M. Stanley Whittingham

State University of New York, New York City, New York, United States

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Publications (231)632.03 Total impact

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    ABSTRACT: The electrochemical performance of nanoscaled FePy, synthesized through a facile mechanochemical method with a high phosphorous content, has been evaluated by different techniques. This alloy has higher capacity and better cyclability at various rates than the reported results to date. Particle size and electrode loading density are important for the charge/discharge behavior; solid electrolyte interphase film is beneficial for the cycling performance.
    Journal of Power Sources 12/2014; 270:248–256. · 5.26 Impact Factor
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    ABSTRACT: Understanding the reaction mechanism of olivine compounds as electrode materials for lithium lithium-ion batteries have has received much attention recently. The question whether olivine LiFePO4 undergoes two-phase or non-nonequilibrium single-phase reaction during electrochemical processes has taken center stage in the understanding of the faster reaction kinetics observed in this material. Here, the lithiation/delithiation mechanism of Mg Mg-substituted LiFePO4 using high high-resolution X-ray diffraction(XRD), transmission electron microscopy(TEM), and electrochemical measurements is reported. Ex situ partially (de)lithiated olivine- LiMg0.2Fe0.8PO4 show the existence of stable equilibrium intermediate phases as characterized by the presence of more than two phases and broadness of diffraction peaks. Electron energy loss spectroscopy profiles across individual nanoparticles further confirm uniform lithiation with a constant Fe–L3 energy measured across each nanoparticle, suggestive of solid solution behavior in individual particles. In addition, a continuous shift in the diffraction peak position is observed even in the “two-phase” region in the ex situ electrochemical (de)lithiated electrodes.
    Advanced Energy Materials 12/2014; · 14.39 Impact Factor
  • M Stanley Whittingham
    Chemical reviews. 10/2014;
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    ABSTRACT: Lithium cobalt germanate (Li2CoGeO4) has been synthesized for the first time by a hydrothermal method at 150 °C. Elemental composition, morphology, and crystal structure of this compound were characterized by various analytical techniques including SEM, TEM, ICP, and XRD analyses. Structure refinement and DFT calculation suggests the resulting Li2CoGeO4 from hydrothermal synthesis has a crystal structure isostructural with Li2ZnGeO4, significantly different from previous reports. Electrochemical studies confirmed Li2CoGeO4 as an active catalyst for oxygen evolution reaction (OER). In alkaline electrolyte (0.1 M NaOH), rotating disk electrodes made with Li2CoGeO4 as catalyst have a Tafel slope of c.a. 67 mV/dec and an overpotential of 330 mV at 50 μA/cm2cat, about 90 mV less than electrodes containing another known OER catalyst, Co3O4. Further characterization with cyclic voltammetry, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and elemental analyses revealed the oxidation of cobalt from 2+ to 3+ during the reaction, along with significant surface amorphization and loss of Li and Ge from the catalyst.
    J. Mater. Chem. A. 09/2014;
  • Electrochemistry Communications 09/2014; 46:67–70. · 4.29 Impact Factor
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    ABSTRACT: We have revealed the critical role of carbon coating in the stability and thermal behaviour of olivine MnPO4 obtained by chemical delithiation of LiMnPO4. (Li)MnPO4 samples with various particle sizes and carbon contents were studied. Carbon-free LiMnPO4 obtained by solid state synthesis in O2 becomes amorphous upon delithiation. Small amounts of carbon (0.3 wt%) help to stabilize the olivine structure, so that completely delithiated crystalline olivine MnPO4 can be obtained. Larger amount of carbon (2 wt%) prevents full delithiation. Heating in air, O2, or N2 results in structural disorder (<300 °C), formation of an intermediate sarcopside Mn3(PO4)2 phase (350–450 °C), and complete decomposition to Mn2P2O7 on extended heating at 400 °C. Carbon coating protects MnPO4 from reacting with environmental water, which is detrimental to its structural stability.
    J. Mater. Chem. A. 07/2014; 2(32).
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    ABSTRACT: This work attempts to understand the rate capability of layered transition metal oxides LiNiyMnyCo1−2yO2 (0.33 ≤ y ≤ 0.5). The rate capability of LiNiyMnyCo1−2yO2 increase with increasing Co in the compounds and with increasing amount of carbon additives in the electrodes. The lithium diffusion coefficients and electronic conductivities of LixNiyMnyCo1−2yO2 are investigated and compared. The 333 compound has higher diffusivity and electronic conductivity and thus better rate performance than 550. Chemical diffusion coefficients for both delithiation and lithiation of LixNiyMnyCo1−2yO2 investigated by GITT and PITT experiments are calculated to be around 10−10 cm2 s−1, lower than that of LixCoO2. The electronic conductivity of LixNiyMnyCo1−2yO2 is inferior compared to LixCoO2 at same temperature and delithiation stage. However, the LixNiyMnyCo1−2yO2 are able to deliver 55%–80% of theoretical capacity at 5 C with good electronic wiring in the composite electrode that make them very promising candidates for electric propulsion in terms of rate capability.
    Journal of Power Sources 01/2014; 268:106–112. · 5.26 Impact Factor
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    ABSTRACT: The layered compound δ-(MoO2)2P2O7 is synthesized by heating MoO2HPO4·H2O (560 °C, 6 min).
    ChemInform 11/2013; 44(46).
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    ABSTRACT: High-voltage cathode material LiNi0.5Mn1.5O4 has been prepared with a novel organic coprecipitation route. The as-prepared sample was compared with samples produced through traditional solid state method and hydroxide coprecipitation method. The morphology was observed by SEM and the spinel structures were characterized by XRD and FTIR. Besides the ordered/disordered distribution of Ni/Mn on octahedral sites, the confusion between Li and transition metal is pointed out to be another important factor responsible for the corresponding performance, which is worthy further investigation. Galvanostatic cycles, CV and EIS are employed to characterize the electrochemical properties. The organic coprecipitation route produced sample shows superior rate capability and stable structure during cycling.
    ACS Applied Materials & Interfaces 09/2013; · 5.90 Impact Factor
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    P. Y. Zavalij, F. Zhang, M. S. Whittingham
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    Jingdong Guo, P. Zavalij, M. S. Whittingham
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    ABSTRACT: Aluminum–silicon alloys are an important class of commercial casting materials having wide applications in automotive and aerospace industries. Etching the Al–Si eutectic leads to selective dissolution of Al, resulting in novel morphology – macroporous Si spheres with a three-dimensional nano network. Up to 5% Al is dissolved in Si, leading to an expansion of the crystal lattice. The resulting porous Si is electrochemically active with lithium and thus can be used as a high capacity anode for lithium-ion batteries. The etching of Al–Si provides a simple and low-cost method of producing nano-structured Si materials.
    MRS Communications 09/2013; 3(03). · 1.55 Impact Factor
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    ABSTRACT: The layered structure of molybdenum (oxy)pyrophosphate (δ-(MoO2)2P2O7) was synthesized by heating MoO2HPO4·H2O precursor at 560 °C. The synthesis temperature was selected using in situ high-temperature X-ray diffraction (XRD) depicting phase transformations of the precursor from room temperature up to 800 °C. Electrochemical evaluation reveals that up to four Li ions per formula unit can be intercalated into δ-(MoO2)2P2O7 upon discharge to 2 V. Three voltage plateaus are observed at 3.2, 2.6, and 2.1 V, lower than the theoretical predictions. The first plateau corresponds to the intercalation of 1.2 Li forming δ-Li1.2(MoO2)2P2O7, the same structure formed upon chemical lithiation with LiI. In-situ XRD indicates two-phase reaction upon the first lithium insertion and expansion of the lithiated phase unit cell in the a direction. Intercalation of the second lithium results in a different lithiated structure, which is also reversible, giving the capacity of about 110 mAh/g between 2.3 and 4 V. More lithium-ion intercalation leads to loss of crystallinity and structural reversibility. The Mo reduction upon lithiation is consistent with the amount of Li intercalated as confirmed by the X-ray absorption fine structure.
    Chemistry of Materials 08/2013; · 8.24 Impact Factor
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    ABSTRACT: A series of layered oxides within the NaxNiix/2Mn1-x/2O2 (2/3 ≤ x ≤ 1) system were synthesized by classical solid-state methodologies. A study of their long and short-range structure was undertaken by combining X-ray diffraction and NMR spectroscopy. A transition from P2 to O3 stacking was observed at x > 0.8 when samples were made at 900 °C, which was accompanied by disordering of ions in the transition metal layer. The magnetic properties of the materials were consistent with this picture of ordering, with all samples showing antiferromagnetic character. At x = 2/3, competition between a P2 and a P3 structure, with different degrees of transition metal ordering, was found depending on the synthesis temperature. Na/Li exchange led to structures with octahedral or tetrahedral coordination of the alkali metal, and Li/Ni crystallographic exchange in the resulting O3 phases. The transition from alkali metal prismatic coordination to octahedral/tetrahedral coordination involves [TMO6]∞ layer shearing that induces some structural disorder through the formation of stacking faults.
    Inorganic Chemistry 08/2013; 52(15):8540-50. · 4.59 Impact Factor
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    ABSTRACT: Li1-3y[VyFe]PO4 (y = 0, 0.025, 0.05, 0.1, 0.2) is synthesized by solid state reaction of Li2CO3, FeC2O4, NH4H2PO4, and NH4VO3 (8.5% H2/He, 550 °C, 10 h).
    ChemInform 07/2013;
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    ABSTRACT: A combination of soft and hard synchrotron-based spectroscopy with first-principles density functional theory within the GGA + U framework is used to investigate the distortion of the Mn local environment of LixMnPO4 as a function of electrochemical delithiation (x = 1.0, 0.75, 0.5, 0.25) and its effect on the electron and hole polaron formation. Analysis of the soft X-ray absorption spectroscopy (XAS) of the Mn L3,2-edges confirmed the evolution from the Mn2+ to the Mn3+ charge state as a two-phase reaction upon delithiation; the corresponding Mn K-edge extended X-ray fine structure measurements clearly revealed a splitting of the Mn–O nearest-neighbor distances with increasing Mn3+ character. In addition, the O K-edge absorption and emission spectra confirmed the corresponding orbital lifting of degeneracy accompanying the distortion of the MnO6 octahedra in the Mn3+ state. Our GGA + U calculations show that the distortion is not a strict Jahn–Teller distortion but is instead a preferential elongation of two of the equatorial Mn–O bonds (edge-sharing with the PO4), which results in a Mn–O–P induction driven hybridization of the unoccupied states (i.e., a pseudo Jahn–Teller distortion). Excellent agreement between the calculated electronic structure and our soft X-ray measurements of the electrochemically delithiated LixMnPO4 nanoparticles verifies the link between the preferential structural distortion and the resultant hybridization of the unoccupied 3d dxz and dx2–y2 orbitals. Our analysis of the corresponding calculated electron and hole polaron supports claims that the elongation of the equatorial bonds (edge-sharing with the PO4) in the Mn3+ charge state (i.e., the pseudo Jahn–Teller distortion) is responsible for increasing the activation energy for polaron migration and the formation energy of the electron (hole) lithium ion (vacancy) complex of the Mn olivine compared to the Fe olivine.
    The Journal of Physical Chemistry C 05/2013; 117(20):10383-10396. · 4.84 Impact Factor
  • Kazuo Eda, Tatsuya Koduka, Yuichi Iriki, M. Stanley Whittingham
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    ABSTRACT: We found that the hexatriacontamolybdate [Mo36O112(H2O)16]8− ({Mo36}) compound of 1,3-diamino-2-propanol (βOHC3-DA) forms seven structural phases with the formula (βOHC3-DA)4{Mo36}·nH2O. They showed a range of dimensionality: three zero-dimensional (0D), two 1D, and two 2D MoO framework structures consisting of {Mo36} anions. Two of the phases have 0D framework structures crystallized in the mother solution. The remaining five phases were obtained when the crystals of these two 0D phases were aged in resin. The dense 2D framework ({Mo36}-nanosheet) of the title compound was formed via solid-phase condensation reactions under restricted dehydration conditions such as in resin-coated crystals, unlike the loose {Mo36}-nanosheet of the (C3DA)4{Mo36}·nH2O. The formation processes of the related high-dimensional MoO frameworks were guided by hydrogen-bonding contacts initially formed between {Mo36} anions in the crystal. There were two different conversion routes: the one starting from the phase consisting of {Mo36} hydrogen-bonded at their head/foot parts lead to the dense 2D nanosheet, while the other originating from the phase consisting of {Mo36} hydrogen-bonded at their trunk parts, to 1D {Mo36}-nanochain with rare triple oxygen bridges. These routes had neither branching nor intercrossing.
    Journal of Solid State Chemistry 03/2013; 199:134–140. · 2.04 Impact Factor
  • Chem. Mater. 01/2013; 25(17):3513-3521.
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    ABSTRACT: Substituted lithium transition-metal (TM) phosphate LiFe(x)Mn(1-x)PO(4) materials with olivine-type structures are among the most promising next generation lithium ion battery cathodes. However, a complete atomic-level description of the structure of such phases is not yet available. Here, a combined experimental and theoretical approach to the detailed assignment of the (31)P NMR spectra of the LiFe(x)Mn(1-x)PO(4) (x = 0, 0.25, 0.5, 0.75, 1) pure and mixed TM phosphates is developed and applied. Key to the present work is the development of a new NMR experiment enabling the characterization of complex paramagnetic materials via the complete separation of the individual isotropic chemical shifts, along with solid-state hybrid DFT calculations providing the separate hyperfine contributions of all distinct Mn-O-P and Fe-O-P bond pathways. The NMR experiment, referred to as aMAT, makes use of short high-powered adiabatic pulses (SHAPs), which can achieve 100% inversion over a range of isotropic shifts on the order of 1 MHz and with anisotropies greater than 100 kHz. In addition to complete spectral assignments of the mixed phases, the present study provides a detailed insight into the differences in electronic structure driving the variations in hyperfine parameters across the range of materials. A simple model delimiting the effects of distortions due to Mn/Fe substitution is also proposed and applied. The combined approach has clear future applications to TM-bearing battery cathode phases in particular and for the understanding of complex paramagnetic phases in general.
    Journal of the American Chemical Society 09/2012; 134(41):17178. · 10.68 Impact Factor
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    ABSTRACT: High voltage spinel LiNi(0.5)Mn(1.5)O(4) is a very promising cathode material for lithium ion batteries that can be used to power hybrid electrical vehicles (HEVs). Through careful control of the cooling rate after high temperature calcination, LiNi(0.5)Mn(1.5)O(4) spinels with different disordered phase and/or Mn(3+) contents have been synthesized. It is revealed that during the slow cooling process (<3 °C min(-1)), oxygen deficiency is reduced by the oxygen intake, thus the residual Mn(3+) amount is also decreased in the spinel due to charge neutrality. In situ X-ray diffraction (XRD) demonstrates that the existence of a disordered phase fundamentally changes the spinel phase transition pathways during the electrochemical charge-discharge process. The presence of an appropriate amount of oxygen deficiency and/or Mn(3+) is critical to accelerate the Li(+) ion transport within the crystalline structure, which is beneficial to enhance the electrochemical performance of LiNi(0.5)Mn(1.5)O(4). LiNi(0.5)Mn(1.5)O(4) with an appropriate amount of disordered phase offers high rate capability (96 mAh g(-1) at 10 °C) and excellent cycling performance with 94.8% capacity retention after 300 cycles. The fundamental findings in this work can be widely applied to guide the synthesis of other mixed oxides or spinels as high performance electrode materials for lithium ion batteries.
    Physical Chemistry Chemical Physics 09/2012; 14(39):13515-21. · 4.20 Impact Factor

Publication Stats

1k Citations
632.03 Total Impact Points

Institutions

  • 1996–2014
    • State University of New York
      New York City, New York, United States
  • 1992–2014
    • Binghamton University
      • • Department of Chemistry
      • • Institute for Materials Research
      Binghamton, New York, United States
  • 2013
    • Stony Brook University
      • Department of Chemistry
      Stony Brook, NY, United States
  • 2012
    • Pacific Northwest National Laboratory
      • Energy and Environment Directorate
      Richland, Washington, United States
    • Lawrence Berkeley National Laboratory
      Berkeley, California, United States
  • 2009
    • State University of New York at Potsdam
      • Department of Biology
      Potsdam, New York, United States
    • University of Houston
      Houston, Texas, United States
  • 2004–2009
    • Kobe University
      • Department of Chemistry
      Kōbe, Hyōgo, Japan
  • 2008
    • Loyola University Maryland
      Baltimore, Maryland, United States
  • 2007
    • University of Tennessee
      • Department of Chemistry
      Knoxville, TN, United States
  • 1999
    • McMaster University
      Hamilton, Ontario, Canada
    • National Academy of Sciences
      New York City, New York, United States