Candidate Materials Research Articles

Measurement of the magnetic octupole susceptibility of PrV2Al20

Revealing the presence of magnetic octupole order and associated octupole fluctuations in solids is a highly challenging task due to the lack of simple external fields that can couple to magnetic octupoles. Here, we demonstrate a methodology for probing the magnetic octupole susceptibility of a candidate material, PrV2Al20, using a product of magnetic field Hi and shear strain ϵjk as a composite effective field, while employing an adiabatic elastocaloric effect to probe the response. We observe Curie-Weiss behavior in the obtained octupolar susceptibility down to approximately 3 K. Although octupole order does not appear to be the leading multipolar channel in PrV2Al20, our results nevertheless reveal the presence of strong magnetic octupole fluctuations and hence demonstrate that octupole order is at least a competing state. More broadly, our results highlight how anisotropic strain can be combined with magnetic fields to probe elusive ‘hidden’ electronic orders.

Enhanced thermoelectric performance of Hf-doped ZrNiSn: a first principle study.

In this work, we perform a systematic study on the thermoelectric properties of Zr1-xNiSnHfx using first-principles calculations combined with Boltzmann transport equations. The power factor of Zr1-xNiSnHfx increases as the temperature increases from 300 to 1200K, because the increase in electrical conductivity is greater than the decrease in the Seebeck coefficient. The power factor of Zr7/8NiSnHf1/8 is larger than that of other Zr1-xNiSnHfx thermoelectric materials, but the thermoelectric figure of merit (ZT) is similar to that of others materials. This is due to the higher electronic thermal conductivity of Zr7/8NiSnHf1/8 compared to other materials. The maximum ZT of p-type (n-type) Zr1-xNiSnHfx is 0.98 (0.97), 0.9 (0.89), 0.83 (0.80), and 0.72 (0.73) at 300K, 600K, 900K, and 1200K, respectively, which are greater than those of the pure ZrNiSn. In conclusion, Hf-doped ZrNiSn can enhance the thermoelectric performance and are promising candidates for thermoelectric materials. This paper uses FP-LAPW implemented in the WIEN2K code. The thermoelectric performance is calculated based on the semi-classical Boltzmann theory implanted using the BoltzTraP code. The electronic thermal conductivity (κe) and the carrier concentration (n) have been calculated using the density functional theory.

Exploring the inhibitory effect of WTaVCr high-entropy alloys on hydrogen retention: From dissolution, diffusion to desorption

Due to the excellent resistance to radiation damage, high-entropy alloys (HEAs) have been considered as important candidates for nuclear materials. However, to realize the great potential of HEAs in fusion energy, it is important to consider the hydrogen (H) behaviors, which remain to be elucidated. Here, we systematically investigate the dissolution, diffusion and desorption of H in equiatomic WTaVCr using the first-principles calculations. It is found that the H solution energy in WTaVCr is lower than that in pure W, which can be clarified by the H affinity of metallic elements and the available volume of interstitial sites. Accordingly, a possible diffusion path of interstitial H is selected, containing 26 metastable sites, and the corresponding energy barrier is 0.46 eV. Besides, the maximum trapping energy and accommodation number of H at a mono-vacancy in WTaVCr is only 0.30 eV and 3 ∼ 5 H, respectively, which is much lower than that in pure W (1.28 eV and 12 H). More importantly, because of the low trapping energy and moderate diffusion energy barrier, the desorption temperature of H from a mono-vacancy is lower than the room temperature, implying that vacancies are not efficient trapping centers for interstitial H atoms in WTaVCr. Therefore, although the equilibrium interstitial H concentration in WTaVCr is higher than that in pure W, H retention at high temperatures and H-induced blistering are suppressed due to the weak H-defect interactions. Our results will provide a good reference for understanding the H behaviors in HEAs.

Magnetic properties and large low-field magnetocaloric effect of RFe2Si2 (R = Ho, Tm) compounds

Nowadays, magnetic refrigerant technology has drawn much attention for its environmental friendliness. Those magnetic materials possessing giant low-field magnetocaloric effect (MCE) performance are of great importance for practical applications, especially at low temperatures. Herein, we present a detailed study on polycrystalline magnetocaloric compounds HoFe2Si2 and TmFe2Si2. HoFe2Si2 exhibits a transition from antiferromagnetic to paramagnetic phase at 2.2 K, while no long-range magnetic ordering is observed in TmFe2Si2 even temperature down to 2 K. For both compounds, they showed large low-field magnetic entropy change (−ΔSM) with the peak values of 10.6 and 7.9 J kg−1 K−1 under field change of 0–2 T for HoFe2Si2 and TmFe2Si2, respectively, which is comparable or even larger than some low-temperature magnetocaloric materials. In addition, the characteristic of second-order magnetic transitions of both compounds were confirmed on basis of Arrott plots and mean-field theory criterion. The low magnetic ordering temperatures, large low-field MCE performance along with the feature of second order phase transition for HoFe2Si2 and TmFe2Si2 indicate that both compounds are promising candidate for magnetic refrigerant materials at liquid helium temperature.

Spinel nickel ferrite (NiFe2O4) materials synthesized via spray-pyrolysis for electrochemical supercapacitor application

To explore potential applications of NiFe2O4-based supercapacitors in various energy storage systems, including portable electronic devices, electric vehicles, and grid energy storage, highlighting the advantages and challenges of using NiFe2O4 in these applications. To identify and propose future research directions for further improving the performance of NiFe2O4 supercapacitors. In the study focuses on optimizing concentration of synthesis to achieve desirable structural and electrochemical properties, characterizing the synthesized materials, and assessing their specific capacitance, energy density, power density, cycle stability, and rate capability. The different molar precursor solutions were utilized for the formation of NiFe2O4 thin films by using the cost-effective spray pyrolysis technique. The impact of different molarities on the structural, morphological, elemental, optical, and charge storage performance of NiFe2O4 thin films has been studied. In the XRD studies identified the cubic crystalline structure with Fd-3 m space group symmetry of NiFe2O4. The FE-SEM shows the grain-like surface morphology of NiFe2O4 thin films. The EDAX study reveals that NiFe2O4 thin films were stoichiometric. Bandgap energy values of the thin films were observed in the range of 1.97 to 2.2 eV with allowed direct band gap transitions. The maximum specific capacitance for NiFe2O4 thin film was found to be 707 Fg−1 at 2 mVs−1 with the wider potential window of − 0.8 to + 1 .6 V in 1 M KOH aqueous electrolyte. GCD study confirms the pseudocapacitive behavior of NiFe2O4 thin films. The maximum specific energy and specific power were found to be 83.88 WhKg−1 and 5.294 KWkg−1 at a current density of 0.002 Ag−1. Such as spinel ferrite NiFe2O4 thin film electrodes as an excellent candidate material for electrochemical supercapacitor applications.

A deep neural network potential model for transition metal diborides

Transition metal diborides (TMB2s) are renowned for their high melting point and exceptional wear, corrosion, and erosion resistance, making them promising candidate materials for applications in extreme environments. As such, there is an urgent need for reliable material design tools for TMB2s to improve efficiency in developing new materials. To address this need, we have developed a domain-specific medium-scale interatomic potential model for TMB2s that encompasses elements Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and B. The prediction errors in energy and force of our model are 8.8 meV/atom and 387 meV/Å, respectively. Furthermore, the model demonstrates high accuracy in predicting various material properties, including lattice parameters, elastic constants, equations of states, and melting points, as well as grain boundary segregations. By providing a reliable and efficient tool for material design, this model will play a crucial role in the development of new, high-performance TMB2s for use in extreme environments.

Biocompatibility, thermal and mechanical properties of glass fiber‐reinforced polybenzoxazine composites as a potential new endodontic post

AbstractA novel dental fiber post from glass fiber‐reinforced polybenzoxazine (PBZ) composites was developed in this work. The essential properties, that is, chemical characteristics, thermal and biological properties of the PBZ composites were investigated for various glass fiber loadings (10.5, 23.7, 41.2 and 65.1 vol%). Finite element analysis (FEA) was also utilized to observe mechanical behaviors of the tooth model repaired with PBZ composite posts compared to a natural tooth model. The findings reveal that for the fiber‐reinforced PBZ composites not only their thermal properties were significantly improved, but they also showed enhanced cytocompatibility; we found a coefficient of thermal expansion of 12.8 ppm/°C and cell viability of 91.55 for the 65.1 vol% glass fiber‐reinforced PBZ composite. Moreover, samples reinforced with higher glass fiber loadings effectively resulted in the reduction of stress distribution in dentin observed from FEA suggesting protection againt root fractures. Restoration using the PBZ composite post showed the same stress patterns in the dentin‐composite resin‐post interface of the repaired tooth as in the natural tooth model. The results revealed that the glass fiber‐reinforced PBZ composites possess good thermal properties and mechanical behaviors which renders them suitable candidates for biocompatible dental materials.Highlights The glass fiber/polybenzoxazine (GF/PBZ) composites had nontoxic properties as evidenced through cell viability, growth and morphology studies. The thermal expansion of the GF/PBZ composite was similar to that of dentin, promoting adaptation at the dentin‐post interface. Mechanical behaviors evaluated by FEA of tooth model restored with GF/PBZ composite post were similar to those restored with commercial glass fiber post. The biocompatible GF/PBZ composite with good thermal and mechanical properties is a promising new candidate material as dental fiber post.

Six‐principal‐component high‐entropy carbonitride aerogel thermal insulator: Theoretical and experimental studies

AbstractA combined theoretical and experimental approach was used to investigate high‐entropy carbonitride. Density functional theory (DFT) calculations suggest that the [N]/([C]+[N]) ratio in (Ti1/6Cr1/6V1/6Mo1/6Nb1/6Ta1/6)(C1−xNx) affects its lattice thermal conductivity which could be decreased by 89% by increasing the ratio from 0 to 1/2. Moreover, a robust, flame‐retardant and high‐temperature resistant (Ti1/6Cr1/6V1/6Mo1/6Nb1/6Ta1/6)(C0.64N0.36) high‐entropy carbonitride aerogel (6‐HECNA) was synthesized. It exhibited a porosity of 94.3%, a compressive strength of 0.9 MPa, and a good high‐temperature stability up to 1673 K. These properties, along with its outstanding fire‐retardancy, and low thermal conductivity (0.122 W·m−1·K−1 at 298 K), make it a promising candidate material for thermal insulation applications under harsh conditions.

Enhanced thermoelectric performance of n-type Mg3.2Sb1.5Bi0.5 by rare-earth elements (Er, Tb, Tm) doping into Mg site

The n-type Mg3.2Sb1.5Bi0.5 has emerged as a promising candidate for thermoelectric materials and has attracted significant research interest. However, effective n-type dopants have been predominantly limited to chalcogens. In our work, we found that rare-earth elements (Er, Tb, Tm) are highly effective dopants for n-type Mg3.2Sb1.5Bi0.5. Through a combination of theoretical predictions and experimental validations, we demonstrate that these dopants significantly enhance the carrier concentration, leading to improved thermoelectric performance. Specifically, we employed direct ball milling and spark plasma sintering to introduce rare-earth elements at the Mg sites. Experimental results show that doping rare-earth elements in n-type Mg3.2Sb1.5Bi0.5 has a higher carrier concentration ( ≈ 8.4 × 1019 cm−3), which is higher than that of chalcogen-doped samples ( ≈ 2 × 1019 cm−3). High power factor (S2σ) ≈ 16 μW cm−1K−2 was obtained in rare-earth elements (Er, Tb, Tm) doped samples. Combined with the lowered lattice thermal conductivity due to the introduction of effective phonon scattering centers in Mg3.2−xAxSb1.5Bi0.5 (A= Er, Tb, Tm) sample. Finally, the ZT values of all doped samples reached ≈ 1.44 at 750 K. The highest peak ZT is ≈ 1.65 at 750 K for Mg3.195Er0.005Sb1.5Bi0.5. The rare-earth elements (Er, Tb, Tm) doped n-type Mg3Sb1.5Bi0.5 has comparable thermoelectric performance with the chalcogen-doped n-type Mg3Sb1.5Bi0.5, exhibiting promising potential for practical applications. This present work offers a comprehensive understanding of the effect of cation site doping improves the thermoelectric properties of n-type Mg3Sb2.

Semi-metallic PtTe2 nanosheets are used as saturable absorbers to generate passive mode-locked pulse laser in the 2 μm band

In passively modulated pulse lasers, the highly stable saturable absorber (SA) used to generate passive pulsed lasers is a necessary core device. In this paper, layered PtTe2 nanosheets were fabricated using a simple, efficient, and low-cost liquid phase exfoliation (LPE) method, and PtTe2-SA devices were prepared by spin coating. Nonlinear optical tests show that the layered PtTe2 nanosheets have good nonlinear saturable absorption characteristics in the 2 μm band, with a modulation depth of 8.2 %, a saturated light intensity of 3.72 MW/cm2, and a non-saturated loss of 9.8 %. We introduced PtTe2-SA devices into Tm3+ doped solid-state laser for the first time, achieving passive mode-locking (PML) operations. In PML operation, a short pulse output of 670.8 ps was achieved. After being exposed to the air for 20 days, it can still produce good pulse output under the same experimental device. The results show that semi-metallic PtTe2 is expected to become a highly stable SA candidate material for pulsed solid-state lasers, which can be used to generate short pulse output in the 2 μm band, providing huge production power in many fields.

Mixed Electronic-Ionic Conductive Polymer Binder for Silicon-Based Solid-State Battery

Silicon has attracted extensive research attention in lithium-ion battery (LIB) field due to its high theoretical specific capacity (~3600 mAh/g) and cost-effectiveness. In recent years, silicon has emerged as a viable candidate for anode material for solid-state battery (SSB) technology. Similar to its application in LIBs, silicon utilizing in SSBs encounters challenges, such as significant volume variation (~300%) during cycling and poor cycling performance. In addition, the utilization of silicon in SSB faces another critical bottleneck in ionic conductivity due to the absence of liquid electrolyte. To address these challenges, various pioneering studies have explored potential solutions, including controlling the thickness of silicon anode to be below 150 nm,(1) fabricating electrodes with a combination of silicon and solid-state electrolyte (e.g, Garnet-type electrolyte(2) and sulfide electrolyte(3)), subjecting SSBs to a high pressure (10-50 MPa)(4).Here, we introduced an alternative approach to mitigate these challenges by designing anodes through incorporating silicon with mixed electronic-ionic conductive (MEIC) hierarchically ordered structure (HOS) polymer binders. These multifunctional HOS polymer binders effectively preserve the structural integrity of electrode materials, even when silicon materials experiences significant volume expansion and shrinkage during the charging-discharging process. Owing to establishments of covalent bonds between silicon surface and the polymer binders, the resulting SSBs exhibited excellent resilience and only required hand-tightening force (<1 ton) for operation. These polymer binders effectively maintained continuous electronic and ionic pathways within silicon-based anodes without the need of additional additives, such as carbon material and solid-state electrolytes. Utilizing these versatile polymer binders, the resultant SSBs featured an outstanding cycling performance over 100 cycles in full cells, with an average Coulombic efficiency exceeding 97%. Reference A. Song, W. Zhang, H. Guo, L. Dong, T. Jin, C. Shen and K. Xie, Advanced Energy Materials, 13, 2301464 (2023).W. Ping, C. Yang, Y. Bao, C. Wang, H. Xie, E. Hitz, J. Cheng, T. Li and L. Hu, Energy Storage Materials, 21, 246 (2019).M. Rana, Y. Rudel, P. Heuer, E. Schlautmann, C. Rosenbach, M. Y. Ali, H. Wiggers, A. Bielefeld and W. G. Zeier, ACS Energy Letters, 8, 3196 (2023).D. H. Tan, Y.-T. Chen, H. Yang, W. Bao, B. Sreenarayanan, J.-M. Doux, W. Li, B. Lu, S.-Y. Ham and B. Sayahpour, Science, 373, 1494 (2021).

Evaluation of Thermal Transport Characteristics of Three-Dimensional Self-Ordered Multilayered Silicon-Germanium Nanodots

1. Background and purpose Silicon-germanium (SiGe) alloys have much lower thermal conductivity than Si and Ge single crystals and are expected to be candidates for next-generation thermoelectric device materials of internet of things society. It is important to achieve both high carrier mobility and low thermal conductivity on the basis of the dimensionless figure of merit [1]. There are several studies on the thermoelectric properties of SiGe with low-dimensional structures such as superlattice and nanodots [2,3] to dramatically decrease thermal conductivity. However, the relationship between the nanoscale thermal properties and the phonon scattering mechanism of self-ordered multilayer SiGe nanodots with high uniformity grown by Stranski-Krastanov [4] mode is unclear. In this study, we demonstrated the thermal transport characteristics of the self-ordered multilayer SiGe nanodots. 2. Experiments Si/SiGe superlattice and nanodots samples were fabricated by reduced pressure chemical vapor deposition. We set to 20 cycles of Si0.65Ge0.35 / Si superlattice, the staggered Si0.65Ge0.35 nanodots (alternately stacked) and the dot-on-dot Si0.65Ge0.35 nanodots (vertically stacked) by changing growth temperature and precursors for Si spacer growth [4], as shown in Fig. 1. Thermal properties were evaluated by the Time Domain Thermoreflectance (TDTR) method. The strain states and Ge fraction were evaluated by Raman spectroscopy. The focal length and wavenumber resolution of the Raman spectrometer were 2,000 mm and 0.1 cm-1, respectively. The excitation light source was a green laser (wavelength: 532 nm). We obtained the Raman spectra of Si-Si, Si-Ge, and Ge-Ge vibrational modes derived from the SiGe regions. 3. Results and discussion Figure 2 shows the thermal conductivity for the SiGe region of the superlattice and nanodots (dot-on-dot and staggered structures) obtained by TDTR method. We found that the SiGe nanodots with the dot-on-dot structure have the highest thermal conductivity, while the SiGe nanodots with the staggered structure and SiGe superlattice have almost the same thermal conductivity. We consider that the heat flow easily penetrates from the top (surface) to the bottom (Si substrate interface) in the dot-on-dot structures. On the other hand, it is possible that the staggered SiGe nanodots can play a sufficient role as a phonon scatterer compared to the dot-on-dot structures since the superlattice structure and the staggered SiGe nanodots have almost the same thermal properties. In conclusion, we demonstrated the possibility of controlling phonon scattering by changing the arrangement of the self-ordered multilayer SiGe nanodots. Acknowledgement This work was supported by JSPS KAKENHI Grant Number 21K14201, Japan.

(Invited) Evolution of the Solid Electrolyte Interphase in Si Nanoparticle Based Li-Ion Battery Anodes: Insights from Ab Initio Simulations of Core-Level Spectroscopies

Silicon nanoparticles (c-Si NPs) are considered promising candidates for the active material in Si-based anodes, offering high gravimetric capacity and helping to mitigate volume expansion effects. However, the formation of an unstable Solid Electrolyte Interphase (SEI) around the nanoparticles leads to increased irreversible lithium consumption, resulting in reduced capacity and poor cycling stability. In this context, core-level spectroscopies are established techniques to assess the evolution and composition of the SEI. While X-ray spectroscopies provide valuable insights into atomic and electronic structures, interpreting them in complex systems could be challenging, highlighting the need of theoretical insights from ab-initio approaches. Our study focuses on the changes occurring in c-Si NPs and the SEI during the initial charge cycle, leveraging post-mortem core-level spectra at various states of charge (SOC). We employ a multi-edge analysis coupled with a fitting approach based on known experimental references and theoretical simulations. Additionally, we demonstrate how comparing experimental spectra with theoretical references allows tracking changes at the NP level, including amorphization and surface oxidation. Finally, we discuss some of the limitations of our theoretical description and propose addressing them through machine learning approaches. This work is supported by the European Union’s Horizon 2020 research and innovation program (BIG-MAP, Grant No. 957189, also part of the BATTERY 2030+ initiative, Grant No. 957213).

Synergy of Silicon-Graphene Anodes and Polymer-Ceramic Hybrid Separators for High Rate-Capable Lithium-Ion Batteries

With more and more electric vehicles (EV) hitting the market, the need for better and more robust energy storage system increases, and silicon has been a promising candidate for the next generation anode material to satisfy the high energy density and high-power requirements for electric vehicles because of its extremely high theoretical capacity. This has allowed the design of thinner electrodes to reduce the diffusion time scales and deliver a fast charge. However, at high charge and discharge rates, low electrical conductivity (~1.12 eV) of silicon hampers the battery performance. As a result, a lot of research has been conducted to improve the performance of silicon anodes using nanoscale carbon to increase the electrical conductivity. Graphene has been used to synthesize Si/Gr hybrid anodes due to its high conductivity.Graphene nanoribbons (GNRs) , a part of the graphene family, are one-dimensional graphene nanostructures which tune its electrical properties based on dimensional confinement. GNR has a higher conductivity than Graphene. It also has high aspect ratio and surface area to provide a strong conductive path along with mechanical strength to support the silicon anode. Due to presence of GNR, lithium-ion transport into silicon nanostructures was enhanced. As a result, 50% of graphene was replaced by 50% GNR with silicon nanoparticles to form anodes. Due to the highly conducting structure of GNR, capacity at high rates was significantly improved because of the improved silicon utilization. Since GNR’s dimensions are in nanometer range, connection with silicon nanoparticles is better. It not only improves silicon to silicon conductivity, but it also acts as a filler for better connection of graphene with silicon nanoparticles.Addition of graphene nanoribbons can improve the lithium-ion transport within the anode but to enhance the high charge transfer rate further, Si/GNR/Gr hybrid, high rate-capable anodes were paired with Polyimide (PI)/Polysilsesquioxane (PSSQ) hybrid separators which also shown to exhibit an improved charge transfer rate. At high rates such as 3C and 5C, the effect of separator on the cell performance becomes more prominent. While Celgard’s performance was very unstable at both 3C and 5C, at 3C, the cycling of hybrid separators did not get impacted, despite the relatively harsher conditions. This synergistic combination of high-rate capable silicon/graphene anode and hybrid separator outperformed the commercially used separator especially at high-rate cycling. Cells with Si/GNR/Gr anode paired with the PI/PSSQ separator delivered an impressive capacity of 1,000 mAh/g at high charge/discharge rates of 5C/5C.

Accelerating the Development of Oxygen Electrodes for Solid Oxide Cells Using Two-Stage Machine Learning

Reversible Solid Oxide Cells (RSOCs) stand out as highly efficient and cost-effective devices for energy storage and conversion. However, the pursuit of high-performance and durable RSOCs is impeded by the lack of efficient and stable oxygen electrodes. The conventional trial-and-error approach used for the development of oxygen electrodes is resources and time-consuming. In this presentation, we introduce a novel "two-stage machine learning" approach designed to expedite the discovery of optimal oxygen electrodes for efficient oxygen reduction/evolution reaction (ORR/OER) in SOCs. In the initial stage, we employed a high-throughput calculation approach to generate four ORR/OER related descriptors (energy above the convex hull, p-band center, d-band center, and vacancy formation energy) for a set of 4455 perovskite oxide candidates. Subsequently, we successfully predicted these descriptors using machine learning techniques based on the fundamental physico-chemical features of the candidates. Moving to the second stage, we measured the polarization resistances - directly related to ORR/OER activity - of 142 oxygen electrodes and employed them as prediction targets. Through our machine learning method, we accurately predicted experimental results based on the fundamental physico-chemical features of the candidate materials. Notably, among the 4455 candidates studied, a specific oxygen electrode material is predicted to exhibit both high activity and stability. When applied to an RSOC based on a proton-conducting electrolyte operated at 600 °C, a high peak power density of >1.5 W cm−2 is demonstrated in the fuel cell mode, and a high current density of >2.5 A cm−2 is achieved at a cell voltage of 1.3 V in the water electrolysis mode while maintaining stable operation for 500 hours.

Elucidating the Effect of Pre-Lithiation of Silicon Dominant Anodes on the Full Cell Performance

Over the last few years, there has been a high interest in increasing the energy density of lithium-ion batteries in order to increase the driving range of battery electric vehicles. On a material level, silicon is a promising anode active material candidate due to its high theoretical capacity of 3579 mAh g-1, which is approximately ten-fold higher than that of the currently used graphite anodes with a theoretical capacity of 372 mAh g-1.[1] However, the main drawbacks of silicon are its intrinsic volume expansion of +300 % upon lithiation.[2] This leads to rupturing of the passivating solid electrolyte interphase (SEI), particle cracking, and loss of electronic contact, limiting the lifetime of batteries with silicon based anodes, thus hindering their transition into application.As a possible solution, Jantke et al. proposed the concept of partial utilization of µm-sized crystalline silicon, where only one-third of the theoretical capacity is used for (de)lithiation. Thereby, a crystalline core remains, and the volume expansion on the particle-level is reduced to approximately + 100%.[3] In addition, it was shown that irreversible losses during the formation and upon cycling can be compensated by pre-lithiation of the anode, which increases the lifetime significantly.[4,5] In this study, we investigated a promising cell chemistry for high-energy applications, containing a Si-dominant anode and a cathode based on a Co-free lithium- and manganese-rich NMC. The here used anode consists of 70 wt% silicon, 20 wt% graphite, 2 wt% conductive C65, and 8 wt% LiPAA-binder. Note that graphite mainly acts as a conductive additive within the operating voltage window, with a negligible contribution to the overall anode capacity. The electrochemical testing was conducted at 25 °C in Swagelok® T-cells containing two glass fiber separators, a 1M LiPF6 in FEC:DEC (2:8, v:v) electrolyte and a lithium metal reference.Without pre-lithiation, these full-cells suffered from rapid capacity fading, reaching the 80 % state-of-health (SOH) criterion after ~100 cycles. As will be discussed, our analysis shows that the primary mode of failure in these cells is the loss of cyclable lithium, evidenced by an increase in the end-of-discharge potential at the anode. It was found that with increasing end-of-discharge potential at the anode, the anode resistance at low state-of-charge rises significantly.Therefore, silicon anodes were lithiated in coin half-cells to 25, 50, and 75 % of the reversible cathode capacity (corresponding to 300, 600, and 900 mAh gSi -1). Then, the anodes were harvested in the lithiated state and assembled in a Swagelok® T-cell with the same cathode, separator, and electrolyte as the non-pre-lithiated reference cells. Pre-lithiation leads to similar reversible charge/discharge capacities, but generates a cyclable lithium reservoir in the anode.Successively increasing the pre-lithiation of the anode increases the lifetime from 100 to 550 cycles. The onset of the above-described aging phenomena is delayed by 150 cycles for every additional 25 % pre-lithiation. Further, the influence of aging and lithium inventory on anode and cathode resistance will be discussed, showing that the increase in anode resistance is mainly a function of (de)lithiation rather than cycle number.Acknowledgments:The authors gratefully acknowledge the funding from the BMBF (Federal Ministry of Education and Research, Germany) in the ExZellTUM III project (grant number 03XP0255). We also kindly thank Wacker Chemie AG and BASF SE for providing the anode and cathode active materials.

Comparative Analysis of Single- and Poly-Crystalline Layered Cathode Materials: Determining the Superior Choice

In the field of cathode material candidates of lithium-ion batteries, there has been ongoing debate regarding which material is superior: poly-crystalline (PC) or single-crystalline (SC) cathode active materials. The PC materials are characterized by primary particles that agglomerate into secondary particles, which PCs are prone to micro-crack due to significant c-axis volumetric expansion/contraction in their lattice structure.As an alternative, the SC materials have been received attention for their physical resistance from the expansion/contraction and external pressure. However, in terms of lithium-diffusion pathway, it has been reported that SC’s structures possess certain disadvantages in lithium-ion diffusion compared to PC materials. This is attributed to the scarcity of grain boundaries and the extensive pathways of bigger primary particles in SC, which impede the efficient movement of lithium ions. Even though the comparative analysis has been needed between PC and SC above superiority, achieving an exact comparison under identical or similar conditions is challenging due to differences in particle size and surface environment, including binders and conducting materials.In this study, we standardized the size of both PC and SC particles to 10 μm to evaluate their electrochemical performance under identical environmental conditions and using a common commercial electrode composition (96:2:2, active material, carbon black, and PVDF binder) in a wet process with a 60% nickel cathode (NCM622). Consequently, in comparing PC and SC materials, the focus has been on analyzing key factors that contribute to electrode performance, specifically concerning issues of lithium-ion diffusion and the composition of materials at the electrode level that may arise. Moreover, we fabricated SC electrodes using a solvent-free dry electrode process as an alternative of better process, aimed at creating higher energy density electrodes without the addition of carbon black, but rather by employing coated carbon nanotubes (CNT) on the SC surface with the composition (99.6:0:0.4, active material, carbon black, PTFE binder) to clarify the comparison between two main cathodes’ design.Finally, we found that the dry-processed SC electrode demonstrated superior performance in full-cell tests and show excellent cycle performance at high temperature (45 °C) and high voltage (2.8 to 4.5V). The enhanced performance observed in dry-processed electrodes using CNT was found to be primarily due to the reduced ion resistance in environments devoid of internal carbon black, as confirmed through comparison with wet-processed electrodes. Although electron conductivity was ensured through the conductive material, a significant decrease in performance was noted if the environment was not conducive to the movement of internal lithium-ion. And it is attributable to enhanced surface stability under high-voltage storage conditions with a reduced specific surface area compared to PC cathode and PC wet process condition. Figure 1

Bending Effects on Polyvinyl Alcohol Thin Film for Flexible Wearable Antenna Substrate

Polyvinyl Alcohol (PVA) has been used in various applications, including the medical health industry and electronics. It is a synthetic polymer with advantages such as being transparent, flexible, biocompatible, biodegradable, and a simpler synthesis process. These advantages make PVA a very promising material for human wearable antennae. In this research, the bending effect of an antenna using a PVA substrate is studied to analyze its durability in the wearable application. Firstly, the thin film substrate synthesis is performed using PVA 2488 with the measured average dielectric constant and tangent loss of 1.24 and 0.066, respectively, across S-Band frequency. Later, a 5G antenna is designed and fabricated using the PVA substrate. Finally, the bending effects of the fabricated antenna are measured at different bending radii. Four different antenna-bending radii are selected to represent different curvatures of human body parts. Results show that bending does not have a significant effect on the reflection coefficient of the antenna, where the frequency shifts from 2.2% up to 7.4% only for all bending conditions. Hence, in that aspect of finding, the PVA thin film is a potential candidate for flexible and wearable antenna material in various human body parts in biomedical applications.

Monitoring the evolution of optical coatings during thermal annealing with real-time, in situ spectroscopic ellipsometry

Abstract Thermal annealing plays a key role in optimizing the properties of amorphous optical coatings. In the field of gravitational wave detection (GWD), however, the effects of annealing protocols on the interferometry mirror coatings have been explored primarily by ex post analysis. As a result, the dynamics of the coatings properties during annealing is still poorly known, potentially leading to suboptimal performance. Here, using real-time, in situ spectroscopic ellipsometry (SE) we have tracked the refractive index and thickness of a titania-tantala coating during controlled annealing. We have tested the material and the annealing protocol used in&amp;#xD;current GWD mirrors. The annealing cycle consisted of a heating ramp from room temperature to 500 °C, followed by a 10-hour plateau at the same temperature and the final cooling ramp. SE measurements have been run continuously during the entire cycle. Significant variations in the thickness and refractive index, which accompany the coating structural relaxation, have been recorded during the heating ramp. These variations start around 200 °C, slightly above the deposition temperature, and show an increased rate in the range 250-350 °C. A smaller, continuous evolution has been observed during the 10-hour high-temperature plateau. The results offer&amp;#xD;suggestions to modify the current annealing protocol for titania-tantala coatings, for example by increasing the time duration of the high-temperature plateau. They also suggest an increase in the substrate temperature at deposition. The approach presented here paves the way for systematic, real-time investigations to clarify how the annealing parameters shape the properties of optical coatings, and can be leveraged to define and optimize the annealing protocol of new candidate materials for GWD mirrors.

Design and development of titanium-coated implants with advanced antioxidant properties for enhanced regenerative repair of diabetic bone

The aging population is closely associated with chronic metabolic diseases, including diabetes, hypertension, and other metabolic disorders. Metabolic dysfunction is a primary characteristic of diabetic patients, which can impair cellular response to insulin and lead to increased production of reactive oxygen species (ROS), hindering bone healing. Therefore, the development of multifunctional titanium (Ti) implants with the ability to eliminate reactive oxygen and promote bone formation is the optimal strategy to address this issue. In this study, we designed a thioctic acid(Ta) coating loaded with strontium(Sr), forming a strong bond with the Ti implant (Ti-Ta@Sr). During treatment, sulfuric acid demonstrated the ability to release monomers in the early stages, effectively eliminating excess reactive oxygen produced in high-glucose environments and regulating the diabetic microenvironment. The delayed in-situ release of strontium ions also enhanced osteogenic differentiation efficiency. Both in vivo and in vitro experiments confirmed that Ti-Ta@Sr significantly restored the osteogenic capacity and proliferation of osteoblasts under high-glucose conditions. These advantages make Ti-Ta@Sr a promising candidate material for orthopedic implants, suitable for repairing bone defects in diabetic patients.