Reversible Mn^(2+)/Mn^(4+)double-electron redox in P3-type layer-structured sodium-ion cathode

The balance between cationic redox and oxygen redox in layer-structured cathode materials is an important issue for sodium batteries to obtain high energy density and considerable cycle stability.Oxygen redox can contribute extra capacity to increase energy density,but results in lattice instability and capacity fading caused by lattice oxygen gliding and oxygen release.In this work,reversible Mn^(2+)/Mn^(4+)redox is realized in a P3-Na_(0.65)Li_(0.2)Co_(0.05)Mn_(0.75)O_(2)cathode material with high specific capacity and structure stability via Co substitution.The contribution of oxygen redox is suppressed significantly by reversible Mn^(2+)/Mn^(4+)redox without sacrificing capacity,thus reducing lattice oxygen release and improving the structure stability.Synchrotron X-ray techniques reveal that P3 phase is well maintained in a wide voltage window of 1.5-4.5 V vs.Na^(+)/Na even at 10 C and after long-term cycling.It is disclosed that charge compensation from Co/Mn-ions contributes to the voltage region below 4.2 V and O-ions contribute to the whole voltage range.The synergistic contributions of Mn^(2+)/Mn^(4+),Co^(2+)/Co^(3+),and O^(2-)/(O_n)^(2-)redox in P3-Na_(0.65)Li_(0.2)Co_(0.05)Mn_(0.75)O_(2)lead to a high reversible capacity of 215.0 m A h g^(-1)at 0.1 C with considerable cycle stability.The strategy opens up new opportunities for the design of high capacity cathode materials for rechargeable batteries.

Analysis of Boundary Layer Structure,Turbulence,and Flux Variations before and after the Passage of a Sea Breeze Front Using Meteorological Tower Data

A detailed analysis of a sea breeze front(SBF)that penetrated inland in the Beijing–Tianjin–Hebei urban agglomeration of China was conducted.We focused on the boundary layer structure,turbulence intensity,and fluxes before and after the SBF passed through two meteorological towers in the urban areas of Tianjin and Beijing,respectively.Significant changes in temperature,humidity,winds,CO_(2),and aerosol concentrations were observed as the SBF passed.Differences in these changes at the two towers mainly resulted from their distances from the ocean,boundary layer conditions,and background turbulences.As the SBF approached,a strong updraft appeared in the boundary layer,carrying near-surface aerosols aloft and forming the SBF head.This was followed by a broad downdraft,which destroyed the near-surface inversion layer and temporarily increased the surface air temperature at night.The feeder flow after the thermodynamic front was characterized by low-level jets horizontally,and downdrafts and occasional updrafts vertically.Turbulence increased significantly during the SBF’s passage,causing an increase in the standard deviation of wind components in speed.The increase in turbulence was more pronounced in a stable boundary layer compared to that in a convective boundary layer.The passage of the SBF generated more mechanical turbulences,as indicated by increased friction velocity and turbulent kinetic energy(TKE).The shear term in the TKE budget equation increased more significantly than the buoyancy term.The atmosphere shifted to a forced convective state after the SBF’s passage,with near isotropic turbulences and uniform mixing and diffusion of aerosols.Sensible heat fluxes(latent heat and CO_(2)fluxes)showed positive(negative)peaks after the SBF’s passage,primarily caused by horizontal and vertical transport of heat(water vapor and CO_(2))during its passage.This study enhances understanding of boundary layer changes,turbulences,and fluxes during the passage of SBFs over urban areas.

Layered Structural PBAT Composite Foams for Efficient Electromagnetic Interference Shielding

The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.

Tuning the layer structure of molybdenum trioxide towards high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries(ZIBs) have attracted significant attentions because of low cost and high reliability. However, conventional ZIBs are severely limited by the development of high energy density cathode materials with reversible Zn^(2+)insertion/extraction. Herein, a conducting polymer intercalated MoO_(3)(PMO) with extensively extended interlayer spacing is developed as a high-performance ZIBs cathode material. The interlayer spacing of PMO is prominently increased which results in an improved Zn^(2+)mobility during charge and discharge process. More significantly, the electrochemical results reveals that the intercalation of PANI facilitates the charge storage and reinforces the layered structure of MoO_(3), leading to a high capacity and good cycling stability. DFT calculation further reveals the intercalation of PANI into MoO_(3)significantly lower Zn^(2+)diffusion barrier. Benefit from these advantages, the ZIBs based on PMO electrode delivers a considerable capacity of 157 m Ah/g at 0.5 A/g and ameliorative stability with 63.4%capacity retention after 1000 cycles.

LiZr_(2)(PO_(4))_(3)surface coating towards stable layer structure Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2)cathode materials with long cycle performance

Li-rich manganese-based materials are considered to be the mainstream cathode materials for next-generation lithium-ion batteries due to high discharge capacity and low cost,but poor cycle life and high temperature performance limit their development.Herein,LiZr_(2)(PO_(4))_(3)(LZPO)is coated on the surface of spherical Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2)(LMNCO)material by a simple wet chemical method.The LZPO layer not only has the function of traditional coating layer to inhibit the occurrence of side reactions between electrolyte and LMNCO surface but also promotes the formation of spinel phase in the layered structure,increases the content of lattice oxygen,and reduces the content of absorbed oxygen.Thus,LZPO coated LMNCO has a more stable layered structure during cycling compared pure LMNCO,which improves effectively its long life and high temperature performance.The capacity loss rate of LZPO coated LMNCO is only 16.2%and 11.9%after 350 cycles at 25℃and 200 cycles at 50℃,respectively.Moreover,the capacity retention rate of the full cell composed of LZPO coated LMNCO and graphite is 70.7%after 200 cycles at 1.0 C.The coating layer toward stable surface structure can provide an idea for the modification of cathode materials,especially for Li-rich manganese-based materials.

High-Throughput Growth of Hexagonal Boron Nitride Film Using Porous-Structure Isolation Layer

Chemical vapor deposition is considered as the most hopeful method for the synthesis of large-area high-quality hexagonal boron nitride on the substrate of catalytic metal. However, the size the hexagonal boron nitride films are limited to the size of growth chamber, which indicates a lower production efficiency. In this paper, the utilization efficiency of growth chamber is highly improved by alternately stacking multiple pieces of Cu foils and carbon fiber surface felt with porous structure. Uniform and continuous hexagonal boron nitride films are prepared on Cu foils through chemical vapor deposition utilizing ammonia borane as the precursor. This work develops a simple and practicable method for high-throughput preparation of hexagonal boron nitride films, which could contribute to the industrial application of hexagonal boron nitride. .

Difficulties, strategies, and recent research and development of layered sodium transition metal oxide cathode materials for high-energy sodium-ion batteries

Energy-storage systems and their production have attracted significant interest for practical applications.Batteries are the foundation of sustainable energy sources for electric vehicles(EVs),portable electronic devices(PEDs),etc.In recent decades,Lithium-ion batteries(LIBs) have been extensively utilized in largescale energy storage devices owing to their long cycle life and high energy density.However,the high cost and limited availability of Li are the two main obstacles for LIBs.In this regard,sodium-ion batteries(SIBs) are attractive alternatives to LIBs for large-scale energy storage systems because of the abundance and low cost of sodium materials.Cathode is one of the most important components in the battery,which limits cost and performance of a battery.Among the classified cathode structures,layered structure materials have attracted attention because of their high ionic conductivity,fast diffusion rate,and high specific capacity.Here,we present a comprehensive review of the classification of layered structures and the preparation of layered materials.Furthermore,the review article discusses extensively about the issues of the layered materials,namely(1) electrochemical degradation,(2) irreversible structural changes,and(3) structural instability,and also it provides strategies to overcome the issues such as elemental phase composition,a small amount of elemental doping,structural design,and surface alteration for emerging SIBs.In addition,the article discusses about the recent research development on layered unary,binary,ternary,quaternary,quinary,and senary-based O3-and P2-type cathode materials for high-energy SIBs.This review article provides useful information for the development of high-energy layered sodium transition metal oxide P2 and O3-cathode materials for practical SIBs.

Secondary Instability of Large Scale Structure in Free Turbulent Shear Layer

ＳＥＣＯＮＤＡＲＹＩＮＳＴＡＢＩＬＩＴＹＯＦＬＡＲＧＥＳＣＡＬＥＳＴＲＵＣＴＵＲＥＩＮＦＲＥＥＴＵＲＢＵＬＥＮＴＳＨＥＡＲＬＡＹＥＲＺｈａｏＧｅｎｇ－ｆｕ（赵耕夫）（ＴｉａｎｊｉｎＵｎｉｖｅｒｓｉｔｙ，Ｔｉａｎｊｉｎ．３０００７２．Ｐ．Ｒ．Ｃｈｉｎａ...

Layer stacked SiO_(x) microparticle with disconnected interstices enables stable interphase and particle integrity for lithium-ion batteries

Severe mechanical fractu re and unstable interphase,associated with the large volumetric expansion/contraction,significantly hinder the application of high-capacity SiO_(x)materials in lithium-ion batteries.Herein,we report the design and facile synthesis of a layer stacked SiO_(x)microparticle(LS-SiO_(x))material,which presents a stacking structure of SiO_(x)layers with abundant disconnected interstices.This LS-SiO_(x)microparticle can effectively accommodate the volume expansion,while ensuring negligible particle expansion.More importantly,the interstices within SiO_(x)microparticle are disconnected from each other,which efficiently prevent the electrolyte from infiltration into the interior,achieving stable electrode/-electrolyte interface.Accordingly,the LS-SiO_(x)material without any coating delivers ultrahigh average Coulombic efficiency,outstanding cycling stability,and full-cell applicability.Only 6 cycles can attain>99.92%Coulombic efficiency and the capacity retention at 0.05 A g^(-1)for 100 cycles exceeds99%.After 800 cycles at 1 A g^(-1),the thickness swelling of LS-SiO_(x)electrode is as low as 0.87%.Moreover,the full cell with pure LS-SiO_(x)anode exhibits capacity retention of 91.2%after 300 cycles at 0.2 C.This work provides a novel concept and effective approach to rationally design silicon-based and other electrode materials with huge volume variation for electrochemical energy storage applications.

Nacre-inspired interface structure design of polymer bonded explosives toward significantly enhanced mechanical performance

Realizing effective enhancement to the structure of interface region between explosive crystals and polymer binder plays a key role in improving the mechanical properties of the current polymer bonded explosives(PBXs).Herein,inspired by the structure of natural nacre which possesses outstanding mechanical performance,a kind of nacre-like structural layer is constructed in the interface region of PBXs composites,making use of two-dimensional graphene sheets and one-dimensional bio-macromolecules of cellulose as inorganic and organic building blocks,respectively.Our results reveal that the constructed nacre-like structural layer can effectively improve the interfacial strength and then endow the PBXs composites with significantly enhanced mechanical properties involving of creep resistance,Brazilian strength and fracture toughness,demonstrating the obvious advantage of such bioinspired interface structure design strategy.In addition,the thermal conduction performance of PBXs composites also exhibits noticeable enhancement due to the remarkable phonon transport capability endowed by the asdesigned nacre-like structural layer.We believe this work provides a novel design route to conquer the issue of weak interfacial strength in PBXs composites and greatly increase the comprehensive properties for better meeting the higher requirements proposed to the explosive part of weapon equipment in new era.

A New 2D Double-layer Network Constructed from a 2D Single Layer

Two Zn(II) coordination polymers, namely [Zn_2(bpy)(aobtc)(H_2O)_2]·2H_2O(1) and [Zn_2(bpy)(aobtc)(H_2O)]·4H_2O(2)(bpy = 4,4?-bipyridine, H4 aobtc = 3,3?,5,5?-azoxybenzenetetracarboxylic acid) have been hydrothermally synthesized through tuning the p H value of the reaction system(1, C_(26)H_(22)N_(4)O_(13)Zn_2, Mr = 729.21; 2, C_(26)H_(24)N_4O_(14)Zn_2, Mr = 747.23), and their structures have been determined by single-crystal X-ray diffraction analyses. Compound 2 has been further characterized by infrared spectra(IR), elemental analyses, thermal analyses and powder X-ray diffraction(PXRD) analyses. Additionally, the photoluminescence of 2 is also discussed. The structure demonstrates that the crystal of 2 belongs to the triclinic system, space group P1 with a = 8.41494(18), b = 9.59838(19), c = 17.6477(3) ?, α = 91.5098(16), β = 98.1439(17), γ = 90.4323(17)°, V = 1410.44(5) ?3, Z = 2, ρcalc = 1.759 g/cm^3, μ = 2.819 mm-1, F(000) = 760.0, R = 0.0311 and w R = 0.0839(I > 2σ(I)). Compound 1 shows a two-dimensional monolayer while compound 2 displays a novel 2D double-layered network constructed from monolayer motifs, which is similar to the single layer in 1. Further, each bilayer motif in 2 is interdigitated by two others in a parallel fashion to yield an unusual 2D → 3D interdigitated framework.

Well-ordered layered LiNi0.8Co0.1Mn0.1O2 submicron sphere with fast electrochemical kinetics for cathodic lithium storage

Nickel-rich layered oxides have drawn sustainable attentions for lithium ion batteries owing to their higher theoretical capacities and lower cost.However,nickel-rich layered oxides also have exposed several defects for commercial application,such as uncontrollable ordered layered structure,which leads to higher energy barrier for Li+diffusion.In addition,suffering from structural mutability,the bulk nickelrich cathode materials likely trigger overall volumetric variation and intergranular cracks,thus obstructing the lithium ion diffusion path and shortening the service life of the whole device.Herein,we report wellordered layered Li Ni0.8Co0.1Mn0.1O2 submicron spheroidal particles via an optimized co-precipitation and investigated as LIBs cathodes for high-performance lithium storage.The as-fabricated Li Ni0.8Co0.1Mn0.1O2 delivers high initial capacity of 228 mAh g–1,remarkable energy density of 866 Wh kg–1,rapid Li ion diffusion coefficient(10–9cm2s–1)and low voltage decay.The remarkable electrochemical performance should be ascribed to the well-ordered layered structure and uniform submicron spheroidal particles,which enhance the structural stability and ameliorate strain relaxation via reducing the parcel size and shortening Li-ion diffusion distance.This work anticipatorily provides an inspiration to better design particle morphology for structural stability and rate capability in electrochemistry energy storage devices.

Layered Birnessite Cathode with a Displacement/Intercalation Mechanism for High-Performance Aqueous Zinc-Ion Batteries

Mn-based rechargeable aqueous zinc-ion batteries(ZIBs)are highly promising because of their high operating voltages,attractive energy densities,and eco-friendliness.However,the electrochemical performances of Mn-based cathodes usually suffer from their serious structure transformation upon charge/discharge cycling.Herein,we report a layered sodium-ion/crystal water co-intercalated Birnessite cathode with the formula of Na0.55Mn2O4·0.57H2O(NMOH)for high-performance aqueous ZIBs.A displacement/intercalation electrochemical mechanism was confirmed in the Mn-based cathode for the first time.Na+and crystal water enlarge the interlayer distance to enhance the insertion of Zn^2+,and some sodium ions are replaced with Zn^2+ in the first cycle to further stabilize the layered structure for subsequent reversible Zn^2+/H^+ insertion/extraction,resulting in exceptional specific capacities and satisfactory structural stabilities.Additionally,a pseudo-capacitance derived from the surface-adsorbed Na^+ also contributes to the electrochemical performances.The NMOH cathode not only delivers high reversible capacities of 389.8 and 87.1 mA h g^−1 at current densities of 200 and 1500 mA g^−1,respectively,but also maintains a good long-cycling performance of 201.6 mA h g^−1 at a high current density of 500 mA g^−1 after 400 cycles,which makes the NMOH cathode competitive for practical applications.

Layered hydrated vanadium oxide as highly reversible intercalation cathode for aqueous Zn-ion batteries

Aqueous Zn-ion batteries(ZIBs)hold great potential in large-scale energy storage systems due to the merits of low-cost and high safety.However,the unstable structure of cathode materials and sluggish(de)intercalation kinetics of Zn2+pose challenges for further development.Herein,highly reversible aqueous ZIBs are constructed with layered hydrated vanadium oxide as a cathode material.The electrochemical performances are further tested with the optimized electrolyte of 3M Zn(CF3SO3)2 and a cut-off voltage of 0.4 to 1.3 V,exhibiting a remarkable capacity of 290mAh g−1 at 0.5Ag−1,and long-term cycling stability at high current density.Furthermore,the Zn2+storage mechanism of V3O7⋅H2O is recognized as a highly reversible(de)intercalation process with good structural stability,implying the potential application in the field of large-scale energy storage.

Layered Ag-graphene films synthesized by Gamma ray irradiation for stable lithium metal ano des in carb on ate-based electrolytes

Lithium metal batteries are considered as high energy density battery systems with very promising prospects and have bee n widely studied.However,The uncon trollable plating/strippi ng behavior,infinite volume change and den drites formation of lithium metal anode restrict the applicati on.The unc on trolled n ucleati on of lithium caused by the non uniform multi-physical field distributions,can lead to the undesirable lithium deposition.Herein,a graphene composite uniformly loaded with Ag nano-particles(Ag NPs)is prepared through a facile Gamma ray irradiation method and assembled into self-supported film with layered structure(Ag-rGO film).Whe n such film is used as a lithium metal an ode host,the uncontrolled deposition is converted into a highly nucleation-induced process.On one hand,the Ag NPs distributed between the in terlayers of graphe ne can preferentially induce lithium nu cleati on and en able uniform deposition morphology of lithium between interlayers.On the other hand,the stable layered graphene structure can accommodate volume change,stabilize the interface between anode and electrolyte and inhibit dendrites formation.Therefore,the layered Ag-rGO film as anode host can reach a high Coulombic efficiency over 93.3% for 200 cycle(786 h)at a current density of 1 mA cm^(-2) for 2 mAh cm^(-2) in carbonate-based electrolyte.This work proposes a facile Gamma ray irradiation method to prepare metal/3D-skeleton structure as lithium anode host and demonstrates the potential to regulate the lithium metal deposition behaviors via manipulating the distribution of lithiophilic metal(e.g.Ag)in 3D frameworks.This may offer a practicable thinking for the subsequent design of the lithium metal anode.

Structure-dependent re-dispersibility of graphene oxide powders prepared by fast spray drying

The graphene oxide powder(GOP)obtained from the spray drying process often exhibits poor redispersibility which is considered due to the partial reduction of GO sheets.The reduction of drying temperature can effectively increase the redispersibility of GOP,but result in a decreased drying efficiency.Herein,we found that the redispersibility of GOP is strongly affected by its microstructure,which is determined by the feed concentration.With the increase of feed concentration,the GO nanosheet assembly varies from the disordered stacking to relatively oriented assembly,making the morphology of the GOP transform from balllike(the most crumpled one)to flakelike(the least crumpled one),and the 0.8 mgml 1 is the threshold concentration for the morphology,structure,and redispersibility change.Once the feed concentration reaches 0.8 mg ml 1,the appearance of the nematic phase in droplet ensures the relatively oriented assembly of GO sheets to form the layered structure with a low crumpling degree,which greatly improves the polar parts surface tension of the solid GOP,making the GOP easier to form hydrogen bonding with water during the redispersion process,thus stabilizing dispersion.This work provides useful information for understanding the relationships between the morphology,microstructure,and final redispersibility of GOPs.

Synthesis,Crystal Structure and Electronic Structure of Novel Semiconducting KCdAsS_3

A new compound of KCdAsS_3(Mr = 322.60) was successfully synthesized using thiourea reactive flux method. The crystal structure was determined by single-crystal X-ray diffraction. The title compound crystallizes in a monoclinic system of space group P21/n with a = 5.9537(7), b = 16.633(3), c = 6.093(1) ?, b = 90.781(3)°, V = 610.0(1) ?3, Z = 4, Dc = 3.513 g/cm3, m(Mo Kα) = 10.52 mm-1, F(000) = 592, R = 0.057 and w R = 0.136 for 899 observed reflections with I > 2σ(I). The crystal structure of KCdAsS_3 features [Cd As S3]-layers, which are separated by K+ ions. First-principles calculations show that KCdAsS_3 is an indirect band gap semiconductor with a band gap of 2.3 e V. The novel layered compound of tetrahedra CdS_4 and pyramids AsS_3 is potentially useful for photoluminescent, photocatalytic and photoelectric applications.

Characteristic analysis of layered PMSEs measured with different elevation angles at VHF based on an experimental case

Polar Mesosphere Summer Echoes(PMSEs)are very strong radar echoes observed at altitudes near the polar summer mesopause.One of the essential properties of these radar echoes is that they can give useful diagnostic information about the physics of the scattering process.In this paper,the related characteristics of PMSEs measured with the European Incoherent SCATter Very High Frequency(EISCAT VHF)224 MHz radar on 13–15 July 2010 are studied at different elevation angles from 78°to 90°.It is found that the PMSEs peak power and strongest PMSEs average power occur at the same elevation angles.Also interesting is that the strongest PMSEs occur at off-vertical angles when a PMSEs has a layered(multilayer)structure.And reflection may have more significant effects on PMSEs when there are double or multilayer PMSEs.Possible explanations regarding these observations are discussed.

Co-modulated interface binding energy and electric field distribution of layer-structured PVDF–LDPE dielectric composites with BaTiO3: experiment and multiscale simulations

The layer-structured composites were built by the dielectric and insulating layers composed of polyvinylidene fluoride(PVDF)and low-density polyethylene(LDPE)composites containing barium titanate(BT)to modulate the dielectric and energy storage properties of the composites.The simulations on the interface models for molecular dynamics and the geometric models for finite element analysis were performed together with the experimental characterization of the morphology,dielectric,and energy storage properties of the composites.The results revealed that polyethylene as an insulating layer played a successful role in modulating dielectric permittivity and breakdown strength while BT particles exerted positive effects in improving the miscibility between the composed layers and redistributing the electric field.The strong interface binding energy and the similar dielectric permittivity between the PVDF layer and the BT20/LDPE layer made for the layer-structured composites with a characteristic breakdown strength(Eb)of 188.9 kV·mm^(−1),a discharge energy density(Ud)of 1.42 J·cm^(−3),and a dielectric loss factor(tanδ)of 0.017,which were increased by 94%,141%,and decreased by 54%in comparison with those of the BT20/PVDF composite,respectively.