High-performance Hybrid Energy Storage Research Articles

Unleashing asymmetric polyoxometalate redox activators on 2D interfaces for high-performance hybrid energy storage

Polyoxometalates (POMs) are an intriguing class of compounds with remarkable redox capabilities, making them prime candidates for energy storage applications. However, the challenge lies in their heightened solubility, which limits their direct use as electrode materials. The successful confinement of POMs into suitable templates becomes pivotal in creating supercapacitors with elevated energy and power densities. Our study showcases the successful integration of asymmetric POMs (Mo and W) onto two-dimensional (2D) templates, specifically graphene oxide and MXene. The synergy could benefit from the inherent charge storage capabilities of the high surface area 2D substrates that could provide a template for uniform dispersion of POMs enabling additional faradaic capacitances at electrode/electrolyte interface. A hybrid supercapacitor (HSC) fabricated effectively utilizes these faradaic capacitances across an extended potential window of 1.2 V in a 2 M H2SO4 solution, yielding impressive capacitance values of 110.4 F/g at a current density of 1 A/g. Furthermore, our synthesis strategy could effectively anchor POMs resulting in a high capacitive retention of 92.4% at high scan rates of 50 mV/s after 5000 cycles. Our approach can be effective in designing POM based pseudo capacitive electrodes with excellent structural stability and surface properties that can be relevant to many electronic and energy applications.

Graphene electrode functionalization for high performance hybrid energy storage with vanadyl sulfate redox electrolytes

Hybrid energy storage devices face the challenges of pairing suitable redox chemistries with stable electrodes to simultaneously realize the energy storage mechanisms of batteries and supercapacitors. Functionalization of electrodes enables improved catalytic activity and long-term cycling stability by introducing desired functional groups. Herein, we demonstrate novel hybrids using reversible vanadium (V) redox couples along with functionalized graphene electrodes. Redox couples of V(III)/V(IV) and V(IV)/V(V) are formed upon initial charging of the V(IV) electrolyte present in both half-cells, leading to a Galvani potential difference during operation. Moreover, functionalized electrodes with high surface area facilitate both facile redox reactions and electric double layer formation. The unique chemistry offers a straightforward device regeneration step which significantly enhances the cycling stability. Optimized hybrids exhibit a battery-like specific capacity of 700 mAh g−1 at 0.5 A g−1, a supercapacitor-like capacitance of 850 F g−1 over 10,000 cycles at 10 A g−1, and a very low self-discharge rate. This corresponds to power densities of 0.3 kW kg−1 and 9.2 kW kg−1 and energy densities of 363.8 Wh kg−1 and 24.9 Wh kg−1, respectively, outperforming similar aqueous redox hybrid systems.

Ultrahigh performance asymmetric supercapacitor devices with synergetic interaction between metal organic frameworks/graphene nano platelets and redox additive electrolyte

One of the key challenges has been taken to design high performance hybrid energy storage devices using electrodes based on capacitive graphene nanoplatelets (GNPs) and pseudocapacitive metal organic frameworks (MOFs) with high energy storage, power density and long-life cycles. Herein, we are introducing novel hybrid capacitors based on highly porous composite electrodes of ZIF-67/GNPs and ZIF-8/GNPs and redox additive electrolyte (RAE) that is, 0.2 M [K3(Fe (CN)6)] in 1 M Na2SO4. The ZIF-67/GNPs and ZIF-8/GNPs composite electrodes were used to fabricate the asymmetric supercapacitor devices using MOFs/GNPs as a positive electrode and GNPs as the negative electrode in the presence of RAE exhibited high energy and power densities of 85.8 W h kg−1 and 60.7 W h kg−1 and 7500 W kg−1 and 7370 W kg−1, respectively at current density of 1 Ag−1. The asymmetric devices retain excellent capacitances of up to 97.7% (ZIF-67/GNPs) and 97.1% (ZIF-8/GNPs) along with remarkable columbic efficiencies near 100% after 10,000 charge discharge cycles at 2 Ag−1 in a wide voltage range of (0.0–1.5 V).

Binary composites of sonochemically synthesized cobalt phosphates/polyaniline for supercapattery devices

This work focuses on enhancing the electrochemical performance of cobalt phosphate (Co3(PO4)2) via polyaniline (PANI) for high performance hybrid energy storage devices also termed as supercapattery. For projected drive binary composites cobalt phosphate and PANI at different Wt% were made and composition of PANI was optimized. The composition reveals prime electrochemical performance possessing a maximum specific capacity of 638 C/g while operating at 0.8 A/g in three electrode assembly. The charge storage performance was further scrutinized in two electrode assembly, a supercapattery device is fabricated by coupling Co0.70 (PO4)2/PANI0.30 (S3) (positive) and activated carbon (negative) electrodes. The developed device exhibits exceptional energy storage performance with an ultrahigh specific energy (ES) of 53.2 Wh/kg along with a specific power (PS) of 432 W/kg at 0.5 A/g. The maximum specific power delivered by assembled supercapattery device is 6027 W/kg in parallel with an specific energy of 7.1 Wh/kg. The supercapattery device also demonstrates an outstanding cyclic stability potential of 97.6% and excellent columbic efficiency of 87% after 5000 continuous charge/discharge cycles. Furthermore, the Dunn's model is employed to calculate the capacitive and diffusive impact in total capacity of the device. The outstanding performance of the developed binary composites compared with previously reported literature, provides an efficient and preferable electrode material for potential applications in high-performance energy storage technologies.

Influence of template agent on NiMoO4 for high-performance hybrid energy storage devices

Here, NiMoO4 was successfully synthesized via a mild hydrothermal method combined with annealing treatment. The effects of nickel sources and Tween 80 on the morphology and electrochemical performance of NiMoO4 electrode for hybrid energy storage device were investigated in detail. When nickel sulfate as a nickel source, NiMoO4 exhibited a one-dimensional needle structure and reached the best specific capacity of 498 C g−1 at 1 A g−1. Moreover, the different dosages of Tween 80 all improved the morphology and capacity of one-dimensional needle NiMoO4. When the dosage was 0.005 mol, NiMoO4 nanorods formed a flower-like morphology and a higher specific capacity of 754 C g−1. Furthermore, we used the optimized NiMoO4 assembled a hybrid device which reached 68.36 Wh kg−1 at a power density of 923 W kg−1.

Single-walled carbon nanotubes/Ni–Co–Mn layered double hydroxide nanohybrids as electrode materials for high-performance hybrid energy storage devices

Nanohybrids which combine SWCNTs and Ni–Co–Mn layered double hydroxides are prepared by a facile hydrothermal process and investigated for the first time as electrode materials for hybrid energy storage devices. The nanohybrid made with a precursor weight ratio of SWCNTs and Ni–Co–Mn layered double hydroxide of 10:90 exhibits the highest capacity of 912 C g−1 at 1 A g−1, while the nanohybrid made with a precursor weight ratio of 30:70 shows the highest rate retention of 65% from 1 A g−1 (672 C g−1) to 50 A g−1 (435 C g−1) and the best capacity retention of 70% after 10000 cycles. Moreover, the charge transfer mechanism of the Ni–Co–Mn layered double hydroxides during charge/discharge is investigated through in-situ X-ray absorption near-edge spectra. To demonstrate practical hybrid energy storage applications, two nanohybrid//SWCNTs asymmetric energy storage devices are assembled and tested in pouch cell configuration. Their performances under folded condition are also evaluated, revealing great potential for flexible hybrid energy storage applications.

Facile synthesis of a novel Fe3O4-rGO-MoO3 ternary nano-composite for high-performance hybrid energy storage applications

Supercapacitors (SCs) have been considered as inspiring energy storage devices due to the long cycle lifetime and high power densities. However, their energy density is limited due to the low capacitance of cathode materials and inferior cycling stability at practically useable potential windows >1.2 V. In this paper, we demonstrate the synthesis of a novel ternary Fe3O4-rGO-MoO3 nano-composite (FGM) with nanoparticles-like morphology (NPs) by utilizing the fast and facile microwave hydrothermal process. The optimized composition of FGM nanocomposite is characterized by the XPS, EDS, Raman, SEM, TEM and HRTEM techniques. The FGM-NPs supported on the carbon cloth (FGM@CC) electrode is used to investigate the electrochemical charge storage properties in basic potassium hydroxide (KOH) electrolyte. The charge-storage properties of the FGM@CC electrode were studied by the CV, GCD and EIS techniques. The obtained results of FGM@CC electrode in aqueous electrolyte showed excellent electrochemical performance as compared with single metal oxides: maximum specific capacitance of 1666.50 F g−1 (FGM@CC), 1075.26 F g−1 (Fe3O4 NPs) and 952.38 F g−1 (MoO3 NPs) at a current density of 2.5 A g−1. The capacitance retention was 95.01% (FGM@CC), 94.1% (Fe3O4 NPs) and 92.5% (MoO3 NPs) after 5000 cycles. Further, the charge storage mechanism is analyzed in the light of power's law and systematical investigated the capacitive and diffusion controlled based stored charge in FGM@CC electrode. Thus FGM nano-composite showed best performance as the cathode material for the next generation flexible supercapacitors.

Chemically Bonding NiFe-LDH Nanosheets on rGO for Superior Lithium-Ion Capacitors.

Layered double hydroxides (LDHs) have attracted tremendous interest for applications in energy harvest and storage. However, the aggregation of nanosheets compromises the accessible active sites and limits their electrochemical performance, especially at high rates. The present study reports the synthesis of highly dispersed NiFe-LDH nanosheets anchored on reduced graphene oxide (NiFe-LDH/rGO) composites chemically bonded via a facile one-step hydrothermal method. Defect-riched rGO provides abundant active sites for heterogeneous nucleation of NiFe-LDH nanosheets, achieving the much efficient charge transfer between rGO and NiFe-LDH as compared to physically mixed NiFe-LDH + rGO. The crystallite size can effectively reduce to 5.5 nm smaller than 15.1 nm of NiFe-LDH without rGO, beneficial to expose more active surface for fast ion diffusion and redox reactions. NiFe-LDH/rGO as an anode material in lithium-ion batteries shows superior lithium storage capacity with 1202 mAh g-1 after 100 cycles at 100 mA g-1 and high-rate performance with 543 mAh g-1 even at 2000 mA g-1. The corresponding lithium-ion capacitor with NiFe-LDH/rGO anode and mesoporous carbon microsphere cathode exhibits high energy density and power density simultaneously, with 133 Wh kg-1 at 25 W kg-1 and 4016 W kg-1 at 58 Wh kg-1, showing the great potential for high-performance hybrid energy storage systems.

Quadruple thiophene based electrochromic electrodeposited film as high performance hybrid energy storage system

Conducting polymers are considered as an attractive option for energy storage system. In this paper, a unique quadruple thiophene-based polythiophene derivative (pPHBT) film was prepared through the electrochemical deposition from a star-shaped tri(bithiophene)benzene (PHBT). The electrodeposited pPHBT film may possess the microporous structure owing to the effective polymerization of star-shaped PHBT monomer. Also, the electrochemical, UV-vis and theoretical characterization of pPHBT film show that the oxidation reaction for this film should occur on the quadruple thiophene units. The unique structure of pPHBT may enable it with interesting electrochromic and energy storage properties. The pPHBT film shows the multicolor electrochromic character from yellow to green, and finally to blue color. The charging/discharging curves show that pPHBT film exhibits a high capacity of 96.7 mAh g−1, which is viewed as a high value among the reported p-doped conducting polymer energy storage materials. Besides, the pPHBT film shows more symmetrical charging-discharging curves and relatively better cycling stability than the linear-structure poly(bithiophene) film. The combination of these fascinating properties results in an intelligent energy storage device changes its color based on its charged state so that the state of charge can be monitored by simple visual inspection.

Performance Evaluation of a MW-Class SMES-BES DVR System for Mitigation of Voltage Quality Disturbances

Performance evaluations of a MW-class dynamic voltage restorer (DVR) system are presented for mitigation of voltage quality disturbances. A presag compensation strategy is introduced to lock the instantaneous magnitudes and phase angles of real-time line voltages, and thus to compensate the improper voltage components exactly after symmetrical or asymmetrical voltage disturbances. A 0.3-H/1.76-kA superconducting magnetic energy storage (SMES) magnet is used to cooperate with conventional battery energy storage (BES) device for developing a high-performance hybrid energy storage (HES) system. In the SMES-BES HES-based DVR system, the SMES can compensate the worst voltage sag for five cycles (1 MW, 100 ms, and absorb the highest voltage swell for six cycles (1 MW, 120 ms). The accessorial high-capacity BES device is subsequently discharged or charged for lasting long-time mitigation operations. Various simulation cases with regard to combined voltage sag, swell, and harmonic disturbances are carried out. The simulations and comparisons among the SMES-based, BES-based, and HES-based DVR schemes have demonstrated that the HES-based DVR scheme integrates the merits of fast response speed and high-power density from the SMES-based scheme, and the merits of low capital cost and high-energy density from the BES-based scheme.

Porous NiCoMn ternary metal oxide/graphene nanocomposites for high performance hybrid energy storage devices

Mixed transition metal oxides have attracted great attention due to their improved properties over simple oxides in energy storage applications. Herein, we report facile hydrothermal synthesis of novel porous NiCoMn ternary metal oxide flakes with reduced graphene oxide (NCMO_rGO) and their application in high performance aqueous-based energy storage devices. The effect of reaction time on composition and morphology was studied by X-ray diffraction, Raman spectroscopy, thermal gravimetric analysis, transmission electron microscopy, and N2 ad/de-sorption measurements. Accordingly, a high specific surface area of 200 m2 g−1 was achieved for the optimized sample. The sample was electrochemically investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. Porous NCMO_rGO hybrid exhibited a high capacity of 115 mAh·g−1 at 1 A g−1. Subsequent integration of the hybrid material as a positive electrode with rGO negative electrodes resulted in asymmetric aqueous devices having a specific energy as high as 27 Wh·kg−1. Moreover, this NCMO_rGO//rGO hybrid device showed an excellent cycling stability of 96% over 2000 cycles. This work not only reports for the first time the rational design and fabrication of porous NCMO_rGO nanoflakes as high performance electrodes for energy storage but also paves the path towards facile synthesis of mixed metal oxide nanocomposites for other applications.

CoO nanoparticles deposited on 3D macroporous ozonized RGO networks for high rate capability and ultralong cyclability of pseudocapacitors

The integration of pseudocapacitive metal oxides with reduced graphene oxide (RGO) is considered an innovative chemical strategy to resolve both bottlenecks of pseudocapacitor and electrical double-layer capacitor for high performance supercapacitors. Herein, we report a facile synthesis method of highly porous three-dimensional (3D) CoO/RGO nanocomposite via ozone treatment, ice templating, and thermal annealing. The ozonized RGO surface provides a favorable interaction with cobalt precursor for a stable and uniform deposition of well-defined CoO nanoparticles. The morphology, structure, and chemistry of the resulting CoO/RGO nanocomposites are comprehensively characterized by spectroscopic methods. The CoO/RGO nanocomposites show fast and reversible pseudocapacitance due to a large accessible area, rapid ion transport, and low charge transfer resistance arising from 3D internetworked macroporosity. Thus, the nanocomposites achieve high specific capacitance up to 239.4Fg-1 (volumetric capacitance = 12.04Fcm-3), excellent rate capability of 79.1%, and ultralong cyclic stabilities (of 93.2% at 10Ag-1 even up to 10,000 cycles) in 6M KOH electrolyte. This simple synthesis method offers a promising solution for the design of high performance hybrid energy storage materials consisting of high capacity metal oxides and conductive graphene networks.

Nanostructured porous wires of iron cobaltite: novel positive electrode for high-performance hybrid energy storage devices

Nanostructured porous wires of FeCo2O4supported on nickel foam were synthesized and employed as binder/additive-free electrodes in asymmetric aqueous supercapacitors, showing a high energy density of 23 Wh kg−1.