Monolayer transition metal dichalcogenides (TMDs) show promising prospects for valleytronics applications, yet their atomic thinness makes valley polarization highly susceptible to defects. Nevertheless, the microscopic mechanism underlying the influence of defects formed during growth on the valley polarization dynamics of TMDs is still poorly understood. Here, we elucidate the microscopic mechanisms of defect-mediated valley depolarization in as-grown WS2 monolayers by integrating scanning tunneling microscopy/spectroscopy with helicity-resolved ultrafast transient reflection spectroscopy. We identify oxygen-substituting sulfur (OS) and molybdenum-substituting tungsten (MoW) as the predominant defects. OS defects substantially reduce the energy separation between the valence-band maxima at the K and Gamma points (Delta Gamma K) to similar to 146 meV, thereby activating a hole K -> Gamma -> K ' intervalley scattering channel at room temperature and shortening the hole valley polarization lifetime to the femtosecond regime. Moreover, both OS and MoW defects act as spin-conserving electron intervalley scattering centers, enhancing the electron intervalley scattering rate. These defect-induced scattering pathways synergistically accelerate valley depolarization in WS2. Our findings offer important insights for defect engineering toward practical valleytronic applications in monolayer TMDs.

Ferromagnetic single atom doped BP monolayers are proposed as electrocatalysts for lithium-sulfur batteries. Based on first-principles calculations, it is found that Fe-BP and Ni-BP monolayers exhibit higher electronic conductivity, and their adsorption ability for lithium polysulfides are significantly enhanced compared to the bare BP monolayer, which could effectively suppress the shuttling effect. Besides, the Fe-BP monolayer shows the lowest energy barrier for both sulfur reduction reaction and Li2S decomposition, with a low Li+ diffusion energy barrier of 0.25 eV. Based on these results, Fe-BP monolayer is suggested as a promising single-atom electrocatalyst for sulfur redox reactions which will show fast charge-discharge kinetics and long cycle life in lithiumsulfur batteries.

It has attracted tremendous attention for replacing petroleum-based carbon black or mineral fillers with renewable, biology-based and low-cost cellulose. However, the reinforcing effect of cellulose, especially at the microscale, is still a great challenge in the polymer industry. In this work, a feasible surface modification method for microcrystalline cellulose powder (MCC) in all solid states is proposed by using rubber accelerators N-cyclohexyl benzothiazole-2-sulphenamidee (CBS) and 2,2'dibenzothiazoledisulfide (DM). These accelerators not only accelerate the sulfur crosslink of nitrile butadiene rubber (NBR), but also graft to rubber molecular chains and form hydrogen bonds with MCC, resulting in good interfacial interaction and good dispersion of MCC in the NBR matrix. As a consequence, the tensile strength and elongation at break of NBR/10MCC reach up to 20.12 MPa and 511%, respectively, which are the highest values of NBR/MCC or cellulose nanocrystals (CNCs) composites we can find in the world and are comparable to those of carbon black or mineral fillers. This provides a more effective and environmentally friendly way of using MCC or CNCs in the polymer industry.Highlights Microcrystalline cellulose powder can reinforce NBR. Hydrogen bonds have been established between accelerators and MCC. The tensile strength of NBR/10MCC composite reaches 20 MPa. The reinforcing mechanism is ascribed to the immobilized rubber layer.

Constructing a current collector is a promising approach to modifying the zinc anode. However, most collectors exhibit top zinc deposition patterns, leading to unsatisfactory zinc utilization and instability. To address this issue, we have developed a new sandwich deposition approach in which a boron nitride layer (BN layer) is applied onto Cu foils as the current collector, which allows us to achieve the sandwich-structured anode (BN-ZnCu). Through experimental characterization and theoretical calculations, the deposition mechanisms of Zn2+ have been explored and verified. The insulating BN layer, the upper layer of the anode, acts as the protective barrier of deposited zinc and accelerates the transmission of zinc ions. The zincophilic Cu substrate, the bottom layer of the anode, promotes Zn deposition without dendrites. Under the synergistic effect of the BN layer and substrate, the sandwich-structured anode enables superior reversibility with 99.49 % coulombic efficiency over 700 cycles and realizes 66.7 % zinc utilization at 4 mAh cm-2. Moreover, the assembled BN-Zn-Cu||CNT/MnO2 cells display high stability with an average fading of 0.06 % per cycle for 600 cycles. Our work verifies the feasibility of sandwich-structured anodes in enhancing the performance of aqueous zinc-ion batteries, providing an innovative idea for the structural design of metal anodes.

Li1.18Ni0.15Co0.15Mn0.52O2, a lithium-rich manganese oxygen cathode material , was successfully generated with the sol-gel methods, then we modified it using Ce4+ and obtained a new Li1.18Ni0.15Co0.15Mn0.52-xCexO2 (x=0, 0.01) material. scanning electron microscopy (SEM) and X-ray diffraction (XRD) testing were used to analysis the materials, and electrochemical properties were explored by constant current charge/discharge and cyclic voltammetry (CV) tests. Test results showed that cerium-doped cathode material maintained its lamellar structure without significant changes in microscopic morphology. It was also found that the capacity retention rate of the doped materials was 89% after 50 cycles at 0.2C, while that of the undoped materials were 77%. In addition, the discharge capacity of the doped materials at 0.2, 0.5, 1, 2.5, 5 and 10C is higher than that of the undoped materials. The above results show that Ce4+ doping can improve the Electrochemical performance of Li-rich Mn-based cathode materials .

High-entropy materials are new-fashioned electrocatalysts due to their interesting "cocktail effect". However, it is still a great challenge to synthesize single-crystal high-entropy nanomaterials such as (oxy)hydroxides due to the different crystal growth mode for different elements. Herein, we design a dynamic crystal growth strategy by multi-cation exchange to fabricate single-crystal high-entropy (oxy)hydroxides nanosheets. Nanoporous morphology can be achieved by incorporating Al ion into the multicomponent (oxy)hydroxides system after a reversible Al insertion-dissolution process. When adopted as potential electrocatalysts for oxygen evolution reaction (OER), we find that the seven-component ZnVNiCoFeAlRu-OHs single-crystal nanoporous nanosheets display a significantly improved OER performance with a low overpotential of 229 mV at 10 mA cm-2 and a shallow Tafel slope of 39.3 mV dec � 1. Both XPS and DFT calculation reveal that Ru acted an electron dedicator could effectively moderate the overall electronic structures for better OER performance. This work develops an entropy and enthalpy driven multi-cation exchange strategy for synthesizing a library of single-crystal highentropy (oxy)hydroxides for various applications.

The conflict between strength and toughness of plastic/rubber blends is still a great challenge in the world, especially for incompatible plastic/rubber blends. Here, we prepared carboxylated styrene-butadiene rubber latex (XSBR) and polyacrylamide (PAM) composites by a solution mixing method. FTIR and XPS results show a weak hydrogen bond between carboxyl groups of XSBR and amino groups of PAM, which is not enough to enhance the miscibility of XSBR and PAM. As a result, large parts of PAM precipitate to construct a macro continuous phase. A small part of PAM evolves from nanowires to a three-dimension nano network owing to the hydrogen bond inductive effect. Consequently, a leaf vein bionic nano-micro structure is proposed to interpret the great reinforcement effect in Young's modulus (112 times), tensile strength (almost 6 times) as compared to 5XSBR/5PAM with pure XSBR, which is almost equal to the mechanical properties of pure PAM. Meanwhile, the elongation at break and toughness of 5XSBR/5PAM is almost 1567% and 3370% of pure PAM, respectively. This may provide a new road to solve the conflict between strength and toughness.

Si@TiN composites show excellent electrochemical properties and suppressed volume expansion compared with pure silicon nanoparticles (Si NPs).

Bimetallic transition metal chalcogenides (TMCs) materials have emerged as attractive anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of the high intrinsic electronic conductivity, rich redox sites and unique reaction mechanism. In this work, we report the synthesis and electrochemical properties of a novel bimetallic TMCs material CuSbSe2. The as-prepared anode delivers a high reversible capacity of 545.6 mA h g(-1) for SIBs and 592.6 mA h g(-1) for LIBs at a current density of 0.2 A g(-1), and an excellent rate capability of 425.9 mA h g(-1) at 20 A g(-1) for SIBs and 226.0 mA h g(-1) at 10 A g(-1) for LIBs without any common-used surface modification or carbonaceous compositing. In addition, ex situ X-ray diffraction (XRD) and High-resolution transmission electron microscopy (HRTEM) reveal a combined conversion-alloying reaction mechanism of LIBs and NIBs. Our findings suggest bimetallic CuSbSe2 could be a potential anode material for both SIBs and LIBs.

Valleytronics is proposed to explore a new approach for information storage using valley degrees of freedom. In this work, the electronic structure, spin-valley splitting and magnetic anisotropy (MA) of two-dimensional (2D) 2H-VS2/h-VN magnetic van der Waals (vdW) heterostructure are investigated systematically by first-principles calculations. The results show that the considerable spin splitting of 364.7 meV and 543.7 meV are observed at the K and K' valleys, respectively, generating an intrinsic valley splitting of 68.9 meV in the valence band for the 2H-VS2/h-VN heterostructure, which corresponds to an effective Zeeman magnetic field of 774 T based on the k.p model. The valley splitting of 2H-VS2 is well preserved in the heterostructure and can be further adjusted by altering stacking patterns, in-plane strain and interfacial distance due to the interfacial orbital hybridization. Compared with the pristine 2H-VS2 monolayer, the 2H-VS2 of heterostructure still exhibits the in-plane MA, which mainly originates from the positive contribution of the matrix element difference between the V d(xy )and d(x)(2)-(2)(y) orbitals. With the increase of strain from -2% to 3%, the orientation of easy magnetization axis is transformed from in-plane to out of plane. These results suggest that the 2H-VS2/h-VN heterostructure is a potential candidate in further valleytronics and spintronics.

全面推进课程思政建设,将立德树人根本任务贯穿于教育教学全过程,是当前高校进行专业课程教学改革的重中之重.本文以仪器分析课程为例,基于育人和育才相统一、理论性和政治性相统一以及隐性教育和显性教育相统一的教育原则,充分探索和挖掘本课程的思政内涵和实现路径,大力推动高等教育体系由知识传授向价值塑造和能力培育转化.

Many efforts were made to modify cathode materials for K-ion batteries to improve their performance. However, the improvements are not so significant. Herein, we show that the performance of host materials are limited by metal K counter electrode, which leads to underestimation of materials. With a potassiated alloy/carbon composite counter electrode, the Prussian blue analogue cathode can show outstanding rate capability at 5000 mA g(-1) and operate 1000 cycles without capacity fading. Besides, when the anode utilization increased to 72.7%, the battery parameters, such as lifespan, energy and power density, were also promising. This work offers a new perspective for both fundamental and practical research of K-ion batteries. (C) 2021 Elsevier Ltd. All rights reserved.

The instability and low activity of WO3 is the hot-topic for photoelectrochemical (PEC) water splitting, which is decreased by a sluggish interfacial kinetics and incomplete water oxidation. Aiming at such issues, we designed a ternary WO3/RG/Ni:FeOOH photoanode, which exhibits 2.05 times larger photocurrent (1.32 mA cm(-2)) than the WO(3)NFs in 0.5 M Na2SO4 electrolyte solution, accompanied with 83 mV cathodic shift of onset potential. These results demonstrates PEC response can occurs only in Ni:FeOOH but not FeOOH. Therefore, Ni:FeOOH acting as bi-functional modifier, can not only increase light absorption but also promote charge transfer process by forming p-n heterojunction with the WO(3)NFs. Besides, RGO forming a continuously conducting network can further improve charge separation process. Owing to their synergistic effects, the Faradaic efficiency and stability are both improved compared to its counterparts and the bare WO(3)NFs. This work may inspire the PEC application in other co-catalyst decorated systems.

Reversible aqueous zinc-ion batteries (ZIBs) have great potential for large-scale energy storage owing to their low cost and safety. However, the lack of long-lifetime positive materials severely restricts the development of ZIBs. Herein, we report NaV6O15 microflowers as a cathode material for ZIBs with excellent electrochemical performance, including a high specific capacity of ∼300 mA h g-1 at 100 mA g-1 and 141 mA h g-1 maintained after 2000 cycles at 5 A g-1 with a capacity retention of ∼107%. The high diffusion coefficient and stable tunneled structure of NaV6O15 facilitate Zn2+ intercalation/extraction and long-term cycle stability.

We have synthesized a series of Li1+x(Ni0.5Mn0.5)1-xO2 (LNMO) materials to study the influence of excess lithium ions on the structure and electrochemical behaviors of nickel-manganese-based layered compounds. The increasing content of Li+ ions in the transition-metal (TM) layer leads to the departure of the follower-like clusters to Ni-rich and Mn-rich clusters. The Ni2+ ions in the Li layer couple with adjacent transition-metal ions via strong 180° exchange interactions and moderate the local structure, which leads to magnetic clusters with finite size. Electrochemical performance shows that appropriate Ni2+ ions could improve the cycle stability without decreasing the rate capability. Among them, Li1.1Ni0.45Mn0.45O2 shows a rate capability of 76 mAh g-1 at 1000 mA g-1 and a lifespan of 300 cycles at 200 mA g-1. This work shows that structure moderation has an essential impact on its electrochemical performance. Besides this, the crystal and magnetic combined methods we use could offer a better way of studying cathode materials.

Fly ash (FA) is a solid waste from coal-fired power stations, which can cause serious environmental problems without further treatment. Although FA has been successfully utilized in building materials, the reuse of FA in the polymer industry has remained a great challenge due to the difficulty in organically-modifying the smooth surfaces of FA particles. In this study, by introducing tannic acid (TA, a naturally occurring plant polyphenol), nitrile butadiene rubber (NBR)/FA/TA composites were prepared via a simple environment-friendly method. The properties of the products were thoroughly investigated and experiments showed that the TA incorporation into NBR/FA composites resulted in formation of hydrogen bonds among NBR, FA, and TA, leading to dramatic improvement in surface adhesion between NBR and FA. As a consequence, the tensile strength of the NBR/20FA/0.4 TA composite was similar to 110.4% larger than that of NBR/20FA composite, thus opening a new route to large-scale practical use of FA in the polymer industry.

A modified gel polymer electrolyte (GPE) with boron nitride (BN) additive was designed to boost the electrochemical performance of rechargeable lithium metal battery, which consists of Li-rich layered cathode and possesses a high energy density. BN, electron insulator and ion conductor, has excellent thermodynamic and electrochemical stability. BN particles were well dispersed in polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) polymer matrices and thus substantially enhanced the electrochemical and physical properties of the GPEs. With only 0.5 wt% BN additive, it remarkably improved the mechanical modulus and ionic conductivity (to 4.1 x 10(-4) S.cm(-2)) of GPEs, which was beneficial for suppressing lithium dendrite formation and fast ion transportation, respectively, thereby enabling high-performance lithium metal batteries with ultra-long cycle life and high safety at ambient temperature (25 degrees C) and high temperature (55 degrees C). (C) 2019 Elsevier B.V. All rights reserved.

Rechargeable aqueous zinc ion batteries (ZIBs), owing to their low-cost zinc metal, high safety and nontoxic aqueous electrolyte, have the potential to accelerate the development of large-scale energy storage applications. However, the desired development is significantly restricted by cathode materials, which are hampered by the intense charge repulsion of bivalent Zn2+. Herein, the as-prepared VO2(A) hollow spheres via a feasible hydrothermal reaction exhibit superior zinc ion storage performance, large reversible capacity of 357 mA h g-1 at 0.1 A g-1, high rate capability of 165 mA h g-1 at 10 A g-1 and good cycling stability with a capacity retention of 76% over 500 cycles at 5 A g-1. Our study not only provides the possibility of the practical application of ZIBs, but also brings a new prospect of designing high-performance cathode materials.

The electrochemical properties of a Li-excess Li1.18Ni0.15Co0.15Mn0.52O2 cathode material in a lithium difluoro (oxalate) borate (LiDFOB, 20 wt%) and lithium hexafluoride phosphate (LiPF6, 80 wt%) dual-salt electrolyte are investigated. The use of a dual-salt electrolyte significantly improves the material's electrochemical performance, especially at elevated temperature. The capacity retention of the electrode increases from 24% to 92% after charging-discharging at 55 °C for 100 cycles. Spectroscopic analysis demonstrates that LiDFOB salt suppressed Mn2+ dissolution into the electrolyte and improved the electrode's electrochemical kinetic properties. In addition, the thermal safety of the fully-charged electrode is improved by the dual-salt electrolyte, which results in high onset temperature and reduces thermal release.

Li2CO3-passivated Li3N with high stability is prepared by aging Li3N powder in dry air, and is then used as an electrode additive for a Li(Li0.18Ni0.15Co0.15Mn0.52)O-2 (LLMO) cathode material. The material shows a large irreversible capacity of 800mAhg(-1) during the first charge, with the formation of a Li2N intermediate product. Acting as a Li+ sacrificial salt for a LLMO(+)/graphite(-) Li-ion battery, 2wt% Li3N results in a 10% increase in discharge capacity. The Li2N intermediate product reacts with the electrolyte, forming a uniform and regular surface film on the cathode. Moreover, chemical bonding between LLMO and N improves the electrode stability, resulting in excellent electrochemical performance.