Carbon-based flexible self-supporting cathode for lithium-sulfur batteries:Progress and perspective

The flexible self-supporting electrode can maintain good mechanical and electrical properties while retaining high specific capacity,which meets the requirements of flexible batteries.Lithium-sulfur batteries(LSBs),as a new generation of energy storage system,hold much higher theoretical energy density than traditional batteries,and they have attracted extensive attention from both the academic and industrial communities.Selection of a proper substrate material is important for the flexible self-supporting electrode.Carbon materials,with the advantages of light weight,high conductivity,strong structural plasticity,and low cost,provide the electrode with a large loading space for the active material and a conductive network.This makes the carbon materials meet the mechanical and electrochemical requirements of flexible electrodes.In this paper,the commonly used fabrication methods and recent research progresses of the flexible self-supporting cathode with a carbon material as the substrate are introduced.Various sulfur loading methods are summarized,which provides useful information for the structural design of the cathode.As the first review article of the carbon-based flexible self-supporting LSB cathodes,it provides valuable guidance for the researchers working in the field of LSB.

Self-supporting and hierarchically porous Ni_(x)Fe-S/NiFe_(2)O_(4) heterostructure as a bifunctional electrocatalyst for fluctuating overall water splitting

Stable non-noble metal bifunctional electrocatalysts are one of the challenges to the fluctuating overall water splitting driven by re-newable energy.Herein,a novel self-supporting hierarchically porous Ni_(x)Fe-S/NiFe_(2)O_(4) heterostructure as bifunctional electrocatalyst was constructed based on porous Ni-Fe electrodeposition on three-dimensional(3D)carbon fiber cloth,in situ oxidation,and chemical sulfuration.Results showed that the Ni_(x)Fe-S/NiFe_(2)O_(4) heterostructure with a large specific surface area exhibits good bifunctional activity and stability for both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)because of the abundance of active sites,synergistic effect of the heterostructure,superhydrophilic surface,and stable,self-supporting structure.The results further confirmed that the Ni_(x)Fe-S phase in the heterostructure is transformed into metal oxides/hydroxides and Ni_(3)S_(2) during OER.Compared with the commercial 20wt%Pt/C||IrO_(2)-Ta_(2)O_(5) electrolyzer,the self-supporting Ni1/5Fe-S/NiFe_(2)O_(4)||Ni1/2Fe-S/NiFe_(2)O_(4) electrolyzer exhibits better stability and lower cell voltage in the fluctu-ating current density range of 10-500 mA/cm^(2).Particularly,the cell voltage of Ni1/5Fe-S/NiFe_(2)O_(4)||Ni1/2Fe-S/NiFe_(2)O_(4) is only approximately 3.91 V at an industrial current density of 500 mA/cm^(2),which is lower than that of the 20wt%Pt/C||IrO_(2)-Ta_(2)O_(5) electrolyzer(i.e.,approximately 4.79 V).This work provides a promising strategy to develop excellent bifunctional electrocatalysts for fluctuating overall water splitting.

Self-supporting NiFe LDH-MoS_(x) integrated electrode for highly efficient water splitting at the industrial electrolysis conditions

Developing effective and practical electrocatalyst under industrial electrolysis conditions is critical for renewable hydrogen production.Herein,we report the self-supporting NiFe LDH-MoS_(x) integrated electrode for water oxidation under normal alkaline test condition(1 M KOH at 25℃)and simulated industrial electrolysis conditions(5 M KOH at 65℃).Such optimized electrode exhibits excellent oxygen evolution reaction(OER)performance with overpotential of 195 and 290 mV at current density of 100 and 400 mA·cm^(-2) under normal alkaline test condition.Notably,only over-potential of 156 and 201 mV were required to achieve the current density of 100 and 400mA·cm^(-2) under simulated industrial electrolysis conditions.No significant degradations were observed after long-term durability tests for both conditions.When using in two-electrode system,the operational voltages of 1.44 and 1.72 V were required to achieve a current density of 10 and 100 mA·cm^(-2) for the overall water splitting test(NiFe LDH-MoS_(x)/INF||20%Pt/C).Additionally,the operational voltage of employing NiFe LDH-MoS_(x)/INF as both cathode and anode merely require 1.52 V at 50mA·cm^(-2) at simulated industrial electrolysis conditions.Notably,a membrane electrode assembly(MEA)for anion exchange membrane water electrolysis(AEMWEs)using NiFe LDH-MoS_(x)/INF as an anode catalyst exhibited an energy conversion efficiency of 71.8%at current density of 400 mA·cm^(-2)in 1 M KOH at 60℃.Further experimental results reveal that sulfurized substrate not only improved the conductivity of NiFe LDH,but also regulated its electronic configurations and atomic composition,leading to the excellent activity.The easy-obtained and cost-effective integrated electrodes are expected to meet the large-scale application of industrial water electrolysis.

Topology Optimization of Self-Supporting Structures for Additive Manufacturing with Adaptive Explicit Continuous Constraint

The integration of topology optimization(TO)and additive manufacturing(AM)technologies can create significant synergy benefits,while the lack of AM-friendly TO algorithms is a serious bottleneck for the application of TO in AM.In this paper,a TO method is proposed to design self-supporting structures with an explicit continuous self-supporting constraint,which can be adaptively activated and tightened during the optimization procedure.The TO procedure is suitable for various critical overhang angles(COA),which is integrated with build direction assignment to reduce performance loss.Besides,a triangular directional self-supporting constraint sensitivity filter is devised to promote the downward evolution of structures and maintain stability.Two numerical examples are presented;all the test cases have successfully converged and the optimized solutions demonstrate good manufacturability.In the meanwhile,a fully self-supporting design can be obtained with a slight cost in performance through combination with build direction assignment.

Self-supporting and dual-active 3D Co-S nanosheets constructed by ligand replacement reaction from MOF for rechargeable Al battery

Metal sulfides with high theoretical capacities are expected as promising cathode materials of Al batteries(AIBs). However, powdery active materials are mainly synthesized and loaded on current collector by insulating binder without capacity. Meanwhile, S as inert element in metal sulfides can not usually provide capacity. So, powdery metal sulfides only exhibit limiting practical capacity and poor cycling stability due to weak conductivity and low mass utilization. Herein, the novel self-supporting and dual-active Co-S nanosheets on carbon cloth (i.e. Co-S/CC) with hierarchically porous structure are constructed as cathode of AIBs. Co-S nanosheets are derived from ZIF-67 nanosheets on CC by a facile ligand replacement reaction. As a result, the binder-free Co-S/CC cathode with good conductivity delivers excellent initial discharge capacity of 383.4 m Ah g^(-1)(0.211 m Ah cm^(-2)) at current density of 200 m A g^(-1)and maintain reversible capacity of 156.9 m Ah g^(-1)(0.086 m Ah cm^(-2)) with Coulombic efficiency of 95.8% after 500 cycles,which are much higher than those of the traditional slurry-coating cathodes. Both Co and S as active elements in Co-S/CC contribute to capacity, which leads to a high mass utilization. This work provides a significant strategy for the construction of self-supporting metallic cathode for advanced high-energy density Al battery.

Research on self-supporting T-shaped gate structure of GaN-based HEMT devices

A self-supporting T-shaped gate(SST-gate) GaN device and process method using electron beam lithography are proposed.An AlGaN/GaN high-electron-mobility transistor(HEMT) device with a gate length of 100 nm is fabricated by this method.The current gain cutoff frequency(f_(T)) is 60 GHz,and the maximum oscillation frequency(f_(max)) is 104 GHz.The current collapse has improved by 13% at static bias of(V_(GSQ),V_(DSQ))=(-8 V,10 V),and gate manufacturing yield has improved by 17% compared with the traditional floating T-shaped gate(FT-gate) device.

Synthesis of Zeolite LTN-(SOD) Self-Supporting Membranes from SiO2-Rich Industrial Waste

Synthesis of zeolite LTN (“Linde Type N”) was investigated under insertion of a SiO2-rich filtration residue (FR) from waste water cleaning of the silane production. A new synthesis procedure was therefore developed applying a flotation mechanism with the aim to grow LTN in form of thin membrane like sheets. Preparation starts with preactivation of FR by slurrying first in alkaline solution, followed by an addition of aluminate solution and citric acid. The latter was added as suitable chelating agent for the initiation of the flotation process. In the course of these experiments, we succeeded in synthesizing zeo-lite LTN with more or less zeolite SOD as byproduct in the form of a stable compact membrane-like layer at low temperature of 60℃. The crystallization was performed under isotherm static conditions in an open reaction system without addition of organic templates as structure directing agents (OSDA’s). FR was utilized as a total substitute of sodium silicate in all experiments and an expansive pre-treatment procedure like calcinations was not needed. Furthermore, membrane formation with LTN of usual synthesis needs chemically functionalized supports. In contrast self-supporting membranous LTN layers were grown for the first time in the present study.

Study on the Self-supporting Logistics Mode based on B2C E-commerce Enterprises

Taking B2C E-commerce enterprises as the center, it can be divided into a set of logistics activities upstream supply chain logistics producer to B2C e-commerce enterprises, and the B2C e-commerce enterprise logistics to client consumer, and the paper focuses on the study of self-supporting logistics for the E-commerce enterprise. According to the development status of current B2C electronic commerce enterprise in our country and logistics, the paper study B2C electric business enterprise how to correctly choose the logistics mode and how to promote the business logistics operation level.

Layer-by-layer assembly of long-afterglow self-supporting thin films with dual-stimuli-responsive phosphorescence and antiforgery applications

The assembly of thin films （TFs） having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors, anti-counterfeiting materials, and information-encryption systems. However, such films are limited compared with their powder and solution counterparts. In this study, by exploiting the self-organization of phosphors in the two-dimensional （2D） galleries between clay nanosheets, we developed a method for the ordered assembly of long-afterglow TFs by utilizing a hydrogen-bonding layer-by-layer （LBL） process. Compared with the pristine powder, the TFs exhibit high polarization and up-conversion room-temperature phosphorescence （RTP）, as well as enhanced quantum yields and luminescence lifetimes, allowing them to be used as room-temperature phosphorescent sensors for humidity and oxygen. Moreover, modified clay-based hybrids with multicolor RTP can serve as anti-counterfeiting marks and triple-mode 2D barcode displays. We anticipate that the LBL assembly process can be extended to the fabrication of other inorganic--organic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforgery applications.

A Self-supporting,Surface Carbonized Filter Paper Membrane for Efficient Water-in-Oil Emulsion Separation

Due to the important role of oil source in our life,the separation of water-in-oil emulsion is urgent and necessary.Membrane seperation technology has been an efficient and widely used method in separating oil-water separation.Herein,we report a versatile approach to fabricate surface carbonized membranes with self-standing property from biomass-derived precursor by synergistic charring of phytic acid,arginine and filter paper.The obtained membrane exhibited superhydrophobicity in oil,excellent fouling resistance,and self-supporting ability.The membrane can be cycle-used at least 12 times with high permeation flux(up to 1380 L·m^(-2)·h^(-1))and separation efficiency(up to 99.4%).

Self-supporting hierarchically micro/nano-porous Ni_(3)P-Co_(2)P-based film with high hydrophilicity for efficient hydrogen production

Designing efficient and stable non-precious metal HER(hydrogen evolution reaction)electrocatalysts with high large current density adaptability is significant for industrial application of hydrogen production by water electrolysis.Herein,a facile strategy was developed to construct a multi-phase Ni3 P-Co_(2)P-(Ni-Co)film with self-supporting hierarchically micro/nano-porous structure by using bubble template method electrodeposition of self-supporting micro-porous Ni Co P film,oxygen-free annealing for phase separation producing Ni_(3)P-Ni-Co_(2)P-Co structure,and acid etching for constructing surface nano-porous structure.The effective active sites for HER was significantly increased due to the hierarchically micro/nano-porous structure,which not only enlarged the surface roughness,but enhanced the bubble detachment by improving the hydrophilicity.Meanwhile,the HER electrolysis durability was improved benefiting from the Ni_(3)P-Co_(2)P phases with high corrosion resistance(especially in acid solution)and the self-supporting film structure without binder.Consequently,the Ni Co P-OA-AE film exhibited high HER catalytic performance,which delivered a current density of 10 m A cm^(-2)at a low overpotential of 42.9 and 39.7 m V in 1 M KOH and 0.5 M H_(2)SO_(4),respectively.It also possessed high long-term electrolysis durability,and the cell voltage of water electrolysis using self-supporting porous Ni Co P-OA-AE||Ir O_(2)-Ta_(2)O_(5) electrolyzer at 500 m A cm^(-2)for 250 h in 0.5 M H_(2)SO_(4 )is only 2.9 V.

Nickel-decorated TiO2 nanotube arrays as a self-supporting cathode for lithium-sulfur batteries

Lithium-sulfur batteries are considered to be one of the strong competitors to replace lithium-ion batteries due to their large energy density.However,the dissolution of discharge intermediate products to the electrolyte,the volume change and poor electric conductivity of sulfur greatly limit their further commercialization.Herein,we proposed a self-supporting cathode of nickel-decorated TiO2 nanotube arrays(TiO2 NTs@Ni)prepared by an anodization and electrodeposition method.The TiO2 NTs with large specific surface area provide abundant reaction space and fast transmission channels for ions and electrons.Moreover,the introduction of nickel can enhance the electric conductivity and the polysulfide adsorption ability of the cathode.As a result,the TiO2 NTs@Ni-S electrode exhibits significant improvement in cycling and rate performance over TiO2 NTs,and the discharge capacity of the cathode maintains 719 mA·h·g−1 after 100 cycles at 0.1 C.

Visible Light and Temperature Regulated Reflection Colors in Self-supporting Cholesteric Liquid Crystal Physical Gels

Photo-responsive cholesteric liquid crystals(CLCs)have attracted much attention in recent years due to their wide applications in filters,tun able optical lasers,dyn amic display devices,etc.However,UV light is usually used as the exter nal stimulus source,which is not envir on ment-frie ndly enough.On the other hand,the mecha nical properties of CLCs are not strong eno ugh for these practical applications.Therefore,it still remains a challenge to endow the CLCs with visible light response and high mechanical properties at the same time.Herein,an axially chiral tetra-fluorinated binaphthyl azobenzene gelator(S-4F-AG)is synthesized.Upon 550 and 450 nm light irradiations,S-4F-AG exhibits excellent photo-switchable behaviors.Notably,the maximum con tent of c/s-isomer and its half-life are as high as 35%and 89 h in acet on itrile,respectively.A self-supporting CLC physical gel with a storage modulus around 104 Pa can be obtained when 3wt%S-4F-AG and 12wt%binaphthyl azobenzene derivative(dopant 2)are co-doped into a nematic LC host P0616A.This CLC physical gel exhibits a temperature-driven blue,green,and red reflection colors reversibly.Importantly,such three primary RGB colors can also be realized by adjusting the exposure time of 550 nm green light.This work lays a solid foundation for the applications ranging from information storage to high-tech anticounterfeit.

Constructing self-supporting surfaces with planar quadrilateral elements

We present a simple yet effective method for constructing 3D self-supporting surfaces with planar quadrilateral(PQ)elements.Starting with a triangular discretization of a self-supporting surface,we firstcompute the principal curvatures and directions of each triangular face using a new discrete differential geometryapproach,yielding more accurate results than existing methods.Then,we smooth the principal direction field to reduce the number of singularities.Next,we partition all faces into two groups in terms of principalcurvature difference.For each face with small curvature difference,we compute a stretch matrix that turns the principal directions into a pair of conjugate directions.For the remaining triangular faces,we simply keep their smoothed principal directions.Finally,applying a mixed-integer programming solver to the mixed principal and conjugate direction field,we obtain a planar quadrilateral mesh.Experimental results show that our method is computationally efficient and can yield high-quality PQ meshes that well approximate the geometry of the input surfaces and maintain their self-supporting properties.

Green preparation of self-supporting platinum nanoflower catalyst and its electrocatalytic oxidation performance of methanol

The three-dimensional(3D)self-supporting Pt nanoflower catalyst was prepared by using Pt organic compounds as precursors in a low-temperature molten salt system.The obtained Pt nanoflower nanoparticle can reach 400-500 nm with a face-centered cubic structure,which has the structural characteristics of a loose framework and more exposed active sites.The surfactant-free Pt nanoflower was directly used as methanol electrooxidation reaction(MOR)electrocatalysts without any pretreatment and activated carbon support.The results of electrochemical catalytic oxidation of methanol showed that the Pt nanoflower catalyst exhibit more enhanced electrocatalytic oxidation performance toward methanol compared with the commercial platinum black catalyst.The green and effective method can be developed and expected to enable mass production of fuel cell catalysts.

Recent progress of self-supported air electrodes for flexible Zn-air batteries

Smart wearable devices are regarded to be the next prevailing technology product after smartphones and smart homes,and thus there has recently been rapid development in flexible electronic energy storage devices.Among them,flexible solid-state zinc-air batteries have received widespread attention because of their high energy density,good safety,and stability.Efficient bifunctional oxygen electrocatalysts are the primary consideration in the development of flexible solid-state zinc-air batteries,and self-supported air cathodes are strong candidates because of their advantages including simplified fabrication process,reduced interfacial resistance,accelerated electron transfer,and good flexibility.This review outlines the research progress in the design and construction of nanoarray bifunctional oxygen electrocatalysts.Starting from the configuration and basic principles of zinc-air batteries and the strategies for the design of bifunctional oxygen electrocatalysts,a detailed discussion of self-supported air cathodes on carbon and metal substrates and their uses in flexible zinc-air batteries will follow.Finally,the challenges and opportunities in the development of flexible zinc-air batteries will be discussed.

Recent advances of carbon fiber-based self-supported electrocatalysts in oxygen electrocatalysis

Oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are the key reactions in numerous renewable energy devices. Unlike conventional powdered catalysts, self-supported catalysts are extensively employed in oxygen electrocatalysis because of the enhanced electron-transfer rate, high specific surface area, and superior mechanical flexibility. Among the self-supported conductive substrates, carbon fiber usually exhibits several distinctive advantages, such as a straightforward preparation process, relatively low cost, good stability, and excellent conductivity. Against this background,carbon fiber-based self-supported electrocatalysts have been widely applied and studied in oxygen electrocatalysis, indicating a promising development direction in oxygen electrocatalyst research.Thus, it is essential to offer an overall summary of the research progress in this field to facilitate its subsequent development. Taking the regulatory mechanisms and modification methods as a starting point, this review comprehensively summarizes recent research on carbon fiber-based self-supported electrocatalysts in recent years. Firstly, a brief overview of the synthesis methods and regulatory mechanisms of carbon fiber-based self-supported electrocatalysts is given. Furthermore, the view also highlights the modification methods and research progress of self-supported electrocatalysts synthesized on carbon fiber-based substrates in recent years in terms of different dopant atoms. Finally, the prospects for the application of self-supported electrocatalysts based on carbon fiber in oxygen electrocatalysis and the possible future directions of their development are presented. This review summarizes recent developments and applications of self-supported bi-functional electrocatalysts with carbon fiber-based materials as the conducting substrate in oxygen electrocatalysis. It also lays a robust scientific foundation for the subsequent reasonable design of highly effective carbon fiber-based self-supported electrocatalysts.

Deciphering the lithium storage chemistry in flexible carbon fiber-based self-supportive electrodes

Flexible carbon fiber cloth(CFC)is an important scaffold and/or current collector for active materials in the development of flexible self-supportive electrode materials(SSEMs),especially in lithium-ion batteries.However,during the intercalation of Li ions into the matrix of CFC(below 0.5 V vs.Li/Li+),the incompatibility in the capacity of the CFC,when used directly as an anode material or as a current collector for active materials,leads to difficulty in the estimation of its actual contribution.To address this issue,we prepared Ni_(5)P_(4)nanosheets on CFC(denoted CFC@Ni_(5)P_(4))and investigated the contribution of CFC in the CFC@Ni_(5)P_(4)by comparing to the powder Ni_(5)P_(4)nanosheets traditionally coated on a copper foil(CuF)(denoted P-Ni_(5)P_(4)).At a current density of 0.4 mA cm^(−2),the as-prepared CFC@Ni_(5)P_(4)showed an areal capacity of 7.38 mAh cm^(−2),which is significantly higher than that of the PNi_(5)P_(4)electrode.More importantly,theoretical studies revealed that the CFC has a high Li adsorption energy that contributes to the low Li-ion diffusion energy barrier of the Ni_(5)P_(4)due to the strong interaction between the CFC and Ni_(5)P_(4),leading to the superior Li-ion storage performance of the CFC@Ni_(5)P_(4)over the pristine Ni_(5)P_(4)sample.This present work unveils the underlying mechanism leading to the achievement of high performance in SSEMs.

Self-supported metal(Fe, Co, Ni)-embedded nitrogen-doping carbon nanorod framework as trifunctional electrode for flexible Zn-air batteries and switchable water electrolysis

To meet the practical demand of wearable/portable electronics, developing high-efficiency and durable multifunctional catalyst and in-situ assembling catalysts into electrodes with flexible features are urgently needed but challenging. Herein, we report a simple route to fabricate bendable multifunctional electrodes by in-situ carbonization of metal ion absorbed polyaniline precursor. Alloy nanoparticles encapsulated in graphite layer are uniformly distributed in the N-doping carbon nanorod skeleton. Profiting from the favorable free-standing structure and the cooperative effect of metallic nanoparticles, graphitic layer and N doped-carbon architecture, the trifunctional electrodes exhibit prominent activities and stability toward HER, OER and ORR. Notably, due to the protection of carbon layer, the electrocatalysts show the reversible catalytic HER/OER properties. The overall water splitting device can continuously work for 12 h under frequent exchanges of cathode and anode. Importantly, the bendable metal air batteries fabricated by self-supported electrode not only displays the outstanding battery performance,achieving a decent peak power density(125 mW cm^(-2)) and exhibiting favorable charge-discharge durability of 22 h, but also holds superb flexible stability. Specially, a lightweight self-driven water splitting unit is demonstrated with stable hydrogen production.

Bioinspired Nanostructured Superwetting Thin-Films in a Self-supported form Enabled“Miniature Umbrella”for Weather Monitoring and Water Rescue

Two-dimensional(2D)soft materials,especially in their self-supported forms,demonstrate attractive properties to realize biomimetic morphing and ultrasensitive sensing.Although extensive efforts on design of self-supported functional membranes and integrated systems have been devoted,there still remains an unexplored regime of the combination of mechanical,electrical and surface wetting properties for specific functions.Here,we report a self-supported film featured with elastic,thin,conductive and superhydrophobic characteristics.Through a well-defined surface modification strategy,the surface wettability and mechanical sensing can be effectively balanced.The resulted film can function as a smart umbrella to achieve real-time simulated raining with diverse frequencies and intensity.In addition,the integrated umbrella can even response sensitively to the sunlight and demonstrate a positively correlation of current signals with the intensity of sun illumination.Moreover,the superhydrophobic umbrella can be further employed to realize water rescue,which can take the underwater object onto water surface,load and rapidly transport the considerable weight.More importantly,the whole process of loaded objects and water flow velocity can be precisely detected.The self-supported smart umbrella can effectively monitor the weather and realize a smart water rescue,demonstrating significant potentials in multifunctional sensing and directional actuation in the presence of water.