First-principles investigation of phase stability in Li x CoO 2
TL;DR: In this article, the phase diagram of a staged compound is calculated from first principles for x ranging from 0 to 1 and it is shown that there is a tendency for Li ordering at $x=\frac{1}{2}$ in agreement with experiment [J. N. Reimers and J. R. Dahn, 1992].
Abstract: In this work, the phase diagram of ${\mathrm{Li}}_{x}{\mathrm{CoO}}_{2}$ is calculated from first principles for x ranging from 0 to 1. Our calculations indicate that there is a tendency for Li ordering at $x=\frac{1}{2}$ in agreement with experiment [J. N. Reimers and J. R. Dahn, J. Electrochem. Soc. 139, 2091 (1992)]. At low Li concentration, we find that a staged compound is stable in which the Li ions selectively segregate to every other Li plane leaving the remaining Li planes vacant. We do not find the two-phase region observed at high Li concentration and speculate that this two-phase region is caused by the metal-insulator transition that occurs at concentrations slightly below $x=1.$
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TL;DR: The implementation of various DFT functionals and many‐body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures are discussed.
Abstract: During the past decade, computer simulations based on a quantum-mechanical description of the interactions between electrons and between electrons and atomic nuclei have developed an increasingly important impact on solid-state physics and chemistry and on materials science—promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within density-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calculations and structural optimizations for systems with thousands of atoms and ab initio molecular dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mechanical and dynamical properties, liquids, glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chemical reactions, and catalysis) are reviewed. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008
2,364 citations
TL;DR: A new electrode material, P2-Na(2/3)[Fe(1/2)Mn( 1/2)]O(2), that delivers 190 mAh g(-1) of reversible capacity in the sodium cells with the electrochemically active Fe(3+)/Fe(4+) redox will contribute to the development of rechargeable batteries from the earth-abundant elements operable at room temperature.
Abstract: Although sodium is an abundant element that can be electrochemically and reversibly extracted from and inserted into layered materials, the resulting reversible capacity for storing energy remains low. A manganese–iron–sodium-based electrode is now shown to exhibit a reversible capacity of 190 mAh g−1 due to electrochemically active Fe3+/Fe4+ redox reactions.
1,834 citations
TL;DR: A comprehensive survey of conduction phenomena in all components of a Li-ion cell incorporating theoretical, experimental, and simulation studies is presented in this paper, where the critical results, issues and challenges with respect to ionic and electronic conduction in the cathode, anode and electrolyte are discussed.
1,394 citations
TL;DR: A concise user guide is presented outlining the steps required to obtain thermodynamic information from ab initio calculations of alloy thermodynamic properties from first-principles.
Abstract: Although the formalism that allows the calculation of alloy thermodynamic properties from
first-principles has been known for decades, its practical implementation has so far remained a tedious
process. The Alloy Theoretic Automated Toolkit (ATAT) drastically simplifies this procedure by implementing
decision rules based on formal statistical analysis that frees the researchers from a constant
monitoring during the calculation process and automatically “glues” together the input and the output of
various codes, in order to provide a high-level interface to the calculation of alloy thermodynamic properties
from first-principles. ATAT implements the Structure Inversion Method (SIM), also known as the
Connolly-Williams method, in combination with semi-grand-canonical Monte Carlo simulations. In order
to make this powerful toolkit available to the wide community of researchers who could benefit from it,
this article present a concise user guide outlining the steps required to obtain thermodynamic information
from ab initio calculations.
1,001 citations
Cites background from "First-principles investigation of p..."
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...A typical well-converged cluster expansion of the energy of an alloy consists of about 10 to 20 ECI and necessitates the calculation of the energy of around 30 to 50 ordered structures (see, for instance, [25, 9, 17])....
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TL;DR: Using ab initio computations, it is demonstrated that this unexpected behavior of the flow of lithium ions into and out of battery electrodes is due to percolation of a certain type of active diffusion channels in disordered Li-excess materials.
Abstract: Nearly all high energy density cathodes for rechargeable lithium batteries are well-ordered materials where lithium and other cations occupy distinct sites. Cation-disordered materials are generally disregarded as cathodes because lithium diffusion tends to be limited by their structures. The performance of Li1.211Mo0.467Cr0.3O2 shows that lithium diffusion can be facile in disordered materials. Using ab initio computations, we demonstrate that this unexpected behavior is due to percolation of certain diffusion channels that are active in disordered structures, but is unique to Li excess materials. This leads to a unified understanding of high performance in both layered and Li excess materials, and opens up an exciting new direction for designing disordered electrode materials with high capacity and high energy density.
877 citations