Solid Supercapacitor Research Articles

One-step self-assembled biomass carbon aerogel/carbon nanotube/cellulose nanofiber composite for supercapacitor flexible electrode

Flexible and exceptionally lightweight energy storage devices are crucial for wearable electronic gadgets. Biomass materials are emerging as ideal flexible electrode components due to their biocompatibility and non-toxic nature. In this study, pineapple leaf fibers were utilized to create activated biomass carbon aerogel (Bio-CAA). Then, carbon nanotubes (CNTs) were integrated as conductive additives, combined with sturdy pineapple leaf cellulose nanofibers (CNFs) to establish a robust 3D framework. Utilizing a one-step self-assembly method, carbon aerogel/carbon nanotube/carbon nanofiber (Bio-CAA/CNT/CNF) flexible composite electrode materials were successfully synthesized. The porous structure of Bio-CAA effectively minimized the aggregation of CNTs, thereby significantly enhancing the electrochemical performance of the electrode material. The characterization indicated that the carbon aerogel composite exhibited a high specific surface area (684.275 m2 g−1) after tablet compression. The material was light yet robust, capable of being bent arbitrarily and recovering its original shape and withstanding 400 Kpa of pressure at an 88 % strain rate, demonstrating excellent mechanical properties. In a three-electrode system, the Bio-CAA/CNT/CNF = 19:1:1 based electrode exhibited a capacitance of 481 F g−1 at a current density of 1 A g−1. The CAA/CNT/CNF = 19:1:1 based solid symmetric supercapacitor (SSC) displayed excellent cycling stability, preserving 91.7 % capacitance after 10,000 cycles at a current density of 5 A g−1. It achieved an energy density of 39.63 Wh kg−1 at a power density of 500 W kg−1. This biomass-derived carbon aerogel-based composite material demonstrates exceptional energy storage capabilities, and its lightweight attributes make it highly suitable for use in flexible displays, wearable devices, and related fields.

Biscrolled hierarchical hybrid structure of PEDOT:PSS/CNTs-NMP yarn based solid state linear supercapacitor for wearable e-textile

The environmental friendly flexible solid state linear supercapacitor (FSLSc) based on the hierarchical hybrid yarn with core-shell type structure of poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) and hydrophilic carbon nanotubes (CNTs) sheet, fabricated using novel biscrolling technique is proposed. The hierarchical hybrid yarn structure of the electrode establishes the improved electrochemical interface of PEDOT:PSS with the both the hydrophilic CNTs and an aqueous PVA/H3PO4 gel electrolyte. The exterior surface of the yarn electrode rich in PEDOT:PSS which interact with ions from electrolyte and stores charges faradaically while the core region with dense CNTs yarn contributes with its multifunctional capabilities such as EDLC type capacitor, current collector and mechanical support. The observed two-fold decrease in ESR value (∼49Ω) and two-fold increase in capacitance (∼112.76 F/g) for hybrid yarn electrode with N-methyl-2-pyrrolidone (NMP) treated hydrophilic CNTs compared to the one with pristine CNTs, confirms the improved interface of PEDOT:PSS formed with hydrophilic CNTs and aqueous electrolyte. The FSLSc devices with NMP treated CNTs hybrid yarn electrodes exhibited excellent electrochemical performance in terms of the maximum power and energy density of 980 W/kg and 3.799 Wh/kg, respectively. The FSLSc displayed remarkable cycling performance upto 5000 cycles of charge-discharge and a robust bending stability after 1000 bending cycles, making it promising for practical application of the next-generation flexible solid state electrochemical energy storage in e-textiles.

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.

Chitosan modified graphene oxide with MnO2 deposition for high energy density flexible supercapacitors

To obtain a flexible composite electrode material with excellent electrochemical performance, chitosan (CS)/graphene oxide (GO) composite pretreated from microwave hydrothermal is adopted as the carbon substrate, and MnO2 active material is uniformly deposited on their surface through anodic electrodeposition. In this composite system, CS penetrates into graphene sheets as small molecule units, forming NH-C=O groups with GO via dehydration condensation, which effectively inhibits the stacking of GO and improves the specific surface area, conductivity, as well as the wettability of the carbon support. MnO2 bonding with heteroatom N from CS enables high active material loadings and forms stable three-dimensional network structure, facilitating the enhanced electrochemical performance. Results indicate that increasing depositing MnO2 amount leads to more defective structures of the composite, which promotes their electrochemical performance when used as electrode material. The area specific capacitance of the optimal composite reaches 3553.74 mF/cm2 at 5 mA/cm2 in 1 M Na2SO4 electrolyte. Kinetic analysis shows the energy storage process is capacitance-dominated, with the redox reactions of MnO2 being the main contributor. The prepared asymmetric solid supercapacitor delivers an energy density high up to 0.585 mWh/cm2 at power density of 3000 mW/cm2, and their excellent flexibility makes them promising candidates as flexible sensor.

Redox additive effects on the electrochemical performance of hydrothermally grown, binder-free CuO nanosheets in aqueous electrolytes

Adding redox additives into the traditional electrolytes is an efficient approach to achieving high-performance binary metal oxide electrode-based supercapacitors (SCs). Herein, binder-free CuO nanosheets are developed on nickel foams via a facile hydrothermal approach, and their charge storage performance in K3[Fe(CN)6] (KFCN) redox additive electrolyte is investigated. In a three-terminal (3T) configuration, the as-prepared electrode demonstrates a remarkable capacitance of 2755 mF cm−2 (2296 F g−1) in KFCN redox additive electrolyte, which is 10 times greater than that obtained in bare KOH electrolyte (266 mF cm−2 or 222 F g−1). Further, the 93 % capacitance retention after 2000 cyclic voltammetry cycles confirms the reasonable stability of the CuO electrode for SCs with redox additives electrolyte. Additionally, the assembled CuO electrodes-based solid state symmetric supercapacitor (SSC) with redox additive gel electrolyte achieves a maximum energy density (Es) of 31.5 Wh kg−1 at a power density (Ps) of 500 W kg−1. Furthermore, red LEDs are operated by the power source of two SSCs connected in the serial mode for 130 sec. This studies imply that utilizing CuO within redox additive electrolytes could present a simple and cost-effective approach for developing high-energy storage supercapacitors.

Enhanced electrochemical performance of in situ polymerized V2O5-PANI nanocomposites and its practical application confirmation by assembling ionic liquid as well as solid state-based supercapacitor device

In the present study, in situ polymerization of anilinium hydrochloride over V2O5 was used to prepare PANI nanocomposites with varying weight percentage of V2O5 (10, 20 and 30 wt%). V2O5 nanoparticles were synthesized using a simple chemical approach and their purity was confirmed through Rietveld refinement. It confirmed the advantageous electrochemical activity of V2O5 with a higher oxidation state of vanadium (V+5), enabling efficient electron storage. For fabricated electrode materials, the pair of redox peaks as well as their shape in CV suggests the faradic pseudocapacitive properties. Among all prepared electrodes, 20 wt% V2O5-PANI (PV2) nanocomposite demonstrates maximum specific capacitance of 820.5 Fg−1 at a current density of 1 Ag−1 with decent capacitive retention of 88 % after 1000 charge–discharge cycles. PV2 electrode also has a lower charge transfer resistance (Rct) of 0.5 Ω and lesser solution resistance (Ro) of 0.31 Ω in 6 M KOH electrolyte which is also responsible for good electrochemical performance. The higher capacitance value and decent stability of PV2 confirmed its ordered structure with more active sites shown through FESEM, which significantly contributes to efficient ion and electron transfer. In addition, the symmetric supercapacitor configuration of PV2 electrodes exhibits good energy and power densities of 4.6 Wh kg−1 and 80.7 W kg−1, respectively. Finally, the ignition of a red LED using three PV2//PV2 symmetric devices connected in series underscores its potential to advance energy storage applications.

Promoted OH– adsorption and electron-transfer kinetics by electrospinning mono-disperse NiCo2S4 nanocrystals within porous CNFs for solid asymmetric supercapacitors

Bimetallic sulfide NiCo2S4 has been regarded as a potential supercapacitor electrode material with excellent electrochemical performance. However, the origin of its high specific capacity is little studied, and the design of a rational structure still remains a challenge to exert its intrinsic advantage. In this work, the advantage of NiCo2S4 over NiS and CoS is explained by density functional theory calculation from the aspects of energy band, density of electronic states and OH– adsorption energy. It is proved that the synergistic effect of Ni and Co in NiCo2S4 can reduce its OH– adsorption energy and provide more active electrons near the Fermi level, thus promoting electrochemical reaction kinetics in supercapacitors. Then, a simple electrospinning method is used to in-situ load mono-disperse NiCo2S4 nanocrystals within amorphous carbon nanofibers, obtaining a porous, lotus-leaf-stem-like one-dimensional nanocomposite of NiCo2S4/CNF. Ex-situ XPS characterization confirms that the proportion of metal ions involved in electrochemical reactions and the number of transferred electrons in NiCo2S4/CNF during the redox reaction are significantly higher than those in mono-metallic sulfides (NiS/CNF and CoS/CNF), verifying the calculation results. With its boosting reaction kinetics, the NiCo2S4/CNF gives the specific capacity of 757.97C g−1 at 1 A/g and the capacity retention of 95.15 % after 10,000 cycles at 5 A/g, both greater than NiS/CNF and CoS/CNF. The NiCo2S4/CNF, as the positive electrode, and activated carbon, as the negative electrode, are assembled into liquid-state and solid-state asymmetric supercapacitor (ASC) devices, and both show high power density (760.6 W kg−1 for liquid-state device and 1067.4 W kg−1 for solid-state device), high energy density (52.25 Wh kg−1 for liquid-state device and 48.54 Wh kg−1 for solid-state device) and great cycle stability. Moreover, the solid-state ASC device possesses excellent low temperature capacity and reversibility, further demonstrating the wide application potential of the NiCo2S4/CNF composite.

Hydrothermally synthesized three-dimensional hierarchical CuO nanomaterials for energy storage applications

Copper oxide is a promising material for various applications because it exhibits excellent properties in different nanostructures. Highly porous nanomaterials are better suited to a variety of applications, including charge storage supercapacitors. In this research article, the binder-free, flower-like three-dimensional hierarchical copper oxide (3Dh-CuO) nanomaterials on stainless steel (SS) substrates via a hydrothermal technique for charge storage supercapacitor applications has been studied. The flower-like 3Dh-CuO monoclinic polycrystalline structures were confirmed by morphological and structural analysis. The quantum confinement effect was observed on a flower-like 3Dh-CuO nanomaterial. The Quantum Confinement Semiconductor (QCS) exhibits excellent charge storage electrochemical performance. The maximum specific capacitance of binder-free, flower-like 3Dh-CuO nanomaterials is 1312.8 Fg−1 at a 2 mVs−1 sweep rate and 1301.3 Fg−1 at a 1.0 mA cm−2 current density in 1 M KOH electrolyte. The maximum energy density (ED) is 152.73 Wh kg−1 and the power density (PD) is 4.33 kW kg−1. The Solid Asymmetric Hybrid Supercapacitor (SAsHSc)device of the flower-like 3Dh-CuO shows a capacitance of 172.8 Fg-1 at 10 mVs−1 in the 1.6 V potential, with the highest cycling stability up to 3000 cycles having 77.66% retention. The binder-free, flower-like 3Dh-CuO electrodes have been considered a potential candidate material for electrochemical supercapacitors.

Co-electrodeposition hybrid reduced graphene oxide and nickel-cobalt selenide nanosheets on silicon nanowires for high-performance supercapacitor

Due to inherent compatibility with IC technology, 3D silicon is prone to build a skeleton for the energy storage electrodes. Herein, a unique 3D hierarchical core-shell electrode was first developed with silicon nanowire arrays (SiNWs), metal selenide (TMSe) and reduced graphene oxide (RGO) nanosheets, where SiNWs decorated with Ni particles (Si/Ni) served as the conductive core and co-electrodeposited hybrid nickel-cobalt selenide (NCSe) and RGO nanosheets (NCSe-RG) functioned as the high capacitive outer shell. Owing to the synergy effect between NCSe and RGO, high-speed electron transport channels of Si/Ni, and abundant electroactive sites of porous NCSe layer, the synthesized Si/Ni/NCSe-RG electrode delivered a large capacitance of 2268 F g−1 (1973 mF cm−2) at 1 A g−1 which was higher than most reported silicon-based electrodes, and an excellent rapid-charging capability (1540 F g−1 at 30 A g−1). Furthermore, a solid asymmetric supercapacitor (SC) was prepared by using Si/Ni/NCSe-RG as the positive electrode, demonstrating an excellent energy density of 53.23 Wh kg−1 at the power density of 800 W kg−1. Our results suggest that high-performance SC electrodes can be engineered with TMSe and 3D silicon with a simple and time-saving method.

Thermal stability on solid state symmetric supercapacitors with hydrothermally synthesized Cu2CoSnS4 electrodes

The effects of thiourea concentration on crystal phase, morphology, and the elemental composition and electrochemical characteristics (ECs) of hydrothermally synthesized Cu2CoSnS4 (CCTS) electrodes are systematically studied. In a three-terminal (3T) configuration, layered structure morphology with Cu-rich chemical composition-based electrodes exhibits higher ECs than other electrodes. The thermal reliability of devices up to 60℃ is practically validated via temperature-dependent cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements for single symmetric solid-state supercapacitor (SSC) devices. The maximum of Cp=(251.87 ± 30.56)Fg−1, E=(89.55 ± 10.35)Whkg−1, P=(800 ± 40.32)Wkg−1 and voltage window expanded up to 1.6 V including red LED operation for 6 min are achieved for the serially connected two SSCs at 1Ag−1, indicating that CCTS can be one promising electrode material for SSCs.

Nickel cobalt sulfide composite nanosheet anchored on rGO as effective electrode for quasi-solid supercapacitor

A solid supercapacitor based on inorganic/organic composite electrolyte has great promise as a fresh wave of energy storage structure in building engineering owning to its inherent mechanical robustness. Unfortunately, the limited capacity and energy density of these supercapacitors are still challenging. Here, rGO/NixCoyS electrodes were fabricated by in-situ growth on nickel foam (NF). The edge sulfur-enriched NixCoyS nanosheets were equally anchored on rGO surface, increasing the number of electrochemical active sites, accelerating ion diffusion and improving the electrical conductivity. The morphology and electrochemical behavior of the rGO/NixCoyS composite are remarkably affected by the Ni to Co molar ratio. It turned out that the rGO/NixCoyS composite with a Ni to Co molar ratio of 1:1 (rGO/Ni1Co1S) exhibited a high capacitance of 4.55 F cm−2 at 1 mA cm−2. Subsequently, a novel quasi-solid supercapacitor was assembled using rGO/Ni1Co1S cathode, rGO/Fe2O3 anode as well as inorganic/organic composite solid electrolyte. The device achieved a high energy density of 3.6 μWh cm−2 at a power density of 163.2 μW cm−2, and moderate self-discharge (SDC) process, outperforming those of earlier reported structural devices. The practical application demonstration proves the feasibility of ternary rGO/Ni1Co1S electrode combined with inorganic/organic composite solid electrolyte in building energy storage field.

A positive electrode with thoughtful diffusion capacitance for solid flexible supercapacitor: N-6 doped porous carbon shell coated Cu doped Mn[sbnd]Co LDO core

The suitable proportion of diffusion contribution during the electrochemical process could influence the electrochemical performance of electrode materials. An effective method is that tuning the diffusion reaction contribution via doping heteroatom, introducing defects or surface modification. In this work, a unique core-shell structure material Cu-Mn-Co LDO-C is obtained. Benefitting from Cu pre-doped into MnCo LDO, large amount of oxygen vacancies is introduced to enhance electrochemical performance; N-6 doped porous carbon shell protects Cu-Mn-Co LDO core and improves electrochemical performance of Cu-Mn-Co LDO-C further. In addition, doping Cu broadens potential window of Cu-Mn-Co LDO-C surprisingly. Cu-Mn-Co LDO-C presents 5028.7 mF cm−2 at a current density of 1 mA cm−2 with a facilely reached potential window of 0–0.65 V finally, and retains 73.4 % diffusion contribution at a scan rate of 1 mV s−1, 18.3 % at 100 mV s−1. After 10,000 cycles at 2 mA cm−2, Cu-Mn-Co LDO-C keeps 90.3 % of initial capacitance. Using Cu-Mn-Co LDO-C as positive and Fe3O4-C as negative to fabricate a solid flexible asymmetrical supercapacitor (SAS), this SAS presents a considerable energy density that attribute to the high working potential of positive Cu-Mn-Co LDO-C. SAS could working stably at a potential window of 0–2.2 V, and presents the highest energy density 243.1 μWh cm−2 at a power density of 2.8 mW cm−2, remains 203.0 μWh cm−2 at the highest power density of 55.4 mW cm−2. A hand ring that was assembled by three SAS which contacted in series could light a highest rated voltage white LED more than 10 min. As a result, Cu-Mn-Co LDO-C is an ideal candidate for flexible positive electrode in the field of smart, portable energy storage.

Self-supporting electrodes with in situ built aniline on carbon fibers and reduced graphene oxide covalently for stable flexible supercapacitors

Practical applications of flexible electronics have challenged the stability and cycle performance of flexible supercapacitor under continuous mechanical deformation, thus flexible electrode with stable structure has to be considered to maintain high-quality performance. A covalent modification strategy is present here to improve the stability of electrodes. Graphitized carbon cloth (GCC) and reduced graphene oxide (rGO) that modified with aniline by Suzuki reaction, are covalently bonded together with the polymerization of aniline (PANI). The electrode (GCC-PANI-rGO) modified by covalent bonds is stable enough to remain 97.73 % initial specific capacitance after charge-discharge 15,000 times at 40 mA/cm2. The capacitance retention of asymmetric flexible solid supercapacitor (FSSC) prepared by GCC-PANI-rGO and GCC is 108.78 % after 10,000 times mechanical folding. The electrode formed a π-π conjugation system through Suzuki reaction possesses low charge transfer resistance (0.428 Ω), and exhibits high specific capacitance and energy density that up to 11.825 F/cm2 and 1.642 mWh/cm2 at 1 mA/cm2. The energy density of FSSC is 0.266 mWh/cm2 at 1 mA/cm2 and surpasses most FSSC based on PANI and graphene. This work gives an essential covalently synthetic strategy for flexible supercapacitor with stable electrochemical performance in application.

Enhanced electrochemical performance of CuCo2O4 nanowire arrays based solid-state symmetric supercapacitor by K3[Fe(CN)6] redox additive electrolyte

The redox additive in an aqueous gel electrolyte is reported as one of the efficient methods to improve the electrochemical supercapacitor performance. Here, we report the role of redox additive, potassium ferricyanide((K3[Fe(CN)6]), referred to as KFCN) for improving the electrochemical performance of binder-free, CuCo2O4 (CCO) nanowire arrays (NWs) based solid state symmetric supercapacitors (SSCs). The crystal structure and morphology of prepared CCO films are confirmed by X-ray diffraction (XRD) and field emission-transmission electron microscopy (FE-TEM). The elemental composition of CCO films is estimated as Cu0.5Co2.77O3.82 via energy-dispersive X-ray spectroscopy (EDS) analysis. Surprisingly, the areal capacitance (or energy density at 5 mAcm−2) is significantly improved from 0.58 F cm−2 (or 0.016 mWh cm−2) to 10.5 F cm−2 (or 0.296 mWh cm−2), respectively, after the addition of KFCN to aqueous KOH electrolyte, as compared to bare KOH. Furthermore, CCO exhibits decent cyclic stability with 90 % capacitance retention up to 5000 CV cycles at the scan rate of 100 mV s−1. Moreover, 2-terminal CCO NWs-based SSCs, employed with PVA-KOH-KFCN gel electrolyte, demonstrate a wider potential window of −0.9 to 0.9 V (1.8 V) with a 7-fold increase of energy density from 9.1 to 65 Wh kg−1, as compared with that of PVA-KOH gel electrolyte. As practical validation, the operation of Red-LED for 3 min is demonstrated with PVA-KOH-KFCN gel-based SSC, manifesting that adding redox substance in aqueous electrolytes is one of the promising strategies for portable and wearable energy storage systems.

Porous polymer cement composites for quasi-solid graphene supercapacitors

We reported a strong and cheap polymer modified Portland cement (PC) composites with interconnected pores as solid electrolyte for graphene supercapacitors. The porous polymer cement composites solved the low ionic conductivity question of construction materials. Herein, the effects of PAA molecular weight, PAA content and curing age on electrical energy storage and mechanical property were investigated in detail. The PAA (Mw = 5000)/PC-5 % sample delivers the best multifunctionality. Moreover, the as-assembled solid supercapacitor exhibits an optimum energy density of 15.93 mW h cm−2, as well as a considerable compressive strength of 16.2 MPa at 28 days. In addition, introducing PAA can result in high porosity which is conductive to ion migration. The symmetric electrode is directly loaded with GO on Ni foam by electrophoretic, followed by high temperature thermal reduction. The integrated solid supercapacitors are effective, holistic and effortless to operate at room temperature, and they exert a crucial role in energy storage field of inorganic building materials application.

CNT yarn based solid state linear supercapacitor with multi-featured capabilities for wearable and implantable devices

CNT yarn based solid state linear supercapacitor with multi-featured capabilities for wearable and implantable devices

Gel combustion synthesized NiMoO4 anchored polymer nanocomposites as a flexible electrode material for solid state asymmetric supercapacitors

Recent research has focused on the search for new electrode materials to improve the specific capacitance of supercapacitors. Conductive polymers and metal oxides have been extensively tested as electrode materials for supercapacitors. Incorporating both conductive polymers and metal oxides into a composite provides excellent results for the electrochemical performance of supercapacitors. In this present work, we have fabricated the nanoscale α-NiMoO4 particles that enwrapped on electronically conducting polymer nanocomposites (PNCs) based on Polyvinyl alcohol (PVA)/Poly(vinyl) pyrrolidone (PVP) for supercapacitor applications. The different concentrations of PVA/PVP with α-NiMoO4 loaded polymer nanocomposites were developed by using a solution casting method. All the polymer nanocomposites have been subjected to Scanning Electron Microscopy (SEM), Fourier Transforms Infrared (FTIR), X-ray diffraction (XRD), and electrochemical studies. The prepared PNCs surface morphology has been acquired as a non-uniform rod-like structure. The electrochemical performances of the prepared PNCs have been investigated and the resultant value of the maximum specific capacitance is 15.56 F g−1 for 1 wt % of α-NiMoO4 nanoparticles(NPs) loaded polymer blended electrode at a scan rate of 5 mVs−1. The prepared PNCs exhibit 97.12% of columbic efficiency studied by using two electrode systems at room temperature in an aqueous electrolyte solution of 3 M KOH. From these investigation, it has been revealed that the PVA/PVP/α-NiMoO4 composites could be portable and flexible electrodes for energy storage applications.

Redox active cement-based electrolyte towards high-voltage asymmetric solid supercapacitor

The energy storage devices in civil engineering field are limited by low ionic conductivity and capacity. Herein, a kind of bifunctional redox active cement-based composite serving as electrical energy storage and building structural component function was developed. The effect of K3Fe(CN)6 on the ion migration, pore structure, mechanical and electrochemical property were investigated. Results show that the appropriate incorporation of K3Fe(CN)6 increases the pores number, ion penetration and ionic conductivity of samples. In addition, two sizes of all-solid-state devices assembled by rGO/Fe2O3 electrode and redox active cement-based electrolytes both deliver an extended operating potential window (OPW) of 1.5 V. The 1 cm2 cell with 0.04 redox active cement-based electrolyte delivers superior areal capacitance of 166 mF cm−2 at an areal energy density of 51.87 μWh cm−2 and areal power density of 7.5 mW cm−2. The 100 cm2 cell exhibits a high energy density of 23.10 μWh cm−2, together with power density of 75 μW cm−2. As an application, with three 100 cm2 devices connected in series, a green light emitting diode (LED) can be successfully lit up for the first time and last for 260 s after being charged to 4.5V. The vision of using large buildings to store solar energy can greatly reduce the carbon footprint of building and achieve sustainable development.

Polypyrrole embedded in nickel-cobalt sulfide nanosheets grown on nickel particles passivated silicon nanowire arrays for high-performance supercapacitors

Metal sulfide-based composites have been considered as promising electrode materials for energy storage, but the fabrication process of such composites is complicated and requires a multistep hydrothermal treatment. Considering the integration with the silicon-based microelectronics, electrode materials prepared from 3D silicon and metal sulfide are needed. In this work, a hierarchical multi-shelled Ppy-NCS@Ni@SiNWs electrode was successfully developed with a simple, clean and low-cost method, where polypyrrole (Ppy) and nickel–cobalt sulfide (NCS) were co-electrodeposited on nickel particles passivated silicon nanowire arrays (SiNWs). Benefiting from the large surface of SiNWs, high conductivity of nickel passivation layer and the synergy effect between Ppy and NCS including large capacity, hydrophilic surface and high mechanical strength, the as-prepared electrode demonstrated a remarkable specific capacitance (1602 F g-1 at 1 A g−1), an excellent rate capacity (1348 F g-1 at 30 A g−1) and a high cycling stability (91.6 % of initial capacitance after 10,000 cycles). Additionally, a solid asymmetric supercapacitor was fabricated by employing Ppy-NCS@Ni@SiNWs as the positive electrode, which realized a superior energy density of 131.322 Wh kg−1 at an outstanding power density of 1.44 kW kg−1. The findings demonstrate that the hybrid composite of conductive polymer and metal sulfide grown on 3D silicon has enormous potential for energy storage materials.

Assembling zinc cobalt hydroxide/ternary sulfides heterostructure and iron oxide nanorods on three-dimensional hollow porous carbon nanofiber as high energy density hybrid supercapacitor

The critical challenge of supercapacitors lies in sluggish kinetics of electrodes and undesirable specific capacitance during charge discharge process including large volume change and inferior cyclic stability. In this work an elaborately designed three dimensional hierarchical heterostructure comprising ternary metal sulfides completely covered by nickel cobalt layered double hydroxide (NiCo-LDH@ZNCS) core shell arrays on electrospun three-dimensional hollow porous carbon nanofiber and used as free-standing electrode material for supercapacitors. The original built-in interfacial potential between NiCo-LDH and ZNCS on conducting three dimensional hollow PCF can acquire multidimensional channels for ion/electron transfer and validate to be a highly capacitive cathode material with a high specific capacity of 407.11 mA h g−1 at the current density of 1 mA cm−2 maintaining outstanding rate performance. The iron oxide nanorods (Fe2O3-PCF) anode (216.15 mA h g−1 at the current density of 1 mA cm−2) match well to the cathode. Benefiting from the powerful synergistic effect, the assembled quasi solid state asymmetric supercapacitor can deliver ultrahigh energy density of 111.72 W h kg−1 at a power density of 243 W kg−1 and extra ordinary life cycle stability (95.2 % capacity retention after 20,000 charge discharge cycles). Such superior electrochemical performances are attributed to the multidimensional nanostructures, porous carbon networks, improved conductivity, and synergistic interaction between the active components of NiCo-LDH/ZNCS arrays. This approach provides a new perspective for rational design of high energy density hybrid supercapacitors, holding unbounded possibilities in this energy dependent world.