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Sponges based on short electrospun fibers have received significant attention due to their ultrahigh porosity, lightweight, and multifunctional characteristics. In particular, polyimide (PI) sponges have been researched due to their exceptional mechanical properties and thermal stability. Nevertheless, a number of sponges, including PI, are usually hydrophobic and synthesized in toxic, nonwater solvents (e.g., 1,4-dioxane). Conversely, hydrophilic sponges disintegrate upon contact with water. Here, we suggest a new strategy to fabricate PI sponges in water by introducing a suitable surfactant, sodium dodecylbenzenesulfonate (SDBS) (sPI sponges). With less than 1 wt % of SDBS with respect to PI short fibers, they can be homogeneously dispersed in water and mixed well with poly(amic acid) (PAA) solution. The synthesized sponge, depending on the concentration of SDBS, showed hydrophilic properties and substantial water uptake above 5000%. The hydrophilic properties of the sponges, which are not common, and the preparation from aqueous solution introduce new research opportunities. Such hydrophilic sponges are particularly special because they do not swell in contact with water, which makes them dimensionally stable. The methods presented here can serve as a milestone for the future development of various kinds of hydrophilic sponges applied for various applications, ranging from tissue engineering to oil/water separation.

Aqueous Zn-ion battery has developed as an alternative to overcome the limitations of conventional Li-ion batteries, but its application is insufficient due to low reversibility and electrochemical reliability. In this study, we developed a cathode for aqueous Zn-ion battery with improvement of reversibility and electrochemical reliability utilizing phthalocyanine (PTC) that efficiently transports metal ions and electrons. The intercalation/de-intercalation reaction of Zn2+ ions changes according to the central metal ligand ion of PTC, and iron (II) coordinated PTC exhibited the outstanding energy storage capacity (161.34 mAh/g) and electrochemical reliability (99%, 100 cycles). Based on maximized electrochemical performance and reliability, Zn-ion flexible battery was successfully demonstrated by utilizing air-spray coating.

LiNi0.5Mn1.5O4 (LNMO) cathode thin films were prepared on Pt-coated stainless steel (SS) substrates by radio-frequency magnetron sputtering. The layers were post-annealed at 500, 600 and 700 °C to study the impact of thermal treatment on the crystallization of the cathode material. As the annealing temperature increases, interdiffusion occurs between the substrate and the LNMO film, which degrades the electrochemical properties of the cathode film. In order to mitigate this problem, an In-Sn-O (ITO) interlayer was introduced between Pt and the SS substrate. The ITO film is electrochemically stable and acts as an effective diffusion barrier between the substrate and the LNMO layer, which results in improved electrochemical properties of the LNMO film for a lithium ion battery.

Lithium-ion batteries (LIBs) with higher energy density are necessary to meet the increasing demands of energy storage system (ESS) in near future. Tin (IV) oxide, SnO2, is one of highly promising anode candidates due to its high theoretical capacity (782 mAh g−1), abundance, environmental friendliness, and safety with organic electrolytes. However, a rapid capacity fading and poor rate capabilities arising from the large volume expansion and subsequent agglomeration of Sn nanoparticles have been major issues of SnO2. Here, we have synthesized one-dimensional (1D) SnO2-amorphous titanium (IV) oxide NTs (SnO2-a-TiO2 NTs), which allow both facile ionic and electron transport as well as easy penetration of electrolytes. The resultant SnO2-a-TiO2 NTs not only alleviate volume expansion by maintaining their structural integrity but also possess minimal charge transfer resistance even after a number of cycles. SnO2-a-TiO2 NTs exhibit both excellent cycle retention characteristics (1050.2 mAh g−1 after 250 cycles) and outstanding rate capability (522.3 mAh g−1 at a current density of 5000 mA g−1), which is attributed to the introduction of amorphous TiO2 that not only acts as buffer agent for volume changes of SnO2 but also allows fast surface-controlled diffusion process due to its pseudocapacitive charge storage mechanisms.

The utilization of sustainable water electrolysis for hydrogen production is currently limited by sluggish kinetics of the oxygen evolution reaction (OER). The development of stable, highly active, and cost-effective OER catalyst supports would facilitate commercialization of water electrolysis technologies. In this study, we report for the first time the use of metallic cobalt nitride (Co4N) nanofibers (NFs) as highly stable and conductive scaffolds for supporting Ir nanoparticles (NPs). The Ir catalysts supported on Co4N NFs exhibit high OER activity and stability in alkaline media as compared with Ir catalysts supported on other materials (Co3O4 or carbon NFs) and commercial Ir/C. These results are attributed to the (i) efficient charge or mass transport between Ir NPs and metallic one-dimensional (1D) Co4N NFs or interfibers, (ii) maintenance of the active oxidation state (Ir3+) of Ir NPs induced by synergistic charge compensation between catalyst and support during OER, and (iii) long-term stability ...

Nanowires (NWs) synthesized via chemical vapor deposition (CVD) have demonstrated significant improvement in lithium storage performance along with their outstanding accommodation of large volume changes during the charge/discharge process. Nevertheless, NW electrodes have been confined to the research level due to the lack of scalability and severe side reactions by their high surface area. Here, we present nanoporous Ge nanofibers (NPGeNFs) having moderate nanoporosity via a combination of simple electrospinning and a low-energetic zincothermic reduction reaction. In contrast with the CVD-assisted NW growth, our method provides high tunability of macro/microscopic morphologies such as a porosity, length, and diameter of the nanoscale 1D structures. Significantly, the customized NPGeNFs showed a highly suppressed volume expansion of less than 15% (for electrodes) after full lithation and excellent durability with high lithium storage performance over 500 cycles. Our approach offers effective 1D nanostructuring with highly customized geometries and can be extended to other applications including optoelectronics, catalysis, and energy conversion.

A new type of chemiresistor, the impedance-transduced chemiresistor (ITCR), is described for the rapid analysis of glucose. The ITCR exploits porous, high surface area, fluorine-doped carbon nanofibers prepared by electrospinning of fluorinated polymer nanofibers followed by pyrolysis. These nanofibers are functionalized with a boronic acid receptor and stabilized by Nafion to form the ITCR channel for glucose detection. The recognition and binding of glucose by the ITCR is detected by measuring its electrical impedance at a single frequency. The analysis frequency is selected by measuring the signal-to-noise ( S/ N) for glucose detection across 5 orders of magnitude, evaluating both the imaginary and real components of the complex impedance. On the basis of this analysis, an optimal frequency of 13 kHz is selected for glucose detection, yielding an S/ N ratio of 60-100 for [glucose] = 5 mM using the change in the total impedance, Δ Z. The resulting ITCR glucose sensor shows a rapid analysis time (

In the recent times, pseudocapacitive electrode materials have received great attention due to their considerable capability in storing ions at relatively fast charging rates. Among various candidates, niobium (V) pentoxide (Nb2O5) has gained much attraction for lithium-ion batteries (LIBs) due to its insertion/extraction reaction with Li, safe redox potential, and considerably good capacity (about 200 mAhg−1). Nevertheless, low conductivity of Nb2O5 has so far prevented its use as a viable electrode material for LIBs. In this study, we have successfully coated silver (Ag) nanoparticles (NPs) on the surface of one-dimensional orthorhombic Nb2O5 fiber (1D T-Nb2O5) using simple electrospinning processing. Ag NPs coated Nb2O5 fibers (Ag-1D T-Nb2O5) provided faster electron pathways, resulting in much improved capacity at a given current density with superior rate capabilities compared with pristine 1D T-Nb2O5. In addition, 1D T-Nb2O5 was more suitable for coating Ag NPs compared with T-Nb2O5 NPs, where its structural integrity was maintained even after cycling. As a result, effective coating of conductive Ag NPs on the 1D T-Nb2O5 resulted in excellent cycle retention characteristics (179.7 mAhg−1 after 500 cycles at 500 mA g−1) as well as superior rate capabilities (103.6 mAhg−1 at a current density of 5000 mA g−1).

To date, lithium-oxygen batteries (LOBs) using porous carbon materials as the air cathode have been widely studied. However, a fundamental issue of carbon electrode still remains; the carbon surface is unstable and is highly reactive in contact with Li2O2, resulting in the formation of irreversible byproducts (e.g., Li2CO3). To address this issue, we investigated the use of surface protection layers for improving the cycling stability of porous carbon-based LOB cathode. We employed atomic layer deposition (ALD) for conformal coating of two types of overlayers (In2O3 and TiN), i.e., oxide and nitride thin film, on an electrospun carbon nanopaper (CNp) membrane. The LOB cell with In2O3-coated CNp exhibited much enhanced cycling performance (over 140 cycles) compared with pristine CNp and TiN-coated CNp as control samples (less than 60 cycles for both cases). To further improve cell efficiency by reducing overpotentials, the surface of In2O3-coated CNp electrode was functionalized by catalytic RuOx nanoparticles, which enables stable and complete discharging and recharging reactions below 4.2 V for an extended period of 165 cycles. Interestingly, after each discharge, nanosheet-like Li2O2 growth was observed on In2O3-coated CNps, which is advantageous for enhanced cycle life. This work demonstrates that use of a free-standing, high surface area carbon membrane, that is conformally encapsulated by a highly conductive and stable oxide protection layer, is essential for enhanced Li-O2 cell performance by preventing direct contact between underneath carbon and electrolyte.

Efficient electrocatalyst for oxygen reduction reaction (ORR) is an essential component for stable operation of various sustainable energy conversion and storage systems such as fuel cells and metal-air batteries. Herein, we report a facile preparation of meso/macroporous Co and N co-doped carbon nanofibers (Co-Nx@CNFs) as a high performance and cost-effective electrocatalyst toward ORR. Co-Nx@CNFs are simply obtained from electrospinning of Co precursor and bicomponent polymers (PVP/PAN) followed by temperature controlled carbonization and further activation step. The prepared Co-Nx@CNF catalyst carbonized at 700 °C (Co-Nx@CNF700) shows outstanding ORR performance, i.e., a low onset potential (0.941 V) and half wave potential (0.814 V) with almost four-electron transfer pathways ( n = 3.9). In addition, Co-Nx@CNF700 exhibits a superior methanol tolerance and higher stability (>70 h) in Zn-air battery in comparison with Pt/C catalyst (∼30 h). The outstanding performance of Co-Nx@CNF700 catalysts is attributed to i) enlarged surface area with bimodal porosity achieved by leaching of inactive species, ii) increase of exposed ORR active Co-Nx moieties and graphitic edge sites, and iii) enhanced electrical conductivity and corrosion resistance due to the existence of numerous graphitic flakes in carbon matrix.

Facile synthesis of rationally designed structures is critical to realize a high performance electrode for lithium-ion batteries (LIBs). Among different candidates, tin(IV) oxide (SnO2) is one of the most actively researched electrode materials due to its high theoretical capacity (1493 mAh g−1), abundance, inexpensive costs, and environmental friendliness. However, severe capacity decay from the volume expansion and low conductivity of SnO2 have hampered its use as a feasible electrode for LIBs. Rationally designed SnO2-based nanostructures with conductive materials can be an ideal solution to resolve such limitations. In this work, we have successfully fabricated porous SnO2-CuO composite nanotubes (SnO2-CuO p-NTs) by electrospinning and subsequent calcination step. The porous nanotubular structure is expected to mitigate the volume expansion of SnO2, while the as-formed Cu from CuO upon lithiation allows faster electron transport by improving the low conductivity of SnO2. With a synergistic effect of both Sn and Cu-based oxides, SnO2-CuO p-NTs deliver stable cycling performance (91.3% of capacity retention, ∼538 mAh g−1) even after 350 cycles at a current density of 500 mA g−1, along with enhanced rate capabilities compared with SnO2.

To achieve a high reversibility and long cycle life for lithium–oxygen (Li–O2) batteries, the irreversible formation of Li2O2, inevitable side reactions, and poor charge transport at the cathode interfaces should be overcome. Here, we report a rational design of air cathode using a cobalt nitride (Co4N) functionalized carbon nanofiber (CNF) membrane as current collector-catalyst integrated air cathode. Brush-like Co4N nanorods are uniformly anchored on conductive electrospun CNF papers via hydrothermal growth of Co(OH)F nanorods followed by nitridation step. Co4N-decorated CNF (Co4N/CNF) cathode exhibited excellent electrochemical performance with outstanding stability for over 177 cycles in Li–O2 cells. During cycling, metallic Co4N nanorods provide sufficient accessible reaction sites as well as facile electron transport pathway throughout the continuously networked CNF. Furthermore, thin oxide layer (

Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO2)) on metal oxide anodes (such as tin (IV) oxide (SnO2)) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO2 overlayer on SnO2 can have significant influence in the overall parameters of electrochemistry. It is revealed that TiO2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g−1 even at high current density (5000 mA g−1). Surprisingly, it was further discovered that TiO2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO2. The improvements in both ionic and electrical conductivity of TiO2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO2@SnO2, which demonstrates that TiO2 overlayer results in homogeneous and thinner interphase layer compared with SnO2 NTs.

The image quality of an in-vehicle black box camera is often degraded by the reflections of internal objects, dirt, and dust on the windshield. In this paper, we propose a novel algorithm that simultaneously removes the reflections and small dirt artifacts from in-vehicle black box videos under fast forward camera motion. The algorithm exploits the spatiotemporal coherence of the reflection and dirt, which remain stationary relative to the fast-moving background. Unlike previous algorithms, the algorithm first separates stationary reflection and then restores the background scene. To this end, we propose an average image prior, thereby imposing spatiotemporal coherence. The separation model is a two-layer model composed of stationary and background layers, where different gradient sparsity distributions are utilized in a region-based manner. Motion compensation in postprocessing is proposed to alleviate layer jitter due to vehicle vibrations. In evaluation experiments, the proposed algorithm successfully extracts the stationary layer from several real and synthetic black box videos.

The conventional use of metallic current collector in an electrochemical cell results in decreased loading of active materials and hence limited capacity in consideration of all the inactive current collector components. In response to this trend, a number of conductive, free-standing materials have been proposed as electrodes, which would act as both current collector and active materials. Here, in this study, we have firstly developed the cross-aligned carbon nanofiber (CA-CNF) for efficient Li storage, especially at high current densities. Using the insulating block electrospinning, the nanofibers can be aligned in a certain direction, where it is viable to fabricate cross-aligned nanofibers in a cost-effective and scalable manner. Attributed to faster kinetics and regular electron pathway arising from CA-CNF, it exhibits an excellent high-rate cyclability (259.4 mAh g−1 at a current density of 3000 mA g−1). This work builds up a milestone in suggesting a cross-aligned carbon nanofibrous network as efficient Li storage, which can also be applied to various electrode materials embedded cross-aligned conductive composite materials.

For the proliferation of the supercapacitor technology, it is essential to attain superior areal and volumetric performance. Nevertheless, maintaining stable areal/volumetric capacitance and rate capability, especially for thick electrodes, remains a fundamental challenge. Here, for the first time, a rationally designed porous monolithic electrode is reported with high thickness of 800 µm (46.74 mg cm-2 , with high areal mass loading of NiCo2 S4 6.9 mg cm-2 ) in which redox-active Ag nanoparticles and NiCo2 S4 nanosheets are sequentially decorated on highly conductive wood-derived carbon (WC) substrates. The hierarchically assembled WC@Ag@NiCo2 S4 electrode exhibits outstanding areal capacitance of 6.09 F cm-2 and long-term stability of 84.5% up to 10 000 cycles, as well as exceptional rate capability at 50 mA cm-2 . The asymmetric cell with an anode of WC@Ag and a cathode of WC@Ag@NiCo2 S4 delivers areal/volumetric energy density of 0.59 mWh cm-2 /3.93 mWh cm-3 , which is much-improved performance compared to those of most reported thick electrodes at the same scale. Theoretical calculations verify that the enhanced performance could be attributed to the decreased adsorption energy of OH- and the down-shifted d-band of Ag atoms, which can accelerate the electron transport and ion transfer.

Keeping outstanding electrochemical performance under high mass loading is critical to develop functional thick electrodes. Here, we report a high phosphorus-doped wood-derived carbon thick electrode for supercapacitor via phytic acid treatment, which can form hydrogen bonds with cellulose molecules in the wood. The content of phosphorus reaches up to 9.24 at% in carbonized wood with P-doping (CW-P-9.24), higher than most previously reported P-doped carbonaceous materials. CW-P-9.24 electrode (800 μm, 17.17 mg cm−2) exhibits greatly improved electrochemical performance, especially in energy density and cyclic stability. Significantly, the symmetrical supercapacitor device exhibits high areal and specific capacitance of 4.7 F cm−2 and 206.5 F g−1 at 1.0 mA cm−2 with prominent retention of 90.5% through the long-term cycling at 20 mA cm−2 for 20,000 cycles, and 0.94 mW h cm−2 (41.2 Wh kg−1) at power density of 0.6 mW cm−2 (26.3 W kg−1), and possesses excellent volumetric capacitance and energy density of 29.3 F cm−3 and 5.8 Wh cm−3, respectively. The outstanding performance can be attributed to the excellent hierarchical structure, low tortuosity, and high phosphorus doping with fast accessible channels at high current density. The extraordinary performance of CW-P has been elucidated by density functional theory calculations, which confirm the enhanced activity by P-doping. These results demonstrate that the CW-P electrode is promising for practical application in energy storage devices and encourage more investigations for thick electrode.

The conversion reaction is important in lithium-ion batteries because it governs the overall battery performance, such as initial Coulombic efficiency, capacity retention, and rate capability. Here, we have demonstrated in situ observation of the complete conversion reaction and agglomeration of nanoparticles (NPs) upon lithiation by using graphene liquid cell transmission electron microscopy. The observation reveals that the Sn NPs are nucleated from the surface of SnO2, followed by merging with each other. We demonstrate that the agglomeration has a stepwise process, including rotation of a NP, formation of necks, and subsequent merging of individual NPs.

We report photoelectrochemical hydrogen evolution reaction using a Cu2O-based photocathode with a layer doped with Zn ions. The doping results in the shift of the onset flat-band potential of the photocathode, likely a consequence of maximized band-bending in the Cu2O/Zn : Cu2O heterojunction. Systematic electrochemical analysis reveals that expansion of depletion region is responsible for the enhanced photoelectrochemical performance, e.g., the increase of photocurrent and reduced internal resistance.

Ultra-stable pseudocapacitive electrodes for lithium-ion batteries (LIBs) are increasing in demand as highly sustainable energy storage system with excellent charge transport is important. The establishment of facile, controllable, and scalable synthesis of pseudocapacitive electrode materials is an attractive solution to realize such objectives. Here, we have successfully fabricated mesoporous orthorhombic Nb2O5 nanofibers (m-T-Nb2O5 NFs) by simple single-spinneret electrospinning followed by calcination at 600 °C. As-formed m-T-Nb2O5 NFs exhibit high surface area (23.7 m2 g−1) and a number of mesopores in the vacant sites where organic polymer was once decomposed. Such rationally designed m-T-Nb2O5-NFs allow facile Li ion and electron transport, with pseudocapacitive behavior. Arising from the high surface area coupled with mesopores in-between the Nb2O5 nanograins, it exhibits ultra-long cycle retention (a capacity of ∼160 mAh g−1 at 500 mA g−1 after 2000 cycles and ∼88 mAh g−1 at 3000 mA g−1 after 5000 cycles) and higher rate capability (∼70 mAh g−1 at 5000 mA g−1). Such cycle retention characteristics of m-T-Nb2O5-NFs are at least 100-fold slower capacity decay compared with previously reported one-dimensional (1D) Nb2O5 nanostructures and even superior or comparable to recently reported Nb2O5-graphene composite materials.

The external example-driven single image super-resolution (SISR) method that uses a deep convolutional neural network (CNN) has exhibited superior performance as compared to previously developed SISR methods. However, the advantages of jointly using external and internal examples on a deep CNN framework have not been sufficiently investigated. In this letter, we present a novel method for single image super-resolution by exploiting a complementary relation between external and internal example-based SISR methods. The proposed deep CNN model consists of two subnetworks, a global residual network and a self-residual network, to utilize the advantages of both external and internal examples. In contrast with conventional joint SISR methods, the proposed method is the first deep CNN-based SISR method that does not require a retraining process, which tends to be inefficient. The proposed method outperformed existing methods in both quantitative and qualitative evaluations.

The increase of surface area and the functionalization of catalyst are crucial to development of high-performance semiconductor metal oxide (SMO) based chemiresistive gas sensors. Herein, nanoscale catalyst loaded Co3O4 hollow nanocages (HNCs) by using metal–organic framework (MOF) templates have been developed as a new sensing platform. Nanoscale Pd nanoparticles (NPs) were easily loaded on the cavity of Co based zeolite imidazole framework (ZIF-67). The porous structure of ZIF-67 can restrict the size of Pd NPs (2–3 nm) and separate Pd NPs from each other. Subsequently, the calcination of Pd loaded ZIF-67 produced the catalytic PdO NPs functionalized Co3O4 HNCs (PdO–Co3O4 HNCs). The ultrasmall PdO NPs (3–4 nm) are well-distributed in the wall of Co3O4 HNCs, the unique structure of which can provide high surface area and high catalytic activity. As a result, the PdO–Co3O4 HNCs exhibited improved acetone sensing response (Rgas/Rair = 2.51–5 ppm) compared to PdO–Co3O4 powders (Rgas/Rair = 1.98), Co3O4 HNCs...

Huge volume expansion during discharge is always a critical problem of high capacity conversion anodes for next generation lithium-ion (Li-ion) batteries. Although extensive efforts have been devoted to controlling the volume expansion using nanostructuring and surface engineering till now, more simple and facile approaches have to be considered due to the complicated and inefficient synthetic methods. Here, we report a straightforward synthesis of Ag coated ZnCo2O4 porous hollow spheres (ZnCo2O4@Ag HSs): (i) immobilization of metal–organic frameworks (MOFs) including Zn and Co metal nodes onto polystyrene sphere templates, (ii) calcination (∼450 °C) for the removal of core polystyrene sphere templates and oxidation of MOFs to produce a mesoporous ZnCo2O4 HSs, and (iii) a subsequent Ag-mirror reaction for 10 min, resulting in the formation of ZnCo2O4@Ag HSs. This porous hollow morphology not only effectively relieves the strain stemming from the volume expansion of transition metals, but also facilitates the efficient electron transport for Li+ diffusion by shortening the Li-ion diffusion path during a lithiation/delithiation process. Moreover, uniformly decorated Ag nanoparticles are beneficial to the formation of a stable solid electrolyte interface (SEI) layer as well as an increased electrical conductivity of ZnCo2O4. The MOF derived porous ZnCo2O4@Ag HSs exhibited remarkably stable cycling performance (a capacity value of 616 mA h g−1 after 900 cycles at a current density of 1 A g−1) and an excellent capacity retention of 80% at a very high current density of 20.0 A g−1.

Recently, gallium (Ga), one of the liquid metals (LMs), has been explored with special attention because of its liquid phase nature as a self-healing agent and Li storage characteristics. The current challenge that restricts the practical use of Ga is handling Ga easily without loss and understanding its reaction behavior in Li-ion batteries. One solution that helps to address the problem associated with liquid phases is to make solid phases such as gallium oxides and nitrides as starting materials for a stable conversion reaction. Here, we have successfully incorporated GaN nanoparticles into carbon confiners [1D carbon nanofibers (CNFs) with the outermost carbon coating layer] as an anode for the Li-ion battery. By preserving liquid Ga derived from GaN after the conversion reaction in conductive walls, long-term cycling performance (over 5000 cycles) is achievable. This work provides an insight into the LM-relevant materials/carbon composite in the area of the rechargeable battery.

Alloys are recently receiving considerable attention in the community of rechargeable batteries as possible alternatives to carbonaceous negative electrodes; however, challenges remain for the practical utilization of these materials. Herein, we report the synthesis of germanium-zinc alloy nanofibers through electrospinning and a subsequent calcination step. Evidenced by in situ transmission electron microscopy and electrochemical impedance spectroscopy characterizations, this one-dimensional design possesses unique structures. Both germanium and zinc atoms are homogenously distributed allowing for outstanding electronic conductivity and high available capacity for lithium storage. The as-prepared materials present high rate capability (capacity of ~ 50% at 20 C compared to that at 0.2 C-rate) and cycle retention (73% at 3.0 C-rate) with a retaining capacity of 546 mAh g−1 even after 1000 cycles. When assembled in a full cell, high energy density can be maintained during 400 cycles, which indicates that the current material has the potential to be used in a large-scale energy storage system., Alloy anode materials are receiving renewed interest. Here the authors show the design of Ge-Zn nanofibers for lithium ion batteries. Featured by a homogeneous composition at the atomic level and other favorable structural attributes, the materials allow for impressive electrochemical performance.

Stable electrode materials with guaranteed long-term cyclability are indispensable for advanced lithium-ion batteries. Recently, delafossite CuFeO

Recently, quantum dots based light-emitting diodes (QLEDs) have received huge attention due to the properties of quantum dots (QDs), such as high photoluminescence quantum yield (PLQY) and narrow emission. To improve the performance of QLEDs, reducing non-radiative energy transfer is critical. So far, most conventional methods required additional chemical treatment like giant shell and/or ligands exchange. However that triggers unsought shifted emission or reduced PLQY of QDs. In this work, we have firstly suggested a novel approach to improve the efficiency of QLEDs by introducing inorganic nanoparticles (NPs) spacer between QDs, without additional chemical treatment. As ZnS NPs formed a mixture layer with QDs, the energy transfer was reduced and the distance between the QDs increased, leading to improved PLQY of mixture layer. As a result, current efficiency (CE) of the QLED device was improved by twice compared with one using only QDs layer. This is an early report on utilizing ZnS NPs as an efficient spacer, which can be utilized to other compositions of QDs.

In this work, we introduce the preparation of graphene liquid cells (GLCs), encapsulating both electrode materials and organic liquid electrolytes between two graphene sheets, and the facile synthesis of one-dimensional nanostructures using electrospinning. The GLC enables in situ transmission electron microscopy (TEM) for the lithiation dynamics of electrode materials. The in situ GLC-TEM using an electron beam for both imaging and lithiation can utilize not only realistic battery electrolytes, but also the high-resolution imaging of various morphological, phase, and interfacial transitions.

Carbon nanosheets (CNSs) have been used in various applications, ranging from energy storage to drug delivery. CNSs are conventionally synthesized by chemical vapor deposition, but their high cost and non-scalability prompted the development of alternative synthesis routes. More scalable methods such as the sol-gel process still suffer from its complicated synthetic steps with delicate conditions. Here, we demonstrate for the first time a unique top-down synthesis of CNSs from aronia fruit powder, which is simple, scalable, and cost-effective. Aronia-derived CNS can be fabricated at various heating temperatures (500, 700, and 900 °C) and under different atmospheres (N2/H2 and NH3), which can easily tune the overall physicochemical properties of the CNS. We evaluated the electrochemical performance of the CNS for potential applications in Li- and K-ion batteries, in which the CNS showed stable electrochemical performance even at a high current density (1000 mA g−1). Because of the high-throughput nature of this synthetic approach, the aronia-derived CNSs could be very useful in developing novel applications at an industrial scale.

Wearable energy storage system must maintain robust electrochemical performance under severe mechanical and chemical deformations. Here, we demonstrate wearable supercapacitor system assembled with electrodes composed of one-step carbonized plant epidermis and gelatin based hydrogel electrolyte which possesses high electrochemical performance and superior reliability under ambient condition. The carbonized mulberry paper (MP) was used as an electrode to achieve improved volumetric energy density as well as mechanical-chemical reliability (e.g. mechanical toughness and acid resistance). Rationally designed active materials composed of vertically grown WO3 NRs and reduced graphene oxide (rGO) anchored on MP, were employed for developing organism epidermis based supercapacitor. Such electrode exhibits high volumetric energy and power densities of 30.28 mWh cm−3 and 7.67 W cm−3, retaining the volumetric capacitance of 96.0% even after 110,000 charge-discharge cycles. As the final step, we employed the gelatin based electrolyte with high ionic conductivity to solve evaporation and leakage problems of conventional electrolytes. Organism epidermis based supercapacitor integrated with hydrogel electrolyte showed high electrochemical performance and long-term stability under ambient condition even after exposure to acid, demonstrating its gareat suitability as a large-scale wearable energy storage system.

Among various natural wastes, gum wastes pose major issues, as they are unusable and hard to be disposed due to their acidic and sticky nature. Herein, a rational synthetic strategy is employed to transform various kinds of gum wastes into micron-sized carbon, which also exhibit high tap density (1.4–1.7 g cm−3) desirable for practical application in lithium-ion batteries (LIBs). Gum karaya (GK) micron-size functional carbon (GKMFC) exhibits the most outstanding electrochemical performance, with a volumetric capacity of 175.4 mAh cm−3 at a current density of 3000 mA g−1 for 5000 cycles, and possesses ultra-stable high-rate cyclability (a capacity decay of only 0.001881% per cycle). Additional electrochemical analyses reveal that GKMFC exhibits stable structural integrity as well as minimal cell resistance even after cycling, showing its practical application as viable electrode for LIBs. This work sheds light on utilizing high tap density carbon from gum wastes for LIBs, which can also be applicable to other natural wastes and carbon.

Formation of stable solid electrolyte interphase (SEI) layer is critical to outstanding performance of energy storage devices, because it acts as a passive layer that allows facile transport of ions but forbids electron transport between the electrolyte and electrode. Although much study has been devoted to investigate the morphology and structure of SEI layer using a myriad of analytical devices on past decades, the direct observation of SEI layer on a real time scale has remained as a formidable challenge. In addition, it has been difficult to observe both the decomposition of electrolytes and formation process of stable SEI layer at nanometer scale. Here we utilize in situ transmission electron microscopy (TEM) using graphene liquid cell (GLC) to realize the observation of stable SEI layer formation in a sequential time scale. Upon e− beam irradiation, Li salts in the electrolytes react with reduced electrolytes and form gel-like agglomerates, which are deposited on the surface of the active material as a passivation layer and later stabilized to become more uniform in overall thickness. Additionally, growth dynamics of stable SEI layer were suggested, where the deposition of decomposed electrolytes eventually result in relatively uniform SEI layer. This paper demonstrates that it is possible to observe not only the formation of non-crystalline SEI layer but also the movement of decomposed electrolytes onto the surface of active materials which account for broader understanding of SEI layer, and has the potential to detect important interfacial phenomena in electrochemical devices that were overlooked so far.

Ultra thin TiO2 layer (2 nm)-coated SnO2 nanotubes (NTs) wrapped by reduced graphene oxide (rGO) sheets (SnO2@TiO2@rGO) were synthesized as high capacity anode materials for lithium-ion batteries. The rationally designed anodes exhibited superior rate capability while maintaining a high discharge capacity of over 840 mA h g−1 at a current density of 500 mA g−1 after 50 cycles.

Abstact Water energy harvesters have received significant attention, due to wide distribution of water, simple device fabrication, and environmentally-friendly nature. Herein, we report a reliable water energy harvester by employing a composite that consists of synthesized micron-sized carbon as physical anchor, poly(styrene sulfonic acid) (PSSA) as proton supplier, and polyacrylic acid/carboxymethyl cellulose (PAA/CMC) as network binder. Single energy harvester fabricated using slurry casting at low temperature shows electrical output performance with output voltage of 0.4 V and current of 0.45 μA. Especially, the material combination enables both chemical and physical linkage and in turn, reliable electricity production was demonstrated, showing stable performance over 14 days without output degradation. Furthermore, the power level of energy harvesters was simply extended to drive commercial light emitting diodes (LEDs). Consequently, this approach introduced here is well-suited for developing a device with excellent electrical, structural, and chemical properties and the composite combination greatly broadens material choices that can be applied to develop sustainable water energy harvesters.

Facile synthesis of rationally designed nanostructured electrode materials with high reversible capacity is highly critical to meet ever-increasing demands for lithium-ion batteries. In this work, we employed defect engineering by incorporating metal organic framework (MOF) templates into one-dimensional nanostructures by simple electrospinning and subsequent calcination. The introduction of Co-based zeolite imidazole frameworks (ZIF-67) resulted in abundant oxygen vacancies, which induce not only more active sites for Li storage but also enhanced electrical conductivity. Moreover, abundant mesoporous sites are formed by the decomposition of ZIF-67, which are present both inside and outside the resultant SnO2–Co3O4 nanofibers (NFs). Attributed to the creation of vacancy sites along with the synergistic effects of SnO2 and Co3O4, SnO2–Co3O4 NFs exhibit an excellent reversible capacity for 300 cycles (1287 mA h g–1 at a current density of 500 mA g–1) along with superior rate capabilities and improved initia...

We trace Sn nanoparticles (NPs) produced from SnO2 nanotubes (NTs) during lithiation initialized by high energy e-beam irradiation. The growth dynamics of Sn NPs is visualized in liquid electrolytes by graphene liquid cell transmission electron microscopy. The observation reveals that Sn NPs grow on the surface of SnO2 NTs via coalescence and the final shape of agglomerated NPs is governed by surface energy of the Sn NPs and the interfacial energy between Sn NPs and SnO2 NTs. Our result will likely benefit more rational material design of the ideal interface for facile ion insertion.

Flame-retardant, flexible polymer thin film and coating materials are in large demand for various applications. Three approaches have been attempted: inherently fire-retardant polymers; chemically modified polymers; and the addition of fire retardants as additives for polymers. The first two approaches are based on specific polymers, limiting their wide applications. The last approach provides great flexibility in designing materials with multifunctional properties. Herein, we report the fabrication of a flexible vermiculite–polymer hybrid film with very low flammability through photo-cross-linking of polyethylene glycol network incorporating micronized vermiculite particles. Vermiculite is a thermally insulating agent that can withstand flame up to about 1200 °C. The film fabrication process is very simple, time-efficient, and thickness-controllable. Despite quick processing of the film, vermiculite particles are uniformly distributed within the polymer network. Direct fire testing proves that, at a vermiculite concentration of about 75 wt%, the films of 20 μm thick can withstand actual fire for more than a minute. Without vermiculite, the polymer film is burnt out immediately when in contact with flame. This study demonstrates that a vermiculite–polymer hybrid film, though it is relatively thin and highly flexible, can suppress the heat flow without decomposition for more than just a brief moment when in direct contact with flame.

To achieve a high reversibility and long cycle life for lithium-oxygen (Li-O

Room-temperature (RT) operation sensors are constantly in increasing demand because of their low power consumption, simple operation, and long lifetime. However, critical challenges such as low sensing performance, vulnerability under highly humid state, and poor recyclability hinder their commercialization. In this work, sub-10 nm hollow, bimetallic Pt–Ag nanoparticles (NPs) were successfully formed by galvanic replacement reaction in bioinspired hollow protein templates and sensitized on the multidimensional SnO2–WO3 heterojunction nanofibers (HNFs). Formation of hollow, bimetallic NPs resulted in the double-side catalytic effect, rendering both surface and inner side chemical reactions. Subsequently, SnO2–WO3 HNFs were synthesized by incorporating 2D WO3 nanosheets (NSs) with 0D SnO2 sphere by c-axis growth inhibition effect and fluid dynamics of liquid Sn during calcination. Hierarchically assembled HNFs effectively modulate surface depletion layer of 2D WO3 NSs by electron transfers from WO3 to SnO2 ...

The increase of surface area and the functionalization of catalyst are crucial to development of high-performance semiconductor metal oxide (SMO) based chemiresistive gas sensors. Herein, nanoscale catalyst loaded Co

Safe and long cycle life electrode materials for lithium-ion batteries are significantly important to meet the increasing demands of rechargeable batteries. Niobium pentoxide (Nb