Design Of Materials Research Articles

Flexible and washable MXene@PEDOT:PSS@CS@PU pressure sensors

Flexible electronics have attracted great interest because of their potential applications in healthcare monitoring and human-computer interaction. The performance of flexible electronics depends on the design of structure, materials, and mechanical responses. In this work, we explore the use of polyurethane (PU) sponge as the scaffold to form flexible piezoresistive pressure sensors with conductive networks made from conductive polymer PEDOT:PSS and MXene nanosheets. The sensitivity of the prepared pressure sensors reaches 0.2171 kPa−1 under mechanical pressure in a range of 1.8–6.15 kPa. The prepared pressure sensors are re-usable after washing. The applications of the prepared pressure sensors in the sensing of physiological behavior are demonstrated under the action of finger tapping, finger bending, vocal cord vibration, swallowing, and pulsing of radial artery. The prepared pressure sensors have great prospects for applications in human-machine interaction and physiological diagnosis.

Development of a novel characterization model for innovative bionic helical carbon fiber tows

The design of bionic helical structures significantly enhances load-bearing capacity and impact resistance, demonstrating great potential for mechanical property improvement. However, there is still a lack of precise characterization models for the helical structures of carbon fibers, which constrains their potential in engineering applications. This paper successfully fabricated helical carbon fiber tows using a carbon fiber twisting technique and introduced a novel intersecting circular cross-section model to thoroughly investigate the influence of the helical structure on the mechanical properties of carbon fiber tows. Tensile test results show that at a twist angle of 5°, the helical structure increases the tensile strength and fracture toughness of carbon fiber tows by 13.6% and 34.3%, respectively. Additionally, the introduction of complex structures such as helices significantly influences the material’s modulus, and precise modulus prediction is crucial for material optimization and practical application. Based on the newly proposed model, a modulus prediction model is developed, demonstrating higher predictive accuracy than traditional models with a prediction error of 2.8%. Finite element simulations further validate the practicality and superiority of the intersecting circular cross-section model. Compared to traditional models, the predictions of the novel model are closer to experimental data, with a prediction error below 2%, emphasizing the significant impact of microstructures on macroscopic properties and offering a new perspective for modeling complex material systems. These findings provide crucial theoretical and methodological support for the design and performance optimization of carbon fiber materials.

Hydrogen evolution from NaBH4 using novel Ni/Pt nanoparticles decorated on a niobium-based composite

The niobium-based nanocomposite (Nb-CP), inspired by MOF-based synthesis, was developed utilizing the ligands 4-benzenedicarboxylic acid (BDC) and 1,3,5-benzenetricarboxylic acid (BTC). This material was decorated with bimetallic nanoparticles (Ni2/Pt8 NPs-Nb-CP) and applied for the first time for hydrogen evolution from sodium borohydride (NaBH4). Characterization results indicated successful synthesis. The FT-IR analysis revealed the presence of functional groups such as -C-H, –CO, and -O-H from ligands in the composite. Thermogravimetric analysis confirmed the thermal stability of the niobium composite (Nb-CP). Through X-ray diffraction (XRD), peaks associated with sodium niobate were detected. Additionally, the material was functionalized with bimetallic Ni/Pt nanoparticles, whose presence was also identified by XRD. The cubic morphology of the material was observed, with the decoration of bimetallic nanoparticles (Ni2/Pt8 NPs-Nb-CP) with an average size of 7.80 ± 0.10 nm, uniformly distributed in Nb-CP. The catalytic performance of the material was evaluated in hydrogen evolution from NaBH4. Various reaction parameters were investigated, such as nanoparticle composition, variation in NaBH4 concentration, catalyst dose, NaOH concentration, and temperature. Remarkably, the material exhibited a hydrogen generation rate (HGR) of 1782 mL min−1 g−1cat and an activation energy of 23.1 kJ mol−1. Furthermore, it demonstrated efficiency close to 100% over 16 consecutive reaction cycles, indicating its promising stability and reusability. This study highlights the potential of Ni2/Pt8 NPs-Nb-CP as an efficient and durable catalyst for hydrogen production through borohydride hydrolysis, providing insights into the design and application of advanced heterogeneous catalytic materials.

AsTe3: A novel crystalline semiconductor with ultralow thermal conductivity obtained by congruent crystallization from parent glass

The synthesis of novel narrow-band-gap semiconductors with ultralow thermal conductivity opens a pathway to the design of functional materials with high thermoelectric performance or with interesting optical sensitivity in the infrared range. Here, we report on the discovery of the novel crystalline binary AsTe3 (c-AsTe3) prepared by spark plasma sintering (SPS) from full and congruent crystallization of amorphous AsTe3 (a-AsTe3) previously prepared by twin roller quenching. X-ray diffraction suggests that the structure of c-AsTe3 can be described as a superstructure of elementary Te with a specific distribution of As and Te atoms. More specifically, it appears as an intergrowth of a Te subunit (3 atoms) and As2Te5 subunit (6 As + 15 Te atoms) separated with interlayer spaces. The optical transmittance measured on both crystalline and amorphous AsTe3 indicates a maximum transmittance of 22 % over the infrared range 10–25 µm. Transport properties measurements, performed between 5 and 375 K, reveal that AsTe3 behaves as a lightly doped, p-type semiconductor. The complex crystal structure combined with a small-grain-size microstructure of the sample yields extremely low lattice thermal conductivity values of 0.35 W m−1 K−1 near 300 K. This poor ability to conduct heat is the main property that gives rise to an estimated dimensionless thermoelectric figure of merit ZT of ∼0.3 at 375 K. These findings show that the recrystallization of amorphous phases by SPS provides an effective approach for stabilizing novel phases with interesting functional properties.

Diffusion and defect chemistry of temperature-stable BaTiO3-based ceramics: Experiment and theoretical calculations

The ion diffusion and defect chemistry are the key factors in constructing the core-shell structure and improving the dielectric properties in temperature-stable BaTiO3-based dielectric ceramics. In this work, the BaTiO3-based ceramics doped with various rare-earth (RE) elements are prepared via the chemical coating method. The metal vacancy assisted A-B jumping migration path is confirmed as the main migration mechanism, where larger RE ions migrate faster and facilitate grain growth. About ∼1 mol% of amphoteric rare-earth ions are necessary to trap the oxygen vacancies and increase the activation energy and depolarized temperature. The electron paramagnetic resonance and thermodynamic model reveals that Mn4+ is not detected in all samples and the content of Mn2+ is determined by the Fermi level of the systems, influenced by the donor/acceptor doping, concentrations, and oxygen partial pressure. This work provides support for the rational design of dielectric materials with excellent dielectric performance and good reliability.

Advancing first-principles dielectric property prediction of complex microwave materials: an elemental-unit decomposition approach

Tungsten-bronze-type material Ba6-3xRE8+2xTi18O54, (RE = rare earth elements) is an important microwave dielectric that has shown great promises for future miniaturization of microwave devices because of its high dielectric constant, low loss, and tunabilities, and there is still much room for improvement. With their proven predictive power, first-principles calculations may greatly help accelerate materials optimization by reducing or eliminating the expensive and time-consuming experimental trial-and-error process. However, microwave dielectrics such as the tungsten-bronze-type materials are rather complex systems with unit cells containing hundreds or thousands of atoms, making ab initio calculations prohibitively expensive. In this work, we propose an elemental-unit decomposition (EUD) technique that can drastically reduce the computational effort of predicting the properties of complex microwave dielectrics and demonstrate its accuracy and efficiency. Our approach facilitates first-principles prediction and design of complex microwave dielectric materials that would otherwise be extremely difficult.

Efficient mitigation of lithium dendrite by two-dimensional A-type molecular sieve membrane for lithium metal battery

Uneven lithium deposition poses a primary challenge for lithium-ion batteries, as it often triggers the growth of lithium dendrites, thereby significantly compromising battery performance and potentially giving rise to safety concerns. Therefore, the high level of safety must be guaranteed to achieve the large-scale application of battery energy storage systems. Here, we present a novel separator design achieved by incorporating a two-dimensional A-type molecular sieve coating onto the polypropylene separator surface, which functions as an effective lithium ion redistribution layer. The results demonstrated that even after undergoing 1000 cycles, the cell equipped with a two-dimensional A-type molecular sieve-Polypropylene (2D-A-PP) separator still maintains an impressive capacity retention rate of 70 %. In contrast, cells equipped with Polypropylene (PP) separators exhibit capacity retention rates below 50 % after only 500 cycles. Additionally, the incorporation of a two-dimensional molecular sieve enhances the mechanical properties of the PP separator, thereby bolstering battery safety. This study proposes a novel concept for the design of lithium-ion battery separator materials, offering a fresh perspective on the development of separators with exceptional thermal stability, enhanced porosity, superior electrolyte affinity, and effective inhibition of lithium dendrite formation.

Prediction of thermal conductivity in UO2 with SiC additions and related decisive features discovery

Next-generation accident-tolerant fuels for light-water reactors (LWRs) are being developed with high thermal conductivity additives. To reduce the high centerline temperatures that occur in present LWR fuel, complex fuels with improved heat dissipation capabilities are the goal. Depending on the manufacturing process, these fuels can use a variety of additives, and their microstructures vary. The thermal conductivity of UO2-SiC complex fuel is predicted using the finite element method (FEM) and machine learning (ML), as shown in this research. The method accurately predicts the corresponding complex fuel thermal conductivity and captures the characteristic value successfully. Novel anisotropic fuel pellets with higher thermal conductivity in a desired direction can be designed through the application of FEM and ML to material design. Data from published experiments with UO2-SiC complex fuel are used to validate the model and methodology. The model finally predicts the ideal characteristic parameters of the UO2-SiC based on the expected thermal conductivity.

Strengthening high-nitrogen austenitic stainless steel via constructing multi-scaled heterostructure

High nitrogen austenitic stainless steels (HNASSs) have received widespread attention owing to their outstanding corrosion resistance, excellent weldability and workability. However, these materials usually exhibit insufficient yield strength to satisfy the requirement in service because of their face-centered cubic (fcc) structure. Here, we report a novel material design strategy of constructing both grain-scaled and atomic-scaled heterostructure through applying appropriate thermo-mechanical treatment to improve the comprehensive mechanical properties of HNASS. The optimal comprehensive mechanical properties with a yield strength of 1361 MPa and a uniform elongation of 10.6% are achieved. The results show that the ultrahigh yield strength mainly originates from the lath structure consisting of local chemical order domains (∼490 MPa), and the satisfactory ductility benefits from both deformation twinning and dislocation slip. This work proposes for the first time the strategy to improve mechanical properties of HNASS by introducing the multi-scaled heterostructure, and guides the development of high-performance steels and many other advanced fcc materials.

Synergistic effects of multi-dimensionality in an aerogel for lithium-ion battery anodes with an enhanced capacitive contribution

The rational design of anode materials is important when seeking to produce high-performance lithium-ion batteries (LIBs) that offer both a high-power density (P) and a high energy density (ε). In this study, a multi-dimensional aerogel composed of 1-dimensional (1D) and two-dimensional (2D) nanostructures was synthesized. To impart conductivity and dimensional diversity, reduced graphene oxide (rGO) nanoplates were introduced to a 1D Co-S aerogel using a metal coordination-assisted sol–gel method. As the anode material for an LIB, the resulting multi-dimensional rGO@Co-S aerogel with 1.4 wt% GO exhibited outstanding electrochemical performance, with a high specific capacity, high-rate capability, strong cycling stability (84 % at 0.5 A/g after 350 cycles), an excellent P (9,660 W/kg), and a high ε (1,566 Wh/kg). This was attributed to the shorter ion and electron diffusion paths arising from the multi-dimensional structure, coupled with the higher surface area and enhanced capacitive contribution due to the addition of the rGO nanoplates.

Novel Fe1.1Co1.1(CrAlx)1.8Gd0.1 high-entropy alloy absorber: Noticeable ferromagnetic transformation and enhanced magnetic loss

High-entropy alloys (HEAs) with excellent soft magnetic properties are gradually emerging as a new generation of electromagnetic wave (EMW) absorption materials. Existing HEAs still cannot efficiently absorb EMW due to inadequate magnetic properties. This paper aims to modulate the ferromagnetic properties of Fe1.1Co1.1(CrAlx)1.8Gd0.1 (x=1, 1.2, 1.4, 1.6) to enhance the permeability and achieve efficient absorption of EMW. The experimental results show that when the ratio of Al to Cr is 1.6:1, the saturation magnetization and permeability reach their highest values. First-principles calculation confirms from an atomic perspective that when the ratio of Al to Cr is 1.4:1, Gd begins to undergo a ferromagnetic transformation. Its magnetic moment increases from −1.2μΒ to 1.4μΒ, and the degree of electron localization also increases. The Fe1.1Co1.1Cr0.75Al1.05Gd0.1 achieves an effective absorption of −51 dB at a thin thickness of 2 mm and an effective absorption bandwidth of 6.2 GHz of 1.4 mm. The cocktail effect also depends on having good corrosion and oxidation resistance. This paper provides theoretical guidance for the design of high-performance soft magnetic EMW absorption materials.

Material Design and Discovery in Full-Heusler Compounds: A Comprehensive First-Principles Analysis of XMg2Hg, XMgHg2, and X2MgHg (X = Sc, Li)

This study conducts a comprehensive first-principles analysis of the structural, mechanical, phonon dispersion, and electronic properties of XMg2Hg, XMgHg2, and X2MgHg (X = Sc and Li) compounds. Using energy-volume curves, cohesive and formation energy, and phonon dispersion analyses, we confirm the stability of these compounds. Our calculations reveal that Li2MgHg and ScMg2Hg are more stable in the cubic structure with space group F4¯3m (216), whereas other compounds are stable in the Fm3¯m (225) structure. Phonon dispersion calculations indicate dynamical stability for all compounds except Li2MgHg in the Fm3¯m structure and Sc2MgHg and LiMg2Hg in the cubic structure with space group F4¯3m (216). Mechanical stability is confirmed through the calculation of elastic constants, with Sc-based compounds showing higher bulk modulus, shear modulus, and Young's modulus compared to Li-based compounds. Electronic properties, analyzed through density of states and band structure calculations, confirm the metallic nature of these compounds, with significant contributions from Mg atoms at the Fermi energy. The study also identifies distinct electronic features such as flat electron bands and a Dirac point at the Gamma point for ScMgHg2​. Pressure-dependent studies indicate these materials are normal metals without topological phase transitions.

Materials design using genetic algorithms informed by convolutional neural networks: Application to carbon nanotube bundles

Carbon nanotube (CNT) composites are promising but complex material systems whose mechanical response is influenced by many features, including CNT bundle microstructures. It is intractable to design CNT bundle microstructures using experiments and/or simulations alone. Thus, we implement a machine learning-based tool comprising a genetic algorithm (GA) (which aids in selecting features for bundle microstructures) and a convolutional neural network (CNN) (which rapidly predicts mechanical performance of bundle microstructures). Training data for the CNN are obtained from micromechanical finite element simulations. CNN predictions achieve R2>0.96 for elastic and shear moduli and R2>0.83 for Poisson’s ratios. Microstructures identified by the CNN-informed GA outperform between 79% and 100% of solutions found using a brute-force search and are found in less than 5% of the time, providing an efficient tool for informed materials design of CNT bundle microstructures.

Operando Tracking the Dissolution and Deposition Dynamics in Aqueous Zn-MnO2 Batteries

Aqueous Zn–MnO2 batteries have received extensive attention for next-generation large-scale energy storage because of their low cost and outstanding safety. Despite efforts to achieve better performances, the charge-storage chemistry of MnO2 cathodes remains controversial. Zn-ion insertion, Zn-ion/proton co-insertion, proton insertion, and electro-dissolution have been proposed as the mechanism of the MnO2 cathodes. More specifically, the pathway of Mn dissolution is debatable: while intercalation chemistry leads to dissolution caused by the Jahn–Teller effect of Mn(III), electro-dissolution relies on a conversion from Mn(IV) to Mn(II). Furthermore, it is recently considered that Mn dissolution/redeposition efficiency is crucial to the reversibility of MnO2 cathodes, depending on pre-added Mn in the electrolyte. The role of trace Mn additive is also confusing. Last but not least, Mn dissolution and deposition is conjectured to be linked to the dissolution/redeposition of Zn‐based species-that is, Zn4SO4·(OH)6·xH2O (ZSH). To understand these key scientific questions that enlighten the further design of materials and electrolytes, it is imperative to develop operando measurements of the MnO2 cathodes. In our study, we utilized synchrotron X-ray fluorescence microscopy with high spatial resolution to probe the evolution of Zn and Mn species during electrochemical cycling. We can quantify the relationship between Zn and Mn concentrations from the electrode level to the single-particle level. We conclude that during the first discharge, MnO2 delivers the capacity by electro-dissolution, accompanied by the rapid precipitation of ZSH due to change of pH. ZSH surrounds the MnO2, which has high reversibility with the pre-added Mn additive in electrolytes. Our work provides in-depth insights into the complex Zn/Mn deposition and deposition near the electrode surface which will guide the further development of aqueous Zn-MnO2 batteries.

Stable Operation and Enhanced Sensitivity via Composite Structure Design for Efficient Photoplethysmography and Motion Sensors

Healthcare sensors have attracted lots of interests owing to saving a patient's life by continuously monitoring the patient's health via early diagnosis of the symptoms by using healthcare sensors. Many health-care sensors are available in wearable application that can monitor continuously patient health. There are some common parameters such as a heart rate and human motion that are used to monitor human activity.In order to realize stable operation of health-care sensors, material designs are required considering human-body compatibility. In this research, light-sensors fabricated from low-toxicity organic materials by introducing neutral poly(3,4-ethylenedioxythiophene)-(polystyrene sulfonate) (PEDOT-(PSS)) to improve human-body compatibility as well as to strengthen photoplethysmography (PPG) signal. [1] Neutral PEDOT-(PSS) with heterocyclic 1,3-diazole (HDZ) enhances the polymerization degree, carrier mobility, and other physicochemical properties. Consequently, the presented OPD-based PPG sensor has the ability to diagnose blood circulation status and cardiovascular diseases.Second, we fabricate motion sensors by utilizing metallic glass, i.e., amorphous metallic alloy, which is an alloy composition without grain boundaries and long-range ordering. The unique structure of metallic glass results in excellent tensile strength and strain-resistivity as well as chemical stability to those of conventional metals. The Al-Sm MG-based sensors results in enhanced sensitivity and considerable device stability, because of its amorphous phase. [2][1] Adv. Funct. Mater. 2023, 10.1002/adfm.202309271[2] Electrochimica Acta, 2023, 446, 142053

Carbon Nanotube-Based Catalyst Modification to Improve Proton Exchange Membrane Fuel Cell Interlayer Interactions

Proton exchange membrane fuel cells (PEMFC) were identified as a highly viable solution for addressing climate-related issues. Previous theoretical investigations have underscored the significance of Pt nanoparticles as the optimal metal for hydrogen fuel cell catalysts due to their special activity and selectivity. [1] Current works focused on the utilisation, durability, and site activity of Pt particles on support, and most of the schemes achieved performance enhancement by loading Pt onto porous support with different morphology such as graphene, carbon fibre, and carbon black. [2] Some schemes have also incorporated cost considerations to achieve lower Pt loading. [3] However, the design of the catalyst layer (CL) structure in the membrane electrode assembly (MEA) must consider the interactions between the layers.Addressing the crucial aspects of water management, low contact resistance, and the establishment of effective three-phase boundary for MEA, multi-walled carbon nanotubes (MWCNTs) are a promising CL support due to their intrinsically high hydrophobicity, high axial electrical conductivity, and potential for ordered alignment. [4] However, the drawbacks of MWCNTs such as strong agglomeration, wall surface chemical inertness, and unopened ends are unfavourable for Pt nanoparticle loading, which is detrimental to MEA processing and leads to inhomogeneous CL surfaces. This further deteriorates the utilisation of Pt and increases the contact resistance. Previous efforts have explored methods such as introduction of polar functional groups on MWCNT using strong reflux oxidation condition, or nitrogen doping to construct localised pyridine structure. [5, 6] However, over-functionalisation can cause MWCNT to lose its favourable structure and properties.In this work, MWCNT was modified based on the operational requirements of the MEA from the viewpoint of interlayer interactions, including the search for the optimal degree of oxidation, N-doping, and micro-arrangement. MWCNT were functionalise by oxidising, N-doping, as well as micro-alignment to achieve lower contact resistance between CL and proton exchange membrane (PEM), better hydrophobicity, and enhanced performance. Furthermore, this work expects to construct a more continuously distributed three-phase boundary by aligning MWCNT to form a locally ordered structure, which is essential for the efficient utilisation of Pt active sites.Preliminary experiments in this work have tested a range of reflux oxidation conditions for MWCNT treated with concentrated nitric acid ranging from 0 to 10 h. The maximum power density of 979.81 mw cm-2 was achieved by Pt loading on 6h MWCNT oxidation time (Pt-MWCNT 6h). This represented a 59.53% improvement over the commercial Pt/C catalyst of 614.17 (mw cm-2) (Figure 1 (a)). In addition, due to the stronger electrical conductivity, the charge transfer resistance of Pt-MWCNT6h in the electrochemical impedance spectroscopy (EIS) test was 0.09 Ohm cm-2, which was 48.86% lower than that of Pt/C (Figure 1 (b)). This study will discuss the developed catalysts and their efficacy in a working fuel cell system.In conclusion, this research proposed alternative perspectives on the design of the CL based on the actual operational characteristics of MEA with emphasised on the interlayer interaction between CL and other layer. Additionally, the research will validate the impact of low-functionalization modification of MWCNTs on the performance of PEMFC, which simplifying the preparation challenges of CL and contributing for the widespread commercial application of PEMFCs on a larger scale. References Seh, Z.W., et al., Combining theory and experiment in electrocatalysis: Insights into materials design. Science, 2017. 355(6321): p. eaad4998.Sui, S., et al., A comprehensive review of Pt electrocatalysts for the oxygen reduction reaction: Nanostructure, activity, mechanism and carbon support in PEM fuel cells. Journal of Materials Chemistry A, 2017. 5(5): p. 1808-1825.Tian, Z.Q., et al., A Highly Order-Structured Membrane Electrode Assembly with Vertically Aligned Carbon Nanotubes for Ultra-Low Pt Loading PEM Fuel Cells. Advanced Energy Materials, 2011. 1(6): p. 1205-1214.Lehman, J.H., et al., Evaluating the characteristics of multiwall carbon nanotubes. Carbon, 2011. 49(8): p. 2581-2602.Hernández-Fernández, P., et al., Functionalization of multi-walled carbon nanotubes and application as supports for electrocatalysts in proton-exchange membrane fuel cell. Applied Catalysis B: Environmental, 2010. 99(1): p. 343-352.Gribov, E.N., et al., Effect of modification of multi-walled carbon nanotubes with nitrogen-containing polymers on the electrochemical performance of Pt/CNT catalysts in PEMFC. Materials for Renewable and Sustainable Energy, 2019. 8(1): p. 7. Figure 1

Gem-Difluoroalkylation of Cyclic Ethers Enabled by Cobalt-Catalyzed C(sp3)-H Oxidation under Mild Conditions.

Fluorinated rings have emerged as privileged structural modules in the fields of drug discovery and materials research. The incorporation of fluorine atoms into aromatic rings or heterocycles can lead to significant improvements in the physicochemical and biological properties of small molecules, making them valuable components in the design of new drugs and functional materials. Herein, we presented a cobalt-catalyzed C-H oxidation/gem-difluorination cascade reaction of readily available cyclic ethers with difluoroenoxysilanes, affording a series of gem-difluorinated analogues with moderate to high yields. The obtained products as versatile fluoroalkyl building blocks were showcased through divergent-oriented transformations.

Addressing the Key Challenges of Lithium-Sulfur Batteries: A Comprehensive Overview and Future Perspectives

Introduction: Lithium-sulfur (Li-S) batteries represent a pioneering technology with the potential to revolutionize energy storage due to their high theoretical energy density and cost-effectiveness. Nevertheless, their practical implementation encounters various challenges, hindering widespread commercialization. This abstract aims to explore the critical hurdles facing Li-S batteries and proposes strategies to advance their development into a sustainable and efficient energy storage solution. The primary obstacles for Li-S batteries encompass issues related to the polysulfide shuttle effect, sulfur's poor conductivity, limited cycle life, and significant volume changes during charge-discharge cycles. Moreover, achieving stable and efficient sulfur cathodes and electrolytes remains a crucial concern for ensuring prolonged battery performance. This review focuses on a range of strategies and innovations addressing these challenges, including advanced material design, conductive additives, novel electrolytes, and modified separator designs, all aimed at enhancing electrochemical performance. Advanced techniques such as computational modeling and machine learning play a pivotal role in accelerating the discovery and optimization of materials and architectures for Li-S batteries. These methodologies enable precise prediction, design, and evaluation of materials, expediting breakthroughs in overcoming limitations. The future of Li-S batteries relies on multidisciplinary research encompassing material science, electrochemistry, engineering, and computational methodologies.Keywords: Li – S batteries, Energy density, Cycle life, electrolyte design, cost-effectiveness

Exploring Order/Disorder Molecular Networks on Metal Surfaces

Materials featuring disordered structures often exhibit unique properties. Metal-organic frameworks (MOFs) are a class of hybrid materials composed of metal nodes and coordinating organic linkers[1]. Recently, there has been growing interests in MOFs with structural disorder, and the investigations of amorphous structures on surfaces[2]. Herein, we demonstrate a bottom-up method to construct molecular networks on metal surfaces with order-disorder transition by preparing two-component samples with different stoichiometric ratios of two organic molecule linkers sharing the same symmetry but differing in size[3]. We investigate the topological and electronic structures of the order/disorder molecular networks by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) under ultra-high vacuum (UHV). The results may advance our understanding of the formation mechanism and electronic behaviors characteristic of monolayer molecular networks with structural disorders, holding the potential to catalyze advancements in the design and application of new amorphous MOF materials with intriguing properties.[1] L. Dong, et al., Progress in Surface Science, 91, 101–135 (2016).[2] J. Fonseca, et al., Journal of Materials Chemistry A, 9.17, 10562-10611 (2021).[3] J. Lu, et al., ACS Nano, 17, 20, 20194–20202 (2023).

Grain Analysis of NCM Cathode Materials by ASTAR Technique and Its Effect on Battery Performance

Lithium-ion batteries (LIBs) are one of the most promising energy storage systems for portable electronic devices, electric vehicles, and renewable energy systems. Among the various cathode materials for LIBs, nickel cobalt manganese (NCM) oxide has attracted considerable attention due to its high specific capacity, good cycling stability, and appropriate cost for commercialization. However, Ni-rich NCM (Ni >80%) showed poor cyclability and huge gas evolution because of surface instability.Single crystal NCM has been suggested as a solution to these issues due to its excellent properties. However, it is difficult to quantify the degree of single crystallinity because it is so far subjective. In this study, we employed ASTAR technique (transmission electron microscopy combined with electron backscatter diffraction) to investigate the microstructural features of NCM cathode materials. Our ASTAR analysis showed that NCM cathode materials consist of complex grain and grain boundary structures with varying orientations and sizes. By analyzing the grain size and its morphology, we were able to define the single crystallinity of NCM cathode materials, including the poly NCM and single crystal NCM particles.Furthermore, we found that the grain size and its distribution significantly affects the battery performance and lifespan of NCM cathode materials. Specifically, the poly NCM particles exhibited a larger grain boundary and surface area compared to the single crystal NCM particles. The poly NCM particles also showed a faster DC-IR increase and a shorter lifespan than the single crystal NCM particles, indicating that the grain size has a critical influence on the battery performance and lifespan of NCM cathode materials.Our results provide insights into the design and optimization of NCM cathode materials for next-generation LIBs. By controlling the grain size and its distribution of NCM cathode materials, it is possible to enhance the battery performance and lifespan. Therefore, our study highlights the importance of understanding the microstructural features of NCM cathode materials for developing high-performance and stable LIBs.