Gel Electrolyte Research Articles

Polyvinylidene fluoride‐co‐hexafluoropropylene polymer gel electrolyte‐enabled dye‐sensitized solar cell for sustainable energy

AbstractDeveloped specifically to address leakage and stability concerns inherent in liquid electrolytes, this study presents a significant advancement in polymer gel electrolyte (PGE) formulation by combining potassium iodide (KI), ammonium iodide (AI) salts, and polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐co‐HFP) as a host polymer. The tape casting method was employed to deposit the standard TiO2 paste as the photoanode and platinum paste as the counter electrode. N3 dye was incorporated, and PVDF‐co‐HFP was used as the PGE between the electrodes. The conductivity of PGE was measured by using a digitized conductivity meter. The quasi solid‐state solar cell (QS‐DSSC) assembled using single salts (KI, and AI), and mixed cations PGE was examined via photocurrent–voltage characteristics, and electrochemical impedance spectroscopy. The augmented ionic conductivity directly influences the efficiency of DSSCs. Notably, incorporating a mixed salt (KI + AI) within the PGE enhances ionic conductivity compared to single‐salt‐based counterparts. The resultant DSSCs using mixed salt PGE exhibit a Voc of 600 mV, Jsc of 1.01 mA/cm2, FF of 0.6089, and an efficiency of 0.369%, outperforming those using KI or AI. This highlights the perceptible advantages of employing this innovative electrolyte composition to enhance solar cell performance.

Porous Wood Composite as a Green Approach for Enhancing Electrochemical Performance of Gel Polymer Electrolytes for Supercapacitors.

Delignified wood (DW) is a kind of environment-friendly porous material, and its unique hierarchical orous structure and excellent wettability are conducive to the rapid transfer and storage of ions, which can be used as electrolyte matrix of supercapacitors. In order to solve the deficiency of mechanical properties of DW as electrolyte materials, a novel cross-linked polyurethane (CPU) with high water absorption is designed as a reinforced matrix to improve the mechanical properties of electrolytes while maintaining high ionic conductivity. First, DW is immersed in CPU precursor solution, and the DW/CPU composite (W-CPC) is obtained by thermal crosslinking. Finally, W-CPC is soaked in 1 M LiClO4 aqueous electrolyte to obtain the composite gel polymer electrolyte (W-CPC-GPE). Benefiting from the good hydrophilicity of W-CPC, the anisotropic vertical channels inside the DW, and the synergism of hydrogen bond and covalent bond. The highest ionic conductivity and mechanical strength of W-CPC-GPE are 3.5×10-2 S cm-1 and 0.67 MPa, respectively. The W-CPC-5-G based supercapacitor exhibits a high specific capacitance of 146.52 F g-1 and favorable capacitance retention rate of 90.7 % after 5000 cycles. The results show that compounding with DW is an efficient and green way to develop high-performance gel polymer electrolytes for supercapacitors.

Electrodeposited Zn-Mn on three-dimensional electrodes as anodes in liquid and quasi-solid-state zinc-air batteries

Zinc-air batteries (ZABs) are eco-friendly and sustainable energy storage devices. There are different challenges to overcome in ZABs, where anodic issues such as shape changes, passivation, self-corrosion, and dendrite formation require urgent solutions. In this work, Zn and Zn-Mn alloys were electrodeposited on three-dimensional porous carbon electrodes varying the Mn composition (2, 20 and 40 g L−1) and studying its effect during the operation of a 6 M KOH liquid ZAB and a quasi-solid-state ZAB based on poly(vinyl alcohol)/poly(acrylic acid) PVA/PAA gel polymer electrolyte (GPE). Scanning electron microscopy (SEM) images indicated that Zn and Zn-Mn were deposited as platelet-like bi-dimensional structures. Additionally, the use of 20 and 40 g L−1 of the Mn precursor resulted in larger Zn deposition covering the 3D structure of the carbon paper. Elemental analysis indicated that the Mn content in Zn-Mn was 1.3, 2.4 and 6 %. In the aqueous ZAB, the Zn-Mn with 2.4 % Mn enabled to increase the maximum current density achieving the highest power density of 45 mW cm⁻2. In QSS-ZAB, Zn-Mn at 1.3 and 2.4. % Mn displayed higher stability to recovery after demanding different current densities, while the first anode displayed higher cyclability, presenting a similar round trip after 240 charge/discharge cycles This ZAB was maintained functional during 290 cycles vs. 120 cycles for Zn foil. The rechargeability was improved because of the decrease in Zn dendritic growth and passivation.

Light-weight flexible symmetric supercapacitors based on magnesium-zinc codoped MnO2 nanostructures on carbon cloth as enhanced-performance binder-free electrodes

Developing advanced flexible supercapacitors with high energy and power density is a critical research goal. One promising approach involves combining manganese dioxide (MnO2) with a three-dimensional carbon substrate. This strategy leads to the creation of supercapacitor electrode materials that exhibit high specific capacitance, stability, and environmental friendliness. However, the challenge lies in addressing the low electrical conductivity of MnO2, which limits the rate of electron transfer. The incorporation of metal ions enhances the conductivity of manganese oxide, resulting in a significant increase in lattice defects. These defects create abundant active sites for energy storage. In this study, we developed flexible electrodes based on magnesium-doped MnO2, zinc-doped MnO2, and magnesium-zinc codoped MnO2 nanostructures deposited on carbon cloth (CC) via a one-step hydrothermal method. The supercapacitive behavior of these electrodes was investigated using CV and GCD measurements. The as-prepared electrodes exhibit good electrical conductivity, and their interconnected network structure, composed of sponge-shaped nanostructure layers, results in a large specific surface area. This network also facilitates efficient pathways for effective electron transport. The optimized Mg-Zn codoped MnO2@CC sample exhibits a high capacitance of 79.9 mF/cm² at 0.7 mA/cm² and good rate performance, reaching around 46.59 mF/cm² up to 1.5 mA/cm² in the three-electrode system. Notably, the areal capacitance values calculated from the CV curves for all Mg-Zn codoped MnO2@CC electrodes surpass those of Mg-doped MnO2@CC and Zn-doped MnO2@CC. A flexible symmetric supercapacitor assembled using the best Mg-Zn codoped MnO2@CC as both positive and negative electrodes and PVA-Na2SO4 gel electrolyte delivers a desirable energy density of 0.196 mWh/cm2 at 2.38 mW/cm2. Furthermore, this fabricated supercapacitor demonstrates a broad voltage window of 2.25 V and remarkable cycling stability, retaining 83 % of its initial performance after 4000 charge-discharge cycles.

Integrating self-hygroscopic hydrogel electrolyte and porous electrode for supercapacitor operating in variable humidity environments

The application of supercapacitors (SCs) based on the conventional polyvinyl alcohol‑potassium hydroxide (PVA-KOH) polymer electrolyte is challenged in variable humidity environments, especially in low relative humidity (RH) environments. Herein, taking advantage of the high ionic conductivity and strong hygroscopicity of highly concentrated KOH solutions, we have prepared a hygroscopic hydrogel polymer electrolyte composed of sodium alginate (SA)/PVA/poly(acrylic acid) (PAA)-KOH. The SA/PVA/PAA-KOH gel electrolyte exhibits high ionic conductivity, superior water retention and even water adsorption capability. A three-dimensional CoCu-layered double hydroxide/zeolitic imidazole framework-67 (CuCo-LDH/ZIF-67) porous electrode has also been prepared for the construction of the high-performance SC operating in variable RH environments. The CuCo-LDH/ZIF-67 porous electrode allows deep penetration of the self-hygroscopic electrolyte, facilitating electron/ion diffusion and providing fast water transport channels. As a result, our asymmetric SC show significantly improved electrochemical performance than that of SC based on conventional PVA-KOH electrolyte under different RH environments. This integration strategy can advance the practical application of SC in extreme environments.

High-performance electrochromic devices composed of niobium tungsten oxide films

Electrochromic technology plays a pivotal role in various industries, offering significant benefits in energy efficiency and sustainability. By efficiently modulating sunlight, it reduces dependence on traditional climate control systems, thus decreasing overall energy consumption. Among electrochromic materials, tungsten oxide (WO3) is highly favored for its outstanding stability and superior optical modulation amplitude. However, the escalating demands of commercial applications necessitate enhancements in electrochromic performance, achievable through doping or composite designs. This study investigates the electrochromic characteristics of novel niobium tungsten oxide (Nb18W16O93) thin films, employing a gel electrolyte and examining their structural, optical, and electrochemical attributes. Compared to pure WO3, the Nb18W16O93-based electrochromic device exhibited a significant optical modulation of 55.1% in the visible spectrum and 31.3% in the near-infrared region. The gel-based device not only provides safety benefits over liquid electrolytes by mitigating leakage risks but also features rapid switching response times, with a coloration duration of 3.9 s and a bleaching interval of 3.6 s. Moreover, the device showcases exceptional long-term stability, retaining a ΔT of nearly 72% after 10,000 cycles.

A Comprehensive Review of Functional Gel Polymer Electrolytes and Applications in Lithium-Ion Battery.

The rapid expansion of flexible and wearable electronics has necessitated a focus on ensuring their safety and operational reliability. Gel polymer electrolytes (GPEs) have become preferred alternatives to traditional liquid electrolytes, offering enhanced safety features and adaptability to the design requirements of flexible lithium-ion batteries. This review provides a comprehensive and critical overview of recent advancements in GPE technology, highlighting significant improvements in its physicochemical properties, which contribute to superior long-term cycling stability and high-rate capacity compared with traditional organic liquid electrolytes. Special attention is given to the development of smart GPEs endowed with advanced functionalities such as self-protection, thermotolerance, and self-healing properties, which further enhance battery safety and reliability. This review also critically examines the application of GPEs in high-energy cathode materials, including lithium nickel cobalt manganese (NCM), lithium nickel cobalt aluminum (NCA), and thermally stable lithium iron phosphate (LiFePO4). Despite the advancements, several challenges in GPE development remain unresolved, such as improving ionic conductivity at low temperatures and ensuring mechanical integrity and interfacial compatibility. This review concludes by outlining future research directions and the remaining technical hurdles, providing valuable insights to guide ongoing and future efforts in the field of GPEs for lithium-ion batteries, with a particular emphasis on applications in high-energy and thermally stable cathodes.

Binary solvent-reinforced poly (vinyl alcohol)/sodium alginate double network hydrogel as a highly ion-conducting, resilient, and self-healing gel polymer electrolyte for flexible supercapacitors

We present a reliable approach for producing high-performance ion-conducting gel polymer electrolytes (GPEs) based on the sodium chloride (NaCl)-integrated dual network hydrogel of poly (vinyl alcohol)/sodium alginate (PVA/SA) using a binary solvent system of ethylene glycol (EG) and water, providing exceptional ionic conductivity, mechanical strength, and self-healing properties. Different GPEs were produced via the freezing-thawing method using different v/v% of EG and water (named PVA/SA/EG). The best PVA/SA/EG GPE provided a maximum ionic conductivity of 25 mS cm−1, astonishing mechanical strength of 0.42 MPa, exceptional stretchability of 462 %, and remarkable self-healing properties. The binary solvent system- and water-based GPEs were utilized in the construction of symmetric supercapacitors (SSCs) using carbon cloth electrodes and their electrochemical performance were compared. At a current density of 0.5 mA cm−2, the SSC prepared using the best PVA/SA/EG GPE demonstrated a high specific capacity of 577.21 mF cm−2, maintained 94.5 % capacitance after 5000 cycles at 1 mA cm−2, and provided an energy density of 80.14 mWh cm−2 while operating at a power density of 293.3 mW cm−2. The flexible SSC prepared based on this GPE demonstrated outstanding flexibility, while no significant decline in capacitive performance and ionic conductivity was detected when it was bent.

Tissue-like interfacing of planar electrochemical organic neuromorphic devices

Abstract Electrochemical organic neuromorphic devices (ENODes) are rapidly developing as platforms for computing, automation, and biointerfacing. Resembling short- and long-term synaptic plasticity is a key characteristic in creating functional neuromorphic interfaces that showcase spiking activity and learning capabilities. This potentially enables ENODes to couple with biological systems, such as living neuronal cells and ultimately the brain. Before coupling ENODes with the brain, it is worth investigating the neuromorphic behavior of ENODes when they interface with electrolytes that have a consistency similar to brain tissue in mechanical properties, as this can affect the modulation of ion and neurotransmitter diffusion. Here, we present ENODEs based on different PEDOT:PSS formulations with various geometries interfacing with gel-electrolytes loaded with a neurotransmitter to mimic brain-chip interfacing. Short-term plasticity and neurotransmitter-mediated long-term plasticity have been characterized in contact with diverse gel electrolytes. We found that both the composition of the electrolyte and the PEDOT:PSS formulation used as gate and channel material play a crucial role in the diffusion and trapping of cations that ultimately modulate the conductance of the transistor channels. It was shown that paired pulse facilitation can be achieved in both devices, while long-term plasticity can be achieved with a tissue-like soft electrolyte, such as agarose gel electrolyte, on spin-coated ENODes. Our work on ENODe-gel coupling could pave the way for effective brain interfacing for computing and neuroelectronic applications.

Urea-lactic acid as efficient lignin solvent and its practical utility in sustainable electrospinning

The development of lignin-based materials presents a promising avenue for advancing green chemistry and mitigating environmental impact. However, the key challenge lies in the processability of lignin, which significantly affects its practical applications. Addressing the issues related to lignin's complex structure, variability, and reactivity is crucial for optimizing its incorporation into high-performance materials. Therefore, in this study we explore the efficacy of a urea-lactic acid-based deep eutectic solvent (ULA) for the dissolution of kraft lignin, aiming to enhance its practical utility in sustainable electrospinning processes, for the first time. Results of elemental analysis, IR and 2D NMR spectroscopy, provide crucial insights into the structural properties of the regenerated material post-DES treatment. The findings confirm a high lignin recovery rate, reaching up to 96.6 % for samples dissolved at 100°C. Additionally, 2D NMR analysis indicates that the process leads to partial esterification of lignin with lactate ions. The ability of the studied DES to effectively solubilize lignin underscores its potential as an efficient lignin solvent and facilitates the fabrication of lignin-based nanofibers via electrospinning. The incorporation of this DES in electrospinning processes promises significant advancements in the development of sustainable, lignin-derived materials and offers a green alternative for production of high-performance nanofibers. Preliminary results of electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements confirm that the EDLC with prepared hydrogel electrolyte demonstrates attractive electrochemical properties (specific capacitance, CSP = 95 F g–1; series resistance RS = 2.2 Ω; charge transfer resistance, RCT = 1.6 Ω), which are comparable with the reference cell based on a commercial glass fibre separator. Hence, the DES-assisted-electrospinned lignin membrane can be viewed as a potential gel electrolyte matrix for practical use in construction of sustainable energy storage devices.

Improving the Cyclic Stability of Electrochromic Mirrors Composed of Gel Electrolyte

Improving the Cyclic Stability of Electrochromic Mirrors Composed of Gel Electrolyte

Tailored Cellulose Gel Electrolytes with Dual Pores, Aligned Channels, and Dendrite Mitigation for Improved K/Zn Dual-Ion Battery

Tailored Cellulose Gel Electrolytes with Dual Pores, Aligned Channels, and Dendrite Mitigation for Improved K/Zn Dual-Ion Battery

Nickel sulfide nanoparticles decorated on carbon spheres derived from Verbena officinalis for high-performance asymmetric all-solid-state flexible supercapacitors

The crafting and development of electrode materials possessing extensive energy storage capacities, alongside their adherence to environmental and economic principles, along with their outstanding capacitive behaviors, stand as pivotal elements in propelling the technological progress of supercapacitors. In this study, we utilized discarded Verbena officinalis (VOCs) as a carbon substrate and successfully synthesized porous hollow carbon spheres through an in-situ hydrothermal method, subsequently depositing NiS nanoparticles to form a shell-like structured material. The optimized VOCs/NiS-3 composite material exhibited an exceptional specific capacitance of 202.8 mAh g−1 at a current density of 1.0 A g−1; it maintained 71 % of its capacitance even at a high current density of 10 A g−1 (144.2 mAh g−1). After enduring 10,000 charge-discharge iterations, the preservation of charge storage capacity was 81.7 %, highlighting the material's outstanding performance in terms of rapid charge-discharge rates and enduring stability. Furthermore, within a PVA/KOH gel electrolyte, we fabricated an asymmetric all-solid-state supercapacitor device that delivered an energy density of 32.58 Wh k g−1 at a power density of 800 W k g−1. The device sustained a capacitance loss rate of 9.9 % and a coulombic efficiency of 96.8 % after 5000 cycles. Even after 3000 repeated bending at 120°, the capacitance retention reached 88.3 %, indicating the device's exceptional specific capacitance, flexibility and longevity. This research offers a renewable and waste-resource recycling design strategy for synthesizing outstanding-performance, flexible, all-solid-state supercapacitor electrode materials with NiS deposited on discarded biomass carbon, unveiling considerable potential for enhancing energy storage efficiency.

Fabrication of functional laser-induced graphene using gelatin-2,6-diaminoanthraquinone coating for high-performance micro-supercapacitor

In this investigation, we develop a procedure in which gelatin and 2,6-diaminoanthraquinone (ANQ) are combined and then applied as a coating on laser-induced graphene (LIG). The resulting materials are subjected to laser irradiation, which facilitates the introduction of nitrogen doping and the integration of oxygenated functional groups onto the LIG surface. The gelatin polymer played a pivotal role in introducing oxygenated functional groups, while ANQ molecules contributed to both doping with nitrogen and the inclusion of additional oxygenated groups on the LIG surface. The electrode material's performance was enhanced by these functional groups. When evaluated in a three-electrode setup, the ANQ-LIG configuration exhibited a significantly high areal capacitance of 32.4 mF cm−2 at 0.2 mA cm−2, which is five times that of pristine LIG (6.3 mF cm−2) and three times that of gelatin-LIG (9.0 mF cm−2). When integrated into a micro-supercapacitor using a polyvinyl alcohol (PVA)-sulfuric acid (H2SO4) gel electrolyte, ANQ-LIG demonstrated superior areal capacitance (16.0 mF cm−2 at 0.1 mA cm−2) compared to gelatin-LIG (5.3 mF cm−2) at the same current. Additionally, ANQ-LIG displayed favorable capacitance retention (83.8 % after 10,000 cycles) and coulombic efficiency (98.1 % after 10,000 cycles).

Weakened functional group activity enables the uniform distribution of the gel electrolyte to achieve the high-performance of Li-ion batteries

Electrolyte gelation is considered to be one of the main routes to solve the safety problem of liquid electrolytes. However, the distribution of gel polymer electrolyte (GPE) on the surface of electrodes and the mechanism of their effect on the performance of battery are still unknown. Here, methyl methacrylate (MMA) containing methyl (-CH3) and methyl-2-cyanoacrylate (MCA) containing cyanide (-CN) are employed as representative monomers to explore the relationship between gel distribution and battery performance. Due to the stronger electron-withdrawing properties, PMCA gel has shorter chain length and greater shrinkage, showing many cracks on the electrode surface, while PMMA gel can evenly cover the surfaces of electrodes. As a result, the capacity retention rate of 1.4 Ah NCM811/Gr pouch cells with PMMA is 93.5% for 500 cycles at 25 °C and 91.5% for 600 cycles at 60 °C, which these of the cells with PMCA are 58.8% for 266 cycles at 25 °C and 69.1% for 327 cycles at 60 °C. XPS analysis of the electrode sheets before and after cycling reveal that the PMCA-electrode has a large number of rzero valent lithium element precipitation, whereas the PMMA-electrode has the more stable interface film. This study indicates that the uniform distribution of gel electrolyte with -CH3 functional group on the electrode surface can improve the electrochemical performance of NCM811/Gr battery, which has the guiding significance.

The role of polymer gel electrolyte infiltration for enhancement of capacitance and cycle stability

With the increasing application of electronic materials in various fields such as flexible electronic textiles, wearable and portable gadgets, aerospace and aircraft systems etc., the demand for clean high-power energy storage devices is also increasing rapidly. To date, the application of market available supercapacitors has not met the energy expectations in the range of market leading Li-ion batteries (LIBs) due to their unreliable mechanical flexibility, electrolyte leakage, low voltage application, low capacity, low cycle stability and moderate rate-capability. Inappropriate utilization of the maximum porosity of the electrode material and inefficient activities of the electrode/electrolyte interface are major challenges for present supercapacitor development. In this work, for the first time, the role of polymer gel electrolyte infiltration to improve the electrochemical performance of a supercapacitor has been explicitly studied and investigated. It has been observed that 1-Ethyl-3- Methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSI] ionic liquid electrolyte embedded in Polypropylene Carbonate (PPC) and Polycarbonate (PC) polymer matrix polymer gel electrolyte (PGE) showed excellent supercapacitive performance at high voltage window 2.6 V by delivering maximum total capacitance of 5.81 F and maximum energy density 10.9 Wh kg-1 at 30 mA current (0.06 A g-1). Regular infiltration of the polymer gel electrolyte inside the electrode material is also observed during long cycle operation of 10,000 cycles. Infiltration of electrolyte ions into the pores of electrode materials plays a significant role in increasing capacitance and cycle Stability. These results highlight the potential of this novel high-voltage polymer gel electrolyte for future high-power energy storage device applications.

Tough and self-healing all-in-one supercapacitor enabled by triple-network redox carrageenan and sodium carboxymethylcellulose reinforcing gel polymer electrolyte

Flexible supercapacitors have recently gained great attention in the field of wearable electronics due to their long cycle life, and high efficiency. Herein, an all-in-one flexible supercapacitor is fabricated by in-situ polymerization of PANI on the surface of a fully physical cross-linking polyacrylamide/κ-carrageenan-K+/sodium carboxymethylcellulose-Al3+ triple network gel polymer electrolyte (GPE). By designing multiple interpenetrating networks and bimetallic ions cross-linking, the GPE displays outstanding mechanical performance. Meanwhile, owing to the dynamic interactions (hydrogen bond, ion coordination and thermoreverisible transition of KC) among different polymer chains, the GPE exhibits remarkable self-healing properties. Additionally, the all-in-one configuration accelerates ion transport at electrode-electrolyte interface and provides extremely low interface resistance, which endows the supercapacitor with excellent capacitance performance (254.58 mF/cm2) and energy density (59.81 μWh/cm2). Thanks to the unique integrated structure, the device avoids the slippage among multilayers and shows splendid electrochemical stability even under various physical deformations. More importantly, the all-in-one supercapacitor displays superior safety, self-healing and low temperature properties (85 % capacitance retention after 8 cutting/healing cycles even at −20 °C) due to the multi-function GPE. This simple and versatile strategy for constructing the all-in-one supercapacitors will offer broad prospects for designing energy storage devices in wearable electronics.

CdS/CuInS2 Quantum Dots Cosensitized Solar Cells Using Functionalized Polyurethane Gel Electrolytes

CdS/CuInS2 Quantum Dots Cosensitized Solar Cells Using Functionalized Polyurethane Gel Electrolytes

MIL-125 (Ti) and porous dielectric polymer substrate introducing composite gel polymer electrolyte with enhanced mechanical property, thermal stability and electrochemical property

Lithium metal batteries have potentially high energy density, but severe uncontrolled lithium dendrites and unstable side reactions prevent large-scale applications. Serial three-dimensional porous poly (vinylidene fluoride) and copolymer membrane-based composite gel electrolytes are designed by introducing MIL-125 (Ti) and ethylene carbonate. Abundant lithium-ion transportation channels and homogeneous ion transport microregion are provided the new type porous fluoropolymer substrate. We also find that crystalline phase and dielectric properties of serial polymer membrane have significant impact on electrochemical performance for composite gel electrolytes. The mechanical and dielectric property of composite electrolyte enhanced by incorporating uniform and well distribution MIL-125 (Ti), which improve the electrolyte/electrode interface charge distribution and promote uniform lithium deposition, leading to lithium dendrite suppression. MIL-125 (Ti)/P(VDF-TrFE-CTFE) composite membrane shows the enhanced maximum strain of 181 %, thermal stability (188 °C) and corresponding composite gel electrolyte reflects higher ionic conductivity of 1.7 × 10–3 S cm-1 and wider electrochemical window at room temperature than PVDF and PVDF-HFP composite electrolytes. Expectedly, quasi-solid state lithium metal battery of MIL-125 (Ti)/P(VDF-TrFE-CTFE) composite gel electrolyte exhibits higher discharge capacity (152.8 mAh g-1) at 240th cycle and 1 C, longer cycling life and better rate performance under large current density than PVDF and PVDF-HFP composite electrolytes.

Simple construction of molybdate anions-intercalated NiCo-based layered double hydroxides nanosheet arrays on carbon fibers for enhanced flexible fiber-shaped supercapacitors

As the energy supply devices for miniaturized, wearable, portable and intellectualized electronic products, flexible fiber-shaped supercapacitors (FSCs) have attracted great attention by virtue of their peculiar superiorities such as ultra-fast charge/discharge ability, ultra-high output power, ideal service life, outstanding mechanical flexibility, and superior compatibility with the human body. The performance enhancement of FSCs is highly dependent on the high-performance active electrode materials. In this work, a series of molybdate anions-intercalated NiCo based layered double hydroxides (NiCoMo-LDHs) have been synthesized on flexible carbon fiber (CF) by a simple electrodeposition strategy by regulating the Mo content and the growth time. It turns out that the intercalation of molybdate anions can significantly widen the interlayer spacing and reduce the crystallinity of the synthesized LDH materials. The morphological differences between the LDHs with different Ni/Co/Mo ratios are analyzed, and the morphological evolution process of the materials with the specific Ni/Co/Mo ratio of 1:3:0.2 are systematically investigated. The well-developed NiCoMo-LDH nanosheets electrode with appropriate Ni/Co/Mo ratio (NCM2–500) delivers the best electrochemical performances among all the synthesized LDHs. In particular, the synthesized NCM2–500 fiber electrode exhibits excellent specific capacitance, superior electrical conductivity and favourable cycling stability. Additionally, the assembled parallel type NCM2–500//AC FSC device using NCM2–500 and activated carbon (AC) as the cathode and anode with the assistance of PVA/KOH gel electrolyte demonstrates a brilliant specific energy of 36 Wh cm−1 at 845 W cm−1 (nearly 17 Wh kg−1 at about 400 W kg−1) and a high cycle lifespan of maintaining 103 % of the pristine capacity after 5000 cycles. This FSC device is an ideal candidate for next-generation applications due to its remarkable electrochemical properties.