Large Interplanar Spacing Research Articles

Exploring the molarity of Lithium Fluoride in minimally intensive layer delamination (MILD) method for efficient room temperature synthesis of high quality Ti3C2Tx free-standing film

In recent years, MXene has become the most demanding material in the 2D family, leading to their increased use in research for a diverse range of applications, such as energy storage, water purification, optoelectronics, electromagnetic interference (EMI) shielding and medicine. However, recent research has made it increasingly important to synthesize high-quality MXene in a safe, reliable, fast, reproducible, and good-yielding single-step method. To achieve high-quality MXene by etching the MAX phase precursors, it is very important to critically optimize synthesis parameters, such as etching method, etchant concentrations, temperature, time, etc. Minimally intensive layer delamination (MILD) method for MXene synthesis using Lithium Fluoride (LiF) salt and hydrochloric (HCl) acid seems to be a better choice in the context of improved performance in different applications as well as its scalability and reproducibility. Here, the molar ratio of HCL/LIF is critical for Aluminium etching at room temperature to produce a high-quality MXene with = O, -OH, -F termination groups in the MILD method. However, in case of MILD method the effect of LiF/HCL concentrations on quality of MXene need to be addressed. In this study, we focus on room temperature etching of Ti3AlC2 using MILD method to synthesize quasi two-dimensional carbide (Ti3C2) MXene. The influence of molarity concentration of etchants (LiF and HCl) on quality of MXene has been thoroughly investigated. Different molar concentrations of Lithium Fluoride (LiF) with fixed HCL concentration were tested at room temperature for 24 h in the etching process. The crystal structure, microstructure and composition of the MXene were characterized using X-ray diffraction, Raman spectroscopy, and electron microscopy. Flexible free-standing MXene film with largest shift in the characteristic (002) peak, indicating large interplanar spacing, has been successfully achieved repeatedly for an optimum molar concentration of etchants at room temperature.

Boosting the Capacitor Performance of the Metal Organic Frameworks Derived V2O5 Nanoflower by Cu Doping.

Due to its ultrahigh theoretical capacitance, vanadium pentoxide (V2O5) is considered to be a valid candidate for advanced supercapacitors. However, because of the low electron/electrolyte transfer rate, the capacitive performance still remains to be improved. In this report, Cu doping is adopted to improve the capacitive performance by a two-steps strategy consisting of microwave-assisted solvothermal and postannealing treatments. The electrochemical results indicate that the Cu doping was beneficial for improving the specific capacitance, extending the potential window, and improving the rate ability and long-term stability of V2O5. Furthermore, the mechanism for the performance improvement is explained in detail by combining theoretical calculation and experiments. The results indicated that, compared with that of undoped V2O5, the larger interplanar spacing, better electrical conductivity, a larger proportion of V3+/V4+, and more abundant oxygen vacancies result in an improved capacitive performance. Our proposed Cu-doped V2O5 (Cu-V2O5) can be used as both a positive electrode and a negative electrode for the assembly of the symmetric supercapacitor, which can be used as an energy storage device for light emitting diode lamps.

Exploration of the lithiation/de-lithiation mechanisms of MoSe2@rGO composite anode by operando X-ray absorption spectroscopy

Owing to their inherent advantages of large inter-planar spacing and high-rate capability transition metal di-chalcogenides have attracted much attention as active materials for lithium-ion batteries (LIBs). Herein, MoSe2 and hybrid MoSe2@rGO nanocomposites have been successfully synthesized via hydrothermal processes and have been employed as anodes in LIBs. LIBs with bare MoSe2 and MoSe2@rGO anodes yield initial discharge capacities of 825 mAhg−1 and 979 mAhg−1 respectively at the current density of 100 mAg−1 and 619 mAhg−1 and 850 mAhg−1 respectively at the high current density of 500 mAg−1 in a voltage range of 0.1–3 V respectively. Thus, LIBs with MoSe2@rGO anode showed enhanced electrochemical performance compared to that with bare MoSe2 anode. Further, LIB with MoSe2@rGO anode during the 1st discharge/charge cycle has been investigated by operando X-ray Absorption Spectroscopy (XAS) measurements using synchrotron radiation which provides a detail insight into the intercalation/conversion processes that take place during lithiation/de-lithiation. The operando measurements reveal formation of LixMoSe2 in the initial phase of Li intercalation (discharge process) followed by conversion of LixMoSe2 into Mo, Li2Se and Se. The Li de-intercalation (charging process) shows oxidation of Mo to MoSe2, though the process is found to be not fully reversible and residual unreacted Mo and Se may lead to capacity fading of the LIBs during long cycling. Thus in the present work, the distinctive lithium reaction pathway in LIBs with MoSe2@rGO anodes has been deciphered by synchrotron radiation based operando XAS study.

Boosted Charge-Transfer behavior for ultrafast Zn storage by constructing intrinsic heterojunction of ammonium vanadate nanoribbons coupling with interlaminar MXenes nanosheets

Ammonium vanadate (NH4V4O10, NHVO) is one of the most promising cathode materials for aqueous zinc-ion batteries (ZIBs) owing to its inherent large interplanar spacing, highly reversible electrochemical reaction mechanism and admirable specific capacity. However, the fragile interlayer structure and sluggish electron transport behavior generally cause tardy electrochemical reaction kinetics and result in poor cycling stability and rate capabilities. In this work, a novel intrinsic heterojunction cathode (NHVO@MX) of NHVO nanoribbons coupling with inserted Mxenes (MX) nanosheets is rationally constructed on a flexible carbon cloth substrate for wearable ZIB applications. The intercalated MX nanosheets not only serve as the spacer to isolate the NHVO interlayers as well as efficiently accelerate electron and ion transport behaviors, hence preserving the numerous exposed active areas required for rich and rapid Zn storage. Most impressively, it presents the lowest charge-transfer barrier among all the reported vanadate-based materials induced by the interlaminar MX nanosheets, demonstrated by both experimental measurement and theoretical calculation. As a result, the as-prepared heterojunction cathode delivers high specific capacity of 437 mAh·g−1, excellent rate capability and ultralong cycling life (over 2000 cycles). Therefore, manufacturing the heterojunction laminar cathode with incorporated MX can be considered a prospective strategy for next-generation advanced ZIBs.

Modulating the p-band center of carbon nanofibers derived from Co spin state as anode for high-power sodium storage

Carbon nanofibers (CNFs) have received extensive and in-depth studied as anodes for sodium-ion batteries (SIBs), and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level. Herein, CNFs anchored with cobalt nanocluster (CNFs-Co) were prepared using chemical vapor deposition and thermal reduction methods. The as-prepared CNFs-Co shows a high initial Coulombic efficiency of 91% and a high specific discharge capacity of 246 mAh/g at 0.1 A/g after 200 cycles as anode for SIBs. Meanwhile, the CNFs-Co anode still delivers a high cycling stability with 108 mAh/g after 1000 cycles at 10 A/g. These excellent electrochemical properties could be attributed to the involved spin state Co, which endows CNFs with large interplanar spacing (0.39 nm) and abundant vacancy defects. Importantly, the spin state Co downshifts the p-band center of carbon and strengthens the Na+ adsorption energy from −2.33 eV to −2.64 eV based on density functional theory calculation. This novel strategy of modulating the carbon electronic structure by the spin state of magnetic metals provides a reference for the development of high-performance carbon-based anode materials.

The preparation of rod-like porous α-Fe2O3 with large interplanar spacing for symmetric supercapacitors

Rod-like porous α-Fe2O3 was synthesized by static hydrothermal treatment at 160°C and used as a symmetric supercapacitor. The phase information, structure, morphology, valence state and composition of the prepared sample were characterized using X-ray diffraction, infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N2 adsorption–desorption. The results show that the prepared α-Fe2O3 is a rod-like porous material dominated by mesopores. Moreover, the α-Fe2O3 is a hexagonal single crystal with [FeO6] octahedrons and the interplanar crystal spacings are large enough for electrolyte ion diffusion. In both KOH and Na2SO4 electrolytes, the α-Fe2O3 sample displays good pseudocapacitance performance. However, the specific discharge capacity and energy density in KOH are larger than in Na2SO4. In 1 mol L–1 of KOH, remarkable capacities of 139 and 35.5 F g–1 are obtained and an energy density of 3.91 and 1.01 Wh kg–1 is achieved at 1 and 20 A g–1 respectively. After 10 000 cycles, 87.7% of the specific capacitance is still retained at 1 A g–1. The good capacitance properties may attributed to the rod-like porous structure and large interplanar spacing, which provide good ion insertion–exit paths, enough oxidation–reduction active sites and a fast ion transfer velocity.

Synergistically Tailoring the Electronic Structure and Ion Diffusion of Atomically Thin Co(OH)2 Nanosheets Enable Fast Pseudocapacitive Sodium Ion Storage

AbstractThe fast‐growing development for high‐capacity anodes is undermined by their unsatisfactory rate performance and cycling stability stemming from sluggish ion‐migration speed, poor electronic conductivity, and mechanical degradation induced by the stress accumulation, which greatly hamper practical applications of Na‐ion batteries. Here, a combined experimental and theoretical study on atomic‐thickness (0.6 nm) Co(OH)2 nanosheet with surface defects (2D‐Co(OH)2@D NSs) and large interplanar spacing (0.465 nm) is presented, in which fast ion/electron transport is permitted to boost battery reactions. The mechanical degradation on cycling can be well buffered via tailoring mesopores across the Co(OH)2 nanosheet and an elastic solid–electrolyte interface is established by modulating the electronic structure of the Co(OH)2 surface. The 2D‐Co(OH)2@D NSs exhibit high rate‐capacity (>228 mAh g−1 at 20 A g−1) and superior cyclic stability with negligible decay during 1300 cycles. This study will shed light on the development of electrode materials at atomic‐level design for high‐power and long‐lived performance.

Modulating the V10O24·12H2O nanosheets decorated with carbon for enhanced and durable zinc storage

Interlayer spacing, lateral sizes and thickness of V10O24·12H2O nanosheets decorated with carbon could be modulated simply by changing the hydrothermal temperatures without forming impure phases. Ultrathin preferentially oriented V10O24·12H2O nanosheets decoated with discontinuous carbon (denoted as P-V10O24@C) with large interplanar spacing (1.42 nm) and small sizes are synthesized through a facile hydrothermal reaction. Due to the large interplanar spacing, the ultrathin nature of the P-V10O24@C nanosheets (∼1.6 nm thick) and the small holes in the nanosheets, the as-prepared 3D networks of P-V10O24@C nanosheets display enhanced performance for zinc storage. By using the 3D P-V10O24@C as the cathode of zinc-ions batteries, the sample delivers superior capacities of 448.9 mA h g−1 and 175.6 mA h g−1 at current densities of 0.5 and 20 A g−1 respectively, much higher than the non-preferentially orientated V10O24·12H2O nanosheets decorated with carbon (denoted as NP- V10O24@C) with smaller interlayer distances and large sizes. The P-V10O24@C nanosheets display superior cycling stability, an 88.9 % capacity retention is obtained after 10,000 cycles at 10 A g−1. Besides, it provides a simple and scalable strategy to modulate the mixed valenced vanadium oxides nanosheets decorated with carbon for energy storage and conversion.

Phase field modeling of dislocations and obstacles in InSb

We present a phase-field dislocation dynamics (PFDD) model informed by first-principle calculations to elucidate the competitive dislocation nucleation and propagation between the glide and shuffle sets in InSb diamond cubic crystal. The calculations are directly informed with generalized stacking fault energy curves on the (111) slip plane for both the “glide set,” with the smaller interplanar spacing, and the “shuffle set,” with the larger interplanar spacing. The formulation also includes elastic anisotropy and the gradient term associated with the dislocation core. The PFDD calculations show that under no stress the equilibrium structure of screw glide set dislocations dissociates into Shockley partials, while those of the shuffle set dislocations do not dissociate, remaining compact. The calculated dislocation core widths of these InSb dislocations agree well with the measured values for other semiconductor materials, such as Si and GaN. We find that a shuffle set dislocation emits from a dislocation source at an applied stress about three times smaller than that needed to emit leading and trailing partials successively on the glide set plane. Once the partial dislocations in the glide set are emitted, they propagate faster than the shuffle set perfect dislocation at the same stress level.

Investigation and Design of Soybean-Derived Carbon Anode Materials for Potassium-Ion Battery Applications

Lithium-ion battery (LIBs) system is one the most widely used energy storage systems in today’s renewable energy field. However, with the dramatically increased demand over the past decades and limited core material storage, concerns arise regarding its sustainability and large-scale applications. While trying to make more efficient LIBs, the studies of alternative battery systems also appear to be more and more critical. Among many newly studied battery systems, Potassium-ion batteries (PIBs) have caught our attention. With the advantage of high abundance of Potassium (K) and low redox potential of K/K+ (2.93 V vs. standard hydrogen electrode), it appears to be a perfect candidate for substituting many of the current LIBs applications. However, the absence of a suitable carbon anode has hindered the development of PIBs. Herein, we used low-cost and abundant soybean as base material and developed a high-performance hard carbon anode for PIBs. Hard carbon, produced with 500 degrees process, exhibited the highest discharge capacity of 225 mA h g-1, long lifetime of 900 cycles, and good rate capability. Benefited from low activation temperature, the soybean-derived carbon has a medium surface area, large interplanar spacing graphene layers and low degree of graphitization, which are favored by the adsorption-dominated K-ion storage mechanism. To further improve the anode efficiency, a thin layer of Al2O3 coating (~ 2 nm) was applied on the hard carbon by Atomic Layer Deposition (ALD) to function as artificial solid electrolyte interphase and increased the Coulombic efficiency from 99.0% to 99.6%. After investigating the relationship among electrochemical performance, material interface, structural design, and mechanism of potassium-ion storage, we provided new insights for the design and synthesis of carbonaceous materials with improved storage capacity and efficiency for future developments of PIBs.

Effect of hatch space on morphology and tensile property of laser powder bed fusion of Ti6Al4V

Additive manufacturing shows advantages in fabricating TC4 parts, and hatch space (HS) is one of the basic process parameters for optimization and quality improvement of the final products. In this work, the effect of HS on roughness of the single layer, and top and side surfaces, fracture morphology, tensile properties as well as structure refinement of the printed TC4 parts was studied by experiment systematically. The results show that the trend of the roughness change differs for the single layer and bulk pieces due to the scanning strategy and accumulation effect. Under the optimized process parameters, the total tensile extension can be further increased to more than 15% without decreasing the tensile strength by only increasing HS to 210 μm, whose overlapping rate is about –23%. Under the heat treatment at 800 °C for 2 h, its total extension is the highest among other HS due to lower texture and increased content of β phase, which is caused by low temperature gradient and the solid-state phase transformation, and they lead to less columnar grains, larger interplanar spacing and lattice parameters. Its fracture mechanism is based on the aggregation of micro-voids generated from the printing and tensile processing.

Ultrathin Carbon Coated Preferentially Orientated V10o24·12h2o Nanosheets with Large Interplanar Spacing Toward Superior Zinc Storage

Ultrathin Carbon Coated Preferentially Orientated V10o24·12h2o Nanosheets with Large Interplanar Spacing Toward Superior Zinc Storage

A Facile Synthesis of Ultrathin Carbon Nanosheets with Large Interplanar Spacing for Sodium-Ion Battery Anode

A Facile Synthesis of Ultrathin Carbon Nanosheets with Large Interplanar Spacing for Sodium-Ion Battery Anode

Exploring sodium storage mechanism of topological insulator Bi2Te3 nanosheets encapsulated in conductive polymer

Topological insulator has attracted worldwide attention due to its promising application prospects in magnetoresistive devices, optoelectronic devices, spintronic and quantum computing. Nevertheless, its potential in electrochemical energy storage have not been fully explored and utilized. In this paper, a composite of high conductive polypyrrole encapsulated Bi2Te3, a hexagonal phase topological insulator, was synthesized by one-step solvothermal method, and its electrochemical properties were extensively studied. Benefiting from the inherent characteristics of topological insulator, the effective polypyrrole coating, and the intrinsic large interplanar spacing within Bi2Te3, the obtained Bi2Te3@PPy composite exhibited high specific capacity, high-rate capability, and long-term cyclic stability compared with other Bi-based materials in sodium ion batteries system. Furthermore, the reaction mechanism of conversion combined with alloying for Bi2Te3@PPy was revealed by in-situ XRD and ex-situ TEM techniques. The DFT calculations shown that the sandwiching interlayer between Bi2Te3 and PPy would familiar to the Na+ transfer, and the narrowing band gap would enhance the conductivity of the system, which will not only help us to better understand the sodium storage mechanism and reaction kinetics of Bi2Te3, but also provides a reliable strategy for the development of topological insulator as sodium-ion batteries anode materials.

Resolving the Geometry/Charge Puzzle of the c(2 × 2)-Cl Cu(100) Electrode.

Potential-induced changes in charge and surface structure are significant drivers of the reactivity of electrochemical interfaces but are frequently difficult to decouple from the effects of surface solvation. Here, we consider the Cu(100) surface with a c(2 × 2)-Cl adlayer, a model surface with multiple geometry measurements under both ultrahigh vacuum and electrochemical conditions. Under aqueous electrochemical conditions, the measured Cu-Cl interplanar separation (dCu-Cl) increases by at least 0.3 Å relative to that under ultrahigh vacuum conditions. This large geometry change is unexpected for a hydrophobic surface, and it requires invoking a negative charge on the Cl-covered surface which is much greater than expected from the work function and our capacitance measurements. To resolve this inconsistency we employ ab initio calculations and find that the Cu-Cl separation increases with charging at a rate of 0.7 Å/e- per Cl atom. The larger Cu-Cl bond distance increases the surface dipole and, therefore, the work function of the interface, contributing to the negative charge under fixed potential electrochemical conditions. Interactions with water are not needed to explain either the large charge or large Cu-Cl interplanar spacing of this surface under electrochemical conditions.

Electrochemical performance of LiFePO4/graphene composites at low temperature affected by preparation technology

Many strategies have been employed to enhance the electrical conductivity and lithium ion diffusion of LiFePO4 under hydrothermal method. But the modification of the crystal structure affected by preparation technology as well as the influence of the modification on the electrochemical performance at low temperature are not fully understood. This paper systematically reports the LiFePO4/graphene nanocomposites synthesized with different preparing techniques. Among the four methods employed, LiFePO4/graphene nanocomposites synthesized by stirring and dropping method obtains smaller potential difference, less charge transfer resistance and reduced polarization resulting from larger interplanar spacing, less Fe-Li anti-site defects and higher conductivity. The systematical study of charge transfer resistance, Li+ diffusion coefficient, capacity and activation energy at 2.5 - 4.3 V from -30 - 50 °C indicates that compared with charge transfer process, lithium ion diffusion is the rate-determining step and that there is a transition from semi-infinite diffusion-controlled behavior to surface-controlled energy storage process as the temperature drops. The as-prepared sample acquires enhanced discharge capacity as high as 93.6 mAh g−1 (0.5 C) at -30 °C and better rate performance both. Simulation reveals that the lithium ion diffusion process is substantially impeded at low temperature resulting in uneven Li+ distribution in the electrode.

Few-layered MoS2 with expanded interplanar spacing strongly encapsulated inside compact carbon spheres by C–S interaction as ultra-stable sodium-ion batteries anode

Graphite-like metal sulfides, MoS2, is regarded as potential electrode of sodium-ion batteries (SIBs) because of its relatively large interplanar spacing (0.62 nm) and outstanding theoretical capacity (670 mA h g−1). However, original MoS2 electrode often suffered from shortened cycle life and poor rate capability owing to the serious volume change during sodium insertion/extraction and inferior inherent conductivity. Herein, MoS2/C compact spheres (MoS2/C CSs) with dense structure constituted by few-layered MoS2 and conductive carbon coating are successfully developed using a in-situ synthesis method. As anode of SIBs, MoS2/C CSs achieve a high capacity of 425 mA h g−1 after 200 cycles at 0.1 A g−1 with initial coulombic efficiency up to 84.8%. The reversible capacity is still maintained in 320 mA h g−1 after 400 cycles at 1 A g−1, which is three times of original MoS2 (110 mA h g−1). Besides, MoS2/C CSs also have considerable rate performance, reserving impressive capacity (310 mA h g−1) at 5.0 A g−1. The compact and conductive carbon coating effectively inhibits volume expansion and improves electrical conductivity, meanwhile, the few-layered MoS2 nanoflakes with ampliative interplanar spacing (0.73 nm) simplify the Na+ diffusion pathway and promote rapid diffusion of Na+. Furthermore, the C–S chemical bond tightly interlocks MoS2 and C, which guarantees the above mechanisms synergistically and continuously intensify the property of MoS2/C CSs anode. The above results are verified by ex-situ impedance, phase and morphology analysis.

Structural and interface design of hierarchical porous carbon derived from soybeans as anode materials for potassium-ion batteries

Potassium-ion batteries (KIBs) are an attractive energy storage system for large-scale applications, due to the high abundance of potassium (K) and low redox potential of K/K+. However, the development of KIBs has been hindered by the absence of a suitable carbon anode. Herein, we developed a high-performance hard carbon anode for KIBs by using low-cost and abundant soybeans as the starting material. The hard carbon obtained at 500 °C exhibited the highest discharge capacity of 225 mA h g−1, good rate capability, and long lifetime of 900 cycles. Low activation temperature yielded hard carbon with medium surface area, large interplanar spacing of graphene layers, and low degree of graphitization, which favored adsorption-dominated K-ion storage mechanism and were considered as the key merits for the soybeans-derived carbon anode for KIBs. Moreover, a thin Al2O3 coating (~2 nm) by atomic layer deposition was used as an artificial solid electrolyte interphase on hard carbon, and improved the average Coulombic efficiency from 99.0% to 99.6%. Clarification on the correlation among electrochemical performance, structural and physical properties, and K-ion storage mechanism of hard carbon provides new insights critical for knowledge-based design and synthesis of carbonaceous materials with improved K-ion storage capacity and efficiency for practical KIBs.

Advanced MoSe2/Carbon Electrodes in Li/Na‐Ions Batteries

AbstractSecondary charge batteries have captured numerous attentions, owing to their abundant raw, portability, and high energy density. As the main ions‐storage carrier, the electrode materials serve vital roles on the properties of whole battery system. Currently, MoSe2 is regarded as rising star of transition metal dichalcogenides, displaying unique layered structure, high electronic conductivity, as well as narrow energy band. These advantages enable their widely application on hydrogen evolution reactions and solar cells. Recently, a plenty of researching activities on MoSe2/carbon are triggered due to large interplanar spacing and high ions/e− migration rate. In this review, the recent achievements of diverse MoSe2/carbon on great energy‐storage domains are solidly summarized from bonding types (surface‐loading, internal‐wrapped) and dimensional controlling (1D nanotubes/nanofibers, 2D graphene/nanosheets, 3D carbon framework/sphere). Meanwhile, the related Li/Na ions‐storage mechanisms are also concluded. Furthermore, for MoSe2/carbon with better electrochemical properties, the opportunities and perspectives in the future are also suggested. This review throws light on the systematic developments of advanced MoSe2/carbon, and confirms its exploring potential on lithium‐ion batteries/sodium‐ion batteries.

Lamellar V5O12·6H2O Nanobelts Coupled with Inert Zn(OH)2·0.5H2O as Cathode for Aqueous Zn2+/Nonaqueous Na+ Storage Applications

Lamellar V5O12·6H2O nanobelts coupled with inert Zn(OH)2·0.5H2O are in situ fabricated via a facile hydrothermal strategy. Herein, the inert Zn(OH)2·0.5H2O phase acts as a buffer matrix to strengthen the structural stability of V5O12·6H2O host material, relieving the severe volume variation. Therefore, benefiting from the large interplanar spacing of active V5O12·6H2O and volume buffering effect of inert Zn(OH)2·0.5H2O, V5O12·6H2O/Zn(OH)2·0.5H2O hybrid (denoted as Z‐V5O12·6H2O) sustainably endures the repetitive Zn2+/Na+ insertion/extraction and boosts the electrochemical properties. As cathodes for aqueous zinc‐ion batteries, the Z‐V5O12·6H2O hybrid shows a high discharge capacity of 328 mAh g−1 at 50 mA g−1 and keeps 146 mAh g−1 at 1 A g−1 after 1000 cycles. For nonaqueous sodium‐ion batteries, the hybrid also furnishes a high initial discharge capacity of 241 mAh g−1 at a current density of 50 mA g−1 and maintains 97 mAh g−1 at 100 mA g−1 after 100 cycles.