Higher Shear Modulus Research Articles

Following the effect of braid architecture on performance and damage of carbon fibre/epoxy composite tubes during torsional straining

The torsional performance of bi-axially braided carbon fibre reinforced polymer (CFRP) tubes as a function of braid architecture is investigated. It is found that for a given braid pattern, the 45° braided CFRP tubes have higher shear moduli and lower shear strength than the 35° braids. In general, 2/2 (regular) braided CFRP tubes exhibit both higher shear strength and higher shear modulus than 1/1 (diamond) braids. However, beyond the peak load, the shear strength of 2/2 braided CFRPs exhibits sudden and steep drops, resulting in a lower remnant shear strength than 1/1 structures after the shear strain exceeds 4.5%. Moreover, the damage evolution is monitored in-situ by synchrotron X-ray computed tomography during torsional straining. It shows that for a 2/2 structure, inter-tow debonded regions are vertically interconnected allowing rapid crack propagation and strength drops, whereas for the 1/1 braid they are distributed in a chequer board pattern causing a more gradual loss of strength. The fibre/matrix interfacial strength and tow cross-over density play key roles in the torsional failure of 1/1 and 2/2 braided CFRP tubes, as the former controls damage initiation and the latter controls damage propagation.

Interfaces in Garnet‐Based All‐Solid‐State Lithium Batteries

AbstractAll‐solid‐state lithium batteries (ASSLBs) are considered to be the next‐generation energy storage system, because of their overwhelming advantages in energy density and safety compared to conventional lithium ion batteries. Among various systems, garnet‐based ASSLBs are one of the most promising candidates. The advantages arise from the intrinsic properties of garnet electrolytes, especially the high shear modulus and wider electrochemical window compared to that of polymer and sulfide electrolytes, guaranteeing the application of Li metal and high voltage cathodes. However, the interfacial issues between garnets and electrodes (Li metal and cathodes) are challenging and hinder the further development of garnet‐based ASSLBs. Herein, the origin of interfacial resistance and recent development of interfacial construction in garnet‐based ASSLBs are reviewed, as well as the subsequent interfacial degradation and cell failure during cycling process, including inhomogeneous plating and stripping, Li dendrites, and strain induced microcracks in stiff electrodes. Finally, the future challenges and opportunities in this important and exciting field are also presented.

Superior mechanical properties and strengthening mechanisms of lightweight AlxCrNbVMo refractory high-entropy alloys (x = 0, 0.5, 1.0) fabricated by the powder metallurgy process

Light and strong AlxCrNbVMo (x = 0, 0.5, and 1.0) refractory high-entropy alloys (RHEAs) were designed and fabricated via a the powder metallurgical process. The microstructure of the AlxCrNbVMo alloys consisted of a single BCC crystalline structure with a sub-micron grain size of 2−3 μm, and small amounts (< 4 vol.%) of fine oxide dispersoids. This homogeneous microstructure, without chemical segregation or micropores was achieved via high-energy ball milling and spark-plasma sintering. The alloys exhibited superior mechanical properties at 25 and 1000℃ compared to those of other RHEAs. Here, CrNbVMo alloy showed a yield strength of 2743 MPa at room temperature. Surprisingly, the yield strength of the CrNbVMo alloy at 1000℃ was 1513 MPa. The specific yield strength of the CrNbVMo alloy was increased by 27 % and 87 % at 25 and 1000℃, respectively, compared to the AlMo0.5NbTa0.5TiZr RHEA, which exhibited so far the highest specific yield strength among the cast RHEAs. The addition of Al to CrNbVMo alloy was advantageous in reducing its reduce density to below 8.0 g/cm3, while the elastic modulus decreased due to the much lower elastic modulus of Al compared to that of the CrNbVMo alloy. Quantitative analysis of the strengthening contributions, showed that the solid solution strengthening, arising from a large misfit effect due to the size and modulus, and the high shear modulus of matrix, was revealed to predominant strengthening mechanism, accounting for over 50 % of the yield strength of the AlxCrNbVMo RHEAs.

Abnormal Grain Growth: A Potential Way to Construct Gradient Structure

Abnormal grain growth (AGG) has been commonly observed but the mechanism still remains unclear. In this study, the formation of abnormally large grains was investigated in compressed nickel powders. By periodical sintering in the large volume press, AGG occurred and resulted in a gradient coarse-grained structure. Through the improvement of the cell assembly by introducing tungsten tablets with a higher shear modulus, the optimized grained gradient structure can be obtained, which arises from tuning the AGG associated with the suppress of deformation. This work would be a potential way to design heterogeneous gradient nanostructured materials with excellent strength and ductility.

Pentadiamond: A Hard Carbon Allotrope of a Pentagonal Network of sp^{2} and sp^{3} C Atoms.

A pentagonal covalent network consisting of sp^{2} and sp^{3} C atoms has been investigated based on the density functional theory. Our theoretical investigations clarified that the pentagonal covalent network is a metastable three-dimensional carbon allotrope with the Fm3[over ¯]m space group possessing remarkable mechanical properties: relatively high bulk modulus of 381GPa together with a negative Poisson's ratio of -0.241. Accordingly, the pentagonal covalent network possesses extremely high Young's and shear moduli of 1691 and 1113GPa, respectively, surpassing those of the diamond. The electronic structure of the pentagonal network is a semiconductor with an indirect band gap of 2.52eV between L and X points for valence and conduction band edges, respectively, with the relatively small carrier masses.

Non-uniform distribution of passive muscle stiffness within hamstring.

Limited information is available on whether stiffness is different within and between the constituents of the hamstring, that is, the biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM). Therefore, understanding of hamstring injuries and stretching effect on hamstring stiffness is difficult. The present study primarily aimed to identify whether passive muscle stiffness differs between the BFlh, ST, and SM and between the proximal, middle, and distal sites within each muscle. Secondly, the effect of stretching exercise on the heterogeneity in passive muscle stiffness was examined. In the lengthened hamstring positions by extending the knee joint or flexing the hip joint, passive muscle shear modulus (a measure of stiffness) at the proximal, middle, and distal sites of the BFlh, ST, and SM was measured by using ultrasound shear wave elastography. Furthermore, before and after five repetitions of 90-seconds static stretching for the hamstring, passive muscle shear modulus at the proximal and distal sites of the SM was measured. The shear modulus was significantly higher in the SM than in the BFlh and ST and higher at the distal site than the proximal site in all muscles. After the stretching, the higher shear modulus at the distal site of the SM compared to the proximal site was still observed (pre-stretching: +80%, post-stretching: +81%). These findings indicate that passive muscle stiffness varies within the hamstring regardless of performing stretching exercise and that passive muscle stiffness is not highest at the proximal site of the SM where a stretching-type hamstring strain typically occurs.

Effect of Sand Fouling on the Dynamic Properties and Volume Change of Gravel During Cyclic Loadings

Understanding the factors that influence the dynamic behavior of granular soils during cyclic loading is critical to infrastructure design. Previous research has lacked quantitative study of the effects of fouling index (FI), mean effective confining pressure, relative density, shear strain level and anisotropic consolidation, especially when the effective vertical stress is lower than the effective horizontal stress on the dynamic behavior of gravelly soils. The objective of the present study was to evaluate the dynamic behavior and volume change of both clean and fouled specimens for practical applications. To this end, cyclic triaxial tests with local strain measurements under both isotropic and anisotropic confining conditions were conducted. It is found that the fouled specimen with 50 % sand (i.e. the specimen which contains 50 % gravel and 50 % sand) has the highest shear modulus at low shear strain levels and the largest volume reduction and damping ratio at large shear strain levels. The results of tests indicate that the effect of fouling index on the shear modulus is reduced at large shear strain levels. Volumetric contraction due to the increase in mean effective confining pressure is more significant at large shear strain levels. The results also indicate that the stiffness of the specimens under anisotropic compression mode are larger than those in extension or isotropic mode.

Understanding compressive strength improvement of high modulus carbon-fiber reinforced polymeric composites through fiber-matrix interface characterization

Low fiber-direction compressive strength of high-modulus (HM) carbon fiber-reinforced polymers (CFRPs) has been their major weakness prohibiting implementation of such materials in aircraft primary structures despite improving mechanical stiffness at a lower weight. A new HM CFRP achieving fiber-direction compressive strength of intermediate-modulus (IM) CFRPs but with more than 30% higher axial modulus has been recently developed. This work looks into fiber-matrix interface shear strength as a potential mechanism driving the compression strength improvement of the new material system. In-situ scanning electron microscopy (SEM) based single fiber push-out experiments addressing standing challenges associated with manufacturing high-quality samples as well as distinguishing same-diameter HM and IM carbon fibers in the hybrid composite system are used to measure fiber-matrix interface shear strength. The experiments show a 29% lower average value of the fiber-matrix interface shear strength for the HM carbon fibers compared to the IM carbon fibers in the new material system. Such a significant reduction corresponds to a 22% lower fiber-direction compressive strength of the HM CFRP without the integrated IM fibers. The results support the idea of integrating off-the-shelf IM carbon fibers with a stronger fiber-matrix interface and a higher shear modulus into HM CFRPs to improve their compressive strength.

New Insights in All-Solid-State Ceramic Batteries: Dendrite Growth through Pressure and Density Effects

Despite some progress performed, state-of-the-art lithium ion batteries still require improvements in energy and power to extend the range of electric vehicles and reduce charging time. In this domain, all-solid-state batteries are viable alternatives to conventional batteries employing organic electrolytes because of their benefits, i.e., high power density, high energy density, long-life operation and safety. These advantages stem from the great features of inorganic solid electrolytes, which are single ion conductor, so a high lithium ion transport number, and no-liquid nature. In particular, the sulfide-based solid electrolytes possess favorable mechanical properties, allowing all-solid-state batteries to be easily prepared via simple mixing and cold-pressing processes, facilitating the scale-up.Sulfide-based solid-electrolytes can potentially be employed in conjunction with a lithium metal negative electrode and 5V-class high voltage positive electrode material. Indeed, lithium metal is believed to be the most promising negative electrode due to its specific large capacity (3862 mAh.g-1), low volumetric density (0.534 g.cm-3 at 20°C) and the lowest electrochemical potential (-3.03V vs ENH). Nevertheless, like most metal, lithium metal is morphologically dynamic. Its surface morphology is modified, since during the electrochemical cycling, a part of lithium migrates to the other electrode to react and is then plating on its surface heterogeneously, leading to a volume change and sometimes dendrite growth with potential internal short circuit and life-threatening accidents. Ceramic solid electrolytes have been considered to be the ideal solution to prevent dendrite growth because of their high shear modulus and high lithium transference number. In the same time, the chemical nature and composition of ceramic solid electrolyte can affect the dendrite growth by the interfacial chemical and electrochemical stability with lithium metal forming solid electrolyte interphase as a passivating layer. Since the lithium dendrites have to grow through this layer, its composition should play an important role in the dendrite formation. Moreover, it is known that the stack can be easily deformed because lithium dendrite growth with a high shear modulus, indicating that the solid electrolyte and its interface with lithium metal should be sufficiently strong to endure the pressure originating from lithium dendrite growth. The oxide–based ceramic solid electrolytes can be shaped by sintering at high temperature, leading to a grain and grain-boundary microstructure with some porosity, facilitating the lithium dendrite growth through grain boundaries. Due to the low density and plasticity of sulfide based inorganic solid electrolyte, the dendrite growth through the particle-particle contact can be reduced but still present.Different parameters can influence the lithium dendrite growth and the critical current density in ceramic all-solid-state configuration, such as the solid electrolyte chemical composition, particle size, and the compactness of ceramic solid electrolyte. The pressure effect on the electrochemical performances of sulfide electrolytes was investigated. The pressure affects resistive grain boundaries, contact between lithium metal and solid electrolyte and lithium plating. As, the kinetics of reaction is derived from thermodynamic parameters, the temperature can affect the plating/stripping phenomena. These different parameters and the relationship between them will be presented and explained through complete studies based on sulfide solid electrolytes with the combination of various chemical and electrochemical techniques.

Uniform Electrodeposition of Lithium Metal Under an Artificial Solid Electrolyte Interphase Layer

Lithium metal is one of the most promising anode materials for high energy density electrochemical energy storage. However, non-uniform electrodeposition of Li metal and dendritic growth result in low Coulombic efficiency and potential short circuits as the dendrites intrude and span the bulk electrolyte/separator region of the cells. This is one of the key stumbling blocks to further development and commercialization of Li metal batteries. To suppress the dendritic deposition of Li metal, one strategy is to encapsulate the Li metal with an artificial solid electrolyte interface (SEI) layer. The ideal artificial SEI layer should possess high mechanical strength and stiffness to prevent the intrusion of Li filaments, high Li transference number, low interfacial resistance, and high ionic yet negligible electronic conductivity. Moreover, recent studies show that the morphology of SEI layer is critical, and it is believed that a homogeneous, isotropic surface is required. The thin film solid electrolyte, lithium phosphorous oxynitride (LiPON), satisfies all of these properties. It has a relatively high shear modulus of 7.7 GPa, unity transference number, electrochemical stability window spanning from 0 up to 5.5 V vs. Li/Li+, ionic conductivity of 2×10-6 S cm-1, electronic conductivity of 8×10-13 S cm-1, and is fabricated as a smooth isotropic, homogenous thin film via physical vapor deposition. Uniform, reversible plating/stripping of Li metal under LiPON layers has been clearly demonstrated in thin film batteries, but fundamental questions remain regarding the physical and electrochemical processes during Li deposition in hybrid electrolyte cells, where LiPON-protected Li metal anodes are employed in combination with liquid electrolytes.In this study, the electrodeposition of Li on Au current collectors coated with a thin LiPON protective layer was studied, and it was shown that compared to Cu current collectors, the Au layers promote uniform electrodeposition of Li metal. The Au layers alloy with Li, reducing the nucleation overpotential and resulting in a more spatially uniform metal deposit. The LiPON protective layer remains intact during the Li plating process, preventing reaction between the liquid electrolyte and Li metal. The effectiveness of the LiPON protective layer was assessed using x-ray photoelectron spectroscopy (XPS) to characterize the surface chemistry of both LiPON-protected and unprotected Li electrodeposits in liquid electrolytes. The effect of current density and plated capacity on the morphology of plated Li on LiPON and Au current collectors was also studied. Smooth, homogeneous deposits of Li under LiPON layers were maintained for capacities up to 3 mAh cm-2 plated at 0.1 mA cm-2. As the plating current density increased up 1 mA cm-2, the LiPON coating fractured due to the localized, nonuniform lithium deposits and rough, dendritic Li morphologies were observed. In operando impedance spectroscopy during Li plating resolved key resistances in the plating process and demonstrated the integrity of the LiPON layers. Efforts to further optimize these protective LiPON layers and deeply understand the Li plating process will be discussed. Figure 1

Universal chemomechanical design rules for solid-ion conductors to prevent dendrite formation in lithium metal batteries.

Dendrite formation during electrodeposition while charging lithium metal batteries compromises their safety. Although high-shear-modulus (Gs) solid-ion conductors (SICs) have been prioritized to resolve the pressure-driven instabilities that lead to dendrite propagation and cell shorting, it is unclear whether these or alternatives are needed to guide uniform lithium electrodeposition, which is intrinsically density-driven. Here, we show that SICs can be designed within a universal chemomechanical paradigm to access either pressure-driven dendrite-blocking or density-driven dendrite-suppressing properties, but not both. This dichotomy reflects the competing influence of the SIC's mechanical properties and the partial molar volume of Li+ ([Formula: see text]) relative to those of the lithium anode (GLi and VLi) on plating outcomes. Within this paradigm, we explore SICs in a previously unrecognized dendrite-suppressing regime that are concomitantly 'soft', as is typical of polymer electrolytes, but feature an atypically low [Formula: see text] that is more reminiscent of 'hard' ceramics. Li plating (1 mA cm-2; T = 20 °C) mediated by these SICs is uniform, as revealed using synchrotron hard X-ray microtomography. As a result, cell cycle life is extended, even when assembled with thin Li anodes (~30 µm) and either high-voltage NMC-622 cathodes (1.44 mAh cm-2) or high-capacity sulfur cathodes (3.02 mAh cm-2).

Stability of gravity-driven free-surface flow past a deformable solid: The role of depth-dependent modulus.

The linear stability of a Newtonian liquid layer flowing down an inclined plane lined with a deformable linear elastic solid characterized by a continuously varying modulus is analyzed in this study. A low-wave-number asymptotic analysis is performed to obtain an analytical expression for the complex wavespeed which shows striking similarity with the earlier results of Sahu and Shankar [Sahu and Shankar, Phys. Rev. E 94, 013111 (2016)10.1103/PhysRevE.94.013111] for gravity-driven flow of Newtonian fluid past a solid bilayer having constant shear modulus (in each layer) lined on a rigid inclined plane. This shows that a deformable solid layer having a continuously varying shear modulus can be treated as a generalization of a system having multiple solid layers of constant shear modulus. Also, in the low-wave-number limit, we show that the stability of the free surface is governed by the value of effective shear modulus G_{eff}, and not by the detailed spatial variation of the modulus. Here the effective shear modulus (H/G_{eff}=∫_{1}^{1+H}1/[E_{0}+E[over ¯](z)]dz, where [E_{0}+E[over ¯](z)] represents the modulus gradient function) characterizes the overall modulus of the elastic solid, which is obtained by treating the continuous variation to be the limit of the arrangement of solid layers of infinitesimal thickness (each having a constant shear modulus) in a series. At finite wave numbers, we show that the free-surface and the liquid-solid interface become unstable as we increase the value of Γ, where Γ indicates the ratio of viscous stresses in the fluid to elastic stresses in the solid. When the system is analysed for different types of spatial modulus variations, we find results similar to those of Gkanis and Kumar [Gkanis and Kumar, Phys. Rev. E 73, 026307 (2006)10.1103/PhysRevE.73.026307], i.e., when we have two different configurations of the shear modulus function that have the same spatially averaged modulus, but have different values at the interface, the system is more stable for the configuration having higher shear modulus at the liquid-solid interface. In a similar manner, when we examined systems having the same shear modulus at the liquid-solid interface and same average modulus, the more stable case is the one which has a higher value of shear modulus just below the interface. Thus the use of deformable solids with a depth-dependent modulus potentially offers more control in the passive manipulation of the instabilities.

First-principles studies on phase stability, anisotropic elastic and electronic properties of Al-La binary system intermetallic compounds

The excellent comprehensive properties of Al-La binary alloy are mainly due to the stable distribution of Al-La intermetallic compounds in the microstructure. In this work, first-principle calculations have been performed to investigate the phase stability, elastic and electronic properties of eight binary Al-La intermetallic compounds. The results indicated that crystal parameters of Al-La compounds agree well with other experimental and calculated values. The calculated formation enthalpy and cohesion energies of these compounds are less than zero, which indicates that these Al-La binary compounds have good thermal stability. The result reveals that the cohesive energy of these Al-La intermetallic compounds in the binary system decreases with the increase of La content. Among these compounds, Al3La has the highest shear modulus and the strongest resistance to shear strain. The result indicates that the Al-La compounds in this study have an intrinsic sixth power correlation with the work function. It is found that Al11La3 is the most anisotropic in these Al-La binary compounds. The value at the Fermi level is not equal to zero, indicating that all these binary compounds have metal properties. Debye temperature calculation results show that Al3La has the strongest binding force between atoms of Al-La intermetallic compounds. Furthermore, the results show that these compounds have anisotropy of longitudinal and transverse sound velocity in different crystallographic directions.

The study of dynamic properties of carbonate sand through a laboratory database

Carbonate soils are located in temperate and tropical regions of the earth. This kind of soil has special mechanical properties compared with siliceous sand due to special sedimentary environment. In this paper, resonant column device is used to investigate the shear modulus and damping ratio of carbonate sand in the South China Sea at small and moderate shear strain amplitudes. At the same time, the dynamic properties of siliceous sands with the same gradation are also studied for the comparison. The influence of isotropic effective confining pressure and relative density on the dynamic characteristics of the sands is studied. The shear modulus of tested carbonate and siliceous sands increases with the increase of effective confining pressure and relative density. The influence of relative density on the shear modulus and maximum shear modulus of carbonate sand is more obvious than that of siliceous sand under identical test conditions. The damping ratio of both two sands decreases significantly with the increase of effective confining pressure, but the influence of relative density on the damping ratio is not obvious. A comparison between the dynamic characteristics of the carbonate and siliceous sand shows that carbonate sand has higher shear modulus, higher damping ratio, and faster shear stiffness degradation. Based on this study and other existing dynamic and cyclic tests data of different carbonate soils, a database of normalized shear modulus and damping ratio for carbonate soils was created, and a modified hyperbolic model was proposed for calculating the normalized shear modulus and damping ratio of carbonate soils with different calcium carbonate contents.

Interfacial viscoelasticity and aging effect on droplet formation and breakup

Interfacial rheology of interfaces stabilized by food ingredients has been studied extensively within the limits of small and slow deformations, within the linear viscoelastic regime (LVR). However, in practice, products such as foams or emulsions undergo fast and large deformations during food processes such as chewing. emulsifying, or foaming. In this study, we used capillary break-up and droplet formation to observe and quantify large and fast deformations of such interfaces, in the presence of surface viscoelasticity. We studied the inertial thinning of the liquid neck during drop formation using high-speed imaging. We tested solutions of several surface active molecules, including two low molecular weight surfactants (SDS and Tween 20), two milk proteins (β-Lactoglobulin, Bovine Serum Albumin) and the saponin Escin. Escin showed the most significant effect on the shape of the neck and neck thinning dynamics. Interfacial shear rheology measurements indicated that the unusual breakup observation of Escin solutions was related to the high viscoelastic surface shear moduli. These high moduli, and the resulting more symmetric and shorter neck shape observed for the proteins and Escin, are associated with the formation of solid-like interfacial structures. However, the presence of a viscoelastic interface did not affect the inertial thinning regime, which indicates that the solid structures were broken down locally at the area of minimum radius (Rmin), and affected only the shape outside this region. The results of this work therefore, show that interfacial measurements within the LVR are not entirely representative for fast and large deformations well beyond linearity.

Site-specific ground response analysis at a site in the affected area of the 2016 Pidie Jaya earthquake

Analytical models have demonstrated that they are able to simulate reasonably well the seismic motions at the ground level. The most widely used model is the equivalent linear approach. This equivalent linear model was used to compute the free-field response of Meureudu-Pidie Jaya, Aceh Indonesia’s soft soils during the 2016 Pidie Jaya earthquake. The model computes the ground response of horizontally layered soil deposits subjected to transient and vertically propagating shear waves through the one-dimensional soil column. Each soil layer is assumed to be homogeneous, visco-elastic and infinite in the horizontal extent. The equivalent linear estimation of soil properties is taken to express the nonlinearity of the soil’s shear modulus and damping values. These values are assumed to be a function of shear strain amplitude and determined by an iterative process that must be consistent with the level of the effective strain induced in each sub-layer. Starting with the highest shear modulus and a low damping value, the shear modulus and the damping ratio of each sub-layer are modified. The modification is based on the applicable relationship between both properties and the shear strain. The calculation is repeated until strain-compatible modulus and damping values converge within a tolerance of 1%. This research reveals the ground motions of Pidie Jaya’s soils. The results of the analysis are presented.

Uneven Coating Influences on Electrical Impedance of Quartz Crystal Microbalance

High shear modulus coating material does not provide loading effect to the Quartz Crystal Microbalance sensor. The condition is met when the coating material was glassy and the layer was homogeneous. Polystyrene is considered as a glassy coating material when used on 10MHz Quartz Crystal Microbalance. Homogeneous and compact polystyrene coatings that are glassy can be obtained using the spin coating method. The film’s rigid condition is shown by the sensor impedance value at the series resonance frequency after coating. However, using ultrasonic spray coatings, it was known that polystyrene films are formed not as homogeneous as when coated using spin coatings. We observed that Quartz Crystal Microbalance was damped by the polystyrene film when the coating film was not evenly distributed over the sensor surface, especially on the sensor surface above the electrode. The minimum impedance of the QCM sensor increased significantly. The unevenness of the coating causes the damping effect on the QCM sensor. The minimum sensor impedance before coating was less than 15 Ohms. When the polystyrene layer was uneven, we found that the impedance increased by more than 25 Ohms. The results showed that the distribution of polymer layers on the sensor surface is one of the important factors that must be considered to avoid the effect of damping on the sensor. The measurement results showed that the sensor has a negative mass effect.

Structural, mechanical, and electronic properties of P21/m-Carbon✰

The structural, mechanical, and electronic properties of P21/m-carbon were comprehensively investigated by using first principles calculations. Our calculated structure parameters are in good agreement with the previous theoretical values. P21/m-carbon consists of 10 atoms in a unit cell and is made of an exclusively sp3 hybridized bonding network. The calculated phonon spectra and elastic constant verify that P21/m-carbon is dynamically and mechanically stable at ambient pressure. The analysis of the electronic band structure reveals that P21/m-carbon is an insulator with a band gap of 5.47 eV. It has a large bulk moduli of 398 GPa and a high shear moduli of 457 GPa. Further mechanical properties demonstrate that P21/m-carbon is prone to be ductile and possesses a high Vickers hardness value of 82.3 GPa. These values show that P21/m-carbon simultaneously possesses ultra-incompressible and the superhard property. Furthermore, the X-ray diffraction spectra is also theoretically simulated to provide more structure information for future experimental observations.

Facile interfacial adhesion enabled LATP-based solid-state lithium metal battery

As a low-cost fast lithium ionic conductor with high shear modulus and ionic conductivity, Li1.3Al0.3Ti1.7(PO4)3 (LATP) is supposed to be one of the most promising ceramic electrolytes for high-energy solid-state batteries. However, the chemical reaction with lithium metal and the high interfacial impedance with solid electrodes make the ceramic electrolyte difficult to straightly apply to lithium metal batteries. Herein, a facile interfacial adhesion strategy is proposed to solve the addressed issues. The sticky polyethylene oxide (PEO) thin layer is served as interfacial adhesive to link the compact LATP ceramic electrolyte and the solid electrodes in consideration of its acceptable Li+ conducting capability and perfect compatibility with the tailored materials. Meantime, the PEO adhesive instead of PVDF binder is employed to glue the cathode components, enhancing the affinity to the PEO interlayer. As a result, the solid/solid interfacial resistance is decreased by two orders of magnitude. The solid-state Li/LATP/LiFePO4(LFP) cell with PEO adhesion is successfully activated, and exhibits steady cycling performance with high reversible capacity at the current no more than 0.5 C. As proposed interfacial adhesion strategy is simple but efficient to enable solid-state lithium metal batteries.

Crystal structure prediction of ReN2 under high pressure

Three ReN2 phases (Pbcn, C2/m and P4/mbm) are searched to be stable under different pressures by the swarm-intelligence-based CALYPSO method. Pressure-induced phase transitions from Pbcn phase to C2/m phase at 68.5 GPa and C2/m phase to P4/mbm phase at 138.8 GPa are firstly observed. The calculated results of density of state show all the three phases are metallic conductor. And elastic constant calculations confirm their mechanical stabilities. The high bulk and shear moduli of C2/m and P4/mbm phases indicate their high hardness. The total and partial electron densities of states and electron localization functions indicate that the covalent bonding of Re–N in ReN2 makes great contributions to the structural stability and high hardness.