Solid State Ionic Conductors Research Articles

Formation of Na-O bonds in NaZn(BH4)3·xTHF for enhancing sodium conductivity

Developing high-performance solid-state batteries requires solid electrolytes with high ionic conductivity and excellent electrode compatibility. This study focuses on bimetallic borohydride NaZn(BH4)3·xTHF, revealing a room temperature sodium conductivity of 1.89 × 10−5 S cm−1 due to the formation of Na-O bonds. This THF-involved NaZn(BH4)3 was synthesized in a THF solution without ball milling. Our investigation highlights the key role of THF in determining the crystal structure of NaZn(BH4)3·xTHF, which adopts a space group of P2/m. In-situ X-ray diffraction reveals that removing THF from NaZn(BH4)3 under dynamic vacuum conditions leads to a gradual transformation of the crystal structure from space group P2/m to P21/c. X-ray Absorption Fine Structure (XAFS), Pair Distribution Function (PDF), and Far-Infrared analysis illustrate the coordination of THF to NaZn(BH4)3 in the form of Na-O bonds. The DSC results suggest that dynamic desorption and adsorption of THF play an active role in Na+ migration, with the movement of THF creates sodium defects/vacancies that promote Na+ migration. This outstanding property offers attractive prospects for designing bimetallic borohydrides as novel solid-state sodium ion conductors.

Investigation of Ceria based Heterostructure Composite Mixed Matrix Membrane with Polybenzimidazole for Polymer Electrolyte Fuel Cell Application at High Temperature

In recent years Ceria based heterostructure composites are considered as one of the highest performing solid state ionic conductors, therefore we wanted to leverage the benefits of using these materials for high temperature Proton Exchange Membrane Fuel Cells (PEMFCs). In this study a Polybenzimidazole (PBI)/Ceria carbonate CHC (Ceria based heterostructure composite) membrane was prepared by drop casting method and tested as an electrolyte for a high temperature H2/Air PEMFC application in anhydrous condition. Inorganic composite of ceria and alkali metal carbonates (Li2CO3, Na2CO3) was prepared by solid state route to obtain Ceria carbonate CHC. X-Ray diffraction (XRD) study confirmed the formation of the heterostructure and their successful incorporation into the PBI membranes. Homogeneity of fillers inside the membrane was further verified by Energy Dispersive X-Ray Analysis (EDAX) and Scanning Electron Microscopy (SEM). 5wt% of inorganic powder induced inside the PBI fillers reduced the phosphoric acid uptake of composite membrane (∼17% less) compared to pristine PBI membrane, which ultimately resulted into a lower swelling and dimensional change of the composite membrane. Thermal robustness of the phosphoric acid doped composite and pristine PBI membranes was investigated by thermogravimetric analysis (TGA) which showed that the prepared membranes were gone under a less than 10% reduction in weight up till 200ºC, ensuring their validity of application in high temp PEM fuel cells. The added inorganic functionalities resulted in a slight increase in the proton conductivity of PA doped composite PBI membranes i.e., 42.3 mS cm-1 at 180 ºC while for pristine PBI membrane it is 36 mS cm-1 at same temperature. A single cell with composite PBI membranes outperformed a pristine PBI membrane resulted into a ∼120% higher peak power density i.e., 320.88 mW cm-2. The composite membrane also displayed the excellent durability and showed a less than 10-4 mV/h degradation in cell potential till 180 ºC.

Rapid Characterization of Point Defects in Solid-State Ion Conductors Using Raman Spectroscopy, Machine-Learning Force Fields, and Atomic Raman Tensors.

The successful design of solid-state photo- and electrochemical devices depends on the careful engineering of point defects in solid-state ion conductors. Characterization of point defects is critical to these efforts, but the best-developed techniques are difficult and time-consuming. Raman spectroscopy─with its exceptional speed, flexibility, and accessibility─is a promising alternative. Raman signatures arise from point defects due to local symmetry breaking and structural distortions. Unfortunately, the assignment of these signatures is often hampered by a shortage of reference compounds and corresponding reference spectra. This issue can be circumvented by calculation of defect-induced Raman signatures from first principles, but this is computationally demanding. Here, we introduce an efficient computational procedure for the prediction of point defect Raman signatures in solid-state ion conductors. Our method leverages machine-learning force fields and "atomic Raman tensors", i.e., polarizability fluctuations due to motions of individual atoms. We find that our procedure reduces computational cost by up to 80% compared to existing first-principles frozen-phonon approaches. These efficiency gains enable synergistic computational-experimental investigations, in our case allowing us to precisely interpret the Raman spectra of Sr(Ti0.94Ni0.06)O3-δ, a model oxygen ion conductor. By predicting Raman signatures of specific point defects, we determine the nature of dominant defects and unravel impacts of temperature and quenching on in situ and ex situ Raman spectra. Specifically, our findings reveal the temperature-dependent distribution and association behavior of oxygen vacancies and nickel substitutional defects. Overall, our approach enables rapid Raman-based characterization of point defects to support defect engineering in novel solid-state ion conductors.

A theoretical perspective on solid-state ionic interfaces.

Solid-state ionic conductors find application across various domains in materials science, particularly showcasing their significance in energy storage and conversion technologies. To effectively utilize these materials in high-performance electrochemical devices, a comprehensive understanding and precise control of charge carriers' distribution and ionic mobility at interfaces are paramount. A major challenge lies in unravelling the atomic-level processes governing ion dynamics within intricate solid and interfacial structures, such as grain boundaries and heterophases. From a theoretical viewpoint, in this Perspective article, my focus is to offer an overview of the current comprehension of key aspects related to solid-state ionic interfaces, with a particular emphasis on solid electrolytes for batteries, while providing a personal critical assessment of recent research advancements. I begin by introducing fundamental concepts for understanding solid-state conductors, such as the classical diffusion model and chemical potential. Subsequently, I delve into the modelling of space-charge regions, which are pivotal for understanding the physicochemical origins of charge redistribution at electrified interfaces. Finally, I discuss modern computational methods, such as density functional theory and machine-learned potentials, which offer invaluable tools for gaining insights into the atomic-scale behaviour of solid-state ionic interfaces, including both ionic mobility and interfacial reactivity aspects. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Modular MPS3-Based Frameworks for Superionic Conduction of Monovalent and Multivalent Ions.

Next-generation batteries based on more sustainable working ions could offer improved performance, safety, and capacity over lithium-ion batteries while also decreasing the cost. Development of next-generation battery technology using "beyond-Li" mobile ions, especially multivalent ions, is limited due to a lack of understanding of solid state conduction of these ions. Here, we introduce ligand-coordinated ions in MPS3-based (M = Mn, Cd) solid host crystals to simultaneously increase the size of the interlayer spacing, through which the ions can migrate, and screen the charge-dense ions. The ligand-assisted conduction mechanism enables ambient temperature superionic conductivity of various next-generation mobile ions in the electronically insulating MPS3-based solid. Without the coordinating ligands, all of the compounds show little to no ionic conductivity. Pulsed-field gradient nuclear magnetic resonance spectroscopy suggests that the ionic conduction occurs through a hopping mechanism, where the cations are moving between H2O molecules, instead of a vehicular mechanism which has been observed in other hydrated layered solids. This modular system not only facilitates tailoring to different potential applications but also enables us to probe the effect of different host structures, mobile ions, and coordinating ligands on the ionic conductivity. This research highlights the influence of cation charge density, diffusion channel size, and effective charge screening on ligand-assisted solid state ionic conductivity. The insights gained can be applied in the design of other ligand-assisted solid state ionic conductors, which will be especially impactful in realizing solid state multivalent ionic conductors. Additionally, the ion-intercalated MPS3-based frameworks could potentially serve as a universal solid state electrolyte for various next-generation battery chemistries.

Water-mediated super-correlated proton-assisted transport mode for solid-state K−O2 batteries

A comprehensive understanding of the behavior nature of fast ions at the atomic level is essential for the development of advanced solid-state ionic conductors. The inadequate inter-ion correlation effects of current ion transport models lead to a conductivity bottleneck in designing conductors. Herein, based on water-mediated proton-assisted ion transport, a novel transport mode with simultaneous anion-cation and inter-cation coupling is designed, enabling the K-ions of the modeled solid-state ionic conductor K2Fe4O7 crystals to achieve an ultra-high conductivity of 7.6 × 10–2 S cm–1, an enhancement of two orders of magnitude. The principle of the accelerated K-ion diffusion through the rotation and vibration of water molecules around the framework oxygen atom is elaborated, and the coupling correlation between proton and K-ion transport is confirmed using in-situ impedance spectroscopy under labeled isotopes. The application of this mechanism enabled the fabricated K−O2 solid-state battery exhibit an ultra-low overpotential (0.1 V) and excellent rate performance. Further, the mechanism is also applicable for Li and Na-ion conductors, providing significant theoretical guidance for breaking existing universal design rules and for the development for faster ionic conductors.

(Invited) Experimentally Measuring the Role of Ion-Phonon and Ion-Electron Correlations in Solid-State Li Ion Conductors

In superionic conductors, ion hopping involves a complex interplay of ion-phonon, ion-electron, and ion-ion correlations that is challenging to measure experimentally. In this presentation, we present a new experimental technique that can directly measure ultrafast ion hopping on its inherent picosecond and longer timescale. The technique works by measuring the time-resolved perturbation to a GHz impedance signal when potential ion-coupling interactions are driven with UV to THz irradiation. High-bandwidth, real-time electronics allow synchronization of the impedance measurement to ultrafast laser pulses for varying carrier frequencies. The result of the measurement is the relative strength of different correlations in the many-body ion hopping Hamiltonian. We demonstrate the technique on Li0.5La0.5TiO3 (LLTO) and single crystalline Li7La3Zr2O12 (LLZO), both solid-state Li+ conductors. The ultrafast laser-driven impedance measurements reveal that the dominant ion hopping mechanism in LLTO is through a coupled phonon-ion THz rocking mode. Although this higher frequency mode is less than one-quarter of the overall phonon density of states, it leads to the majority of ion hops as compared to other optical and acoustic phonon modes. Metastable states lasting tens of minutes were also measured for ion-electron perturbations. Further work on extending the technique to measure ion-ion correlations is currently underway. In general, the new technique applies to any complex ion conducting system such as polymers, fuel cells, supercapacitors, and membranes.

Crystallization and the liquid-liquid critical point in nonbonded modified-WAC models.

For decades, it has been known that Liquid-Liquid Critical Points (LLCPs) can exist in one-component liquids, yet a comprehensive understanding of the conditions under which they arise remains elusive. To better comprehend the possible interplay between the LLCP and the crystalline phase, we conduct molecular dynamics simulations using the nonbonded family of modified-WAC (mWAC) models, which are known to exhibit a LLCP for certain parameter values. By comparing different versions of the mWAC model-those featuring a LLCP and those lacking one-we identify several key differences between the models relating to crystallization. Those models that do have a LLCP are found to have multiple stable crystalline phases, one of them being a solid-state ionic conductor similar to superionic ice. Moreover, we find that for models that do not have a LLCP, the liquid becomes a glass at a larger range of temperatures, possibly preventing the occurrence of a LLCP. Further studies are required to determine if these results are general or model-specific.

Synthesis and characteristics of densified GDC-LSO composite as a new apatite-based electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFC)

Developing solid-state ionic conductors with desirable charge-transport efficiency and reasonable durability is a fundamental and long-lasting challenge for solid-oxide fuel cells (SOFCs). Ceria-based electrolytes, as one of the most common types of electrolytes for intermediate-temperature solid-oxide fuel cells (IT-SOFCs), offer a high surface-exchange coefficient and faster kinetics in the triple phase boundaries (TPBs); however, they suffer to some extent of electronic conductivity in the reducing atmosphere and gradual phase transitions. Here in this work, we have reported a novel co-doped IT-SOFC electrolyte composite combining the apatite structure of Lanthanum Silicate (LSO) with the fluorite structure of Gadolinium-doped Ceria (GDC), which showed a high ionic conductivity and a minimal electronic leak. The resulting GDC-LSO composite electrolyte also achieved an OCV (open-circuit voltage) of 1 V at 800 °C, implying a significant improvement in the OCV values reported for the typical ceria-based electrolytes (∼0.75 V). The sample was prepared using 40 wt% GDC and 60 wt% LSO (40GDC-60LSO) showed a maximum electrical conductivity of 25 mS cm−1 at 800 °C with good densification properties (>95 % relative density). The cell electrochemical performance measurement was conducted using a 3.0 vol% humified H2 stream at the anode side while the cathode side was exposed to the air at 800 °C. The interdiffusion of cations between La3+ in the LSO phase and Ce4+ and Gd3+ in the GDC phase was detected by XRD and EDX results after sintering samples at 1500 °C for 4 h using 0.5 wt% PVA or 0.5 wt% Ethyl cellulose (EC) as the binder. The proposed GDC-LSO composite could help better understand the influence of compositional constituents and processing variables on the densification and electrical properties of the electrolyte materials for the IT-SOFCs.

Laser-driven ultrafast impedance spectroscopy for measuring complex ion hopping processes.

Superionic conductors, or solid-state ion-conductors surpassing 0.01 S/cm in conductivity, can enable more energy dense batteries, robust artificial ion pumps, and optimized fuel cells. However, tailoring superionic conductors requires precise knowledge of ion migration mechanisms that are still not well understood due to limitations set by available spectroscopic tools. Most spectroscopic techniques do not probe ion hopping at its inherent picosecond timescale nor the many-body correlations between the migrating ions, lattice vibrational modes, and charge screening clouds-all of which are posited to greatly enhance ionic conduction. Here, we develop an ultrafast technique that measures the time-resolved change in impedance upon light excitation, which triggers selective ion-coupled correlations. We also develop a cost-effective, non-time-resolved laser-driven impedance method that is more accessible for lab-scale adoption. We use both techniques to compare the relative changes in impedance of a solid-state Li+ conductor Li0.5La0.5TiO3 (LLTO) before and after UV to THz frequency excitations to elucidate the corresponding ion-many-body-interaction correlations. From our techniques, we determine that electronic screening and phonon-mode interactions dominate the ion migration pathway of LLTO. Although we only present one case study, our technique can extend to O2-, H+, or other charge carrier transport phenomena where ultrafast correlations control transport. Furthermore, the temporal relaxation of the measured impedance can distinguish ion transport effects caused by many-body correlations, optical heating, correlation, and memory behavior.

Unveiling the Impact of Tailoring Ionic Conductor Characteristics on the Performance of Wearable Triboelectric Nanogenerators.

This work reveals the correlation between the performance of triboelectric nanogenerators (TENGs) and the characteristics of deformable solid-state ionic conductors (referred to as ionogels). For this purpose, we modify ionogel characteristics by incorporating additional plasticizers (propylene carbonate) and solid salts (lithium bis(trifluoromethylsulfonyl)imide) into the ionogels. We conclude that the high capacitance of the ionogel is crucial for achieving a high-performance TENG platform. The optimized ionogel-based TENG (i-TENG) exhibits a power density of ∼372.4 mW·m-2 (based on 95 V and 36 mA·m-2 outputs) with outstanding long-term stability over 2 weeks. Additionally, successful demonstrations of wearable nanogenerators are performed by leveraging the high stretchability (up to ∼1000%) and optical transparency (∼90%) of the ionogels. Overall, the results provide insight into the design of deformable ionic conductors for high-performance, reliable, and wearable TENGs.

Chlorine-Rich Na6-xPS5-xCl1+x: A Promising Sodium Solid Electrolyte for All-Solid-State Sodium Batteries.

Developing argyrodite-type, chlorine-rich, sodium-ion, solid-state electrolytes with high conductivity is a long-term challenge that is crucial for the advancement of all-solid-state batteries (ASSBs). In this study, chlorine-rich, argyrodite-type Na6-xPS5-xCl1+x solid solutions were successfully developed with a solid solution formation range of 0 ≤ x ≤ 0.5. Na5.5PS4.5Cl1.5 (x = 0.5), displaying a highest ionic conductivity of 1.2 × 10-3 S/cm at 25 °C, which is more than a hundred times higher than that of Na6PS5Cl. Cyclic voltammetry and electrochemical impedance spectroscopy results demonstrated that the rich chlorine significantly enhanced the ionic conductivity and electrochemical stability, in addition to causing a reduction in activation energy. The Na5.5PS4.5Cl1.5 composite also showed the characteristics of a pure ionic conductor without electronic conductivity. Finally, the viability of Na5.5PS4.5Cl1.5 as a sodium electrolyte for all-solid-state sodium batteries was checked in a lab-scale ASSB, showing stable battery performance. This study not only demonstrates new composites of sodium-ionic, solid-state electrolytes with relatively high conductivity but also provides an anion-modulation strategy to enhance the ionic conductivity of argyrodite-type sodium solid-state ionic conductors.

Bi6Te2-xRxO13 (R=Ti, Si, Ce) Systems: A Investigation for Fuel Cell Applications

In recent years, the increase of economic and environmental problems related to energy generation has increased researches at renewable energy sources. Among others, the fuel cells excel as promising alternative technology of electricity generation and materials science is an ally in the search for better and more efficient materials for this application. In particular, solid-state ionic conductors represent functional materials with promising advantages for fuel cells, as is the case of Bi2O3-based oxygen ion conductors, however, they need to have its cubic phase stabilized at room temperature. This paper presents a study of the Bi6Te2-xRxO13 (R = Ti, Si and Ce) systems for such an application. Solid state reaction was used to materials synthesis. The 3Bi2O3:2TeO2 system present two phases, an orthorhombic one (Bi6Te2O15) stable at room temperature and another high temperature cubic (Bi6Te2O13). Experiments of substitution of Te ions by Ti, Si and Ce ions using the Bi6Te2- xRxO13 matrix were done intending to stabilize the cubic phase at room temperature and the results are presented as well as discussed here.

Accurate description of ion migration in solid-state ion conductors from machine-learning molecular dynamics

Machine-learning molecular dynamics provides predictions of structural and anharmonic vibrational properties of solid-state ionic conductors with ab initio accuracy. This opens a path towards rapid design of novel battery materials.

Ionic conduction in ammonia functionalised closo-dodecaborates MB12H11NH3 (M = Li and Na).

Metal hydroborates and their derivatives have been receiving attention as potential solid-state ion conductors for battery applications owing to their impressive electrochemical and mechanical characteristics. However, to date only a fraction of these compounds has been investigated as solid-state electrolytes. Here, MB12H11NH3 (M = Li and Na) hydroborates are synthesized and investigated as electrolyte materials for all-solid-state batteries. The room temperature α-NaB12H11NH3 was structurally solved in P212121 (a = 7.1972(3) Å, b = 9.9225(4) Å, and c = 14.5556(5) Å). It shows a polymorphic structural transition near 140 °C to cubic Fm3̄m. LiB12H11NH3 and NaB12H11NH3 exhibit cationic conductivities of σ(Li+) = 3.0 × 10-4 S cm-1 and σ(Na+) = 1.2 × 10-4 S cm-1 at 200 °C. Hydration is found to improve ionic conductivity of the hydroborates. It is presumed that modest ionic conductivities could be due to a lack of significant re-orientational dynamics in the crystal structure resulting from the presence of the bulky -NH3 group in the anion.

First-Principles Calculations on Diffusion and Association Behavior of Fluoride Ions in Ba-Doped LaF3 Solid Electrolyte

Fluoride ion batteries, which generate electrical energy through the fluorination/de-fluorination reaction of electrode active materials, are expected to be the next-generation storage batteries with high energy density. LaF3 with a tysonite-type structure is known as one of the representative solid-state fluoride ion conductors. Substitutional solid solution of divalent cations such as Ba or Sr ions at La sites forms fluoride ion vacancies as charge compensation, resulting in fluoride ion conductivity. The main objective of this study is to analyze the formation behavior of point defects in LaF3 through quantitative evaluation of their formation energies using first-principles calculations, and to elucidate the conduction mechanism of fluoride ions in LaF3.The plane-wave basis PAW method implemented in VASP code was used for the electronic structure calculations. The electron correlation treatment uses the PBEsol-type potential based on the generalized gradient approximation. Calculations for given point defects were performed. The cutoff energy of the plane wave basis sets was set to 420 eV, and the structure optimization calculations were performed until the Hellmann-Feynman force acting on each atom was less than 0.02 eV/Å.There are three fluoride ion sites (12g, 4d, and 2a) in the unit cell of LaF3. Using the supercell model, we calculated the defect formation energies of fluoride ion vacancies at each site. The formation energies at the 12g, 4d, and 2a sites are 0.17 eV, 0.52 eV, and 0.52 eV, respectively. According to the defect formation energies, fluoride ion vacancies are most likely to form at the 12g sites.To elucidate the elementary processes of fluoride ion transfer between 12g sites by the vacancy mechanism, we performed first-principles calculations and transition state search using the Nudged Elastic Band method. From symmetry, four different pathways exist in the lattice of undoped LaF3. The pathway with the highest energy barrier is shown to have very low transfer energies, 0.17 eV, and the energy barriers of the other pathways are less than 0.1 eV. These results suggest that LaF3 has a potential for very fast fluoride ionic conductivity by the vacancy mechanism. In the presentation, the mechanism of fluoride ion conduction in Ba-doped LaF3 will also be reported. This work was supported by the RISING2 (JPNP16001) and the RISING3 (JPNP21006) projects from the New Energy and Industrial Technology Development Organization (NEDO), Japan.

Non-Arrhenius Ionic Conductivity Behaviour in Antiperovskite Solid Electrolytes for Sodium Metal Batteries

Solid-state sodium metal batteries have been proposed as an alternative to lithium-ion batteries (LIBs) for next-generation applications due to the high abundance and wide distribution of sodium resources.1 Sodium antiperovskites (Na3OX, X = Cl, Br, or BH4) have recently attracted great interest as solid electrolyte candidates due to the relatively low processing temperature (<500 oC), reasonable ionic conductivity (up to 4.4 x 10-3 S cm-1 at room temperature), and great chemical stability against sodium metal anodes.2,3 Typical solid-state ionic conductors have temperature-dependent ionic conductivity that follows Arrhenius behaviour over a broad range of temperatures, corresponding to a constant activation energy Ea. However, this is not the case in Na3OBr, and instead a phenomenon resulting in a higher ionic conductivity and lower activation energy is observed to occur at 255 oC. Similar non-Arrhenius ionic conductivity phenomenon has also been reported in the potassium antiperovskite K3OI. It has been proposed that this behaviour originated from anion disordering, but conclusive experimental evidence to support this claim has not been reported.4 An understanding of the origin of this behaviour could enable the synthesis route to be optimised such that higher ionic conductivities could be achieved.In this work, we combined temperature-resolved bulk and local characterisation methods including Pawley and Rietveld refinements of synchrotron x-ray diffraction (XRD), pair distribution function (PDF), solid-state nuclear magnetic resonance (NMR) spectroscopy, and electrochemical impedance spectroscopy (EIS) to gain an insight into the origin of this non-Arrhenius behaviour. We found that this phenomenon does not originate from anion disordering, as previously speculated, because the lattice parameter of Na3OBr changed linearly with temperature and no major intensity changes were observed in the Na-Br and Na-O signals in the PDF patterns. Other supporting findings that lead us to this conclusion will be discussed in the presentation.References Wang, X. et al. Ultra-stable all-solid-state sodium metal batteries enabled by perfluoropolyether-based electrolytes. Nat. Mater. 21, 1057–1066 (2022).Zheng, J., Perry, B. & Wu, Y. Antiperovskite Superionic Conductors: A Critical Review. ACS Mater. Au 1, 92–106 (2021).Sun, Y. et al. Rotational Cluster Anion Enabling Superionic Conductivity in Sodium-Rich Antiperovskite Na3OBH4. J. Am. Chem. Soc. 141, 5640–5644 (2019).Zheng, J. et al. Antiperovskite K3OI for K-Ion Solid State Electrolyte. J. Phys. Chem. Lett. 12, 7120–7126 (2021).

Synthesis and Interface Stabilization of Chalcogenide-Based Solid Electrolytes in Solid-State Sodium Batteries

Rechargeable sodium (Na) batteries that utilizing solid-state ion conductors have attracted intense attentions for large-scale energy storage systems due to the abundant resources of Na compounds and electrochemical voltage (2.70 V vs. 3.05V for Li). So far, the most popular inorganic Na-ion SEs include oxides, halides, and chalcogenides such as Na3PhCh4 (Ph=P, Sb; Ch=S, Se) etc. In specific, Na3SbCh4 (Ch=S, Se) chalcogenide conductors exhibit impressive ionic conductivity at room temperature due to vacancy-assisted three-dimensional (3D) ion transport channels. In this talk, we will introduce our works on the studies on in-situ synthesis of Na chalcogenide solid electrolytes (SEs) and several strategies for interface stabilization of such SEs towards Na anode. The in-situ synthesis studies of Na3SbCh4 (Ch=S, Se) reveal the structural evolutions during the solid-state reaction process.1 Besides, efficient interface stabilization strategies have been demonstrated to enable solid-state Na metal batteries that using Na as the anode, and metal sulfide (TiS2 or FeS2) as the cathode.2, 3 For instance, phase transition interlayer (PEG-PPG-PEG) has been successfully proved to prevent the side reactions between the Na3SbS4 SE and Na metal and contribute to the uniform Na deposition at interface to prevent dendrite formation and growth. The goal of our work is to develop novel chalcogenide Na conductors and promote their applications in solid-state Na batteries. Halacoglu, S.; Chertmanova, S.; Chen, Y.; Li, Y.; Rajapakse, M.; Sumanasekera, G.; Narayanan, B.; Wang, H., Visualization of Solid-State Synthesis for Chalcogenide Na Superionic Conductors by in-situ Neutron Diffraction. ChemSusChem 2021, 14 (23), 5161-5166.Li, Y.; Arnold, W.; Halacoglu, S.; Jasinski, J. B.; Druffel, T.; Wang, H., Phase-Transition Interlayer Enables High-Performance Solid-State Sodium Batteries with Sulfide Solid Electrolyte. Advanced Functional Materials 2021, 31 (28), 2101636.Li, Y.; Halacoglu, S.; Shreyas, V.; Arnold, W.; Guo, X.; Dou, Q.; Jasinski, J. B.; Narayanan, B.; Wang, H., Highly efficient interface stabilization for ambient-temperature quasi-solid-state sodium metal batteries. Chemical Engineering Journal 2022, 434, 134679.

Predicting Ion Diffusion from the Shape of Potential Energy Landscapes.

We present an efficient method to compute diffusion coefficients of multiparticle systems with strong interactions directly from the geometry and topology of the potential energy field of the migrating particles. The approach is tested on Li-ion diffusion in crystalline inorganic solids, predicting Li-ion diffusion coefficients within 1 order of magnitude of molecular dynamics simulations at the same level of theory while being several orders of magnitude faster. The speed and transferability of our workflow make it well-suited for extensive and efficient screening studies of crystalline solid-state ion conductor candidates and promise to serve as a platform for diffusion prediction even up to the density functional level of theory.

Synthesis, Thermodynamic Properties, and Ionic Conductivity of Compounds Based on Bismuth Niobates Doped by Rare-Earth Elements (A Review)

Synthesis methods, thermodynamic and functional properties of compounds based on bismuth niobates doped with rare-earth elements (REEs) are presented. These compounds are promising materials for fuel cells, ceramic oxygen generators, electrocatalysis, etc. As show the data generalized, most compounds have a cubic structure of the δ-form of bismuth oxide, which has the highest ionic conductivity among solid-state ionic conductors. The compounds have high lattice enthalpy and are therefore promising high-energy compounds. The review summarizes studies on the basic thermodynamic characteristics of bismuth niobates doped with rare earth elements. The change in standard enthalpies of formation, lattice enthalpies, and heat capacity when replacing one rare earth element with another is analyzed. It is shown that as the radius of rare earth elements decreases, the standard enthalpies of formation increases and lattice enthalpies increases. The change in ionic conductivity with changes in temperature and rare earth element content has been studied. It has been shown that with increasing temperature and REE content, conductivity increases.