Zinc-ion Hybrid Supercapacitors Research Articles

Cellulose-based water-in-salt ZnBr2 hydrogels with multiple functions for energy storage devices

A new simple preparation method for water-in-salt-type cellulose hydrogels filled with ZnBr2 is reported. The ZnBr2 hydrogel electrolyte can be applied to zinc-ion hybrid supercapacitors and Zn-Br interfacial batteries. The water-in-salt ZnBr2 hydrogel serves as a stable electrolyte for good electrochemical performance in zinc-ion hybrid supercapacitors without redox reactions and can participate in the charging/discharging process of the Zn‒Br interfacial battery through the redox reaction of halogen anions. The assembled zinc-ion hybrid supercapacitor exhibits a specific capacitance of 241.8 F g-1 at 0.5 A g-1. Furthermore, after a 10000-cycle-long charging/discharging test at 5 A g-1, the coulombic efficiency is found at nearly 100%. The interfacial battery reaches the highest energy efficiency of 66% at a current density of 3 mA cm-2 at 0–1.8 V and displays a good cycle life with an 88% average coulombic efficiency at 3 mA cm-2. This work expands the application of hydrogels and provides new possibilities for optimizing the high performance of electrolytes.

Win-Win Strategies Enable Efficient Anode-less Zinc-ion Hybrid Supercapacitors.

Boosting the energy and power densities of electrochemical energy storage (EES) devices to broaden their practicality is of great significance and emergently desirable. Recently, the EES cells with an anode-free concept have been announced to realize those targets. Herein, 20 μm of a zincophilic layer prepared by blending ZIF-8 and sodium alginate (SA) is uniformly coated on Cu foil (Z8-SA@Cu) as an alternative anode for anode-less zinc-ion hybrid supercapacitors (ALZHSCs). Contributing by the distinctive features evidenced by electrochemical measurements and post-mortem analyses: (1) less nucleation barrier and overpotential, (2) limited zincate formation, (3) improved Zn2+ flux and (4) efficient Zn plating/stripping, the as-prepared Z8-SA@Cu is rationally considered to be a promising anode for ALZHSCs. Encouragingly, the assembled ALZHSC device not only delivers an impressive rate capability (40 mAh/g at 1 mA/cm2 and 34 mAh/g at 10 mA/cm2) but also achieves the excellent cycling stability (capacity retention: 88% after 12,000 cycles at 5 mA). Most importantly, the ALZHSC device also reveals significant increases in gravimetric energy density and high-power ability as compared to the traditional ZHSCs.

Hydrogen-Bonded Ionic Co-Crystals for Fast Solid-State Zinc Ion Storage.

The development of new ionic conductors meeting the requirements of current solid-state devices is imminent but still challenging. Hydrogen-bonded ionic co-crystals (HICs) are multi-component crystals based on hydrogen bonding and Coulombic interactions. Due to the hydrogen bond network and unique features of ionic crystals, HICs have flexible skeletons. More importantly, anion vacancies on their surface can potentially help dissociate and adsorb excess anions, forming cation transport channels at grain boundaries. Here, it is demonstrated that a HIC optimized by adjusting the ratio of zinc salt and imidazole can construct grain boundary-based fast Zn2+ transport channels. The as-obtained HIC solid electrolyte possesses an unprecedentedly high ionic conductivity at room and low temperatures (≈11.2 mScm-1 at 25°C and ≈2.78mScm-1 at -40°C) with ultra-low activation energy (≈0.12eV), while restraining dendrite growth and exhibiting low overpotential even at a high current density (<200mV at 5.0mAcm-2) during Zn symmetric cell cycling. This HIC also allows solid-state Zn||covalent organic framework full cells to work at low temperatures, providing superior stability. More importantly, the HIC can even support zinc-ion hybrid supercapacitors to work, achieving extraordinary rate capability and a power density comparable to aqueous solution-based supercapacitors. This work provides a path for designing facilely prepared, low-cost, and environmentally friendly ionic conductors with extremely high ionic conductivity and excellent interface compatibility.

Solvent self-doping synthesis of nitrogen/oxygen co-doped porous carbon from cellulose as high performance material for multipurpose energy storage

Developing novel heteroatoms co-doped biomass porous carbon with low-cost, tunable physical/chemical properties, and environmental friendliness is an important candidate to face energy shortage and environmental pollution currently. Herein, a novel solvothermal avenue was designed using triethanolamine as self-doping solvent to treat rice straw powders with KOH. The rice straw with triethanolamine derived carbon (RSTCs-1) possessed hierarchical porous structure, N/O diatomic doping, and large specific surface area. The electrochemical energy storage performance of RSTCs-1 was evaluated in the systems of supercapacitors, aqueous zinc ion hybrid supercapacitors (AZHSs), and lithium-ion batteries (LIBs) respectively. As the results, the RSTCs-1 based symmetric supercapacitor exhibited the maximum energy density of ca. 98.4 Wh·kg−1 with the excellent cycling stability. Moreover, both RSTCs-1 AZHSs and RSTCs-1 LIBs achieved the relative high discharge specific capacities of ca. 407.1 and 1906.7 mAh·g−1 at current density of 0.1 A·g−1. These results highlighted the huge potential of the obtained with notable electrochemical performance acting as multifunctional electrode material for the different energy storage devices.

Engineering Zinc Ion Hybrid Supercapacitor Performance of Graphitic Carbon Nitride Embedded Iron Oxide (Hematite)

Zinc-ion hybrid supercapacitors (ZHSC) gain high traction due to the prosperous unification of batteries and supercapacitors. Especially with graphene discovery nano carbonaceous materials have been the most investigated types in energy storage (ES) utilization including ZHSC. Among carbonaceous materials, graphitic carbon nitride (g-C3N4) possessing polymeric layers, quasi graphene arouses extreme interest due to its low-impact structure with economical yet chemical and mechanical stability inflicted by high nitrogen contents. Herein, we aim to examine the g-C3N4 doping effect on the electrochemical performance of hematite (α-Fe2O3) for ZHSC application. The assembled ZHSC device managed to reach the potential window of 2.0 volts with an efficient specific capacitance (Sc) of 280 F g-1 at a current density of 1 A g-1. Moreover, the highest energy and power densities were 38.8 Wh kg-1 and 20 kW kg-1 respectively. With this remarkable efficiency, the α-Fe2O3/g-C3N4 composite material can be considered a promising cathode material for ZHSC

Flexible zinc-ion hybrid supercapacitor based on Co2+-doped polyaniline/V2O5 electrode

With the rapid advancement of renewable energy sources and portable electronic devices, the demand for high-performance energy storage systems is growing, driving continuous progress in supercapacitor technology. Zinc-ion hybrid supercapacitors (ZIHS), known for their higher safety, cost-effectiveness, and environmental friendliness, have become a hot research topic. Vanadium pentoxide (V2O5) possesses flexible multivalence, low cost, low toxicity, wide voltage window, high capacitance, and high energy density. However, its poor electrical conductivity and low cycling stability hinder its electrochemical performance, thus limiting its application in ZIHS. Here, we propose a novel strategy of incorporating Co2+ ions and conductive polyaniline (PANI) with V2O5 (CoVO-PANI) as cathode materials for ZIHS. The synergistic effect between cobalt ions and polyaniline have led to an expansion of the interlayer spacing in CoVO-PANI, which reduce the binding energy of Zn2+ ion insertion, decrease the diffusion barrier of Zn2+ ion insertion, and enhanced the electronic conductivity of the material for electron transport. In result, the CoVO-PANI@CC//2 M ZnSO4//AC@CC can reach the areal capacitance of 847.3 mF cm−2 at 1 mA cm−2. Following 2000 times at 50 mA cm−2, the CoVO-PANI@CC//2 M ZnSO4//AC@CC maintains a retention rate of 81.37 %, and can achieve a Coulombic efficiency of 100 %. The assembled flexible ZIHS device exhibits excellent flexibility and stability, with an areal capacitance of 775.6 mF cm−2 at 1 mA cm−2. This work demonstrates the tremendous potential of CoVO-PANI@CC as a cathode material for ZIHS.

MXene/Zwitterionic Hydrogel Oriented Anti‐freezing and High‐Performance Zinc–Ion Hybrid Supercapacitor

AbstractWith the wide application of portable electronic devices, zinc–ion hybrid supercapacitors (ZIHCs) have aroused great interest. However, balancing the low‐temperature performance and high energy density of ZIHCs remains a huge challenge. Herein, a zwitterionic hydrogel electrolyte (ZHE) loaded with carboxymethylcellulose and MXene is designed for ZIHCs, which shows excellent frost resistance and high output voltage. Carboxymethylcellulose and MXene enhance the flexibility and conductivity of the zwitterionic hydrogel electrolyte. Moreover, When ZnCl2 is introduced into a gel electrolyte, it induces an increase in the rate of ion transport, which enables a broadening of the operating temperature of the hydrogel (−40 °C–25 °C). As a result, Zn//AC ZIHCs based on ZHE show a high voltage window of 2 V, a high energy density (specific capacity) of 137 Wh kg−1 (247 F g−1), and the potential for wearable devices. This study will provide an effective strategy for the design of hydrogel ZIHCs with wide voltage windows, high energy density, and high practicality.

Significant performance enhancement of Zn-ion hybrid supercapacitors based on microwave-assisted pyrolyzed active carbon via synergistic effect of NaHCO3 activation and CNT networks

Zinc-ion hybrid supercapacitors (ZIHSCs) represents a promising technological approach for large-scale energy storage with the combined advantages of supercapacitors and zinc-ion batteries. Unfortunately, it is still challengeable to quickly fabricate low-cost, high-performance carbonaceous cathode materials at relatively low temperature. To address such issues, herein, taking waste Eucommia ulmoides Oliver (EUO) wood as an example, we present a novel microwave-assisted carbonization (MWC) approach at relatively low temperature to quickly prepare active carbon, and we present a synergistic strategy to significantly enhance the electrochemical performance by introducing sodium bicarbonate activation (SA) and constructing conductive carbon nanotubes (CNT) networks. The MWC-SA@CNT hybrid exhibits outstanding specific capacitance of 344.2 F/g at 0.2 A/g within three-electrode system, much better than conventional high-temperature pyrolyzed AC, MWC carbon, and MWC-SA carbon. The superior performance of MWC-SA@CNT can be attributed to the synergistic effect of its large specific surface area of 1102.7 m2/g, high mesoporous percentage of 53.5%, and rich –OH and CO groups due to microwave-assisted carbonization and sodium bicarbonate activation, and rich electron transport paths due to the presence of CNT networks. Furthermore, ZIHSCs assembled by MWC-SA@CNT cathode could delivers impressive performance with excellent capacity (194.37 mA h/g at current density of 1 A/g), energy density (142.30 Wh/kg), and durability (capacitance retention rate of 97.65% after 5000 cycles). This work offers a rapid and low-temperature method for preparing wood-based active carbon with rich nanopores and strong conductivity to improve performance of Zinc ion storage.

Inhibiting the zinc anodes corrosion to achieve ultra-stable high temperature aqueous zinc-ion hybrid supercapacitors

The corrosion of zinc anode significantly undermines the stability of aqueous zinc-based energy storage devices (ZnESDs), potentially leading to cell failure even explosions. In this study, we mixed a high concentration electrolyte (21 m LiTFSI) with a conventional 2 m Zn(OTF)2 electrolyte to highly reduce the activity of solvent water, which can greatly suppress the corrosion of zinc anode at room temperature and high temperatures. We systematically studied the phenomenon of ZnWiS inhibiting zinc anode corrosion at different temperatures and investigated its principle through experiments and theoretical calculations. As a result, the Zn||Zn symmetric cells demonstrated remarkable stability, sustaining over 3642 h at room temperature and over 112 h at 80 °C. Moreover, the as assembled aqueous zinc ion hybrid supercapacitors (ZHSC) also exhibited excellent cycling stability for over 5220 h at room temperature and over 165 h at 80 °C. In contrast, ZHSC assembled with 2 m Zn(OTF)2 can only cycle 80 h at room temperature, and 9 h at 80 °C. These findings confirm that reducing water activity in the electrolyte effectively contributes to achieving highly stable aqueous ZnESDs, and the universality of this strategy offering promise for its application in various aqueous metal ion energy storage devices.

Low temperature resistant flexible zinc-ion hybrid supercapacitor

Zinc-ion hybrid supercapacitors (ZIHS) have high capacity and power density, as well as safety and stability. However, ZIHS are susceptible to electrolyte solidification and deactivation under low temperatures, resulting in rapid capacity degradation. Consequently, their practical use in cold environments is limited. In this study, solid organic hydrogels were prepared as electrolytes using ZnCl2 in a solution of ethylene glycol (EG) and deionized water (H2O), incorporating polyvinyl alcohol (PVA). The hydrogen bonding between PVA and EG effectively suppresses ice crystal formation and promotes the growth of PVA crystal domains. In addition, EG can also form hydrogen bonds with H2O molecules, further preventing H2O crystallization, thereby improving the low temperature resistance of the ZIHS. The results show that the specific capacitance of ZIHS prepared with MnO2 as cathode electrode material and active carbon (AC) as anode electrode material can reach 60 mF cm−2 at −30 °C, and the capacity retention rate can reach 81.2 % after 8000 cycles. In addition, it was found that ZIHS still had good stability after bending at different angles at −30 °C. The development of ZIHS with excellent flexibility and low-temperature resistance is crucial for advancing electronics capable of operating in cold environments.

A Comprehensive Evaluation of Biomass-Derived Activated Carbon Materials for Electrochemical Applications in Zinc-Ion Hybrid Supercapacitors

A Comprehensive Evaluation of Biomass-Derived Activated Carbon Materials for Electrochemical Applications in Zinc-Ion Hybrid Supercapacitors

Low-temperature resistant self-healing hydrogel electrolyte for dendrite-free flexible zinc-ion hybrid supercapacitors

Flexible zinc-ion hybrid supercapacitors (ZHSC), have great potential as a novel energy storage device, and the appropriate electrolyte with stable low-temperature resistance and high conductivity is crucial for its widespread practical application. Herein, a poly (vinyl alcohol) (PVA)- carboxymethylcellulose sodium salt (CMC) hydrogel electrolyte is prepared by the repeated freezing method, with the advantages of low-temperature resistance, high conductivity, excellent mechanical properties (stretching, compression and torsion), and a certain degree of self-healing function to resist the damage of tearing. The PVA main chain in the gel forms a semi-interpenetrating network with CMC, which improves the mechanical strength of the gel, as well as enhances the binding ability with Zn2+ and promotes the uniform distribution of Zn2+. The incorporation of Li+ into the polymer network disrupts the crystalline domains, enhancing the viscosity and self-healing properties of the gel while improving its low-temperature resistance and electrical conductivity. The conductivity of the gel at 25/-20 °C is 5.17/2.37 mS cm−1. In addition, ethylene glycol (EG) is added to the gel as an antifreeze agent to help the gel not freeze easily at low temperatures. A low-temperature flexible ZHSC are prepared using PVA-CMC/Zn(CF3SO3)2/Li+/EG hydrogel electrolytes and carbonized ZIF-8 (HC) as the electrode. When at a current density of 2 mA cm−2, the device exhibits a specific capacitance of 282.7 mF cm−2 (141.4 F g−1) at room temperature, 270.4 mF cm−2 (135.2 F g−1) at −20 °C and even 61.7 mF cm−2 (135.2 F g-1) at −30 °C. Furthermore, the hydrogel electrolyte can efficiently inhibit the growth of zinc anode dendrites, thus guarantee the good capacitance retention of 81.7 % at 25 °C for 10,000 cycles and a coulombic efficiency of approximately 100 %. The device is also electrochemically stable under various bending conditions, and can power the timer at −30 °C, demonstrating new possibilities for the low-temperature flexible ZHSC.

Lotus leaf-derived capacitive carbon for zinc-ion hybrid supercapacitors prepared by one-step molten salt carbonization

Lotus leaf-derived capacitive carbon for zinc-ion hybrid supercapacitors prepared by one-step molten salt carbonization

Sodium anthraquinone-2-sulfonate combined with biomass porous carbon for high-performance zinc-ion hybrid supercapacitors

Zinc ion hybrid supercapacitors (ZIHSCs) can have their energy density raised by coupling high-capacity molecules with porous carbon, as demonstrated by research. However, few studies on the effect of introduction strategies of these molecules have been conducted on ZIHSC performance. Herein, sodium anthraquinone-2-sulfonate (AQS) are introduced into porous carbon (TAC) by one-step hydrothermal strategy to prepare the composites (TAC/AQS (W)). TAC/AQS (M) composites synthesized by physical mixing method as control samples. When used as the cathode material for aqueous ZIHSCs, TAC/AQS-1 (W) with the best mass ratio of AQS and TAC has a high specific capacitance of 310.89 mAh g−1 at 0.2 A g−1 and retains 89.17 % of its capacity after 20,000 cycles of the charge and discharge test, while those of TAC/AQS-0.5 (M) is 284.60 mAh g−1 and 10.09 %. Furthermore, TAC/AQS-1 (W) can achieve energy density of 295.35 Wh kg−1 and that of TAC/AQS-0.5 (M) is only 256.14 Wh kg−1. These results demonstrate that the way of introducing AQS affect the electrochemical properties of ZIHSC. The main reason for the difference in performance of two approaches is that the hydrothermal method makes AQS and TAC combine into a single solid phase with π-π non-covalent bonds, while the physical method is only a simple mechanical mixing of two phases.

N/O co-doped poly(γ-glutamic acid)/Ni2+/melamine/chitosan nanoparticle-based hollow graphite carbon spheres for aqueous zinc-ion hybrid supercapacitors

Hollow carbon spheres (HCSs) have attracted broad attention in aqueous zinc-ion hybrid supercapacitors (ZIHSCs) owing to their distinctive properties. However, traditional methods for fabricating HCSs face limitations, including complex multistep procedures, the use of corrosive chemicals, and stringent reaction conditions. In this work, biomass-based poly(γ-glutamic acid)/Ni2+/melamine/chitosan nanoparticles were used as the precursors to fabricate N/O co-doped hollow graphite carbon spheres (HGCSs). Thanks to the appropriate hydrophilic characteristic, specific surface area, pore size distribution, and electrical conductivity, the fabricated HGCSs cathode exhibited superior electrochemical properties. The assembled HGCSs-based ZIHSCs device showed a satisfactory specific capacitance of 133.2 mAh·g−1 at a current density of 1.0 A·g−1, high energy densities of 75.2 Wh·kg−1 at 10,000 W·kg−1 and 107.9 Wh·kg−1 at 1000 W·kg−1, respectively. Additionally, the assembled HGCSs-based ZIHSCs device displayed an exceptional cycling stability, enduring up to 10,000 cycles at 0.5 A·g−1 with a capacity retention rate of 98.1 %. This work provides a facile and novel strategy to prepare superior electrochemical performance biomass-based HGCSs cathode for ZIHSCs.

Chitin and Cellulose as Constituents of Efficient, Sustainable, and Flexible Zinc-Ion Hybrid Supercapacitors

A zinc-ion hybrid supercapacitor (ZIHS) is a prospective energy storage device featuring cost-effectiveness, operational safety, environmental friendliness, high-power performance, and satisfied energy density.1 The sustainability of this ZIHS technology is even improved by introducing biopolymer constituents into the cell construction.2 Herein, efficient, sustainable, and flexible ZIHSs employing polysaccharide (chitin- or cellulose-based) components are developed.3 Using green ionic liquid solvents, biopolymer-bound, activated carbon-based cathode materials and hydrogel biopolymer electrolytes containing conductive zinc salts are obtained. According to systematical characterization results, the prepared materials possess favorable functional properties. Biopolymer binders provide homogeneity and integrity within the electrode network and high adhesion to the surface of the current collector. Depending on the type of zinc salt, hydrogel biopolymer electrolytes display high ionic conductivity (up to 46 mS cm−1), expanded electrochemical stability window (up to ca. 2.8 V), and zinc dendrites growth suppression. Biopolymer components assembled with zinc foil electrodes operate efficiently in both coin and pouch ZIHS cell configurations, providing satisfactory energy (45–50 Wh kg−1) and high power (10–20 kW kg−1) density combined with excellent cycle stability. Moreover, these ZIHS pouch-type devices exhibit superior durability and flexibility, withstanding mechanical stress up to 150° bending states with at least 90% of capacitance retention. It suggests a prospect for their application in wearable electronics.4 References(1) Wang, Y.; Sun, S.; Wu, X.; Liang, H.; Zhang, W. Status and Opportunities of Zinc Ion Hybrid Capacitors: Focus on Carbon Materials, Current Collectors, and Separators. Nano-Micro Lett. 2023, 15 (1), 78.(2) Kasprzak, D.; Mayorga-Martinez, C. C.; Pumera, M. Sustainable and Flexible Energy Storage Devices : A Review. Energy & Fuels 2023, 37, 74–97.(3) Kasprzak, D.; Liu, J. Chitin and Cellulose as Constituents of Efficient, Sustainable, and Flexible Zinc-Ion Hybrid Supercapacitors. Sustain. Mater. Technol. 2023, 38, e00726.(4) Dubal, D. P.; Chodankar, N. R.; Kim, D. H.; Gomez-Romero, P. Towards Flexible Solid-State Supercapacitors for Smart and Wearable Electronics. Chem. Soc. Rev. 2018, 47 (6), 2065–2129. Figure 1. Graphical abstract of the research on biopolymer-based Zn-ion hybrid supercapacitors. Figure 1

Pulsed laser-modified zinc anode with improved dendrite and corrosion resistance for sustainable high performance zinc ion hybrid supercapacitors

This research explores the development and evaluation of zinc ion hybrid supercapacitors (ZIHSCs) with a focus on the enhanced performance and low corrosion attributes of pulsed laser-modified zinc anodes compared to their non-modified counterparts. These anodes, paired with cathodes crafted from activated carbon derived from jute sticks on graphite foil, were immersed in a 2 M zinc sulfate electrolyte. A pivotal aspect of the study is improving the electrochemical properties and corrosion resistance of zinc anodes achieved through precise pulsed laser modification. Extensive electrochemical testing was conducted to assess the capacitive behavior, energy storage capabilities, and durability of the supercapacitors during prolonged cycling. Hence, using the laser modified anode, we attain remarkable stability in Zn||Zn symmetric cells for 1000 h at high current density of 10 mA cm−2 with a capacity of 1 mAh cm−2, and ZIHSCs achieving specific capicitance up to 287 F/g at a current density of 0.1 A/g, and reaching an energy density of 102 Wh/kg while sustaining a power density of 80 W/kg. After 10,000 galvanostatic charge-discharge cycles, these supercapacitors maintained high capacitance values, underscoring their resilience. Notably, charge transfer resistance reduction, improved ion diffusion and enhanced corrosion resistance contributes to the supercapacitors' longevity and efficiency, which can be attributed to these anodes laser-induced surface alterations. This study highlights the crucial role of pulsed laser-modified zinc anodes in advancing ZIHSCs performance, marking a significant step towards achieving efficient and sustainable energy storage solutions.

Biomass-tar-derived oxygen-enriched porous carbon as a high-performance carbon electrode material for double electric layer and zinc-ion hybrid supercapacitor

Carbon-based capacitor electrodes have the advantages of high capacitance value, superior recyclability, and inexpensive raw materials, which fuel the application of capacitors in large-scale energy storage. Biomass tar is a hazardous waste that can be recycled as a low-cost carbon electrode precursor for capacitors, due to its retaining biomass-based heteroatom. In this study, hierarchically porous carbon with cross-linked structure was fabricated by using a nano-Al2O3 template combined with the KOH activation technique, in which the γ-Al2O3 has a size of only 10 nm with high specific surface area, thus optimizing the pore structure of the carbon material. The resulting optimal material, BTC-0.2-2-800, contains abundant pore structure and extremely high oxygen content, delivers low resistance and excellent rate performance with high specific capacitance of 292.1 F g−1 and 221.7 F g−1 at 1 A g−1 and 20 A g−1, respectively, in double electric layer supercapacitors (EDLCs). Besides, no significant capacity degradation after 10,000 charging and discharging cycles at 10 A g−1 was found. The two-electrode device prepared using Na2SO4 electrolyte achieves a high energy density of 43.18 Wh kg−1 at the power density of 1000 W kg−1, which can light up a 2 V LED lamp. Moreover, Zinc-ion hybrid supercapacitor (ZIHSC) fabricated with BTC-0.2-2-800 carbon electrode accounts for the energy densities of 69.82 Wh kg−1 and 49.39 Wh kg−1 at the power densities of 40 W kg−1 and 400 W kg−1, respectively. This study reveals the great potential of biomass-tar-derived carbon as a high-performance electrode material, which may provide an opportunities for the resource utilization of hazardous wastes.

Tough and temperature-tolerance cellulose/polyacrylic acid/bentonite hydrogel with high ionic conductivity enables self-powered triboelectric wearable electronic devices

Solid-state zinc-ion hybrid supercapacitors (ZHSCs) featuring hydrogel electrolytes have become ideal for large-scale flexible energy storage. However, existing polyacrylic acid (PAA) hydrogel electrolytes often lack the combined traits of ionic conductivity, mechanical robustness, and temperature tolerance. Herein, a versatile PAA-based hydrogel electrolyte (ACBH-Zn) containing a ZnCl2-cellulose solution and bentonite (BT) is delivered, facilitated by cooperative coordination bonds and hydrogen bonds. The coordination bonds between Zn2+ and −COOH of PAA, in conjunction with cellulose and BT, alongside the abundant hydrogen bonds within cellulose and PAA, are conducive to upgrading mechanical strength and ionic conductivity, while the BT's lamellar structure further provides sufficient ion migration channels. Consequently, the ACBH-Zn showcases exceptional mechanical properties, satisfying ionic conductivity (88.9 mS cm−1), and excellent temperature tolerance at −60 °C (30.3 mS cm−1). The ACBH-ZHSC, when assembled, attains a remarkable maximum energy density (323.4 Wh kg−1), maintaining an impressive capacity retention rate (92 %) even after undergoing 10,000 cycles at 10.0 A g−1. Furthermore, the assembled self-powered triboelectric wearable electronic device effectively converts mechanical energy from human movement into electrical energy, enabling efficient storage and utilization, and offering promising insights into the application of flexible wearable devices.

Preparation of photoreactive cathodes from copper-based metal-organic frameworks and their application in aqueous zinc-ion hybrid supercapacitors

To further enhance the energy density of aqueous zinc-ion hybrid supercapacitors, this paper verifies the feasibility of using copper catecholate (Cu-CAT) a copper-based metal-organic framework (MOF) characterized by strong broadband light absorption, good electrical conductivity, and a large specific surface area as a photoactive material. When used as the photoactive cathode in a Zn//Cu-CAT@CC aqueous zinc-ion hybrid supercapacitor, it can convert and store solar energy in the electrodes. Under sunlight, at a current density of 1 mA cm2, the device's areal capacity reaches 0.162 mAh cm2, an 89.1% increase over the storage capacity without light. This not only opens up new areas for the application of Cu-CAT materials but also offers more possibilities for the development of aqueous zinc-ion hybrid supercapacitors.