Charge Storage Efficiency Research Articles

Preinserted Ammonium in MnO2 to Enhance Charge Storage in Dimethyl Sulfoxide Based Zinc-Ion Batteries.

Nonaqueous zinc-ion batteries (NZIBs) featuring manganese dioxide (MnO2) cathodes position themselves as viable options for large-scale energy storage systems. Herein, we demonstrate the use of ammonium cation as a preintercalant to improve the performance of the δ-MnO2 cathode in wet dimethyl sulfoxide based electrolytes. Employing in situ X-ray absorption spectroscopy, Raman spectroscopy, and synchrotron X-ray diffraction, we reveal that the integration of ammonium cations promotes the formation of NH-O-Mn networks. These networks are crucial for manipulating the distortion of the MnO6 octahedral units during discharging, thereby mitigating charge disproportionation, which is a primary limitation to MnO2's charge-storage efficiency. The modified MnO2, through this idea, displays a notable improvement in capacity (∼247 mAh/g) and can pass charge-discharge cycles up to 500 cycles with a capacity retention of 85%. These findings underscore the potential of modified MnO2 in advancing MnO2-based hosts for Zn-MnO2 batteries, marking significant progress toward next-generation energy storage solutions.

Nitrogen and phosphorus enriched nanoporous carbonaceous material for gas sorption and supercapacitor applications

Nitrogen and phosphorous-enriched heteroatoms-based nanoporous carbonaceous material (designated as HPHMC900) possesses a high surface area of 1668 m2 g−1 was synthesized. HPHMC900 captures 5.6 and 3 mmol g−1 of CO2 and CH4 at 273 K and 1 bar, respectively. Further, the material has 11.95 mmol g−1 of H2 adsorption capability at 77 K and 1 bar. HPHMC900 has been investigated for supercapacitor application. Further, a symmetric supercapacitor device (SSD) fabricated using the HPHMC900, has a specific capacitance (Csp) of 233 F g−1, energy (E) of 46.6 Wh kg−1, and power (P) of 289 W kg−1, respectively. The high Csp and high energy were achieved at low-concentrated aqueous electrolyte (0.5 M KOH), without using any redox-active agents. Further, it shows 100 % coulombic efficiency and initial capacitance retention (94.9 %) after 10,000 cycles. This research elucidates the correlation between high surface area and heteroatom enrichment with enhanced charge storage and gas adsorption efficiency.

Improving the electro-optical properties of MoS2/rGO hybrid nanocomposites using liquid crystals

Hybrid systems of two-dimensional (2D) materials (such as graphene-family materials and 2D transition metal dichalcogenides) are attracting much attention due to their distinctive optoelectronic, thermal, mechanical, and chemical properties. The application perspectives of these materials in various fields further expand when enriching those with liquid crystals (LCs) primarily due to their enhanced tunability and functionality. In this study, we report on the hydrothermal synthesis of hybrid nanocomposites composed of MoS2 and rGO and discuss tuning possibilities of their electro-optical properties by incorporating thermotropic LCs. In particular, we demonstrate that the incorporation of 5CB LC increases the sensitivity and charge storage efficiency of the hybrid nanocomposites. In addition, we also present the responsivity, detectivity, and response time properties of the hybrid nanocomposites of MoS2/rGO, both with and without the inclusion of nematic LCs. Furthermore, we demonstrate that the system exhibits a 5CB-induced photocurrent switching effect. We believe the findings will open new doors for applications of these materials in optoelectronics and photonics.

Molybdenum Sulfide Nanoflowers as Electrodes for Efficient and Scalable Lithium-Ion Capacitors.

Hybrid supercapacitors (HSCs) bridge the unique advantages of batteries and capacitors and are considered promising energy storage devices for hybrid vehicles and other electronic gadgets. Lithium-ion capacitors (LICs) have attained particular interest due to their higher energy and power density than traditional supercapacitor devices. The limited voltage window and the deterioration of anode materials upsurged the demand for efficient and stable electrode materials. Two-dimensional (2D) molybdenum sulfide (MoS2) is a promising candidate for developing efficient and durable LICs due to its wide lithiation potential and unique layer structure, enhancing charge storage efficiency. Modifying the extrinsic features, such as the dimensions and shape at the nanoscale, serves as a potential path to overcome the sluggish kinetics observed in the LICs. Herein, the MoS2 nanoflowers have been synthesized through a hydrothermal route. The developed LIC exhibited a specific capacitance of 202.4 F g-1 at 0.25 A g-1 and capacitance retention of >90 % over 5,000 cycles. Using an ether electrolyte improved the voltage window (2.0 V) and enhanced the stability performance. The ex-situ material characterization after the stability test reveals that the storage mechanism in MoS2-LICs is not diffusion-controlled. Instead, the fast surface redox reactions, especially intercalation/deintercalation of ions, are more prominent for charge storage.

Zn-Doped MnO2 microflake pseudocapacitive cathode on Ni(OH)2/Ni-Foam substrate as a promising charge storage material

Zn-doped MnO2 microflakes cathode material on Ni(OH)2/Ni foam has been synthesized and characterized as well as tested its electrochemical performances in 3 M KOH solution. The present work varies the amounts of Zn dopant in MnO2 system to improve its capability in energy storage. Material identification has been simply confirmed with XRD, SEM, TEM, and XPS analysis. It is expected the Zn dopant will induce surface defects such as ZnMn2- or ZnMn0 and oxygen vacancy, leading to enhanced charge storage efficiency. In addition, XPS analysis reveals the existence of positively charged oxygen vacancy and the surface charge of ZnMn2- or ZnMn0 induce different surface oxidation states of Mn2+ and Mn4+. The oxidation states of Mn could accommodate the redox reactions involving ion adsorption and intercalation during pseudocapacitive charge and discharge processes. Substituting Zn into Mn sites is optimized with MnZn-1.5 which reaches a specific capacitance of 1601F/g at a 0.4 VAg/AgCl in KOH solution. This work demonstrates a promising material system for supercapacitor applications using Zn doping with a simple preparation process to support a large-scale application.

Elucidating the Energy Storage Performance of 2D Metallic Vanadium Ditelluride/Carbon Nanotube for Next‐Generation Asymmetric Supercapacitors Using Emerging MoSSe/Carbon Nanotube

Recently, vanadium ditelluride (VTe2) a member of the transition metal ditellurdies family has emerged as a functional material for energy storage applications owing to its exotic intrinsic properties. Similar to most of the nanostructured materials, a hybrid structure of VTe2 is expected to provide enhanced energy storage capability. Herein, two hybrid structures of VTe2 are engineered using well‐explored nanocarbons such as RGO and carbon nanotube (CNT) to create a compelling supercapacitor electrode material. Both the hybrid structures show improved electrochemical activity, but VTe2/CNT fared better in the charge storage efficiency. The enhanced active sites, short ionic/electronic pathways provided by the CNT network, and the large electric double‐layer contribution have synergized for the inflated capacitance of VTe2/CNT. Further, a high‐performance asymmetric supercapacitor (ASC) of VTe2/CNT//MoSSe/CNT is constructed in a typical Swagelok cell, and the ASC delivered an energy density output of 36.28 Wh kg−1 at a power density of 463.16 W kg−1 with a remarkable 80.26% capacitance retention. The results of this work suggest that VTe2/CNT is a promising contender in the pantheon of functional materials for energy storage applications in the near future.

Interlayer Nano-Dots Induced High-Rate Supercapacitors.

The fast OH- transfer between hydroxide layers is the key to enhancing the charge storage efficiency of layered double hydroxides (LDH)-based supercapacitors (SCs). Constructing interlayer reactive sites in LDH is much expected but still a huge challenge. In this work, CdS nano-dots (NDs) are introduced to interlayers of ultra-thin NiFe-LDH (denoted CdSinter. -NiFe-LDH), promoting the interlayer ions flow for higher redox activity. The excellent performance is not only due to the enlarged layer spacing (from 0.70 to 0.81nm) but also stems from anchored interlayer reactive units and the undamaged original layered structure of LDH, which contribute to the improvement of OH- diffusion coefficient (1.6×10-8 cm2 s-1 ) and electrochemical active area (601mFcm-2 ) better than that of CdS NDs on the surface of NiFe-LDH (2.1×10-9 cm2 s-1 and 350mFcm-2 ). The champion CdSinter. -NiFe-LDH electrode displays high capacitance of 3330.0Fg-1 at 1Ag-1 and excellent retention capacitance of 90.9% at 10Ag-1 , which is better than the NiFe-LDH with CdS NDs on the surface (1966.6Fg-1 ). Moreover, the assembled asymmetric SCs (ASC)device demonstrate an outstanding energy density/power density (121.56Whkg-1 /754.5Wkg-1 ).

Collective behavior of boreholes and its optimization to maximize BTES performance

Borehole layout strongly affects the behavior of borehole heat exchangers (BHEs) and changes the performance of a borehole thermal energy storage (BTES). This study investigates the existence and importance of the optimum collective behavior of BHEs to maximize the performance of BTES. Charge benefit ratio, storage efficiency and configurational benefit factor are proposed as performance indicators for better and finer performance evaluations of BTES systems. A small-scale BTES consisting of ten boreholes arranged on a concentric double-ring layout is considered as an application. Performance variations with the inner and the outer radii of the borehole field are analyzed for the first five years of operation. The temperature fields of different configurations show the transition from collective to individual behavior of boreholes, which leads to an optimal radial configuration maximizing the performance indicators. It is seen that the indicators strongly depend on both inner and outer radii and they reach their maximums for the same distinct radial configuration. The optimum arrangement can almost double the thermal performance indicators. It is thus of great importance to optimize collective behavior to maximize the usage of stored thermal energy. The results are qualitatively general and represent the common behavioral patterns of BTES systems.

Hierarchical MnO2/NiS–MnS with Rich Electro-Microstructural Physiognomies for Highly Efficient All-Solid-State Hybrid Supercapacitors

To revolutionize the charge storage efficiency of electrode materials for their utilizations in high Ragone efficient electrochemical energy storage devices, herein, a slow-precipitation-induced material growth approach has been innovated to design a hetero oxide–sulfide [MnO2/NiS–MnS (MnO2/Ni–Mn–S)] material with smaller crystallite size, ultrathin assembled-sheet-like microstructure, and perceptible phase physiognomies (α-MnO2, MnS, and α-NiS). The electroredox assessment of MnO2/Ni–Mn–S illustrates high pseudocapacitive energy storage efficiency, significant redox reversibility, lowly constrained bulk accessibility of the OH– ions at higher rate electrochemical reaction conditions, dominance of semi-infinite diffusion-controlled electrochemical processes, and extremely low charge-transfer resistance (∼1.45 Ω), total series resistance (∼0.51 Ω) and diffusion (Warburg) resistance. A fabricated 1.8 V MnO2/Ni–Mn–S||nitrogen-doped reduced graphene oxide (N-rGO) all-solid-state hybrid supercapacitor (ASSHSC) device with N-rGO as the negative electrode material delivers high area and mass specific capacitance/capacity, ∼100% Columbic efficiency at high-rate operating conditions, and very low charge-transfer and Warburg resistance. The MnO2/Ni–Mn–S||N-rGO ASSHSC device also delivers excellent Ragone efficiency (ED = 31.5 W h kg–1 at PD = 937.5 W kg–1 and ED = 15.5 W h kg–1 at PD = 2767.5 W kg–1) and ∼97.6% retention of charge storage after 11,000 uninterrupted charge–discharge cycles. The significantly improved supercapacitive charge storage efficacy of MnO2/Ni–Mn–S is ascribed to the cohesive redox activity of Ni2+, Ni3+, Mn2+, and Mn3+ and nonstoichiometric Ni2±δ, Ni3±δ, Mn2±δ, and Mn3±δ ions, rich ion-disseminating bulk, S2– vacancy-induced electronic conductivity, and suitable electro-microstructural physiognomies for the electrochemical processes.

Zinc-Catalyzed Two-Electron Nickel(IV/II) Redox Couple for Multi-Electron Storage in Redox Flow Batteries.

Energy storage is a vital aspect for the successful implementation of renewable energy resources on a global scale. Herein, we investigated the redox cycle of nickel(II) bis(diethyldithiocarbamate), NiII(dtc)2, for potential use as a multielectron storage catholyte in nonaqueous redox flow batteries (RFBs). Previous studies have shown that the unique redox cycle of NiII(dtc)2 offers 2e- chemistry upon oxidation from NiII → NiIV but 1e- chemistry upon reduction from NiIV → NiIII → NiII. Electrochemical experiments presented here show that the addition of as little as 10 mol % ZnII(ClO4)2 to the electrolyte consolidates the two 1e- reduction peaks into a single 2e- reduction where [NiIV(dtc)3]+ is reduced directly to NiII(dtc)2. This catalytic enhancement is believed to be due to ZnII removal of a dtc- ligand from a NiIII(dtc)3 intermediate, resulting in more facile reduction to NiII(dtc)2. The addition of ZnII also improves the 2e- oxidation, shifting the anodic peak negative and decreasing the 2e- peak separation. H-cell cycling experiments showed that 97% Coulombic efficiency and 98% charge storage efficiency was maintained for 50 cycles over 25 h using 0.1 M ZnII(ClO4)2 as the supporting electrolyte. If ZnII(ClO4)2 was replaced with TBAPF6 in the electrolyte, the Coulombic efficiency fell to 78%. The use of ZnII to increase the reversibility of 2e- transfer is a promising result that points to the ability to use nickel dithiocarbonates for multielectron storage in RFBs.

Boosting zinc-ion storage capability by engineering hierarchically porous nitrogen-doped carbon nanocage framework

In virtue of combining superb power of supercapacitors and high energy of batteries, zinc-ion hybrid supercapacitors become a competitive candidate in current energy storage systems. However, the cell chemistry related to carbon cathode still suffers from the obstacles of reaction kinetics and charge storage efficiency. Herein, a three-dimensional framework of N-doped carbon nanocages is constructed through pyrolyzing and activating polypyrrole on the platform of ZIF-8, synchronously achieving hierarchical porosity and high N-doping content. Thanks to the comprehensive modulation of the morphology, pore structure, and surface chemistry, the obtained carbon shows the significant enhancement in active site exposure and diffusion kinetics. Therefore, the zinc-ion hybrid supercapacitor using this carbon cathode achieves the remarkably improved Zn-ion storage capability (124 mAh g−1 at 0.25 A g−1 with a 65.9% capacity retention at 20 A g−1, and nearly no capacity decay after 10000 cycles at 10 A g−1). Moreover, this device exhibits superior energy/power densities of 107.3 Wh kg−1/16647.7 W kg−1, together with a low self-discharge rate of 3 mV h−1. Our work presents a good design strategy to develop advanced carbon-based cathodes to accelerate the development of Zn-based devices.

Ultrathin Carbon Deficient Molybdenum Carbide (α-MoC1-x) Enables High-Rate Mg-Ion-based Energy Storage.

Dual-electron transfer with Mg2+-ion intercalation outperforms typical alkali metal-ion (Li+, Na+, K+) systems with superior charge storage efficiency while the neutral electrolytes can achieve a working voltage beyond the hydrolysis window of 1.23 V. Hence, aqueous Mg-ion electrolytes are promising for electrochemical energy storage devices to boost the energy density and solve the safety challenges synchronously. However, the Mg-based electrochemical energy storage (EES) devices are generally confined by poor rate performance due to the slow Mg2+ diffusion in the electrode materials. In this paper, we demonstrate that carbon-deficient carbide could function as a promising electrode material in Mg2+-ion-based EES. An electrode made of such carbide can operate over an extended window up to 2.4 V in 1 M magnesium acetate, showing superior performance of high capacitance (125.2 F/g), high energy density (25.1 Wh/kg), and high power density (3934.8 W/kg). Ab initio simulation reveals migration energy of Mg2+ being lower than that of Li+ diffusing from one carbon defect to another in the α-MoC1-x lattice, supporting the experimental results that a symmetric supercapacitor made of α-MoC1-x in an electrolyte based on Mg2+ outperforms electrolytes based on Li+.

Investigation of Electrochemical Charge Storage Efficiency of NiCo2Se4/RGO Composites Derived at Varied Duration and Its Asymmetric Supercapacitor Device

Morphology and crystalline structure of electrode materials control the capacitive properties of a supercapacitor device. Among the commonly studied electrode materials, Ni-Co based bi-metallic sel...

3D-heterostructured NiO nanofibers/ultrathin g-C3N4 holey nanosheets: An advanced electrode material for all-solid-state asymmetric supercapacitors with multi-fold enhanced energy density

Herein, we report a modified polyol condensation based synthesis of highly-hydrophilic, lowly-crystalline and holey-ultrathin g-C3N4 (GCN) nanosheets, which are further used as the conducting matrix to interfacially grow NiO nanofibers. The physicochemical studies show restricted crystal growth of NiO on GCN, ultra-dispersive nature of NiO/GCN heteronanocomposite in water, and chemical interaction between NiO and GCN. Thorough electrochemical analyses in 3-electrode setup confirm lower equivalent series resistance, charge transfer resistance and diffusion resistance of NiO/GCN heteronanocomposite as compared to pristine NiO. The NiO/GCN heteronanocomposite offers ~2 times more specific capacitance and higher rate capacitance as compared to the pristine NiO. Further, 1.8 V all-solid-state asymmetric supercapacitor (ASSASC) devices are fabricated by using NiO/GCN heteronanocomposite and pristine NiO as the positive electrode materials, and N-rGO as the negative electrode material, and the supercapacitive charge storage efficiencies of the devices are systematically compared. Results show that, the respective mass-specific capacitance and rate capacitance offered by NiO/GCN||N-rGO is ~2 and ~3 times more than that offered by pristine-NiO||N-rGO ASSASC device. The NiO/GCN||N-rGO also offers ~2.7 and ~6 times more energy densities at respective power densities of ~3200 and ~6900 W kg–1, over pristine-NiO||N-rGO ASSASC device. Further, the NiO/GCN||N-rGO retains ~13% more specific capacitance as compare to the pristine-NiO||N-rGO ASSASC device, after 6000 charge-discharge cycles. The largely improved supercapacitive charge storage efficiency of NiO/GCN heteronanocomposite is ascribed to GCN-prompted surface functionality, lowly-impeded electron transport, and greater electrolyte access to the majority of redox-active sites, during high-rate supercapacitive charge storage process.

Synthesis of Ce-V-Mo Oxide Nanocomposite for High Performance All Solid State Asymmetric Supercapacitors (ASSASs)

The depletion of non-renewable resources has prompted the continuous development of various energy storage systems to manage the world’s increasing demand for energy. Among the well-known energy storage systems, supercapacitors (SCs) exhibit superior performance because they can store more energy than conventional capacitors and have a higher power density than batteries. In this context, we have strategically synthesized ternary Ce-V-Mo oxide (CVMO) nanocomposite and directly utilized it in all solid state supercapacitor device. The phase purity, element composition and surface morphology were characterized by PXRD, EDS, FESEM, HRTEM and XPS measurements. The pseudocapacitive charge storage efficiency of CVMO was thoroughly studied by CV, GCD and EIS measurements. The CVMO offers a specific capacitance value of 5484 F g–1 at scan rate of 5 mV s–1 and 4330 F g–1 at a current density 4 Ag–1. The CVMO also retains ~87% of specific capacitance at a high current density of 20 A g–1. The EIS study shows low solution and charge transfer resistance of CVMO. An ASSAS device fabricated using N-rGO as the negative electrode material shows high rate capacitance, and superior energy density at elevated power density condition. The results presented here is significant in the context of developing high performance ASSASC devices for numerous technological viability.1-5

Graphene based ceria nanocomposite synthesized by hydrothermal method for enhanced supercapacitor performance

Reduced graphene oxide – cerium oxide (rGO-CeO2) nanocomposite is prepared by simple hydrothermal method for enhanced charge storage supercapacitor performance. The prepared nanocomposite is characterized by various techniques, such as X-ray diffraction (XRD), Fourier Transform – Raman Spectra (FT-Raman), Field Emission - Scanning Electron Microscope (FE-SEM), High Resolution –Transmission Electron Microscope (HR-TEM), Thermo-gravimetric and Differential Thermal Analysis (TG-DTA), Cyclic Voltametric (CV), Galvanostatic Charge/Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) studies to understand its morphology, composition, thermal stability and charge storage efficiency as electrode material. The nanocomposite formation is confirmed with FE-SEM and HR-TEM images where the ceria is anchored on the surface of the graphene sheets and the interplanar distances are observed as fringes. The Energy Dispersive Analysis of X-Ray (EDAX) has provided substantial evidence for the nanocomposite formation with the elemental composition. The maximum specific capacitance is measured as 280 F/g using GCD studies. The surface area of the nanocomposite is determined using the Brunauer-Emmett-Teller (BET) analysis.

Sedgelike Porous Co3O4 Nanoarrays as a Novel Positive Electrode Material for Co3O4 || Bi2O3 Asymmetric Supercapacitors

Tuning crystallinity and surface functionality are supreme for extracting maximum charge storage efficiency from electrode materials for energy storage devices. Contextually, suitable organic addit...

Hysteresis analysis in dye-sensitized solar cell based on different metal alkali cations in the electrolyte

Hysteresis phenomenon occurs in solar cells and its cause is still an arguable issue as it redefines how accurately we control the device performance. Here, the hysteresis behavior in Dye-sensitized solar cell (DSSC) is studied based on the electrolyte. Three electrolytes were used containing Sodium iodide (NaI), Potassium iodide (KI), and Cesium iodide (CsI). Current density-voltage characteristics was measured for each device at fast (1 V/s) scan rate, medium (0.5 V/s) scan rate, and slow (0.1 V/s) scan rate. The charging-discharging process at TiO2/electrolyte interface during forward and reverse scan directions is propose as the responsible mechanism for hysteresis in DSSC. Based on our investigation, hysteresis phenomenon is strongly dependent on the size of alkali metal cation as well as J-V sweep scan rate. Hysteresis is dominant for NaI electrolyte with the smallest Na+ cation size while it diminishes for KI and CsI electrolytes with bigger K+ and Cs+ sizes, respectively. Also, using CsI electrolyte along with the slow scan rate of 0.1 V/s is the perfect combination for the minimal hysteresis in the solar cell. In addition, hysteresis index calculation was redefined based on the intercept cross points between forward and reverse scan directions. Our results suggest that DSSC has a charge storage efficiency accompanied by its primary function as a power conversion device. The charge storage ability occurs for V > VOC during the forward scan and it is significant for smaller cation size.

A Porous and Conductive Graphite Nanonetwork Forming on the Surface of KCu7S4 for Energy Storage

A flexible all-solid-state supercapacitor is fabricated by building a layer of porous and conductive nanonetwork on the surface of KCu7S4 nanowires supported on the carbon fiber fabric, where the porous and conductive nanonetwork is assembled by graphite nanoparticles. This porous graphite layer plays a key role in providing ion diffusion channels to access the KCu7S4 through the pores for electrochemical reactions and forming electron transport pathways from the graphite network to the electronic collector of the carbon fiber fabric. This flexible supercapacitor exhibits excellent electrochemical performance with high specific capacitance of 408 F g−1 at a current density of 0.5 A g−1 and high energy density of 36 Wh kg−1 at a power density of 201 W kg−1. Moreover, it is cost-effective, easy to scale up and environmentally friendly with high flexibility. Our investigation demonstrates that such a porous and conductive nanonetwork could be used to improve the charge storage efficiency for a wide range of electrode materials.

One-dimensional array of gold nanoparticles fabricated using biotemplate and its application to fine FET

By synthesizing AuS nanoparticles (NPs) with spherical shell protein (ferritin) and using a V-groove, a one-dimensional array of NPs was formed at the bottom of the V-groove. It has been reported that AuS NPs are converted to Au NPs by UV/ozone treatment. Floating gate memory (FGM) was fabricated by applying this one-dimensional array to V-grooved junctionless (JL) FETs, V-grooved nin-like-type FETs, and pip-like-type FETs, which are fine FETs. In JL-FETs, it is considered that conversion occurred because of good charge storage efficiency, and operation in the opposite direction to normal FGM operation was seen. In the nin-like and pip-like types devices, the same operation as in conventional FGM was shown, and the width of the memory window was about the same size as when one electron entered one NP. The one-dimensional arrangement of the metal NPs used in this study is considered to be applicable to various fields of nanotechnology.