Analysis of Diffusion in Solid-State Electrolytes through MD Simulations, Improvement of the Li-Ion Conductivity in β‑Li3PS4 asan Example

Molecular dynamics simulations are a powerful tool to study diffusion processes in battery electrolyte andelectrode materials. From molecular dynamics simulations, manyproperties relevant to diffusion can be obtained, including thediffusion path, amplitude of vibrations, jump rates, radial distribution functions, and collective diffusion processes. Hereit is shown how the activation energies of different jumps and theattempt frequency can be obtained from a single moleculardynamics simulation. These detailed diffusion properties providea thorough understanding of diffusion in solid electrolytes, andprovide direction for the design of improved solid electrolytematerials. The presently developed analysis methodology isapplied to DFT MD simulations of Li-ion diffusion in β-Li3PS4.The methodology presented is generally applicable to diffusion in crystalline materials and facilitates the analysis of moleculardynamics simulations. The code used for the analysis is freely available at: https://bitbucket.org/niekdeklerk/md-analysis-withmatlab. The results on β−Li3PS4 demonstrate that jumps between bc planes limit the conductivity of this important class of solid electrolyte materials. The simulations indicate that the rate-limiting jump process can be accelerated significantly by adding Li interstitials or Li vacancies, promoting three-dimensional diffusion, which results in increased macroscopic Li-iondiffusivity. Li vacancies can be introduced through Br doping, which is predicted to result in an order of magnitude larger Li-ionconductivity in β−Li3PS4. Furthermore, the present simulations rationalize the improved Li-ion diffusivity upon O dopingthrough the change in Li distribution in the crystal. Thus, it is demonstrated how a thorough understanding of diffusion, based on thorough analysis of MD simulations, helps to gain insight and develop strategies to improve the ionic conductivity of solid electrolytes.RST/Storage of Electrochemical Energ

Investigation of Structure, Ionic Conductivity, and Electrochemical Stability of Halogen Substitution in Solid-State Ion Conductor Li₃YBr_xCl_{6- x}

Li3YX6(X = Cl, Br) materials are Li-ion conductors that can be used as solid electrolytes in all solid-state batteries. Solid electrolytes ideally have high ionic conductivity and (electro)chemical compatibility with the electrodes. It was proven that introducing Br to Li3YCl6increases ionic conductivity but, according to thermodynamic calculations, should also reduce oxidative stability. In this paper, the trade-off between ionic conductivity and electrochemical stability in Li3YBrxCl6-xhalogen-substituted compounds is investigated. The compositions of Li3YBr1.5Cl4.5and Li3YBr4.5Cl1.5are reported for the first time, along with a consistent analysis of the whole Li3YBrxCl6-x(x = 0-6) tie-line. The results show that, while Br-rich materials are more conductive (5.36 × 10-3S/cm at 30 °C for x = 4.5), the oxidative stability is lower (∼ 3 V compared to ∼ 3.5 V). Small Br content (x = 1.5) does not affect oxidative stability but substantially increases ionic conductivity compared to pristine Li3YCl6(2.1 compared to 0.049 × 10-3S/cm at 30 °C). This work highlights that optimization of substitutions in the anion framework provide prolific and rational avenues for tailoring the properties of solid electrolytes.RST/Storage of Electrochemical EnergyBN/Cees Dekker LabRID/TS/Technici PoolRID/TS/Instrumenten groe

Quantification of the Li-ion diffusion over an interface coating in all-solid-state batteries via NMR measurements

A key challenge for solid-state-batteries development is to design electrode-electrolyte interfaces that combine (electro)chemical and mechanical stability with facile Li-ion transport. However, while the solid-electrolyte/electrode interfacial area should be maximized to facilitate the transport of high electrical currents on the one hand, on the other hand, this area should be minimized to reduce the parasitic interfacial reactions and promote the overall cell stability. To improve these aspects simultaneously, we report the use of an interfacial inorganic coating and the study of its impact on the local Li-ion transport over the grain boundaries. Via exchange-NMR measurements, we quantify the equilibrium between the various phases present at the interface between an S-based positive electrode and an inorganic solid-electrolyte. We also demonstrate the beneficial effect of the LiI coating on the all-solid-state cell performances, which leads to efficient sulfur activation and prevention of solid-electrolyte decomposition. Finally, we report 200 cycles with a stable capacity of around 600 mAh g−1 at 0.264 mA cm−2 for a full lab-scale cell comprising of LiI-coated Li2S-based cathode, Li-In alloy anode and Li6PS5Cl solid electrolyte.RST/Storage of Electrochemical EnergyInstrumenten groe

Author Correction: Quantification of the Li-ion diffusion over an interface coating in all-solid-state batteries via NMR measurements (Nature Communications, (2021), 12, 1, (5943), 10.1038/s41467-021-26190-2)

The original version of this article contained errors in Figure 3a and Figure 3f. In Figure 3a, the activation energies (Ea) were calculated using a log scale instead of a logarithm ln scale. In Figure 3f, the y-axis interval was not properly selected. The correct y-axis interval in Figure 3f and the numerical values of the activation energy are now provided in Figure 3a and the main text. These errors have been corrected in the HTML and PDF versions of the article.Corrections & amendments DOI 10.1038/s41467-021-26190-2RST/Storage of Electrochemical EnergyRID/TS/Instrumenten groe

Re-investigating the structure-property relationship of the solid electrolytes Li _3−xIn_1−xZr_xCl₆ and the impact of In-Zr(iv) substitution

Chloride-based solid electrolytes are considered interesting candidates for catholytes in all-solid-state batteries due to their high electrochemical stability, which allows the use of high-voltage cathodes without protective coatings. Aliovalent Zr(iv) substitution is a widely applicable strategy to increase the ionic conductivity of Li3M(iii)Cl6 solid electrolytes. In this study, we investigate how Zr(iv) substitution affects the structure and ion conduction in Li3−xIn1−xZrxCl6 (0 ≤ x ≤ 0.5). Rietveld refinement using both X-ray and neutron diffraction is used to make a structural model based on two sets of scattering contrasts. AC-impedance measurements and solid-state NMR relaxometry measurements at multiple Larmor frequencies are used to study the Li-ion dynamics. In this manner the diffusion mechanism and its correlation with the structure are explored and compared to previous studies, advancing the understanding of these complex and difficult to characterize materials. It is found that the diffusion in Li3InCl6 is most likely anisotropic considering the crystal structure and two distinct jump processes found by solid-state NMR. Zr-substitution improves ionic conductivity by tuning the charge carrier concentration, accompanied by small changes in the crystal structure which affect ion transport on short timescales, likely reducing the anisotropy.RST/Storage of Electrochemical EnergyRID/TS/Instrumenten groe

A Series of Ternary Metal Chloride Superionic Conductors for High-Performance All-Solid-State Lithium Batteries

Understanding the relationship between structure, ionic conductivity, and synthesis is the key to the development of superionic conductors. Here, a series of Li3-3xM1+xCl6 (−0.14 < x ≤ 0.5, M = Tb, Dy, Ho, Y, Er, Tm) solid electrolytes with orthorhombic and trigonal structures are reported. The orthorhombic phase of Li–M–Cl shows an approximately one order of magnitude increase in ionic conductivities when compared to their trigonal phase. Using the Li–Ho–Cl components as an example, their structures, phase transition, ionic conductivity, and electrochemical stability are studied. Molecular dynamics simulations reveal the facile diffusion in the z-direction in the orthorhombic structure, rationalizing the improved ionic conductivities. All-solid-state batteries of NMC811/Li2.73Ho1.09Cl6/In demonstrate excellent electrochemical performance at both 25 and −10 °C. As relevant to the vast number of isostructural halide electrolytes, the present structure control strategy guides the design of halide superionic conductors.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Storage of Electrochemical EnergyPhotovoltaic Materials and DevicesRID/TS/Instrumenten groe