relations and reduction conditions compare well to experimental findings on stoichiometric and Li-off-stoichiometric LiFePO4. For Li-deficient stoichiometries, the formation of iron phosphate phases (Fe7(PO4)6 and Fe2 P2O7) commonly observed under moderately reducing conditions during LiFePO4 synthesis and the formation of iron phosphides (Fe2P) under highly reducing conditions are consistent with the predictions from our phase diagram. Our diagrams also predict the formation of Li3PO4 and iron oxides for Li-excess stoichiometries under all but the most reducing conditions, again in agreement with experimental observations. For stoichiometric LiFePO4, the phase diagram gives the correct oxidation products of Li3Fe2(PO4)3 and Fe2O3. The predicted carbothermal reduction temperatures for LiFePO4 from the Ellingham diagram are also within the range observed in experiments (800–900 °C). The diagrams developed provide a better understanding of phase relations within the Li−Fe−P−O2 system and serve as a guide for future experimental efforts in materials processing, in particular, for the optimization of synthesis routes for LiFePO4.
Co-reporter:Kisuk Kang;Ying Shirley Meng;Julien Bréger;Clare P. Grey
Science 2006 Vol 311(5763) pp:977-980
Publication Date(Web):17 Feb 2006
DOI:10.1126/science.1122152
Abstract
New applications such as hybrid electric vehicles and power backup require rechargeable batteries that combine high energy density with high charge and discharge rate capability. Using ab initio computational modeling, we identified useful strategies to design higher rate battery electrodes and tested them on lithium nickel manganese oxide [Li(Ni0.5Mn0.5)O2], a safe, inexpensive material that has been thought to have poor intrinsic rate capability. By modifying its crystal structure, we obtained unexpectedly high rate-capability, considerably better than lithium cobalt oxide (LiCoO2), the current battery electrode material of choice.
Co-reporter:Fei Zhou, Matteo Cococcioni, Kisuk Kang, Gerbrand Ceder
Electrochemistry Communications 2004 Volume 6(Issue 11) pp:1144-1148
Publication Date(Web):November 2004
DOI:10.1016/j.elecom.2004.09.007
The Li intercalation potential of LiMPO4 and LiMSiO4 compounds with M = Fe, Mn, Co and Ni is computed with the GGA + U method. It is found that this approach is considerably more accurate than standard LDA or GGA methods. The calculated potentials for LiFePO4, LiMnPO4 and LiCoPO4 agree to within 0.1 V with experimental results. The LiNiPO4 potential is predicted to be above 5 V. The potentials of the silicate materials are all found to be rather high, but LiFeSiO4 and LiCoSiO4 have negligible volume change upon Li extraction.
Co-reporter:Fei Zhou, Kisuk Kang, Thomas Maxisch, Gerbrand Ceder, Dane Morgan
Solid State Communications 2004 Volume 132(3–4) pp:181-186
Publication Date(Web):October 2004
DOI:10.1016/j.ssc.2004.07.055
Materials with the olivine LixMPO4 structure form an important new class of materials for rechargeable Li batteries. There is significant interest in their electronic properties because of the importance of electronic conductivity in batteries for high-rate applications. The density of states of LixMPO4 (x=0, 1 and M=Fe, Mn) has been determined with the ab initio generalized gradient approximation (GGA)+U method, appropriate for these correlated electron systems. Computed results are compared with the optical gap of LiFePO4, as measured using UV–Vis-NIR diffuse reflectance spectroscopy. The results obtained from experiment (3.8–4.0 eV) and GGA+U computations (3.7 eV) are in very good agreement. However, standard GGA, without the same level of treatment of electron correlation, is shown to make large errors in predicting the electronic structure. It is argued that olivines are likely to be polaronic conductors with extrinsically determined carrier levels and that their electronic conductivity is therefore not simply related to the band gap.
Co-reporter:Sangtae Kim, Xiaohua Ma, Shyue Ping Ong and Gerbrand Ceder
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 44) pp:NaN15578-15578
Publication Date(Web):2012/10/01
DOI:10.1039/C2CP43377J
To understand the difference in reversible energy storage capacity between the O3-type layered Na and Li compounds, we use first principles calculations to study and contrast the effect of two well-known destabilization mechanisms, transformation into the spinel-type structures and cation mixing due to transition metal migration. This study is performed on the layered oxides at the A0.5MO2 composition, where A = (Na, Li) and M is a 3d transition metal. We find that while all Li0.5MO2 compounds have strong driving forces and low energy kinetic paths to transform to the spinel structure, Na0.5MO2 compounds do not have thermodynamic driving forces to transform to spinel type structures. We also find that transition metal mobility is higher in Li layered compounds than in Na layered compounds because of the unusual activated state for transition metal hopping. For many compounds, migration goes along an oct–tet–oct path, but transition metal migration needs to be assisted by alkali migration into a tetrahedral site forming activated Atet–Mtet defects; substituting Na for Li in the layered structure results in increased transition metal migration barriers due to the larger size of Na+ ions. Overall, our findings indicate that Na compounds in the layered O3 structure have fundamentally different destabilization mechanisms to those of Li compounds. This distinction allows superior battery electrode performance in many Na compounds and offers optimistic perspective on finding many high energy density Na electrodes that cycle with stable high capacity.
Co-reporter:Anubhav Jain, Geoffroy Hautier, Shyue Ping Ong, Stephen Dacek and Gerbrand Ceder
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 8) pp:NaN5953-5953
Publication Date(Web):2015/01/30
DOI:10.1039/C5CP00250H
High voltage and high thermal safety are desirable characteristics of cathode materials, but difficult to achieve simultaneously. This work uses high-throughput density functional theory computations to evaluate the link between voltage and safety (as estimated by thermodynamic O2 release temperatures) for over 1400 cathode materials. Our study indicates that a strong inverse relationship exists between voltage and safety: just over half the variance in O2 release temperature can be explained by voltage alone. We examine the effect of polyanion group, redox couple, and ratio of oxygen to counter-cation on both voltage and safety. As expected, our data demonstrates that polyanion groups improve safety when comparing compounds with similar voltages. However, a counterintuitive result of our study is that polyanion groups produce either no benefit or reduce safety when comparing compounds with the same redox couple. Using our data set, we tabulate voltages and oxidation potentials for over 105 combinations of redox couple/anion, which can be used towards the design and rationalization of new cathode materials. Overall, only a few compounds in our study, representing limited redox couple/polyanion combinations, exhibit both high voltage and high safety. We discuss these compounds in more detail as well as the opportunities for designing safe, high-voltage cathodes.
Co-reporter:Aziz Abdellahi, Oncu Akyildiz, Rahul Malik, Katsuyo Thornton and Gerbrand Ceder
Journal of Materials Chemistry A 2014 - vol. 2(Issue 37) pp:NaN15447-15447
Publication Date(Web):2014/07/25
DOI:10.1039/C4TA02935F
We gain new insights into the equilibrium properties and potential two-phase lithiation mechanisms in LiFePO4 nano-particles by conducting a first-principles investigation of the anisotropic chemical interfacial energy landscape in LiFePO4. The chemical interfacial energy per unit area along the ac plane is found to be remarkably low (7 mJ m−2) with respect to the bc (115 mJ m−2) and ab (95 mJ m−2) chemical interfacial energies. Because chemical interfacial energy and coherency strain energy have different anisotropies, the thermodynamically stable interface orientation is shown to depend both on the particle size and on the particle morphology. In particular, ac interfaces are favored for isotropic particles below 40 nm. This indicates that, if experimentally-relevant nano-particles were to (de)lithiate under a thermodynamic two-phase mechanism, the resulting front would be orientated along the ac plane, and not along the bc plane as is assumed in most lithiation models in the literature.
Co-reporter:Hong Zhu, Geoffroy Hautier, Umut Aydemir, Zachary M. Gibbs, Guodong Li, Saurabh Bajaj, Jan-Hendrik Pöhls, Danny Broberg, Wei Chen, Anubhav Jain, Mary Anne White, Mark Asta, G. Jeffrey Snyder, Kristin Persson and Gerbrand Ceder
Journal of Materials Chemistry A 2016 - vol. 4(Issue 19) pp:NaN4331-4331
Publication Date(Web):2016/04/27
DOI:10.1039/C6TC90077A
Correction for ‘Computational and experimental investigation of TmAgTe2 and XYZ2 compounds, a new group of thermoelectric materials identified by first-principles high-throughput screening’ by Hong Zhu et al., J. Mater. Chem. C, 2015, 3, 10554–10565.
Co-reporter:Hong Zhu, Geoffroy Hautier, Umut Aydemir, Zachary M. Gibbs, Guodong Li, Saurabh Bajaj, Jan-Hendrik Pöhls, Danny Broberg, Wei Chen, Anubhav Jain, Mary Anne White, Mark Asta, G. Jeffrey Snyder, Kristin Persson and Gerbrand Ceder
Journal of Materials Chemistry A 2015 - vol. 3(Issue 40) pp:NaN10565-10565
Publication Date(Web):2015/08/13
DOI:10.1039/C5TC01440A
A new group of thermoelectric materials, trigonal and tetragonal XYZ2 (X, Y: rare earth or transition metals, Z: group VI elements), the prototype of which is TmAgTe2, is identified by means of high-throughput computational screening and experiment. Based on density functional theory calculations, this group of materials is predicted to attain high zT (i.e. ∼1.8 for p-type trigonal TmAgTe2 at 600 K). Among approximately 500 chemical variants of XYZ2 explored, many candidates with good stability and favorable electronic band structures (with high band degeneracy leading to high power factor) are presented. Trigonal TmAgTe2 has been synthesized and exhibits an extremely low measured thermal conductivity of 0.2–0.3 W m−1 K−1 for T > 600 K. The zT value achieved thus far for p-type trigonal TmAgTe2 is approximately 0.35, and is limited by a low hole concentration (∼1017 cm−3 at room temperature). Defect calculations indicate that TmAg antisite defects are very likely to form and act as hole killers. Further defect engineering to reduce such XY antisites is deemed important to optimize the zT value of the p-type TmAgTe2.
Co-reporter:Geoffroy Hautier, Anubhav Jain, Hailong Chen, Charles Moore, Shyue Ping Ong and Gerbrand Ceder
Journal of Materials Chemistry A 2011 - vol. 21(Issue 43) pp:NaN17153-17153
Publication Date(Web):2011/10/06
DOI:10.1039/C1JM12216A
The discovery of new chemistries outperforming current lithium intercalation cathodes is of major technological importance. In this context, polyanionic systems with the potential to exchange multiple electrons per transition metal are particularly interesting because they could combine the safety of polyanion systems with higher specific energy. In this paper, we report on a series of new mixed polyanions compounds of formula AxM(YO3)(XO4) (with A = Na, Li; X = Si, As, P; Y = C, B; M = a redox active metal; and x = 0 to 3) identified by high-throughput ab initio computing. The computed stability of both lithium and sodium-based compounds is analyzed along with the voltage, specific energy and energy density of the lithium-based compounds. This analysis suggests several novel carbonophosphates and carbonosilicates as potential high capacity (>200 mAh/g) and specific energy (>700 Wh/kg) cathode materials for lithium-ion batteries.
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