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Rechargeable Zn‐based batteries provide a compelling supplement to subsistent energy storage devices owing to their high energy density, good safety, and low cost. Nevertheless, inherent imperfections such as dendrite growth, side reactions, and andante reaction kinetics, severely impede their commercialization. As new 0D nanomaterials, carbon dots (CDs) with unique characteristics and excellent electrochemical activity, exhibit promising potential exploitation in electrochemistry and electrocatalysis areas. Herein, the adhibition of CDs in resolving the aforementioned drawbacks of Zn‐based batteries is introduced. To begin with, concepts, physicochemical properties, and synthetic methods of CDs are discussed. Next, recent developments and advances exploiting CDs in respectively ameliorating the performance of the Zn anode, the cathode, and electrolytes of Zn ion batteries and bifunctional electrocatalytic activities including oxygen reduction reaction and oxygen evolution reaction for Zn‐air batteries, are roundly reviewed and minutely generalized. Finally, current challenges and prospects are surveyed as well, aiming to offer a reference for the blossom of advanced Zn‐based batteries. [ABSTRACT FROM AUTHOR]

The electric eel is known as the most powerful creature to generate electricity with a discharge voltage up to 860 V and peak current up to 1 A. These surprising properties are the results of billions of years of evolution on the electrical biological structure and bulk, and now have triggered great research interest in electric eel biomimetics for designing innovated configurations and components of energy storage and conversion devices. In this review, first, the bioelectrical behavior of electric eels is surveyed, followed by the physiological structure to reveal the discharge characteristics and principles of electric organs and electrocytes. Additionally, underlying electrochemical mechanisms and models for calculating the potential and current of electrocytes are presented. Central to this review is the recent progress of electric‐eel‐inspired innovations and applications for energy storage and conversion, particularly including novel power sources, triboelectric nanogenerators, and nanochannel ion‐selective membranes for salinity gradient energy harvesting. Finally, insights on the challenges at the moment and the perspectives on the future research prospects are critically compiled. It is suggested that energy‐related electric eel biomimetics will greatly boost the development of next‐generation high performance, green, and functional electronics. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable batteries (ARBs) have attracted wide attention due to their rich resources, environmental friendliness, and safety. The high ionic conductivity, safety and interfacial wettability of the aqueous electrolyte are essential for energy storage devices. However, the narrow electrochemical stability window (ESW) of the aqueous electrolyte and the side reactions of the electrode/electrolyte lead to the low energy density of the ARBs. In the past studies, the above problems were generally solved by improving the ion transport characteristics of the electrolyte and the electrode/electrolyte interface. Herein, we discuss the background, limitations, and key concepts for performance improvement of aqueous electrolytes, aiming to provide a comprehensive perspective and inspiration for further research on aqueous electrolytes and promote their development and application in the field of energy storage. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) have rapidly risen to the forefront of energy storage systems as a promising supplementary for Lithium‐ion batteries (LIBs). Na3V2(PO4)2F3 (NVPF) as a common cathode of SIBs, features the merits of high operating voltage, small volume change and favorable specific energy density. However, it suffers from poor cycling stability and rate performance induced by its low intrinsic conductivity. Herein, we propose an ingenious strategy targeting superior SIBs through cross‐linked NVPF with multi‐dimensional nanocarbon frameworks composed of amorphous carbon and carbon nanotubes (NVPF@C@CNTs). This rational design ensures favorable particle size for shortened sodium ion transmission pathway as well as improved electronic transfer network, thus leading to enhanced charge transfer kinetics and superior cycling stability. Benefited from this unique structure, significantly improved electrochemical properties are obtained, including high specific capacity (126.9 mAh g−1 at 1 C, 1 C = 128 mA g−1) and remarkably improved long‐term cycling stability with 93.9% capacity retention after 1000 cycles at 20 C. The energy density of 286.8 Wh kg−1 can be reached for full cells with hard carbon as anode (NVPF@C@CNTs//HC). Additionally, the electrochemical performance of the full cell at high temperature is also investigated (95.3 mAh g−1 after 100 cycles at 1 C at 50 °C). Such nanoscale dual‐carbon networks engineering and thorough discussion of ion diffusion kinetics might make contributions to accelerating the process of phosphate cathodes in SIBs for large‐scale energy storages. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been widely adopted in various fields (catalysis, sensor, energy storage, etc.) during the last decade owing to the trait of abundant surface chemistry, porous structure, easy‐to‐adjust pore size, and diverse functional groups. However, the limited active sites and the poor conductivity hinder the relative practical application. 2D MOFs can shorten the ion transport path with the merit of layered structure. The large surface area can increase the number of active sites as well as effectively utilize the sufficient active sites, exhibiting enormous potential in the field of energy storage systems (EESs). In this review, the characteristics of the 2D MOFs have been introduced, and the systematic synthesis methods (top‐down and bottom‐up) of 2D MOFs are presented, providing fundamental understanding for the construction of 2D MOFs. Moreover, the applications of 2D MOFs in energy storage fields such as supercapacitors and batteries are demonstrated in detail. Finally, the future development prospects have been proposed, offering guidelines for the rational utilization of 2D MOFs and promoting the understanding of 2D MOFs in EESs. [ABSTRACT FROM AUTHOR]

High‐voltage aqueous rechargeable energy storage devices with safety and high specific energy are hopeful candidates for the future energy storage system. However, the electrochemical stability window of aqueous electrolytes is a great challenge. Herein, inspired by density functional theory (DFT), polyethylene glycol (PEG) can interact strongly with water molecules, effectively reconstructing the hydrogen bond network. In addition, N, N‐dimethylformamide (DMF) can coordinate with Zn2+, assisting in the rapid desolvation of Zn2+ and stable plating/stripping process. Remarkably, by introducing PEG400 and DMF as co‐solvents into the electrolyte, a wide electrochemical window of 4.27 V can be achieved. The shift in spectra indicate the transformation in the number and strength of hydrogen bonds, verifying the reconstruction of hydrogen bond network, which can largely inhibit the activity of water molecule, according well with the molecular dynamics simulations (MD) and online electrochemical mass spectroscopy (OEMS). Based on this electrolyte, symmetric Zn cells survived up to 5000 h at 1 mA cm−2, and high voltage aqueous zinc ion supercapacitors assembled with Zn anode and activated carbon cathode achieved 800 cycles at 0.1 A g−1. This work provides a feasible approach for constructing high‐voltage alkali metal ion supercapacitors through reconstruction strategy of hydrogen bond network. [ABSTRACT FROM AUTHOR]

Aqueous zinc batteries usher in a renaissance due to their intrinsic security and cost effectiveness, bespeaking vast application foreground for large‐scale energy storage system. However, uncontrolled dendrite growth along with hydrogen evolution severely restricts its reversibility and stability for practical application. Herein, the surface of Zn metal is reconstructed with metallic particles (In, Sn, In0.2Sn0.8) to diminish surface defects and regulate Zn deposition behavior. The alloyed In–Sn greatly activates the Zn surface for lower Zn adsorption energy barrier to expedite plating kinetics and confine Zn aggregation. Dense and uniform deposition of Zn on the reconstructed surface significantly prevents the Zn substrate from dendrites growth for catastrophic damage. Meanwhile, alloy layer embodies high hydrogen evolution overpotential, ensuring high plating and stripping efficiency for Zn anode. Consequently, In0.2Sn0.8 reconstructed surface realizes long‐term lifespan up to 1800 h with low polarization (12 mV) at the condition of 1 mA cm−2 and 1 mAh cm−2. When paired with sodium vanadate (NVO) cathode, the full cell steady operates for a high‐capacity retention of 94.0% after 5000 cycles at 5 A g−1. This study provides new insights into the surface‐defects dependent Zn deposition process and offers a guide for constructing stable surface for dendrite‐free Zn growth. [ABSTRACT FROM AUTHOR]

Highlights: The classification of metal–organic frameworks (MOFs) is summarized: MOFs can be divided into one, two and three dimensions based on the skeletal structure, MOFs can be divided into isoreticular metal organic frameworks, zeolitic imidazolate frameworks, and so on according to the ligand. The preparation methods of MOFs are reviewed, which can be divided into traditional one pot method and the emerging preparation methods. The application of MOF materials, MOF composite materials, and MOFs-derived materials in supercapacitor is emphasized. Exploring new materials with high stability and capacity is full of challenges in sustainable energy conversion and storage systems. Metal–organic frameworks (MOFs), as a new type of porous material, show the advantages of large specific surface area, high porosity, low density, and adjustable pore size, exhibiting a broad application prospect in the field of electrocatalytic reactions, batteries, particularly in the field of supercapacitors. This comprehensive review outlines the recent progress in synthetic methods and electrochemical performances of MOF materials, as well as their applications in supercapacitors. Additionally, the superiorities of MOFs-related materials are highlighted, while major challenges or opportunities for future research on them for electrochemical supercapacitors have been discussed and displayed, along with extensive experimental experiences. [ABSTRACT FROM AUTHOR]

The high‐throughput scalable production of inexpensive and efficient electrode materials at high current densities demanded by industry is a huge challenge for large‐scale implementation of energy storage technologies. Here, inspired by theoretical calculations that a FeS2/TiO2 heterostructure with built‐in electric field (BEF) can reduce the reaction energy barrier and enhance charge transport, the scalable production of cheap FeS2/TiO2 heterostructure is fabricated by utilizing natural ilmenite as precursor, exhibiting excellent electrochemical performances for sodium‐ion capacitors (SICs) anode. Assembling it with activated carbon (AC) cathode for SICs delivers high energy density (73.7 Wh kg−1) and high power density (10 kW kg−1) as well as outstanding cycle lifespan. Impressively, the method breaks through the traditional preparation approach by using natural minerals instead of high‐purity chemical raw materials as precursors for constructing heterojunctions, and price of the mineral is nearly five orders of magnitude lower than that of commercial chemical raw materials with high‐purity, which greatly reduces raw materials cost and is available for mass production. Similarly, the method can be extended to utilize other minerals to construct heterostructures, thus achieving expanded electrochemical performance, which exhibits huge potentials in electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Potassium ion capacitors (PICs) have the potential to combine the advantages of capacitors and batteries, making them promising energy storage substitutes for existing systems. Biomass‐based‐electrodes are very promising materials for potassium storage, however, at present, the acquisition of biomass‐based‐electrodes is mainly dependent on high temperature calcination, which makes the efficient utilization of biomass materials quite challenging. Herein, in accordance with ex‐situ 13C NMR and Raman, a universally directional selection strategy of biomass precursors through an advanced pre‐diagnosis method for calcination intermediates and a sulfur engineering strategy are initially proposed, proving that the carbon materials derived from precursors with fewer aliphatic chains and more aromatic carbons show a higher yield and can be have more K ions inserted. In addition, the evolution mechanism of in‐plane/interlayered CS bonds is thoroughly evaluated. Notably, PICs assembled by such carbon materials as the battery‐type anode, deliver a high energy density of 151 Wh kg‐1 and an ultrahigh power output of 10 kW kg‐1, closing to state‐of‐the‐art values for PICs. This breakthrough opens up a new avenue for targeted design of biomass materials and offers in‐depth insights into the evolution of S‐C bonds, promoting the energy/power density of PICs devices to a higher level. [ABSTRACT FROM AUTHOR]

Nowadays sodium‐based energy storage systems (Na‐based ESSs) have been widely researched as it possesses the possibility to replace traditional energy storage media to become next generation energy storage system. However, due to the irreversible loss of sodium ions in the first cycle, development of Na‐based ESSs is limited. Presodiation, as a strategy of adding excess sodium ions to the system in advance, accomplishes the enhancement of electrochemical performance. In this minireview, different presodiation strategies applied in sodium‐based energy storage systems will be summarized in detail, their functions and corresponding mechanisms will be discussed as well. Furthermore, the current novel application of presodiation method in other aspects of Na‐based ESSs will be mentioned additionally. At last, in the view of present research status of presodiation, issues that can be mitigated are put forward and guidelines are given on how to deliberate in‐depth presodiation technology in the future, dedicating to promote the further development of Na‐based ESSs. [ABSTRACT FROM AUTHOR]

The use of a sacrificial cathode additive as a pre‐metallation method could ensure adequate metal sources for advanced energy storage devices. However, this pre‐metallation technique suffers from the precise regulation of decomposition potential of additive. Herein, a molecularly compensated pre‐metallation (Li/Na/K) strategy has been achieved through Kolbe electrolysis, in which the electrochemical oxidation potential of a metal carboxylate is manipulated by the bonding energy of the oxygen–metal (O–M) moiety. The electron‐donating effect of the substituent and the low charge density of the cation can dramatically weaken the O–M bond strength, further bringing out the reduced potential. Thus, sodium acetate exhibits a superior pre‐sodiation feature for sodium‐ion battery accompanied with a large irreversible specific capacity of 301.8 mAh g−1, remarkably delivering 70.6 % enhanced capacity retention in comparison to the additive‐free system after 100 cycles. This methodology has been extended to construct a high‐performance lithium‐ion battery and a lithium/sodium/potassium‐ion capacitor. [ABSTRACT FROM AUTHOR]

Prelithiation/presodiation techniques are regarded as indispensable procedures in electrochemical energy storage (EES) systems, which can effectively compensate irreversible capacity loss, raise working voltage, and increase Li+/Na+ concentration in the electrolyte. Various prelithiation/presodiation methods have been successfully exploited and a revolutionary impact has been achieved through the utilization of prelithiation/presodiation techniques. It is well acknowledged that different prelithiation/presodiation strategies possess their own specific mechanisms, which play vital roles in the advancement of EES systems. However, there has rarely been systematical reviews about the concept and progress of prelithiation/presodiation techniques. Hence, in this review various prelithiation/presodiation approaches are comprehensively analyzed and summarized, and in‐depth prelithiation/presodiation behaviors and other innovative applications (including optimization of separators, amelioration of binders, regeneration of spent batteries) are discussed in detail. Finally, suggested future directions of prelithiation/presodiation techniques are proposed and it is expected that these prelithiation/presodiation techniques could provide guidance for construction of advanced EES systems and propel the commercialization process with a focus on safety considerations. [ABSTRACT FROM AUTHOR]

High‐capacity cathodes and anodes in energy storage area are required for delivering high energy density due to the ever‐increasing demands in the applications of electric vehicles and power grids, which suffer from significant safety concerns and poor cycling stability at the current stage. All‐solid‐state lithium batteries (ASSLBs) have been considered to be particularly promising within the new generation of energy storage, owing to the superiority of safety, wide potential window, and long cycling life. As the key component in ASSLBs, individual solid electrolytes that can meet practical application standards are very rare due to poor performance. To the present day, numerous research efforts have been expended to find applicable solid‐state electrolytes and tremendous progress has been achieved, especially for garnet‐type solid electrolytes. Nevertheless, the garnet‐type solid electrolyte is still facing some crucial dilemmas. Hence, the issues of garnet electrolytes' ionic conductivity, the interfaces between electrodes and garnet solid electrolytes, and application of theoretical calculation on garnet electrolytes are focuses in this review. Furthermore, prospective developments and alternative approaches to the issues are presented, with an aim to improve understanding of garnet electrolytes and promote their practical applications in solid‐state batteries. [ABSTRACT FROM AUTHOR]

Advanced materials with various micro‐/nanostructures have attracted plenty of attention in energy storage field over the past decades. Metallic reduction reactions (MRRs) possess the merits of low energy consumption, flexibility, convenience, and scalability, which have been considered as potential methods to acquire diverse micro‐/nanostructured materials. In this review, the latest progress of MRRs is systematically summed up, featuring the usage of metallic reductants (e.g., magnesium, aluminum, zinc, lithium) on synthesizing of advanced micro‐/nanostructured materials and their applications in various energy storage systems. The as‐obtained materials (e.g., carbon‐, silicon‐, germanium‐, antimony‐, and titanium‐based materials) can deliver various architectures, including solid spherical structures, hollow porous structures, core–shell structures, yolk–shell structures, core–satellite structures, and many kinds of 1D, 2D, 3D micro‐/nanostructures. Besides, the defect properties of materials can be well tuned via MRRs. The application progress of these materials as active electrodes, host materials, or functional interlayers for lithium ion batteries, lithium sulfur batteries, sodium ion batteries, or supercapacitors is reviewed. In the end, the strengths and insufficiencies of MRRs are discussed and the probable future research directions of MRRs are proposed. [ABSTRACT FROM AUTHOR]

High‐efficiency energy storage technologies and devices have gained numerous attention because of their ever‐increasing requirement. Sodium‐ion capacitors (SICs), as a burgeoning electrochemical energy storage device, combine virtues of rechargeable batteries and electrochemical double layer supercapacitors, delivering both high energy–power density and long cycling life. In the past decades, great efforts have been made to find suitable anode material to conquer the kinetic imbalance between the battery‐type anode with sluggish bulk redox reaction and the capacitor‐type cathode with fast ion absorption/desorption process. By exploring high‐rate performance anode materials, the great reaction kinetic gap between cathodes and anodes can be narrowed down, which directly affects the energy–power densities of SICs. In this article, an overview of advanced battery‐type anode materials is offered for high‐performance SICs with an emphasis on anode structural design and improved energy–power density, including carbonaceous materials, metallic compounds, MXene, organic polymers, and so on. Furthermore, the implementation of presodiation for the sake of optimizing the SICs is also illustrated. Finally, the challenges faced and the perspectives for future developing trends of SICs are discussed. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous zinc-ion batteries are a promising candidate for next-generation energy storage devices. However, their practical application is limited by the severe safety issue caused by uncontrollable dendrite growth on zinc anodes. Here we develop faceted titanium dioxide with relatively low zinc affinity, which can restrict dendrite formation and homogenize zinc deposition when served as the protective layer on zinc anodes. The as-prepared zinc anodes can be stripped and plated steadily for more than 460 h with low voltage hysteresis and flat voltage plateau in symmetric cells. This work reveals the key role of crystal orientation in zinc affinity and its internal mechanism is suitable for various crystal materials applied in the surface modification of other metal anodes such as lithium and sodium. Zinc affinity plays a key role in the zinc plating and stripping processes but its internal mechanism is still unclear. Here, the authors report a protective layer with controllable zinc affinity by adjusting the crystal orientation to suppress the dendrite growth on the zinc anode interface. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries have rapidly developed recently as promising energy storage devices in large‐scale energy storage systems owing to their low cost and high safety. Research on suppressing zinc dendrite growth has meanwhile attracted widespread attention to improve the lifespan and reversibility of batteries. Herein, design methods for dendrite‐free zinc anodes and their internal mechanisms are reviewed from the perspective of optimizing the host–zinc interface and the zinc–electrolyte interface. Furthermore, a design strategy is proposed to homogenize zinc deposition by regulating the interfacial electric field and ion distribution during zinc nucleation and growth. This Minireview can offer potential directions for the rational design of dendrite‐free zinc anodes employed in aqueous zinc‐ion batteries. [ABSTRACT FROM AUTHOR]

Demand for energy in day to day life is increasing exponentially. However, existing energy storage technologies like lithium ion batteries cannot stand alone to fulfill future needs. In this regard, potassium ion batteries (KIBs) that utilize K ions in their charge storage mechanism have attracted considerable attention due to their unique properties and are therefore established as one of the future battery systems of interest among the scientific community. Nevertheless, the development and identification of appropriate electrode materials is very essential for practical applications. This review features the current development in KIBs electrode and electrolyte materials, the present challenges facing this technology (in the commercial aspect), and future aspects to develop fully functional KIBs. The potassium storage mechanisms, evolution of the KIBs, and the advantages and disadvantages of each category of materials are included. Additionally, various approaches to enhance the electrochemical performances of KIBs are also discussed. This review is not only an amalgamation of different viewpoints in literature, but also contains concise perspectives and strategies. Moreover, the potential emergence of a novel class of K‐based dual ion batteries is also analyzed for the first time. [ABSTRACT FROM AUTHOR]

Herein, we report the fabrication and application of Li‐ion anodes for utilisation within Li‐ion batteries, which are fabricated via additive manufacturing/3D printing (fused deposition modelling) using a bespoke graphene/polylactic acid (PLA) filament, where the graphene content can be readily tailored and controlled over the range 1–40 wt. %. We demonstrate that a graphene content of 20 wt. % exhibits sufficient conductivity and critically, effective 3D printability for the rapid manufacturing of 3D printed freestanding anodes (3DAs); simplifying the components of the Li‐ion battery negating the need for a copper current collector. The 3DAs are physicochemically and electrochemically characterised and possess sufficient conductivity for electrochemical studies. Critically, it is found that if the 3DAs are used in Li‐ion batteries the specific capacity is very poor but can be significantly improved through the use of a chemical pre‐treatment. Such treatment induces an increased porosity, which results in a 200‐fold increase (after anode stabilisation) of the specific capacity (ca. 500 mAh g−1 at a current density of 40 mA g−1). This work significantly enhances the field of additive manufacturing/3D printed graphene based energy storage devices demonstrating that useful 3D printable batteries can be realised. [ABSTRACT FROM AUTHOR]

Abstract: Antimony holds a high‐specific capacity as a promising anode material for Na‐ion batteries (SIBs) and much research is focused on solving the poor cycling stability issue associated with its large volume expansion during alloying/dealloying processes. Here, self‐thermal‐reduction method is successfully applied to prepare antimony/carbon rods (Sb/C rods) utilizing potassium antimony(III)‐tartrate (C8H10O15Sb2K2) as a dual source of carbon matrix and metallic antimony. According to theory calculations and experiment results, the formation process is explicitly explored as follows: C8H10O15Sb2K2 → Sb2O3/C → Sb2O3/Sb/C → Sb/C rods. Notably, organic ligands in C8H10O15Sb2K2 can be gradually turned into amorphous carbon with simultaneous reduction of Sb3+ to metal Sb. Moreover, potassium chloride acts as an activator and a template during the course of carbonization, and synchronous reduction is introduced. Consequently, an antimony/carbon electrode material denoted as SbOC/C is formed, exhibiting a unique dual‐carbon‐modified structure and extensive SbOC bridge bonds that give rise to outstanding cycling performance and rate capacity. Specifically, the capacity is maintained at 404 mA h g−1 with 89% retention after 700 cycles at 500 mA g−1. The low‐cost, self‐thermal‐reduction method and excellent electrode performances of electrode material make it attractive for large‐scale energy storage systems. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) metal-organic frameworks (MOFs) exhibit great promise as high-energy anode materials for next-generation lithium-ion capacitors (LICs) due to their tunable chemistry and short ion transport paths. Nevertheless, high-throughput production of ultrathin 2D MOFs and energy storage mechanism analysis are still full of challenges. Here, theoretical calculations indicate that partial introduction of Fe in Co sites can enhance interaction of metal centers with water in solvents due to the strong 3d-2p orbital binding energy, which induces ultrathin nanosheets, resulting in exposure of high-density ligand active sites, lower band gap and higher Young modulus during lithium insertion. Greatly, ultrathin 2D Co/Fe-BDC nanosheets are obtained with a bottom-up method and can be scaled up to high-throughput production. In/ex-situ results further reveal highly reversible insertion/extraction reactions accompanied by crystalline to amorphous for Co/Fe-BDC anodes. LICs with optimal Co 4 Fe-BDC anode deliver high energy density (199.7 Wh kg−1) and power density (10,000 W kg−1), together with superior cycle lifespan. This work offers in-depth insights for the high-throughput synthesis and the storage mechanism in 2D MOFs. [Display omitted] • Ultrathin metal-organic frameworks are synthesized by a stirring method with the potential for scale-up production. • The DFT calculations reveal the introduction of Fe induces 2D stuctures and enhances electrochemical kinetics. • In/ex-situ results indicate Co/Fe-BDC shows the insertion/extraction mechanism accompanied by crystalline to amorphous. • The optimal LICs deliver high energy density (199.7 Wh kg−1), power density (10000 W kg−1) and superior cycle lifespan. [ABSTRACT FROM AUTHOR]

High-rate acetylene black (AB) decorated NiCo 2 S 4 hollow microsphere is prepared via a gas bubble soft template and hydrothermal methodology. Benefiting from the combined advantages of the AB with high conductivity and the nanopetals assembled NiCo 2 S 4 with unique hollow micro-/nano- structures, abundant porosity and high conductivity, the as-obtained composites are found to exhibit high specific capacitances (768 F g −1 at 2 A g −1 ) and remarkable rate capabilities (92.2, 80.1 and 70.3% of capacity retention rate at 20, 50 and 100 A g −1 ). The fabrication mechanism of the AB-NiCo 2 S 4 composite is also proposed. Furthermore, an asymmetric supercapacitor is fabricated by using the AB-NiCo 2 S 4 composite as a positive electrode and activated carbon as a negative electrode. Owing to the excellent electrochemical properties of the AB-NiCo 2 S 4 electrode, the asymmetric device delivers high energy density (24.7 Wh kg −1 ) at a power density of 428 W kg −1 or high power density (17.12 kW kg −1 ) at a reasonable energy density of 7.1 Wh kg −1 , and exceptional cycling stability (105.6% of the initial capacity retention at 5 A g −1 over 5000 cycles). These results above demonstrate the significance and great potential of mesoporous NiCo 2 S 4 hollow microsphere-based composites in the development of high-performance energy-storage systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • All-organic asymmetric supercapacitor device with 1.7 V is demonstrated. • 27 m ammonium and potassium acetate are used as low-cost electrolytes. • ASC device delivers energy & power densities of 22.2 Wh kg−1 and 8.5 kW kg−1. • The device has 79 % of capacity retention after 10,000 charge-discharge cycles. Engineering the polymers with electrochemical functionality is a topic of contemporary research towards developing lightweight and low-cost energy storage devices. In this study, a pair of organic polymers is successfully synthesized by coupling the redox-active moieties such as perylenetetracarboxylic diimide together through monosulfide and disulfide groups. The introduction of two different sulfide linkages in the polymeric chain yields two distinct morphologies due to the different structures of sulfide linkage groups. These polymers are tested as the electrode materials for supercapacitors in two different water-in-salt electrolytes. The interactions of K+/NH 4 + ions with polymer electrodes are separately studied in 27 m potassium acetate (KAc) and 27 m ammonium acetate electrolytes. The polymer with monosulfide moieties shows better specific capacitance, rate capability, and cyclic stability in 27 m KAc compared to the one with disulfide moieties. In order to demonstrate the practical application, the asymmetric supercapacitors are fabricated by using the polymer and activated carbon as the negative and positive electrodes, respectively. The device with 27 m KAc delivers an energy density of 29.9 Wh kg−1 at the power density of 850 W kg−1 and exhibits 79% of the initial capacitance after 10,000 charge-discharge cycles at the current density of 2 A g−1. [ABSTRACT FROM AUTHOR]

Keywords: batteries; electrochemistry; energy storage; presodiation; sodium EN batteries electrochemistry energy storage presodiation sodium 1 1 1 11/24/21 20211122 NES 211122 B Presodiation, known as b pre-doping of sodium ions, represents the addition of sodium sources to ensure adequate sodium content in the sodium-based energy storage systems. In addition, multiple functions of presodiation are clarified, such as compensating for sodium loss, addressing safety issue, enhancing energy density and so on, aiming to promote the development of Na-based energy storage systems. Batteries, electrochemistry, energy storage, presodiation, sodium. [Extracted from the article]

Aqueous all-organic battery-supercapacitor hybrid (BSH) devices are emerging as promising alternative energy storage systems to conventional metal-ion batteries/supercapacitors in terms of their easy processability, high tunability, cost-effectiveness, and recyclability. In this study, we demonstrate an all-organic BSH device using a record concentration of ammonium acetate (30 m NH 4 Ac) as a cheap and green electrolyte. This novel water-in-salt system possesses an electrochemical stability window up to 2.1 V. In addition, organic polymers comprising of perylenetetracarboxy diimide core and the mixed aromatic amine groups are employed as negative and positive electrodes, respectively. The polymers show low water solubility, good crystallinity, and nano-morphology, which make them decent candidates for the all-organic aqueous BSH device. More importantly, electrochemical kinetic analysis of polymer electrodes reveals that the negative and positive electrodes display pseudocapacitive and battery-type behaviors, respectively. For the first time, an all-organic BSH device with 30 m NH 4 Ac is fabricated, which delivers a specific capacity of 42 mA h g−1 at 200 mA g−1 and capacity retention of ca. 63% after 5000 cycles. It further shows the maximum energy density of 16.5 Wh kg−1 and power density of 719 Wh kg−1, depicting great potential in energy storage applications. [Display omitted] • All-organic battery-supercapacitor hybrid device with 1.9 V has been demonstrated • High concentrated aqueous ammonium acetate of 30 m is used as a cheap electrolyte • The hybrid device exhibited the specific capacity of 42 mA h g−1 at 200 mA g−1 • After 2000 cycles of GCD, the hybrid device possessed 60% of capacity retention [ABSTRACT FROM AUTHOR]

Na4Mn1.5Fe1.5(PO4)2P2O7 (NMFPP), with its low cost and high energy density, is essential for accelerating the commercialization of sodium‐ion batteries. However, its practical application is limited by serious voltage hysteresis and detrimental Jahn‐Teller distortions. Herein, a high operating voltage and superior stable Nb‐doped NMFPP with fewer intrinsic anti‐site defects are elaborately designed by the reconstruction of the crystal lattice and electronic distribution. By introducing higher charge density Nb─O bonds, the lengths of Mn‐O bonds are shortened, enhancing lattice stability. As a result, the lattice volume contracted during Na+ extraction/insertion is decreased with niobium‐modified Na4(Mn0.5Fe0.5)2.94Nb0.06(PO4)2P2O7, mitigating lattice distortion from the Jahn‐Teller effect and increasing the capacity retention after 1000 cycles from 57.5% to 82.3%. More importantly, the delayed effect of Mn2+ involvement in redox reactions is significantly reduced, raising the average operating voltage from 3.32 to 3.64 V and increasing the overall energy density by 13%. This study opens new avenues to develop advanced sodium‐ion battery cathode materials with high energy density and long calendar life for energy storage. [ABSTRACT FROM AUTHOR]

Developing novel anodes with outstanding fast‐charging properties is crucial for next‐generation energy storage research. Sb2S3 materials are deemed promising electrodes due to their high theoretical specific capacity. However, they are restricted by sluggish bulk‐phase kinetics, bringing about inferior electronic conductivity at high current density. In this work, the cable‐like SS@C‐x anodes are successfully prepared via the thermal‐chemical treatment method. Through the tailoring of habit modifiers, their unique core–shell architectures are induced with (hk1) preferential planes and the construction of S‐defects, accompanied by lowered energy barriers. Meanwhile, assisted by C─S and C─O─Sb bonds, the charge accumulation on the surface can be rapidly released toward the bulk phase. As expected, for the as‐optimized samples, the capacity of 603.7 mAh g−1 can remain after 100 cycles at 1.0 A g−1. Even at 10.0 A g−1, their superior capacity of 436.1 mAh g−1 can be noted, and it still displayed the reversible capacity of 479 mAh g−1 at −5 °C. Assisted by kinetic analysis, the great electrochemical properties mainly come from the reduced migration energy barriers and accelerated Li+ diffusion rates. Given this, the work is expected to shed light on crystal orientation tuning and defect engineering for advanced metal‐based energy storage materials. [ABSTRACT FROM AUTHOR]

Heteroatom modification represents one of the major areas of carbon materials' research in electrical energy storage. However, the influence of heteroatomic state evolution on electrochemical properties remains an elusive topic. Herein, thiophene‐2,5‐dicarboxylic acid is chemically activated to prepare O,S‐diatomic hybrid carbon material (OS–C). The heteroatoms and carbon matrix coexist in the form of CO/CO and CS/SS bonds, which introduce porous networks to the partially graphitized carbon skeleton and provide abundant active sites for better ion absorption. Moreover, the heteroatoms and carbon matrix are bridged to establish stable pseudocapacitive functional groups like quinoid unit and disulfide bonds, which can be electrochemically converted into benzenoid units and mercaptan anions through Faradaic reactions to further improve the reversible capacity. Combined with the detailed kinetic exploration and in situ investigation of the electrochemical impedance spectra, the energy storage mechanism for lithium/sodium is proposed in the following steps: Faradaic reactions at a higher potential range, energy storage at active sites, and ions intercalation on the graphitized parts in the low‐voltage states. Greatly, the electrode can store lithium up to the capacity of ≈700 mAh g−1, while also delivering ≈330 mAh g−1 of sodium storage, providing lifetimes in excess of thousands of cycles. [ABSTRACT FROM AUTHOR]

Room temperature sodium–sulfur batteries have emerged as promising candidate for application in energy storage. However, the electrodes are usually obtained through infusing elemental sulfur into various carbon sources, and the precipitation of insoluble and irreversible sulfide species on the surface of carbon and sodium readily leads to continuous capacity degradation. Here, a novel strategy is demonstrated to prepare a covalent sulfur–carbon complex (SC‐BDSA) with high covalent‐sulfur concentration (40.1%) that relies on SO3H (Benzenedisulfonic acid, BDSA) and SO42− as the sulfur source rather than elemental sulfur. Most of the sulfur is exists in the form of OS/CS bridge‐bonds (short/long‐chain) whose features ensure sufficient interfacial contact and maintain high ionic/electronic conductivities of the sulfur–carbon cathode. Meanwhile, the carbon mesopores resulting from the thermal‐treated salt bath can confine a certain amount of sulfur and localize the diffluent polysulfides. Furthermore, the CSxC bridges can be electrochemically broken at lower potential (<0.6 V vs Na/Na+) and then function as a capacity sponsor. And the R‐SO units can anchor the initially generated Sx2− to form insoluble surface‐bound intermediates. Thus SC‐BDSA exhibits a specific capacity of 696 mAh g−1 at 2500 mA g−1 and excellent cycling stability for 1000 cycles with 0.035% capacity decay per cycle. The covalent sulfur–carbon complex SC‐BDSA (S, 40.1%) with different chain lengths is prepared. The short‐chain bridges can be electrochemically broken at potential <0.6 V (Na/Na+) and then worked together with the long‐chain units as a capacity sponsor. The R‐SO parts anchor Sx2− to form insoluble surface‐bound intermediates, leading to a special capacity of ≈750 mAh g−1 over 200 cycles. [ABSTRACT FROM AUTHOR]

• The subsurface tailoring manner is used for recycling graphite from spent LIBs. • Optimizing physicochemical behaviors of graphite with the help of ionic liquids. • The RG-2 anode exhibits impressive long-cycle stability and remarkable ICE. • Specific energy-storage mechanisms for different cycling stages are proposed. • The well-prepared anodes provide outstanding economic and environmental values. Captured by the economic value and environmental friendliness, the high-value recycling of spent batteries has been devoted plenty of attention. However, the regenerated graphite is still limited by large anisotropy and inferior rate abilities. Through the tailoring of low-temperature ionic liquid, the further regenerated graphite displayed rich sub-surface pores and improved crystalline degree, bringing about strong wettability and enhanced isotropy. Utilizing as lithium-storage anode, the optimized sample could deliver a capacity of 321 mAh/g after 300 loops at 1.0 C. Even at 2.0 C after 400 cycles, their capacity could also remain about 278 mAh/g. Supported by the detailed kinetic analysis, the abundant pores of sub-surface served significant roles in the enhancements of diffusion/surface-controlling behaviors. Their pre-storage advantages would be beneficial for the alleviation of voltage dropping, resulting in improved rate properties. Meanwhile, its activation energy was calculated at about 14.52 KJ mol−1, revealing its relatively small ion-diffusion energy barrier. More significantly, assisted by economic analysis, its revenue could also reach up to 5700$ t−1, with a promising recycling value. Given this, the work is expected to offer significant cooperative regeneration manners and shed light on the significant effect of sub-surface designing. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-performance cathode materials for all-organic proton full-battery are synthesized. • Organic copolymers of tertiary amines exhibit nanorod-like morphology. • The device delivers energy densities of 33.9 & 9.6 Wh kg−1 at 423 & 1880 W kg−1. • The assembled proton battery can operate even at −25 °C with > 93% of capacity retention. High-performance aqueous all-organic rechargeable batteries are promising candidates for cost-effective, safe, and environment-friendly next-generation energy storage devices. Herein, two organic copolymers with nanorod-like morphology (AN-TA, and AN-PA), composed of different tertiary amines, are synthesized as the cathode material for an aqueous proton battery. The individual copolymer electrodes possess the dominated diffusion-controlled electrode kinetics resulting from the proton insertion/de-insertion along with the surface-controlled processes in 2 M HCl and 2 M H 2 SO 4. Among the two copolymers, AN-PA exhibits the maximum specific capacity of 145 mAh g−1 at 1 A g−1 and then, even at the higher current density of 10 A g−1, it possesses the capacity as 110 mAh g−1 in 2 M HCl. The assembled aqueous proton battery comprising of AN-PA as a cathode delivers the capacity of 80 mAh g−1 at 1 A g−1 in 2 M HCl. The maximum deliverable energy density of 33.9 Wh kg−1 is achieved at the power density of 423 W kg−1. Notably, our proton battery can well operate at the sub-zero temperature of −25 °C with a cell voltage of 1.1 V. More importantly, the device retains 84 % of the initial capacity after 1000 cycles at 2 A g−1 and exhibits the retention of specific capacity of about > 93% when compared to that of room temperature. [ABSTRACT FROM AUTHOR]

The electrochemical performance of the cathode material is influenced by its structure, including morphology, pore size, specific surface area, layer spacing, impurity content, and species. Each of these factors plays a distinct role in the energy storage process of the electrode. The purpose of this review is not only to provide the relationship between the structure and mechanism of cathode materials, but also to provide directional guidance for optimizing electrochemical performance of the materials. [Display omitted] • Critically reviewing the applications of various cathode materials in MIHCs (Li, Na, K and Zn). • Discussing the relationship between material structure and energy storage mechanism. • Summarizing the methods of optimizing electrochemical properties of cathode materials. Metal ion hybrid capacitors (MIHCs) consist of both capacitance-type electrodes and battery-type electrodes, thereby combining the advantages of metal ion batteries and supercapacitors. Nevertheless, the disparity between the specific capacity and rate performance of the cathode and anode materials suggests that the current performance of MIHCs does not meet practical requirements. The performance of MIHCs is affected by the type, composition, and morphology of the cathode material, affirming their essential role as critical components. Therefore, there is a need to concentrate on and discuss the electrochemical properties of electrode materials, as well as strategies aimed at enhancing their electrochemical performance. This article introduces the composition, types, and energy storage mechanisms of MIHCs. Subsequently, a review is conducted on the cathode materials used in lithium, sodium, potassium, and zinc ion capacitors, with emphasis on their physical and chemical properties and the resulting electrochemical performance. Moreover, a comprehensive investigation is conducted to explore effective strategies for enhancing the electrochemical properties of materials, incorporating a substantial number of theoretical calculations and experimental results. Finally, this review provides valuable suggestions for the development and large-scale production of cathode electrode materials for MIHCs (Li+, Na+, K+, and Zn2+), addressing current issues and proposing potential research directions. [ABSTRACT FROM AUTHOR]

The booming development of the lithium-ion battery market has aroused the transformation of people's consumption and life style. As a significant branch of lithium-ion batteries, LiFePO 4 (LFP)-type batteries has been widely employed in electric vehicles and energy storage devices due to its high safety and decent charge-discharge stability. Nevertheless, the resulted massive scrap of LFP batteries will greatly pose environmental threats and waste of resources if appropriate technical means are not adopted. The advanced recycling methods of spent LFP cathode have long been constantly explored in recent years but have not been systematically discussed. Hence, this review comprehensively summarizes the recovery technologies of spent LiFePO 4 cathode in the current status, including traditional pyro-/hydro-metallurgical processes, direct regeneration and other innovative methods, etc. Furthermore, the pretreatment process is also covered to promote all-sided understanding of the development of LFP cathode recovery approaches. Based on the systematic analysis of spent LFP cathode recycling, the future outlook of efficient recycling methods is proposed to promote the sustainable development of spent lithium-ion batteries. Schematic illustration of strategies and characteristics towards spent LFP cathode recycling. [Display omitted] • A comprehensive summary and prospect of spent LFP cathode recycling. • Pretreatment is introduced to ensure deep understanding of recycling implication. • Mainstream recycling technologies of spent LFP battery are reviewed. • Up-to-date novel recycling methods for spent LFP cathode are summarized. • Future challenges and perspectives are proposed to promote efficient recycling. [ABSTRACT FROM AUTHOR]

The structural collapse of manganese-based materials during cycling greatly restricts its development in Sodium-ion batteries (SIBs). Hence, two-phase structures with different manganese valence states are designed based on an alternating voltage approach to mitigate volume expansion via two-phase coordination. Here distinct manganese valence states of precursor are driven via atmosphere. And in the following heat-induced phase transition, the elemental valence state is the decisive key for the structural and compositional evolution. In a batch of synthetic materials, MnO/MnS with bivalent states of manganese performs best as expected. Furthermore, NaPF 6 in DEGDME is taken to replace the traditional carbonate electrolyte which is prone to produce unstable SEI film and leading to polarization. A series of characterization methods confirm that the energy barrier of charge transfer at the interface between electrolyte and electrode is the main factor determining the electrochemical characteristics of the interface and thus the energy storage performance. Ultimately, carbon dots (CDS) with rich functional groups are introduced in an effort to further promote the conductivity of MnO/MnS, and the in-situ generated C-S-Mn bond enhances electrochemical kinetic behaviors. This work provides an approach for designing manganese-based materials and the selection of electrolytes in sodium energy storage. [Display omitted] • MnO/MnS and MnO/MnS@CDS are prepared based on an alternating voltage approach. • The heterostructure shows good sodium storage performance in ether electrolyte. • The SEI film formed in ether electrolyte ensures efficient sodiation dynamics. • In-situ generated C-S-Mn bond elevates pseudocapacitive behavior. [ABSTRACT FROM AUTHOR]

Aiming at the problems of poor cycle stability of carbon-based materials in potassium ion batteries, functionalized nitrogen and sulfur co-doped carbon dots (CDs) are applied to improve the potassium storage performance of electrode materials. In this work, the functionalized CDs are used to regulate the structure and morphology of the polypyrrole in-situ during the polymerization process of pyrrole monomer. Concretely, the original strip-like fibrous polypyrrole can be induced to become bead-like particle with the disappearance of fiber shape, and with the increase of the amount of carbon dots, the active particles increased. Compared with pure polypyrrole derived carbon, the carbon-dot-regulated polypyrrole derived carbon exhibits more excellent cycling performances with a shorter ion transmission and transfer path, more active sites, increased contact area with the electrolyte and improved structural stability. The specific capacity of the carbon anode carbonized from polypyrrole (C-ppy-NSCDs-100) regulated by 100 mg of carbon dots could reach 360.2 mAh g−1 at 0.1 A g−1, showing the application potential of carbon dots in improving electrochemical potassium storage by regulating the morphology of carbon-based materials. Predictably, these unparalleled features of CDs can be expected to inspire more exciting results in potassium-ion energy storage systems. • A series of polypyrrole carbon-based materials were obtained with the inducers of carbon dots. • The C-ppy-NSCDs-100 anode exhibited a specific capacity of 155.4 mAh g−1 at 1.0 A g−1 after 495 cycles. • The introduction of carbon quantum is an effective way to improve electrochemical potassium storage. [ABSTRACT FROM AUTHOR]

By reason of rich sodium resources, sodium-ion batteries have excited enormous consideration for adhibition in the developing energy-storage stations. And not surprisingly, the exploration of cost-effective anode materials for SIBs have been a conspicuous topic. Herein, iron trioxide embedded in the nitrogen-doped carbon matrix with strong oxygen-bridge bonds is synthesized by using the iron based metal organic framework as template. The obtained composite delivers excellent electrochemical properties, such as specific capacity of 473.7 mAh g −1 at the current density of 100 mA g −1 after 100 cycles. Besides, the reversible capacity still remains at 155.3 mAh g −1 at the high density of 4000 mA g −1 . This remarkable sodium-ion storage capability could be attributed to the incorporation of nitrogen atoms into carbon matrix and the strong chemical bonds between iron trioxide and carbon matrix, which can restrain electrode pulverization and also retain an interparticle connection even after long cycling that could offer a good electronic conductive pathway. This engineer strategy for preparing iron trioxide possess strong interfacial interaction with nitrogen-doped carbon matrix can be applied to other metal phosphides and metal oxide materials. [ABSTRACT FROM AUTHOR]

• The working mechanisms of MOFs-derived heterostructures are introduced. • The synthesis strategies of MOFs-derived heterostructures, including precursors design and post-treatments, are described in detail. • The recent developments of MOFs-derived heterostructures in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), lithium-sulfur batteries (Li-S batteries), supercapacitors (SCs), and other energy storage devices are overviewed. • The challenges and future outlook of promising MOFs-derived heterostructures for electrochemical energy storage are concluded. To satisfy the ever-growing demand for electrochemical energy storage devices, significant research efforts have been devoted to developing promising electrode materials and uncovering the energy storage mechanism. Recently, the construction of MOFs-derived heterostructures for electrode materials has received a great deal of attention since it is a reasonable way to optimize energy storage performance by combining the merits of building blocks while neutralizing the drawbacks, which could greatly enhance the capacity and rate performance. Moreover, MOFs-derived heterostructures with highly structurally and compositionally tunable can be easily customized and applied to different electrochemical energy storage devices. In this review, a comprehensive overview on the structural features and mechanism of MOFs-derived heterostructures, including unique pore structure and large surface area, built-in electric fields, and abundant phase boundaries, which could facilitate the penetration of electrolyte, enhance electrical conductivity and promote ion diffusion kinetics, is firstly presented. Thereafter, the classification and synthesis strategies for MOFs-derived heterostructures are also described. Next, the recent progress of MOFs-derived heterostructures in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), lithium-sulfur batteries (Li-S batteries), supercapacitors (SCs), and other energy storage devices are discussed. Finally, the challenges and future outlook of promising MOFs-derived heterostructures for electrochemical energy storage are concluded. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mesoporous sponge-like NFPP@C@rGO caged in cross-linked dual-carbon frameworks was fabricated via a feasible one-step solid state method. • Enhanced electrical conductivity and kinetics at high temperature has been achieved through nanoengineering and interface regulation. • 86.7% capacity retention was obtained after 30,000 cycles at 20 C. • Full cells (NFPP@C@rGO//HC) exhibited outstanding electrochemical performances. Iron-based mixed phosphates sodium ion batteries (SIBs) are promising sustainable storage devices due to the low-costing and non-toxicity characters. Whereas, their real application is seriously restricted by the sluggish Na+ diffusion and inferior intrinsic electronic conductivity. Herein, we propose mesoporous sponge-like structural Na 4 Fe 3 (PO 4) 2 (P 2 O 7) (NFPP) in-situ caged in carbon layer and cross-linked graphene nanosheets (NFPP@C@rGO), toward fast charging and highly stable sodium ion half/full cells in a wide temperature range. This rational strategy gives the cathode superior long-lasting cycling stability, specifically, 86.7 % capacity retention is retained at 20 C for over 30,000 cycles, displaying a capacity loss less than 0.00045 % per cycle. Notably, outstanding thermal stability at 60 °C is achieved and no obvious capacity degradation can be observed after cycling for 200 times at 1 C. Furthermore, the impressive electrochemical performances of full cells are determined, ascribed to the improved electronic conductivity and structural stability (e.g. a small volume change of ∼4.1 % during sodium ion insertion/deinsertion), which is confirmed by in-situ X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements. All the results above prove that the NFPP@C@rGO is of high potential for advanced energy storage system based on its low costs, long-lasting cyclability and excellent thermal stability. [ABSTRACT FROM AUTHOR]

• Anchor-oxygen interface layer is rationally designed. • Interfacial quasicrystal bonding effects are ingeniously aroused. • Formation energy of oxygen vacancy is effectively elevated. • Capacity/voltage fading is significantly mitigated. Sacrificial additive as an electrolyte engineering could regulate the electrode/electrolyte interface for advanced energy storage devices. In particular, the evolution of cathode electrolyte interface (CEI) is closely related with the epitaxial coordination environment of cathode materials. Herein, polarly modulated solvent strategy is successfully achieved, in which the electrochemical oxidation potential of perfluorinated electrolyte with tris(trimethylsilyl)borate additive is manipulated by the polarity of solvent structure. By taking Li-rich Mn-based oxide (LRM) as a model cathode, the interfacial quasicrystal bonding effects are ingeniously aroused between the interfacial lattice oxygen of LRM cathode and anchor oxygen CEI layer. More greatly, the formation energy of oxygen vacancy is effectively elevated by constructing the epitaxially strong covalent B/Si-O bonding, thereby considerably mitigating the lattice oxygen escaping and inhibiting the irreversible phase transformation. Consequently, LRM cathode with robust anchor oxygen CEI renders improved cycling stability after 200 loops with 87.5% capacity retention at 1C as compared to anchor oxygen-free LRM with only 61.9%. Given this, these findings inform new chemical and interface strategies to facilitate the application of high voltage cathodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The voltage failure is reported and suppressed by heterostructure material. • The construction of heterostructure facilitate the migration of sodium ions. • The assembled sodium-ion capacitor delivers high energy and power density. The voltage failure is a widespread problem in electrochemical energy storage. Nevertheless, uncovering the voltage failure mechanism at the molecular level and further solving this problem are still great challenges. Herein, the voltage failure mechanism of SnSe in the ester-based electrolyte is initially revealed and explained by Hard-Soft-Acid-Base (HSAB) theory. Inspired by theoretical calculations that a CoSe 2 /SnSe heterostructure with built-in electric field (BEF) can bring the migration of electrons from the CoSe 2 to SnSe side and result in the conversion of the boundary acid (Sn2+) into a soft acid, an ultra-homogeneous twinned CoSe 2 /SnSe heterostructure is fabricated by employing CoSnO 3 -MOFs as precursor, exhibiting prominent electrochemical performances for sodium-ion capacitors (SICs). Owing to the abundant phase boundaries and BEF, the migration barrier of Na+ decreases from 1.17 eV to 0.39 eV, delivering greatly enhanced charge transport kinetics. Impressively, the SICs assembled by employing this materials as the anode deliver high energy density (146.3 Wh kg−1) and high power density (12 kW kg−1) as well as excellent cycle lifespan, indicating that the voltage failure phenomenon is solved perfectly by the strategy of constructing heterostructures. The work promotes better fundamental understanding of the voltage failure and provides a new strategy to suppress the voltage failure of electrodes, which may also be extended to other electrochemical energy storage system with similar voltage failure phenomenon. [ABSTRACT FROM AUTHOR]

Electrochemically anodic exfoliation of graphite has been developed for nitrogen-doped few-layer graphene sheets (N-FLGS), demonstrating high N-doping levels of 6.05 atom%. The process for the preparation of N-FLGS is involved with the intercalation of glycine anions H 2 NCH 2 COO − into the graphite layers, electro-polymerization of large electro-oxidation products H 2 NCH 2 CONHCH 2 − , and in situ N-doping in the graphite layer. Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy were employed to characterize the structure and properties of the N-FLGS. The as-fabricated N-FLGS utilized as electrode materials for supercapacitor exhibit enhanced electrochemical performance, including excellent cycling stability (the capacitance ratios after 10 000 cycles is 96.1%) and a remarkable rate capability (184.5 F g −1 at 1 A g −1 , 132.7 F g −1 at 50 A g −1 ). [ABSTRACT FROM AUTHOR]

In recent years metal ion capacitors (MICs) and supercapacitors devices have been reported as promising alternatives for energy storage on a large scale. MICs are characterized by superior power density and energy density, combining advantages of metal-ion batteries such as lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, zinc-ion batteries, etc., and those of supercapacitors. Herein we provide a review of recent progress on MICs, focusing on the sodium-ion capacitor (SICs), potassium-ion capacitors (PICs), and zinc-ion capacitors (ZICs); starting from the basic concepts (the perspectives of the design concepts, the configuration of MICs devices, the electrochemical behavior and the energy storage mechanism), the electrode materials and electrolyte systems in details with some examples. The factors impacting the electrochemical performances of the MICs are also provided in this work and end with a conclusion. This review will be helpful for researchers, especially the new researchers in the field of MICs and supercapacitors, to have an overall understanding of MICs and supercapacitors, develop electrochemical storage devices, and respond to the need forenergy storage in electric vehicles and electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

A high-performing electrolyte plays an imperative role in the pursuit of high energy density, green, low-cost, and safe supercapacitors. To this end, a novel deep eutectic solvent (DES) composed of N-methylacetamide and lithium perchlorate has been engineered by the addition of co-solvents including water and N,N -dimethylformamide (DMF). Interestingly, each co-solvent makes a specific contribution to DES performance as water for flame resistance and DMF for antifreeze. The optimized hybrid DES is tested as the electrolyte for symmetric supercapacitors with polyaniline/reduced graphene oxide composite electrodes (PANI-rGO). The hybrid DES with high ionic conductivity imparts a high operation voltage of 2.2 V to devices whereas the PANI-rGO electrode with the pseudocapacitive behavior provides the high capacitances. Due to the above synergistic effects, our device delivers the maximum energy density of 28.2 W h kg−1 at a power density of 1.1 kW kg−1 and shows moderate cyclic stability at room temperature. More importantly, the supercapacitors can well function in a low temperature range from −20 to 25 °C. The device operated at 25 °C achieves the maximum capacitance of 41.9 F g−1 due to improved ionic conductivity of the DES electrolyte. The current study opens a new route towards sustainable and affordable energy storage devices. [Display omitted] • DES electrolyte with N,N -dimethylformamide as co-solvent shows 2.2V window. • PANI-rGO exhibits pseudocapacitive behavior in the hybrid DES electrolyte. • Fabricated symmetric supercapacitor has potential to operate from −20 to 70 °C. • It delivers an energy density of 28.2 W h kg−1 at a power density of 1.1 kW kg−1 [ABSTRACT FROM AUTHOR]

Two-dimensional birnessite-type manganese oxide electrochemically exfoliated from non-van der Waals manganese metal shows superior zinc storage performance. • 2D layered birnessite has been electrochemically exfoliated form bulk Mn metal. • Monolayer and few-layer birnessite sheets can be obtained. • The cation content and layer number of birnessites can be tuned. • The exfoliated birnessite provides superior zinc storage performances. • This method is applicable to producing various 2D layered transition metal oxides. Electrochemical exfoliation of layered van der Waals solids is becoming a promising method for the fabrication of two-dimensional (2D) materials beyond graphene. Nevertheless, most of bulk layered starting solids are semiconductive or even nonconductive, which will reduce the exfoliation efficiency. In addition, the strong bonding interaction between the layers of van der Waals crystal will lead to the incomplete exfoliation. These deficiencies will hinder the application of this method in the synthesis of two-dimensional semiconductive and insulating materials. Herein, one-pot electrochemical potential-cycles exfoliation has been introduced to fabricate nonconductive 2D layered birnessite-type manganese oxide utilizing non-layered metal as starting precursor, demonstrating that monolayer and few layer birnessite sheets can be obtained through tuning the potential sweep rate. More importantly, this strategy promotes a high exfoliation yield up to 96%, which is much higher than that of electrochemical exfoliation of layered precursors. Additionally, this method can overwhelm the drawbacks such as hindrance of intrinsic/contact high resistance and incomplete exfoliation of the layered starting material presented by electrochemical exfoliation of bulk layered van der Waals solids. When utilized as cathode material for Zn-ion batteries, the exfoliated birnessite can deliver a capacity of 325 mAh g−1 at a current density of 200 mA g−1 and achieved capacity retention of 84% over 1000 cycles at 1000 mA g−1. As exfoliation parameters can be manipulated, this effective method is applicable to producing various 2D layered transition metal oxides and layered double hydroxides regardless of electric conductivity, which will contribute to plentiful applications. [ABSTRACT FROM AUTHOR]