Electrodes For Energy Storage Research Articles

A Highly Robust and Conducting Ultramicroporous 3D Fe(II)-Based Metal-Organic Framework for Efficient Energy Storage.

Exploitation of metal-organic framework (MOF) materials as active electrodes for energy storage or conversion is reasonably challenging owing to their poor robustness against various acidic/basic conditions and conventionally low electric conductivity. Keeping this in perspective, herein, a 3D ultramicroporous triazolate Fe-MOF (abbreviated as Fe-MET) is judiciously employed using cheap and commercially available starting materials. Fe-MET possesses ultra-stability against various chemical environments (pH-1 to pH-14 with varied organic solvents) and is highly electrically conductive (σ=0.19Sm-1) in one fell swoop. By taking advantage of the properties mentioned above, Fe-MET electrodes give prominence to electrochemical capacitor (EC) performance by delivering an astounding gravimetric (304Fg-1) and areal (181mFcm-2) capacitance at 0.5Ag-1 current density with exceptionally high cycling stability. Implementation of Fe-MET as an exclusive (by not using any conductive additives) EC electrode in solid-state energy storage devices outperforms most of the reported MOF-based EC materials and even surpasses certain porous carbon and graphene materials, showcasing superior capabilities and great promise compared to various other alternatives as energy storage materials.

Fabrication of nickel-cobalt sulfide heterostructures with stable thermodynamic interfaces and enhanced electrochemical performance

Transition metal sulfides (TMS) with multicomponent heterostructure have been widely used as electrodes in electrochemical energy storage devices due to their abundant electroactive sites and fast charge transfer across the interfaces. Different kinds of heterostructures with specific TMS are fabricated by various routes to date, but it is still poorly understood how specific thermodynamic interfaces can be designed and easily coupled. Herein, the spinel and cobalt-pentlandite crystal phases of nickel–cobalt sulfides were chosen as models to demonstrate the formation of epitaxial heterointerface. The density functional theory calculations revealed the easy combination and high compatibility of these two crystal phases at the (111) plane. Along this guideline, a novel NiCo2S4/[Ni, Co]9S8 heterostructure was synthesized by a facile one-step hydrothermal strategy, with nanosheet-like shapes and well-defined heterointerfaces along the [111] crystal direction. The formation mechanism of the epitaxial heterointerface was proposed through the combination of solid and liquid phase reaction fields. As a proof-of-concept application, the obtained NiCo2S4/[Ni, Co]9S8 heterostructure as redox electrode for supercapacitor exhibits an enhanced specific capacitance of 1780F g−1 at 1 A/g and high capacitance retention of 70 % at 20 A/g. Moreover, the assembled aqueous hybrid supercapacitor of NiCo2S4/[Ni, Co]9S8//activated carbon delivers a high energy density of 62.8 Wh kg−1 at 0.4 kW kg−1 and excellent electrochemical stability after 3000 cycles. This work provides a new perspective on the epitaxial design of nickel–cobalt sulfide heterostructure with good lattice match as a promising electrode in energy storage devices.

A close-packed sphere model for characterising porous networks in atomistic simulations and its application in energy storage and conversion

Hierarchical (micro, meso & macro) porosity in materials plays a crucial role in influencing the movement of ions which governs the energy and power density during energy storage and conversion. The extant available methods to characterise porosity across scales (nano to meso to macro) lacks rigour and accuracy. Having accurate assessment of the porosity in materials can unlock new designs of electrodes for energy efficient energy storage and conversion devices such as batteries, supercapacitors and fuel cells. Through this work, we report the systematic development of a method to fully characterise the carbon porous networks using a molecular dynamics simulation testbed. Our work entails modelling and simulation of porous carbon structures using quenched molecular dynamics (QMD) simulations using Gaussian Approximation potential (GAP) and benchmarking the results with prior literature. This modelling technique can reliably be used for quantitative characterisation of the interconnectivity in porous structures to study ionic movements and charge transfer mechanisms. A new parameter, namely nearest neighbour search (NNS) coefficient was introduced to quantify homogeneity and networking in the porous structures. NNS coefficient increased from 1.62 to 1.92 with decrease of the annealing temperature from 8000 K to 4000 K in carbon. The procedure outlined was although tested on porous carbon networks, but adaptable to study any other material system at multi-length scales.

Doping Ti3C2Tx with Sn to enhance the stability of electrode for supercapacitor

The chemical instability and self-restacking have become major hurdle to the practical application of Ti3C2Tx although it is considered to be the promising candidates for energy storage. Herein, one-step process is developed to increase the stability and inhibit the self-agglomeration of Ti3C2Tx by using SnCl2 in ethanol to intercalate Ti3C2Tx. Characterization results demonstrate that Sn has doped into Ti3C2Tx (termed Ti3C2Tx-Sn). The obtained Ti3C2Tx-Sn shows an enlarged interlayer spacing to facilitate the rapid diffusion of electrolyte ions, and improve the stability by reducing its oxidation rate. In 1.0 M H2SO4 solution, the optimal Ti3C2Tx-Sn sample (labelled as Ti3C2Tx-Sn-2) can retain 93.5 % of its initial capacitance after 10,000 cycles, but Ti3C2Tx electrode only 51.2 %. Especially, after storage for 120 days in a refrigerator at −18 °C, the Ti3C2Tx-Sn-2 sample still exhibits excellent cycle stability (84.6 % capacitive retention after 10,000 cycles) while Ti3C2Tx sample remains negligible capacitance retention (only 2.7 % of its initial capacitance). It is believed that this work provides a simple and mild strategy to prepare high-stability Ti3C2Tx-based electrodes for energy storage.

Self-supported iron-doped nickel oxide multifunctional electrodes for highly efficient energy storage and overall water-splitting uses

Caused by complex synthesis processes, slow diffusion rates, and the formation of undesired nanostructures, it is tedious to produce a high-quality nickel oxide (NiO) electrodes for potential energy storage and water splitting applications. This paper introduces a novel chemical technique for producing self-supported iron-doped NiO electrodes having a high concentration of oxygen vacancies by utilizing different iron-based salts i.e. iron nitrate, iron chloride, iron ammonium sulfate, iron fumarate, and iron sulfate salts. After examining physical properties, the electrochemical energy storage and water splitting measurements were performed where iron nitrate precursor-mediated self-supporting Fe-NiO electrode confirms the optimum performance. Specifically, it exhibits a specific capacitance (SC) of 3302.5 Fg−1 at a current density of 5 Ag−1. The as-fabricated Fe-NiO-A//Bi2O3 asymmetric supercapacitor has a broad voltage range of 1.5 V, a remarkable volumetric-energy-density of 98.2 W hkg−1 at a power density of 900 Wkg−1, and a long-lasting cycling life with 92.6 % capacity retention after 5000 cycles at a current density of 15 Ag−1. A bifunctional Fe-NiO//Fe-NiO electrocatalyst demonstrates a current density of 10 mA cm−2 and remarkable long-term durability of 75 h without any degradation while operating at an ultra-low cell voltage of only 1.51 V, specifying importance of self-supported Fe-doped NiO electrodes for electrochemical energy storage and water splitting applications.

Nano-alumina islands enabling superior capacitive lithium-ion storage of pitaya configuration

Currently, high-temperature thermal failure hinders the development of lithium-ion batteries (LIBs). Interfacial side reaction of electrolyte and electrode is the main cause of thermal failure at high temperature. Explicitly, suppressing interfacial side reactions at high temperatures can help the research of capacitive energy storage electrodes. While, thermo-electrochemical inert alumina can be facilitated to solve this problem. In this paper, pitaya configuration of nano-alumina islands uniformly dispersed in carbon matrix can be achieved from NOTT-300(Al). Nano-alumina contributes to the structural stability of porous carbon during carbonization and lithium deintercalation. And nano-alumina islands are effective in suppressing interfacial side reactions at high temperatures. Thus, NC-3 exhibits competitive specific capacity (717.1 mAh/g) and cycling stability (99.15% after 500 cycles). NC-3's capacity was confirmed to be mainly attributed to capacitive energy storage mechanism. This study provides a new research paradigm for nano-alumina to improve the high-temperature thermal stability management of LIBs.

Manganese ferrite/reduced graphene oxide composites as energy storage electrode materials for supercapacitors

Manganese ferrite/reduced graphene oxide composites as energy storage electrode materials for supercapacitors

ReS2/CoS heterostructure catalysts for electrochemical application in hydrogen evolution and supercapacitor

Development of Nano-heterostructures based on transition metal chalcogenides is promising strategy to accelerate the catalytic performance for hydrogen evolution reaction (HER) and supercapacitor application. The design and development of non-noble transition metal based catalysts is required for the low-cost, efficient and earth-abundant electrodes for sustainable energy conversion and storage. ReS2/CoS heterostructures were synthesized by two step methods involving liquid phase exfoliation of ReS2 and hydrothermal decoration of CoS. The prepared ReS2/CoS heterostructures shows high performance supercapacitor applications with specific capacitance of 663.2 F/g at 2 A/g and 643.1 F/g at scan rate 5 mV/s, showing enhanced redox reaction and number of electrochemically active sites due to synergistic effect and modulated electronic structure. Additionally, ReS2/CoS heterostructures shows the superior HER performance in alkaline condition with overpotential of 187 mV at 10 mA/cm2 due to accelerated kinetics, enhanced ECSA and low charge transfer resistance. The ReS2/CoS heterostructures shows the stable electrochemical performance for HER for more than 17 h.

Multiscale hierarchical nanoarchitectonics with stereographically 3D-printed electrodes for water splitting and energy storage

The pursuit of sustainable solutions to address the global energy crisis has led to a keen interest in the advancement of cost-effective and multifunctional electrochemical systems. These systems aim to achieve both zero-carbon emissions and the dual capability to convert and store energy efficiently. The electrochemical splitting of water is one way to create carbon–neutral, clean hydrogen gas. Electrocatalysis and hydrogen evolution in general depends not only on the catalyst but also on its nano- and microstructure, which influences local chemical conditions and hydrogen gas bubble detachment. Therefore, rapid screening of not only potential catalysts but also various structured surfaces is needed for effective electrode fabrication. The fused deposition modeling (FDM) method of 3D printing is frequently used for electrode fabrication using conducting filaments; however, its micro-structuration resolution is limited. Stereolithography can produce complex and fine structures; however, the resins are not conductive and therefore the structures are not suitable for electrode fabrication. In this work, we have fabricated a substrate with high-resolution needle array architecture using stereolithographic (SLA) 3D printing and coated it with Co3Te4-CoTe2 (COT) nanofiber for water splitting and energy storage. The SLA 3D-printed cobalt telluride electrodes showed appreciable performance as a photoelectrocatalyst for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), acting as a bifunctional catalyst. We also demonstrated fabrication of a cobalt telluride based SLA 3D-printed supercapacitor device with multiscale hierarchy. The SLA 3D-printed supercapacitor device exhibited good electrochemical behavior along with high cycling stability. In general, we show here a universal method for SLA conductive electrode fabrication with hierarchical structuring of functional elements and suitable for various applications.

Porphyrin-Thiophene Based Conjugated Polymer Cathode with High Capacity for Lithium-Organic Batteries.

Organic electrode materials are promising for next-generation energy storage materials due to their environmental friendliness and sustainable renewability. However, problems such as their high solubility in electrolytes and low intrinsic conductivity have always plagued their further application. Polymerization to form conjugated organic polymers can not only inhibit the dissolution of organic electrodes in the electrolyte, but also enhance the intrinsic conductivity of organic molecules. Herein, we synthesized a new conjugated organic polymer (COPs) COP500-CuT2TP (poly [5,10,15,20-tetra(2,2'-bithiophen-5-yl) porphyrinato] copper (II)) by electrochemical polymerization method. Due to the self-exfoliation behavior, the porphyrin cathode exhibited a reversible discharge capacity of 420 mAh g-1, and a high specific energy of 900 Wh Kg-1 with a first coulombic efficiency of 96 % at 100 mA g-1. Excellent cycling stability up to 8000 cycles without capacity loss was achieved even at a high current density of 5 A g-1. This highly conjugated structure promotes COP500-CuT2TP combined high energy density, high power density, and good cycling stability, which would open new opportunity for the designable and versatile organic electrodes for electrochemical energy storage.

Porphyrin‐Thiophene Based Conjugated Polymer Cathode with High Capacity for Lithium‐Organic Batteries

AbstractOrganic electrode materials are promising for next‐generation energy storage materials due to their environmental friendliness and sustainable renewability. However, problems such as their high solubility in electrolytes and low intrinsic conductivity have always plagued their further application. Polymerization to form conjugated organic polymers can not only inhibit the dissolution of organic electrodes in the electrolyte, but also enhance the intrinsic conductivity of organic molecules. Herein, we synthesized a new conjugated organic polymer (COPs) COP500‐CuT2TP (poly [5,10,15,20‐tetra(2,2′‐bithiophen‐5‐yl) porphyrinato] copper (II)) by electrochemical polymerization method. Due to the self‐exfoliation behavior, the porphyrin cathode exhibited a reversible discharge capacity of 420 mAh g−1, and a high specific energy of 900 Wh Kg−1 with a first coulombic efficiency of 96 % at 100 mA g−1. Excellent cycling stability up to 8000 cycles without capacity loss was achieved even at a high current density of 5 A g−1. This highly conjugated structure promotes COP500‐CuT2TP combined high energy density, high power density, and good cycling stability, which would open new opportunity for the designable and versatile organic electrodes for electrochemical energy storage.

Pristine cobalt humic acid xerogels embedded with ultrafine cobalt sulfide for enhanced and stable lithium-ion storage

The electrochemical performance of pristine metal–organic xerogels as anodes in lithium-ion batteries is reported for the first time. We propose a novel synthesis approach for the in situ generation of highly dispersed, ultrafine cobalt sulfide nanoparticles on humic acid gels (CoSHA). The CoS nanoparticles in CoSHA have an average diameter of approximately 3 nm. CoSHA electrodes demonstrate enhanced lithium storage capacity, delivering a capacity of 662 mAh g−1 at 0.1 A g−1. They also show stable long-term cycling performance, with no capacity decay after 900 cycles at 1.0 A g−1. Furthermore, our experiments indicate that the improved lithium-ion adsorption results from the oxygen-containing functional groups in humic acid and the ultrafine CoS active sites. This study offers a practical methodology for synthesizing ultrafine metal sulfides and new insights into using pristine gel-based electrodes for energy storage and conversion.

Storage dynamics of ions on graphene

AbstractCarbon has been widely utilized as electrode in electrochemical energy storage, relying on the interaction between ions and electrode. The performance of a carbon electrode is determined by a variety of factors including the structural features of carbon material and the behavior of ions adsorbed on the carbon surface in the specific environment. As the fundamental unit of graphitic carbons, graphene has been employed as a model to understand the energy storage mechanism of carbon materials through various experimental and computational methods, ex‐situ or in‐situ. In this article, we provide a succinct overview of the state‐of‐the‐art proceedings on the ion storage mechanism on graphene. Topics include the structure engineering of carbons, electric gating effect of ions, ion dynamics on the interface or in the confined space, and specifically lithium‐ion storage/reaction on graphene. Our aim is to facilitate the understanding of electrochemistry on carbon electrodes.

Building a Rechargeable Voltaic Battery via Reversible Oxide Anion Insertion in Copper Electrodes.

Voltaic pile, the very first battery built by humanity in 1800, plays a seminal role in battery development history. However, the premature design leads to the inevitable copper ion dissolution issue, which dictates its primary battery nature. To address this issue, solid-state electrolytes, ion exchange membranes, and/or sophisticated electrolytes are widely utilized, leading to high costs and complicated cell configuration. Herein, we build a rechargeable zinc-copper voltaic battery from simple and cheap electrolyte/separator materials, thus eliminating the need to use the above components. Notably, our battery leverages the Zn4SO4(OH)6·xH2O precipitation in ZnSO4 electrolytes, a common side reaction in zinc batteries, to provide a "locally alkaline" environment for copper electrodes. Consequently, oxide (O2-) anion insertion takes place and readily transforms copper to copper(I) oxide (Cu2O) without any copper ion dissolution issue. Therefore, this battery realizes a high capacity of ∼370 mA h g-1 and a long cycling of ∼500 cycles. Our work provides an innovative approach to stabilize anion insertion in metal electrodes for energy storage.

Atomic and Electronic Structure of Metal–Salen Complexes [M(Salen)], Their Polymers and Composites Based on Them with Carbon Nanostructures: Review of X-ray Spectroscopy Studies

Currently, electrically conductive polymers based on transition metal complexes [M(Salen)], as well as their composites, are among the systems showing promise as catalysts, electrochromic and electroluminescent materials, and electrodes for energy storage (for batteries and supercapacitors). The current review focuses on elucidating the atomic and electronic structure of metal–salen complexes, their polymers, and composites with nanostructured carbon (carbon nanotubes and graphene) using modern X-ray spectroscopy methods (X-ray photoelectron (XPS) and valence-band photoemission (VB PES) spectroscopy, as well as near-edge (NEXAFS) and extended (EXAFS) X-ray absorption fine structure spectroscopy). We trust that this review will be of valuable assistance to researchers working in the field of synthesizing and characterizing metal–salen complexes and composites based on them.

In-situ fabrication of a novel CNTs-promoted Na3MnTi(PO4)3@C electrode in high-property sodium-ion storage

NASICON-type Na3MnTi(PO4)3 (NMTPO) material is suggested as a novel electrode in sodium energy storage because of its high plateaus, high theoretical capacity, low toxicity and cheap price. Nevertheless, the pristine NMTPO electrode shows the bad high-rate property and poor cycling-life owing to the disappointing electrical conductivity. In this research, we adopt a facile strategy to fabricate the CNTs-promoted NMTPO with in-situ carbon coating (CNTs-NMTPO@C) as promising electrode in sodium-ion storage. Benefiting from the synergistic effects of nanosized NMTPO, thin carbon coating and CNTs, the as-fabricated CNTs-NMTPO@C electrode displays good rate property and superior cycling stability. It can deliver the reversible capacity of 136.8 mAh g−1 at 2.0C and possess a capacity retention of around 92.2 % over 300 cycles at 10.0C. Therefore, we can make a conclusion that the designed CNTs-NMTPO@C material is a promising cathode in sodium-ion storage.

Organic polymer coating induced multiple heteroatom-doped carbon framework confined Co1-xS@NPSC core-shell hexapod for advanced sodium/potassium ion batteries

Synthesis of advanced structure and multiple heteroatom-doped carbon based heterostructure materials are the key to the preparation of high-performance energy storage electrode materials. Herein, the hexapod-shaped Co1-xS@NPSC has been triumphantly prepared using hexapod ZIF-67 as the sacrificial template to prepare Co1-xS inner core and N, P, and S tri-doped carbon (NPSC) as the shell through the carbonization of the organic polymer precursor. When applied as anode for Na+ batteries (SIBs) and K+ batteries (PIBs), Co1-xS@NPSC presents the high reversible specific capability of 747.4 mAh/g at 1.0 A/g after 235 cycles and 387.8 mAh/g at 5.0 A/g after 760 cycles for SIBs, as well as 326.7 mAh/g at 1.0 A/g after 180 cycles for PIBs. The excellent storage capacity and rate capability of Co1-xS@NPSC is ascribed to hexapod structure of ZIF-67 unlike the common dodecahedron, which is constructed with interior porous and exterior framework repository, donating supplemental active sites, and doping of multiple heteroatoms forming organic polymer coating inhibiting the volume expansion and restrains the agglomeration of Co1-xS nanoparticles. This approach has paved a bright avenue to exploit promising anode materials with novel structure and hetero-atom doping for high-performance energy storage devices.

Energy utilization of agricultural waste: Machine learning prediction and pyrolysis transformation

The rapid screening of agricultural waste materials for capacitor preparation holds significant importance in comprehending the relationship between material properties and enhancing experimental efficiency. In this study, we developed two machine learning models to predict electrode material characteristics using 2997 data points extracted from 235 articles. The identification and influence of key features on prediction indices provide a theoretical foundation for subsequent practical preparation. Through regression analysis and index evaluation, corn straw emerged as the optimal material for capacitor preparation, leading us to propose a one-step activation and two-step modification approach to convert corn straw into porous biochar. By modifying biochar with Co(NO3)2·6H2O, the maximum electrode capacitance of porous carbon reached 732.6 F/g. Furthermore, the electrode exhibited exceptional cycle stability with a remaining capacitance of 96 % after 5000 cycles. The prepared symmetric capacitor demonstrated pseudocapacitance behavior with a capacitance of 183.15 F/g at a current density of 1.0 A/g, power density of 22 kW/kg, and energy density of 9.03 Wh/kg. Considering the increasing annual output of corn straw and its superior industrial application prospects compared to acid-, base-, or precious metal-based alternatives due to their cost-effectiveness and environmental friendliness, these findings highlight the potential practical value in utilizing modified corn straw biochar as an efficient energy storage electrode material.

Synthesis strategies of smart 3D nanoarchitectures and their applications in energy storage and conversion

AbstractThe creation of effective and clean energy storage technologies has advanced dramatically due to growing worldwide worries over the depletion of fossil fuels and environmental issues. Energy storage and conversion systems have emerged as a crucial component with the development of numerous electronic devices, enabling the devices to function for extended periods of time. Due to their enormous surface area, strong electrical conductivity, and ion transport, 3D self‐supported nanoarchitectures associated with electrochemical energy storage (EES) devices can offer alternatives for enhancing the performance and advancement of existing EES systems. Here, we present the results of our findings regarding the design, production, and use of self‐supported 3D nanostructures in energy storage and conversion systems such as supercapacitors, batteries, solar cells, and fuel cells. A variety of advanced 3D nanomaterials may be readily created on an immense scale using various synthetic techniques, and they have a great deal of potential for use as electrodes in energy storage and conversion devices with much better performance. These fabrication techniques include electrochemical deposition, electrospinning, chemical precipitation, spray pyrolysis, sol‐gel method, hydrothermal method, chemical vapor deposition, and so forth.

In-situ grown nickel iron bimetal organic frameworks from activated Ni foam for efficient energy storage and electrocatalysis: Study of metal ratio and nickel precursor effects

Ex-situ fabrication of electroactive electrodes encounters serious peeling off problems. Nickel foam (NF) shows promise as conductive substrate of electroactive electrodes due to high surface area, porosity and conductivity. To broaden NF applications and enhance attachments, applying in-situ growth for establishing efficient active materials on NF is necessary. In this study, nickel iron bimetal organic frameworks (NiFeMOF) are firstly synthesized from activated NF as electroactive electrodes for energy storage and electrocatalysis. Metal ratio and nickel precursor effects are studied to elucidate growing mechanism of electroactive materials. The optimal NiFeMOF/NF presents the highest specific capacitance (CF) of 2017.9 F/g at 20 mV/s, while MOF/NF electrodes prepared with only Ni and Fe respectively show smaller CF values of 622.1 and 1121.8 F/g. The superior electrocatalytic ability is achieved by NiFeMOF/NF. Inclusion of additional Ni salts is necessary for synthesizing Ni-MOF on NF with improved energy storage ability, but that prepared without addition of Ni salt exhibits better electrocatalytic ability. Trade-off between electrochemical surface area and electrical conductivity is proved as crucial factor in designing electroactive materials for energy storage and electrocatalytic water splitting. This study brings novel insights into establishment of effective electroactive materials for electrochemical systems using simple concepts and techniques.