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Special Issue "Advances in Electrochemical Energy Storage Devices"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Electrochemistry".

Deadline for manuscript submissions: closed (30 September 2019).

Special Issue Editor

Prof. Dr. Amor M. Abdelkader
E-Mail Website1 Website2
Guest Editor
1. Associate Professor of Advanced Materials, Head of Research & Professional Practice, Department of Design and Engineering, Faculty of Science and Technology, Bournemouth University, C226, Christchurch House, Talbot Campus, Fern Barrow, Poole, Dorset, BH12 5BB, UK 2. Visitor Academic, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK
Interests: rechargeable batteries; supercapacitors; nanomaterials; energy materials; electrochemical CO2 sequestration
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

There is a growing interest in electrochemical energy storage devices to empower portable electronics, electric vehicles and to fulfil the need for the large-scale storage of stationary applications. Despite significant research efforts in recent years, there remain key challenges to be overcome in the near future. These include improvements to storage energy density and power density, conversion efficiency, cost, cycle life, battery weight and volume, and battery safety.

Chemical and conceptual developments are progressing, with electrolytes, packaging materials, and electrode materials and structures also advancing. There has been a simultaneous focus on the development of flexible energy storage devices, motivated by the rise of wearable electronics. Furthermore, theoretical and experimental studies are seeking to understand the fundamentals of physicochemical processes, including electronic and ionic transport in electrodes, electrolyte phases and stability, electrochemical reactions, material phase changes, and mechanical and thermal stresses.

This Special Issue focuses on recent advancements in electrochemical energy storage technology, encompassing supercapacitors, primary batteries and rechargeable batteries. Contributions of both original articles and comprehensive reviews, will cover the latest developments in device architecture, electrode design and materials, thermal and mechanical stress management, large-scale devices, and energy device manufacturing processes.

Assoc. Prof. Dr. Amor M. Abdelkader
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Primary batteries
  • Rechargeable batteries
  • Supercapacitors
  • Hybrid electrochemical energy storage

Published Papers (8 papers)

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Open AccessFeature PaperArticle
Electrocatalytic Assisted Performance Enhancement for the Na-S Battery in Nitrogen-Doped Carbon Nanospheres Loaded with Fe
Molecules 2020, 25(7), 1585; https://doi.org/10.3390/molecules25071585 - 30 Mar 2020
Cited by 3 | Viewed by 1045
Abstract
Room temperature sodium-sulfur batteries have been considered to be potential candidates for future energy storage devices because of their low cost, abundance, and high performance. The sluggish sulfur reaction and the “shuttle effect” are among the main problems that hinder the commercial utilization [...] Read more.
Room temperature sodium-sulfur batteries have been considered to be potential candidates for future energy storage devices because of their low cost, abundance, and high performance. The sluggish sulfur reaction and the “shuttle effect” are among the main problems that hinder the commercial utilization of room temperature sodium-sulfur batteries. In this study, the performance of a hybrid that was based on nitrogen (N)-doped carbon nanospheres loaded with a meagre amount of Fe ions (0.14 at.%) was investigated in the sodium-sulfur battery. The Fe ions accelerated the conversion of polysulfides and provided a stronger interaction with soluble polysulfides. The Fe-carbon nanospheres hybrid delivered a reversible capacity of 359 mAh·g−1 at a current density of 0.1 A·g−1 and retained a capacity of 180 mAh·g−1 at 1 A·g−1, after 200 cycles. These results, combined with the excellent rate performance, suggest that Fe ions, even at low loading, are able to improve the electrocatalytic effect of carbon nanostructures significantly. In addition to Na-S batteries, the new hybrid is anticipated to be a strong candidate for other energy storage and conversion applications such as other metal-sulfur batteries and metal-air batteries. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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Open AccessFeature PaperEditor’s ChoiceArticle
Enhanced Reactant Distribution in Redox Flow Cells
Molecules 2019, 24(21), 3877; https://doi.org/10.3390/molecules24213877 - 28 Oct 2019
Cited by 3 | Viewed by 1405
Abstract
Redox flow batteries (RFBs), provide a safe and cost-effective means of storing energy at grid-scale, and will play an important role in the decarbonization of global electricity networks. Several approaches have been explored to improve their efficiency and power density, and recently, cell [...] Read more.
Redox flow batteries (RFBs), provide a safe and cost-effective means of storing energy at grid-scale, and will play an important role in the decarbonization of global electricity networks. Several approaches have been explored to improve their efficiency and power density, and recently, cell geometry modification has shown promise in efforts to address mass transport limitations which affect electrochemical and overall system performance. Flow-by electrode configurations have demonstrated significant power density improvements in laboratory testing, however, flow-through designs with conductive felt remain the standard at commercial scale. Concentration gradients exist within these cells, limiting their performance. A new concept of redistributing reactants within the flow frame is introduced in this paper. This research shows a 60% improvement in minimum V3+ concentration within simulated vanadium redox flow battery (VRB/VRFB) cells through the application of static mixers. The enhanced reactant distribution showed a cell voltage improvement by reducing concentration overpotential, suggesting a pathway forward to increase limiting current density and cycle efficiencies in RFBs. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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Open AccessArticle
Structural, Impedance, and EDLC Characteristics of Proton Conducting Chitosan-Based Polymer Blend Electrolytes with High Electrochemical Stability
Molecules 2019, 24(19), 3508; https://doi.org/10.3390/molecules24193508 - 27 Sep 2019
Cited by 29 | Viewed by 1154
Abstract
In this report, a facile solution casting technique was used to fabricate polymer blend electrolytes of chitosan (CS):poly (ethylene oxide) (PEO):NH4SCN with high electrochemical stability (2.43V). Fourier transform infrared (FTIR) spectroscopy was used to investigate the polymer electrolyte formation. For the electrochemical property [...] Read more.
In this report, a facile solution casting technique was used to fabricate polymer blend electrolytes of chitosan (CS):poly (ethylene oxide) (PEO):NH4SCN with high electrochemical stability (2.43V). Fourier transform infrared (FTIR) spectroscopy was used to investigate the polymer electrolyte formation. For the electrochemical property analysis, cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) techniques were carried out. Referring to the FTIR spectra, a complex formation between the added salt and CS:PEO was deduced by considering the decreasing and shifting of FTIR bands intensity in terms of functional groups. The CS:PEO:NH4SCN electrolyte was found to be electrochemically stable as the applied voltage linearly swept up to 2.43V. The cyclic voltammogram has presented a wide potential window without showing any sign of redox peaks on the electrode surface. The proved mechanisms of charge storage in these fabricated systems were found to be double layer charging. The EIS analysis showed the existence of bulk resistance, wherein the semicircle diameter decreased with increasing salt concentration. The calculated maximum DC conductivity value was observed to be 2.11 × 10−4 S/cm for CS:PEO incorporated with 40 wt% of NH4SCN salt. The charged species in CS:PEO:NH4SCN electrolytes were considered to be predominantly ionic in nature. This was verified from transference number analysis (TNM), in which ion and electron transference numbers were found to be tion = 0.954 and tel = 0.045, respectively. The results obtained for both ion transference number and DC conductivity implied the possibility of fabricating electrolytes for electrochemical double layer capacitor (EDLC) device application. The specific capacitance of the fabricated EDLC was obtained from the area under the curve of the CV plot. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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Open AccessEditor’s ChoiceArticle
A Promising Polymer Blend Electrolytes Based on Chitosan: Methyl Cellulose for EDLC Application with High Specific Capacitance and Energy Density
Molecules 2019, 24(13), 2503; https://doi.org/10.3390/molecules24132503 - 09 Jul 2019
Cited by 49 | Viewed by 1638
Abstract
In the present work, promising proton conducting solid polymer blend electrolytes (SPBEs) composed of chitosan (CS) and methylcellulose (MC) were prepared for electrochemical double-layer capacitor (EDLC) application with a high specific capacitance and energy density. The change in intensity and the broad nature [...] Read more.
In the present work, promising proton conducting solid polymer blend electrolytes (SPBEs) composed of chitosan (CS) and methylcellulose (MC) were prepared for electrochemical double-layer capacitor (EDLC) application with a high specific capacitance and energy density. The change in intensity and the broad nature of the XRD pattern of doped samples compared to pure CS:MC system evidencedthe amorphous character of the electrolyte samples. The morphology of the samples in FESEM images supported the amorphous behavior of the solid electrolyte films. The results of impedance and Bode plotindicate that the bulk resistance decreasedwith increasing salt concentration. The highest DC conductivity was found to be 2.81 × 10−3 S/cm. The electrical equivalent circuit (EEC) model was conducted for selected samples to explain the complete picture of the electrical properties.The performance of EDLC cells was examined at room temperature by electrochemical techniques, such as impedance spectroscopy, cyclic voltammetry (CV) and constant current charge–discharge techniques. It was found that the studied samples exhibit a very good performance as electrolyte for EDLC applications. Ions were found to be the dominant charge carriers in the polymer electrolyte. The ion transference number (tion) was found to be 0.84 while 0.16 for electron transference number (tel). Through investigation of linear sweep voltammetry (LSV), the CS:MC:NH4SCN system was found to be electrochemically stable up to 1.8 V. The CV plot revealed no redox peak, indicating the occurrence of charge double-layer at the surface of activated carbon electrodes. Specific capacitance (Cspe) for the fabricated EDLC was calculated using CV plot and charge–discharge analyses. It was found to be 66.3 F g−1 and 69.9 F g−1 (at thefirst cycle), respectively. Equivalent series resistance (Resr) of the EDLC was also identified, ranging from 50.0 to 150.0 Ω. Finally, energy density (Ed) was stabilized to anaverage of 8.63 Wh kg−1 from the 10th cycle to the 100th cycle. The first cycle obtained power density (Pd) of 1666.6 W kg−1 and then itdropped to 747.0 W kg−1 at the 50th cycle and continued to drop to 555.5 W kg−1 as the EDLC completed 100 cycles. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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Open AccessArticle
Structure, Shift in Redox Potential and Li-Ion Diffusion Behavior in Tavorite LiFe1−xVxPO4F Solid-Solution Cathodes
Molecules 2019, 24(10), 1893; https://doi.org/10.3390/molecules24101893 - 16 May 2019
Cited by 2 | Viewed by 924
Abstract
Solid-solution Li-ion cathode materials transform through a single-phase reaction thus leading to a long-term structural stability and improved cyclability. In this work, a two- to single-phase Li+-extraction/insertion mechanism is studied through tuning the stoichiometry of transition-metal Fe/V cations to trigger a [...] Read more.
Solid-solution Li-ion cathode materials transform through a single-phase reaction thus leading to a long-term structural stability and improved cyclability. In this work, a two- to single-phase Li+-extraction/insertion mechanism is studied through tuning the stoichiometry of transition-metal Fe/V cations to trigger a transition in the chemical reactivity path. Tavorite triclinic-structured LiFe1−xVxPO4F (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) solid-solution powders were prepared by a facile one-step solid-state method from hydrothermal-synthesized and commercial raw materials. The broad shape of cyclic voltammetry (CV) peaks, sloping charge/discharge profiles and sloping open-circuit voltage (OCV) profiles were observed in LiFe1−xVxPO4F solid-solution cathodes while 0 < x < 1. These confirm strongly a single-phase behavior which is different from the two-phase behavior in the end-members (x = 0 or 1). The electronegativity of M (M = Fe1−xVx) for the redox potential of Fe2+/3+ couple or the M–O4F2 bond length for the V3+/4+ couple plays respectively a dominant role in LiFe1−xVxPO4F solid-solution cathodes. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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Open AccessArticle
Well-Wrapped Li-Rich Layered Cathodes by Reduced Graphene Oxide towards High-Performance Li-Ion Batteries
Molecules 2019, 24(9), 1680; https://doi.org/10.3390/molecules24091680 - 30 Apr 2019
Cited by 1 | Viewed by 1275
Abstract
Layered lithium-rich manganese oxide (LLO) cathode materials have attracted much attention for the development of high-performance lithium-ion batteries. However, they have suffered seriously from disadvantages, such as large irreversible capacity loss during the first cycle, discharge capacity decaying, and poor rate performance. Here, [...] Read more.
Layered lithium-rich manganese oxide (LLO) cathode materials have attracted much attention for the development of high-performance lithium-ion batteries. However, they have suffered seriously from disadvantages, such as large irreversible capacity loss during the first cycle, discharge capacity decaying, and poor rate performance. Here, a novel method was developed to coat the surface of 0.4Li2MnO3∙0.6LiNi1/3Co1/3Mn1/3O2 cathode material with reduced graphene-oxide (rGO) in order to address these drawbacks, where a surfactant was used to facilitate the well-wrapping of rGO. As a result, the modified LLO ([email protected]) cathode exhibits superior electrochemical performance including cycling stability and rate capability compared to the pristine LLO cathode. In particular, the [email protected] with a 0.5% rGO content can deliver a high discharge capacity of 166.3 mAh g−1 at a 5C rate. The novel strategy developed here can provide a vital approach to inhibit the undesired side reactions and structural deterioration of Li-rich cathode materials, and should be greatly useful for other cathode materials to improve their electrochemical performance. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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Open AccessArticle
Synthesis and Luminescence Properties of a Novel Green-Yellow-Emitting Phosphor BiOCl:Pr3+ for Blue-Light-Based w-LEDs
Molecules 2019, 24(7), 1296; https://doi.org/10.3390/molecules24071296 - 03 Apr 2019
Cited by 3 | Viewed by 1127
Abstract
The development of white-light-emitting diodes (w-LEDs) makes it meaningful to develop novel high-performance phosphors excited by blue light. Herein, BiOCl:Pr3+ green-yellow phosphors were prepared via a high-temperature solid-state reaction method. The crystal structure, luminescent properties, lifetime, thermal quenching behavior, and quantum yield [...] Read more.
The development of white-light-emitting diodes (w-LEDs) makes it meaningful to develop novel high-performance phosphors excited by blue light. Herein, BiOCl:Pr3+ green-yellow phosphors were prepared via a high-temperature solid-state reaction method. The crystal structure, luminescent properties, lifetime, thermal quenching behavior, and quantum yield were studied in detail. The BiOCl:Pr3+ phosphors presented several emission peaks located in green and red regions, under excitation at 453 nm. The CIE coordinates could be tuned along with the changed doping concentration with fair luminescence efficiency. The results also indicated that the optimized doping concentration of Pr3+ ions was at x = 0.0075 because of the concentration quenching behavior resulting from an intense exchange effect. When the temperature reached 150 °C, the intensity of the emission peak at 495 nm could remain at 78% of that at room temperature. The activation energy of 0.20 eV also confirmed that the BiOCl:Pr3+ phosphor exhibited good thermal stability. All these results indicate that the prepared products have potential to be used as a high-performance green-yellow-light-emitting phosphor for blue-light-based w-LEDs. Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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Other

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Open AccessConcept Paper
How to Measure and Calculate Equivalent Series Resistance of Electric Double-Layer Capacitors
Molecules 2019, 24(8), 1452; https://doi.org/10.3390/molecules24081452 - 12 Apr 2019
Cited by 13 | Viewed by 1383
Abstract
Electric double-layer capacitors (EDLCs) are energy storage devices that have attracted attention from the scientific community due to their high specific power storage capabilities. The standard method for determining the maximum power (Pmax) of these devices uses the relation P [...] Read more.
Electric double-layer capacitors (EDLCs) are energy storage devices that have attracted attention from the scientific community due to their high specific power storage capabilities. The standard method for determining the maximum power (Pmax) of these devices uses the relation Pmax = U2/4RESR, where U stands for the cell voltage and RESR for the equivalent series resistance. Despite the relevance of RESR, one can observe a lack of consensus in the literature regarding the determination of this parameter from the galvanostatic charge-discharge findings. In addition, a literature survey revealed that roughly half of the scientific papers have calculated the RESR values using the electrochemical impedance spectroscopy (EIS) technique, while the other half used the galvanostatic charge discharge (GCD) method. RESR values extracted from EIS at high frequencies (>10 kHz) do not depend on the particular equivalent circuit model. However, the conventional GCD method better resembles the real situation of the device operation, and thus its use is of paramount importance for practical purposes. In the latter case, the voltage drop (ΔU) verified at the charge-discharge transition for a given applied current (I) is used in conjunction with Ohm’s law to obtain the RESR (e.g., RESR = ΔUI). However, several papers have caused a great confusion in the literature considering only applied current (I). In order to shed light on this important subject, we report in this work a rational analysis regarding the GCD method in order to prove that to obtain reliable RESR values the voltage drop must be normalized by a factor of two (e.g., RESR = ΔU/2I). Full article
(This article belongs to the Special Issue Advances in Electrochemical Energy Storage Devices)
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