Flexible Solid-state Asymmetric Supercapacitor Research Articles

A flexible solid-state asymmetric supercapacitor device comprising cobalt hydroxide and biomass-derived porous carbon.

Development in the field of alternative and renewable energy sources is becoming necessary considering the current energy demands of the growing technologies. The main challenge associated with the produced energy is to store it for future use, such that it can be used when needed. Supercapacitors are among the electrochemical energy storage systems that provides higher power density, faster charging-discharging, high specific capacitance (C S), and long cycling life. Herein, the fabrication of a flexible solid-state asymmetric supercapacitor (ASC) device is reported, where Co(OH)2 hollow spheres and biomass-derived porous carbon (PC) are the cathode and anode, respectively. Co(OH)2 is a highly redox active material, whereas PC is an electric double-layer capacitive (EDLC) material. In this device, aqueous KOH solution (electrolyte) encapsulated in PVA gel (separator) was used to bind the electrodes. This Co(OH)2//PC ASC device exhibited a high C S of 260 F g-1 (at 2 A g-1). It retained ∼91% of the initial C S value (at 6 A g-1) till ∼5000 cycles. Electrochemical impedance spectroscopy (EIS) study confirmed low internal resistance (0.95 Ω) and charge transfer resistance (1.41 Ω) values of Co(OH)2//PC. These results indicate that the high electron transfer process in the electrode-electrolyte interface during the electrochemical reaction, which is responsible for the excellent performance of this ASC device. The high-performance Co(OH)2//PC ASC device exhibited an energy density of 76.7 W h kg-1 at a power density of 1416.9 W kg-1. To demonstrate its practical use, LED lights were illuminated using this Co(OH)2//PC ASC device.

The construction of a flexible solid-state asymmetric supercapacitor device using nickel-copper oxide nanoplates and carbon nanosphere serving as positive and negative electrode, respectively with excellent electrochemical capabilities

Here, nickel-copper oxide nanoplates (NCN) and carbon nanosphere (CNS) as positive and negative electrodes are synthesised via a hydrothermal protocol without adding any surfactant and binders. The NCN and CNS electrodes in KOH electrolyte exhibit superior specific capacitance of ∼ 2362.5 F g−1 and ∼ 246.11 F g−1 at 1 A g−1 respectively. The NCN and CNS retained 98.54 % and 97.88 % of the initial capacitance after 3000 galvanostatic charge–discharge (GCD) cycles, respectively. Additionally, an asymmetric supercapacitor (ASC) device NCN//CNS is constructed using NCN and CNS as positive and negative electrodes, utilizing poly(vinyl alcohol) PVA − KOH gel electrolyte separator. The ASC device demonstrates a maximum energy density of 50.4 Wh kg−1 (181.44 KJ kg−1) with a power density ∼ 750 W kg−1 at 1 A g−1, maintaining 90.4 % cyclic stability after 10,000 GCD cycles. The electrochemical outputs of the device present significant potential for the advancement of high-performance ASC devices in electronic applications.

PH-Regulated host-guest architecture in molybdenum Dioxide/Carbon sphere composites for flexible solid-state supercapacitors

Compositing molybdenum dioxide (MoO2) with carbon sphere (CS) can greatly enhance the conductivity and structural instability to achieve its high theoretical capacitances. The controllable regulation of local architecture and host–guest interaction in the two-phase composites is highly desirable, but commonly hindered by the significant difference in formation mechanism between MoO2 and CS. Herein, a pH-regulated pre-intervention strategy was developed to provide control over the MoO2/CS architecture by adjusting the interplay between the precipitation kinetics of MoO2 and the polymerization effect of hydrochar precursor. By varying the pre-synthesis pH from 10.0 to 0.1, the corresponding dominant formation process of precursor changes from inside-out Ostwald ripening to protonation-induced electrostatic interactions, resulting in the structural evolution of MoO2/CS from hollow CS-encapsulating MoO2 nanosheets and solid CS-supporting MoO2 nanoparticles. The electrochemical test proved the former architecture possesses faster electrode kinetics, lower charge/ion-transfer resistance, and better electrochemical stability. An extended oxidation-etching method was further introduced to prepare mesoporous CS with excellent supercapacitive properties. A flexible solid-state asymmetric supercapacitor composed of optimal MoO2/CS structure as the positive electrode and mesoporous CS as the negative electrode delivers a high energy density of 52.3 W h kg−1 and power density of 14500 W kg−1, and good cycling stability with 89.7 % retention of the initial capacitance after 8000 cycles.

Flexible solid-state asymmetric supercapacitor based on reduced graphene oxide (rGO)/ruthenium oxide (RuO2) composite electrode

Energy storage in flexible supercapacitor devices extensively depends on electrode design with good electrochemical as well as mechanical properties. Here, a cost-effective and scalable method is proposed for the synthesis of a reduced graphene oxide/ruthenium oxide (rGO/RuO2) composite thin film for flexible supercapacitor. The successive ionic layer adsorption and reaction (SILAR) method used to synthesize rGO/RuO2 composite electrode allowed the synthesis of amorphous RuO2 with optimized rGO composition. The morphological structure of rGO/RuO2 composite examined using a scanning electron microscope showed compact spherical microparticles coated on rGO sheets. The electrochemical measurements of rGO/RuO2 composite electrode revealed that the composite material achieved a specific capacitance of 1371 F g−1 at a scan rate of 5 mV s−1. Due to the combined impact of rGO and RuO2, a flexible solid-state asymmetric supercapacitor (FSS-ASC) of configuration rGO/RuO2/PVA-H2SO4/WO3 exhibited Cs of 114 F g−1 at 5 mV s−1 with 88% of capacitance retention after 5000 galvanostatic charge-discharge (GCD) cycles. The FSS-ASC provided a remarkable specific energy of 23 Wh kg−1 and a specific power of 613 W kg−1. The electrochemical features of rGO/RuO2 composite show a promising way to fabricate flexible supercapacitors.

High-performance flexible solid-state asymmetric supercapacitor with NiCo2S4 as a cathode and a MXene-reduced graphene oxide sponge as an anode

Ti3C2 MXenes have revealed immense potential in energy storage systems.

Hierarchical NiCo-LDH@MoS2/CuS composite as efficient trifunctional electrocatalyst for overall water splitting and asymmetric supercapacitor

The development of highly active and long-lived multifunctional electrocatalysts is a key priority to boost clean renewable energy technologies. It is difficult to construct such hierarchically structured materials with an efficient synergistic heterostructure technique to improve electrochemical performance. Here, a novel hierarchical NiCo-LDH@MoS2/CuS heterostructure (HS) was prepared by facile two-step hydrothermal synthesis for water splitting and supercapacitor applications. The hierarchical network of NiCo-LDH is grown on MoS2/CuS and is put forward based on various physio-chemical analysis. The hierarchical structure and heterostructure synergistic effect result in excellent HER (114 mV@10 mA cm−2) and OER (310 mV@10 mA cm−2) activity. Two electrode water-splitting cells (NiCo-LDH@MoS2/CuS||NiCo-LDH@MoS2/CuS) achieved a cell potential of 1.57 V@10 mA cm−2. NiCo-LDH@MoS2/CuS also exhibits the electrochemical charge storage property of 147.16 mAh g−1@0.2 A g−1. NiCo@MoS2/CuS||AC flexible solid-state asymmetric supercapacitor (FSSC) demonstrated charge storage of 226.08 mAh g−1 and energy density of 152.60 W h kg−1@0.2 A g−1 with 90.05 % retention rate, demonstrated the excellent cyclic and structural stability. The acquired knowledge from this study could be a novel strategy for designing hierarchical LDH-based heterostructures as electrode materials for water splitting and energy storage devices.

Synthesis of reduced graphene oxide (rGO)/dysprosium selenide (Dy2Se3) composite electrode for energy storage; flexible asymmetric supercapacitor

In recent years, the requirement for flexible electrode materials has attracted scientific attention for developing flexible supercapacitors. The present work reports the porous reduced graphene oxide/dysprosium selenide (rGO/Dy2Se3) composite thin films preparation, employing successive ionic layer adsorption and reaction (SILAR) method. This work offers thorough information about the structure, morphology, and elemental analysis of prepared rGO/Dy2Se3 composite, as well as its electrochemical properties such as specific capacitance (Cs), charge transfer resistance, electrochemical stability, etc. The rGO/Dy2Se3 composite electrode achieved a Cs of 289 F g−1 at a 5 mV s−1 scan rate with 89% retention up to 5000 galvanostatic charge-discharge (GCD) cycles due to synergy between properties of Dy2Se3 and rGO. A flexible solid-state asymmetric supercapacitor (FSSAS) rGO-Dy2Se3/LiClO4-PVA/MnO2) device delivered Cs of 107 F g−1 at a 5 mV s−1 and a specific energy of 45 Wh kg−1 at a power of 9 kW kg−1. The FSSAS device retained 91% of its capacitance at a 160° bending angle. These findings show that Dy2Se3 anchored on rGO using SILAR method is a promising candidate for supercapacitors.

Enhancing electrochemical performance of ultrasmall Fe2O3-embedded carbon nanotubes via combusting-induced high-valence dopants

• Ti 4+ , Sn 4+ , and Zr 4+ were successfully incorporated in Fe 2 O 3 by a flame synthesis. • The Fe 2 O 3 /CNTs nanocomposite was directly obtained by a flame synthesis. • Combustion reaction generating oxygen functional groups favor the wettability of electrode. • High-valence metal ions optimize the electron structure and enhance Na + adsorption. • The flexible Ti-FeO-CNT//MnO 2 achieved an exceeding high operating potential of 2.0 V. Doping is a reasonable solution to improve the electronic structure and surface properties of nanomaterials. Herein, we propose a rapid and simple methodology, flame synthesis, as an effective preparation strategy for incorporating high-valence metal ions (Ti 4+ , Sn 4+ , and Zr 4+ ) into ultrasmall Fe 2 O 3 on carbon nanotube support (i.e., M-FeO-CNT). The resulting materials exhibit not only a boosted Na + adsorption as shown by density functional theory (DFT) calculations, but also display an increased oxygen deficiency. The electrochemical activity and charge transfer efficiency of Fe 2 O 3 can be improved by reasonably substituting Fe 3+ with Ti 4+ , Sn 4+ , and Zr 4+ . The electrochemical investigation of Ti-doped Fe 2 O 3 (Ti-FeO-CNT) electrode demonstrates a splendid specific capacitance of 1.25 F cm −2 at 1 mA cm −2 in 1 M Na 2 SO 4 . This is significantly higher as compared to the capacitance of 0.48 F cm −2 . Flexible solid-state asymmetric supercapacitor Ti-FeO-CNT//MnO 2 is verified with operating voltage of 2.0 V and stability over 3000 cycles, and delivers a high energy density of 2.14 mWh cm −3 at power density of 25 mW cm −3 . The flame synthesis is expected to be widely applicable for the preparation of high-valence metal ions doped nanosized Fe 2 O 3 functionalized materials, thus opening up new avenues for energy and catalysis research.

Controlled synthesis of Fe3O4 microparticles with interconnected 3D network structures for high-performance flexible solid-state asymmetric supercapacitors

The eco-friendly Fe-based oxides have attracted broad attention in supercapacitors on account of large theoretical capacities and cost-effective technologies associated with production and recycling. However, inferior conductivity and bad structural stability are still the main obstacles for its promoted application than the competition. In this work, well-designed Fe 3 O 4 microparticles with homogeneous size distribution, high crystallinity, and amorphous carbon shell have been synthesized and deposited on carbon fabric as an anode electrode via a series of feasible techniques, including anodic electrodeposition, polymerization, and annealing. The interconnected 3D network structures of electroactive materials are featured by high specific surface area and fast diffusion rate of ions. The sufacial carbon layer of Fe 3 O 4 particles, serves as the armor, which not only boosts electrical conductivity, but also maintains structural stability of the electrode during electrochemical processes. The electrochemical results show that the binder-free anode exhibits a remarkable areal capacitance of 0.95 F·cm −2 , a wide potential window of 1.2 V, and an outstanding cycling stability in 1 M KOH electrolyte (capacitance retention of 93.39 % over 8000 charge-discharge cycles). After combining with a NiCo-based cathode, 4.93 F·cm −3 volumetric capacitance, 1.8 mWh·cm −3 energy density, and 198 mW·cm −3 power density are achieved for the flexible solid-state asymmetric supercapacitor, which displays impressive cycling stability, excellent mechanical flexibility, and obvious performance advantages as compared with previously reported flexible energy storage devices. This work provides a feasible strategy to design a flexible Fe-based anode with superior conductivity and long-term stability for high-performing flexible solid-state asymmetric supercapacitor towards practical applications. • High crystallinity Fe 3 O 4 microparticles were deposited on CF via stepwise strategy. • Polypyrrole was served as carbon source and barrier material during annealing. • The 3D network structures embrace good conductivity and fast diffusion rate. • The anode exhibits large capacitance, wide potential window and good stability. • Bending test and 8000 GCD cycles demonstrate the flexibility and cycling stability.

Hierarchically structured Fe2O3@C hollow acanthospheres on carbon cloth as anodes for high-performance asymmetric supercapacitors

The use of hematite (α-Fe2O3) as anode materials remains challenging because α-Fe2O3 with poor conductivity and sluggish ionic transportation in the oxide lattice during energy storage. Herein, the hierarchically structured hollow acanthospheres (Fe2O3 @C-HASs), for the first time, were prepared on carbon cloth (CC) by facile solvothermal method and self-sacrifice template method. Benefiting from its unique hierarchical hollow acanthospheres structures, a large specific surface area, transition-metal oxides and graphitized carbon layer, the hierarchically structured CC/Fe2O3 @C-HASs electrode delivers an outstanding areal capacitance of 1712.1 mF cm−2 at 5 mA cm−2, which are far superior to CC/Fe2O3-HASs (777.8 mF cm−2 at 5 mA cm−2). A 1.7 V flexible solid-state asymmetric supercapacitor (ASC) was successfully assembled with CC/Fe2O3 @C-HASs as the anode, NiO on carbon cloth (CC/NiO) as the cathode, exhibiting a maximum volumetric energy density of 2.87 mWh cm−3 at a volumetric power density of 40.20 mW cm−3, and excellent cycling stability (82.1% after 10,000 cycles). In this work, CC/Fe2O3 @C-HASs can be used as an ideal anode material, which can provide a reference for the rational design and preparation of electrode material to asymmetric supercapacitors.

Flexible Solid-State Asymmetric Supercapacitor with High Energy Density and Ultralong Lifetime Based on Hierarchical 3D Electrode Design

Flexible Solid-State Asymmetric Supercapacitor with High Energy Density and Ultralong Lifetime Based on Hierarchical 3D Electrode Design

Constructing a novel carbon skeleton to anchor Sn/SnO2 nanodots for flexible supercapacitor with excellent rate capability

Designing SnO2/carbon composites is an effective strategy to improve the conductivity and buffer the volume expansion of SnO2. However, it remains a challenge to combine SnO2 and carbon materials tightly as a stable integration. Herein, a facile and versatile strategy of Sn/SnO2 nanodots anchored tightly into carbon nanofibers (CNFs) with the decoration of graphene quantum dots (GQDs) for high performance supercapacitor is reported. Through a simple electrospinning and carbonization reduction process, a novel multidimensional carbon skeleton of GQD/CNF effectively improves the conductivity, and importantly, abundant Sn–O–C covalent bonds are constructed to anchor SnO2 nanodots tightly into GQD/CNF, suppressing SnO2 aggregation and facilitating electron/ion transfer kinetics. Consequently, as self-supporting and binder-free electrode material, Sn/SnO2/GQD/CNF displays high specific capacitance of 168.6 mA h g−1 (1349 F g−1) at 1 A g−1 with excellent rate capability (88.9% retention at 20 A g−1). Furthermore, a flexible solid-state asymmetric supercapacitor based on Sn/SnO2/GQD/CNF and GQD/CNF achieves a high energy density of 32.3 W h kg−1 at a power density of 800 W kg−1 with remarkable flexibility and cycling stability (86.1% retention after 5000 cycles). The excellent electrochemical performances demonstrate that this novel carbon skeleton anchored active materials shows great potential for electrochemical energy storage applications.

Interface modification based on MnO2@N-doped activated carbon composites for flexible solid-state asymmetric supercapacitors

One of the key issues to improve the energy density of supercapacitors is optimizing the performance of electrode materials. In this work, urea is used to modify the activated carbon (NAC), and then MnO2 are introduced on the surface of NAC by hydrothermal treatment to form three-dimensional structure composites (MnO2@NAC). After interface modification, the NAC has strong interactions with MnO2, which can ensure rapid charge transfer. The electrode material exhibits an excellent electrochemical performance (408.5 F g−1 at 0.5 A g−1) and a long-term stability (88.2% after 10,000 cycles). The 1.6 V flexible solid-state asymmetric supercapacitor is assembled with NAC as the anode, MnO2@NAC as the cathode, and PVA-KOH as the electrolyte with a superior specific capacitance (75 F g−1 at 1 A g−1), a high energy density (26.7 Wh kg−1 at 400 W kg-1) and an excellent rate performance (89.5% retention after 10,000 cycle). The density functional theory is used to calculate charge density difference, N-doping can strengthen the interactions at the interface of MnO2 and NAC, and enhance the charge transfer at the two-phase interface. This research can provide a thought for the rational design of carbon/metal oxide composites with excellent electrochemical properties in the future.

NiCo2O4 nanoneedle-nanosheet hybrid structure on CC substrate for high-performance flexible supercapacitors

In this paper, three different morphologies of NiCo2O4 nanoarrays, namely, nanosheet (S-NiCo2O4), nanoneedle (N-NiCo2O4) and their hybrid nanostructure (M-NiCo2O4) were successfully prepared on flexible carbon cloth (CC) by a hydrothermal method. The structures, surface morphologies and compositions of the samples were respectively characterized by XRD, SEM, EDS, and XPS, and the effect of NiCo2O4 morphologies on the electrochemical performances was systematically investigated. It is found that the M-NiCo2O4/CC electrode demonstrates the best supercapacitive performance among the three kinds of samples, typically its specific capacitance is 1347.4 F/g at 1 A/g (1509.1 F/cm2 at 1 mA/cm2), much higher than that of S-NiCo2O4 (938.4 F/g at 1 A/g) and N-NiCo2O4 (1022.4 F/g at 1 A/g). Meanwhile, the M-NiCo2O4/CC sample exhibits excellent rate capability (81.6%, from 1 A/g to 15 A/g) and cycling stability (92.4% retention after 10,000 cycles). In addition, an flexible solid-state asymmetric supercapacitor (ASC) with M-NiCo2O4/CC as positive electrode manifests great capacity retention (94% after 5000 cycles) and outstanding energy density of 41.7 Wh/kg at the power density of 750 W/kg. Moreover, the charge-discharge time shows no significant change after 2000 bends, demonstrating its application potential in the field of flexible SCs. The excellent performance is attributed to the unique hybrid porous structure of one-dimensional (1D) nanoneedles and two-dimensional (2D) nanosheets.

Hierarchical micro-nano structure based NiCoAl-LDH nanosheets reinforced by NiCo2S4 on carbon cloth for asymmetric supercapacitor

All-solid-state asymmetric supercapacitor based on hierarchical hybrid structure decorated with conductive NiCo 2 S 4 on NiCoAl-LDH has good energy density and power density. • NCA-LDH@NCS@CC is synthesized by a simple and low-cost hydrothermal method. • Hierarchical hybrid structure NCA-LDH@NCS is formed on carbon cloth. • NiCo 2 S 4 boosts overall electrical conductivity and hinders agglomeration of LDH. • NCA-LDH@NCS@CC//AC@CC is assembled with high energy density and cycle stability. Rational construction of microstructure and successful incorporation of multiple components offer a scalable strategy for applying electrode materials in asymmetric supercapacitors. Herein, a hierarchical hybrid structure of NiCoAl-layered double hydroxide (NCA-LDH) and ternary spinel NiCo 2 S 4 (NCS) on carbon cloth (CC) without binders is obtained through three-step hydrothermal reaction. The NCA-LDH@NCS@CC electrode exhibits outstanding electrochemical performance with 1775F g −1 at 1 A g −1 . Its capacitance retention is 79.6% when cycles reach 10 000 under 10 A g −1 , benefiting from the hierarchical hybrid structure and improved overall conductivity. A flexible solid-state asymmetric supercapacitor (FSASC) is assembled using NCA-LDH@NCS@CC and activated carbon coated on carbon cloth (AC@CC) for positive and negative electrodes, respectively. It possesses 33.13 Wh kg −1 under 750 W kg −1 , and also maintains a better cycling performance of 71.4% at 1 A g −1 after 10 000 cycles. Hierarchical hybrid NCA-LDH@NCS@CC electrode provides a favorable and scalable candidate for the development of FSASC device with superior performance.

Constructing nickel cobaltate @nickel-manganese layered double hydroxide hybrid composite on carbon cloth for high-performance flexible supercapacitors

Flexible supercapacitors have received considerable interest owing to their potential application in wearable electronics. Designing subtle hybridization of active materials and constructing smart electrode architectures are effective strategies for developing high-performance flexible supercapacitors. Herein, a hierarchically hybrid electrode is engineered by integrating nanoneedle-like structural NiCo2O4 and NiMn layered double hydroxide (NiMn-LDH) composite on highly conductive carbon cloth (CC). This architecture can endow abundant active sites, rapid electron collection pathways and efficient ion transport channels. The resultant hybrid electrode delivers high areal capacitance of 4010.4 mF cm−2, excellent cyclic stability and good rate performance. Furthermore, by pairing with an activated carbon (AC)/CC anode, a flexible solid-state asymmetric supercapacitor (ASC) is assembled, which exhibits the high areal energy/power density of 0.78 mWh cm−2/40.4 mW cm−2 and superior capacitive stability at bending deformation. Meanwhile, the assembled ASC possesses outstanding cycling stability with 97.7% capacitance retention after 10,000 cycles. This work presents the effects of rational design of hybrid electrode with high electrochemical properties and flexibility, holding great potential for flexible energy storages.

Realizing Superior Redox Kinetics of Hollow Bimetallic Sulfide Nanoarchitectures by Defect-Induced Manipulation toward Flexible Solid-State Supercapacitors.

As a typical battery-type material, CuCo2 S4 is a promising candidate for supercapacitors due to the high theoretical specific capacity. However, its practical application is plagued by inherently sluggish ion diffusion kinetics and inferior electrical transport properties. Herein, sulfur vacancies are incorporated in CuCo2 S4 hollow nanoarchitectures (HNs) to accelerate redox reactivity. Experimental analyses and theoretical investigations uncover that the generated sulfur vacancies increase the active electron states, reduce the adsorption barriers of electrolyte ions, and enrich reactive redox species, thus achieving enhanced electrochemical performance. Consequently, the deficient CuCo2 S4 with optimized vacancy concentration presents a high specific capacity of 231 mAh g-1 at 1 A g-1 , a ≈1.78 times increase compared to that of pristine CuCo2 S4 , and exhibits a superior rate capability (73.8% capacity retention at 20 A g-1 ). Furthermore, flexible solid-state asymmetric supercapacitor devices assembled with the deficient CuCo2 S4 HNs and VN nanosheets deliver a high energy density of 61.4 W h kg-1 at 750 W kg-1 . Under different bending states, the devices display exceptional mechanical flexibility with no obvious change in CV curves at 50mV s-1 . These findings provide insights for regulating electrode reactivity of battery-type materials through intentional nanoarchitectonics and vacancy engineering.

MnMoO4 nanorods-encapsulated carbon nanofibers hybrid mat as binder-free electrode for flexible asymmetric supercapacitors

In this work, the in-situ formation of MnMoO4 nanoparticles and simultaneous encapsulation within the porous carbon nanofiber (CNF) matrix through electrospinning-carbonization-thermal annealing processes were carried out. The results of various spectroscopic and morphological analyses confirmed the successful formation of rectangular-shaped MnMoO4 nanorods within the CNF matrix. The MnMoO4@CNF hybrid yielded a maximum specific capacitance of 389.7 F/g at 0.1 A/g, which is 3-folds more than that of CNF (123.4 F/g). The MnMoO4@CNF symmetric cell with an aqueous KOH electrolyte possessed a maximum energy density of 54.12 Wh/kg at a power density of 10 W/kg. The excellent capacitive performances of as-prepared MnMoO4@CNF nanofibers could be ascribed to their high specific surface area (229.35 m2/g) with wide mesoporous distribution (3–13 nm) and enhanced reactivity of the nano-sized MnMoO4 nanoparticles. The hybrid electrode demonstrated excellent cyclic stability with capacitance retention of 92.1% after 5000 cycles, suggesting restricted extrication of metal oxide from the CNF matrix during the charge-discharge process. A flexible solid-state asymmetric supercapacitor was assembled by using MnMoO4@CNF hybrid mat as a positive electrode and activated carbon cloth as a negative electrode. The polymer gel electrolyte (PVA + KOH) was used as electrolyte-cum-separator. The as-prepared MnMoO4@CNF//AC cell yielded a highest energy density of 37.46 Wh/kg and an equivalent power density of 278 W/kg. The present investigation could open new horizons in developing next-generation flexible solid-state supercapacitors for wearable electronics.

Supercapacitor devices based as SILAR synthesized ytterbium sulfide @ graphene oxide nanocomposite flexible thin film electrodes

• For first time Yb 2 S 3 , GO and GO/Yb 2 S 3 composite films are prepared by SILAR method. • The GO/Yb 2 S 3 composite thin film showed maximum Cs of 376 Fg −1 at 5 mV s −1 scan rate. • The FSS-SSC device showed Cs 58F g −1 , E. D. 23 Wh kg −1 and P. D. 0.43 kW kg −1. • The FSS-ASC device showed Cs 92F g −1 , E. D. 42 Wh kg −1 and P. D. 0.84 kW kg −1. • Glowing of 211 red LEDs panel showed the practical application of both devices. Ytterbium sulfide (Yb 2 S 3 ), graphene oxide (GO), and graphene oxide/ytterbium sulfide (GO/Yb 2 S 3 ) composite thin films were synthesized by binder-free successive ionic layer adsorption and reaction (SILAR) method. Formation of Yb 2 S 3 , GO and GO/Yb 2 S 3 composite thin films was confirmed by XRD and XPS techniques. Surface morphology and particle size of these films were observed through FE-SEM and TEM analyses. All thin films showed hydrophilic nature. The Yb 2 S 3 , GO and GO/Yb 2 S 3 composite thin films exhibited the maximum specific capacitance of 181, 193 and 376 F g −1 , respectively in 1 M Na 2 SO 4 electrolyte at scan rate of 5 mV s −1 . The flexible solid state supercapacitor (FSS-SSC) symmetric device was fabricated with GO/Yb 2 S 3 composite electrodes as an anode and a cathode and a flexible solid state asymmetric supercapacitor (FSS-ASC) device were fabricated with GO/Yb 2 S 3 as an anode and MnO 2 as a cathode electrode with the PVA-Na 2 SO 4 gel electrolyte. The FSS-SSC device showed specific capacitance 58 F g −1 , energy density 23 Wh kg −1 and power density 0.43 kW kg −1 . The FSS-ASC device showed specific capacitance 92 F g −1 , energy density 42 Wh kg −1 and power density 0.84 kW kg −1 . Both FSS-SSC and FSS-ASC devices showed coulombic efficiency of 88 and 79% for 10,000 GCD cycles, respectively. The FSS-ASC device showed better performance than the FSS-SSC device. The FSS-ASC device showed better performance than the FSS-SSC device.

In-Situ Growth of Urchin Manganese Sulfide Anchored Three-Dimensional Graphene (γ-MnS@3DG) on Carbon Cloth as a Flexible Asymmetric Supercapacitor.

In energy storage-device it is highly crucial to develop durable electrode materials having high specific capacitance and superior energy density without disturbing its inherent flexibility. Herein, we demonstrate three-dimensional graphene oxide decorated monodispersed hollow urchin γ-MnS (γ-MnS@3DG) via proficient one-step solvothermal method. The designed material delivers a remarkable capacitance of 858 F g-1 at 1 A g-1. A flexible solid state asymmetric supercapacitor (ASCs) device assembled using surface activated carbon cloth (CC) decorated with γ-MnS@3DG as positive and three-dimension graphene on carbon cloth (3DG@CC) as negative electrode, (γ-MnS@3DG//3DG). The device delivers 26 Wh kg-1 energy density at power density 500 W kg-1 @ 1A g-1 and retains favorable energy density 17.8 Wh kg-1 at an ultrahigh power density of 1500 W kg-1@3 A g-1. This carbon embedded transition-metal sulfide (TMS) based ASC demonstrates eminent mechanical flexibility under rigorous bending states maintaining invariant performance.