Continuous Fabrication of Ti_(3)C_(2)T_x MXene-Based Braided Coaxial Zinc-Ion Hybrid Supercapacitors with Improved Performance

Zinc-ion hybrid fiber supercapacitors(FSCs)are promising energy storages for wearable electronics owing to their high energy density,good flexibility,and weavability.However,it is still a critical challenge to optimize the structure of the designed FSC to improve energy density and realize the continuous fabrication of super-long FSCs.Herein,we propose a braided coaxial zinc-ion hybrid FSC with several meters of Ti_(3)C_(2)T_x MXene cathode as core electrodes,and shell zinc fiber anode was braided on the surface of the Ti_(3)C_(2)T_x MXene fibers across the solid electrolytes.According to the simulated results using ANSYS Maxwell software,the braided structures revealed a higher capacitance compared to the spring-like structures.The resulting FSCs exhibited a high areal capacitance of 214 mF cm^(-2),the energy density of 42.8μWh cm^(-2)at 5 mV s^(-1),and excellent cycling stability with 83.58%capacity retention after 5000 cycles.The coaxial FSC was tied several kinds of knots,proving a shape-controllable fiber energy storage.Furthermore,the knitted FSC showed superior stability and weavability,which can be woven into watch belts or embedded into textiles to power smart watches and LED arrays for a few days.

Zinc-ion hybrid supercapacitors with ultrahigh areal and gravimetric energy densities and long cycling life

Zinc ion hybrid supercapacitor (ZIHSC) with promising energy and power densities is an excellent answer to the ever-growing demand for energy storage devices.The restricted lifespan due to the dendrite formation on metallic zinc (Zn) is one of the main roadblocks.Herein,we investigate the electrochemical capability of oxygen-enriched porous carbon nanofibers (A-CNF) and nitrogen,oxygen-enriched porous carbon nanofibers (N-CNF) cathode materials for structural ZIHSCs.To this end,a series of samples with different chemical compositions (N and O contents) are prepared to present deep insight into the electrochemical mechanism between N/O doping and Zn-ion storage.The as-prepared ZIHSC in the presence of N-CNF cathode and Zn Cl_(2) electrolyte offers a battery-level gravimetric energy density of 143.2 Wh kg^(-1)at a power density of 367.1 W kg^(-1).The free-standing N-CNF electrodes in ZIHSCs enjoy delivering an outstanding areal energy density of 110.4μWh cm^(-2)at 0.24 m W cm^(-2),excellent rate capability,and noticeable cycling stability over 10,000 cycles at 10 A g^(-1)with less than 7%decay.It was also concluded that active pyrrolic N dopants might deliver and facilitate more pseudocapacitance in ZIHSCs than other N configurations,resulting in higher adsorption/desorption and insertion/extraction process of Zn Cl^(+).Taking advantage of the beneficial properties of a free-standing continuous cathode,this novel generation of structural cathode material offers high areal and gravimetric energy densities and mechanical properties in a single zinc-ion-based package.

PVP/PAN-derived porous carbon fiber for zinc-ion hybrid supercapacitors

Porous carbon fibers are promising cathodes for zinc-ion hybrid supercapacitors(ZHSs)owing to their abundant active sites,great conductivity,and stable physical and chemical properties.However,designing a proper preparation technique to regulate the microstructure of carbon fibers still remains a great challenge.Here,a poly vinylpyrrolidone/po-lyacry lonitrile(PVP/PAN)-derived porous carbon fiber is developed via the PVP/PAN blend electrospinning and hydrothermal selective PVP removal strategy.The hydrothermal selective PVP removal strategy can effectively avoid a cross-linking between PVP and PAN during the traditional stabilization at air atmosphere.In PVP/PAN-derived porous carbon fiber,the sufficient micropores provide abundant space for the Zn^(2+)storage,whereas the proper mesopores contribute to the fast ion transfer.These hierarchical porous structures endow ZHSs with high specific capacity and high-rate performance.The ZHS assembled with the optimal PVP/PAN-derived porous carbon fiber(PVP-PANC-0.8)displays an outstanding specific capacity of 208 mAh·g^(-1),high rate capability(49.5%)from 0.5 to 5 A·g^(-1),and 72.25%capacity retention after 10,000 cycles at 0.5 A·g^(-1).

Hydrophilic polyanionic hydrogel electrolyte for anti-freezing and bending resistant zinc-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors(ZHSCs)have been widely considered as promising candidates for flexible electrochemical energy storage devices.The key challenge is to develop hydrogel electrolytes with high hydrophilicity,anti-freezing,bending resistance,and stable interface with electrodes.This study reported a hydrogel electrolyte system that can meet the above functions,in which the zincophilic and negatively charged SO3−,migratable Na+,abundant hydrophilic functional groups,gum xanthan,and porous architecture could effectively promote the electrochemical performance of ZHSCs.ZHSCs with such hydrogel electrolytes not only exhibited good low-temperature performance but also showed excellent bending resistance ability.A high specific capacitance could be kept after a long air-working lifespan over 10,000 cycles under a wide operation voltage of 1.85 V at−10℃.Furthermore,flexible ZHSCs could maintain the capacitance retention of 93.18%even after continuous 500 bends at an angle of 180°.The designed hydrogel electrolytes could be also used for other electrochemical energy storage devices with anti-freezing and bending resistance by changing electrolyte salt.

Anti-stacking synthesis of MXene-reduced graphene oxide sponges for aqueous zinc-ion hybrid supercapacitor with improved performance

Two‑dimensional MXenes with an enormous active surface area are considered to be significant cathode materials for Zn‑ion hybrid supercapacitors. However, the nanosheets are easily self-restacked during the assembly into macroscopic porous electrodes, resulting in a significantly reduced effective surface area, hindering their applications in energy storage. Here, MXenes are subtly distributed on the surface of the sponge in a coral-like structure rather than participating in the assembly of the framework, which has suppressed the self-restacking of MXene effectively, improved the hydrophilicity of the sponge, and provided fast diffusion channels for electrolyte ions. Therefore, the MXene-TiC-reduced graphene oxide sponge exhibits excellent electrical conductivity, an enormous specific surface area with abundant accessible electroactive sites, and superior electrochemical performance. The resulting sponge demonstrates an outstanding specific capacity, up to 501 mAh g–1 at 0.2 A g–1 , with excellent capacity retention (90%) after 3100 cycles as Zinc-ion hybrid supercapacitor cathodes. Furthermore, it exhibits an elegant gravimetric energy density of 486 mWh g–1 at 415 mW g–1 , which has surpassed most leading MXene-based Zn-ion cathodes. This work provides a new synthetic idea for MXene-based macro-composites and paves a new avenue for designing next-generation flexible and portable porous electrodes with high gravimetric and rate performances.

Flexible quasi-solid-state zinc-ion hybrid supercapacitor based on carbon cloths displays ultrahigh areal capacitance

Over the past few years,the flexible quasi-solid-state zinc-ion hybrid supercapacitors(FQSS ZHSCs)have been found to be ideal for wearable electronics applications due to their high areal capacitance and energy density.The assembly of desirable ZHSCs devices that have promising practical applications is of high importance,whereas it is still challenging to assemble ZHSCs devices.In this study,a ZHSC that exhibited ultrahigh areal capacitance and high stability was developed by using an active carbon cloth(ACC)cathode,which could improve ionic adsorption.The as-obtained ACC cathode had an energy storage mechanism due to the electrical double-layer capacitive behavior of Zn^(2+),which was accompanied by the dissolution/deposition of Zn_(4)SO_(4)(OH)6·5H2O.The ACC//Zn@ACC ZHSC device exhibited an areal capacitance of 2437 mF cm^(−2)(81 F cm^(−3),203 F g^(-1) under the mass of ACC with∼12 mg cm^(−2))at 1 mA cm^(−2),an areal energy density of 1.354 mWh cm^(−2) at 1 mW cm^(−2),as well as high stability(with an insignificant capacitance decline after 20000 cycles),which was demonstrated to outperform the existing ZHSCs.Furthermore,the assembled flexible device still had competitive capacitance,energy density and service life when integrated into a FQSS ZHSC.When applied in practice,the device could achieve high mechanical flexibility,wearable stability and output.This study can inspire the development of the FQSS ZHSC device to satisfy the demands for wearable energy storage devices with high performance.

Electrostatic Interaction-directed Construction of Hierarchical Nanostructured Carbon Composite with Dual Electrical Conductive Networks for Zinc-ion Hybrid Capacitors with Ultrastability

Metal-organic framework(MOF)-derived carbon composites have been considered as the promising materials for energy storage.However,the construction of MOF-based composites with highly controllable mode via the liquid-liquid synthesis method has a great challenge because of the simultaneous heterogeneous nucleation on substrates and the self-nucleation of individual MOF nanocrystals in the liquid phase.Herein,we report a bidirectional electrostatic generated self-assembly strategy to achieve the precisely controlled coatings of single-layer nanoscale MOFs on a range of substrates,including carbon nanotubes(CNTs),graphene oxide(GO),MXene,layered double hydroxides(LDHs),MOFs,and SiO_(2).The obtained MOF-based nanostructured carbon composite exhibits the hierarchical porosity(V_(meso)/V_(micro)∶2.4),ultrahigh N content of 12.4 at.%and"dual electrical conductive networks."The assembled aqueous zinc-ion hybrid capacitor(ZIC)with the prepared nanocarbon composite as a cathode shows a high specific capacitance of 236 F g^(-1)at 0.5 A g^(-1),great rate performance of 98 F g^(-1)at 100 A g^(-1),and especially,an ultralong cycling stability up to 230000 cycles with the capacitance retention of 90.1%.This work develops a repeatable and general method for the controlled construction of MOF coatings on various functional substrates and further fabricates carbon composites for ZICs with ultrastability.

Dual-ion carrier storage through Mg^(2+) addition for high-energy and long-life zinc-ion hybrid capacitor

Cation additives can efficiently enhance the total electrochemical capabilities of zinc-ion hybrid capacitors (ZHCs).However their energy storage mechanisms in zinc-based systems are still under debate.Herein,we modulate the electrolyte and achieve dual-ion storage by adding magnesium ions.And we assemble several Zn//activated carbon devices with different electrolyte concentrations and investigate their electrochemical reaction dynamic behaviors.The zinc-ion capacitor with Mg^(2+)mixed solution delivers 82 mAh·g^(-1)capacity at 1 A·g^(-1) and maintains 91%of the original capacitance after 10000 cycling.It is superior to the other assembled zinc-ion devices in single-component electrolytes.The finding demonstrates that the double-ion storage mechanism enables the superior rate performance and long cycle lifetime of ZHCs.

Ag-integrated mixed metallic Co-Fe-Ni-Mn hydroxide composite as advanced electrode for high-performance hybrid supercapacitors

Direct growth of redox-active noble metals and rational design of multifunctional electrochemical active materials play crucial roles in developing novel electrode materials for energy storage devices.In this regard,silver(Ag)has attracted great attention in the design of efficient electrodes.Inspired by the house/building process,which means electing the right land,it lays a strong foundation and building essential columns for a complex structure.Herein,we report the construction of multifaceted heterostructure cobalt-iron hydroxide(CFOH)nanowires(NWs)@nickel cobalt manganese hydroxides and/or hydrate(NCMOH)nanosheets(NSs)on the Ag-deposited nickel foam and carbon cloth(i.e.,Ag/NF and Ag/CC)substrates.Moreover,the formation and charge storage mechanism of Ag are described,and these contribute to good conductive and redox chemistry features.The switching architectural integrity of metal and redox materials on metallic frames may significantly boost charge storage and rate performance with noticeable drop in resistance.The as-fabricated Ag@CFOH@NCMOH/NF electrode delivered superior areal capacity value of 2081.9μA h cm^(-2)at 5 mA cm^(-2).Moreover,as-assembled hybrid cell based on NF(HC/NF)device exhibited remarkable areal capacity value of 1.82 mA h cm^(-2)at 5 mA cm^(-2)with excellent rate capability of 74.77%even at 70 mA cm^(-2)Furthermore,HC/NF device achieved maximum energy and power densities of 1.39 mW h cm^(-2)and 42.35 mW cm^(-2),respectively.To verify practical applicability,both devices were also tested to serve as a self-charging station for various portable electronic devices.

Anion storing,oxygen vacancy incorporated perovskite oxide composites for high-performance aqueous dual ion hybrid supercapacitors

Dual ion storage hybrid supercapacitors(HsCs)are considered as a promising device to overcome the limited energy density of existing supercapacitors while preserving high power and long cyclability.However,the development of high-capacity anion-storing materials,which can be paired with fast charg-ing capacitive electrodes,lags behind cation-storing counterparts.Herein,we demonstrate the surface faradaic OH-storage mechanism of anion storing perovskite oxide composites and their application in high-performance dual ion HsCs.The oxygen vacancy and nanoparticle size of the reduced LaMnO_(3)(r-LaMnO_(3))were controlled,while r-LaMnO_(3) was chemically coupled with ozonated carbon nanotubes(oCNTs)for the improved anion storing capacity and cycle performance.As taken by in-situ and ex-situ spectroscopic and computational analyses,OH-ions are inserted into the oxygen vacancies coordi-nating with octahedral Mn with the increase in the oxidation state of Mn during the charging process or vice versa.Configuring OH-storing r-LaMnO_(3)/oCNT composite with Na*storing MXene,the as-fabricated aqueous dual ion HSCs achieved the cycle performance of 73.3%over 10,000 cycles,delivering the max-imum energy and power densities of 47.5 w h kg^(-1) and 8 kw kg^(-1),respectively,far exceeding those of previously reported aqueous anion and dual ion storage cells.This research establishes a foundation for the unique anion storage mechanism of the defect engineered perovskite oxides and the advancement of dual ion hybrid energy storage devices with high energy and power densities.

An aqueous magnesium-ion hybrid supercapacitor operated at-50℃

The recent advances in aqueous magnesium-ion hybrid supercapacitor(MHSC)have attracted great attention as it brings together the benefits of high energy density,high power density,and synchronously addresses cost and safety issues.However,the freeze of aqueous electrolytes discourages aqueous MHSC from operating at low-temperature conditions.Here,a low-concentration aqueous solution of 4 mol L^(-1) Mg(ClO_(4))_(2) is devised for its low freezing point(-67℃)and ultra-high ionic conductivity(3.37 mS cm^(-1) at-50℃).Both physical characterizations and computational simulations revealed that the Mg(ClO_(4))_(2) can effectively disrupt the original hydrogen bond network among water molecules via transmuting the electrolyte structure,thus yielding a low freezing point.Thus,the Mg(ClO_(4))_(2) electrolytes endue aqueous MHSC with a wider temperature operation range(-50℃–25℃)and a higher energy density of 103.9 Wh kg^(-1) at 3.68 kW kg^(-1) over commonly used magnesium salts(i.e.,MgSO_(4) and Mg(NO_(3))_(2))electrolytes.Furthermore,a quasi-solid-state MHSC based on polyacrylamide-based hydrogel electrolyte holds superior low-temperature performance,excellentflexibility,and high safety.This work pioneers a convenient,cheap,and eco-friendly tactic to procure low-temperature aqueous magnesium-ion energy storage device.

Rational design of nitrogen doped hierarchical porous carbon for optimized zinc-ion hybrid supercapacitors

Aqueous rechargeable zinc-ion hybrid supercapacitors are considered to be a promising candidate for large-scale energy storage devices owing to their high safety,long life,and low price.In this paper,a nitrogen doped hierarchical porous carbon is evaluated as the cathode for aqueous rechargeable zinc-ion hybrid supercapacitors.Benefiting from the synergistic merits of excellent structural features of N-HPC and tiny zinc dendrite of Zn anode in ZnSO4 electrolyte,the zinc-ion hybrid supercapacitor exhibits excellent energy storage performance including high capacity of 136.8 mAh·g^−1 at 0.1·Ag^−1,high energy density of 191 Wh·kg^−1,large power density of 3,633.4 W·kg^−1,and satisfactory cycling stability of up to 5,000 cycles with a capacity retention of 90.9%.This work presents a new prospect of developing high-performance aqueous rechargeable zinc ion energy storage devices.

All-Climate Stretchable Dendrite-Free Zn-Ion Hybrid Supercapacitors Enabled by Hydrogel Electrolyte Engineering

Hybrid supercapacitors have shown great potentials to fulfill the demand of future diverse applications such as electric vehicles and portable/wearable electronics.In particular,aqueous zinc-ion hybrid supercapacitors(ZHSCs)have gained much attention due to their low-cost,high energy density,and environmental friendliness.Nevertheless,typical ZHSCs use Zn metal anode and normal liquid electrolyte,causing the dendrite issue,restricted working temperature,and inferior device flexibility.Herein,a novel flexible Zn-ion hybrid supercapacitor(FZHSC)is developed by using activated carbon(AC)anode,δ-MnO_(2) cathode,and innovative PVA-based gel electrolyte.In this design,heavy Zn anode and its dendrite issue are avoided and layered cathode with large interlayer spacing is employed.In addition,flexible electrodes are prepared and integrated with an anti-freezing,stretchable,and compressible hydrogel electrolyte,which is attained by simultaneously using glycerol additive and freezing/thawing technique to regulate the hydrogen bond and microstructure.The resulting FZHSC exhibits good rate capability,high energy density(47.86 Wh kg^(−1);3.94 mWh cm^(−3)),high power density(5.81 kW kg^(−1);480 mW cm^(−3)),and excellent cycling stability(~91%capacity retention after 30000 cycles).Furthermore,our FZHSC demonstrates outstanding flexibility with capacitance almost unchanged even after various continuous shape deformations.The hydrogel electrolyte still maintains high ionic conductivity at ultralow temperatures(≤−30℃),enabling the FZHSC cycled well,and powering electronic timer robustly within an all-climate temperature range of−30~80℃.This work highlights that the promising Zn metal-free aqueous ZHSCs can be designed with great multifunctionality for more practical application scenarios.

Recent progress in flexible Zn-ion hybrid supercapacitors: Fundamentals, fabrication designs, and applications

One of the most exciting new developments in energy storage technology is flexible Zn-ion hybrid supercapacitors(f-ZIHSCs),which combine the high energy of Zn-ion batteries with high-power supercapacitors to satisfy the needs of portable flexible electronics.However,the development of f-ZHSCs is still in its infancy,and there are numerous barriers to overcome before they can be widely implemented for practical applications.This review gives an up-to-date description of recent achievements and underlying concepts in energy storage mechanisms of f-ZIHSCs and emphasizes the critical role of cathode,anode,and electrolyte materials systems in speeding the prosperity of f-ZIHSCs.The innovative nanostructured-based cathode materials for f-ZIHSCs include carbon(e.g.,porous carbon,heteroatom-doped carbon,biomass-derived porous carbon,graphene,etc.),metal-oxides,MXenes,and metal/covalentorganic frameworks,and other materials(e.g.,activated carbon,phosphorene,etc.)are mainly focused.Afterward,the latest developments in flexible anode and electrolyte frameworks and impacts of electrolyte compositions on the electrochemical properties of f-ZIHSC are elaborated.Subsequently,the advancements based on fabrication designs,including quasi-solid-state,micro,fiber-shaped,and all climate-changed f-ZIHSCs,are discussed in detail.Lastly,a summary of current challenges and recommendations for the future progress of advanced f-ZIHSC are addressed.This review article is anticipated to further understand the viable strategies and achievable approaches for assembling high-performance f-ZIHSCs and boost the technical revolutions on cathode,anode,and electrolytes for f-ZIHSC devices.

Improving the charge kinetics through in-situ growth of NiSe nanoparticles on g-C_(3)N_(4)nanosheets for efficient hybrid supercapacitors

Nickel selenide(NiSe)has been a promising positive electrode for hybrid supercapacitors due to its multiple oxidation states,tunability,and high specific capacity.However,sluggish ion transfers and particle agglomeration hamper its electrochemical performance.In the present study,we have grown NiSe nanoparticles on two-dimensional(2D)graphitic carbon nitride(g-C_(3)N_(4))nanosheets to realize three-dimensional(3D)architecture.The 2D support,high nitrogen content,and features of g-C_(3)N_(4)enhanced the specific capacity of the NiSe/g-C_(3)N_(4)nanocomposite material.The resulting nanocomposite shows a specific capacity of 320 mA h g^(-1)at a current density of 1 A g^(-1),which is considerably higher than pristine NiSe.Later,the hybrid supercapacitor(HSC)device was fabricated using NiSe/g-C_(3)N_(4)composite as positive and activated carbon(AC)as negative electrodes.The cell delivered an energy density of 52.5 Wh kg^(-1)at a power density of 1488 W kg^(-1)with excellent cyclic stability of 84.9%over 8000 cycles.The electrochemical performance enhancement corresponds to a 3D structure,high electrochemical active sites,and improved charge transportation at the electrode/electrolyte interface.Thus,the present work offers an easy approach and architectural design for high-performance HSC.

Lithiation-induced controllable vacancy engineering for developing highly active Ni_(3)Se_(2) as a high-rate and large-capacity battery-type cathode in hybrid supercapacitors

The poor rate capability and low capacity are huge barriers to realize the commercial applications of battery-type transition metal compounds(TMCs) cathode.Herein,numerous Se vacancy defects are introduced into the Ni_(3)Se_(2)lamellas by pre-lithiation technique,which can be acted as a novel class of battery-type cathode for hybrid supercapacitors.Appropriately modulating the contents of the preembedded lithium(Li) ions can induce a controllable vacancy content in the series of as-prepared products,effectively endowing a fast reaction kinetic and high activity for the cathode.Benefiting from the distinct design,the optimized cathode(Li2-Ni_(3)Se_(2)) presents a high specific capacity of 236 mA h g^(-1)at1 A g^(-1),importantly,it can still possess 117 mA h g^(-1)when the current density is increased up to 100A g^(-1),exhibiting relatively high rate capability.It is much superior to other battery-type TMC cathodes reported in previous studies.Moreover,the cathode also shows the excellent cycling stability with 92%capacity retention after 3,000 cycles.In addition,a hybrid supercapacitor(HSC) is assembled with the obtained Li2-Ni_(3)Se_(2)as the cathode and active carbon(AC) as the anode,which delivers a high energy density of 77 W h kg^(-1)at 4 kW kg^(-1)and long-term durability(90% capacitance retention after 10,000 cycles).Therefore,the strategy not only provides an effective way to realize the controllable vacancy content in TMCs for achieving high-perfo rmance cathodes for HSC,but also further promotes their large-scale applications in the energy storage fields.

A survey of hybrid energy devices based on supercapacitors

Developing multifunctional energy storage systems with high specific energy, high specific power and long cycling life has been the one of the most important research directions. Compared to batteries and traditional capacitors, supercapacitors possess more balanced performance with both high specific power and long cycle-life. Nevertheless, regular supercapacitors can only achieve energy storage without harvesting energy and the energy density is still not very high compared to batteries. Therefore, combining high specific energy and high specific power,long cycle-life and even fast self-charging into one cell has been a promising direction for future energy storage devices. The multifunctional hybrid supercapacitors like asymmetric supercapacitors, batteries/supercapacitors hybrid devices and self-charging hybrid supercapacitors have been widely studied recently. Carbon based electrodes are common materials used in all kinds of energy storage devices due to their fabulous electrical and mechanical properties. In this survey, the research progress of all kinds of hybrid supercapacitors using multiple effects and their working mechanisms are briefly reviewed. And their advantages and disadvantages are discussed. The hybrid supercapacitors have great application potential for portable electronics, wearable devices and implantable devices in the future.

Surface-engineered binder-free PEDOT shielded nickel magnesium selenide nanosheet arrays electrode for ultralong-life flexible quasi-solid-state hybrid supercapacitors

Together with the development of high-performance advanced electronics,flexible supercapacitors(SCs)with tailored nanostructures have great attraction.Electrochemically deposited nanosheet arrays of nickel magnesium selenide(NixMg3-xSe4,NMgS)with high capacitance provide high potentials as a positive electrode in flexible SCs.To further enhance their electrochemical properties and long-term cycling stability,a promising strategy of surface engineering with conducting polymer poly(3,4-ethylenedioxythiophene)(PEDOT)is proposed.The present work proposes the construction of PEDOT shielded NMgS(P@NMgS-2)on a flexible carbon cloth substrate via a hierarchical electrodeposition technique.Benefitting from the synergistic effect,the P@NMgS-2 exhibits an excellent areal capacitance value of 1440 mF cm^(-2)at 4 mA cm^(-2).A novel shape-adaptable polymer gel electrolyte-assisted flexible quasi-solid-state hybrid SC(FQHSC)device constructed with P@NMgS-2 as a positive electrode and activated carbon as a negative electrode demonstrates the maximum power and energy density values of 14.13 mW cm^(-2)and 0.18 mWh cm^(-2),respectively,followed by outstanding cycling stability(∼100%capacitance retention over 50,000 cycles).Furthermore,the FQHSC device successfully powered electronic devices with no serious degradation upon bending and twisting for wearable electronic applications.

Facile preparation of Nb_(2)O_(5) microspheres and their excellent electrochemical performance in aqueous zinc-ion hybrid supercapacitors

The aqueous solution-based zinc-ion hybrid supercapacitors(ZHSCs)have attracted immense attention as they are characterized by high power and energy densities.Electrode materials with high performance should be developed for ZHSCs to resolve power imbalances between capacitor-and battery-type electrode materials.To address this issue,Nb_(2)O_(5) microspheres(with the structure like sweet dumplings with exposed stuffing)were produced following a hydrothermal process which was followed by a high-temperature calcination process.The specific capacity of the as-synthesized Nb_(2)O_(5) microspheres was up to 324 F·g^(-1) when the current density was 0.1 A·g^(-1),and the long-term capacity retention was 85%at the end of 5000 cycles.The results revealed that the nanospheres could be used as battery-type electrode materials for the fabrication of ZHSCs.Nb_(2)O_(5)//AC ZHSCs were fabricated with Nb_(2)O_(5) microspheres as the negative electrode materials,and activated carbon(AC)was used as the positive electrode material.As a result,a specific capacity of 108 F·g^(-1) was achieved when the current density was 0.1 A·g^(-1).The power density was high(8020 W·kg^(-1))at 28 Wh·kg^(-1),and the energy density was high(60 Wh·kg^(-1))at 100 W·kg^(-1).The structurally novel Nb_(2)O_(5) microspheres can be potentially used for the development of the next-generation ZHSCs that exhibit excellent performance.

Synthesis of coal tar pitch-derived heteroatom-doped porous carbon materials for aqueous zinc-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors (ZHSs), which combine the superiority of batteries and supercapacitors, will become a new development direction in the field of energy storage. The development of ZHSs with high capacity and high stability can be further promoted by heteroatom doping or structural modification of cathode materials. Herein, N,O,P co-doped porous carbon materials were synthesized by a facile method using coal tar pitch as precursor, aluminum phosphate as template, and sodium hydroxide as activator. Due to the high specific surface area and abundant micropores, the heteroatom-doped porous carbon materials were employed as cathode for aqueous ZHSs to study the electrochemical performance. Benefitted from the rich micropores and heteroatom doping, the porous carbon electrodes exhibit an outstanding electrochemical performance and deliver a large specific capacitance of 113.3 mA h g􀀀 1 at 0.1 A g􀀀 1. In addition, the porous carbon electrode shows a high energy density of 64.9 Wh kg􀀀 1 and a high power density of 1.23 kW kg􀀀 1, which outperforms most aqueous ZHS energy storage systems previously reported. Interestingly, after 5000 cycles at 1 A g􀀀 1, the specific capacity is about 36% higher than the original capacity and the coulomb efficiency still remains nearly 100%. The article may provide a new insight into exploring cathode materials for high-performance aqueous rechargeable zinc-ion energy storage devices.