Enhancing P2/O3 Biphasic Cathode Performance for Sodium-Ion Batteries: A Metaheuristic Approach to Multi-Element Doping Design.

Sodium-ion batteries (SIBs) have emerged as a compelling alternative to lithium-ion batteries (LIBs), exhibiting comparable electrochemical performance while capitalizing on the abundant availability of sodium resources. In SIBs, P2/O3 biphasic cathodes, despite their high energy, require furthur improvements in stability to meet current energy demands. This study introduces a systematic methodology that leverages the meta-heuristically assisted NSGA-II algorithm to optimize multi-element doping in electrode materials, aiming to transcend conventional trial-and-error methods and enhance cathode capacity by the synergistic integration of P2 and O3 phases. A comprehensive phase analysis of the meta-heuristically designed cathode material Na0.76Ni0.20Mn0.42Fe0.30Mg0.04Ti0.015Zr0.025O2 (D-NFMO) is presented, showcasing its remarkable initial reversible capacity of 175.5 mAh g-1 and exceptional long-term cyclic stability in sodium cells. The investigation of structural composition and the stabilizing mechanisms is performed through the integration of multiple characterization techniques. Remarkably, the irreversible phase transition of P2→OP4 in D-NFMO is observed to be dramatically suppressed, leading to a substantial enhancement in cycling stability. The comparison with the pristine cathode (P-NFMO) offers profound insights into the long-term electrochemical stability of D-NFMO, highlighting its potential as a high-voltage cathode material utilizing abundant earth elements in SIBs. This study opens up new possibilities for future advancements in sodium-ion battery technology.

Exploiting High-Voltage Stability of Dual-Ion Aqueous Electrolyte Reinforced by Incorporation of Fiberglass into Zwitterionic Hydrogel Electrolyte.

Rechargeable zinc aqueous batteries are key alternatives for replacing toxic, flammable, and expensive lithium-ion batteries in grid energy storage systems. However, these systems possess critical weaknesses, including the short electrochemical stability window of water and intrinsic fast zinc dendrite growth. Hydrogel electrolytes provide a possible solution, especially cross-linked zwitterionic polymers that possess strong water retention ability and high ionic conductivity. Herein, an in situ prepared fiberglass-incorporated dual-ion zwitterionic hydrogel electrolyte with an ionic conductivity of 24.32 mS cm-1 , electrochemical stability window up to 2.56 V, and high thermal stability is presented. By incorporating this hydrogel electrolyte of zinc and lithium triflate salts, a zinc//LiMn0.6 Fe0.4 PO4 pouch cell delivers a reversible capacity of 130 mAh g-1 in the range of 1.0-2.2 V at 0.1C, and the test at 2C provides an initial capacity of 82.4 mAh g-1 with 71.8% capacity retention after 1000 cycles with a coulombic efficiency of 97%. Additionally, the pouch cell is fire resistant and remains safe after cutting and piercing.

Zinc Anodes Modified by One-Molecular-Thick Self-Assembled Monolayers for Simultaneous Suppression of Side-Reactions and Dendrite-Formation in Aqueous Zinc-Ion Batteries.

Repeated charge/discharge in aqueous zinc-ion batteries (ZIBs) commonly results in surface corrosion/passivation and dendrite formation on zinc anodes, which is a major challenge for the commercialization of zinc-based batteries. In this work, metallic Zn modified by self-assembled monolayers is described as a viable anode for ZIBs. ω-mercaptoundecanoic acid that is spontaneously adsorbed on Zn (MUDA/Zn) contributes to the simultaneous suppression of side reactions and dendrite formation in ZIBs. Though one-molecular-thick, densely packed alkyl chains prohibit H2 O and H+ from making direct contact with the underlying Zn, and surface carboxylate moieties (-COO- ) effectively repel anionic species (OH- ) in a solution, which renders a Zn anode inert against zincate formation within a wide range of pH. In contrast, the electrostatic attraction between surface-carboxylates and cations increases the concentration of Zn2+ on the surface of MUDA/Zn to facilitate Zn plating/stripping with less overpotentials. The high concentration of Zn2+ also results in an increased number of nucleation sites, which enhances the lateral growth of Zn with no formation of dendrites. As a result, MUDA/Zn shows excellent stability during prolonged Zn plating/stripping within a wide range of pH. The advantageous properties of MUDA/Zn are also retained in full-cells coupled with δ-MnO2 cathodes.

Cyan-Light-Emitting Chalcogenometallate Phosphor, KGaS2:Eu2+, for Phosphor-Converted White Light-Emitting Diodes.

A novel KGaS2 phosphor host that emits a cyan light was discovered to fill the cyan gap in the visible spectrum of phosphor-converted white light-emitting diodes (pc-wLEDs). KGaS2, belonging to the chalcogenometallates of the type ABQ2, was synthesized via a solid-state route with compositions optimized to achieve a phosphor host that would achieve the best photoluminescence (PL) properties. The activation with Eu2+ gave rise to PL in the cyan region of the spectrum with a PL maximum at ∼498 nm, as measured under the near-UV (420 nm) and blue (450 nm) excitations. The PL properties at the near-UV excitation are found to be much better, as compared to those obtained at the blue excitation. The Rietveld analysis, using high resolution synchrotron X-ray diffraction calibrated at a wavelength of 1.522 Å and selected area electron diffraction (SAED) pattern analysis of the composition optimized with the highest PL intensity, revealed a centrosymmetric monoclinic structure in the C2/c space group. The stoichiometry of the optimized composition, as estimated using Rietveld refinement, was revealed as KGa0.921S1.882:Eu2+. The decay curve measurement, using time-resolved spectroscopy, yielded a 10% decay time of 0.41 µs, which is much smaller compared with the decay time of the commercially available ß-SIALON phosphor that has a 10% decay time of 1.71 µs. The white pc-LED, fabricated with a cyan phosphor, had a higher value on the color rendering index and a lower value for color correlated temperatures, as compared with the version fabricated without a cyan phosphor, which makes this novel phosphor suitable for applications as a pc-wLED.

KCrS2 Cathode with Considerable Cyclability and High Rate Performance: The First K+ Stoichiometric Layered Compound for Potassium-Ion Batteries.

KCrS2 is presented as a stable and high-rate layered material that can be used as a cathode in potassium-ion batteries. As far as it is known, KCrS2 is the only layered material with stoichiometric amounts of K+ , which enables coupling with a graphite anode for full-cell construction. Cr(III)/Cr(IV) redox in KCrS2 is also unique, because LiCrS2 and NaCrS2 are known to experience S2- /S2 2- redox. O3-KCrS2 is first charged to P3-K0.39 CrS2 and subsequently discharged to O'3-K0.8 CrS2 , delivering an initial discharge capacity of 71 mAh g-1 . The following charge/discharge (C/D) shows excellent reversibility between O'3-K0.8 CrS2 and P3-K0.39 CrS2 , retaining ≈90% of the initial capacity during 1000 continuous cycles. The rate performance is also noteworthy. A C/D rate increase of 100-fold (0.05 to 5 C) reduces the reversible capacity only by 39% (71 to 43 mAh g-1 ). The excellent cyclic stability and high rate performance are ascribed to the soft sulfide framework, which can effectively buffer the stress caused by K+ deinsertion/insertion. During the transformation between P3-K0.39 CrS2 and O'3-K0.8 CrS2 , the material resides mostly in the P3 phase, which minimizes the abrupt dimension change and allows facile K+ diffusion through spacious prismatic sites. Structural analysis and density functional theory calculations firmly support this reasoning.

Determination of possible configurations for Li0.5CoO2 delithiated Li-ion battery cathodes via DFT calculations coupled with a multi-objective non-dominated sorting genetic algorithm (NSGA-III).

Here, we propose a new and logical approach to systematically treat the configurational diversity in density functional theory (DFT) calculations. To tackle this issue, we select Li0.5CoO2 as a representative example because it is one of the most extensively studied cathodes in Li-ion batteries (LIBs), and it has a huge number of disordered configurations. To delineate the configurations that will match well with the experimentally measured macro-functions of redox potential, band gap energy, and magnetic moment, we adopt a multi-objective, non-dominated sorting, genetic algorithm (NSGA-III) that enables the simultaneous optimization of these three objective functions. The decision variables include configuration of the Li/vacancy, initial input for the magnetic moment distribution reflecting Co3+/Co4+ distribution, and initial input for the lattice parameter and Hubbard U. We use NSGA-III to separate the configurations that exhibit awkward objective function values, which allows us to pinpoint a set of plausible configurations that match the experimentally estimated values of the objective functions. The results reveal a plausible configuration that is a mixture of various ordered/disordered configurations rather than a simple ordered structure.

Metaheuristics-Assisted Combinatorial Screening of Eu2+-Doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N Compositional Space in Search of a Narrow-Band Green Emitting Phosphor and Density Functional Theory Calculations.

A metaheuristics-based design would be of great help in relieving the enormous experimental burdens faced during the combinatorial screening of a huge, multidimensional search space, while providing the same effect as total enumeration. In order to tackle the high-throughput powder processing complications and to secure practical phosphors, metaheuristics, an elitism-reinforced nondominated sorting genetic algorithm (NSGA-II), was employed in this study. The NSGA-II iteration targeted two objective functions. The first was to search for a higher emission efficacy. The second was to search for narrow-band green color emissions. The NSGA-II iteration finally converged on BaLi2Al2Si2N6:Eu2+ phosphors in the Eu2+-doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N compositional search space. The BaLi2Al2Si2N6:Eu2+ phosphor, which was synthesized with no human intervention via the assistance of NSGA-II, was a clear single phase and gave an acceptable luminescence. The BaLi2Al2Si2N6:Eu2+ phosphor as well as all other phosphors that appeared during the NSGA-II iterations were examined in detail by employing powder X-ray diffraction-based Rietveld refinement, X-ray absorption near edge structure, density functional theory calculation, and time-resolved photoluminescence. The thermodynamic stability and the band structure plausibility were confirmed, and more importantly a novel approach to the energy transfer analysis was also introduced for BaLi2Al2Si2N6:Eu2+ phosphors.

Density functional theory calculations for the band gap and formation energy of Pr4-xCaxSi12O3+xN18-x; a highly disordered compound with low symmetry and a large cell size.

A novel oxynitride compound, Pr4-xCaxSi12O3+xN18-x, synthesized using a solid-state route has been characterized as a monoclinic structure in the C2 space group using Rietveld refinement on synchrotron powder X-ray diffraction data. The crystal structure of this compound was disordered due to the random distribution of Ca/Pr and N/O ions at various Wyckoff sites. A pragmatic approach for an ab initio calculation based on density function theory (DFT) for this disordered compound has been implemented to calculate an acceptable value of the band gap and formation energy. In general, for the DFT calculation of a disordered compound, a sufficiently large super cell and infinite variety of ensemble configurations is adopted to simulate the random distribution of ions; however, such an approach is time consuming and cost ineffective. Even a single unit cell model gave rise to 43 008 independent configurations as an input model for the DFT calculations. Since it was nearly impossible to calculate the formation energy and the band gap energy for all 43 008 configurations, an elitist non-dominated sorting genetic algorithm (NSGA-II) was employed to find the plausible configurations. In the NSGA-II, all 43 008 configurations were mathematically treated as genomes and the calculated band gap and the formation energy as the objective (fitness) function. Generalized gradient approximation (GGA) was first employed in the preliminary screening using NSGA-II, and thereafter a hybrid functional calculation (HSE06) was executed only for the most plausible GGA-relaxed configurations with lower formation and higher band gap energies. The final band gap energy (3.62 eV) obtained after averaging over the selected configurations, resembles closely the experimental band gap value (4.11 eV).

The Composite Structure and Two-Peak Emission Behavior of a Ca1.5Ba0.5Si5O3N6:Eu(2+) Phosphor.

A Ca1.5Ba0.5Si5O3N6:Eu(2+) phosphor with a monoclinic lattice in the Cm space group exhibiting a composite structure consisting of CaSi2O2N2-like and BaSi6N8O-like structures was examined in terms of structure and luminescence. The luminescent properties of the Ca1.5Ba0.5Si5O3N6:Eu(2+) phosphor could be suitable for light-emitting diode applications since it exhibited a promising yellow (or amber) emission peaking at ∼ 570-590 nm at excitations of 450-460 nm. The present investigation was focused on verifying the composite structure by employing quantum mechanical calculations such as the Hartree-Fock ab initio calculation and a density functional theory calculation along with precise structural and compositional analyses. The two-peak emission behavior ascribed to the composite structure was also examined in terms of continuous wave and time-resolved photoluminescence. In addition, the energy transfer between two activator sites ascribed to the composite structure was examined in detail.

Discovery of a Red-Emitting Li3RbGe8O18:Mn4+ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations.

A solid-state combinatorial chemistry approach, which used the A-Ge-O (A = Li, K, Rb) system doped with a small amount of Mn4+ as an activator, was adopted in a search for novel red-emitting phosphors. The A site may have been composed of either a single alkali metal ion or of a combination of them. This approach led to the discovery of a novel phosphor in the above system with the chemical formula Li3RbGe8O18:Mn4+. The crystal structure of this novel phosphor was solved via direct methods, and subsequent Rietveld refinement revealed a trigonal structure in the P3̅1m space group. The discovered phosphor is believed to be novel in the sense that neither the crystal structure nor the chemical formula matches any of the prototype structures available in the crystallographic information database (ICDD or ICSD). The measured photoluminescence intensity that peaked at a wavelength of 667 nm was found to be much higher than the best intensity obtained among all the existing A2Ge4O9 (A = Li, K, Rb) compounds in the alkali-germanate system. An ab initio calculation based on density function theory (DFT) was conducted to verify the crystal structure model and compare the calculated value of the optical band gap with the experimental results. The optical band gap obtained from diffuse reflectance measurement (5.26 eV) and DFT calculation (4.64 eV) results were in very good agreement. The emission wavelength of this phosphor that exists in the deep red region of the electromagnetic spectrum may be very useful for increasing the color gamut of LED-based display devices such as ultrahigh-definition television (UHDTV) as per the ITU-R BT.2020-2 recommendations and also for down-converter phosphors that are used in solar-cell applications.

A smart load-sensing system using standardized mechano-luminescence measurement.

The mechano-luminescence (ML) of phosphors has stirred a great deal of interest for its potential application in inexpensive, non-destructive load sensors. However, the most serious drawback of ML phosphors has been responses that differ according to the loading conditions. This has led to a lack of standardization in realizing smart ML sensor applications. We improved the applicability of ML phosphors to that of a smart, standardized load sensor by detecting ML based on the UV excitation above the threshold power density during the entire loading process. The ML behavior under these conditions was completely different from that of conventional ML behavior with UV excitation turned off. The ML output was clearly represented as a simple linear function of the applied load under conditions that could be either static or dynamic. In addition, neither a ML loss angle nor hysteresis behavior was observed under these ML measurement conditions.

Combinatorial screening of luminescent and structural properties in a Ce(3+)-doped Ln-Al-Si-O-N (Ln = Y, La, Gd, Lu) system: the discovery of a novel Gd3Al(3+x)Si(3-x)O(12+x)N(2-x):Ce(3+) phosphor.

The discovery of novel phosphors for use in light emitting diodes (LED) has gained in significance because LED-based solid-state lighting applications now attract a great deal of attention for energy savings and environmental concerns. Recent research trends have centered on the discovery of novel phosphors, not on slight variations of well-known phosphors. In a real sense, novelty goes beyond simple variations or improvements in existing phosphors. A brilliant strategy for the discovery of novel phosphors is to introduce an appropriate activator to existing inorganic compounds. These compounds have structures that are well-defined in crystallographic structure databases, but they have never been considered as a phosphor host. Another strategy is to discover new host compounds with structures that cannot be found in existing databases. We have simultaneously pursued both strategies by employing metaheuristics-assisted combinatorial material search techniques. In the present investigation, we screened a search space consisting of Ln-Al-Si-O-N (Ln = Y, La, Gd, Lu), and thereby we discovered a blue-light-emitting novel phosphor, Gd3Al(3+x)Si(3-x)O(12+x)N(2-x):Ce(3+), with a monoclinic system in the C2 space group--a potential candidate for UV-LED applications.

Discovery of a phosphor for light emitting diode applications and its structural determination, Ba(Si,Al)5(O,N)8:Eu2+.

Most of the novel phosphors that appear in the literature are either a variant of well-known materials or a hybrid material consisting of well-known materials. This situation has actually led to intellectual property (IP) complications in industry and several lawsuits have been the result. Therefore, the definition of a novel phosphor for use in light-emitting diodes should be clarified. A recent trend in phosphor-related IP applications has been to focus on the novel crystallographic structure, so that a slight composition variance and/or the hybrid of a well-known material would not qualify from either a scientific or an industrial point of view. In our previous studies, we employed a systematic materials discovery strategy combining heuristics optimization and a high-throughput process to secure the discovery of genuinely novel and brilliant phosphors that would be immediately ready for use in light emitting diodes. Despite such an achievement, this strategy requires further refinement to prove its versatility under any circumstance. To accomplish such demands, we improved our discovery strategy by incorporating an elitism-involved nondominated sorting genetic algorithm (NSGA-II) that would guarantee the discovery of truly novel phosphors in the present investigation. Using the improved discovery strategy, we discovered an Eu(2+)-doped AB5X8 (A = Sr or Ba, B = Si and Al, X = O and N) phosphor in an orthorhombic structure (A21am) with lattice parameters a = 9.48461(3) Å, b = 13.47194(6) Å, c = 5.77323(2) Å, α = ß = γ = 90°, which cannot be found in any of the existing inorganic compound databases.

Mechanoluminescence of SrAl2O4:Eu(+), Dy(3+) under cyclic loading.

The mechanoluminescence (ML) of SrAl2O4:Eu(+), Dy(3+) (SAO) has been of particular interest based on the possibility that these materials could be used as nondestructive, reproducible stress (or load) sensors. However, there has been no in-depth study of ML under a cyclic load. It was found that a cyclic load generated harmonics in the ML response. The second harmonic term exhibiting a doubled frequency was significant, but the others could be ignored. In addition, hysteresis behavior was observed in the ML and was examined by comparison with the hysteresis that is typical in piezoelectricity.

Nonradiative energy transfer between two different activator sites in La(4-x)Ca(x)Si12O(3+x)N(18-x):Eu2+.

Energy transfer, which affects the entire performance of luminescent material, has been generally treated as an averaged parameter by assuming the host material to be a homogeneous continuum. However, energy transfer should be investigated in association with the crystallographic local structure around an activator site. To accomplish this, we established an analytical model and derived comprehensive rate equations, elucidating the relationship between the local structure and energy transfer behavior of La(4-x)Ca(x)Si12O(3+x)N(18-x):Eu2+, which is a recently discovered luminescent material for use in light-emitting diodes. Using the rate-equation model with the assistance of particle swarm optimization, the full-scale decay curves of donors and acceptors located at different crystallographic sites was computed.

Solid-state combinatorial chemistry of Eu(2+)-doped Sr-Al-Si-O-N phosphors.

Sr-Al-Si-O-N composition space was screened by a solid state combinatorial chemistry. For this sake, powder mixtures of Sr3N2, alpha-Si3N4, AIN and Eu3N2 was fired at 1500 degrees C-1900 degrees C for 2 h under 1.0 Mpa N2 using a gas pressurized sintering (GPS) furnace. The resultant phosphors were phase-identified, and the photo luminescence was examined. The Sr-Al-Si-O-N phosphors are blue-Green and orange in color and emit in the region of 520-630 nm depending on synthesized temperature. Considering an intense excitation band in blue LED and emission band, these materials can be used as novel conversion phosphor for White-LEDs, if the luminance was improved.

Heuristics-assisted combinatorial screening of oxynitride phosphors.

Nitride or oxynitride phosphors have been recently acting as key phosphors in the light emitting diode (LED) application. In particular, their superiority to the conventional oxide-based phosphors in terms of efficacy, thermal stability, color rendering, and etc. made it possible to achieve rapid commercialization of several nitride or oxynitride phosphors such as CaAISiN3, alpha- and beta-Sialons, Sr2Si5N8, and etc. However, it is still necessary to discover more nitride or oxynitride phosphors, which meet specific requirements for LED applications. In this regard, heuristics-based combinatorial material search (HCMS) strategies have been applied to multi-compositional inorganic systems to search for new phosphors and to optimize the properties of phosphors in the six dimensional SrCO3-BaCO3-CaCO3-SiO2-Si3N4-Eu2O3 search space. The heuristics strategies include non-dominated sorting genetic algorithm (NSGA) and particle swarm optimization (PSO).

Unprecedented Cyclability and Moisture Durability of NaCrO2 Sodium-Ion Battery Cathode via Simultaneous Al Doping and Cr2O3 Coating.

Although there are many cathode candidates for sodium-ion batteries (NIBs), NaCrO2 remains one of the most attractive materials due to its reasonable level of capacity, nearly flat reversible voltages, and high thermal stability. However, the cyclic stability of NaCrO2 needs to be further improved in order to compete with other state-of-the-art NIB cathodes. In this study, we show that Cr2O3-coated and Al-doped NaCrO2, which is synthesized through a simple one-pot synthesis, can achieve unprecedented cyclic stability. We confirm the preferential formation of a Cr2O3 shell and a Na(Cr1-2xAl2x)O2 core, rather than xAl2O3/NaCrO2 or Na1/1+2x(Cr1/1+2xAl2x/1+2x)O2, through spectroscopic and microscopic methods. The core/shell compounds exhibit superior electrochemical properties compared to either Cr2O3-coated NaCrO2 without Al dopants or Al-doped NaCrO2 without shells because of their synergistic contributions. As a result, Na(Cr0.98Al0.02)O2 with a thin Cr2O3 layer (5 nm) shows no capacity fading during 1000 charge/discharge cycles while maintaining the rate capability of pristine NaCrO2. In addition, the compound is inert against humid air and water. We also discuss the reasons for the excellent performance of Cr2O3-coated Na(Cr1-2xAl2x)O2.

In situ health monitoring of multiscale structures and its instantaneous verification using mechanoluminescence and dual machine learning.

Extensive changes in the legal, commercial and technical requirements in engineering fields have necessitated automated real-time structural health monitoring (SHM) and instantaneous verification. An integrated system with mechanoluminescence (ML) and dual artificial intelligence (AI) modules with subsidiary finite element method (FEM) simulation is designed for in situ SHM and instantaneous verification. The ML module detects the exact position of a crack tip and evaluates the significance of existing cracks with a plastic stress-intensity factor (PSIF; K P ). ML fields and their corresponding K p M L values are referenced and verified using the FEM simulation and bidirectional generative adversarial network (GAN). Well-trained forward and backward GANs create fake FEM and ML images that appear authentic to observers; a convolutional neural network is used to postulate precise PSIFs from fake images. Finally, the reliability of the proposed system to satisfy existing commercial requirements is validated in terms of tension, compact tension, AI, and instrumentation.

Digital Image Correlation Compatible Mechanoluminescent Skin for Structural Health Monitoring.

Monitoring structural health using mechanoluminescent (ML) effects is widely considered as a potential full-field and direct visualizing optical method with high spatial and temporal resolution and simple setup in a noncontact manner. The challenges and uncertainties in the mapping of ML field to effective strain field, however, tend to limit significant commercial ML applications for structural health monitoring systems. Here, however, quantification problems are resolved using the digital image correlation (DIC) method. Specifically, an image containing mechanically induced photon information is processed using a DIC algorithm to measure the strain field components, which enables the establishment of a calibration curve when the ML field is mapped onto the effective strain field using pixel level information. The results show a linear relationship between effective strain and ML intensity despite the plastic flow in ML skin. Furthermore, the calibration curve allows for easy conversion of ML field to effective-strain field at the crack-tip plastic zone of the alloy structure, retaining its spatial resolution. The compatibility of ML skin with the DIC algorithm not only enables the quantification of the ML effects of several organic/inorganic ML materials, but may also be useful in elucidating the fundamentals of the trap-controlled mechanism.