Structural and Mechanistic Insights into Fast Lithium-Ion Conduction in Li4SiO4–Li3PO4 Solid Electrolytes

Deng, Yue; Eames, C.; Chotard, Jean‐Noël; Lalère, Fabien; Seznéc, Vincent; Emge, Steffen P.; Pecher, Oliver; Grey, Clare P.; Masquelier, Christian; Islam, M. Saïful

doi:10.1021/jacs.5b04444

Cited by 242 publications

(237 citation statements)

References 71 publications

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“…In addition to lithium garnet and NASICON SICs, this mechanism is observed in other SIC materials, such as Li 7 P 3 S 11 , β-Li 3 PS 4 , LISICON, Li x La 2/3− x /3 TiO 3 (LLTO) perovskite25, and Na + -conducting NASICON, where high-energy sites are occupied along the diffusion path and the concerted migration with low energy barrier is confirmed in ab initio modelling (Supplementary Note 5 and Supplementary Figs 6–11). The concerted migration of multiple ions is also reported for low-barrier diffusion in other Li ionic conductors, for example, Li 3 OX (X=Cl, Br)26 and doped Li 3 PO 4 (refs 27, 28). In addition to Li + and Na + conductors, our proposed model is generally applicable to conductors of other ions.…”

Section: Discussionmentioning

confidence: 57%

Origin of fast ion diffusion in super-ionic conductors

2017

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Super-ionic conductor materials have great potential to enable novel technologies in energy storage and conversion. However, it is not yet understood why only a few materials can deliver exceptionally higher ionic conductivity than typical solids or how one can design fast ion conductors following simple principles. Using ab initio modelling, here we show that fast diffusion in super-ionic conductors does not occur through isolated ion hopping as is typical in solids, but instead proceeds through concerted migrations of multiple ions with low energy barriers. Furthermore, we elucidate that the low energy barriers of the concerted ionic diffusion are a result of unique mobile ion configurations and strong mobile ion interactions in super-ionic conductors. Our results provide a general framework and universal strategy to design solid materials with fast ionic diffusion.

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Section: Discussionmentioning

confidence: 57%

Origin of fast ion diffusion in super-ionic conductors

2017

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“…Our previous work [43,44] and that of some others [45][46][47] verified that correlated jumps lead to lower energy barriers and higher ion conductivity in some fast ion conductors, for example, Li 3 OX (X = Cl, Br), [45] doped Li 3 PO 4 , [46] and Li 7 La 3 Zr 2 O 12 (LLZO). Our previous work [43,44] and that of some others [45][46][47] verified that correlated jumps lead to lower energy barriers and higher ion conductivity in some fast ion conductors, for example, Li 3 OX (X = Cl, Br), [45] doped Li 3 PO 4 , [46] and Li 7 La 3 Zr 2 O 12 (LLZO).…”

Section: Na + -Ion Dynamics In Nasicon Materialsmentioning

confidence: 53%

Correlated Migration Invokes Higher Na⁺‐Ion Conductivity in NaSICON‐Type Solid Electrolytes

Zhang

Zou

Kaup

et al. 2019

Advanced Energy Materials

190

223

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Na super ion conductor (NaSICON), Na 1+n Zr 2 Si n P 3-n O 12 is considered one of the most promising solid electrolytes; however, the underlying mechanism governing ion transport is still not fully understood. Here, the existence of a previously unreported Na5 site in monoclinic Na 3 Zr 2 Si 2 PO 12 is unveiled. It is revealed that Na + -ions tend to migrate in a correlated mechanism, as suggested by a much lower energy barrier compared to the single-ion migration barrier. Furthermore, computational work uncovers the origin of the improved conductivity in the NaSICON structure, that is, the enhanced correlated migration induced by increasing the Na + -ion concentration. Systematic impedance studies on doped NaSICON materials bolster this finding. Significant improvements in both the bulk and total ion conductivity (e.g., σ bulk = 4.0 mS cm −1 , σ total = 2.4 mS cm −1 at 25 °C) are achieved by increasing the Na content from 3.0 to 3.30-3.55 mol formula unit −1 . These improvements stem from the enhanced correlated migration invoked by the increased Coulombic repulsions when more Na + -ions populate the structure rather than solely from the increased mobile ion carrier concentration. The studies also verify a strategy to enhance ion conductivity, namely, pushing the cations into high energy sites to therefore lower the energy barrier for cation migration.

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“…The values of s i for Li 4 It is possible to use molecular dynamics results in a more quantitative analysis of ionic conductivity following the approach implemented by Mo, Ong, and others. [32][33][34][35] For a molecular dynamics simulation at temperature T with resultant ion trajectories {r i (t)} as a function of time t, one can calculate the mean squared displacement and use Einstein's expression to determine the diffusion constant D trace (T ):…”

Section: Molecular Dynamics Simulationsmentioning

confidence: 99%

“…The simulation results reported here should be regarded as preliminary, due to the relatively small number of configurations sampled. Previous work of this sort [32][33][34][35] was based on simulation times 10-100 times as long as our 3-8 ps simulations. For these reasons, the least squares fit lines through the simulated results for log(T σ) versus 1000/T should be considered with large error bars.…”

Section: Molecular Dynamics Simulationsmentioning

confidence: 99%

Li₄SnS₄and Li₄SnSe₄: Simulations of Their Structure and Electrolyte Properties

Al-Qawasmeh

Howard

Holzwarth

2017

J. Electrochem. Soc.

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Recent experimental literature reports the solid state electrolyte properties of Li 4 SnS 4 and Li 4 SnSe 4 , identifying interesting questions regarding their structural details and motivating our first principles simulations. Together with Li 4 GeS 4 , these materials are all characterized by the orthorhombic space group Pnma and are found to be isostructural. They have a ground state crystal structure (denoted Li 4 SnS 0 4 ) having interstitial sites in void channels along the c-axis. They also have a meta-stable structure (denoted Li 4 SnS * 4 ) which is formed by moving one fourth of the Li ions from their central sites to the interstitial positions, resulting in a 0.5 Å contraction of the a lattice parameter. Relative to their ground states, the meta-stable structures are found to have energies 0.25 eV, 0.02 eV, and 0.07 eV for Li 4 From this literature, some interesting questions arise regarding crystal structures and mechanisms for ion mobility. In order to address these questions, we use first principles methods to examine the ideal crystal forms and defect structures of Li 4 SnS 4 and the structurally and chemically related materials Li 4 GeS 4 and Li 4 SnSe 4 . For each of these materials, we identify two closely related structures -an ideal ground state structure and an ideal meta-stable structure. The simulations show that the meta-stable structural form is most accessible to Li 4 SnS 4 of the three materials studied. The simulations are extended to study mechanisms of Li ion migration in both Li 4 SnS 4 and Li 4 SnSe 4 and are related to the experimental results reported in the literature. Computational MethodsThe computational methods used in this work are based on density functional theory (DFT), 8,9 using the projected augmented wave (PAW) 10 formalism. The PAW basis and projector functions were generated by the ATOMPAW 11 code and the crystalline materials were modeled using the QUANTUM ESPRESSO 12 and ABINIT 13 packages. Visualizations were constructed using the XCrySDEN, 14 The exchange correlation function is approximated using the localdensity approximation (LDA). 17 The choice of LDA functional was made based on previous investigations 18-20 of similar materials which showed that, provided that the lattice constants are scaled by a correction factor of 1.02, the simulations are in good agreement with experiment, especially lattice vibrational frequencies and heats of formation. The partial densities of states were calculated as described in previous work, 20,21 using weighting factors based on the charge within the augmentation spheres of each atom with radii r The calculations were well converged with plane wave expansions of the wave function including |k + G| 2 ≤ 64 bohr −2 . Calculations for the conventional unit cells were performed using a Brillouin-zone sampling grid of 4 × 8 × 8. Simulations of Li ion migration were performed at constant volume in supercells constructed from the optimized conventional cells extended by 1 × 2 × 2 and a Brillouin-zone sampling grid of 2 × 2 × 2. In ...

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Structural and Mechanistic Insights into Fast Lithium-Ion Conduction in Li₄SiO₄–Li₃PO₄ Solid Electrolytes

Cited by 242 publications

References 71 publications

Origin of fast ion diffusion in super-ionic conductors

Origin of fast ion diffusion in super-ionic conductors

Correlated Migration Invokes Higher Na⁺‐Ion Conductivity in NaSICON‐Type Solid Electrolytes

Li₄SnS₄and Li₄SnSe₄: Simulations of Their Structure and Electrolyte Properties

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Structural and Mechanistic Insights into Fast Lithium-Ion Conduction in Li4SiO4–Li3PO4 Solid Electrolytes

Cited by 242 publications

References 71 publications

Origin of fast ion diffusion in super-ionic conductors

Origin of fast ion diffusion in super-ionic conductors

Correlated Migration Invokes Higher Na+‐Ion Conductivity in NaSICON‐Type Solid Electrolytes

Li4SnS4and Li4SnSe4: Simulations of Their Structure and Electrolyte Properties

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Structural and Mechanistic Insights into Fast Lithium-Ion Conduction in Li₄SiO₄–Li₃PO₄ Solid Electrolytes

Correlated Migration Invokes Higher Na⁺‐Ion Conductivity in NaSICON‐Type Solid Electrolytes

Li₄SnS₄and Li₄SnSe₄: Simulations of Their Structure and Electrolyte Properties