Abstract Solid-state sodium batteries (Na-SSBs) have emerged as promising candidates for next-generation energy storage systems owing to the natural abundance and low cost of sodium, as well as the potential to utilize high-capacity sodium metal anodes. However, the practical implementation of Na metal in combination with inorganic solid electrolytes remains limited by severe interfacial challenges, including chemical and electrochemical instability, as well as poor interfacial contact resulting in void evolution and dendrite growth during cycling. These phenomena lead to increased interfacial resistance, non-uniform sodium deposition, and rapid performance degradation. In this review, we discuss the fundamental interfacial processes occurring between sodium metal and the major classes of inorganic solid electrolytes, including β-alumina solid electrolytes (BASE), NASICON-type oxides, sulfides, complex hydrides, and halide-based electrolytes. Particular emphasis is placed on the origins of interfacial instability, including thermodynamic incompatibility, mixed conducting interphase formation, chemo-mechanical degradation, and wetting limitations. Furthermore, recent interface engineering and surface functionalization strategies are summarized, including metallic and ceramic coatings, artificial interphases, alloy interlayers, carbon-based modifications, polymeric interlayers, and composite sodium anodes. By correlating electrolyte chemistry, interfacial phenomena, and surface engineering strategies, this review provides perspectives for the rational design of stable sodium metal interfaces toward powerful Na-SSBs.
The discovery of novel two-dimensional (2D) carbon allotropes with tailored electronic and mechanical properties remains an important challenge in carbon materials research. Here, we predict a previously unexplored member of the tetra-penta-hexa (TPH) graphene family, termed TPH-M, through particle swarm optimization combined with first-principles calculations. The proposed monolayer is found to be energetically competitive within the family of carbon allotropes and satisfies the criteria for dynamical, mechanical, and thermal stability. $ab~initio$ molecular dynamics simulations further demonstrate that TPH-M retains its structural integrity at elevated temperatures. In contrast to the previously reported semiconducting TPH phases, TPH-M exhibits an intrinsic nonmagnetic metallic electronic structure arising from delocalized C- $p$ states crossing the Fermi level. The metallic state is preserved under moderate mechanical deformation, highlighting the robustness of its electronic properties. Mechanical calculations reveal pronounced elastic anisotropy together with an exceptionally high in-plane Young’s modulus comparable to the reported in-plane stiffness of graphene. Under large tensile strains, TPH-M exhibits distinct strain-dependent responses, including a structural transformation toward a biphenylene-like phase under uniaxial loading and significant modifications of its electronic structure under biaxial strain. The unique combination of intrinsic metallicity, thermal robustness, graphene-like mechanical rigidity, and strain-dependent structural and electronic responses establishes TPH-M as a noteworthy addition to the family of 2D carbon allotropes and provides new insights into the relationship between bonding configuration, mechanical deformation, and electronic properties in low-dimensional carbon systems.
Early ferric hydroxide clusters are widely regarded as key precursors to iron corrosion products, yet the atomistic pathway linking molecular species to crystalline phases remain unclear. In this work, a robust quantum-mechanical structure-screening workflow ( UniGrow ) was developed and employed to identify the global minimum structures of [Fe(OH) _3 ] _n clusters ( n = 1–8) and to investigate their size-dependent structural and electronic evolution during growth. Cluster aggregation drives substantial structural reorganization of the Fe–O framework, leading to increasingly compact three-dimensional motifs with larger cluster sizes. Structural descriptors show progressive convergence towards crystalline Fe(III) phases, with average Fe–O bond lengths increasing from 1.79 to 2.02 Å and Fe coordination numbers rising from 3.0 to 5.5. Energetic stabilization increases rapidly at small sizes and approaches a plateau for n = 6–8, indicating the emergence of locally stable motifs. Electronic analyses reveal convergence of Fe Bader charges, broadening of the density of states from discrete molecular-like features to more continuous band-like distributions, and increasing similarity to crystalline iron oxyhydroxides. Among the reference phases considered, larger clusters exhibit the closest electronic resemblance to α -FeOOH. These results demonstrate that ferric hydroxide clusters progressively acquire crystal-like structural and electronic characteristics during aggregation, providing atomistic insight into the earliest stages of iron corrosion-product formation and identifying plausible precursors to recognizable iron oxyhydroxide motifs.
The ternary III/V semiconductor InGaP is a leading material for the fabrication of red micro-light-emitting diode (LED) structures. Micro-LEDs are promising candidates for next-generation displays, with many advancements over current display technologies, such as high brightness and durability. Etching processes, used to define the mesa structures of the micro-LEDs and the subsequent oxidation of the mesa sidewall, can introduce surface defect states that result in non-radiative recombination on the mesa sidewall. With downward dimensional scaling of micro-LEDs, the properties of the etched mesa sidewall surfaces on the periphery of the devices play an increasingly important role in the optical performance of the structures due to increasing surface area to volume ratio. Direct measurement of the elemental composition and oxidation state of the mesa sidewall surface following etching is an essential step toward maximising the quantum efficiency of the devices. In this study, a novel measurement geometry is employed to isolate and directly characterise the elemental composition and oxidation state of micron-scale LED mesa sidewalls using angle resolved hard x-ray photoelectron spectroscopy. We show that the chemical composition of the etched sidewall is quantifiably different from that of a planar blanket-etched surface of the same material, demonstrating that planar etch studies are not a reliable proxy for sidewall composition, and establishing a measurement capability with which to evaluate future sidewall passivation treatments.
The development of new cathodes is essential for enabling next generation energy storage technologies. Here, we introduce a multi-fidelity workflow that bridges AI-based candidate identification and density functional theory refinement for accelerated discovery of cathode materials. Starting from the Energy-graph networks for materials exploration (GNoME) database, we use foundation machine-learning force fields (MLFFs) as an intermediate-fidelity layer to screen Li-, Na-, K-, Mg-, and Ca-ion intercalation cathodes. We assess dynamical stability and simulate intercalation voltage profiles to determine the average operating voltage and specific energy. The surviving candidates are further prioritized using experimentally motivated filters based on space-group prevalence, elemental availability, and cost, followed by DFT+U refinement of the most promising structures. Finally, combined MLFF and DFT nudged elastic band calculations are used to assess ion-migration kinetics and identify candidates with the potential for good rate capability. The workflow reduces 615 high-confidence Energy-GNoME cathodes to 10 prioritized candidates with favorable electrochemical properties and manageable volume changes. In addition to delivering a shortlist of promising candidates, this work benchmarks the consistency of Energy-GNoME, ML interatomic potential, and DFT predictions and demonstrates how MLFFs can transform AI-prioritized materials databases into physics-grounded discovery pipelines.
