Nonionic Research Articles

A novel composite solid electrolyte with ultrahigh ion transference number and stability for solid-state sodium metal batteries

The combination of a Na-ion conducting filler and polymer matrix in composite solid electrolyte (CSE) presents a promising and attractive strategy for improving the energy density and safety of the sodium-metal batteries. The agglomeration and precipitation of inorganic ceramic fillers in the polymer matrix present a major challenge leading to the decreased Na ion conductivity property and transference number, increased interfacial resistance, and worsened mechanical properties of CSEs. Herein, we introduce a novel composite solid electrolyte (denoted as 3D-15PNZSPP), comprising a three-dimensional interconnected porous Na3Zr2Si2PO12 framework integrated with an asymmetric polymer electrolyte layer, which not only offers continuous conductive pathways and high mechanical strength for Na ions transfer, but also enhances the interfacial compatibility and expands the electrochemical stability window. The 3D-15PNZSPP CSE shows a high Na+ conductivity of 7.6 × 10−4 S cm−1 and an outstanding transference number of 0.82 at temperature of 30 °C. These characteristics enable the Na/3D-15PNZSPP/Na symmetric cell to cycle for over 700 h with a small overpotential. More importantly, the assembled all solid-state Na0.67Li0.24Mn0.76O2/3D-15PNZSPP/Na batteries demonstrate remarkable cycling stability and high rate capability, indicating a promising and facile strategy for designing ultra-safe and high-performance solid-state sodium metal batteries.

Enhanced stability of sodium anodes by amino-functioned macroporous two-dimensional nanodiamond coated polypropylene separators

The abundance and cost-effectiveness of sodium metal present a promising foundation for the widespread adoption of sodium-metal batteries (SMBs). However, the dendrite formation during the repeated Na deposition/stripping process impedes the long-term stable operation of the batteries. To tackle these concerns, a separator structure is designed by coating commercial polypropylene (PP) with amino (NH2) functionalized two-dimensional diamonds (diamane) with macroporous structure. As a result, the Na symmetric cell incorporating the PP/NH2-diamane separator exhibits sustained stability for 3200 h at 5 mA cm−2 with 1 mAh cm−2, and 1800 h at a high current density of 20 mA cm−2 with 1 mAh cm−2. The excellent electrochemical performance of the cell with the PP/NH2-diamane separator can be attributed not only to the sodiophilic NH2 functional groups facilitating the uniform deposition of Na ion, but also to the homogeneously macroporous channels formed on the PP separators, enabling uniform and rapid transportation of sodium ions through the separator. Moreover, the PP/NH2-diamane separator also enhances the rate capability and long-cycle stability of Na metal batteries. This cost-effective strategy offers a promising avenue for engineering stable SMBs through simply separator modifications.

Employing Graph Neural Networks for Predicting Electrode Average Voltages and Screening High-Voltage Sodium Cathode Materials.

For many years, humans have been relentlessly focused on enhancing battery longevity and boosting energy storage capacities. The performance and durability of a battery depend significantly on the material used for its electrodes. In this context, merging machine learning with density functional theory (DFT) calculations has emerged as a pivotal approach to advancing the exploration of battery crystal structures. We present a new method that combines a graph convolutional neural network (GNN) with a Transformer convolutional layer, which we call Transformer-GNN. To underscore its efficacy, we benchmarked Transformer-GNN against three established statistical machine learning models: Support Vector Machine, Random Forest, and XGBoost. We also developed a standard GNN, which we refer to as Basic-GNN. Additionally, we compared Basic-GNN with Transformer-GNN to highlight the improvements brought about by incorporating the Transformer convolutional layer. The Transformer-GNN model outperforms the other models, achieving the highest R2 value of 0.82 and the lowest mean squared error of 0.3161. Our findings demonstrate that the Transformer-GNN can profoundly understand battery crystal structures, thus forging the path toward more sophisticated and durable battery systems. Leveraging the GNN model's voltage predictions in tandem with the capacity data sourced from the database, we screened and pinpointed Na(NiO2)2 as a high-voltage (higher than 5 V), high-capacity sodium cathode material. We conducted DFT calculations on Na(NiO2)2 and revealed the migration mechanism of the Na ions.

Characterizations and solubility profile of novel senary SiO2–CaO–Na2O–P2O5–CaF2–SrO glass structure modified with Nb2O5

The solubility/degradability of bioactive glasses play crucial role in bone tissue engineering applications owing to the release of ions from their structure, which exert therapeutic effects on tissues. The present study evaluates the findings of a detailed investigation on the main features and solubility behaviors of newly formulated Nb incorporated glasses (Nb-BGs). New glass formulation in SiO2–CaO–Na2O–P2O5–CaF2–SrO–xNb2O5 (x: 0.0, 0.5, 1.0, and 1.5 mol. %) system was successfully synthesized by melt-quenching technique. Glass composition was verified with Energy Dispersive X-ray Fluorescence spectrometer analysis and its amorphous nature, functional groups of the matrix and morphological features were identified via X-Ray diffraction analyses, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscope analysis, respectively. Network connectivity (NC) of the Nb-BGs was assessed with respect to the role of Nb2O5 in the glass matrix as network former, modifier, or both. In order to evaluate the in vitro solubility of Nb-BGs, released concentrations of particular ions from the glass compositions were determined at certain time points and comprehensively discussed with several mathematical models such as zero-order, first-order, second-order, Higuchi, and Korsmeyer-Peppas for the first time. Results showed that the incorporation of Nb2O5 (up to 1.5 mol. %) increased the density, oxygen density as well as NC values of newly formulated glasses. Si, Na and Ca ions which play a main role in well-defined Hench's mechanism followed mostly second-order release kinetics for all glasses in the mathematical models studied. When the Nb content increase (to 1.5 mol. %) in glass composition, the release mechanism of Si ion according to Korsmeyer-Peppas model shifts from the diffusion mechanism to an erosion-dominant release mechanism.

Doping effects of conductivity improvement in anti-perovskite Na3OBr solid electrolytes

Improving the ionic conductivity of solid-state sodium (Na) ion electrolytes is an urgent issue, given their widespread application in all solid-state commercial batteries, and the problems facing this industry, including source shortage, high cost, and safety issues. Substituting halogen and oxygen ions (O2−) with larger atoms is expected to enlarge this bottleneck, as the introduction of distortions in the material can result in an improvement in its ionic conductivity. In this paper, two approaches to introduce distortions into Na3OBr solid electrolytes are provided. Adding either I− or S2− to replace the smaller ions, Br− or O2−, can achieve this result. The lattice distortion increases with increasing concentration of I− or S2− in Na3OBr electrolytes, improving their ionic conductivity. We also discuss the crystallinity of electrolytes, which is an important factor for the diffusion of mobile ions.

Two‐dimensional sp2‐carbon‐linked covalent organic framework for large‐capacity and long‐life Na metal batteries

AbstractNa metal batteries are regarded as an encouraging route for energy‐dense and low‐cost battery systems. However, the unstable and irreversible Na plating/stripping, caused by the uncontrolled dendritic Na growth, prevents their practical applications. Herein, a two‐dimensional sp2‐carbon‐linked covalent organic framework (cyano‐sp2c‐COF) is adopted as seeding/hosting coating layer for a highly stable interface with long cycling life, large capacity, and high Na utilization. Benefit from the features of a fully π‐conjugated structure and well‐defined cyano groups, cyano‐sp2c‐COF with superior sodiophilicity and small interface resistance can reduce the nucleation barrier, enable Na ion flux uniformity, and enhance interface stability. Ultimately, the system achieves a low nucleation overpotential of only 10 mV, a remarkable average Coulombic efficiency of 99.7% maintained over 500 cycles in half cells, and exceptional interfacial durability of 8500 h with a high accumulated capacity of 8.5 Ah cm−2 in symmetric cells. Furthermore, the symmetric cells also present a steady cycling, even increasing the depth of discharge up to 90%. As proof, full cells demonstrate a long lifespan enduring 2700 cycles with tiny capacity decay, providing valuable insights into the long‐life Na batteries.

Control of Biological Surface States on Chlorine-Doped Amorphous Silica Particles and Their Effective Absorptive Ability for Antibody Protein.

Amorphous silica particles (ASPs) have low biotoxicity and are used in foodstuffs; however, the adsorption states of proteins on their surfaces have not yet been clarified. If the adsorption states can be clarified and controlled, then a wide range of biological and medical applications can be expected. The conventional amorphous silica particles have the problem of protein adsorption due to the strong interaction with their dense silanol groups and denaturation. In this study, the surfaces of amorphous silica particles with a lower silanol group density were modified with a small amount of chlorine during the synthesis process to form a specific surface layer by adsorbing water molecules and ions in the biological fluid, thereby controlling the protein adsorption state. Specifically, the hydration state on the surface of the amorphous silica particles containing trace amounts of chlorine was evaluated, and the surface layer (especially the hydration state) for the adsorption of antibody proteins while maintaining their steric structures was evaluated and discussed. The results showed that the inclusion of trace amounts of chlorine increased the silanol groups and Si-Cl bonds in the topmost surface layer of the particles, thereby inducing the adsorption of ions and water molecules in the biological fluid. Then, it was found that a novel surface layer was formed by the effective adsorption of Na and phosphate ions, which would change the proportion of the components in the hydration layer. In particular, the proportion of the free water component increased by 21% with the doping of chlorine. Antibody proteins were effectively adsorbed on the particles doped with trace amounts of chlorine, and their steric adsorption states were evaluated. It was found that the proteins were clearly adsorbed and maintained the steric state of their secondary structure. In the immunoreactivity tests using streptavidin and biotin, biotin bound to the chlorine-doped particles showed efficient reactivity. In conclusion, this study is the first to discover the surface layer of the amorphous silica particles to maintain the steric structures of adsorbed proteins, which is expected to be used as a carrier particle for antibody test kits and immunochromatography.

Investigation of hexagonal boron nitride monolayer with pores as an anode material for sodium-ion batteries

The hexagonal boron nitride monolayer (h-BNML) used as an anode material for metal-ion batteries was assumed pristine form. However, inspired by the imperfections in natural materials, this study investigates the effect of defects on the electrochemical properties of h-BNML. Within the current piece of research, h-BNML with pores is introduced to develop an anode material for sodium ion battery (SIBs) by undertaking density-functional theory (DFT) computations. During the diffusion and storage process of Na ions, the pores effect was thoroughly investigated. The boron atoms were removed from the structure of the pure h-BNML in order to form the h-BNML with pores, which mimicked the pore formation. Based on the DFT results, after the pore formation, the h-BNML retained its planarity. Following the introduction of vacancies, significant alterations occurred in the electronic structure characteristics of h-BNML within the pores, facilitating the effective adsorption of Na ions within the pore. The results of quantum theory of atoms in molecules indicated that there were interactions between the pores and Na ions through an electrostatic-type attraction. The h-BNML with pores was capable of retaining a large number of Na ions at its surface without any change in its planar structure. This led to an increase in its theoretical specific capacity, which increased with porosity. Hence, unlike the pure h-BNML, the pore formation improved the diffusion of Na ions. This can be promising to designing highly efficient anodes for SIBs. The methodological approach in this study can be used for tailoring porous BN materials for SIBs.

Preparation of nanodiamonds modified hard carbon with uniform spherical feature for improving sodium-ion storage performances

Sodium-ion batteries (SIBs) have received remarkable attention due to their abundant sodium (Na) content and low resources cost. However, the absence of high-performance anode materials make carbon-based SIBs still a challenge. Herein, nano-diamonds (NDs) modified gleditsia japonica shell carbon to form a uniform carbon microsphere, which improves the graphitization degree and Na ion adsorption, NDs also act as a strong scaffold to maintain its stability. This spherical carbon-based material exhibits superior performances including the enhanced capacity (270 mA h g−1 at 0.2C after 100 cycles) and long-cycle stability (155 mA h g−1 at 2C after 1000 cycles) when incorporated into SIBs. This work provides a green and simple synthesis strategy for fabricating high performance porous spherical carbon used for SIBs anode.

Metallic Be[formula omitted]M (M = Al, Ga) monolayers as potential universal anodes for Li and post-Li ion batteries

Developing excellent comprehensive performance anode materials is of vital importance for rechargeable metal ion batteries in the domain of energy conversion and storage. By first-principles calculations, we have appreciated that the highly conductive planar hexacoordinate Be2Al and Be2Ga monolayers can be served as universal anodes for alkali/alkaline metal ion batteries. Due to favorable adsorption energy landscape, the diffusion barriers of Li, Na, K, and Ca atoms on the Be2Al and Be2Ga surfaces are as low as 0.116, 0.075, 0.046, 0.270 eV and 0.044, 0.025, 0.014, 0.217 eV, respectively, indicative of fast rate capabilities. At the same time, the Be2Al and Be2Ga monolayers exhibit the desirable mean open-circuit voltages of 0.049 and 0.104 V for Li+, 0.234 and 0.278 V for Na+, 0.249 and 0.227 V for K+, as well as 0.120 and 0.124 V for Ca2＋, respectively, conducive to achieve high operating voltage at the full-cell level. Arising from stable double-sided multilayer adsorption, the Be2Al (Be2Ga) monolayer can deliver ultrahigh reversible specific capacities up to 2382 (1222), 4764 (1833), 2382 (1222), and 7146 (3665) mA h g−1 for Li, Na, K, and Ca atoms, respectively. All of these advantages along with reliable cycling stability demonstrate that these two 2D materials enjoy great potential as promising anodes for Li, Na, K, and Ca ions batteries.

Combination of Efficient Red Fluorescence and High Photothermal Conversion in the Second Near‐Infrared Window from Carbon Dots through Photoinduced Sodium‐Doping Approach

AbstractCarbon dots (CDs) are highly desired in biological applications. However, achieving a balance between photoluminescence (PL) efficiency and photothermal conversion efficiency (PTCE) is challenging. In this study, an unprecedent combination of efficient red fluorescence and high PTCE in the second near‐infrared (NIR‐II) window in a sodium‐doped CDs system is reported. Upon 808 nm laser irradiation, photo‐induced oxidation–reduction reactions happened on the surface of sodium cation‐functionalized CDs (Na‐CDs), leading to the partial reduction of surface‐functionalized sodium (Na) ions. The photo‐reduced Na atoms coordinated with sp2 C domains in the core, resulting in Na‐doped CDs (ir‐Na‐CDs) with an enhanced absorption band in the NIR‐II window and a high PTCE of 43% under 1064 nm laser irradiation (1 W cm−2). Composing the ir‐Na‐CDs with bovine serum albumin (BSA) enhanced the PLQY of the red emission to 31% in water without diminishing the PTCE in the NIR‐II region. Transient absorption spectra revealed that no energy transfer occurred between the red emission center and the NIR‐II absorption band, revealing a novel CDs system with independent Janus photophysical processes. Moreover, ir‐Na‐CDs@BSA exhibited negligible to low cytotoxicity and demonstrated tumor accumulation capacity after intravenous injection, enabling effective tumor photothermal therapy in the NIR‐II region.

Highly Dense N-N-Bridged Dinitramino Bistriazole-Based 3D Metal-Organic Frameworks with Balanced Outstanding Energetic Performance.

Due to the inherent conflict between energy and safety, the construction of energetic materials or energetic metal-organic frameworks (E-MOFs) with balanced thermal stability, sensitivity, and high detonation performance is challenging for chemists worldwide. In this regard, in recent times self-assembly of energetic ligands (high nitrogen- and oxygen-containing small molecules) with alkali metals were probed as a promising strategy to build high-energy materials with excellent density, insensitivity, stability, and detonation performance. Herein, based on the nitrogen-rich N,N'-([4,4'-bi(1,2,4-triazole)]-3,3'-dial)dinitramide (H2BDNBT) energetic ligand, two new environmentally benign E-MOFs including potassium [K2BDNBT]n (K-MOF) and sodium [Na2BDNBT]n (Na-MOF) have been introduced and characterized by NMR, IR, TGA-DSC, ICP-MS, PXRD, elemental analyses, and SCXRD. Interestingly, Na-MOF and K-MOF demonstrate solvent-free 3D dense frameworks having crystal densities of 2.16 and 2.14 g cm-3, respectively. Both the E-MOFs show high detonation velocity (VOD) of 8557-9724 m/s, detonation pressure (DP) of 30.41-36.97 GPa, positive heat of formation of 122.52-242.25 kJ mol-1, and insensitivity to mechanical stimuli such as impact and friction (IS = 30-40 J, FS > 360 N). Among them, Na-MOF has a detonation velocity (9724 m/s) superior to that of conventional explosives. Additionally, both the E-MOFs are highly heat-resistant, having higher decomposition (319 °C for K-MOF and 293 °C for Na-MOF) than the traditional explosives RDX (210 °C), HMX (279 °C), and CL-20 (221 °C). This stability is ascribed to the extensive structure and strong covalent interactions between BDNBT2- and K(I)/Na(I) ions. To the best of our knowledge, for the first time, we report dinitramino-based E-MOFs as highly stable secondary explosives, and Na-MOF may serve as a promising next-generation high-energy-density material for the replacement of presently used secondary thermally stable energetic materials such as RDX, HNS, HMX, and CL-20.

Boosting the capacity and stability of Na3V2(PO4)2F3-2xO2x microspheres, using atomic layer deposition of artificial CEI

Phosphate-based materials [e.g. Na3V2(PO4)2F3-2xO2x; (NVPFO2x;0 < x < 1)] are regarded as a promising intercalation cathodes for Sodium-ion batteries (SIBs) due to their high reversible specific capacity and stability. However, so far only 2 Na ion were demonstrated to be active in these polyanionic cathodes, which limit their capacity. Herein we provide a strategic approach towards electrochemical activation of a 3rd Na ion, which leads to higher capacity, and preserves structural integrity. We synthesize and study a series of NVPFO2x (0 < x < 1) with well-controlled surface morphology and vanadium oxidation state, and study the dependence of the electrochemical behavior on the various composition and morphology. The optimized NVPFO cathode exhibited highest initial specific discharge capacity (131 mA h g−1) indicating the activation of 3rd Na ion. Nevertheless, the material suffers rapid capacity fading within ~50 cycles. We demonstrate how this instability is suppressed profoundly through the formation of a thin artificial cathode electrolyte interface (CEI) layer of TiO2 (ca. 2 nm) on the surface of NVPFO by atomic layer deposition (ALD). This TiO2 coating enabled even further extraction of sodium through higher voltage domain, but more importantly, it facilitated excellent long-term stability over 200 cycles. The structural stability of the cathode material was revealed by post cycling HRSEM, XPS, and XRD study. All these studies demonstrate that the thin TiO2 layer effectively contributes to formation of a robust CEI layer, diminishes the parasitic reaction on the electrode surface, reduces carbonate formation, and restricts the electrolyte decomposition.

Phase change electrolytes for combined electrochemical and thermal energy storage

Inorganic salt-based phase change materials (PCMs) form the basis of next-generation thermal energy storage technologies that store and release energy at temperatures relevant for regulating energy usage in residential environments. Here, we detail a rational approach for designing a multifunctional electrolyte that stores latent heat using polymer-stabilized sodium sulfate and sodium thiosulfate mixture. This formulated PCM also allows rapid sodium ion transport in both the solid and liquid states. This PCM composite electrolyte was prepared by blending the components at elevated temperatures, forming a viscous liquid that can serve as a gel-electrolyte for Na-ion batteries. The addition of sodium borate as a nucleating agent resulted in a PCM composite electrolyte with fusion enthalpy (120 J/g) and a phase transition centered around 25.0 °C with 11 °C supercooling. This PCM electrolyte showed excellent thermal cycling stability (>10 cycles) that also maintains high ionic conductivity (>10 mS cm−1). We show that the electrolyte enables Na ion cycling of the dual anode/cathode material, Na2VTi(PO4)3. These properties make this composite electrolyte a promising material for multifunctional energy storage devices.

Removal Cr(VI) from tunneling wastewater by Fe-containing sludge biochar: The role of endogenous iron

Fe-containing sludge biochar produced by pyrolysis of Fe-containing residual municipal sludge was utilized for removing Cr(VI) from aqueous solutions. It was observed that increasing the solution pH decreased the adsorption performance of FSBC for Cr(VI), while raising the adsorption temperature enhanced Cr(VI) removal on FSBC. The coexisting ions of Na+, K+, SO42- and NO3- had minimal impact on removing Cr(VI) by FSBC, whereas the divalent cation of Ca2+ and Mg2+ exhibited a slight inhibitory influence on removing Cr(VI). Both the pseudo-first-order and Langmuir model were found to better describe the Cr(VI) removal process on FSBC from aqueous solutions. The mechanisms involved in removing Cr(VI) by FSBC may include complexation, electrostatic interaction and reduction processes. The Fe species present on FSBC were identified as both Fe2O3 and Fe3O4, with Fe3O4 disappearing after removing Cr(VI). The Fe species on FSBC provided Fe-O groups as site for removing Cr(VI), while Fe3O4 facilitated the Cr(VI) reduction by FSBC. This findings offered further viewpoints into removing Cr(VI) from aqueous solutions using Fe-containing sludge biochar.

Confining Polymer Electrolyte in MOF for Safe and High‐Performance All‐Solid‐State Sodium Metal Batteries

AbstractNanoconfined polymer molecules exhibit profound transformations in their properties and behaviors. Here, we present the synthesis of a polymer‐in‐MOF single ion conducting solid polymer electrolyte, where polymer segments are partially confined within nanopores ZIF‐8 particles through Lewis acid‐base interactions for solid‐state sodium‐metal batteries (SSMBs). The unique nanoconfinement effectively weakens Na ion coordination with the anions, facilitating the Na ion dissociation from salt. Simultaneously, the well‐defined nanopores within ZIF‐8 particles provide oriented and ordered migration channels for Na migration. As a result, this pioneering design allows the solid polymer electrolyte to achieve a Na ion transference number of 0.87, Na ion conductivity of 4.01×10−4 S cm−1, and an extended electrochemical voltage window up to 4.89 V vs. Na/Na+. The assembled SSMBs (with Na3V2(PO4)3 as the cathode) exhibit dendrite‐free Na‐metal deposition, promising rate capability, and stable cycling performance with 96 % capacity retention over 300 cycles. This innovative polymer‐in‐MOF design offers a compelling strategy for advancing high‐performance and safe solid‐state metal battery technologies.

Pyrazinoquinoxaline graphdiyne: A novel high-capacity anode material for metal-ion batteries

The rapid expansion of the electronics industry and the growing need for advanced energy storage solutions have driven the quest for rechargeable batteries with improved capacity and prolonged lifetimes. In this context, significant attention has been directed towards the exploration of two-dimensional (2D) materials, particularly carbon nanosheets such as Graphdiyne, owing to their compelling electrical, optical, mechanical, and chemical properties. The recent achievement in producing pyrazinoquinoxaline graphdiyne (PQ-GDY) nanosheets, distinguished by their remarkable stability and exceptional physical properties, has ignited our research curiosity, prompting an exploration of their potential suitability as anode materials for lithium (Li), sodium (Na), calcium (Ca), and magnesium (Mg) ion batteries. This investigation is conducted using first-principle electronic structure simulations. Drawing from our rigorous theoretical analysis, pyrazinoquinoxaline graphdiyne (PQ-GDY) has demonstrated favorable electrode properties, positioning it as a promising candidate for potential utilization in Li, Na, and Ca ion batteries. Notably, the pyrazinoquinoxaline graphdiyne rectangular (PQ-GDY-Rec) material demonstrates remarkable storage capacities for Li, Na, and Ca ions, reaching values of 1938 mAh/g, 1716 mAh/g, and 830.60 mAh/g, respectively. These findings position PQ-GDY-Rec as a highly promising material for application in metal-ion batteries, suggesting new avenues for the advancement of rechargeable batteries with significantly enhanced storage capabilities.

Achieving rapid sodiation/desodiation kinetics in NASICON-structured Na3MnTi(PO4)3 via Cr doping

Na3MnTi(PO4)3 is one of the most promising cathode candidates for sodium-ion batteries owing to its low cost, high operating voltage, and large reversible capacity. However, its electrochemical performance is significantly impeded by its deteriorative structure and sluggish Na+ diffusion kinetics. Herein, Cr-doping is introduced to tailor the structure of Na3MnTi(PO4)3, which helps to lengthen the Na2-O bond and expand the Na ion diffusion channels. X-ray diffraction, cyclic voltammetry, galvanostatic intermittent titration technique, and first principle calculations confirm the broadened diffusion channel for Na+ and facilitated Na+ diffusion rate after Cr-doping. As a result, the Na3.1MnTi0.9Cr0.1(PO4)3 electrode exhibits superior electrochemical performance with high discharge capacity (167.5 mAh g–1 at 0.1 C), outstanding rate capability (127.5 mAh g–1 at 10 C), and remarkable cyclability (70.56 % retention after 1400 cycles at 5 C). We believe that the results are useful for the design of high-performance NASICON-structured cathode materials for practical sodium-ion batteries.

Study on the Sodium-Doped Titania Interface-Type Memristor.

Memristors integrated into a crossbar-array architecture (CAA) are promising candidates for analog in-memory computing accelerators. However, the relatively low reliability of the memristor device and sneak current issues in CAA remain the main obstacles. Alkali ion-based interface-type memristors are promising solutions for implementing highly reliable memristor devices and neuromorphic hardware. This interface-type device benefits from self-rectifying and forming-free resistive switching (RS), and exhibits relatively low variation from device to device and cycle to cycle. In a previous report, we introduced an in situ grown Na/TiO2 memristor using atomic layer deposition (ALD) and proposed a RS mechanism from experimentally measured Schottky barrier modulation. Self-rectifying RS characteristics were observed by the asymmetric distribution of Na dopants and oxygen vacancies as the Ti metal used as the adhesion layer for the bottom electrode diffuses over the Pt electrode at 250 °C during the ALD process and is doped into the TiO2 layer. Here, we theoretically verify the modulation of the Schottky barrier at the TiO2/Pt electrode interface by Na ions. This study fabricated a Pt/Na/TiO2/Pt memristor device and confirmed its self-rectifying RS characteristics and stable retention characteristics for 24 h at 85 °C. Additionally, this device exhibited relative standard deviations of 27 and 7% in the high and low resistance states, respectively, in terms of cycle-to-cycle variation. To verify the RS mechanism, we conducted density functional theory simulations to analyze the impact of Na cations at interstitial sites on the Schottky barrier. Our findings can contribute to both fundamental understanding and the design of high-performance memristor devices for neuromorphic computing.

Swelling behavior of calcium ion-crosslinked sodium alginate in an in vitro hemostatic tamponade model

Various types of hemostatic agents are used to manage bleeding in surgery. Many such agents are animal products, which carry the risk of secondary infection. The aim of this study is to develop a novel hemostatic agent from a non-animal source that quickly stops bleeding, is easy to use, and has no risk of infection.In this study, we synthesized calcium ion-crosslinked sodium alginate (Alg-Na/Ca) by partial substitution of Ca ions for Na ions in sodium alginate. We prepared 12 kinds of Alg-Na/Ca powders with different Ca mass ratios, molecular weights, M/G ratios and particle size distributions and measured their swelling ratio and the burst pressure generated. We found that Alg-Na/Ca began to swell immediately after contact with saline, especially Alg-Na/Ca at Ca mass ratios of 74.1–77.0 % showed a high swelling ratio after 2 min and a high burst pressure, over 200 % and 500 mmHg respectively. Also, there is a correlation between the swelling ratio after 2 min and the burst pressure. Our results suggest that, by optimizing the composition conditions, Alg-Na/Ca may be an effective hemostatic agent that could act as a tamponade by absorbing and swelling at a bleeding site to quickly achieve primary hemostasis.