Flexible Zinc Research Articles

Recent advances and perspectives of 1D/2D carbon materials for high-performance flexible zinc ion batteries

This review provides a summary of recent advancements in 1D/2D carbon materials (carbon nanotubes, graphene, MXenes, and carbon fibers) for FZIBs. It mainly introduces the functions of 1D/2D carbon materials in enhancing the performance of FZIBs.

An Ultrafast Air Self-Charging Zinc Battery.

Air self-charging power systems possess the capability of energy harvesting, conversion, and storage simultaneously. However, in general, their self-charging rate is slow and the batteries cannot be oxidized to the fully charged state due to the weak oxidizability of O2 . Herein, an ultrafast air self-charging aqueous zinc battery is designed by constructing a polyaniline@Pt/C (PANI@Pt/C)composite cathode. The introduction of Pt/C catalyst endows the redox reaction between PANI and O2 with fast reaction kinetics and extended redox potential difference. Therefore, the self-charging rate of the Zn/PANI@Pt/C batteries is effectively accelerated and they can be self-charged to fully charged state. Furthermore, the PANI can be recharged by O2 simultaneously during discharging process to compensate the consumed electrical energy, achieving prolonged energy supply. In addition, the PANI@Pt/C cathodes can be directly used as the cathodes of flexible self-charging zinc batteries due to their excellent mechanical properties. As a proof of concept, flexible soft-packaged Zn/PANI@Pt/C batteries are fabricated and displayed stable electrochemical performance and self-rechargeability even at different bending states. A route is provided here to design ultrafast chemical self-charging energy storage devices and the horizons of flexible energy storage devices are broadened.

Flexible low-temperature zinc ion supercapacitor based on gel electrolyte with α-MnO2@rGO electrode

Zinc ion supercapacitors (ZSCs) are considered to be a new generation of energy storage device because of their low cost and battery-like performance. However, the uncontrollable structural deformation and poor cyclic stability make them a great challenge in practical applications. Herein, we developed a flexible quasi-solid-state ZSC assembled with gel electrolytes, porous α-MnO2@reduced graphene oxide(α-MnO2@rGO) cathode, and activated carbon/carbon cloth (AC/CC) anode. The gel electrolytes containing polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), and ethylene glycol (EG) shows great mechanical properties, good electrical conductivity, and can afford a wide electrochemical potential window. The flexible ZSC exhibited an excellent specific capacitance of 575.5 mF cm−2 at a current density of 6 mA cm−2 and good stability during bending test. More important, the device can achieve stable electrochemical properties at low temperature of −20 °C, cycle retention can maintain 89.189 % even after 5000 cycles. This work has successfully proposed an energy storage system with excellent performance, which provides possibilities for multi-scene applications of flexible devices.

Chemically cross-linked Poly(vinyl alcohol) and halloysite nanotubes as composite separator for stable Zn-organic battery

Zn-organic batteries (ZOBs) are promising energy-storage device owing to their merits of high capacity, low cost, and sustainability. However, their electrochemical performance is limited by irreversible organic small-molecular cathode due to the shuttle effect of discharge intermediates. Here, we report on the use of a chemically cross-linked poly(vinyl alcohol) films with halloysite nanotubes (GA-PVA/HNTs) as a separator for ZOBs. The GA-PVA/HNTs separator with intrinsic electro-negativity of HNTs act as permselective shield for negatively redox organic resultants, thereby preventing the shuttling effect without sacrificing power. In order to illustrate the superior performance of the GA-PVA/HNTs separator, a battery using as-prepared GA-PVA/HNTs separator, benzoquinone (BQ) as the cathode and Zn as the anode displays a high initial capacity (435 mAh g−1 at 0.3C) and superior cycle performance (98% capacity retention after 200 cycles at 3C). Moreover, a flexible Zn||BQ battery based on GA-PVA/HNTs separator is constructed, achieving a highly stable capacity of 431 mAh g−1 under different bending conditions. This work promotes the development of high absorptivity separator for the flexible zinc batteries.

Transparent and flexible zinc oxide-based thin-film diodes and thin-film transistors: A review

Electronics today has evolved significantly, including its application in transparent and flexible devices. Flexible electronics offers new product concepts, including low production cost, low energy consumption, and sustainable and environmentally friendly materials. This concept leads to the development of novel materials that realize today’s requirements. Incorporating optically transparent and flexible thin-film-based devices into the electronic circuitry helps in maintaining high conductivity along with achieving the similar electronic behavior of the conventional electronic gadgets. Thin-film diodes (TFDs) and thin-film transistors (TFTs) are the core materials to be incorporated as building blocks for flexible devices. Among them, oxide-based thin films have been marked to be significant because of their efficient electrical performance, low temperature processing, and device flexibility. The present article reviews the concepts and application of zinc oxide (ZnO) as the semiconducting material for flexible thin-film devices. We also review flexible and transparent TFDs and TFTs that are based prominently on ZnO as the semiconducting material. Furthermore, the present issues have also been addressed.

3D Printed Flexible Zinc Ion Micro‐Batteries with High Areal Capacity Toward Practical Application

AbstractPrinted zinc ion micro‐batteries (PZIMBs) possess characteristics such as miniaturization, customizability, and affordability, making them highly promising for the field of flexible electronic devices. Nevertheless, the current development of PZIMBs is seriously hindered by their limited areal capacity. In this study, PZIMBs with a high areal capacity are conducted based on 3D printing technology by optimizing the material properties, electrode ink formulation, and printing parameters. The cathode material, polyvinylpyrrolidone‐induced ammonium vanadate (P‐NVO) nanobelt, exhibits a high capacity of 457.3 mAh g−1 at 0.1 mA g−1, along with good cycling performance and rate capability. The double‐network hydrogel electrolyte, composed of crosslinked polyacrylamide‐polyvinylpyrrolidone (PAM‐PVP hydrogel electrolyte), demonstrates excellent ionic conductivity (107.22 mS cm−1), high stretchability (970%), and viscosity. The constructed PZIMBs exhibit a high areal capacity of 4.02 mAh cm−2 at 0.5 mA cm−2, along with good mechanical flexibility. Moreover, through the integration of PZIMBs with pressure sensors, an interactive system is developed that resembles electronic skin, and this integration enables practical applications of wearable devices. This study presents a novel approach for fabricating PZIMBs with high areal capacity, thereby contributing to and propelling the advancement of flexible energy storage.

High energy density flexible zinc–ion batteries enabled by polyaniline-encapsulated molybdenum-doped tungsten oxide nanorods as a zinc intercalation electrode

High energy density flexible zinc–ion batteries enabled by polyaniline-encapsulated molybdenum-doped tungsten oxide nanorods as a zinc intercalation electrode

Fully Printed Flexible Zinc Oxide Patch for Wearable UV Light Sensing

AbstractMetal oxide materials are widely adopted in UV sensing due to their advantages of reliability, stability, and high sensitivity. However, the fabrication of metal oxide films on flexible substrates using micro/nano printing techniques still poses challenges. Notably, inks containing oxide nanoparticles often lead to nozzle clogging during the printing process. In addition, methods relying on precursor solutions typically require high post‐processing temperatures that conventional flexible substrates cannot withstand. In this study, a novel precursor ink based on zinc amine hydroxide complexes is proposed, enabling post‐processing at a low temperature of 250 °C. Through a fully printed approach, a wearable UV sensor based on a zinc oxide nanofilm on a flexible substrate is successfully fabricated. The sensor exhibits outstanding sensitivity and rapid response characteristics. By incorporating silver nanoparticles into the ink, the baseline resistance of the sensitive material is adjusted. Furthermore, a smart patch utilizing the NFC communication protocol is developed, allowing for wireless, passive, and wearable UV detection. In this study, a process paradigm for fabricating metal oxide films on flexible substrates using micro/nano printing techniques is introduced, showcasing significant potential in the field of micro/nano sensor fabrication.

High-Performance Flexible Zinc–Air Batteries Enabled by a Sodium Polyacrylate-Based Gel Electrolyte Containing Graphene Oxide and Cellulose Nanofibers

High-Performance Flexible Zinc–Air Batteries Enabled by a Sodium Polyacrylate-Based Gel Electrolyte Containing Graphene Oxide and Cellulose Nanofibers

A braided flexible Zn–MnO2 yarn battery based on cobweb-like carbonized polypyrrole modified carbon fiber electrodes

Flexible zinc ion batteries (ZIBs) are promising candidates for energy storage devices because of high safety and low cost. Carbon fibers (CFs) are ideal current collectors for ZIBs due to their good flexibility, electrical conductivity and corrosion resistance. Herein, a novel CFs-based current collector is proposed. At first, the inertness and non-polarity of CFs were significantly modified by activating and etching to obtain a multi-layered porous structure. Thereafter, carbonized polypyrrole (CPPy) nanowire conductive networks were built up on etched carbon fibers (ECFs) by electrochemical in situ growth and carbonization. Based on the CPPy network, MnO2 nanoflowers were grown firmly by the hydrothermal method to construct multi-layer MnO2@CPPy@ECFs composite electrode. The multi-layered 3D CPPy conductive network is rooted in MnO2, providing a dedicated transmission path for both electrons and ions during electrochemical redox reactions. The MnO2@CPPy@ECFs electrode had an initial capacity of 346.1 mA h·g−1 at 0.1 A g−1 and 252.8 mA h·g−1 after 800 cycles. In addition, the integrated flexible Zn–MnO2 2D fabric battery with MnO2@CPPy@ECFs fabric cathode shows a specific capacity of 254.7 mA h·g−1 at 0.1 A g−1. Finally, a flexible Zn–MnO2 yarn battery with high flexibility, shape adaptability, structural integrity and good mechanical stability was fabricated by the 2D braid method. The initial specific capacity of the flexible Zn–MnO2 yarn battery is 111.7 mA h·g−1 at 0.1C, which also presents a remarkable volumetric energy density of 30.5 mW h cm−3. This work opens up a new pathway for the rational design of flexible electrodes for wearable ZIBs.

Bifunctional Oxygen Electrocatalyst of Co4N and Nitrogen‐Doped Carbon Nanowalls/Diamond for High‐Performance Flexible Zinc–Air Batteries

AbstractRational design of heterogeneous catalysts with unique structural and electronic properties is one of the major challenges to improve the activity toward the reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), the bottleneck in the construction of air cathodes for the next‐generation flexible zinc–air batteries (ZABs). Herein, density functional theory calculations are combined with experimental attempts to exploit the roles of the electronic effects at the interface between Co4N nanoparticles and nitrogen‐doped carbon nanowalls/diamond (d‐NCNWs/D) toward the ORR and OER activities. The vacancy defect‐induced Co‐pyridinic N─C bond optimizes the electronic structure of Co 3d orbitals and balances the adsorption energies of intermediates along the reaction pathways. Consequently, as‐synthesized Co4N@d‐NCNWs/D composites exhibit superior bifunctional oxygen catalytic activity. The overpotential of the OER is as low as 340 mV at 10 mA cm−2 and the high half‐wave potential reaches 0.83 V for the ORR. As a binder‐free and flexible ZABs cathode, this composite exhibits an open circuit voltage of 1.41 V and excellent bendable stability, proving its promising potential for the assembly of wearable devices. This work offers theoretical evidence and a controllable strategy to design high‐performance ZAB cathodes for their application in smart electronic devices.

Stretchable, anti-drying, and self-healing hydrogel electrolytes for thermal adaptive zinc–air batteries with robust electrolyte/electrode interfaces

Hydrogel electrolytes possessing excellent elasticity and ionic conductivity have garnered significant attention in the realm of flexible zinc–air batteries (ZABs). Nonetheless, the inherent issue of hydrogel electrolyte dehydration when exposed to air, particularly under high temperatures, poses a significant obstacle to the practical application of hydrogel-based ZABs. To address this challenge, a novel hydrogel electrolyte is fabricated by polymerization of (3-acrylamidopropyl) trimethylammonium chloride (ATAC)/ethylene glycol (EG) solution containing polyacrylic acid (PAA). The hydrogen bonds between poly (ATAC) (PATAC) with EG and PAA chains can supply dynamic network that imparts outstanding self-healing properties to the hydrogel electrolytes. Moreover, the presence of water molecules, firmly bound and confined within the dense hydrogen bond networks, endows the hydrogel electrolytes with a unique anti-drying characteristic even at high temperatures. Additionally, the adhesion capability allows the hydrogel electrolytes to form a tight bond with the electrodes. Consequently, the resulting zinc–air batteries exhibit superior electrochemical stability under various deformations and elevated temperatures of 50 °C. This study introduces a promising avenue for the development of flexible zinc–air batteries that demonstrate superior performance and adaptability to environmental conditions.

Rational design of 1D nanowires with internal void space assembled by MnO@C nanoreactors as efficient cathodes for flexible zinc ion batteries

MnO-based materials are one of the most promising cathodes for rechargeable zinc ion batteries (ZIBs) owing to their high energy density and abundant resources. However, the notorious electronic conductivity and large volumetric expansion issues have severely restricted their practical application. Herein, 1D nanowires (NWs) with abundant internal void space, composed of ultra-small MnO@C nanoreactors, is proposed to get rid of the above dilemma. Specifically, carbon layer dramatically enhances electrically conductive, the elaborated constructed void space between MnO@C nanoreactors effectively avoid the physical clogging and restacking of MnO, relieving the strain upon charge and discharge process, and ultimately ensuring cathode satisfactory integrity maintenance, different from traditional 1D NWs composite architecture. As expected, the NWs constructed by MnO@C nanoreactors exhibit the superior cycling stability (102.9% capacity retention after 2000 cycles) and good rate performance. Moreover, we firstly construct freestanding MnO@C NWs/CNTs film as cathode and assemble a quasi-solid-state ZIB by using soaking-free PAM hydrogel electrolyte. The device without extra binders and additives affords an impressive reversible capacity of 357.2 mAh g−1 at 0.1 A g−1, and remarkable volumetric energy density of 20.8 mWh cm−3 (higher than commercial Li thin-film battery). Furthermore, our soft-packaged ZIBs also exhibits satisfactory flexibility and high safety.

Anchoring Polar Organic Molecules in Defective Ammonium Vanadate for High-Performance Flexible Aqueous Zinc-Ion Battery.

Ammonium vanadate (NVO) often has unsatisfactory electrochemical performance due to the irreversible removal of NH4 + during the reaction. Herein, layered DMF-NVO nanoflake arrays (NFAs) grown on highly conductive carbon cloth (CC) are employed as the binder-free cathode (DMF-NVO NFAs/CC), which produces an enlarged interlayer spacing of 12.6Å (against 9.5 Å for NH4 V4 O10 ) by effective N, N-dimethylformamide (DMF) intercalation. Furthermore, the strong attraction of highly polar carbonyl and ammonium ions in DMF can stabilize the lattice structure, and low-polar alkyl groups can interact with the weak electrostatic generated by Zn2+ , which allows Zn2+ to be freely intercalated. The DMF-NVO NFAs/CC//Zn battery exhibits an impressive high capacity of 536 mAh g-1 at 0.5Ag-1 , excellent rate capability, and cycling performance. The results of density functional theory simulation demonstrate that the intercalation of DMF can significantly reduce the band gap and the diffusion barrier of Zn2+ , and can also accommodate more Zn2+ . The assembled flexible aqueous rechargeable zinc ion batteries (FARZIBs) exhibit outstanding energy density and power density, up to 436Wh kg-1 at 400W kg-1 , and still remains 180Wh kg-1 at 4000W kg-1 . This work can provide a reference for the design of cathode materials for high-performance FARZIBs.

A promising approach to prepare gel electrolyte and electrocatalyst derived from natural long-staple cotton for high-performance flexible Zn-air battery

Due to the high energy density and risk-free operation, flexible zinc–air batteries (ZABs) have the potential to be energy sources for wearable electronic devices. Nonetheless, the performance of quasi-solid-state gel electrolytes diminishes progressively throughout the ion-exchange process, primarily due to water evaporation on the exposed cathode side, which shortens the useful lifetime of ZABs. Herein, we propose a distinctive gel polymer electrolyte membrane comprising cotton fiber (CF) from natural long-staple cotton and polyvinyl acetate (PVA) to effectively extend the battery lifespan, which is due to that the addition of CF improves surface wettability, liquid absorption and retention, and ionic conductivity (1.53 × 10−2 S cm−1) compared with single PVA electrolyte membrane. We also prepare a composite electrocatalyst (Co-N-C@GCF-950) by pyrolyzing the precursor of ZIF-67 in situ grown on the cotton fiber at 950 ℃. The flexible ZAB assembled with Co-N-C@GCF-950 as the cathode electrocatalyst and the CF-PVA membrane as the gel electrolyte shows a high open-circuit voltage of 1.5 V, and a stable charge-discharge voltage gap of 0.8 V for 11-h lifespan at a current density of 2 mA cm−2 under various bending conditions, which guides the future way of the application potential of environmental cotton fibers in the multiaspects for flexible metal-air batteries.

Enhanced Semi-interpenetrating Network Quasi-solid Electrolytes Modified by Hollow Porous Nanofibers for Flexible Zinc–Air Batteries

Enhanced Semi-interpenetrating Network Quasi-solid Electrolytes Modified by Hollow Porous Nanofibers for Flexible Zinc–Air Batteries

Highly Sensitive and Wearable ZnO–Graphene Nanocomposite-Based Strain Sensors for Human Motion Detection

Flexible electronic sensors have garnered considerable interest in wearable health-monitoring devices and electronic skin. In this work, a simple method for the fabrication of flexible zinc oxide-graphene nanoplatelets (ZnO-GNP) nanocomposite based strain sensors has been proposed. The sensing element was deposited on polydimethylsiloxane (PDMS) substrate by a facile spin and peel strategy to yield flexible sandwiched sensors. Effect of varying the blending ratio of the constituents on the electromechanical responses of the sensors was studied. The sensors exhibited high stretchability, good sensitivity, high reversibility and superior stability under tensile and bending loads. The flexible nanocomposite sensors were able to detect extensive human movements such as bending of the elbow, wrist and finger and also subtle motions such as eye blinking, wrist pulse and phonation. Owing to the facile and economical fabrication method, high sensitivity and good reversibility, the ZnO-GNP sensors have high prospect of application in wearable health monitoring devices, robotics and various forms of human-machine interface.

A thin flexible zinc battery enabled by simultaneously electro-depositing both electrodes in acetate electrolytes

Electrolytic batteries with the anode or cathode formed by electro-deposition from the electrolytes show promising potential for simplifying the fabrication process of flexible and micro-size rechargeable batteries. Thin flexible zinc batteries with both anode and cathode electro-deposited simultaneously are demonstrated and investigated here. We find that the acetate anions (Ac-) show excellent electro-depositing efficiency for manganese oxide cathodes, which enable a capacity of 0.26 mAh/cm2 with only carbon current collectors and electrolytes.

Vacancy engineering of MoS2−X @NCNTs for efficient storage of zinc ions

Zinc-ion batteries are receiving interest due to their high level of safety and eco-friendliness. However, the sluggish diffusion kinetics of zinc ions in the electrode limit its practical application. In this paper, rapid Zn2+ diffusion in the MoS2−X @NCNTs cathode is achieved by utilizing the S vacancies generated under a H2/Ar atmosphere and N-doped carbon nanotubes (NCNTs) derived from the pyrolysis of polyethylene and melamine. The presence of S vacancies significantly reduces the diffusion barrier of Zn2+, thereby promoting the transport of Zn2+ ions. MoS2−X @NCNTs cathode demonstrates an impressive discharge specific capacity of 220 mAh g−1 (0.1 A g−1) and a remarkable reversible capacity of 173 mAh g−1 (3 A g−1). Furthermore, the reduced adsorption energy of MoS2−X nanosheets leads to Zn2+ tending to preferentially insert S vacancies, resulting in a larger capacity than pure MoS2. This work realizes efficient storage of Zn2+ in 2D disulfides through carbon frameworks and S vacancies. In addition, flexible zinc batteries with MoS2−X @NCNTs cathodes have promising applications in wearable devices.

Long-Range Regulation of Se Doping for Oxygen Reduction of Atomically Dispersed Sb Catalysts for Ultralow-Temperature Solid-State Zn–Air Batteries

Regulating the p-orbital valence electrons of atomically dispersed main-group metals to improve the inherent electrocatalytic activity has attracted extensive concerns. Herein, we designed and synthesized an atomically dispersed Sb–SeNC catalyst containing SbN2C2 and SeC2 structures, which have been identified by X-ray absorption spectroscopy and density functional theory (DFT) calculations. Sb–SeNC exhibits a high activity for the oxygen reduction reaction (ORR), and a Sb–SeNC-based flexible solid-state zinc–air battery (ZAB) can work efficiently at −40 °C, with a peak power density of 54.1 mW cm–2 and a rate discharge operation of about 44 h. DFT calculations further confirm the long-range regulation mechanism of the SeC2 moiety for the ORR of SbN2C2 and obtain the volcano relationship of Uonset vs the Se–N distance. When the Se–N distance is 7.4 Å, the adsorption ability of active site Sb can be regulated to an optimal state related to the RDS: *O → *OH, while the smaller Se–N distance in short-range would lead to the excessive attenuation of adsorption ability of active site and decrease of ORR activity, which therefore yields the long-range regulation effect of Se doping on the ORR activity of SbN2C2. This long-range regulation strategy may provide a promising approach to boost the catalytic activity of main-group metal catalysts to achieve its application in ultralow-temperature solid-state ZABs.