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

The stability and redox mechanisms of Ni-rich NMC cathodes:Insights from first-principles many-body calculations

Ni-rich LiNi_aMn_bCo_cO_2 (NMC) cathodes undergo a series of degradation reactions, a prominent one being oxygen loss from the surface of the NMC particles, this process being more pronounced as Ni content is increased and at high voltages. Our first-principles study examines the redox behavior of transition metals and O in Ni-rich NMC cathodes as a function of (de)lithiation. We use ab initio multiple scattering, density-functional theory (DFT) based core-loss spectroscopy, and dynamical mean-field theory (DMFT) to give a many-body treatment of both dynamic and static correlations. Despite Ni, Mn, and Co K-edges calculated using ab initio multiple scattering based on Green's functions showing an excellent match with experimentally obtained X-ray absorption near-edge spectra (XANES), we demonstrate that the ionic model of ascribing shifts in the XANES spectra to changes in metal oxidation states is inappropriate. We show that in these cases, which are characterised by strong covalency between the transition metal and oxygen, DMFT calculations based on Wannier projections are essential to calculate charges and hence assign oxidation states accurately. Due to the corresponding charge transfer from O p to Ni d, a ligand hole forms on O in Ni-rich regions. The individual Ni charge remains fairly constant throughout the charging/discharging process, particularly in Ni-rich environments in the material. In contrast, O has dual redox behavior, showing greater involvement in redox in Ni-rich regions while showing negligible redox involvement in Ni-poor regions. The Ni-O covalent system starts participating in redox around a state of delithiation of ~17%, which represents, in our system, the beginning of charge. Contrary to previous DFT calculations, we show that Co oxidation does not occur at the very end of charge but rather starts at an earlier state of delithiation of ~67%. The dual behaviour of O in terms of participation in the redox process helps explain the overall higher relative stability of lower Ni content NMCs compared to Ni-rich NMCs or LiNiO_2 in terms of O loss and evolution of singlet oxygen

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

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