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Abstract Li4Ti5O12 (LTO) is known for its zero-strain characteristic in electrochemical applications, making it a suitable material for fast-charging applications. Here, we systematically studied the quasi-equilibrium and non-equilibrium lithium-ion transportation kinetics in LTO thin-film electrodes, across a range of scales from the crystal lattice to the microstructured electrodes. At the crystal lattice scale, during the non-equilibrium lithiation process, lithium ions are dispersedly embedded into the 16c position, resulting in more 8a → 16c migration compared with the quasi-equilibrium lithiation, and forming numerous fast lithium diffusion channels inside the LTO lattice. At the microstructural electrode scale, optical spectrum characterizations supported the “nano-filaments” lithiation model in polycrystalline LTO thin-film electrodes during the lithiation process. Our results reveal the patterns of lithium migration and distribution within the LTO thin film electrode under the non-equilibrium and quasi-equilibrium lithiation process, offering profound insights into the potential optimization strategies for enhancing the performance of fast-charging thin film batteries.

Understanding the evolution of the solid electrolyte-electrode interface is currently one of the most challenging obstacles in the development of solid-state batteries (SSBs). Here, we develop an X-ray Photoelectron Spectroscopy (XPS) that allows for operando measurement during cycling. Based on theoretical analysis and the modulated electrode and detector co-grounding mode, the displacement of binding energy can be correlated with the surface electrostatic potential of the material, revealing the charge distribution and composition evolution of the space charge layer between the cathode and the electrolyte. In the investigation of typical LiCoO2 (LCO)/Li6PS5Cl (LPSC)/Li–In batteries, we observed the static potential difference and oxidative decomposition between LPSC and LCO, and the effectiveness of the LiNbO3 coating in reducing potential difference and inhibiting the diffusion of Co and oxidation of S species. Furthermore, our study also revealed that the potential drop between LiNi0·8Co0·1Mn0·1O2 and LPSC is smaller than that of LCO, whilst that between Li3InCl6 and LCO remains near zero. The proposed operando XPS method offers a novel approach for real-time monitoring of interface potential and species formation, providing rational guidance for the interface engineering in SSBs.

The weak interlaminar properties severely hinder the high-property applications of carbon fiber (CF) reinforced thermoplastic composites. Here, interlaminar properties were significantly enhanced by introducing carbon nanotube (CNT) decorated polyether ether ketone (PEEK) films into the interlayer. PEEK films decorated with different CNT contents were fabricated by the spraying and thermoforming processes. Tensile test results show that the films with a CNT surface density of 45 mg/m2 exhibit superior tensile strength and Young's modulus due to the higher crystallinity and larger crystalline size. The introduction of this modified film into unidirectional CF reinforced PEEK laminates leads to an increase by 101% to 1.67 kJ/m2 in interlaminar fracture toughness, while the interlaminar shear strength is retained. Fractographic analysis reveals that the increase in interlayer resin content and crack path deflection are primary factors contributing to interlaminar toughening. Molecular dynamics simulation demonstrates that incorporating CNT in the interlayer resin significantly improved the interfacial bonding strength between fiber and resin, thus resulting in crack path deflection.

Spin gapless semiconductor (SGS) presents abundant electric and magnetic properties and is highly sensitive to external factors, such as current, electric field, magnetic field, and stress. This paper reports on a PbPd0.9Co0.1O2/PMNPT(001) laminate thin film with the “SGS/ferroelectrics” structure, which exhibits significant current-induced resistance (I-ER) effect. More importantly, the colossal static electric-field-induced resistance (E-ER) effect in such a laminate film was observed for the first time. The introduction of lattice defects (Pb vacancies) induces a local electric field, electron spin ordering state, and ferroelectric polarization field effect to explain the excellent physical properties. The reported laminate thin film composite exhibits promising application potential in spintronic devices, composite sensor units, storage systems, and other low-energy semiconductor electronic device fields. This work proposes an alternative way to investigate the novel properties for spin gapless semiconductors and expand the research fields of multi-field modulation effect in magnetoelectric composites.

Abstract Relieving the stress or strain associated with volume change is highly desirable for high‐performance SiOx anodes in terms of stable solid electrolyte interphase (SEI)‐film growth. Herein, a Si‐valence gradient is optimized in SiOx composites to circumvent the large volume strain accompanied by lithium insertion/extraction. SiOx@C annealed at 850°C has a gentle Si‐valence gradient along the radial direction and excellent electrochemical performances, delivering a high capacity of 506.9 mAh g−1 at 1.0 A g−1 with a high Coulombic efficiency of ~99.8% over 400 cycles. Combined with the theoretical prediction, the obtained results indicate that the gentle Si‐valence gradient in SiOx@C is useful for suppressing plastic deformation and maintaining the inner connection integrity within the SiOx@C particle. Moreover, a gentle Si‐valence gradient is expected to form a stress gradient and affect the distribution of dangling bonds, resulting in local stress relief during the lithiation/delithiation process and enhanced Li‐ion kinetic diffusion. Furthermore, the lowest interfacial stress variation ensures a stable SEI film at the interface and consequently increases cycling stability. Therefore, rational design of a Si‐valence gradient in SiOx can provide further insights into achieving high‐performance SiOx anodes with large‐scale production.

Stretching is the most important way of forming polymer films, and the mechanism of stretch-induced structural evolution is a long-standing fundamental issue in the stretching process of polymer films. Current methods are limited in sampling frequency or transparent materials and difficult to in situ measure the molecular chain structure evolution. In this study, we proposed a new principle for measuring the stretching process of polymer materials based on dielectric anisotropy. Firstly, the strain-dielectric anisotropy linear relation during small elastic deformation was found, and an extremely small strain (∼0.1%) can be measured with a high sampling frequency (∼8.3 Hz). Then, the molecular chain orientation-induced dielectric anisotropy for the underlying mechanism was confirmed by molecular dynamics simulations and in situ polarized Raman spectroscopy experiments. The proposed method was successfully applied in measuring tube compliance and dynamic health monitoring by measuring small elastic strain accurately, exhibiting the potential for wide applications.

With the popularization of small batch production, the main cutting method for sheet metal parts has changed. Laser cutting has become the main production method for coil material cutting. Developing an irregular part nesting method for the continuous cutting of coil material is urgent. Based on the coil material cutting process, this paper proposes an intelligent approach for the unit nesting problem of coil material. Firstly, a unit nesting model of coil material was constructed. Secondly, an intelligent approach using an improved marine predator algorithm was used to solve this model. In solving the model, the minimum nesting unit was continuously updated by changing the position, angle, and quantity of the nesting parts. Thirdly, the geometric characteristics of this minimum nesting unit were extracted. Finally, the nesting units for production were obtained using a single row or opposite row of the minimum nesting unit. The computational results and comparison prove that the presented approach is feasible and effective in improving material utilization, reducing production costs, and meeting the requirements of the production site.

The moiré pattern restricts the electronic states of transition metal bilayers, thus extending the concept of the magic angle found in twisted bilayer graphene to semiconductors. Here, we have studied the electronic structure of the twisted bilayer WTe2 using first-principle calculations. Our result shows that a twist significantly changes the band structure, resulting in the bandgap engineering when the twisted bilayer of WTe2 is turning to a specific angle. The electronic structure is changed by the change of the twist angle. Interestingly, a semiconductor-to-metal phase transition is found at a twist angle of 15°. Our results provide a reference for the regulation of two-dimensional band structures. These results are important for understanding the electronic structure of twisted systems and for future applications in electronic devices.

The overmolding for thermoplastic composites is an integrated process that can manufacture multilayer parts with complex structures. However, the interfacial bonding strength between layers manufactured by different processes is weak. Here we study how material and process parameters affect the fiber pinning effect and thereby influence the interface binding strength of overmolded bilayer parts. The bilayer parts were prepared by overmolding the short-carbon-fiber-reinforced polyether-ether-ketone (SCF/PEEK) onto the hot-pressed woven-CF/PEEK (WCF/PEEK) laminates. An analytical model showed that the fiber pinning effect was dominated by the fiber content (Cf), interfacial temperature (Ti) and fiber orientation (αxx). The experimental results showed that a 32% increase in interlaminar shear strength (ILSS) of bilayer parts was achieved by regulating material and process parameters and optimizing the fiber pinning effect. The microstructural characterization shows that the Ti dominates the degree of resin fusion near the interface and thereby affects the fiber pinning depth indirectly. The Cf not only changes the amount of pinned fiber, but also affects αxx, which was confirmed by nano-CT scan.

Electronic structures of non-twisted and twisted WTe2/WSe2 heterojunction bilayers were investigated using first-principles calculations. Our results show that, for the twisted WTe2/WSe2 heterojunction bilayer, the bandgaps are all direct bandgaps, and the bandgap (K–K) increases significantly when the twist angle is from 0° to 10°. However, when the twist angle is from 11° to 14.2°, the bandgaps are all indirect bandgaps and the bandgap (G–K) significantly reduces. The band structure of the twisted WTe2/WSe2 heterojunction bilayer differs significantly from that of the non-twisted. Twisted WTe2/WSe2 heterojunction bilayers can be seen as a direct bandgap to an indirect bandgap conversion when turned to a certain angle. Interestingly, the bandgap of the WTe2/WSe2 heterojunction bilayer is very sensitive to the change in the twist angle. For example, when the twist angle is 10.5°, a maximum bandgap will appear. However, the minimum bandgap is 0.041 eV at 14.2°. Our findings have important guidance for device tuning of two-dimensional heterojunction materials.

Abstract Eliminating the uncontrolled growth of Li dendrite inside solid electrolytes is a critical tactic for the performance improvement of all‐solid‐state Li batteries (ASSLBs). Herein, a strategy to swallow and anchor Li dendrites by filling Si nanoparticles into the solid electrolytes by the lithiation effect with Li dendrites is proposed. It is found that Si nanoparticles can lithiate with the adjacent Li dendrites which have a strong electron transport ability. Such effect can inhibit the formation of Li dendrites at the interface of Li anode, and also swallow the tip Li inside the solid electrolytes, and thus inhibiting its longitudinal growth and avoiding the solid electrolyte puncturing. As a proof of concept, a novel sandwich‐structure solid electrolyte of Li6.7La3Zr2Al0.1O12 (LLZA)‐PEO/Si‐PEO electrolyte/ (LLZA)‐PEO with asymmetrical structure is first constructed and demonstrated stable Li plating/stripping over 1800 h and remarkably improved cycling stability in Li/LiFePO4 cells with a reversible capacity of 111.9 mAh g−1 at 1 C after 150 cycles. The proof of lithiation of Si‐PEO electrolyte in the interlayer is also verified. Furthermore, the pouch cell thus prepared exhibits comparable cyclic stability and is allowable for folding and cutting, suggesting its promising application in ASSLBs by this simple and efficient strategy.

Using devices such as unified power quality conditioners (UPQCs) in distribution networks seems essential for higher electricity quality. Moreover, distribution network reconfiguration is a suitable model for improving network characteristics, including loss reduction and voltage increase for distribution networks, and is widely used in this era. Here, the study discusses the rechanging of distribution networks for UPQC via proposing an appropriate model for it. In addition to the optimum structure of distribution networks, the most appropriate branch where UPQC must be located and the most appropriate reactive power size with which series and shunt filters must be injected into the grid are determined. The simulations have been applied on two 69- and 84-standard-bus networks. The results of the simulations indicate much power loss reduction and much voltage increase in the presence of UPQC compensators.

Defects profoundly affect the magnetic, electronic structure and topological behaviour of intrinsic magnetic topological insulators. Here, we investigate the magnetic, structural stability and topological properties of different Te atomic sites in the intrinsic magnetic topological insulator FeBi _2 Te _4 with Se substitution of the FM- z magnetic order. When Se replaces the outermost site of the septuple layer (the Te atomic layer connected by van der Waals bonds), the Se–Bi bond length formed with its nearest neighbour Bi is drastically shortened and the lattice constant and volume contract accordingly. We speculate that this defect-induced chemical bond enhancement is related to the strong electronegativity of Se over Te. In contrast, the system has lower formation energy, a more stable structure, and enhanced magnetic moment when Se replaces the Te atomic layer inside the septuple layer. Also, we reveal a variety of topological phase transitions due to substitution defects. FeBi _2 Te _4 is considered to belong to the $z_{2} \times z_{4}$ topological classification of higher-order topological insulators with z _4 = 2. The system after Se substitution can be transformed into Weyl semimetals, strong 3D topological insulators, and unknown topological materials without symmetry-base indicators, respectively.

Solid-state thermo-stamping of fabric reinforced composites has attracted extensive attention for its efficiency and potential energy saving in recent years. In this paper, a hybrid lamination model is proposed to describe the forming behavior of woven fabric reinforced thermoplastic composites (WFRTP) during solid-state thermo-stamping process. The woven carbon fiber (CF)/ Polyetheretherketone (PEEK) sheet/prepreg is modelled as laminate structure with woven reinforcement layers (shell elements) embedded in thermoplastic resin layer (solid elements). More specifically, a hypoelastic constitutive model is used to represent the anisotropic mechanical behavior of fabric reinforcement under large deformation, while the fabric model is calibrated and validated by uniaxial bias extension (UBE) test and tensile test of woven fabric. A phenomenological model is adopted to describe the viscoelastic-plastic deformation behavior of thermoplastic resin, while the resin model is calibrated by tensile tests of PEEK. The applicability of the hybrid model is demonstrated through comparing numerical results of UBE tests and Erichsen tests with their corresponding experiment results. The hybrid lamination model provides a theoretical foundation for numerical simulation of WFRTP solid-state thermo-stamping.

The cathode/anode-electrolyte interfaces in lithium/sodium ion batteries act as the “gate” for the ion exchange between the solid electrode and liquid electrolyte. Understanding the interfacial properties of these solid-liquid interfaces is essential for better design high-performance lithium/sodium ion batteries. Here, we provide a novel method for studying solid-liquid interfacial properties of battery materials through combining physical vapor deposition (PVD) and beam-exit cross-sectional polishing (BEXP) followed by controlled environment multifunctional Scanning Probe Microscope (SPM). In this method, commercial battery materials can be either directly grown on the current collector substrates, or polished by obliqued Ar-ion beams to get a nanoscale flat surface which allows the multifunctional SPM to study sample directly in the liquid electrolyte or in protective oxygen/H2O free environment. This approach allows to investigate wide range of interfacial properties, including surface morphology, internal cracks, mechanical properties, electronic/ionic conductivity and surface potential, with nanoscale resolution in-operando during the battery cycles as well as post-mortem. • PVD and novel BEXP methods were introduced to prepare battery powder materials as perfect specimens for nanoscale SPM characterization. • Various physical/chemical properties of battery materials can be probed on the as-prepared specimens under liquid electrolyte using in situ/operando SPM techniques. • Ex situ/post-mortem analyses based on the controlled environment multifunction SPM characterizations can be achieved in the BEXP polished degradation battery electrodes.

High filler content is the prerequisite for imparting specific properties to polymeric composite. However, serious mechanical properties degradation happened in this kind of material due to the inevitable reduction of material cohesion. In this work, highly filled poly(butylene terephthalate)/ alumina (PBT/Al2O3) composites were modified by directly melt mixing with a reactive compatibilizer ethylene–methyl acrylate–glycidyl methacrylate terpolymer (E-MA-GMA). The modified samples presented greatly enhanced elongation at break and impact response, simultaneously preserved their tensile strength and high thermal conductivity. The reactive compatibilization between PBT and Al2O3 spheres was confirmed by SEM, FTIR, and rheology characterizations. Three rheology criteria plots demonstrated that the filler percolating network and apparent yield behavior occurred in the ternary PBT/Al2O3/E-MA-GMA composites melt. It is believed that enhanced particle-matrix interfacial interaction and stress transfer caused by E-MA-GMA endowed this highly filled composite improved toughness. This study suggests the potential application of E-MA-GMA elastomer to resolve the mechanical properties degradation in highly filled polymeric composites.

Abstract We have investigated the effects of graphene intercalation on dielectric reliability of HfO2 for Ni/Gr/HfO2 interfaces, and the effects of graphene intercalation and interfacial atom vacancy on the effective work function (EWF) of Ni/Gr/HfO2 interfaces using first-principle calculation based on density functional theory. The calculated results indicate that graphene intercalation can improve dielectric reliability of HfO2 dielectric even for the interfaces having interfacial oxygen vacancy or a small amount carbon vacancy. Moreover, the calculated results indicate that, inserting graphene into Ni/HfO2 interface induces the EWF’s to decline, and controlling interfacial oxygen or carbon vacancy can effectively tune the EWF of Ni/Gr/HfO2 interface. Our work strongly suggests that the use of graphene synthesized into Ni/HfO2 interface is a very effective way to improve the interface quality, and controlling interfacial oxygen or carbon vacancy is also an attractive and promising way for modulating the EWF of Ni/Gr/HfO2 interfaces.

Abstract The Electronic structure of PbPdO2 with (002) and (211) preferred orientations were investigated using first-principles calculation. The calculated results indicate that, (002) and (211) orientations exhibit different electric field dependence of band-gap and carrier concentration. The small band gap and more sensitive electric field modulation of band gap were found in (002) orientation. Moreover, the electric field modulation of the resistivity up to 3–4 orders of magnitude is also observed in (002) slab, which reveals that origin of colossal electroresistance. Lastly, electric field modulation of band gap is well explained. This work should be significant for repeating the colossal electroresistance.

Abstract The multi-functional nanomaterial constructed with more than one type of materials has gained a great attention due to its promising application. Here, a high white light photodetector prototype established with two-dimensional material (2D) and 2D nanocomposites has been fabricated. The 2D-2D nanocomposites were synthesized with SnSe nanoplate and graphene. The device shows a linear I-V characterization behavior in the dark and the resistance dramatically decreases under the white light. Furthermore, the photosensitivity of the device is as large as 1110% with a rapid response time, which is much higher than pristine SnSe nanostructure reported. The results shown here may provide a valuable guidance to design and fabricate the photodetector based on the 2D-2D nanocomposites even beyond the SnSe nanoplate-graphene nanocomposites.

In this paper, topological quantum phase transition was reported in the magnetic topological insulator MnBi _2 Te _4 under pressure strain. Electronic and topological properties of the bulk anti-ferromagnetic MnBi _2 Te _4 were investigated by first-principles calculations. We found that the band structure of MnBi _2 Te _4 changes with the strain, resulting in a phase transition between metal and insulator. From the variation of charge-density distribution with strain, it was found that hydrostatic tensile strain is beneficial for increasing the interlayer spacing, thereby reducing the anti-ferromagnetic interaction between layers. On the contrary, the compressive strain promotes the strengthening of the bonding between the Te and Bi atomic layers. It was worth noting that the phase transition occurs at 2.12% strain when the band crossing is observed at Γ point, suggesting that the band gap has just closed. In addition, through the calculation of surface states, it is observed that, after the action of 2.12% strain, the bulk band gap of the system closes with the surface band gap reopens, achieving an intrinsic mechanism of strain modulation of the MnBi _2 Te _4 antiferromagnetic bulk structure to undergoes a topological quantum phase transition. Our results provide feasible guidance not only for pressure-strain engineering of MnBi _2 Te _4 experimentally but also for developing a meaningful strain-control mechanism for the electronic structures of other potential intrinsic magnetic insulators.

Work functions and magnetic moments of C adsorbed Cr/Fe(001) surfaces with different C coverages θ and magnetic alignments (parallel or antiparallel) between Cr and Fe atom moments are investigated using first-principles methods based on density functional theory. The calculated results reveal that the spin configuration plays a significant role in determining the work function of the systems. The work functions of the systems with parallel states are evidently larger than those with antiparallel states. Moreover, for θ≤0.5 ML, with increasing value of θ, the work function increases from 4.23 eV to 5.13 eV for antiparallel states and from 4.47 eV to 5.44 eV for parallel states. While for θ>0.5 ML, the work function decreases with increasing value of θ. It can be also found that, for θ≤0.5 ML, the smaller the Cr and Fe magnetic moments are, the lower the Fermi energy EF is and the larger the work functions of the systems are. Based on analysis and discussion, we conclude that the changes of the work functions and magnetic moments are mainly determined by those of Fermi level and density of state (DOS) induced by the spin polarization, the electron transfer and the surface structure. Our work strongly suggests that controlling the magnetic states is a promising way for modulating the work function of magnetic metal gate.