Flexible Asymmetric Supercapacitor Device Research Articles

Composite of CoS1.97 nanoparticles decorated CuS hollow cubes with rGO as thin film electrode for high-performance all solid flexible supercapacitors

Stretchable flexible thin-film electrodes are extensively explored for developing new wearable energy storage devices. However, traditional carbon-based materials used in such independent electrodes have limited practical applications owing to their low energy storage capacity and energy density. To address this, a unique structure and remarkable mechanical stability thin-film flexible positive electrode comprising CoS1.97 nanoparticles decorated hollow CuS cubes and reduced graphene oxide (rGO), hereinafter referred to as CCSrGO, is prepared. Transition metal sulfide CoS1.97 and CuS shows high energy density owing to the synergistic effects of its active components. The electrode can simultaneously meet the high-energy density and safety requirements of new wearable energy storage devices. The electrode has excellent electrochemical performance (1380 F/g at 1 A/g) and ideal capacitance retention (93.8 % after 10,000 cycles) owing to its unique three-dimensional hollow structure and polymetallic synergies between copper and cobalt elements, which are attributed to their different energy storage mechanisms. Furthermore, a flexible asymmetric supercapacitor (FASC) was constructed using CCSrGO as the positive electrode and rGO as the negative electrode (CCSrGO//rGO), which delivers an energy density of 100 Wh kg−1 and a corresponding power density of 2663 W kg−1 within a voltage window of 0–1.5 V. The resulting FASC can power a light-emitting diode (LED) at different bending and twisting angles, exerting little effect on the capacitance. Therefore, the prepared CCSrGO//rGO FASC devices show great application prospects in energy storage.

Flexible electrodes composed of flower-like MoS2 and MXene for supercapacitor applications

Flexible supercapacitors with high charge storage ability are needed for emerging applications in wearable electronics. Here, we introduce a novel flexible supercapacitor electrode by incorporating flower-like MoS2 into MXene via a hydrothermal technique. We mostly focused on the structural design for electrode configuration to enhance the charge storage mechanism. Three different electrodes composed of MoS2, MXene, and MoS2@MXene were fabricated via a versatile drop-casting and drying method. There are unique advantages of incorporating MoS2 with MXene such as the fast electron transfer, hydrophilicity of the interface, and structural stability. The MoS2@MXene // MXene flexible asymmetric supercapacitor device offered a high energy density of 1.21 W h /kg and a power density of 54.45 W /kg. Moreover, the asymmetric device exhibits nearly identical electrochemical behavior following 100 bending cycles at different angles. The high electrochemical activity of MoS2 and MXene and good interaction are ascribed to the superior electrochemical performance of the composite material. Furthermore, this research could guide the development of flexible, high-performance, and low-cost electrodes which will be useful in wearable electronics.

In situ growth of a redox-active metal-organic framework on electrospun carbon nanofibers as a free-standing electrode for flexible energy storage devices.

The rational construction of free-standing and flexible electrodes for application in electrochemical energy storage devices and next-generation supercapacitors is an emerging research focus. Herein, we prepared a redox-active ferrocene dicarboxylic acid (Fc)-based nickel metal-organic framework (MOF) on electrospun carbon nanofibers (NiFc-MOF@CNFs) via an in situ approach. This in situ approach avoided the aggregation of the MOF. The NiFc-MOF@CNF flexible electrode showed a high redox-active behavior owing to the presence of ferrocene and flexible carbon nanofibers, which led to unique properties, including high flexibility and lightweight. Furthermore, the prepared electrode was utilized in a supercapacitors (SC) without the use of any binder, which achieved a specific capacity of 460 C g-1 at 1 A g-1 with an excellent cyclic retention of 82.2% after 25 000 cycles and a good rate capability. A flexible asymmetric supercapacitor device was assembled, which delivered a high energy density of 56.25 W h kg-1 and a long-lasting cycling performance. Also, the prepared electrode could be used as a freestanding electrode in flexible devices at different bending angles. The obtained cyclic voltammetry curves showed negligible changes, indicating the high stability and good flexibility of the electrode. Thus, the use of the in situ strategy can lead to the uniform growth of redox-active MOFs or other porous materials on CNFs.

Cerium-assembled tungsten oxide composite fibers: Adhesive-free electrodes for high performance asymmetric supercapacitors

In this study, in-situ cerium-assembled tungsten oxide carbon nanofibers were successfully prepared via simple electrospinning and calcination technology and were used as flexible electrodes without conductive agent and adhesive. It was confirmed that the introduction of Ce has better maintained the continuous morphology of one-dimensional fibers to provide a continuous uninterrupted reaction position by the SEM TEM and XPS results. The addition of cerium improved the wettability of the material, which was propitious to the penetration of the electrolyte, made the electrolyte more fully contact with the active site, and enhanced the interface transmission effectiveness by the liquid contact angle test. Otherwise, the XRD and XPS results exhibited that the addition of cerium has caused the lattice expansion of the tungsten oxide, which generated the self-adjustable strain relaxation ability of electrode material in the process of continuous constant voltage charge and discharge. It proved that the introduction of cerium has promoted electron transfer, which improved the electrochemical performance of electrode material. In this paper, compared with WO3-CNFs without Ce, the Ce/WO3-CNFs have wide lattice spacing and hydrophilicity, fully contact with the electrolyte in the electrochemical reaction, and provide high electron transfer ability. The Ce/WO3-CNFs shows the maximum specific capacitance (407 F g−1) and excellent cycling stability (10,000 cycles at 5 A g−1 with a retention rate of 80 %). Otherwise, the flexible asymmetric supercapacitor device was prepared using the Ce/WO3-CNFs as cathode, and the CNFs as the anode, which exhibited the maximum energy density was 35.75 Wh kg−1 and a power density was 362.54 W kg−1 at 0.5A g−1. The results show that rare earth doping is an effective way and that the Ce/WO3-CNFs are promising electrode materials for supercapacitors.

Wire-shaped, all-solid-state, high-performance flexible asymmetric supercapacitors based on (Mn,Fe) oxides/reduced graphene oxide/oxidized carbon nanotube fiber hybrid electrodes

Wire-shaped flexible supercapacitors (FSCs) have attracted tremendous attention due to their tiny volume, lightweight, high flexibility, and wearability. In the present study, we report the MnO2- or Fe2O3-loaded three-dimensional (3D) nanostructure networks of reduced graphene oxide (rGO) composite on oxidized CNT (denoted as the OCNTF/3D-rGO/MnO2 and OCNTF/3D-rGO/Fe2O3) fibers as the cathode and anode, respectively, for the fabrication of a high-performance, wire-shaped, all-solid-state, flexible asymmetric supercapacitor (FASC). To this end, the 3D-rGO/OCNTF hierarchical structure was electrochemically fabricated, followed by further pulse electrodeposition of MnO2 and Fe2O3, respectively, into the 3D porous graphene networks and the insides of the OCNTF. As such, they were restricted to nano-sized particles and linked by the graphene and the OCNTF. The OCNTF/3D-rGO/MnO2 as the cathode was assembled with the OCNTF/3D-rGO/Fe2O3 as the anode with the carboxymethyl cellulose sodium (CMC)-Na2SO4 gel electrolyte, producing a wire-shaped, all-solid-state FASC that achieved a high specific capacitance of 59.2 F·cm−3 (171 mF·cm−2) and an exceptional energy density of 26.7 mWh·cm−3. The FASC device also showed good flexibility and cyclability, promising to advance power sources for wearable electronics.

Aerosol derived carbon dots decorated boron nitride supported Zn-doped MoS2 for high performing flexible asymmetric supercapacitor

Alternative finding of toxic pollutant materials in proper utilization is a great challenge. Toxic and pollutant cigarette smoke having different π-conjugated organic components may work well as a precursor for carbon dots (CDs). In this work, cigarette smoke aerosol has been used for the synthesis of CDs and CDs have been further used for the fabrication of supercapacitor electrode. This methodology could be able to mitigate the two major problems-energy crisis and environment pollution. The smart combination of EDLC-type CDs deposited boron nitride (BN) and pseudocapacitive type Zn-doped MoS2 was able to enhance the supercapacitive performances. Heteroatom doping into MoS2 enhances the capacitive performances through the effective Faradic reactions. CDs and CDs deposited BN (CDs@BN) have been characterized using different characterization techniques. Zn-doped MoS2 has been uniformly grown on the CDs decorated BN (Zn–MoS2/CDs@BN) resulting in the stabilization of the electrode system. Zn–MoS2/CDs@BN nanohybrid delivered a specific capacitance (Sp.C) of 397 F/g in three-electrode system. Further, the asymmetric supercapacitor (ASC) device using Zn–MoS2/CDs@BN as cathode demonstrated wide potential range (up to 1.8 V) with a volumetric energy density of 3.42 mW h/cm3 and retaining a capacitance of ∼89% after 10,000 charging-discharging processes. Moreover, a flexible ASC device was made-up using viscous ionic electrolyte and it was able to glow a red LED, while it was bended in different angles. The methods described here will give a straightforward approach for using toxic-pollutant cigarette smoke to fabricate supercapacitor electrodes in order to compensate the upcoming energy crisis in a sustainable way.

Copper oxide stabilized oxy-functionalized boron nitride‑carbon nanotube nanohybrid: An ultra-stable electrode for flexible asymmetric supercapacitor device in ionic electrolyte

This work explores the smart combination of functionalized boron nitride (mK-BN) and carbon nanotube (CNT), stabilized with copper oxide (CuO), as a highly stable, flexible supercapacitor electrode in low-cost viable ionic electrolyte. Oxy-surface modified boron nitride (BN) was introduced to induce supplementary acceptor and donor energy levels for charge transport. Incorporation of CNT facilitated the charge storage through EDLC mechanism and also reduced internal resistance. In three-electrode analysis, CuO/mK-BN/CNT nanohybrid exhibited specific capacitance (Csp) of 425 F/g in aqueous KCl. An asymmetric supercapacitor (ASC) device using CuO/mK-BN/CNT as cathode achieved a Csp of 80 F/g and 36 Wh/kg energy density with ⁓88 % stability after 25,000 charging-discharging cycles in organic electrolyte. To further boost the capacitive performance, energy density, and rate capability of the ASC device, a low-cost, solvent free, and viable ionic electrolyte [(NEt3H)+(HSO4)−] was introduced. In ionic electrolyte, device showed a maximum Csp of 132 F/g with an enhanced energy density of 59.4 W h/kg. ASC devices in ionic electrolyte also exhibited superior volumetric energy density of 1.410 mW h/cm3 and excellent electrochemical performances after connecting two cells in parallel or in series combination implying the capability of the device to produce different required capacitance and potential for practical application. Finally, a flexible ASC device with the ionic electrolyte was also tested. This work established that with the smart combination of additional energy level induced functionalized BN, conducting nanotubes, and pseudocapacitive CuO, a highly stable, flexible asymmetric supercapacitor device can be fabricated with high energy density.

Enhanced electrochemical performance of flexible asymmetric supercapacitor based on novel nanostructured activated fullerene anchored zinc cobaltite

The rational design and development of nanostructured materials having unique structural and superior electrochemical activity is urgently required for achieving ultra-high energy storage performance. In this regard, activated fullerene decorated over zinc cobaltite (A-C60-ZCO) has been synthesized and its performance evaluation was displayed towards supercapacitor application. As synthesized nanocomposite shows the enhanced specific capacitance of 593.2 F/g at a scan rate of 1 mV/S and retained the capacitance of 83.7% till 5000 cycles at a high current density of 8 A/g. The enhanced performance can be attributed to the hybrid nature of the prepared material, where A-C60 enhances the stability and conductivity and the ZCO enhances the charge storage owing to its pseudo capacitive nature. The incorporation of A-C60 immensely improved the specific capacitance and cyclic stability of the nanocomposite by enhancing hydrophilicity, conductivity, ion/electron transport ability, redox active functional groups and electroactive sites. Furthermore, the constructed flexible asymmetric supercapacitor device provided an energy density of 36.43 Wh/kg at a power density of 1681.47 W/kg, with a superior cycling performance of 91.06% capacitance retention after 5000 cycles at 6 A/g. Owing to the impressive electrochemical performance A-C60-ZCO can be considered as the potential candidate for supercapacitor application.

Formation of carbon coated yolk-shelled Fe3O4-CeO2 hollow spheres toward remarkable performance supercapacitors

Yolk-shelled hollow structures with unique structural features are incredibly attractive for energy storage systems. Here we present a self-template strategy to prepare carbon coated yolk-shelled Fe3O4-CeO2 hollow spheres. First, yolk-shelled Fe-Ce glycerate precursors are designed by a solvothermal method. Afterward, the carbon coated yolk-shelled Fe3O4-CeO2 hollow spheres are eventually synthesized via calcinations the obtained precursors in Ar. Such unique structures endow the Fe3O4-CeO2 with abundant inner cavities, large surface area and more electroactive site. As electrode material for supercapacitors, a large capacity of 430 C g−1 is obtained at 2.0 A g−1, and it can be as high as 198.4 C g−1 even at 20 A g−1. Moreover, it also takes outstanding rate capability and superior cycling durability (only 5.2 % capacity reduction over 5000 cycles at 6.0 A g−1). Furthermore, a quasi-solid-state flexible asymmetric supercapacitor device is constructed by Fe3O4-CeO2 cathode and activated carbon anode. The device manifests a high energy density of 46.6 Wh kg−1 at 2.0 A g−1 (versus 1650 W kg−1 power density). Even at 15 A g−1, the energy density is still 21 Wh kg−1 with 12,441 W kg−1. We envision that this work not only explores a promising electrode material for supercapacitors, but also provides an alternative avenue to prepare yolk-shelled hollow structures toward energy storage applications.

Strongly coupled carbon quantum dots/NiCo-LDHs nanosheets on carbon cloth as electrode for high performance flexible supercapacitors

NiCo-LDHs is one of the most promising electrode materials for supercapacitors. However, the intrinsic low conductivity and the volume expansion/contraction still seriously limit the application of NiCo-LDHs in supercapacitors. Herein, we constructed carbon quantum dots (CQDs)/NiCo-LDHs nanosheets heterostructures on carbon cloth (CQDs/NiCo-LDHs@CC) through a simple solvothermal method using CQDs-embedded Co-MOF as precursor. The in-situ implanting of CQDs not only can effectively improve the conductivity of the NiCo-LDHs but also boost the long-term structural stability of the flexible electrode through the morphological optimization of NiCo-LDHs. Benefit from the ingenious structural design and strong coupling between CQDs and NiCo-LDHs, the CQDs/NiCo-LDHs@CC electrode delivered a much-enhanced capacitance performance in 6 M KOH, including a large reversible specific capacitance of 2023 F g−1 (5.22 F cm−2) at 5 mA cm−2, superior rate capability with 84.3% capacitance retention at 30 mA cm−2 and excellent cycle life. The flexible asymmetric supercapacitor device exhibited an energy density of 117.8 Wh kg−1 with a power density of 528.3 W kg−1 at 2 mA cm−2 using CQDs/NiCo-LDHs@CC as positive electrode and activated CC as negative electrode. This work provides a new opportunity for the development of nanocomposites with the in-situ implanting of CQDs to construct high-performance electrodes for flexible supercapacitors.

CoFe2O4 Nanoparticle Decorated Hierarchical Biomass Derived Porous Carbon Based Nanocomposites for High-Performance All-Solid-State Flexible Asymmetric Supercapacitor Devices

CoFe₂O₄ Nanoparticle Decorated Hierarchical Biomass Derived Porous Carbon Based Nanocomposites for High-Performance All-Solid-State Flexible Asymmetric Supercapacitor Devices

Facile stepwise hydrothermal synthesis of hierarchical CoMoO4/CoMoO4 core/shell dandelion-like nanoarrays: A promising binder-free positive electrode for high-performance asymmetric supercapacitors

In this study, we have fabricated a flexible supercapacitor with outstanding pseudocapacitive performance using hierarchical CoMoO4/CoMoO4 core/shell dandelion-like nanoarrays. The dandelion-like CoMoO4/CoMoO4 nanostructure electrode yields a high specific capacitance (1548 F g−1 at a current density of 1 A g−1) and superior cycling stability performance (94% capability retention after 5000 cycles at 8 A g−1) in the 3 mol L–1 KOH solution. Furthermore, a flexible asymmetric supercapacitor device was assembled based on nickel foam/CoMoO4/CoMoO4 dandelion-like as positive electrode and activated carbon (AC) as negative electrode. The CoMoO4/CoMoO4 nanostructure//AC asymmetric supercapacitor device represents remarkable electrochemical performance such as good specific capacitance of 152 F g−1 and maximum energy and power densities of 54.04 Wh kg−1 and 8.83 kW kg−1, respectively. These encouraging results depict great potential in developing energy storage devices by making heterostructure nanomaterials.

A high-performance flexible energy storage device from biomass-derived porous carbon supported MnCo2O4 nanorods and MnO2 nanoscales

MCO-MnO2-PC||PC as a high-performance flexible asymmetric supercapacitor device.

All pseudocapacitive MXene-MnO2 flexible asymmetric supercapacitor

As a newly emerging 2D materials, MXene as electrode materials can be widely used in supercapacitors. However, symmetric supercapacitors based on MXene have a narrow voltage window due to oxidation occurs at a high anode potential. In this study, flexible asymmetric supercapacitor device is designed and fabricated by combining MXene/carbon fabric (CF) as the negative electrode and CF/MnO2 as the positive electrode in neutral electrolyte. The voltage window of the asymmetric device is successfully increased to 1.5 V, which is more than twice wider than that of the symmetric device. The maximum specific capacitance is 20.5 F g−1 at 1.5 A g−1. The specific capacitance remains at 84% after 3000 charge-discharge cycles at 1.5 A g−1. Furthermore, two asymmetric devices after bending 1000 times greater than 90° connected in series can easily power a 3 V LED for 90 min. The energy density of the asymmetric device is 6.4 W h kg−1 at 1107.7 W kg−1 power density. The work presented here shows that the asymmetric device based on MXene//MnO2 have excellent application prospects for the next generation of electrochemical energy storage devices.

Correction to “High-Performance All-Solid-State Flexible Asymmetric Supercapacitor Device Based on a Ag–Ni Nanoparticle-Decorated Reduced Graphene Oxide Nanocomposite as an Advanced Cathode Material”

Correction to “High-Performance All-Solid-State Flexible Asymmetric Supercapacitor Device Based on a Ag–Ni Nanoparticle-Decorated Reduced Graphene Oxide Nanocomposite as an Advanced Cathode Material”

Wire spherical-shaped Co-MOF electrode materials for high-performance all-solid-state flexible asymmetric supercapacitor device

The exploration of an inexpensive, low-energy consumption and environmentally friendly preparation process to synthesize high capacitance performance MOF-based electrode materials is an important prerequisite for their commercialization. We propose a non-calcined strategy to synthesize nanowire microsphere shaped Co-BTC (CBNWM). Making MOF into one-dimensional nanowire structure can effectively increase its active sites and the ion transfer rate. After the MOF nanowires are entangle and reunite into microspheres, their mechanical property and chemical stability are improved. Therefore, compared with Co-BTC crystal (CBC), the electrochemical properties of CBNWM have been significantly improved. The specific capacity of CBNWM reaches 1020 F g−1 at 5 mV s−1 or 657 F g−1 at 0.5 A g−1 with the capacity remains 81.4% after 3000 cycles. Subsequently, a flexible asymmetric device of CBNWM//AC was fabricated, whose maximum energy density can achieve 34.4 W h kg−1 with the related power density of 375.3 W kg−1.

Single step fabrication of nanostructured Cr2O3-MoO2 composite flexible electrode for top-notch asymmetric supercapacitor

Herein, a high performing flexible asymmetric supercapacitor (FASC) has been constructed by using Cr2O3-MoO2 composite film as positive electrode and carbon film as negative electrode. These thin film electrodes were synthesized by using DC magnetron sputtering technique on the flexible stainless steel (SS 304) current collector. Further, electrochemical kinetics of the prepared thin film electrodes were examined in 1 M Na2SO4 aqueous electrolyte solution. The Cr2O3-MoO2 composite thin film electrode offered high specific capacitance of 340.8 Fg−1 at the current density of 2 mAcm−2. Cr2O3-MoO2 composite electrode surplus Cr2O3 electrode in aspect of their electrochemical properties and cyclability. The structural integrity of both electrodes for (Cr2O3-MoO2//C) FASC device construction facilitated excellent electrochemical performance, operated at prolonged working voltage of +1.9 V and accomplished specific capacitance of 74.5 Fg−1 at 2 mAcm−2. FASC device delivered competitive specific energy of (37.35 Whkg−1) at specific power of (9708 Wkg−1) with excellent capacitance retention of (91.7%) even after 20,000 discharging cycles. Moreover, FASC displayed high capacitance retention (86.1%) in 80° bend state for the same number of charging cycles. These tremendous electrochemical properties and excellent cyclic stability of design FASC device, suggests it to be a promising candidate for energy storage and flexible electronic devices.

High-Performance All-Solid-State Flexible Asymmetric Supercapacitor Device Based on a Ag–Ni Nanoparticle-Decorated Reduced Graphene Oxide Nanocomposite as an Advanced Cathode Material

The development of wearable electronic devices and energy storage devices that are thin, lightweight, and flexible has led to the fabrication of flexible all-solid-state supercapacitors with skyscraping mechanical endurance and foldability. Herein, for the first time, we have delineated the assembly of a high-performance mechanically flexible all-solid-state asymmetric supercapacitor device from the nanocomposite comprising (Ag0.50Ni0.50)90-rGO10 and pure rGO as the cathode and anode electrode, respectively. Polyvinyl alcohol (PVA) gel containing 3 M KOH is used as the electrolyte and separator. This device delivers a high power density of 1700 W kg–1 without compromising with an energy density value of 49 W h kg–1 which is much higher in comparison to many of the existing supercapacitors in the market and substantive findings in the literature. Also, when the fabricated device is subjected to 5000 galvanostatic charge–discharge (GCD) cycles, a retention of ∼97% of the initial specific capacitance value is observed, displaying its high cycling stability. The omnidirectional mechanical robustness of this supercapacitor makes it flexible to that extent that it tends to exhibit high electrochemical performance even under extreme conditions and the specific capacitance value is pragmatically left unmodified when the device was subjected to different bending conditions. This device showcased its practical application by illuminating seven light-emitting diodes (LEDs) and appeared as an attractive energy storage unit for handy devices.

Facile co-deposition of the carbon nanotube@MnO2 heterostructure for high-performance flexible supercapacitors

Herein, a facile co-deposition method is developed to synthesize carbon nanotube (CNT)@MnO2 heterostructures grown on carbon fibre paper (CFP) and flexible carbon fibre cloth (CFC) (denoted as CNT@MnO2/CFP and CNT@MnO2/CFC, respectively). A three-dimensional (3D) interconnected CNT network of highly conductive, ultrathin CNT@MnO2 heterostructure nanosheets with a nanoporous structure and with epitaxial growth of MnO2 on the CNTs achieves excellent capacitance performance for flexible MnO2-based supercapacitor materials. The CNT@MnO2/CFP fabricated in an electrolyte with CNT content of 0.5 g L−1 (0.5-CNT@MnO2/CFP) obtains mass, area and volume specific capacitance values of 393.0 F g−1, 585.0 mF cm−2 and 29.3 F cm−3, respectively, at a charge-discharge rate of 0.25 A g−1. A flexible asymmetric supercapacitor device was successfully assembled which possesses a high energy density of 27.8 Wh kg−1 at a high power density of 250 W kg−1 (0.75 mA cm−2) and a high capacitance retention of 84% after 10,000 performs at a charge-discharge rate of 15 mA cm−2 (5 A g−1). Our work confirmed that this structure can effectively improving the utilization and specific capacitance of MnO2, and the simplicity of the fabrication and the environmentally friendly characteristics of the deposition liquid make this approach suitable for practical production.

Superfast ice crystal-assisted synthesis of NiFe2O4 and ZnFe2O4 nanostructures for flexible high-energy density asymmetric supercapacitors

An ultrafast (∼20 min), inexpensive and scalable ice crystal-assisted precipitation approach was developed to synthesize unique self-assemblies of nickel ferrite nanoparticles (NiFe2O4 NPs) and zinc ferrite nanorods (ZnFe2O4 NRs) that contain plenty of porous voids for supercapacitor applications. The void-rich NiFe2O4 NPs and ZnFe2O4 NRs provide the required electroactive sites, multiple redox couples, and fast ion transportation pathways for electrolyte ions. Due to the formation of these self-assembled porous networks of nanostructures and their high specific surface area, NiFe2O4 NP- and ZnFe2O4 NR-based electrodes demonstrate excellent charge storage properties. Particularly, the individual NiFe2O4 NP and ZnFe2O4 NR electrodes manifest high specific capacities of 1403 and 1005 C g−1 at a current density of 1 A g−1, respectively, and excellent durability with a high capacity retention (>97%) for up to 15,000 cycles. A flexible NiFe2O4 NP//ZnFe2O4 NR-based asymmetric supercapacitor (ASC) device was fabricated using NiFe2O4 NPs as the positive electrode, ZnFe2O4 NRs as the negative electrode, and a PVA-KOH electrolyte. Importantly, the flexible NiFe2O4 NP//ZnFe2O4 NR device exhibits a superhigh energy density of 99.55 Wh kg−1 at a power density of 1.28 kW kg−1. During the long-term stability tests, this flexible ASC device shows a capacity retention of 95% after 15,000 GCD cycles. Thus, the present work offers an alternative low-cost and rapid ice crystal-assisted precipitation approach for the development of self-assembled porous networks with void-rich structures to enhance the overall performance of energy storage devices.