Joint NMR and Diffraction Studies of Catalyst Structure and Binding

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High-rate lithium ion energy storage to facilitate increased penetration of photovoltaic systems in electricity grids

High-rate lithium ion batteries can play a critical role in decarbonizing our energy systems both through their underpinning of the transition to use renewable energy resources such as photovoltaics and electrification of transport. Their ability to be rapidly and frequently charged and discharged can enable this energy storage technology to play a key role in facilitating future lowcarbon electricity networks and thereby limit emissions that may result from transport electrification if fossil fuels are required for battery production and charging. This decarbonizing transition will require lithium ion technology to provide increased power and longer cycle lives at reduced cost. Rate performance and cycle life are ultimately limited by the materials used and the kinetics associated with the charge transfer reactions, ionic and electronic conduction. We review materials strategies for electrode materials and electrolytes that can facilitate high rates and long cycle lives and explore the new opportunities that may arise in embedded distributed storage via devices that blur the distinction between supercapacitors and batteries.This work has been supported by the Australian Research Council (ARC) through grants DP170103219 and FT170100447 (Future Fellowship – Alison Lennon). Yu Jiang and Charles Hall acknowledge the support of the Australian Government through their Research Training Program Scholarships. Kent J. Griffith acknowledges funding from the Winston Churchill Foundation of the United States and a Herchel Smith Scholarship. Kent J. Griffith and Clare P. Grey thank the EPSRC for a LIBATT grant (EP/M009521/1). The views expressed herein are not necessarily the views of the Australian Government, and the Australian Government does not accept responsibility for any information or advice contained herein

Prospects for lithium-ion batteries and beyond-a 2030 vision.

It would be unwise to assume ‘conventional’ lithium-ion batteries are approaching the end of their era and so we discuss current strategies to improve the current and next generation systems, where a holistic approach will be needed to unlock higher energy density while also maintaining lifetime and safety. We end by briefly reviewing areas where fundamental science advances will be needed to enable revolutionary new battery systems

Superionic Lithium Intercalation through 2 x 2 nm(2) Columns in the Crystallographic Shear Phase Nb18W8O69

Nb18W8O69 (9Nb2O5·8WO3) is the tungsten-rich end-member of the Wadsley–Roth crystallographic shear (cs) structures within the Nb2O5–WO3 series. It has the largest block size of any known, stable Wadsley–Roth phase, comprising 5 × 5 units of corner-shared MO6 octahedra between the shear planes, giving rise to 2 × 2 nm2 blocks. Rapid lithium intercalation is observed in this new candidate battery material and 7Li pulsed field gradient nuclear magnetic resonance spectroscopy—measured in a battery electrode for the first time at room temperature—reveals superionic lithium conductivity with Li diffusivities at 298 K predominantly between 10–10 and 10–12 m2·s–1. In addition to its promising rate capability, Nb18W8O69 adds to our understanding of the large family of high-performance Wadsley–Roth complex metal oxides

Joint NMR and Diffraction Studies of Catalyst Structure and Binding

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The importance of electronic correlations in exploring the exotic phase diagram of layered Li_xMnO₂

Using ab initio dynamical mean-field theory we explore the electronic and magnetic states of layered Li$_x$MnO$_2$ as a function of $x$, the state of charge. Constructing real-space Wannier projections of Kohn-Sham orbitals based on the low-energy subspace of Mn $3d$ states and solving a multi-impurity problem, our approach focuses on local correlations at Mn sites. The antiferromagnetic insulating state in LiMnO$_2$ has a moderate N\'{e}el temperature of $T_N=296\,K$ in agreement with experimental studies. Upon delithiation the system proceeds through a number of states: ferrimagnetic correlated metals at $x$=0.92, 0.83; multiple charge disproportionated ferromagnetic correlated metals with large quasiparticle weights at $x$=0.67, 0.50, 0.33; ferromagnetic metals with small quasiparticle weights at $x$=0.17, 0.08 and an antiferromagnetic insulator for the fully delithiated state, $x=0.0$. At moderate states of charge, $x=0.67-0.33$, a mix of +3/+4 formal oxidation states of Mn is observed, while the overall nominal oxidation of Mn state changes from +3 in LiMnO$_2$ to +4 in MnO$_2$. In all these cases the high-spin state emerges as the most likely state in our calculations considering the full $d$~manifold of Mn based on the proximity of $e_g$ levels in energy to $t_{2g}$. The quasiparticle peaks in the correlated metallic states were attributed to polaronic states based on previous literature for similar isoelectronic JT driven materials, arising due to non-Fermi liquid type behaviour of the strongly correlated system

Importance of electronic correlations in exploring the exotic phase diagram of layered LixMnO2

Using ab initio dynamical mean-field theory we explore the electronic and magnetic states of layered LixMnO2 as a function of x, the state-of-charge. Constructing real-space Wannier projections of Kohn-Sham orbitals based on the low-energy subspace of Mn 3d states and solving a multi-impurity problem, our approach focuses on local correlations at Mn sites. The antiferromagnetic insulating state in LiMnO2 has a moderate Néel temperature of TN=296K in agreement with experimental studies. Upon delithiation the system proceeds through a number of states: ferrimagnetic correlated metals at x=0.92, 0.83; multiple charge disproportionated ferromagnetic correlated metals with large quasiparticle peaks at x=0.67, 0.50, 0.33; ferromagnetic metals with small quasiparticle peaks at x=0.17, 0.08 and an antiferromagnetic insulator for the fully delithiated state, x=0.0. At moderate states of charge, x=0.67-0.33, a mix of +3/+4 formal oxidation states of Mn is observed, while the overall nominal oxidation of Mn state changes from +3 in LiMnO2 to +4 in MnO2. In all these cases the high-spin state emerges as the most likely state in our calculations considering the full d manifold of Mn based on the proximity of eg levels in energy to t2g. We observe a crossover from coherent to incoherent behavior on delithiation as function of state-of-charge.</p

A 17O Paramagnetic NMR Study of Sm2O3, Eu2O3, and Sm-/Eu- Substituted CeO2

Paramagnetic solid-state NMR of lanthanide (Ln) containing materials can be challenging due to the high electron spin states possible for the Ln f electrons, which result in large paramagnetic shifts, and these difficulties are compounded for 17O due to the low natural abundance and quadrupolar character. In this work, we present examples of 17O NMR experiments for lanthanide oxides and strategies to overcome these difficulties. In particular, we record and assign the 17O NMR spectra of monoclinic Sm2O3 and Eu2O3 for the first time, as well as performing density functional theory (DFT) calculations to gain further insight into the spectra. The temperature dependence of the Sm3+ and Eu3+ magnetic susceptibilities are investigated by measuring the 17O shift of the cubic sesquioxides over a wide temperature range, which reveal non-Curie temperature dependence due to the presence of low-lying electronic states. This behaviour is reproduced by calculating the electron spin as a function of temperature, yielding shifts which agree well with the experimental values. Using the understanding of the magnetic behaviour gained from the sesquioxides, we then explore the local oxygen environments in 15 at% Sm- and Eu-substituted CeO2, with the 17O NMR spectrum exhibiting signals due to environments with zero, one and two nearest neighbour Ln ions, as well as further splitting due to oxygen vacancies. Finally, we extract an activation energy for oxygen vacancy motion in these systems of 0.35 ± 0.02 eV from the Arrhenius temperature dependence of the 17O T1 relaxation constants, which is found to be independent of the Ln ion within error. The relation of this activation energy to literature values for oxygen diffusion in Ln-substituted CeO2 is discussed to infer mechanistic information which can be applied to further develop these materials as solid-state oxide-ion conductors.Oppenheimer Foundation. NECCES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DE-SC0012583. Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility Scientific Data and Computing Center, a component of the Computational Science Initiative, at Brookhaven National Laboratory, under Contract No. DE-SC001270

First-Principles Study of Localised and Delocalised Electronic States in Crystallographic Shear Phases of Niobium Oxide

Crystallographic shear phases of niobium oxide form an interesting family of compounds that have received attention both for their unusual electronic and magnetic properties, as well as their performance as intercalation electrode materials for lithium-ion batteries. Here, we present a first-principles density-functional theory study of the electronic structure and magnetism of H-Nb$_2$O$_5$, Nb$_{25}$O$_{62}$, Nb$_{47}$O$_{116}$, Nb$_{22}$O$_{54}$, and Nb$_{12}$O$_{29}$. These compounds feature blocks of niobium-oxygen octahedra as structural units, and we show that this block structure leads to a coexistence of flat and dispersive energy bands, corresponding to localised and delocalised electronic states. Electrons localise in orbitals spanning multiple niobium sites in the plane of the blocks. Localised and delocalised electronic states are both effectively one-dimensional and are partitioned between different types of niobium sites. Flat bands associated with localised electrons are present even at the GGA level, but a correct description of the localisation requires the use of GGA+U or hybrid functionals. We discuss the experimentally observed electrical and magnetic properties of niobium suboxides in light of our results, and argue that their behaviour is similar to that of $n$-doped semiconductors, but with a limited capacity for localised electrons. When a threshold of one electron per block is exceeded, metallic electrons are added to existing localised electrons. We propose that this behaviour of shear phases is general for any type of $n$-doping, and should transfer to doping by alkali metal (lithium) ions during operation of niobium oxide-based battery electrodes. Future directions for theory and experiment on mixed-metal shear phases are suggested