Wood-inspired anisotropic hydrogel electrolyte with large modulus and low tortuosity realizing durable dendrite-free zinc-ion batteries.

While aqueous zinc-ion batteries exhibit great potential, their performance is impeded by zinc dendrites. Existing literature has proposed the use of hydrogel electrolytes to ameliorate this issue. Nevertheless, the mechanical attributes of hydrogel electrolytes, particularly their modulus, are suboptimal, primarily ascribed to the substantial water content. This drawback would severely restrict the dendrite-inhibiting efficacy, especially under large mass loadings of active materials. Inspired by the structural characteristics of wood, this study endeavors to fabricate the anisotropic carboxymethyl cellulose hydrogel electrolyte through directional freezing, salting-out effect, and compression reinforcement, aiming to maximize the modulus along the direction perpendicular to the electrode surface. The heightened modulus concurrently serves to suppress the vertical deposition of the intermediate product at the cathode. Meanwhile, the oriented channels with low tortuosity enabled by the anisotropic structure are beneficial to the ionic transport between the anode and cathode. Comparative analysis with an isotropic hydrogel sample reveals a marked enhancement in both modulus and ionic conductivity in the anisotropic hydrogel. This enhancement contributes to significantly improved zinc stripping/plating reversibility and mitigated electrochemical polarization. Additionally, a durable quasi-solid-state Zn//MnO2 battery with noteworthy volumetric energy density is realized. This study offers unique perspectives for designing hydrogel electrolytes and augmenting battery performance.

Unlocking the Design Paradigm of In-Plane Heterojunction with Built-in Bifunctional Anion Vacancy for Unexpectedly Fast Sodium Storage.

Transition metal chalcogenide (TMD) electrodes in sodium-ion batteries exhibit intrinsic shortcomings such as sluggish reaction kinetics, unstable conversion thermodynamics, and substantial volumetric strain effects, which lead to electrochemical failure. This report unlocks a design paradigm of VSe2- x /C in-plane heterojunction with built-in anion vacancy, achieved through an in situ functionalization and self-limited growth approach. Theoretical and experimental investigations reveal the bifunctional role of the Se vacancy in enhancing the ion diffusion kinetics and the structural thermodynamics of Nax VSe2 active phases. Moreover, this in-plane heterostructure facilitates complete face contact between the two components and tight interfacial conductive contact between the conversion phases, resulting in enhanced reaction reversibility. The VSe2- x /C heterojunction electrode exhibits remarkable sodium-ion storage performance, retaining specific capacities of 448.7 and 424.9 mAh g-1 after 1000 cycles at current densities of 5 and 10 A g-1 , respectively. Moreover, it exhibits a high specific capacity of 353.1 mAh g-1 even under the demanding condition of 100 A g-1 , surpassing most previous achievements. The proposed strategy can be extended to other V5 S8- x and V2 O5- x -based heterojunctions, marking a conceptual breakthrough in advanced electrode design for constructing high-performance sodium-ion batteries.

Unlocking the Interfacial Adsorption-Intercalation Pseudocapacitive Storage Limit to Enabling All-Climate, High Energy/Power Density and Durable Zn-Ion Batteries.

Sluggish storage kinetics and insufficient performance are the major challenges that restrict the transition metal dichalcogenides (TMDs) applied for zinc ion storage, especially at the extreme temperature conditions. Herein, a multiscale interface structure-integrated modulation concept was presented, to unlock the omnidirectional storage kinetics-enhanced porous VSe2-x ⋅n H2 O host. Theory research indicated that the co-modulation of H2 O intercalation and selenium vacancy enables enhancing the interfacial zinc ion capture ability and decreasing the zinc ion diffusion barrier. Moreover, an interfacial adsorption-intercalation pseudocapacitive storage mechanism was uncovered. Such cathode displayed remarkable storage performance at the wide temperature range (-40-60 °C) in aqueous and solid electrolytes. In particular, it can retain a high specific capacity of 173 mAh g-1 after 5000 cycles at 10 A g-1 , as well as a high energy density of 290 Wh kg-1 and a power density of 15.8 kW kg-1 at room temperature. Unexpectedly, a remarkably energy density of 465 Wh kg-1 and power density of 21.26 kW kg-1 at 60 °C also can be achieved, as well as 258 Wh kg-1 and 10.8 kW kg-1 at -20 °C. This work realizes a conceptual breakthrough for extending the interfacial storage limit of layered TMDs to construct all-climate high-performance Zn-ion batteries.

3D Artificial Array Interface Engineering Enabling Dendrite-Free Stable Zn Metal Anode.

The ripple effect induced by uncontrollable Zn deposition is considered as the Achilles heel for developing high-performance aqueous Zn-ion batteries. For this problem, this work reports a design concept of 3D artificial array interface engineering to achieve volume stress elimination, preferred orientation growth and dendrite-free stable Zn metal anode. The mechanism of MXene array interface on modulating the growth kinetics and deposition behavior of Zn atoms were firstly disclosed on the multi-scale level, including the in-situ optical microscopy and transient simulation at the mesoscopic scale, in-situ Raman spectroscopy and in-situ X-ray diffraction at the microscopic scale, as well as density functional theory calculation at the atomic scale. As indicated by the electrochemical performance tests, such engineered electrode exhibits the comprehensive enhancements not only in the resistance of corrosion and hydrogen evolution, but also the rate capability and cyclic stability. High-rate performance (20 mA cm-2) and durable cycle lifespan (1350 h at 0.5 mA cm-2, 1500 h at 1 mA cm-2 and 800 h at 5 mA cm-2) can be realized. Moreover, the improvement of rate capability (214.1 mAh g-1 obtained at 10 A g-1) and cyclic stability also can be demonstrated in the case of 3D MXene array@Zn/VO2 battery. Beyond the previous 2D closed interface engineering, this research offers a unique 3D open array interface engineering to stabilize Zn metal anode, the controllable Zn deposition mechanism revealed is also expected to deepen the fundamental of rechargeable batteries including but not limited to aqueous Zn metal batteries.

A Multifunctional Anti-Proton Electrolyte for High-Rate and Super-Stable Aqueous Zn-Vanadium Oxide Battery.

Large volumetric expansion of cathode hosts and sluggish transport kinetics in the cathode-electrolyte interface, as well as dendrite growth and hydrogen evolution at Zn anode side are considered as the system problems that cause the electrochemical failure of aqueous Zn-vanadium oxide battery. In this work, a multifunctional anti-proton electrolyte was proposed to synchronously solve all those issues. Theoretical and experimental studies confirm that PEG 400 additive can regulate the Zn2+ solvation structure and inhibit the ionization of free water molecules of the electrolyte. Then, smaller lattice expansion of vanadium oxide hosts and less associated by-product formation can be realized by using such electrolyte. Besides, such electrolyte is also beneficial to guide the uniform Zn deposition and suppress the side reaction of hydrogen evolution. Owing to the integrated synergetic modification, a high-rate and ultrastable aqueous Zn-V2O3/C battery can be constructed, which can remain a specific capacity of 222.8 mAh g-1 after 6000 cycles at 5 A g-1, and 121.8 mAh g-1 even after 18,000 cycles at 20 A g-1, respectively. Such "all-in-one" solution based on the electrolyte design provides a new strategy for developing high-performance aqueous Zn-ion battery.

Band structure tuning of α-MoO3 by tin intercalation for ultrafast photonic applications.

van der Waals (vdW) transition metal oxides have attracted extensive attention due to their intriguing physical and chemical properties. However, primary drawbacks of these materials are the lack of band structure tunability and substandard optical properties, which severely hinder their implementation in nanophotonic applications. Atomic intercalation is an emerging structural engineering approach for two-dimensional vdW materials to engineer the atomic structure and modify the optical properties, thereby broadening their range of applications. Herein, we synthesized tin-intercalated ultrathin α-MoO3 (Sn-MoO3) nanoribbons via chemical intercalation method and then investigated the broadband nonlinear optics (NLO) of stable few-layer α-MoO3 by performing a Z-scan laser measurement and femtosecond-resolved transient absorption (TA) spectroscopy. Sn-MoO3 showed a stable structure of Mo-O-Sn-O-Mo and a shorter relaxation time than pristine MoO3, indicating the accelerated recombination process of electrons and holes. Furthermore, Sn-MoO3 nanoribbons were used as an optical saturable absorber for ultrafast photonics; a highly stable femtosecond laser with a pulse width of 467 fs was generated from a single-mode fiber in the telecommunication band (1550 nm). These results indicate that atomic intercalation is an effective way to modulate the band structure and nonlinear optical properties of α-MoO3, which hold a great potential in the generation of ultrafast mode-locked laser pulses for optical communication technologies.

Two-Dimensional Black Arsenic Phosphorus for Ultrafast Photonics in Near- and Mid-Infrared Regimes.

Black arsenic phosphorus (b-AsP), as one kind of novel two-dimensional (2D) materials, bridges the band gap between black phosphorus and graphene. Thanks to its great advantages, including high carrier mobility, excellent in-plane anisotropy, and broad tunability band gap, b-AsP has aroused great interest in fields of photonics and photoelectronics. In this paper, ultrathin 2D b-AsP nanomaterials were fabricated by the liquid-phase exfoliation method, and their strong broadband linear and nonlinear absorptions were characterized by ultraviolet-visible-infrared and Z-scan technology. The experimental determination of the nonlinear absorption coefficient and low saturation intensity of b-AsP were -0.23 cm/GW and 3.336 GW/cm2, respectively. Based on density functional theory, the partial charge density and band structure at the conduction band minimum and valence band maximum were calculated, which further proves the excellent optical properties of 2D b-AsP. By first using 2D b-AsP as a novel saturable absorber in both erbium-doped and thulium-doped fiber lasers, mode-locked soliton pulses can stably operate at 1.5 and 2 µm. The laser pulses generated by 2D b-AsP possess higher stability to resist self-splitting than those generated by other 2D material-based mode-lockers. These experimental results highlight that 2D b-AsP has great application potential as a novel optical material in ultrafast photonics from near- to mid-infrared regimes.

Recent Advances of Spatial Self-Phase Modulation in 2D Materials and Passive Photonic Device Applications.

Optical nonlinearity in 2D materials excited by spatial Gaussian laser beam is a novel and peculiar optical phenomenon, which exhibits many novel and interesting applications in optical nonlinear devices. Passive photonic devices, such as optical switches, optical logical gates, photonic diodes, and optical modulators, are the key compositions in the future all-optical signal-processing technologies. Passive photonic devices using 2D materials to achieve the device functionality have attracted widespread concern in the past decade. In this Review, an overview of the spatial self-phase modulation (SSPM) in 2D materials is summarized, including the operating mechanism, optical parameter measurement, and tuning for 2D materials, and applications in photonic devices. Moreover, some current challenges are also proposed to solve, and some possible applications of SSPM method are predicted for the future. Therefore, it is anticipated that this summary can contribute to the application of 2D material-based spatial effect in all-optical signal-processing technologies.

Ultrathin boron nanosheets as an emerging two-dimensional photoluminescence material for bioimaging.

Two-dimensional (2D) metal-free sheets with atomic thickness have been highly considered as promising candidates for fluorescent probes, due to their intriguing characteristics. In this work, 2D ultrathin boron nanosheets (B NSs) with a surface defect nanolayer can be effectively prepared by modified liquid phase exfoliation. The as-prepared ultrathin B NSs show blue fluorescence characteristics even with a quantum yield efficiency of up to 10.6%. Such luminescent behavior originates from the quantum confinement effect and the existence of a surface defect layer. In light of the advantages of being environmentally friendly, having high photostability and good biocompatibility, for the first time we have shown that ultrathin B NSs can be used as an emerging fluorescent probe for application in cellular bioimaging. It is believed that this work will open new avenues for ultrathin B NSs in biomedical fields, and it will also inspire the development of other elemental 2D nanomaterials.

A self-powered photodetector based on two-dimensional boron nanosheets.

Owing to their intriguing characteristics, the ongoing pursuit of emerging mono-elemental two-dimensional (2D) nanosheets beyond graphene is an exciting research area for next-generation applications. Herein, we demonstrate that highly crystalline 2D boron (B) nanosheets can be efficiently synthesized by employing a modified liquid phase exfoliation method. Moreover, carrier dynamics has been systematically investigated by using femtosecond time-resolved transient absorption spectroscopy, demonstrating an ultrafast recovery speed during carrier transfer. Based on these results, the optoelectronic performance of the as-synthesized 2D B nanosheets has been investigated by applying them in photoelectrochemical (PEC)-type and field effect transistor (FET)-type photodetectors. The experimental results revealed that the as-fabricated PEC device not only exhibited a favourable self-powered capability, but also a high photoresponsivity of 2.9-91.7 µA W-1 in the UV region. Besides, the FET device also exhibited a tunable photoresponsivity in the range of 174-281.3 µA W-1 under the irradiation of excited light at 405 nm. We strongly believe that the current work shall pave the path for successful utilization of 2D B nanosheets in electronic and optoelectronic devices. Moreover, the proposed method can be utilized to explore other mono-elemental 2D nanomaterials.

Kerr Nonlinearity in 2D Graphdiyne for Passive Photonic Diodes.

Graphdiyne is a new carbon allotrope comprising sp- and sp2 -hybridized carbon atoms arranged in a 2D layered structure. In this contribution, 2D graphdiyne is demonstrated to exhibit a strong light-matter interaction with high stability to achieve a broadband Kerr nonlinear optical response, which is useful for nonreciprocal light propagation in passive photonic diodes. Furthermore, advantage of the unique Kerr nonlinearity of 2D graphdiyne is taken and a nonreciprocal light propagation device is proposed based on the novel similarity comparison method. Graphdiyne has demonstrated a large nonlinear refractive index in the order of ≈10-5 cm2 W-1 , comparing favorably to that of graphene. Based on the strong Kerr nonlinearity of 2D graphdiyne, a nonlinear photonic diode that breaks time-reversal symmetry is demonstrated to realize the unidirectional excitation of Kerr nonlinearity, which can be regarded as a significant demonstration of a graphdiyne-based prototypical application in nonlinear photonics and might suggest an important step toward versatile graphdiyne-based advanced passive photonics devices in the future.

Ultrathin GeSe Nanosheets: From Systematic Synthesis to Studies of Carrier Dynamics and Applications for a High-Performance UV-Vis Photodetector.

Owing to the attractive energy band properties, a black phosphorus (BP)-analogue semiconductor, germanium selenide (GeSe), shows a promising potential applied for optoelectronic devices. Herein, ultrathin GeSe nanosheets were systematically prepared via a facile liquid-phase exfoliation approach, with controllable nanoscale thickness. Different from BP, ultrathin GeSe nanosheets exhibit good stability under both liquid and ambient conditions. Besides, its ultrafast carrier dynamics was probed by transient absorption spectroscopy. We showed that the GeSe nanosheet-based photodetector exhibits excellent photoresponse behaviors ranging from ultraviolet (UV) to the visible regime, with high responsivity and low dark current. Furthermore, the detective ability of such a device can be effectively modulated by varying the applied bias potential, light intensity, and concentration of the electrolyte. Generally, our present contribution could not only supply fundamental knowledge of a GeSe nanosheet-based photoelectrochemical (PEC)-type device, but also offer guidance to extend other possible semiconductor materials in the application of the PEC-type photodetector.

Two-dimensional beta-lead oxide quantum dots.

In recent years, black-phosphorus-analogue (BPA) two-dimensional (2D) materials have been explored to demonstrate promising optoelectronic performances and distinguished ambient stabilities, holding great promise in practical applications. Here, one new kind of BPA material, orthorhombic ß-PbO quantum dots (QDs), is successfully fabricated by a facile liquid phase exfoliation (LPE) technique. The as-prepared ß-PbO QDs show a homogeneous distribution of the lateral size (3.2 ± 0.9 nm) and thickness (2.5 ± 0.5 nm), corresponding to 4 ± 1 layers. The carrier dynamics of ß-PbO QDs was systematically investigated via a femtosecond resolution transient absorption approach in the visible wavelength regime and it was clarified that two decay components were resolved with a decay time of τ1 = 2.3 ± 0.3 ps and τ2 = 87.9 ± 6.0 ps, respectively, providing important insights into their potential applications in the field of ultrafast optics, nanomechanics and optoelectronics. As a proof-of-concept, ß-PbO QDs were, for the first time to our knowledge, fabricated as a working electrode in a photoelectrochemical (PEC)-typed photodetector that exhibits significantly high photocurrent density and excellent stability under ambient conditions.

Oxygen Vacancy Engineering in Tin(IV) Oxide Based Anode Materials toward Advanced Sodium-Ion Batteries.

A high theoretical capacity of approximately 1400 mA h g-1 makes SnO2 a promising anode material for sodium-ion batteries (SIBs). However, large volume expansion, poor intrinsic conductivity, and sluggish reaction kinetics have greatly hindered its practical application. The controlled creation of oxygen vacancy (OV) defects allows the intrinsic properties of SnO2 to be effectively modulated, but related work concerning SIBs is still lacking. In this Minireview, the mechanism of failure of SnO2 electrodes is discussed and an overview of recent progress in the general synthesis of OV-containing SnO2 materials and the feasible detection of OVs in SnO2 is presented. The use of OV-containing SnO2 -based anode materials in SIBs is also reviewed. Finally, challenges and future opportunities to engineer OVs for semiconductor oxides are examined.

Robust SnO2-x Nanoparticle-Impregnated Carbon Nanofibers with Outstanding Electrochemical Performance for Advanced Sodium-Ion Batteries.

The sluggish sodium reaction kinetics, unstable Sn/Na2 O interface, and large volume expansion are major obstacles that impede practical applications of SnO2 -based electrodes for sodium-ion batteries (SIBs). Herein, we report the crafting of homogeneously confined oxygen-vacancy-containing SnO2-x nanoparticles with well-defined void space in porous carbon nanofibers (denoted SnO2-x /C composites) that address the issues noted above for advanced SIBs. Notably, SnO2-x /C composites can be readily exploited as the working electrode, without need for binders and conductive additives. In contrast to past work, SnO2-x /C composites-based SIBs show remarkable electrochemical performance, offering high reversible capacity, ultralong cyclic stability, and excellent rate capability. A discharge capacity of 565 mAh g-1 at 1 A g-1 is retained after 2000 cycles.

Facile fabrication and characterization of two-dimensional bismuth(iii) sulfide nanosheets for high-performance photodetector applications under ambient conditions.

Two-dimensional (2D) bismuth(iii) sulfide (Bi2S3) nanosheets as non-toxic graphene-like nanomaterials were successfully fabricated by a facile liquid phase exfoliation (LPE) method. A robust photodetector employing a Bi2S3 nanosheet film has been fabricated for the first time via a facile fabrication process on an ITO-coated glass. UV-Vis and Raman spectroscopy techniques were carried out and they confirmed the inherent optical and physical properties of Bi2S3 nanosheets. Photoelectrochemical (PEC) measurements demonstrate that a significantly higher photocurrent density (42 µA cm-2) and enhanced photoresponsivity (210 µA W-1), at a lower bias potential in alkaline solution, of the Bi2S3 nanosheet-based photodetector are achieved, compared with those of other 2D nanomaterial-based photodetectors under light irradiation. Furthermore, the as-prepared Bi2S3 nanosheet-based photodetector not only exhibits an appropriate capacity of self-driven broadband and high-performance photoresponse but also displays strong long-term stability of the ON/OFF switching behaviour without any external protection in alkaline solutions. Because of facile synthesis via a LPE method, a higher photocurrent density and photoresponsivity, self-driven performance and long-term stability of the Bi2S3 nanosheet-based photodetector at a lower bias potential in alkaline solutions, the present work can provide fundamental acknowledgement of the high performance of this new kind of PEC-type 2D nanosheet-based photodetector.

In situ nitrogen doping of TiO2 by plasma enhanced atomic layer deposition for enhanced sodium storage performance.

Nitrogen-doped TiO2 is in situ synthesized by plasma enhanced atomic layer deposition on carbon nanotubes (N-TiO2/CNTs). The prepared N-TiO2/CNT nanocomposites are employed as anode materials for sodium ion batteries. The specific capacity of an N-TiO2/CNT electrode is 1.45 times higher than that of a TiO2/CNT electrode at a current density of 50 mA g-1 after 200 cycles. It is demonstrated that N-TiO2/CNTs are more effective in an electrochemical Na cell due to the enhanced kinetics which results from the nitrogen-doping and the amorphous feature.

Li1.2Mn0.54Ni0.13Co0.13O2-Encapsulated Carbon Nanofiber Network Cathodes with Improved Stability and Rate Capability for Li-Ion Batteries.

Li1.2Mn0.54Ni0.13Co0.13O2-encapsulated carbon nanofiber network cathode materials were synthesized by a facile electrospinning method. The microstructures, morphologies and electrochemical properties are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), galvonostatic charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy (EIS), etc. The nanofiber decorated Li1.2Mn0.54Ni0.13Co0.13O2 electrode demonstrated higher coulombic efficiency of 83.5%, and discharge capacity of 263.7 mAh g(-1) at 1 C as well as higher stability compared to the pristine particle counterpart. The superior electrochemical performance results from the novel network structure which provides fast transport channels for electrons and lithium ions and the outer carbon acts a protection layer which prevents the inner oxides from reacting with HF in the electrolyte during charge-discharge cycling.