Spacer Layer Research Articles

Effect of Sulfur Modification on Structural and Electrochemical Performance of Pitch-Based Carbon Materials for Lithium/Sodium Ion Batteries.

Coal tar pitch (CTP) has become an ideal choice in the preparation of anode precursors for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of its abundant carbon content, competitive pricing and adjustable structure properties. In this paper, sulfurized pitch-based carbon (SPC-800) was obtained by allowing CTP to react with sulfur at 350 °C and subsequently achieve carbonization at 800 °C. SPC-800 was more disordered and had a larger layer spacing than carbonized CTP (PC-800). Upon utilization as an anode for LIBs, SPC-800 possessed a higher reversible specific capacity (478.1 mAh g-1 at 0.1 A g-1), while utilization in SIBs displayed a capacity of 220.9 mAh g-1 at 20 mA g-1. This work is an important guide to the design of high-performance anodes suitable for use with both LIBs and SIBs.

Comparison of Color Changes in Paints Based on Ultramarine and Zinc White Resulting from Storage and Thermally Induced Aging

ABSTRACT The paper presents the results of measurements of the L*, a*, and b* color coordinates in the CIEL*a*b*76 (D65/10) space of paint layers of zinc white and ultramarine with several primers and binders. The coordinates are measured for naturally aged reference samples and test samples that underwent two thermal shocks. The color differences of samples obtained using three binders and three primers are quantitatively characterized. It is shown that thermally induced changes in the L* coordinate, as distinct from the a* and b* coordinates, are significantly greater than the changes predicted by the artificial aging protocol. However, during subsequent storage, L* partially relaxes to its original values, and the resulting changes in this coordinate can be considered insignificant. The relaxation effect is also characteristic of the a* and b* coordinates for most samples. Specific results are obtained for paint layers with resin-containing binder on glue–chalk primers. When zinc white is used, such samples have greater L* coordinate and smaller b* coordinate, i.e. appear to be lighter and less yellow in comparison with the remaining samples. When ultramarine is used as a pigment, the resin-containing binder and glue–chalk primers provide the maximum depth of blue color (minimum b* value), which remains almost unchanged with aging. However, the crimson hue characteristic of such samples (greater value of the a* coordinate) is intensified due to heating. The results show that two thermal effects on paint layers separated in time can lead to opposite changes in color coordinates.

Revealing the sodium storage mechanism of cellulose separator-derived hard carbon anode materials for sodium-ion batteries

Hard carbon (HC) shows significant promise as a material for sodium-ion batteries (SIB). Cellulose-derived carbon is considered one of the most promising high-performance anode materials for sodium-ion batteries. In this study, waste cellulose separator-derived HC anode materials were rationally developed using the pre-oxidation-carbonization pyrolysis method. The as-prepared HC possessed advantageous characteristics for Na+ storage, including a unique fibrous structure, a reasonable space layer, and a small specific surface area (SSA). The optimal sample demonstrated a substantial reversible capacity of 361.29 mAh/g at 0.1C, an impressive high-rate performance with a reversible capacity of 272.93 mAh/g at 10C, and an initial coulombic efficiency of 84.85 %. Following 500 cycles at 1C, the capacity retained 96.38 % of its initial value. The sodium storage process was identified as the “adsorption-insertion-pore filling mechanism” through ex-situ XRD and in-situ Raman experiments. Moreover, the as-prepared HCs demonstrated better rate and cycle capability when evaluated as anodes in full-cell sodium-ion batteries (SIBs). This research provides valuable insights into the rational design of high-performance HC anodes for SIBs and other applications.

Flexible room temperature gas sensor based on α-Fe2O3/Ti3C2Tx MXene composites for ppb-level H2S detection

Ti3C2Tx MXene have attracted enormous attention in portable, wearable electronics areas due to its excellent flexible, electrical conductivity and outstanding physical and chemical properties. Here, 2D α-Fe2O3/Ti3C2Tx MXene composites were synthesized by in-suit growth of α-Fe2O3 on the surface of Ti3C2Tx MXene and between the layers of Ti3C2Tx MXene by solvothermal and annealing methods. Compared with pure α-Fe2O3, the optimal α-Fe2O3/Ti3C2Tx MXene composites exhibited excellent gas sensitive performance (100 ppm can reach 20.27) and a theoretical ultra-low limit-of-detection of 10.19 ppb to H2S gas at room temperature (25 ○C). The combination of α-Fe2O3 and Ti3C2Tx lead to the layer spacing of Ti3C2Tx MXene are further enlarged which is more favorable for H2S gas adsorption. And the excellent performance is maintained even under bending conditions. This work provides a new idea for MOS/Ti3C2Tx MXene in the field of flexible room temperature sensors.

Improvement of digital, analog/RF and linearity performances of charge plasma based junctionless FinFET through spacer layer engineering

We investigate the digital, analog/RF, and linearity performance of four CP FinFETs distinguished by spacer layers: (i) single low-k spacer on both sides of the gate (D1), (ii) single high-k spacer on both sides of the gate (D2), (iii) a combination of high-k spacer and air on the source side and high-k spacer on the drain side (D3), and (iv) a combination of high-k spacer and air symmetrically placed on both sides of the gate (D4) at 10 nm technology node. Our results highlight the superior digital performance of the D4 device, demonstrating significant enhancements in various analog/RF figures of merit (FOMs) including transconductance, transconductance efficiency, unity gain cut-off frequency (FT), and gain bandwidth product (GBP). Notably, the D4 device exhibits a remarkable 256 % improvement in FT and a substantial 456.13 % enhancement in GBP compared to D1. Additionally, we analyze linearity and intermodulation distortion performance, suggesting the D4 device as the optimal architecture for high-performance digital and analog/RF applications.

Influence of the counterion on the structure and stability of the smectic C phase in ionic liquid crystals

ABSTRACT Ionic liquid crystals (ILCs) are built of ion pairs. These consist often of a small anion and a large mesogenic cation. The properties of the ILCs like e.g. the phase behaviour or structure parameters, depend not only on the large mesogenic cations but also on the small counteranions. Here the influence of the small anion on the formation and stability of the in ILCs rare smectic C (SmC) phase is investigated in a series of methylimidazolium azobenzene ILCs with the same cation but different anions. All ILCs synthesised show the rare SmC phase. The phase behaviour and the tilt angles of the compounds were studied using polarising optical microscopy and differential scanning calorimetry. Furthermore, layer spacing and layer shrinkage of the SmC phase were examined using X-ray scattering. We show that the structural parameters of the phase-like layer spacing and tilt angle are only weakly influenced by the anions, whereas the mesophase ranges are strongly influenced by the choice of the anions. The results are also compared to the Hofmeister series for anions and it is found that the anions stabilise the SmC phase more the more kosmotropic they are.

Impact of groove-and-tongue parameters on the bonding behavior between 3d-printed UHP-SHCC and cast normal concrete

The utilization of 3D-printed formworks represents a significant advancement in traditional construction practices, offering the potential to enhance structural capacity and effectively address reinforcement challenges in 3D concrete printing. Ensuring strong bonding between formwork and cast concrete is critical for structural integrity. In this study, 11 composite specimens with varying groove-and-tongue parameters including the layer number, spacing, length, and thickness of tongues undergo splitting tests. Results reveal that increasing the tongue’s layer number enhances the interfacial splitting tensile strength, whereas tongue spacing has minimal impact on interfacial strength, and a thicker tongue negatively affects the interfacial splitting tensile strength. An optimized groove-and-tongue configuration can significantly increase the interfacial splitting tensile strength from 2.10 MPa to 3.66 MPa, with a maximum increase rate of 70.4% and achieving a higher value (20.8%) than that of fully cast normal concrete. A splitting tensile strength model is proposed, with predictions aligning well with experimental results.

Exploration microstructural evolution and wear mechanisms of wire arc additive manufacturing NiTi/Nb bionic composite materials

NiTi/Nb layered heterogeneous structure (LHS) materials with different layer spacings were designed and fabricated using composite wire arc additive manufacturing. The NiTi/Nb LHS samples consisted of NiTi phase and β-Nb phase, and no other intermetallic compounds were formed. The NiTi layer in the NiTi/Nb LHS sample changes from a homogeneous eutectic microstructure to a gradient heterogeneous eutectic microstructure as the layer thickness increases. The Nb layer grains are much smaller than the NiTi layer grains, and no obvious texture is formed in the NiTi/Nb LHS samples. NiTi/Nb LHS samples still have a certain recoverable strain at room temperature, with a maximum recoverable strain of 4.36 % after 10 cycles of 10 % strain compression. The wear rate of the NiTi layer of the NiTi/Nb LHS samples was lower than that of the Nb layer. The main wear mechanisms on the Nb surface are abrasive wear, adhesive and oxidative wear while the main wear mechanism on the NiTi surface is adhesive wear. When the layer thickness ratio of NiTi layer to Nb layer is 2:1, the NiTi/Nb LHS samples form a gradient heterogeneous eutectic structure in the NiTi region, which in turn enhances the wear resistance of the LHS samples. In this study, cross-scale NiTi alloy and Nb heterogeneous components were constructed by wire arc additive manufacturing, which showed good wear resistance. The design provides a new solution for integrated additive manufacturing repair of heterogeneous metals in engineering applications.

Research progress of functional MXene in inhibiting lithium/zinc metal battery dendrites.

The layered two-dimensional (2D) MXene has great promise for applications in supercapacitors, batteries, and electrocatalysis due to its large layer spacing, excellent electrical conductivity, good chemical stability, good hydrophilicity, and adjustable layer spacing. Since its discovery in 2011, MXene has been widely used to inhibit the growth of anode dendrites of lithium metal. In the past two years, researchers have used MXene and MXene based materials in the anodes of zinc metal batteries and zinc ion hybrid capacitors, respectively, and made a series of important progressive steps in the inhibition of zinc dendrite growth. In this review, we summarize the research progress of functional MXenes in inhibiting the growth of lithium and zinc metal anode dendrites, and provide a brief overview and outlook on the current challenges of MXene materials, which will help researchers to further understand the methods and their mechanisms, thus to develop novel electrochemical energy storage systems to meet the needs of rapidly developing electric vehicles and wearable/portable electronics.

High-Yield Exfoliation of Stanene Nanodots for High-Performance Organic Light-Emitting Diodes.

Stanene nanodots (SnNDs) derived from layered tin have attracted considerable interest due to their conveniently tunable bandgap and topological superconductivity. However, high-yield exfoliation of ultrathin SnNDs is still a challenge due to the short layer spacing and strong binding energy. In this work, atomically thin SnNDs with a uniform size of 2.3 nm are successfully prepared by utilizing imidazolium ionic liquid-assisted exfoliation. The obtained SnNDs possess a wide bandgap of 2.69 eV, along with notable solvent compatibility (well dispersed in both polar and nonpolar solvents) and excellent stability. Furthermore, we construct Ir(ppy)3-based green OLED with hybridizing SnNDs and graphene oxide (GO) as the hole injection layer (HIL). It proves that the application of SnNDs helps to modulate the work function and passivate surface defects of GO, increasing hole mobility and thereby improving the device performance. Compared to the PEDOT:PSS-based control device, the optimized SnNDs-GO-based OLED demonstrates an improvement of 6.56, 41.06, and 8.16% in current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE), respectively. This work not only introduces a new approach to preparing 2D SnNDs but also creates a novel HIL material for OLED devices.

Controllable synthesis of NiCoMo-LDH with nanofloral structure assisted by monodisperse spherical silica for asymmetric supercapacitor

Traditional layered double hydroxides (LDH) have disadvantages such as small layer spacing, insufficient active sites and poor electrical conductivity, which seriously restricts their future utilization in the realm of energy storage. In this paper, a controlled synthesis strategy of tercomponent metal NiCoMo-LDH is proposed by using the structural advantages of metal-organic skeleton (MOF) templates, combining structural regulation and atom doping. On the basis of the synthesis of Ni-MOF 74, Co and Mo atoms are introduced for a small amount of doping, and the monodisperse spherical SiO2 is inserted to adjust the pore structure of NiCoMo-MOF, expand the lamellar spacing, and effectively avoid the accumulation and agglomeration of lamella. Finally, NiCoMo-LDH cathode material with loose porous and coarsely curled nanosphere structure was synthesized through the chemical reaction of OH− with SiO2 and the destruction of the skeleton structure of MOF. The specific capacitance of the material is 1423.3 F·g−1 at 0.5 A·g−1, and after 5000 cycles of charging and discharging, 80.0% of the original specific capacitance is sustained. Moreover, NiCoMo-LDH//AC ASC possesses a high energy density of 39.1 Wh·kg−1 at the power density 400 W·kg−1. Combined with density functional theory (DFT) calculation, the fact that metal doping can not only effectively improve the conductivity of electrode materials has been further proved, but also accelerate the electron/ion migration rate, which successfully reveal the synergistic enhancement mechanism of electrochemical properties of materials.

Liquid template synergizing combustion activation to construct vesicular porous carbon anode for sodium ion batteries

In this study, B, N and O tri-doped porous carbon material (EBNK) is successfully prepared by liquid template synergistic combustion activation. Benefiting from this method, the generated EBNK exhibits a unique vesicle-like spherical shell structure, which significantly accelerates the transport of sodium ions, and therefore the initial coulombic efficiency of its half-cells in ether-based electrolyte is as high as 95.6 %. Moreover, the synergistic effect of the three dopant atoms increases the number of defects and the spacing of the carbon layers, resulting in the EBNK anode exhibiting rare and excellent properties. The specific capacity is 487.5 mAh/g at 0.05 A/g, and 125 mAh/g at 50 A/g; the capacity is maintained at 138.9 mAh/g after 5500 cycles at 20 A/g. The NVP//EBNK full cell has an energy density of 192.2 Wh kg−1 at a power density of 159.7 W kg−1. This study will undoubtedly expand the methods for preparing sodium-ion batteries with excellent performance, provide new perspectives on the energy storage mechanism of multi-doped porous carbon, and promote the development of the energy storage field.

Long-Life Na3V2(PO4)3||Graphite Energy Storage Device Enabled via Regulating the Area Density of Anode

Abstract The regular graphite can only provide the negligible capacity for Na-ion intercalation, due to the narrow layer spacing and unstable thermodynamic factor. In this study, an energy storage device is created using the prelithiated graphite and Na3V2(PO4)3&NaClO4-based electrolyte, achieving an initial energy density of 317 W h kg−1 and a long lifespan of 1000 cycles with a 71.3% energy retention under the current rate of 1 C. Additionally, the prelithiated graphite anode could be recognized as an artificial Li metal with a strong skeleton, which reduces the volume changes and provides the growth substrate for Na-ion storage by the plating/stripping behavior. When the Li is depleted by participating in the reconstruction of SEI and the occurrence of complex side reactions, the battery system would die as a result. Therefore, the amounts of excess Li have a significant impact on the electrochemical performance of this device. That is to say that regulating the area density of anode enables a long-life Na3V2(PO4)3||graphite energy storage device.

WO3 coating improves the cyclic stability of LiNi0.9Co0.05Mn0.05 as cathode materials for lithium-ion batteries

In this paper, WO3 uniformly coated LiNi0.9Co0.05Mn0.05O2 cathode materials are prepared by wet coating method using ammonium metatungstate as tungsten source. The XRD, SEM, and XPS tests show that the cladding process introduced W ions into the NCM lattice, increasing the layer spacing and improving the lithium diffusion rate. The charge/discharge test results indicate that a moderate amount of WO3 coating can enhance the rate-discharge performance and increase the long cycle life. After 100 cycles at 1C (180 mAh g−1), the reversible capacity of the material containing 0.5wt% WO3 coating is 157.9 mAh g−1, while that of the original material is only 130.9 mAh g−1, which indicates that the WO3 coating protects the cathode material from HF corrosion, thus improving the stability of the structure. DFT calculations show that the dangling bonds of O on the NCM surface are highly susceptible to binding with W, which reduces the possibility of WO3 coating exfoliation.WO3 and NCM are p-type semiconductors and semi-metallic materials, respectively, which form ohmic contacts at heterogeneous interfaces thereby increasing the electronic conductivity of the materials, and due to the synergistic effect, the diffusion barrier of Li near the heterogeneous interfaces is lower than that of the pristine materials.

Magnetization dynamics in single and trilayer nanowires

We have studied the magnetization dynamics of single Py(t) (t= 20 nm, 50 nm) and trilayer [Py(50)/Pd(tPd)/Py(20)] nanowire arrays fabricated over large areas using deep ultraviolet lithography technique. The dynamic properties are sensitive to the field orientation and magnetic film thicknesses. A single resonant mode corresponding to the excitations at the bulk part of the wire is detected in all the single-layer nanowire arrays. Furthermore, the spacer layer thickness influenced the dynamic properties in trilayer samples due to the different coupling mechanisms. A single resonant mode is observed intPd= 2 nm trilayer nanowires with a sharp frequency jump from 13 GHz to 15 GHz across the reversal regime. This indicates the exchange coupling and the coherence in magnetization precession in the ferromagnetic layers. On the other hand, wires with 10 nm-spacer display two well-resolved modes separated by ∼3 GHz with a gradual change in frequency across the reversal regime from-26mT to-46mT, indicating the presence of long-range dipolar interactions instead of exchange coupling. The spacer layer of the proposed spin-valve-type structure can be tailored for desired microwave splitters or combiners.

Rigid-flexible coupling multistage carbon composite materials based on hybrid crosslinking as anodes for ultra long-cycling lithium-ion batteries

Graphene have garnered considerable attention owing to their disordered structure, wide layer spacing, and cost-effectiveness. The hierarchical porous structure of porous reduced graphene oxide (rGO) nanosheets with hollow carbon nanospheres offers advantages such as an intact conductive network and a robust structure. However, since the hollow carbon nanospheres are physically in contact with rGO, they are randomly dispersed on the graphene surface, severely impeding fast electron transport and resulting in poor electrochemical performance. In this study, we introduced a third layer of a polypyrrole (PPy) -derived carbon film on the basis of porous rGO sheets and hollow carbon nanospheres. The HCGP-200 anode was successfully prepared to effectively encapsulate hollow carbon nanospheres on rGO sheets through the synergistic effect of rGO and the PPy-derived carbon film. The HCGP-200 anode exhibits robust cycling performance (780 mAh g−1 after 2200 cycles at 5 A g−1) and excellent rate capacity. Additionally, it demonstrates outstanding cycling stability and remarkable capacity retention (450 mAh g−1 after 3000 cycles) even at ultra-high current densities of 20 A g−1. The ingenious design and preparation of HCGP-200 is of great significance in guiding the application of high-power appliances.

Facilitating sulfur species capture and bi-directional redox in Li-S batteries with single-atomic Co-O2N2 coordination structure

Lithium-sulfur (Li-S) batteries suffer from the shuttle effect of soluble lithium polysulfides (LiPSs) and slow redox kinetics, significantly limiting their practical application. Although single-atom catalysts (SACs) offer a promising strategy to address these challenges, designing materials with optimal adsorption force and high catalytic activity remains a grand challenge. Here, we present a cobalt (Co)-based SAC with unique Co-O2N2 coordination structures for Li-S batteries. Both experimental and theoretical studies demonstrate that O, N-coordinated Co single atoms anchored on a porous carbon framework (Co/NOC) effectively capture LiPSs and dramatically catalyze bidirectional polysulfide conversion. The expanded carbon layer spacing facilitates lithium ions diffusion and maximizes the exposure of active sites. As a result, Li-S batteries incorporating Co/NOC as separators exhibit outstanding rate performance (906.6 mAh g−1 at 3 C) and exceptional cycling stability, even at −10 °C. Furthermore, with a high sulfur loading of 12.0 mg cm−2, the areal specific capacity reaches up to 12.36 mAh cm−2. This work provides some useful insights for the design of high-performance SACs for Li-S batteries.

Balancing Graphitic Nanodomains and Heteroatom Doping in Hard Carbons Toward High Capacity and Durable Potassium‐Ion Battery Anodes

AbstractHard carbons (HCs) have emerged as promising candidates for commercial anodes in potassium‐ion batteries (PIBs). However, a thorny challenge remains in achieving high reversible capacities at high charge/discharge rates, which significantly hinders the development of HCs for PIBs. Here, a temperature‐controlled strategy is proposed to effectively balance graphitic nanodomains and heteroatom doping content in HCs, resulting in widened carbon layer spacing, high conductivity, and abundant K‐ion intercalation sites. The optimized NO‐HC600 electrode exhibits a high reversible capacity of 315.0 mAh g−1 at 0.2 A g−1, and exceptional cyclic stability (235.0 mAh g−1 after 1200 cycles at 2.0 A g−1 with a capacity retention rate of 98.82%). Furthermore, systematic in /ex situ experiments unveil a highly reversible “adsorption–intercalation” mechanism governing potassium‐ion storage, confirming the origin of the superior performance. This work offers valuable insights into the facile preparation of HC anodes with high reversible capacity and fast charge/discharge capability for PIBs.

Zr-doped O3-type NaNi1/3Fe1/3Mn1/3O2 cathodes with enhanced structure stability for sodium-ion batteries

O3-type NaTMO2 (TM = transition metal) is highly anticipated as a cathode for sodium-ion batteries due to its high theoretical specific capacity and low cost. However, the irreversible phase transition during sodiation/desodiation and the Jahn-Teller effect induced by Mn3+ have hindered its steps towards industrialization. Herein, we propose a doping strategy to enhance the structural stability of O3-type NaNi1/3Fe1/3Mn1/3O2 through Zr doping. On the one hand, the Na+ transport channels are broadened due to the enlarged layer spacing, which accelerates the kinetic processes. On the other hand, Zr doping maintains structural integrity, inhibiting the decay of the layered structure. As a result, the uniquely designed material NNFMZO-6000 exhibited a discharge specific capacity of 113.8 mAh g−1 at 1 C and a capacity retention of 67.54 % after 200 cycles. This work presents an effective modification method to optimize the properties of O3-type NaTMO2 materials.

Ultrahigh nitrogen-doped carbon derived from g-C3N4 assisted by citric acid for superior potassium-ion storage

Nitrogen-doped carbon is regarded as a promising anode for potassium ion batteries (PIBs) because nitrogen atoms can regulate the structures of carbon and generate abundant active sites. How to improve the nitrogen content in carbon through simple and effective methods remains to be further addressed. In this paper, a carbon material (60NC) with ultrahigh nitrogen content (16 %) was prepared from graphite phase carbon nitride (g-C3N4) by a convenient freeze-drying and high-temperature pyrolysis method, assisted by citric acid. When used as an anode for PIBs, 60NC exhibited a superior reversible capacity of 318.1 mAh g−1 after 200 cycles at 0.1 A g−1. Even at the high current density of 1A g−1, 60NC maintained a specific capacity of 261.8 mAh g−1 after 1000 cycles. The excellent electrochemical performance of 60NC mainly stems from its abundant K+ storage active sites caused by nitrogen doping, large layer spacing, and hierarchical porous structure.