Advanced Electrochemical Energy Storage Devices Research Articles

Recent Advances in Biopolymer-Based Hydrogel Electrolytes for Flexible Supercapacitors.

Growing concern regarding the impact of fossil fuels has led to demands for the development of green and renewable materials for advanced electrochemical energy storage devices. Biopolymers with unique hierarchical structures and physicochemical properties, serving as an appealing platform for the advancement of sustainable energy, have found widespread application in the gel electrolytes of supercapacitors. In this Review, we outline the structure and characteristics of various biopolymers, discuss the proposed mechanisms and assess the evaluation metrics of gel electrolytes in supercapacitor devices, and further analyze the roles of biopolymer materials in this context. The state-of-the-art electrochemical performance of biopolymer-based hydrogel electrolytes for supercapacitors and their multiple functionalities are summarized, while underscoring the current technical challenges and potential solutions. This Review is intended to offer a thorough overview of recent developments in biopolymer-based hydrogel electrolytes, highlighting research concerning green and sustainable energy storage devices and potential avenues for further development.

Preparation of Sea Urchin‐Like Co/Ni Alloy Compounds for Pseudocapacitive Supercapacitor

Energy density and power density are the two most crucial metrics in advanced electrochemical energy storage (EES) devices. The design of pseudocapacitor materials with good structure and reasonable composition can ensure that the power density can be greatly increased under the condition of little or no reduction in energy density. However, how to reasonably design excellent pseudocapacitor materials is still a huge challenge. Herein, layered double hydroxides containing Ni and Co elements on carbon materials derived from distillers’ grains by hydrothermal synthesis (NiCo‐LDH/JKPC‐2) are grown. The fabricated NiCo‐LDH/JKPC‐2 has exhibited a sea urchin‐like nanostructure that primarily consists of mesoporous and possesses a high specific surface area (303 m2 g−1), which facilitates the formation of larger active sites, thereby increasing the rate of charge transport. The specific capacitance of the NiCo‐LDH/JKPC‐2 reaches a maximum value of 1454 F g−1 at 1 A g−1. When it combines with carbon materials originating from distillers’ grains, the assembled asymmetric supercapacitor electrode exhibits a remarkable energy density (40.86 Wh kg−1 at 775 W kg−1) and superior power density (7750.8 W kg−1 at 21.53 Wh kg−1). Thus, the NiCo‐LDH/JKPC‐2 asymmetric supercapacitor electrode can be considered as a potential candidate in advanced energy storage device systems.

Sustainable hydrothermal carbon for advanced electrochemical energy storage

The development of advanced electrochemical energy storage devices (EESDs) is of great necessity because these devices can efficiently store electrical energy for diverse applications, including lightweight electric vehicles/aerospace equipment.

Unlocking the Effect of Chain Length and Terminal Group on Ethylene Glycol Ether Family Toward Advanced Aqueous Electrolytes.

Constructing high-performance hybrid electrolyte is important to advanced aqueous electrochemical energy storage devices. However, due to the lack of in-depth understanding of how the molecule structures of cosolvent additives influence the properties of electrolytes significantly impeded the development of hybrid electrolytes. Herein, a series of hybrid electrolytes are prepared by using ethylene glycol ether with different chain lengths and terminal groups as additives. The optimized 2m LiTFSI-90%DDm hybrid electrolyte prepared from diethylene glycol dimethyl ether (DDm) molecule showcases excellent comprehensive performance and significantly enhances the operating voltage of supercapacitors (SCs) to 2.5V by suppressing the activity of water. Moreover, the SC with 2m LiTFSI-90%DDm hybrid electrolyte supplies a long-term cycling life of 50000 cycles at 1Ag-1 with 92.3% capacitance retention as well as excellent low temperature (-40ºC) cycling performance (10000 times at 0.2Ag-1). Universally, Zn//polyaniline full cell with 2m Zn(OTf)2-90%DDm electrolyte manifests outstanding cycling performance in terms of 77.9% capacity retention after 2,000 cycles and a dendrite-free Zn anode. This work inspires new thinking of developing advanced hybrid electrolytes by cosolvent molecule design toward high-performance energy storage devices.

Zinc ion exchange assisted synthesis of R-TiO2@C hollow spheres with superior lithium-ion storage performance

Nanostructured anode materials hold the key to advance the performance of the corresponding lithium-ion batteries as advanced electrochemical energy storage devices. Here, we designed a zinc exchange assisted phase change strategy as an acid-free and well-controlled approach to successfully synthesize a kind of rutile phase TiO2 @C (R-TiO2 @C) hollow spheres with well-defined size by using SiO2 spheres as sacrificial templates. The exchanged zinc ions in an alcohol solvothermal reaction were considered as a phase transition medium to promote the formation of a high-quality rutile TiO2 crystal through a high temperature solid-state heat way. By this way, the final morphologies of rutile phase TiO2 nanocrystals were well controlled, and the rutile TiO2 phase transformation temperature was lower than that of conventional one-step high temperature calcination way (without zinc ions exchange). Note that it successfully avoided using acids as mediums to promote the formation of rutile phase TiO2 crystal in the nano process. Meanwhile, the carbon layer formed by a hydrothermal carbonization reaction not only provided self-supporting solid-state in situ reducing medium for Zn2+ to Zn vapor but also produced conductive porous carbon coating porous and robust R-TiO2 spherical shell with nanosized subunits. The reaction process and mechanism of zinc ions induced phase transformation were discussed. Benefiting from the nanoscale morphology-regulation and hollow structure with enhanced ability of ion and electron transfer as well as electrolyte transport, the resultant R-TiO2 @C hollow spheres can significantly promote Li ions storage and deliver a high reversible specific capacity of 115.6 mAh g-1 at 5.0 C over 1600 cycles. A typical electrochemical reaction on Li ions inserted into TiO2 crystal was simply elaborated as well. This work demonstrates its great potential for practical application in lithium-ion batteries.

Two-Dimensional Conjugated Metal-Organic Frameworks Embedded with Iodine for High-Performance Ammonium-Ion Hybrid Supercapacitors.

Ammonium ions (NH4 + ) are emerging non-metallic charge carriers for advanced electrochemical energy storage devices, due to their low cost, elemental abundance, and environmental benignity. However, finding suitable electrode materials to achieve rapid diffusion kinetics for NH4 + storage remains a great challenge. Herein, we report a two-dimensional conjugated metal-organic framework (2D c-MOF) for immobilizing iodine as a high-performance cathode material for NH4 + hybrid supercapacitors. Cu-HHB (HHB = hexahydroxybenzene) MOF embedded with iodine (Cu-HHB/I2 ) features excellent electrical conductivity, highly porous structure, and rich accessible active sites of copper-bis(dihydroxy) (Cu-O4 ) and iodide species, resulting in a remarkable areal capacitance of 111.7 mF cm-2 at 0.4mA cm-2 . Experimental results and theoretical calculations indicate that Cu-O4 species in Cu-HHB play a critical role in binding polyiodide and suppressing its dissolution, as well as contributing to a large pseudocapacitance with adsorbed iodide. In combination with porous MXene anode, the full NH4 + hybrid supercapacitors deliver an excellent energy density of 31.5 mWh cm-2 and long-term cycling stability with 89.5% capacitance retention after 10,000 cycles, superior to those of the state-of-the-art NH4 + hybrid supercapacitors. This study sheds light on the material design for NH4 + storage, enabling the development of novel high-performance energy storage devices. This article is protected by copyright. All rights reserved.

Deciphering the electrochemical behavior of Mn-based electrode-electrolyte coupling system toward advanced electrochemical energy storage devices

Mn-based aqueous electrochemical energy storage devices (AEESDs) are promising candidates for sustainable and flexible energy applications due to their environmental benignity, high theoretical capacity and versatile architecture. One of the effective strategies to boost their electrochemical performance is to introduce Mn2+ ions into the electrolyte, which can trigger a reversible solid/liquid reaction process of Mn2+/MnO2 deposition/dissolution with a high capacity and an ideal electrochemical kinetics. However, the complex energy storage mechanism that involves the Mn2+/MnO2 deposition/dissolution and the intrinsic insertion/extraction of proton and metal ions remains elusive and poses a great challenge for the rational design of Mn-based AEESDs. Moreover, the insufficient dissolution of MnO2 can lead to the deterioration of performance, which hinders their practical applications. To address these issues, we systematically investigate the Mn2+ ions added Mn-based AEESDs by employing a novel quasi-steady electrochemical measurement technique, and establish a kinetic evolution model to elucidate the solid/liquid reaction at different interface conditions. Furthermore, a full cell is assembled and measured to explore the real electrochemical process of Mn-based electrode with additive Mn2+ ions, which is influenced by the potential windows and charge-discharge rate. This study may provide new insights for the development of advanced AEESDs.

High specific energy and power sodium-based dual-ion supercabatteries by pseudocapacitive Ni-Zn-Mn ternary perovskite fluorides@reduced graphene oxides anodes with conversion-alloying-intercalation triple mechanisms

• A new concept of sodium-based dual-ion supercabattery (S-DICB) was firstly proposed. • The superior pseudocapacitance-dominated kinetics was verified. • The charge storage mechanism of KNZMF@rGO anode was deeply deciphered. • Utilizing different presodiated methods to explore the impact on S-DICB. Sodium (Na)-based electrochemical energy storage devices have drawn particular attention in the renewable and rechargeable energy storage system primarily because of their remarkable energy density and cost-competitive advantages. Herein, we have reported a novel ternary perovskite fluoride K 0.97 Ni 0.31 Zn 0.28 Mn 0.41 F 2.84 with a well-distributed reduced graphene oxide substrate (denoted as KNZMF@rGO) as anode for Na-ion storage that possesses the fast kinetics validated via electrochemical and density functional theory (DFT) methods as well as superior lifespan, which delivers fascinating performances owing to the unexceptionable synergistic effect of Ni, Zn and Mn redox-active species with variable valence. Meanwhile, the surface conversion, alloying and intercalation triple hybridization mechanisms of KNZMF@rGO anode have been explored by the electrochemical analysis and the diverse ex situ physicochemical characterizations. What is more, this work also offers new insights into the device design and proposes the previously unreported “sodium-based dual-ion supercabatteries” (S-DICBs) systems for establishing advanced electrochemical energy storage devices, which exhibit the more intriguing properties than traditional sodium ion capacitors (SICs) and sodium-based dual ion batteries (S-DIBs). In parallel, utilizing different presodiated current densities of anode to explore their impact on the various electrochemical properties of S-DICBs opens up a way for the research of presodiation techniques in the future. A new concept of sodium-based dual-ion supercabattery (S-DICB) was constructed via the pseudocapacitive Ni-Zn-Mn ternary perovskite fluoride (ABF 3 )@reduced graphene oxide (KNZMF@rGO) anode material, which shows the surface conversion/alloying/intercalation triple mechanisms for charge storage. The lower presodiated current density of anode leads to the higher electrochemical properties of S-DICB because of the superior solid electrolyte interface (SEI) film, charge balance and utilization rate of active substance.

Environmental Solid Waste‐derived Carbon for Advanced Rechargeable Lithium‐Sulfur Batteries: A Review

AbstractLithium‐sulfur (Li−S) batteries are lighter and cheaper than today's electrochemical energy storage devices for the forthcoming generations. Particularly the low price and abundance of sulfur as the cathode material, high energy density, and theoretical capacity are delightful characteristics. However, Li−S batteries have many hindrances to attain their commercial applications. Among the challenges are the polysulfide shuttle effect, the insulating property of sulfur, and large volume expansion during charging‐discharging processes. Researchers have carried out comprehensive research on the potential solutions to these challenges. Environmental waste‐derived carbon has an increasingly important role in the energy storage devices (Li−S batteries) due to their sustainable development, low cost, heteroatom doping, large specific surface area, adjustable pore size, easily available sources, and high electric conductivity, which had a significant effect to enhance electrochemical performance. This review highlighted the research progress on carbon derived from environmental solid wastes for the application of Li−S batteries. Furthermore, the preparation, morphology, and design protocols of carbon derived from solid wastes are elaborated for energy storage devices focused on Li−S batteries. These properties inspire researchers in the rational design of environmental waste‐derived carbon materials for sustainable and advanced electrochemical energy storage devices.

Superior capacitive performance of micropore-dominant porous carbon derived from biomass wastes

A series of porous carbon materials with rich O-containing groups are facilely fabricated from the poplar catkin biomass wastes. The optimal KAPC-700-2, which is prepared under the conditions of calcination temperature 700 °C and a mass ratio of 1:2 for the pre-carbonized carbon to activation agent (K2CO3), possesses a micropore-dominant porous network. Benefitting from the hierarchical porous network with a large specific surface area (1410 m2 g−1) and high O-doping amount (11.99 at.%), KAPC-700-2 displays excellent capacitive performance. The corresponding specific capacitance is 278.0 F g−1 at 1.0 A g−1 in the three-electrode system, as well as remarkable rate capability. The energy density in the assembled symmetrical devices (40.5 Wh kg−1 at 0.27 kW kg−1) is superior to many previous results. Other than that, KAPC-700-2 exhibits high cycling stability with a 105.8% capacitance retention in the 30,000th charge/discharge cycle at 1.0 A g−1. Our work offers a good strategy to produce porous carbon from annoying bio-wastes for advanced electrochemical energy storage devices.

Nanostructure and Advanced Energy Storage: Elaborate Material Designs Lead to High-Rate Pseudocapacitive Ion Storage.

The drastic need for development of power and electronic equipment has long been calling for energy storage materials that possess favorable energy and power densities simultaneously, yet neither capacitive nor battery-type materials can meet the aforementioned demand. By contrast, pseudocapacitive materials store ions through redox reactions with charge/discharge rates comparable to those of capacitors, holding the promise of serving as electrode materials in advanced electrochemical energy storage (EES) devices. Therefore, it is of vital importance to enhance pseudocapacitive responses of energy storage materials to obtain excellent energy and power densities at the same time. In this Review, we first present basic concepts and characteristics about pseudocapacitive behaviors for better guidance on material design researches. Second, we discuss several important and effective material design measures for boosting pseudocapacitive responses of materials to improve rate capabilities, which mainly include downsizing, heterostructure engineering, adding atom and vacancy dopants, expanding interlayer distance, exposing active facets, and designing nanosheets. Finally, we outline possible developing trends in the rational design of pseudocapacitive materials and EES devices toward high-performance energy storage.

Optimization of hydrogen-ion storage performance of tungsten trioxide nanowires by niobium doping

The transport and storage of ions within solid state structures is a fundamental limitation for fabricate more advanced electrochemical energy storage, memristor, and electrochromic devices. Crystallographic shear structure can be induced in the tungsten bronze structures composed of corner-sharing WO6 octahedra by the addition of edge-sharing NbO6 octahedra, which might provide more storage sites and more convenient transport channels for external ions such as hydrogen ions and alkali metal ions. Here, we show that Nb2O5·15WO3 nanowires (Nb/W = 0.008) with long length-diameter ratio, smooth surface, and uniform diameter have been successfully synthesized by a simple hydrothermal method. The Nb2O5·15WO3 nanowires do exhibit more advantages over h-WO3 nanowires in electrochemical hydrogen ion storage such as smaller polarization, larger capacity (71 mAh g−1, at 10C, 1C = 100 mA g−1), better cycle performance (remain at 99% of the initial capacity after 200 cycles at 100C) and faster H+ ions diffusion kinetics. It might be the crystallographic shear structure induced by Nb doping that does result in the marked improvement in the hydrogen-ion storage performance of WO3. Therefore, complex niobium tungsten oxide nanowires might offer great promise for the next generation of electrochemical energy and information storage devices.

Cotton fabric-derived hybrid carbon network with N-doped carbon nanotubes grown vertically as flexible multifunctional electrodes for high-rate capacitive energy storage

The emerging electronic textiles (e-textiles) with various functionalities urgently demand the flexible textile-based supercapacitors (TSCs) as reliable power sources. The textiles used for energy storage generally serve as supports/current-collectors and thus hardly contribute capacitance in contrast to electrochemically active materials. Herein, ultralong N-doped carbon nanotubes (NCNTs) are grown directly on the hollow textile carbon (TC) fibers to yield highly conductive TC-NCNTs hybrid network (20.4 S cm −1 ) through a facile one-pot heating strategy, allowing rapid ion and electron kinetics along this 3D interlaced backbone. Electrochemical oxidation of TC-NCNTs for 20 min yields the EATC-NCNTs-20 electrode with an enhanced areal capacitance of 1279 mF cm −2 due to the introduction of tremendous oxygen functional groups. Meanwhile, electrodeposition of CoS nanosheets on TC-NCNTs offers large accessible surface area for pseudocapacitive redox reactions, leading the TC-NCNTs@CoS-8 electrode to achieve an areal capacitance of 2240 mF cm −2 at 5 mA cm −2 , together with a remarkable rate performance (92.6 % capacitance retention at 100 mA cm −2 with CoS mass loading of 10.8 mg cm −2 ). A flexible asymmetric supercapacitor fabricated with the two electrodes delivers an energy density of 2.30 mWh cm −3 at 24.27 mW cm −3 . These results could promote the development of advanced textile-based electrochemical energy storage devices. • Ultralong N-doped CNTs have been successfully grown on flexible textile carbon (TC). • An enhanced areal capacitance is achieved by electrochemical oxidation of TC-NCNTs. • TC-NCNTs@CoS electrode retains 92.6 % areal capacitance at 5–100 mA cm −2 . • A flexible asymmetric supercapacitor delivers an energy density of 2.30 mWh cm −3 .

3D Printing of Next‐generation Electrochemical Energy Storage Devices: from Multiscale to Multimaterial

The increasing energy requirements to power the modern world has driven active research into more advanced electrochemical energy storage devices (EESD) with both high energy densities and power densities. Wide range of newly discovered materials with promising electrochemical properties has shown great potential for next‐generation devices, but their performance is normally associated with contradicting demands of thin electrodes and high mass loading that can be hardly achieved for practical applications. Design of three‐dimensional (3D) porous electrodes can increase the mass loading while maintaining the effective charge transport even with thick electrodes, which has proven to be efficient to overcome the limitations. 3D structures have also been demonstrated excellent structural stability to withstand strong strains and stresses generated during charge/discharge cycle. 3D printing, which can fabricate various delicate and complex structural designs, thus offering brand‐new opportunities for the rational design and facile construction of next‐generation EESDs. The recent developments in 3D printing of next‐generation EESDs with high performance are reviewed. Advanced/multiscale electrode structures, such as hierarchically porous structure that can be constructed via high‐resolution 3D printing or with post‐treatment, are further emphasized. The ability of current 3D printing techniques to fulfill multimaterial printing to fulfill simple packaging will be covered.

Application of Ionic Liquids for Batteries and Supercapacitors.

Nowadays, the rapid development and demand of high-performance, lightweight, low cost, portable/wearable electronic devices in electrical vehicles, aerospace, medical systems, etc., strongly motivates researchers towards advanced electrochemical energy storage (EES) devices and technologies. The electrolyte is also one of the most significant components of EES devices, such as batteries and supercapacitors. In addition to rapid ion transport and the stable electrochemical performance of electrolytes, great efforts are required to overcome safety issues due to flammability, leakage and thermal instability. A lot of research has already been completed on solid polymer electrolytes, but they are still lagging for practical application. Over the past few decades, ionic liquids (ILs) as electrolytes have been of considerable interest in Li-ion batteries and supercapacitor applications and could be an important way to make breakthroughs for the next-generation EES systems. The high ionic conductivity, low melting point (lower than 100 °C), wide electrochemical potential window (up to 5–6 V vs. Li+/Li), good thermal stability, non-flammability, low volatility due to cation–anion combinations and the promising self-healing ability of ILs make them superior as “green” solvents for industrial EES applications. In this short review, we try to provide an overview of the recent research on ILs electrolytes, their advantages and challenges for next-generation Li-ion battery and supercapacitor applications.

Porous nitrogen-enriched hollow carbon nanofibers as freestanding electrode for enhanced lithium storage

One-dimensional porous carbons bearing high surface areas and sufficient heteroatom doped functionalities are essential for advanced electrochemical energy storage devices, especially for developing freestanding film electrodes. Here we develop a porous, nitrogen-enriched, freestanding hollow carbon nanofiber (PN-FHCF) electrode material via filtration of polypyrrole (PPy) hollow nanofibers formed by in situ self-degraded template-assisted strategy, followed by NH3-assisted carbonization. The PN-FHCF retains the freestanding film morphology that is composed of three-dimensional networks from the entanglement of 1D nanofiber and delivers 3.7-fold increase in specific surface area (592 m2·g−1) compared to the carbon without NH3 treatment (FHCF). In spite of the enhanced specific surface area, PN-FHCF still exhibits comparable high content of surface N functionalities (8.8%, atom fraction) to FHCF. Such developed hierarchical porous structure without sacrificing N doping functionalities together enables the achievement of high capacity, high-rate property and good cycling stability when applied as self-supporting anode in lithium-ion batteries, superior to those of FHCF without NH3 treatment.

Surface and Interface Engineering of Nanoarrays toward Advanced Electrodes and Electrochemical Energy Storage Devices.

The overall performance of electrochemical energy storage devices (EESDs) is intrinsically correlated with surfaces and interfaces. As a promising electrode architecture, 3D nanoarrays (3D-NAs) possess relatively ordered, continuous, and fully exposed active surfaces of individual nanostructures, facilitating mass and electron transport within the electrode and charge transfer across interfaces and providing an ideal platform for engineering. Herein, a critical overview of the surface and interface engineering of 3D-NAs, from electrode and interface designs to device integration, is presented. The general merits of 3D-NAs and surface/interface engineering principles of 3D-NA hybrid electrodes are highlighted. The focus is on the use of 3D-NAs as a superior platform to regulate the interface nature and unveiling new mechanism/materials without the interference of binders. The engineering and utilization of the surface of 3D-NAs to develop flexible/solid-state EESDs with 3D integrated electrode/electrolyte interfaces, or 3D triphase interfaces involving other active species, which are characteristic of (quasi-)solid-state electrolyte infiltration into the entire device, are also considered. Finally, the challenges and future directions of surface/interface engineering of 3D-NAs are outlined. In particular, potential strategies to obtain electrode charge balance, optimize the multiphase solid-state interface, and attain 3D solid electrolyte infiltration are proposed.

Recent progress in conductive polymers for advanced fiber-shaped electrochemical energy storage devices

Conductive polymers endow fiber-shaped electrodes and devices with excellent mechanical and electrochemical performance for energy storage in future wearable electronics.

N, O self-codoped hierarchical porous carbon from chitosan for supercapacitor electrode active materials

The oxygen and nitrogen self-codoped activated carbon nanosheets are facilely prepared from chitosan by using ZnCl2. The optimal carbon possesses a significantly increased specific surface area (SBET = 1679 m2 g− 1) and richer porosity (Vp = 0.792 cm3 g− 1) in comparison with the pristine carbon prepared without using ZnCl2 (Vp = 0.035 cm3 g− 1, SBET = 80 m2 g− 1). The well-developed hierarchical porous structure and high heteroatom contents (N 7.35 at%, O 8.96 at%) endow the optimal carbon superior capacitive performance. It delivers a specific capacitance of 287.94 F g− 1 at 1.0 A g− 1 in the three-electrode supercapacitors. Moreover, the optimal carbon-based symmetric supercapacitor achieves an energy density of 28.74 Wh kg− 1 when the power density is 399.92 W kg− 1, and demonstrates satisfactory cycling stability. Our work provides an effective way for fabricating heteroatom self-doped porous carbon materials for advanced electrochemical energy storage devices.

Efficient bifunctional electrocatalysts for solid oxide cells based on the structural evolution of perovskites with abundant defects and exsolved CoFe nanoparticles

Solid oxide cells (SOCs) including solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are advanced electrochemical energy storage and conversion devices. However, the lack of highly active and stable fuel electrode materials impedes their practical applications. Herein, in-situ exsolved CoFe nanoparticles on perovskite matrixes with abundant defects are developed as bifunctional fuel electrocatalysts for SOCs from the Sr2FeMo1-xCoxO6−δ (x = 0, 0.15, 0.25, 0.45) precursor. Increasement of Co doping promotes CoFe alloy exsolution and the formation of more defects in the remaining perovskite matrix under reducing atmosphere at high temperatures. Consequently, with increasing Co dopant content, the electrocatalytic activity towards CO2 electrolysis and hydrogen (H2) fuel oxidation are both significantly enhanced for the reduced Sr2FeMo1-xCoxO6−δ. The reduced Sr2FeMo1-xCoxO6−δ with high Co doping content of x = 0.45 electrocatalysts also exhibits respectable coking resistance and excellent long-term stability. The high performance may be owing to the unique simultaneously in-situ formed nanoalloy-oxide heterostructure and electron-ion mixed conductive perovskite matrixes with abundant defects.