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In situ imaging of LiO2 dynamics in LOBs with Au/CNT cathode was conducted by ETEM. During discharge, LiO2 formed from Li15Au4 seeds with stability for several minutes. The de-activation of Lifacilitates the nucleation and stabilization of LiO2.

Memristors are an interesting novel class of devices for memory and beyond von Neumann computing. Besides classical CMOS technology, memristors can also be manufactured by additive printing techniques and hold great potential for printable neuromorphic circuits and memories. In this work, we report a fully inkjet-printed unipolar metal oxide memristor with a low forming voltage. The memristor is based on a sandwich-like Ag/ZnO/Ag structure. The device exhibits excellent performance parameters, such as high cycle-to-cycle and device-to-device uniformity and a long retention time of ≥104 s. Furthermore, the inkjet-printed memristor shows an exceptionally high ROFF/RON ratio of 107 over 100 pulsed switching cycles.

Performing reliable preparation of transmission electron microscopy (TEM) samples is the necessary basis for a meaningful investigation by ex situ and even more so by in situ TEM techniques, but it is challenging using materials that are sensitive to electron beam irradiation. Focused ion beam is currently the most commonly employed technique for a targeted preparation, but the structural modifications induced during focused ion beam preparation are not fully understood for a number of materials. Here, we have investigated the impact of both the electron and the Ga+ ion beam on insulating solid-state electrolytes (lithium phosphorus oxynitride, Na-β"-alumina solid electrolyte and Na3.4Si2.4Zr2P0.6O12 (NaSICON)) and observed significant lithium/sodium whisker growth induced by both the electron and ion beam already at fairly low dose, leading to a significant change in the chemical composition. The metal whisker growth is presumably mainly due to surface charging, which can be reduced by coating with a gold layer or preparation under cryogenic conditions as efficient approaches to stabilize the solid electrolyte for scanning electron microscopy imaging and TEM sample preparation. Details on the different preparation approaches, the acceleration voltage dependence and the induced chemical and morphological changes are reported.

Performing reliable preparation of TEM samples is the necessary basis for a meaningful investigation by ex-situ and even more so by in-situ TEM techniques, but it is challenging using materials that are sensitive to electron-beam irradiation. FIB is currently the most commonly employed technique for a targeted preparation, but the structural modifications induced during FIB preparation are not fully understood for a number of materials. Here, we have investigated the impact of both the electron and the Ga+ ion beam on insulating solid-state electrolytes (LiPON, BASE and NaSICON) and observed significant Li/Na whisker growth induced by both the electron and ion beam already at fairly low dose leading to a significant change in the chemical composition. The metal whisker growth is presumably mainly due to surface charging which can be reduced by coating with a gold layer or preparation at cryogenic conditions as efficient approaches to stabilize the solid electrolyte for SEM imaging and TEM sample preparation. Details on the different preparation approaches, the acceleration voltage dependence and the induced chemical and morphological changes are reported.

Electron tomography (ET) has gained increasing attention for the 3D characterization of nanoparticles. However, the missing wedge problem due to a limited tilt angle range is still the main challenge for accurate reconstruction in most experimental TEM setups. Advanced algorithms could in-paint or compensate to some extent the missing wedge artifacts, but cannot recover the missing structural information completely. 360° ET provides an option to solve this problem by tilting a needle-shaped specimen over the full tilt range and thus filling the missing information. However, sample preparation especially for fine powders to perform full-range ET is still challenging, thus limiting its application. In this work, we propose a new universal sample preparation method that enables the transfer of selected individual nanoparticle or a few separated nanoparticles by cutting a piece of carbon film supporting the specimen particles and mounting them onto the full-range tomography holder tip with the help of an easily prepared sharp tungsten tip. This method is demonstrated by 360° ET of Pt@TiO2 hollow cage catalyst showing high quality reconstruction without missing wedge.

The commercial graphite (CG) is the conventional anode material for lithium ion batteries (LIBs) due to its low delithiation voltage plateau (below 0.5 V) and extraordinary durability. Nevertheless, the further promotion of energy density of LIBs is restricted by the limited capacity below 0.5 V of CG. Here, based on the supercritical CO2 exfoliation technique, the production of multi-layered graphene (MLG) is achieved from the pilot scale production line. The great merit of the exfoliated MLG anode is that the voltage plateau below 0.5 V is broadened obviously as compared to those of natural graphite and CG. Additionally, no obvious lithium dendrites are observed for MLG during the lithiation process. The large delithiation capacity under the low voltage plateau of MLG is mainly benefited from the combination of Li intercalation and boundary storage mechanism, which is further confirmed by the density functional theory calculations. The LiFePO4/MLG full cell can afford the satisfactory electrochemical property with respect to the capacity, energy density and ultralong cycling stability (90% capacity retention after 500 cycles at 2 C), significantly better than that of LiFePO4/CG. Besides, this developed technique not only dedicates to producing the high-performance anode for LIBs but also opens a door for the mass production of MLG in the industrial scale.

Akin to Li, Na deposits in a dendritic form to cause short circuit in Na metal batteries. However, the growth mechanisms and related mechanical properties of Na dendrites remain largely unknown. He...

Mn-based hexacyanoferrate (Mn-HCF) cathodes for Na-ion batteries usually suffer from poor reversibility and capacity decay resulting from unfavorable phase transitions and structural degradation during cycling. To address this issue, the high-entropy concept is here applied to Mn-HCF materials, significantly improving the sodium storage capabilities of this system via a solid-solution mechanism with minor crystallographic changes upon de-/sodiation. Complementary structural, electrochemical, and computational characterization methods are used to compare the behavior of high-, medium-, and low-entropy multicomponent Mn-HCFs resolving, to our knowledge for the first time, the link between configurational entropy/compositional disorder (entropy-mediated suppression of phase transitions, etc.) and cycling performance/stability in this promising class of next-generation cathode materials.

Bulk-type solid-state batteries (SSBs) composed of lithium thiophosphate superionic solid electrolytes (SEs) and high-capacity cathode active materials (CAMs) have recently attracted much attention for their potential application in next-generation electrochemical energy storage. However, compatibility issues between the key components in this kind of battery system are difficult to overcome. Here, we report on a protective cathode coating that strongly reduces the prevalence of detrimental side reactions between CAM and SE during battery operation. This is demonstrated using preformed HfO

Inorganic solid-state batteries are attracting significant interest as a contender to conventional liquid electrolyte-based lithium-ion batteries but still suffer from several limitations. The search for advanced coatings for protecting cathode materials in solid-state batteries to achieve interfacial stability is a continuing challenge. In the present work, the surface of an industrially relevant Ni-rich LiNi$_x$Co$_y$Mn$_z$O$_2$ cathode material, NCM-851005 (85 % Ni), was modified by applying a coating containing Li, Nb and Zn, aiming at a composition Li$_6$ZnNb$_4$O$_14$, by means of sol-gel chemistry. Detailed characterization using scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy and nano-beam electron diffraction showed that the surface layer after heating in O$_2$ at 500 °C contains Li$_3$NbO$_4$ nanocrystals and Li$_2$CO$_3$, with Zn presumably acting as a dopant. The protective coating on the NCM-851005 secondary particles significantly increased the cycling performance (reversible capacity, rate capability etc.) and stability of full cells using argyrodite Li$_6$PS$_5$Cl as solid electrolyte. Interestingly, the level of improvement is superior to that achieved with conventional LiNbO$_3$ coatings.

In nonaqueous Mg batteries, inactive adsorbed species and the passivation layer formed from the reactive Mg with impurities in the electrolyte seriously affect the Mg metal/electrolyte interface. These adlayers can impede the passage of Mg$^{2+}$ ions, leading to a high Mg plating/stripping overpotential. Herein, we report the properties of a new additive, bismuth triflate (Bi(OTf)$_{3}$), for synthesizing a chlorine-free Mg electrolyte to enhance Mg plating/stripping from initial cycles. The beneficial effect of Bi(OTf)$_{3}$ can be ascribed to Bi/Mg$_{3}$Bi$_{2}$ formed in situ on the Mg metal surface, which increases the charge transfer during the on–off transition by reducing the adsorption of inactive species on the Mg surface and enhancing the resistance of the reactive surface to passivation. This simple method provides a new avenue to improve the compatibility between the Cl-free Mg electrolyte and the Mg metal anode.

Lithium metal is considered the ultimate anode material for future rechargeable batteries1,2, but the development of Li metal-based rechargeable batteries has achieved only limited success due to uncontrollable Li dendrite growth3–7. In a broad class of all-solid-state Li batteries, one approach to suppress Li dendrite growth has been the use of mechanically stiff solid electrolytes8,9. However, Li dendrites still grow through them10,11. Resolving this issue requires a fundamental understanding of the growth and associated electro-chemo-mechanical behaviour of Li dendrites. Here, we report in situ growth observation and stress measurement of individual Li whiskers, the primary Li dendrite morphologies12. We combine an atomic force microscope with an environmental transmission electron microscope in a novel experimental set-up. At room temperature, a submicrometre whisker grows under an applied voltage (overpotential) against the atomic force microscope tip, generating a growth stress up to 130 MPa; this value is substantially higher than the stresses previously reported for bulk13 and micrometre-sized Li14. The measured yield strength of Li whiskers under pure mechanical loading reaches as high as 244 MPa. Our results provide quantitative benchmarks for the design of Li dendrite growth suppression strategies in all-solid-state batteries. Lithium whisker growth and mechanical properties can be studied in situ using a combination of two microscopies.

MnO@C/CNTs compounds with adjustable thickness to achieve excellent electromagnetic wave (EMW) absorption performance are successfully fabricated by combining a chemical vapor deposition (CVD) method and carbonization process. The obtained worm hollow MnO@C/CNTs nanostructures have a synergistic effect between the MnO microspheres and the carbon shell layers, and a specific amount of carbon nanotubes (CNTs) can improve the overall conductivity of the composite material, resulting in multipolar polarization, surface polarization and concomitant relaxation. Under the optimized state, the MnO@C/CNTs composites present the best EMW absorption performance, with the reflection loss (RL) value of −60.5 dB and the effective absorption bandwidth (

The development of silicon-based anode materials is important for improving the energy density of current lithium ion batteries. However, there are still strong demands for these materials with better cycle stability and higher reversible capacity. Here, a kind of dual bond restricted MXene-Si-CNT composite anode materials with enhanced electrochemical performance is reported. These dual bonds have been clearly revealed by an X-ray photoelectron spectroscopy technique and also proven by theoretical calculations with spontaneous reaction energy values (-0.190 and -0.429 eV/atom for Ti-Si and C-Si bonds, respectively). The cycle stability of the composites, prepared by a facile ball-milling synthetic method, can obviously be improved because of the existence of these dual bonds and the multidimensional constructed architecture. The MXene-Si-CNT composite with 60 wt % silicon possesses the best overall performance, with ∼80% capacity retention after 200 cycles, and achieves 841 mAh g-1 at 2 A g-1. This approach demonstrates a promising strategy to exploit high-performance anode materials and lessens the immanent negative effect of silicon-based materials. Furthermore, it is significant to extend this method to other anode materials with serious volumetric change problems during the cycling process.

A facile yet rational strategy is highly desired for the synthesis of high-value-added carbon materials from cheap petroleum asphalt. Here, we develop an in situ texturing strategy for the synthesi...

Lithiation, sodiation, and potassiation usually induce volume expansion to the host structure due to the insertion of alkali metal ions into the host structure. Here we report an unusual volume shrinkage phenomenon during the potassiation of CuO nanowires. The volume shrinkage is caused by an “oxygen pump” and an electrochemically driven Kirkendall effect, in which the O2− ions in the CuO lattice and the K+ migrate asymmetrically under external electric field due to their different mass-to-charge ratio. This is the first direct observation on the “oxygen pump” and electrochemical Kirkendall effect induced volume shrinkage phenomenon, which reveals peculiar ion transport characteristic during electrochemical reactions.

Dielectric composites with high thermal conductivity and mechanical strength have great potential in microelectronic packaging. However, conventional composites with excellent thermal conductivity generally possess high electrical conductivity which raises short-circuit problems and unsatisfactory mechanical properties which limits their applications. In this work, dielectric composites with superior thermal and mechanical performance are obtained by fabricating a new type of fillers with three-dimensional (3D) nanostructure. Specially speaking, carbon nanotubes (CNTs) are grown on the surface of boron nitride nanosheets (BNNS) by chemical vapor deposition (CVD), and then utilized as fillers in epoxy resin (BNNS/CNT/Epoxy). The thermal, mechanical and dielectric properties of as-prepared composites are investigated in details. It is shown that the cross-plane thermal conductivity enhancement of the novel composite is as high as 615% compared with the pure epoxy, higher than that of BNNS/Epoxy (380%). Meanwhile, the BNNS/CNT/Epoxy remains a high electrical resistivity of more than 1 Mohm·cm, which is important to avoid short-circuit in electronics. The tensile strength of the composite increases nearly 4 times with the increase of CVD time. These experimental results indicate that the fabricated BNNS/CNT has great potential for reinforcement of composites with wide applications.

In this Letter, we report an inkjet-printed resistive switching device based on an Ag/ZnO/Au structure. The device exhibits bipolar resistive switching behavior, a low operation voltage of about 0.7 V, a high on/off ratio of 107, a long retention time exceeding 104 s, and good endurance. The conduction mechanism of the device in low and high resistive states was studied and showed good consistency with the theory of Ohmic and space charge limited conduction mechanisms, respectively.

Rational design of heterogeneous non-noble metal catalysts as highly efficient and selective catalysts for hydrogenation of nitroarenes with hydrogen as the reducing agent is currently a great challenge, which has attracted a great deal of attention. Herein, a new strategy for achieving atomic dispersion of Ni atoms on nitrogen-doped porous carbon (Ni–N–C) with a specific surface area of up to 810 m2 g−1 and nickel loading as high as 4.4 wt% is developed, yielding high activity, chemoselectivity, and reusability of catalysts in the hydrogenation of nitroarenes using hydrogen as the reductant with a turnover of number (TON) value of 84 and a turnover of frequency (TOF) value of 8.4 h−1 for the first time. The Ni single atoms anchored on N-doped porous carbon by binding with nitrogen/carbon have been proved to be the active sites. Importantly, the Ni–N3 active species is found to contribute more activity compared with Ni–N2 and Ni–N4. Density functional theory (DFT) calculations also reveal that the Ni–N3 structure exhibits the highest activity according to the lowest adsorption energy and the longest elongation N–O bonds of nitrobenzene, which originated from the induced charge transfer. This work opens a new route for rational design and accurate modulation of nanostructured organic molecular transformation catalysts at the atomic scale.

Carbon dioxide (CO2) as a greenhouse gas causes globe warming. Recent studies have shown that CO2 can be harnessed to make an energy storage device through the operation of metal-CO2 batteries. While the Li-CO2 and Na-CO2 batteries showing high capacity and good cycle life have been demonstrated, the possibility of creating a K-CO2 battery has not been realized. Here we report the creation of a K-CO2 battery by using CO2 as the cathode in an advanced aberration corrected environmental transmission electron microscope, and in-situ observation of the discharge and charge processes of the nanobattery. During discharge, K2CO3 was generated in the cathode, which converted back to metal K during charge, and the K-CO2 nanobattery demonstrates a good cyclability. Moreover, it is evident that CO gas was released during discharge and the carbon cathode was consumed continuously during charge. Our study provides a fundamental understanding of the K-CO2 battery, which may aid the designing of K-CO2 based energy storage devices.

Investigating lightweight electromagnetic microwave absorption materials is still urgent because of the issue related to the electromagnetic pollution or military defense. Our findings indicate that core-shell MnO@carbon nanowires (MnO@C NWs) achieve substantially enhanced microwave absorption, suggesting the suitable impedance matching induced by the synergetic effect between MnO and carbon. Furthermore, the peapod-like MnO@C NWs with internal void space can be facially synthesized by partial etching of core-shell MnO@C NWs. The peapod-like MnO@C NWs with internal voids/cavities exhibit dramatically enhanced electromagnetic microwave absorption property when the carbon content is about 64 wt %, a minimum reflection loss (RL) of -55 dB at 10 wt % loading was observed at 13.6 GHz, and the bandwidth of RL less than -10 dB (90% absorption) covers 6.2 GHz at the thickness of 2 mm. The excellent electromagnetic microwave absorption performance is superior to the most of MnO x/C composites in the literatures, which probably benefits from the dielectric polarization among conductive network structure between MnO and carbon, as well as the multiple reflection and absorption induced by internal void space. Our work is expected to pave an effective way to extend the electromagnetic microwave absorption performance of MnO/C composites through partial etching to create a void space.

Facile yet rational design of efficient electrocatalyst toward triiodide reduction reaction is a persistent challenge for the practical application of dye-sensitized solar cell (DSSC). Here we propose a protocol for fabricating atomic N-coordinated cobalt sites (Co-Nx-C) within nanomesh graphene frameworks (Co-NMG). The as-synthesized Co-NMG combines the features of atomically dispersed active sites and interconnected mesoporous structure with high porosity, which makes these active sites fully exposed and accessible while facilitating the mass transport of reactants. As a result, the Co-NMG electrocatalysts with substantial active sites and desired porous architectures exhibit high electrocatalytic activity and long-term electrochemical stability. Electrochemical measurements and DFT calculations reveal that the catalytic sites toward the reduction of triiodide mainly derive from the abundant topological defects, nitrogen dopants, and especially the atomic Co-Nx-C moieties. Furthermore, with Co-NMG as counter electrodes (CEs), the DSSCs display a power conversion efficiency of 9.06%, which is higher than that of Pt CEs (7.71%). This work not only provides a promising CE material for DSSC to address the issues associated with Pt catalyst, but also opens up new avenues for developing nanocarbon based catalysts with desired features for other energy-related applications.

A new type of silica nanosphere supported palladium nanoparticles encapsulated with graphene (denoted as Pd/SiO2@RGO) sandwich nanostructure electrocatalyst is prepared via a two-step reduction method for the first time. The characterization of electrocatalyst morphology and composition is discussed by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The TEM and XRD results show that palladium nanoparticles (Pd NPs) with a narrow size distribution are uniformly dispersed between silica sphere and the graphene layer. The ternary hybrid electrocatalyst exhibits high activity (1533 mA mg−1pd), superior operational durability and anti-poisoning ability (If/Ib = 3.9) compared with other controlled Pd catalysts. Moreover, it significantly reduces the peak potential (ca. 40 mv) and onset potential (ca. 80 mv) than commercial Pd/C, accounting for combination of the merits of SiO2 nanosphere support and the excellent electronic conductivity of RGO while overcoming their shortcomings. We provide an efficient way to fabricate a promising non-platinum anode catalyst for alkaline fuel cells.

Herein, we report a facile yet effective fluorescent nanosensor for the direct, selective and sensitive determination of cerebral Cu2+ in the rat brain microdialysate. The fluorescent nanosensor is constructed by utilizing the strong fluorescent graphene quantum dots (GQDs) as the fluorescent signaling output, which were synthesized via chemical oxidation from 3D nanomesh graphene frameworks (NGFs). Initially, the as-prepared GQDs displays a uniform size with lateral size below 5 nm is observed to exhibit photoluminescence properties. The subsequent addition of Cu2+ into the GQDs mixture results in the significant quenching of the fluorescence of GQDs. The quenching degree of Cu2+ towards GQDs is highly sensitive to the concentration of Cu2+ and shows a linear relationship for Cu2+ within the range from 0.1 μM to 1.0 μM with a limit of detection (LOD) of 0.067 μM which substantially enables the GQDs as a nanosensor for Cu2+. Moreover, the as-fabricated nanosenor displays a high specificity for Cu2+ irrespective of the coexistence of other metal ions, amino acids, and biological substance that endogenously existed in the rat brain and has been employed to successfully determination of Cu2+ in rat brain with the basal value of 2.21 ± 0.76 μM (n = 3).

Boron and nitrogen co-doped graphene-like carbon (BNC) with a gram scale was synthesized via a two-step method including a ball-milling process and a calcination process and used as electrode materials for supercapacitors. High surface area and abundant active sites of graphene-like carbon were created by the ball-milling process. Interestingly, the nitrogen atoms are doped in carbon matrix without any other N sources except for air. The textual and chemical properties can be easily tuned by changing the calcination temperature, and at 900 oC the BNC with a high surface area (802.35 m2/g), a high boron content (2.19 at%), a hierarchical pore size distribution and a relatively high graphitic degree was obtained. It shows an excellent performance of high specific capacitance retention about 78.2% at high current density (199 F/g at 100 A/g) of the initial capacitance (254 F/g at 0.25 A/g) and good cycling stability (90% capacitance retention over 1000 cycles at 100 A/g) measured in a three-electrode system. Furthermore, in a two-electrode system, a specific capacitance of 225 F/g at 0.25 A/g and a good cycling stability (93% capacitance retention over 20,000 cycles at 25 A/g) were achieved by using BNC as electrodes. The strategy of synthesis is facile and effective to fabricate multi-doped graphene-like carbon for promising candidates as electrode materials in supercapacitors.

In the past decades, graphene has attracted much attention as the host material of photodetectors (PDs), owing to its fascinating mechanical property, ultrahigh carrier mobility and remarkable optical transparency. However, the intrinsic low light absorption of graphene affects its comprehensive application in PDs. Therefore, graphene-based PDs research has focused on hybrid system and optimized graphene structures to enhance photoabsorption. In order to combine the advantages of both approaches, we successfully prepared crumpled reduced graphene oxide (C-rGO) for PDs by a simple ultrasonic pyrolysis method. Through this rapid, one-step capillary-driven route, C-rGO and C-rGO/(ZnO,PbS) composite films can be easily deposited on arbitrary substrates (PET, glass, Al2O3 ceramic and paper). Interestingly, the unique C-rGO PDs shows superior stability and fast transient photocurrent response (rise/decay time of 189/189 ms). Furthermore, by incorporating ZnO and PbS nanoparticles to enhance light absorption, the crumpled hybrid nanostructure PDs demonstrate about four times increased photocurrents and broad-band (UV–Vis–NIR) photodetection features with R of 0.12 A/W. Such crumpled C-rGO-based PDs hold great potentials for future optoelectronic applications, and the ultrasonic pyrolysis method could open a new way for engineering novel nanostructured thin films with high-performance photodetection.

Molybdenum disulfide (MoS2) has attracted a great deal of attention to its unique properties in recent years. In this work, a scalable and green method was developed for the production of high-quality MoS2 nanosheets using shear-assisted supercritical CO2 exfoliation. Our experiments indicate that high temperature, pressure, and shearing speed are favorable to the exfoliation of MoS2. It is found that over 95% of the exfoliated MoS2 nanosheets are less than 10 layers, among which about 50% are 1–4 layers. Raman spectra and XRD patterns reveal that few-layer MoS2 nanosheets with high planar crystal structure are successfully prepared. Moreover, the produced MoS2 has a better stability in N-methyl-pyrrolidone (NMP) than the bulk MoS2. The concentration of the exfoliated MoS2 in NMP after sedimentation for 7 days is as high as 0.97 mg/ml.

Micro molybdenum disulfide was prepared with one-step hydrothermal method; the influence of reactant concentration and temperature on the surface ratio of micro-MoS2 grain was investigated. Raman spectroscopy (Raman), X-ray diffraction (XRD), and Scanning electron microscopy (SEM) were used to characterize the structure, composition and morphology of MoS2. The results show that micro-MoS2 grains were synthesized with one-step hydrothermal synthesis, and the morphology of micro-MoS2 grains is like flower and sphere. The SEM figures indicate that the surface ratio of micro-MoS2 grains is different and also show that the surface ratio of micro-MoS2 grains can be improved by regulating reactant concentration and temperature. This research showed a method to improve the surface ratio of micro-MoS2 grains.