Quasi In-Situ EBSD Analysis of Twinning-Detwinning and Slip Behaviors in Textured AZ31 Magnesium Alloy Subjected to Compressive-Tensile Loading

Twinning and detwinning behavior, together with slip behavior, are studied in a textured AZ31 magnesium alloy under compressive and tensile strains along the rolling direction (RD) after each interrupted mechanical test via quasi in-situ electron backscattered diffraction technique. The results show that twinning firstly takes place under the compressive strain along the RD. With the increasing compressive strain, {1012} tensile twins firstly nucleate, then propagate, and finally thicken. While under a reversed tensile strain along the RD, detwinning occurs. No nucleation happens during detwinning. Thus, tensile twins can detwin at lower tensile strain, followed by thinning, shortening, and vanishing. Slips are also activated to accommodate the plastic deformation. In the matrix, prismatic slip can only dominate at relatively high strains. Otherwise, basal slip dominates. While in the twins, prismatic slip can activate at lower strains, which is ascribed to the texture reorientation

Multiphase Layered Transition Metal Oxide Positive Electrodes for Sodium Ion Batteries

Multiphase layered transition metal oxides (LTMOs) for sodium ion battery (SIB) positive electrodes with phase interfaces across multiple length scales are a promising avenue toward practical, high-performance SIBs. Combinations of phases can complement each other\u27s strengths and mitigate their weaknesses if their interfaces are carefully controlled. Intra- and interparticle phase interactions from nanoscale to macroscale must be carefully tuned to generate distinct effects on properties and performance. An informed design strategy must be paired with relevant synthesis techniques and complemented by spatially resolved characterization tools to manipulate different length scales and interfaces. This review examines the design, synthesis, and characterization strategies that have been demonstrated for the preparation of heterogeneous, multiphasic LTMOs with phase interfaces across varied length scales

Heterostructure Engineering in Electrode Materials for Sodium-Ion Batteries: Recent Progress and Perspectives

Sodium-ion batteries (SIBs) have stepped into the spotlight as a promising alternative to lithium-ion batteries for large-scale energy storage systems. However, SIB electrode materials, in general, have inferior performance than their lithium counterparts because Na+ is larger and heavier than Li+. Heterostructure engineering is a promising strategy to overcome this intrinsic limitation and achieve practical SIBs. We provide a brief review of recent progress in heterostructure engineering of electrode materials and research on how the phase interface influences Na+ storage and transport properties. Efficient strategies for the design and fabrication of heterostructures (in situ methods) are discussed, with a focus on the heterostructure formation mechanism. The heterostructure\u27s influence on Na+ storage and transport properties arises primarily from local distortions of the structure and chemomechanical coupling at the phase interface, which may accelerate ion/electron diffusion, create additional active sites, and bolster structural stability. Finally, we offer our perspectives on the existing challenges, knowledge gaps, and opportunities for the advancement of heterostructure engineering as a means to develop practical, high-performance sodium-ion batteries

Elucidating the Synergic Effect in Nanoscale MoS\u3csub\u3e2\u3c/sub\u3e/TiO\u3csub\u3e2\u3c/sub\u3e Heterointerface for Na-Ion Storage

Interface engineering in electrode materials is an attractive strategy for enhancing charge storage, enabling fast kinetics, and improving cycling stability for energy storage systems. Nevertheless, the performance improvement is usually ambiguously ascribed to the “synergetic effect”, the fundamental understanding toward the effect of the interface at molecular level in composite materials remains elusive. In this work, a well-defined nanoscale MoS2/TiO2 interface is rationally designed by immobilizing TiO2 nanocrystals on MoS2 nanosheets. The role of heterostructure interface between TiO2 and MoS2 by operando synchrotron X-ray diffraction (sXRD), solid-state nuclear magnetic resonance, and density functional theory calculations is investigated. It is found that the existence of a hetero-interfacial electric field can promote charge transfer kinetics. Based on operando sXRD, it is revealed that the heterostructure follows a solid-solution reaction mechanism with small volume changes during cycling. As such, the electrode demonstrates ultrafast Na+ ions storage of 300 mAh g−1 at 10 A g−1 and excellent reversible capacity of 540 mAh g−1 at 0.2 A g−1. This work provides significant insights into understanding of heterostructure interface at molecular level, which suggests new strategies for creating unconventional nanocomposite electrode materials for energy storage systems

Electrochemically Induced Amorphous-to-Rock-Salt Phase Transformation in Niobium Oxide Electrode for Li-Ion Batteries

Intercalation-type metal oxides are promising negative electrode materials for safe rechargeable lithium-ion batteries due to the reduced risk of Li plating at low voltages. Nevertheless, their lower energy and power density along with cycling instability remain bottlenecks for their implementation, especially for fast-charging applications. Here, we report a nanostructured rock-salt Nb2O5 electrode formed through an amorphous-to-crystalline transformation during repeated electrochemical cycling with Li+. This electrode can reversibly cycle three lithiums per Nb2O5, corresponding to a capacity of 269 mAh g−1 at 20 mA g−1, and retains a capacity of 191 mAh g−1 at a high rate of 1 A g−1. It exhibits superb cycling stability with a capacity of 225 mAh g−1 at 200 mA g−1 for 400 cycles, and a Coulombic efficiency of 99.93%. We attribute the enhanced performance to the cubic rock-salt framework, which promotes low-energy migration paths. Our work suggests that inducing crystallization of amorphous nanomaterials through electrochemical cycling is a promising avenue for creating unconventional high-performance metal oxide electrode materials

The Sihailongwan Maar Lake, northeastern China as a candidate Global Boundary Stratotype Section and Point for the Anthropocene Series

Sihailongwan Maar Lake, located in Northeast China, is a candidate Global boundary Stratotype Section and Point (GSSP) for demarcation of the Anthropocene. The lake’s varved sediments are formed by alternating allogenic atmospheric inputs and authigenic lake processes and store a record of environmental and human impacts at a continental-global scale. Varve counting and radiometric dating provided a precise annual-resolution sediment chronology for the site. Time series records of radioactive (239,240Pu, 129I and soot 14C), chemical (spheroidal carbonaceous particles, polycyclic aromatic hydrocarbons, soot, heavy metals, δ13C, etc), physical (magnetic susceptibility and grayscale) and biological (environmental DNA) indicators all show rapid changes in the mid-20th century, coincident with clear lithological changes of the sediments. Statistical analyses of these proxies show a tipping point in 1954 CE. 239,240Pu activities follow a typical unimodal globally-distributed profile, and are proposed as the primary marker for the Anthropocene. A rapid increase in 239,240Pu activities at 88 mm depth in core SHLW21-Fr-13 (1953 CE) is synchronous with rapid changes of other anthropogenic proxies and the Great Acceleration, marking the onset of the Anthropocene. The results indicate that Sihailongwan Maar Lake is an ideal site for the Anthropocene GSSP

\u3cem\u3eAb Initio\u3c/em\u3e Investigations on Metal Ion Pre-Intercalation Strategy of Layered V\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e5\u3c/sub\u3e Cathode for Magnesium-Ion Batteries

Metal ions pre-intercalated layered structure materials are considered as potential high performance cathodes for Mg-ion batteries (MIBs). Herein, metal ions pre-intercalation strategy of layered cathode for MIBs by using Li, Na, Al pre-intercalated V2O5 cathode as a carrier has been investigated and proposed based on first principle calculations. The pre-intercalation process is energetically favorable and metal ion pre-intercalation improves the electronic conductivity of V2O5. The bondings of Li-V2O5, Na-V2O5 and Al-V2O5 all exhibit ionic characters, and the interaction between Al ion and V2O5 is the strongest. The interlayer distance expansion of Na pre-intercalated V2O5 is more trivial than that of Li, Al pre-intercalated V2O5. The open circuit voltage of the V2O5 cathode is dropped by pre-intercalated metal ions, and the voltage of Li and Na pre-intercalated V2O5 is higher than that of Al pre-intercalated V2O5. The diffusion barriers of Mg in the V2O5 matrix are reduced by pre-intercalation. Overall, metal ion pre-intercalation with a large atomic radius and small atomic charges holds great potentials to expand interlayer distance, enhance electronic conductivity, maintain high discharge voltage and improve diffusion ability of layered cathode. We hope our work could provide a significant guidance to the practical design of layered cathodes for MIBs

Roles of Twinning and \u3c a \u3e Slipping in Tensile Anisotropy of Rolled Mg-3Al-Zn Alloy

In this work, the {101‾2} tensile twinning and \u3c a \u3e type slipping dependence of plastic anisotropy in the rolled Mg-3Al-Zn alloy are studied by using tensile tests along two orthogonal directions, the rolling direction and normal direction. The results show that the initial basal texture of the material influences the activities of twinning and slips, leading to anisotropic deformation. During tension along the rolling direction, the deformation is dominated by basal and prismatic \u3c a \u3e slips. During tension along the normal direction, the deformation is accommodated through tensile twinning and basal \u3c a \u3e slip; prismatic \u3c a \u3e slip is hard to active in matrix grains, but it plays an important role in twined regions