A binder-free CF|PANI composite electrode with excellent capacitance for asymmetric supercapacitors

In this work,carbon fiber and polyaniline(CF|PANI)composites are prepared by using an electrochemical polymeriza-tion method.The morphology and composition characterization results show that the PANI nanospheres are successfully syn-thesized and uniformly coated on the CF.When the electrodeposition period is 300 cycles,the as-prepared CF|PANI electrode ex-hibits good specific capacitance of 231.63 F/g at 1 A/g,high performance of 98.14%retention rate from 0.5 to 20 A/g,and excel-lent cycle stability with only 0.96%capacity loss after 1000 cycles.This is ascribed to the internal resistance that was signific-antly reduced without binders,which helps to the CF|PANI electrode maintains high operating potential and pseudo-capacit-ance performance at high current density.The symmetrical supercapacitor based on two CF|PANI electrodes connecting by acid-ic PVA-H2SO4 gel electrolyte exhibits an energy density of 6.55 W·h/kg at a power density of 564.37 W/kg.In addition,the asym-metric supercapacitor based on MoS2|MWCNTs and CF|PANI electrodes with neutral PVA-Na2SO4 gel electrolyte shows an en-ergy density of 16.12 W·h/kg at a power density of 525.03 W/kg.These results indicate that the low internal resistance contrib-utes to the high energy density of symmetrical supercapacitors and asymmetric supercapacitors at high current density and high power density,which is significant for its practical application.

Coral-like and binder-free carbon nanowires for potassium dual-ion batteries with superior rate capability and long-term cycling life

Owing to the advantages of high operating voltage,environmental benignity,and low cost,potassium-based dual-ion batteries(KDIBs)have been considered as a potential candidate for large-scale energy storage.However,KDIBs generally suffer from poor cycling performance and unsatisfied capacity,and inactive components of conductive agents,binders,and current collector further lower their overall capacity.Herein,we prepare coral-like carbon nanowres(CCNWs)doped with nitrogen as a binder-free anode material for K^(+)-ion storage,in which the unique coral-like porous nanostructure and amorphous/short-range-ordered composite feature are conducive to enhancing the structural stability,to facilitating the ion transfer and to boosting the full utilization of active sites during potassiation/de-potassiation process.As a result,the CCNW anode possesses a hybrid K^(+)-storage mechanism of diffusive behavior and capacitive adsorption,and stably delivers a high capacity of 276 mAh g^(-1)at 50 mA g^(-1),good rate capability up to 2 A g^(-1),and long-term cycling stability with 93%capacity retention after 2000 cycles at 1 A g^(-1).Further,assembling this CCNW anode with an environmentally benign expanded graphite(EG)cathode yields a proof-of-concept KDIB,which shows a high specific capacity of 134.4 mAh g^(-1)at 100 mA g^(-1),excellent rate capability of 106.5 mAh g^(-1)at 1 A g^(-1),and long-term cycling stability over 1000 cycles with negligible capacity loss.This study provides a feasible approach to developing high-performance anodes for potassium-based energy storage devices.

Rational Design of Layered SnS2 on Ultralight Graphene Fiber Fabrics as Binder-Free Anodes for Enhanced Practical Capacity of Sodium-Ion Batteries

Generally,the practical capacity of an electrode should include the weight of non-active components such as current collector,polymer binder,and conductive additives,which were as high as 70 wt%in current reported works,seriously limiting the practical capacity.This work pioneered the usage of ultralight reduced graphene fiber(rGF)fabrics as conductive scaffolds,aiming to reduce the weight of nonactive components and enhance the practical capacity.Ultrathin SnS2 nanosheets/rGF hybrids were prepared and used as binder-free electrodes of sodium-ion batteries(SIBs).The interfused graphene fibers endow the electrode a porous,continuous,and conductive network.The in situ phase transformation from SnO2 to SnS2 could preserve the strong interfacial interactions between SnS2 and graphene.Benefitting from these,the designed binder-free electrode delivers a high specific capacity of 500 mAh g?1 after 500 cycles at a current rate of 0.5 A g?1 with almost 100%Coulombic efficiency.Furthermore,the weight percentage of SnS2 in the whole electrode could reach up to 67.2 wt%,much higher than that of common electrode configurations using Cu foil,Al foil,or carbon cloth,significantly highlighting the ultralight characters and advantages of the rGF fabrics for using as binder-free electrodes of SIBs.

All-Climate Aluminum-Ion Batteries Based on Binder-Free MOF-Derived FeS_(2)@C/CNT Cathode

Aluminum-ion batteries(AIBs)are promising next-generation batteries systems because of their features of low cost and abundant aluminum resource.However,the inferior rate capacity and poor all-climate performance,especially the decayed capacity under low temperature,are still critical challenges toward high-specific-capacity AIBs.Herein,we report a binder-free and freestanding metal-organic framework-derived FeS_(2)@C/carbon nanotube(FeS_(2)@C/CNT)as a novel all-climate cathode in AIBs working under a wide temperature window between−25 and 50℃ with exceptional flexibility.The resultant cathode not only drastically suppresses the side reaction and volu-metric expansion with high capacity and long-term stability but also greatly enhances the kinetic process in AIBs with remarkable rate capacity(above 151 mAh g^(−1) at 2 A g^(−1))at room temperature.More importantly,to break the bottleneck of the inherently low capacity in graphitic material-based all-climate AIBs,the new hierarchical conductive composite FeS_(2)@C/CNT highly promotes the all-climate performance and delivers as high as 117 mAh g^(−1) capacity even under−25°C.The well-designed metal sulfide electrode with remarkable performance paves a new way toward all-climate and flexible AIBs.

All Binder-Free Electrodes for High-Performance Wearable Aqueous Rechargeable Sodium-Ion Batteries

Extensive efforts have recently been devoted to the construction of aqueous rechargeable sodium-ion batteries(ARSIBs)for large-scale energy-storage applications due to their desired properties of abundant sodium resources and inherently safer aqueous electrolytes.However,it is still a significant challenge to develop highly flexible ARSIBs ascribing to the lack of flexible electrode materials.In this work,nanocube-like KNiFe(CN)6(KNHCF)and rugby balllike NaTi2(PO4)3(NTP)are grown on carbon nanotube fibers via simple and mild methods as the flexible binder-free cathode(KNHCF@CNTF)and anode(NTP@CNTF),respectively.Taking advantage of their high conductivity,fast charge transport paths,and large accessible surface area,the as-fabricated binder-free electrodes display admirable electrochemical performance.Inspired by the remarkable flexibility of the binder-free electrodes and the synergy of KNHCF@CNTF and NTP@CNTF,a high-performance quasi-solid-state fiber-shaped ARSIB(FARSIB)is successfully assembled for the first time.Significantly,the as-assembled FARSIB possesses a high capacity of 34.21 mAh cm?3 and impressive energy density of 39.32 mWh cm?3.More encouragingly,our FARSIB delivers superior mechanical flexibility with only 5.7%of initial capacity loss after bending at 90°for over 3000 cycles.Thus,this work opens up an avenue to design ultraflexible ARSIBs based on all binder-free electrodes for powering wearable and portable electronics.

3D Interconnected MoO_2 Nanocrystals on Nickel Foam as Binder-free Anode for Li-ion Batteries

MoOnanocrystals(NCs) on Ni foam were simply synthesized via a facile hydrothermal method and a dip-coating method. It was worth noting that ultrafine interconnected MoOnanocrystals(about 10 nm) were uniformly anchored on Ni foam to fabricate a particular three-dimensional architecture, which may provide more active sites and shorter transmission pathways for lithium ions. As binder-free anode, MoONCs on Ni foam deliver a high initial discharge capacity of 990 mAh·gand retain a reversible capacity of 924 mAh· g(-1) after 100 cycles at a current density of 0.1 C. More importantly, when the current density returns from 2 C to 0.1 C, the capacity recovers to 910 mAh·g(-1)(about 92% of the original high capacity), suggesting excellent cycling stability and rate capability. The particular 3 D electrode as binder-free anode makes it a promising anode candidate for high-performance lithium-ion batteries.

3D MoS_(2) foam integrated with carbon paper as binder-free anode for high performance sodium-ion batteries

Molybdenum sulfide(MoS_(2))with well-designed porous structure has the potential to be great electrode materials in sodium-ion batteries due to its high theoretical capacity and abundant resource,however,hindered by its intrinsic low conductivity and stability.Herein,MoS_(2) with 3 D macroporous foam structure and high conductivity was obtained through SiO_(2) templates and integrated with carbon paper(3 D FMoS_(2)/CP).It has showed superior specific capacity(225 m A h g^(-1),0.4–3 V)and cycling stability(1000 cycles)at high rate(2000 m A g^(-1)),with a low decay rate(0.033%per cycle)in sodium-ion batteries.The excellent electrochemical performance may originate from its unique integrated structure:3 D MoS_(2) macropores providing high surface area and abundant transfer channels while carbon paper enhancing the conductivity of MoS_(2) and avoiding unnecessary side reactions brought by binder addition.

A Binder-Free Amorphous Manganese Dioxide for Aqueous Zinc-Ion Battery

Aqueous zinc-ion battery has attracted much attention due to its low price, high safety, and high theoretical specific capacity. However, most of their performances are limited by the unsatisfied architecture of cathodes. Herein, we fabricated amorphous manganese dioxide by an in situ deposition method. The amorphous manganese dioxide can directly serve as the cathode of an aqueous zinc-ion battery without a binder. The resultant cathode exhibits a high specific capacity of 133.9 mAh/g at 200 mA/g and a capacity retention of 82% over 50 cycles at 1 A/g.

A high over-potential binder-free electrode constructed of Prussian blue and MnO2 for high performance aqueous supercapacitors

Extending the potential window of aqueous supercapacitors (SCs) up to 2.0 V is still a great challenge.Based on their good dynamic structural reversibility and open framework structure,the coordination superamolecular networks (CSNs) exhibit rapid charge/discharge ability and excellent cycle stability.As a typical coordination superamolecular network (CSN),Prussian blue (denoted as CSN-PB),which self-assembled by the CN-ligand and iron ions is firstly in-situ grown on carbon cloth,followed by electro-deposition of MnO2 to form CSN-PB/MnO2 composite electrode.Benefiting from synergistic effect of the constituent components,as well as the open framework structure of CSN-PB,this composite electrode reaches a high potential window of 1.4 V (vs.Ag/AgCl) and delivers a good specific capacitance of 315.3 F·g^-1 in aqueous electrolyte.An aqueous asymmetric device,constructed with CSN-PB/MnO2 composite as cathode and activated carbon as anode,can work in a stable potential window of 2.4 V,exhibits a high energy density of 46.13 Wh·kg^-1 and excellent cycling stability with 85.5% capacitance retention after 20,000 cycles.This work provides a new concept of high dynamic structural reversibility from CSNs to increase the cell voltage of asymmetric SCs for further boosting energy density.

Solvothermal-induced construction of ultra-tiny Fe_(2)O_(3) nanoparticles/graphene hydrogels as binder-free high-capacitance anode for supercapacitors

Three-dimensional(3D) ultra-tiny Fe_(2)O_(3) nanoparticles/graphene hydrogels were prepared using a facile and efficient solvothermal reaction, by which the phase of iron oxide, particle size and the morphology of hydrogels can be precisely controlled by simply adjusting the solvothermal reaction time. Accordingly, the effect of the microstructures of hydrogels on electrochemical performance was systematically studied. It was found that Fe_(2)O_(3)/r GO-50 hydrogels(with a solvothermal reaction time of 50 min) possessed a desirable crystallinity, suitable particle size, decent porous structure, large specific surface area and high electrical conductivity, thus exhibiting a superior electrochemical performance as binder-free anode of supercapacitors: a large potential range of 1.15 V, an ultrahigh specific capacitance of 1090 F·g^(-1) at a current density of 2A·g^(-1) and excellent rate capability (531 F·g^(-1) at 10 A·g^(-1)). The rational design and systematic research of electrode materials will provide new lights for the preparation of advanced electrochemical energy storage devices.

NiS_(2) nanosheet arrays on stainless steel foil as binder-free anode for high-power sodium-ion batteries

Owing to the wide range and low cost of sodium resources,sodium-ion batteries(SIBs)have received extensive attention and research.Metal sulfides with high theoretical capacity are used as promising anode materials for SIBs.This paper presents the electrochemical performance of the binder-free NiS_(2)nanosheet arrays grown on stainless steel(SS)substrate(NiS_(2)/SS)using an in situ growth and sulfidation strategy as anode for sodium ion batteries.Owing to the close connection between the NiS_(2)nanosheet arrays and the SS current collector,the NiS_(2)/SS anode demonstrates high rate capability with a reversible capacity of 492.5 mAh·g^(-1)at 5.0C rate.Such rate capability is superior to that of NiS_(2)nanoparticles(NiS_(2)/CMC:41.7 mAh·g^(-1)at 5.0C,NiS_(2)/PVDF:7.3 mAh·g^(-1)at 5.0C)and other Ni sulfides(100–450 mAh·g^(-1)at 5.0C)reported.Furthermore,the initial reversible specific capacity and Coulombic efficiency of NiS_(2)/SS are 786.5 mAh·g^(-1)and 81%,respec-tively,demonstrating a better sodium storage ability than those of most NiS_(2)anodes reported for SIBs.In addition,the amorphization and conversion mechanism during the sodiation/desodiation process of NiS_(2)are proposed after investigation by in situ X-ray diffraction(XRD)measurements of intermediate products at successive charge/discharge stages.

Scalable fabrication of NiCo_(2)O_(4)/reduced graphene oxide composites by ultrasonic spray as binder-free electrodes for supercapacitors with ultralong lifetime

Durable and cost-effective electrode materials are essential for practical application of supercapacitors.Herein,large area NiCo_(2)O_(4)/reduced graphene oxide(NiCo_(2)O_(4)/rGO)composites with hierarchical structure were fabricated by a facile one-step ultrasonic spray on Ni foam and directly used as the binder-free electrodes for supercapacitors in aqueous KOH electrolyte.Owing to high electrical conductivity of rGO,hierarchical and layered structure of the electrode,as well as tight adhesion of active materials on the current collector,the as-obtained hybrid electrodes show a high specific capacitance of 871 F g^(-1)at current density of 1 A g^(-1),good rate performance and remarkable cycling stability with a capacitance retention of 134%after 30000 cycles.Besides,the assembled NiCo_(2)O_(4)/rGO//AC asymmetric supercapacitor(ASC)displays the maximum energy density of 29.3 Wh kg^(-1)at a power density of 790.8 W kg^(-1).Significantly,an ultralong cycling life of 102%capacitance retention is achieved for the ASC device after 30,000 charge/discharge cycles at 20 A g^(-1).The scalable fabrication route and excellent electrochemical performance of the NiCo_(2)O_(4)/rGO composites open the door for making novel hybrid electrodes of advanced supercapacitors.

Binder-free electrodes for advanced potassium-ion batteries:A review

Potassium-ion batteries(PIBs)have attracted enormous attention due to the abundance of potassium resources,low cost,fast ionic conductivity of electrolyte and relatively high operating voltage.Despite great effo rts and progress,researches on PIBs are still at the initial stage,especially in the emerging field of flexible and wearable PIBs.The inevitable challenges for PIBs include low reversible capacity,unsatisfactory cycling stability and insufficient energy density,the solution to which mostly relies on designing adva nced electrodes.Binder-free electrodes have emerged as promising electrode architecture for PIBs.Such electrodes avoid the use of insulating binders,which can be designed with various synergistic functional materials to address the aforementioned PIB issues and be endowed with flexibility/wearability.In this review,we mainly summarize the recent progress on binde r-free electrodes for PIBs,with the focus on the methodologies,detailed strategies and functional materials for electrode construction.One strategy for binder-free electrodes is to assemble free-standing architecture with the help of carbon nanotubes(CNTs),graphitic fibers,and other carbon or mechanically robust materials,either alone or in combination.The other effective strategy is current collector substrate-assisted direct growth,including the use of carbon cloth,metal.MXenes and other conductive substrates.Additionally,challenges and research opportunities are put forward at the end as the guidance for future development of binder-free PIB devices.

Extraordinary high-temperature mechanical properties in binder-free nanopolycrystalline WC ceramic

From the perspective of high-temperature applications,materials with excellent high-temperature mechanical properties are always desirable.The present work demonstrates that the binder-free nanopolycrystalline WC ceramic with an average grain size of 103 nm obtained by high-pressure and hightemperature sintering exhibits excellent mechanical properties at both room temperature and high temperature up to 1000℃.Specifically,the binder-free nanopolycrystalline WC ceramic still maintains a considerably high Vicker hardness H_(V)of 23.4 GPa at 1000℃,which is only 22%lower than the room temperature H_(V).This outstanding thermo-mechanical stability is superior to that of typical technical ceramics,e.g.SiC,Si_(3)N_(4),Al_(2)O_(3),etc.Nanocrystalline grains with many dislocations,numerous low-energy,highly stableΣ2 grain boundaries,and a relatively low thermal expansion coefficient,are responsible for the observed outstanding high-temperature mechanical properties.

A binder-free electrode for efficient H_(2)O_(2) formation and Fe2+ regeneration and its application to an electro-Fenton process for removing organics in iron-laden acid wastewater

The electro-Fenton process,with its capacity for in-situ H_(2)O_(2)formation and Fe^(2+)regeneration,is a strik-ing alternative to the traditional chemical-Fenton process.However,the frequent requirement of extra binders for electrode fabrication leads to low catalyst utilization,a complex fabrication process,and weak conductivity.Herein,a three-dimensional(3D)porous electrode was fabricated in-situ on a Ni foam(NF)substrate integrated with nitrogen-doped carbon nanotubes(N@C)derived from carbonization of zeolitic imidazolate framework-8(ZIF-8)without any binder.The resulting 900/N@C-NF cathode(synthesized at 900℃)was high in surface area,N content,and degree of graphitization,achieved high performance of H_(2)O_(2)production(2.58 mg L^(−1)h^(−1)H_(2)O_(2)/mg catalyst)at-0.7 V(vs.SCE),and enabled prompt regeneration of Fe^(2+).The electro-Fenton system equipped with the 900/N@C-NF cathode was effective in removing a diverse range of organic pollutants,including rhodamine B(Rh B),phenol,bisphenol A(BPA),nitroben-zene(NB),and Cu-ethylenediaminetetraacetic acid(EDTA),and significantly attenuating the concentration of chemical oxygen demand(COD)in the real acid wastewater,exhibiting superior activity and stability.This binder-free and self-supporting electro-Fenton cathode was thus shown to be an attractive candidate for application to wastewater treatment,particularly those rich in organics,acids,and Fe^(3+)/Fe^(2+).

Covalent interfacial coupling of vanadium nitride with nitrogen-rich carbon textile boosting its lithium storage performance as binder-free anode

Eliminating the usage of metal current collectors and binders in traditional battery electrode configuration is an effective strategy to significantly improve the capacities of lithium ion batteries (LIBs). Herein, we demonstrate the construction of porous vanadium nitride (VN) nanosheet network in situ grown on nitrogen-rich (N-rich) carbon textile (N-C@P-VN) as lightweight and binder-free anode for LIBs. The N-rich carbon textile is used both as the current collector and host to store Li^(+), thus improving the specific capacities of binder-free VN anode and meanwhile reducing the inert mass of the whole cell. Moreover, the open spaces in carbon textile and vertically aligned pores in VN nanosheet network can not only provide an expressway for Li+ and e− transport, but also afford more active sites. As a result, the binder-free N-C@P-VN anode maintains a specific capacity of 1,040 mAh·g^(−1) (or an areal capacity of 2.6 mAh·cm^(−2)) after 100 cycles at 0.1 mA·cm^(−2) in half cell. Moreover, in an assembled N-C@P-VN//LiFePO4 full cell, it exhibits an areal capacity of 1.7 mAh·cm^(−2) after 300 cycles at 0.1 C. The synergistic strategy of N-C substrate and porous VN network could be applied to guide rational design of similar N-C@nitride or sulfide hybrid systems with corresponding sulfur-doped carbon textile as the substrate.

Needle-like cobalt phosphide arrays grown on carbon fiber cloth as a binder-free electrode with enhanced lithium storage performance

Cobalt phosphide(CoP) is a promising anode candidate for lithium-ion batteries(LIBs) due to its high specific capacity and low working potential.However,the poor cycling stability and rate performance,caused by low electrical conductivity and huge volume variation,impede the further practical application of CoP anode materials.Herein,we report an integrated binder-free electrode featuring needle-like CoP arrays grown on carbon fiber cloth(CC) for efficient lithium storage.The as-prepared CoP/CC electrode integrates the advantages of 1 D needle-like CoP arrays for efficient electrolyte wettability and fast cha rge transpo rtation,and 3 D CC substrate for superior mechanical stability,flexibility and high conductivity.As a result,the CoP/CC electrode delivers an initial specific capacity of 1283 mAh/g and initial Coulombic effeciencies of 85.4%,which are much higher than that of conventional CoP electrode.Notably,the Co P/CC electrode shows outstanding cycling performance up to 400 cycles at 0.5 A/cm^(2) and excellent rate performance with a discharge capacity of 549 mAh/g even at 5 A/cm^(2).This work demonstrates the great potential of integrated CoP/CC hybrid as efficient bind-free and freestanding electrode for LIBs and future flexible electronic devices.

Feather-like NiCo2O4 self-assemble from porous nanowires as binder-free electrodes for low charge transfer resistance

The unique feather-like arrays composing of ultrathin secondary nanowires are fabricated on nickel foam(NF)through a facile hydrothermal strategy.Thus,the enhancement of electrochemical properties especially the low charge transfer resistance strongly depends on more active sites and porosity of the morphology.Benefiting from the unique structure,the optimized NiCo2O4 electrode delivers a significantly lower charge transfer resistance of 0.32Ω and a high specific capacitance of450 Fg^-1 at 0.5 A.g^-1,as well as a superior cycling stability of 139.6%capacitance retention.The improvement of the electrochemical energy storage property proves the potential of the fabrication of various binary metal oxide electrodes for applications in the electrochemical energy field.

Modified tungsten oxide as a binder-free anode in lithium-ion battery for improving electrochemical stability

As the anode active substance of lithium ions battery(LIB),the low conductivity/ion diffusivity and large volume changes of tungsten oxide(WO_(3))lead to its serious polarization during the lithiation/delithiation process,decreasing the cycling stability.To address these challenges,a binder-free anode consisting of nitrogen-doped tungsten oxide nanosheets,encapsulated in carbon layers(N-doped WO_(3)@CL)and entangled with carbon nanotubes macro-films(CMF),was successfully synthesized through a combination of hydrothermal and online assembly method.Compared with the pristine tungsten oxide entangled with carbon nanotubes macro-films(WO_(3)@CMF),the synthesized N-doped WO_(3)@CL@CMF as a binder-free LIB anode demonstrated better electrochemical performance,which could be attributed to(1)surface defects of WO_(3)created by N dopant providing more channels to improve Li^(+)diffusion,(2)the N-doped WO_(3)@CL with a flower-like structure shortening the diffusion length of Li^(+)ions and further leading to high Li^(+)incorporation,and(3)carbon layers and carbon nanotubes synergistically alleviating the large volume change of the N-doped WO_(3)@CL@CMF electrode during the charging and discharging process.The present study offers insights into employing nitrogen dopant and a carbon matrix to mediate the conductivity and wrapped structure in the WO_(3)semiconductor powder,which provides an important strategy for large-scale design of the binder-free LIB anode with high performance.

Capacitive Properties of the Binder-Free Electrode Prepared from Carbon Derived from Cotton and Reduced Graphene Oxide

减少的 graphene 氧化物(rGO ) 和从棉花(aCFC ) 导出的激活的碳的没有文件夹的合成电影被制作了并且用作电极让电气化学的电容器(EC ) 在另外的文件夹引起的传统的过程避免电容的性能的减少。最佳的 aCFC 在 850