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Lithium‐ion batteries (LIBs) have been widely used as a new energy storage system with high energy density and long cycle life. However, the solid electrolyte interface (SEI) formed on the surface of anode consumes excess active lithium during the initial cycle, resulting in an initial irreversible capacity loss (ICL) and reducing the overall electrochemical performance. To solve the critical issue, pre‐lithiation technology has been accepted as one of the most promising strategies. Due to the pre‐lithiated treatment provides additional active lithium to compensate for the ICL and effectively improves initial Coulombic efficiency (ICE), leading to raising the working voltage, increasing the Li+ concentration, as well as improving the energy density and cycle stability of LIBs. In this overview, the causes of ICL in LIBs are analyzed from different perspectives, and various pre‐lithiation strategies are systematically classified and summarized. Finally, some current problems and development prospects in this field are summarized, with prospects for realizing industrialized technologies. [ABSTRACT FROM AUTHOR]

Despite the high energy density of lithium metal batteries (LMBs), their application in rechargeable batteries is still hampered due to insufficient safety. Here, we present a novel flame-retardant solid-state electrolyte based on polyvinylidene fluoridehexafluoropropylene (PVDF-HFP) with nano SiO2 aerogel as an inert filler but Li6.4La3Zr1.4Ta0.6O12 (LLZTO) as an auxiliary component to enhance the ion conductivity. The introduction of SiO2 aerogels imparts the polymer electrolyte with exceptional thermal stability and flame retardancy. Simultaneously, the interaction between hydroxyl groups of SiO2 particles and PVDF-HFP creates a strong cross-linking structure, enhancing the mechanical strength and stability of the electrolyte. Furthermore, the presence of SiO2 aerogel and LLZTO facilitates the dissociation of lithium salts through Lewis acid-base interactions, resulting in a high ionic conductivity of 1.01 × 10−3 S·cm−1 and a wide electrochemical window of ∼ 5.0 V at room temperature for the prepared electrolytes. Remarkably, the assembled Li|Li cell demonstrates the excellent resistance to lithium dendrite and runs stablly for over 1500 h at a current density of 0.25 mA·cm−2. Thus, we prepare a pouch cell with high safety, which can work normally after short-circuiting under the external folding and cutting. [ABSTRACT FROM AUTHOR]

Simultaneously achieving high energy density and high‐power density in energy storage systems is a crucial direction for developing next‐generation energy storage technologies. The high capacity and rapid kinetic performance of rechargeable proton batteries provide an ideal solution for overcoming energy limitation of capacitors and power constraints of traditional metal‐ion batteries. Research efforts primarily concentrated on electrode materials design, understanding the charge storage mechanisms, and exploring the failure mechanisms. While there has been relatively less emphasis on the modifications to electrolytes and electrode‐electrolyte interfaces to enhance overall performance. Summarizing and sorting relevant work is crucial in providing direction and suggestions for future research endeavors. Herein, to improve energy density, power density, and cycle stability of proton batteries, a series of recently published studies on electrolyte and electrode‐electrolyte interfaces are discussed and reviewed. Furthermore, challenges and future directions pertaining to the electrolytes of proton batteries have been identified, offering insights to facilitate the development of proton battery technology. [ABSTRACT FROM AUTHOR]

Highlights: Solvation engineering toward dual-salt electrolyte by fluorosurfactant additive is proposed, which implements the stable interface of electrode/electrolyte coupled with fast ion thermodiffusion, improving the durability and capability of lithium-ion thermoelectrochemical cell. By combining the optimized electrolyte with functional electrodes, as-constructed device exhibits high Seebeck coefficient and energy density based on hybrid mechanisms, which can be extended as self-power supply for smart electronics. Lithium-ion thermoelectrochemical cell (LTEC), featuring simultaneous energy conversion and storage, has emerged as promising candidate for low-grade heat harvesting. However, relatively poor thermosensitivity and heat-to-current behavior limit the application of LTECs using LiPF6 electrolyte. Introducing additives into bulk electrolyte is a reasonable strategy to solve such problem by modifying the solvation structure of electrolyte ions. In this work, we develop a dual-salt electrolyte with fluorosurfactant (FS) additive to achieve high thermopower and durability of LTECs during the conversion of low-grade heat into electricity. The addition of FS induces a unique Li+ solvation with the aggregated double anions through a crowded electrolyte environment, resulting in an enhanced mobility kinetics of Li+ as well as boosted thermoelectrochemical performances. By coupling optimized electrolyte with graphite electrode, a high thermopower of 13.8 mV K−1 and a normalized output power density of 3.99 mW m–2 K–2 as well as an outstanding output energy density of 607.96 J m−2 can be obtained. These results demonstrate that the optimization of electrolyte by regulating solvation structure will inject new vitality into the construction of thermoelectrochemical devices with attractive properties. [ABSTRACT FROM AUTHOR]

Potassium‐ion hybrid capacitors (PIHCs) overcome the limitations of potassium‐ion batteries (PIBs) and supercapacitors (SCs) and integrate the advantages of both, including high energy density, high power density, low cost, long cycle life, and stable electrochemical performance. However, the development of PIHCs is hindered by thermodynamic instability and kinetic hysteresis. Additionally, the dynamic mismatch between anode and cathode materials poses an urgent challenge. To this end, many research works related to material development have been dedicated to overcoming the drawbacks. In this review, the energy storage mechanism of PIHCs is briefly introduced. Moreover, the research progress and achievements of anode and cathode materials in recent years are reviewed, including carbon‐based materials, MXenes, transition metal materials, Prussian blue and its analogues. Finally, the challenges and prospects of PIHCs are proposed, together with guiding significant research directions in the future. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries are recognized as one of the most promising next‐generation energy‐storage technologies owing to their high energy density and low cost. Nevertheless, the shuttle effect of polysulfide intermediates and the formation of lithium dendrites are the principal reasons that restrict the practical adoption of current Li–S batteries. Adjustable frameworks, structural variety, and functional adaptability of covalent organic frameworks (COFs) have the potential to overcome the issues associated with Li–S battery technology. Herein, a summary is presented of emerging COF materials in addressing the challenging problems in terms of sulfur hosts, modified separators, artificial solid electrolyte interphase layers, and solid‐state electrolytes. This comprehensive overview focuses on the design and chemistry of COFs used to upgrade Li–S batteries. Furthermore, existing difficulties, prospective remedies, and prospective research directions for COFs for Li–S batteries are discussed, laying the groundwork for future advancements in this class of fascinating materials. [ABSTRACT FROM AUTHOR]

Proton batteries have been considered as an innovative energy storage technology owing to their high safety and cost‐effectiveness. However, the development of fast‐charging proton batteries with high energy/power density is greatly limited by feasible material selection. Here, the pre‐protonated vanadium hexacyanoferrate (H‐VHCF) is developed as a proton cathode material to alleviate the capacity loss of proton‐free electrode materials during electrochemical tests. The pre‐protonation process realizes fast and long‐distance transport of protons by shortening diffusion path and reducing migration barriers. Benefitting from the enhanced hydrogen bonding network combined with dual redox reactions of V and Fe in protonated H‐VHCF cathode, a high energy density of 74 Wh kg−1 at 1.1 kW kg−1, and a maximum power density of 54 kW kg−1 at 65 Wh kg−1 is achieved for the asymmetric proton batteries coupling with MoO3/MXene anode. Proton transport and double oxidation‐reduction center are verified by theoretical calculations and ex situ experimental measurements. Considering the anti‐freezing availability of proton batteries, 82.5% of its initial capacity is maintained after 10000 cycles under −40 °C at 0.5 A g−1. As a proof‐of‐concept, flexible device fabricated by optimized electrodes and hydrogel electrolytes can power up a light‐emitting diode even under a bent state. [ABSTRACT FROM AUTHOR]

Thermal energy is abundantly available in our daily life and industrial production, and especially, low‐grade heat is often regarded as a byproduct. Collecting and utilizing this ignored energy by low‐cost and simple technologies may become a smart countermeasure to relieve the energy crisis. Here, a unique device has been demonstrated to achieve high value‐added conversion of low‐grade heat by introducing redox‐active organic alizarin (AZ) onto N‐doped hollow carbon nanofibers (N–HCNF) surface. As‐prepared N–HCNF/AZ can deliver a high specific capacitance of 514.3 F g−1 (at 1 A g−1) and an outstanding rate capability of 60.3% even at 50 A g−1. Meanwhile, the assembled symmetric proton capacitor can deliver a high energy density of 28.0 Wh kg−1 at 350.0 W kg−1 and a maximum power density of 35.0 kW kg−1 at 17.0 Wh kg−1. Significantly, the thermally chargeable proton capacitors can attain a surprisingly high Seebeck coefficient of 15.3 mV K–1 and a power factor of 6.02 µW g–1. Taking advantage of such high performance, a satisfying open‐circuit voltage of 481.0 mV with a temperature difference of 54 K is achieved. This research provides new insights into construction of high value‐added energy systems requiring high electrochemical performances. [ABSTRACT FROM AUTHOR]

Metal–oxygen batteries have been growing rapidly as an energy storage technology in light of their high specific energy density. However, waste metal–oxygen batteries will raise many environmental issues; therefore, the recycling and reusing of the spent metal–oxygen batteries has attracted great attention. Herein, we report the 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) as a redox mediator for manganese–oxygen battery (MOB). Trace amounts of PTIO result in the discharge capacity of MOB increase to 2588 mAh g−1 and enhance the formation of manganese dioxide (MnO2) with toroidal appearance and high crystallinity on the cathode. After being used, the dismantled MnO2/carbon nanotube (CNT) cathode can be reused as an electrode for supercapacitor via simple calcining at mild temperature. The recycled free-standing MnO2/CNT electrode demonstrates an exceptional specific capacitance (253.86 F g−1) at a current density of 0.5 A g−1 in a 0.5 M Na2SO4 electrolyte. Moreover, we prepare an asymmetric supercapacitor fabricated with the recycled MnO2/CNT electrode and activated carbon (AC), which exhibits excellent energy density (32.00 Wh kg−1 at 413.70 W kg−1) with 78.26% retention over 6000 cycles. This work provides a promising strategy to derive high-quality and high-value MnO2/CNT electrode materials from the spent MOBs. It's the 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) as a redox mediator for manganese-oxygen battery (MOB). The recycled manganese dioxide (MnO2)/carbon nanotube (CNT) cathode can be reused as an electrode for supercapacitor via simple calcining at mild temperature. The recycled MnO2/CNT electrode shows the toroidal appearance and high crystallinity. Furthermore, the asymmetric supercapacitor fabricated with the MnO2/CNT free-standing electrode displays high specific capacitance, superior energy density, and good cyclic ability. [ABSTRACT FROM AUTHOR]

Recently, developing matchable cathode materials of Zn ion hybrid capacitor still remains difficult owing to insufficient understanding of the charge storage behavior. However, most previous efforts are devoted to explain the effect of oxygen‐containing groups without paying attention to graphitic structure. Herein, the charge storage capability and electrochemical kinetics of reduce graphene oxide (rGO) nanosheets are optimized as a function of their surface properties. Beyond the contribution of oxygen‐containing groups, an extra contribution from the reversible adsorption/desorption of H+ on carbon atom of rGO sheets is confirmed. Electrochemical analysis and density functional theory calculations reveal that H+ induces disruption of π cloud in aromatic domain, accompanied by C sp2‐sp3 re‐hybridization and the distortion/restoration of graphitic structure. The optimal electrochemical performance with a specific capacitance of 245 F g‐1 at 0.5 A g‐1 with 53% retention at 20 A g‐1 is achieved for rGO thermally treated at 200 °C. As a proof‐of‐concept application, the 3D printed rGO electrode delivers a high areal capacitance of 1011 mF cm‐2 and an energy density of 266 μWh cm‐2. The study is believed to broaden the horizons of proton adsorption chemistry and shed light on the design of novel electrode materials. [ABSTRACT FROM AUTHOR]

Electrochemical proton storage provides high energy, fast kinetics, safety, and environmental friendliness for grid‐scale energy storage. However, the development of pseudocapacitive proton supercapacitors with fast chargeability and high stability is still challenging because of the unclear electrochemical reaction mechanism and unsuitable construction strategy. Here it is shown that a multi‐metallic Prussian blue analog—Cu0.82Co0.18HCF, which possesses enhanced electronic structure and ion transport path—can intercalate/de‐intercalate large amounts of proton at high rates. Ion‐induced transformation of magnetism, fast solid‐state proton transport, and reversible insertion/de‐insertion of protons lead to extremely excellent rate capacities and cycling stability for proton storage. An asymmetric pseudocapacitive proton supercapacitor (Cu0.82Co0.18HCF//WO3·nH2O) is fabricated with a voltage window of 1.7 V, delivering a maximum energy density of 35 Wh kg−1 and an energy density of 22 Wh kg−1 at a high power density of 26 kW kg−1. Combining systematical material design and mechanism study, this work not only broadens the preparation of electrode materials but also brings light to the construction of high‐performance devices for efficient proton storage. [ABSTRACT FROM AUTHOR]

Mesocrystals have received intense attention in the electrochemical energy storage field owing to their favourable electronic conductivity, high crystallinity and large specific surface area. However, a critical limitation to the wide applications of mesocrystals is the lack of a facile synthesis approach for high-performance mesocrystals. Here, we report a one-step self-assembly solvothermal method to prepare 3D hierarchical highly-ordered Nb3O7F nanowire cluster mesocrystals (denoted NOF-NCMs), of which the diameter of each nanowire is within 10 nm. Through kinetic analysis, NOF-NCMs can be confirmed to provide unique intercalation pseudocapacitance, enabling rapid charge transfer. When used as an anode material, the NOF-NCM electrode displays a high capacity of ∼356.7 mAh g−1 at 800 mA g−1, excellent rate performance and a long cycle life with ∼88.3% capacity retention after 3000 cycles. The improved electrochemical properties of NOF-NCMs are attributed to the unique highly-ordered nanowire cluster architectures. A lithium ion capacitor (LIC) is constructed by using well-prepared NOF-NCMs as an anode and commercial AC as a cathode. The NOF-NCMs//AC LIC can hold a maximum energy density of 74.5 W h kg−1 at 87.5 W kg−1, and has a long cycle lifespan with a 92.5% capacity retention after 3000 cycles and low self-discharge rate, demonstrating a bright candidate for applications in both high-energy and high-power electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Despite high specific capacity (3860 mAh g−1), the utilization of Li‐metal anodes in rechargeable batteries are still hampered due to their insufficient cyclability. Herein, we report an anion‐receptor‐mediated carbonate electrolyte with improved performance and can ameliorate the solid electrolyte interphase (SEI) composition comparing to the blank electrolyte. It demonstrates a high average Coulombic efficiency (97.94 %) over 500 cycles in the Li/Cu cell at a capacity of 1 mAh cm−2. Raman spectrum and molecular modelling further clarify the screening effects of the anion receptor on the Li+‐PF6− ion coupling that results in the enhanced ion dynamics. The X‐ray photoelectron spectroscopy (XPS) distinguishes the disparities in the SEI components of the developed electrolyte and the blank one, which is rationalized by the molecular insights of the Li‐metal/electrolyte interface. Thus, we prepare a 2.5 Ah prototype pouch cell, exhibiting a high energy density (357 Wh kg−1) with 90.90 % capacity retention over 50 cycles. [ABSTRACT FROM AUTHOR]

Carbon materials are widely used as anodes of supercapacitors due to the long cycling stability, but the low capacitance results in low energy density of the supercapacitor device in aqueous solution, greatly limiting the application field of the supercapacitor. Here, the spiral low-crystalline Ni(OH)2 supported on self-standing layered film structure of N-doped graphene/carbon nanotubes film (NCF) is reported. The prepared flexible film electrode of low-crystalline Ni(OH)2/NCF is functioned as cathode directly, presenting high gravimetric capacitance (GC) and areal capacitance of 2130 F g − 1 (2 A g − 1 ) and 2.88 F cm − 2 (1 A g − 1 ). Also, this self-standing electrode film shows ultra-long cycle life, retaining 111.4% of initial capacitance after 30 000 circles at large current densities (20 A g − 1 ) and almost 0% fade before 10 000 circles. Moreover, Ni(OH)2/NCF and activated polyaniline derived carbon (APDC) have been assembled into an asymmetric supercapacitor, exhibiting a high gravimetric energy density of 60 Wh kg − 1 at 800 W kg − 1 , suggesting that the obtained electrode has a good prospect application in long cycling stability with high energy density of supercapacitor devices. Low-crystalline flower-like Ni(OH)2 nanosheets have been prepared on N-doped graphene/carbon nanotubes film (NCF) by hydrothermal process. The CF with oxygen-containing functional groups can absorb positively-charged Ni2+ through mutual electrostatic interactions. In addition, the introduction of nitrogen can enhance the coupling and electrostatic interaction between Ni(OH)2 and NCF. Therefore, Ni2+ could be easily adsorbed onto the surface of the NCF. The as-synthesized Ni(OH)2/NCF samples exhibited ultra-long cycle life and high specific capacitance. [ABSTRACT FROM AUTHOR]

The serious limitations of MnO2 are poor electrical conductivity and low utilization rate of electrochemical active area. These problems have seriously limited the application of MnO2 aqueous zinc‐ion batteries (AZIBs). Herein, preparing MnO2 uniformly loaded on carbon nanotubes with good electrical conductivity can greatly improve the poor electrical conductivity of MnO2. Moreover, by introducing oxygen vacancy, the surface capacitance, the reaction kinetics, and the electrochemical performance of MnO2 is increased. The specific capacity of the Vo‐MnO2/CNT material is 314 mAh g−1, at 0.2 A g−1, and capacity retention of 81% is achieved after 1000 cycles. In particular, the prepared device presents a distinct energy density of 416.2 Wh kg−1. As a result, the capacity as well as the cycle stability is effectively improved compared with the original MnO2. [ABSTRACT FROM AUTHOR]

Lithium-ion capacitors (LICs) are gradually emerging as one of the most indispensable hybrid energy storage devices. However, it is one main challenge to evade the mismatch of electrochemical kinetics and specific capacity between cathode and anode in LICs. Herein, we have proposed an efficient strategy to prepare the nitrogen-doped hierarchical porous carbon spheres (NHPCS) as cathode, which is synthesized by a simple aerosol-spraying pyrolysis using the low-cost phenolic resin as carbon source without any other catalyst or hard template. The NHPCS exhibits porous nanospheres structure with an appropriate nitrogen doping level (3.65 at.%). Benefitting from the two-pronged strategy of N-doped feature and nanostructure engineering, NHPCS achieves a high specific capacity of 74 mAh g−1 at a current density of 0.1 A g−1 and remains 86.5% of initial capacity even being subjected to a high rate of 50-fold. Furthermore, a high-performance LIC has been developed by coupling NHPCS cathode and hard carbon anode, which delivers a maximum energy density of 151 Wh kg−1 and excellent cycle stability (96.3% capacity retention after 3000 cycles). Significantly, such designed porous carbon could not only be convenient for scalable production, but also be served for many other energy storage devices. We have presented a larger-scale spray pyrolysis strategy to prepare nitrogen-doped hierarchical porous carbon spheres (NHPCS). A high-stable lithium-ion capacitor has been constructed by coupling NHPCS cathode with hard carbon anode, which exhibits a maximum energy density of 151 Wh kg−1 and capacity retention of 96.3% over 3000 cycles, showing great potential for the next-generation energy storage application. [ABSTRACT FROM AUTHOR]

Sodium‐ion capacitors (SICs), designed to attain high energy density, rapid energy delivery, and long lifespan, have attracted much attention because of their comparable performance to lithium‐ion capacitors (LICs), alongside abundant sodium resources. Conventional SIC design is based on battery‐like anodes and capacitive cathodes, in which the battery‐like anode materials involve various reactions, such as insertion, alloying, and conversion reactions, and the capacitive cathode materials usually depend on activated carbon (AC). However, researchers have attempted to construct SICs based on battery‐like cathodes and capacitive anodes or a combination of both in recent years. In this Minireview, charge storage mechanisms and material design strategies for SICs are summarized, with a focus on the battery‐like anode materials from both inorganic and organic sources. Additionally, the challenges in the fabrication of SICs and future research directions are discussed. [ABSTRACT FROM AUTHOR]

Biomass-derived porous carbon materials have been receiving considerable attention in energy-storage devices by virtue of the abundant and renewable sources. In this work, we developed a facile, yet scalable fabrication of nitrogen doping porous carbon (QPC-3) with high specific surface area (SSA) of 2597 m2 g−1 derived from quinoa. The QPC-3 electrode exhibits a special capacitance of 330 F g−1 in 6 M KOH at a density of 1 A g−1 and a good rate capability. Additionally, symmetrical supercapacitors assembled by QPC-3 can deliver capacitances of 254 F g−1 and 99.2 F g−1 at 0.5 A g−1, and the energy densities approach 9.5 Wh kg−1 and 22 Wh kg−1 in aqueous and organic electrolyte, respectively. The results suggest that this quinoa-derived porous carbon could be a promising biomass-derived electrode material applied in high-capacitance supercapacitors. [ABSTRACT FROM AUTHOR]

Aqueous sodium‐ion capacitors (ASICs) are becoming increasingly important due to the remarkable advantages of aqueous electrolyte about the excellent ionic conductivity, non‐flammability and low cost compared with organic systems. But, low capacitance of the electric double‐layer capacitive material and narrow potential window of aqueous electrolyte both have negative effects on the enhancement of energy density. Therefore, we employ typical pseudocapacitive material, layered MnO2/CNTs composite as cathode to fabricate sodium ion capacitor. It needs to be emphasized that the electrochemical process involves two kinds of energy storage mechanisms, such as the reversible Na+ adsorption/desorption onto the surface of each layer and fast Na+ (de)intercalation into the 2D interlayer space. Thus, the composite delivers a high specific capacitance (322.5 F g−1 at 0.5 A g−1) and an excellent cycle stability (5000 cycles with capacitance retention of approximately 90 %). By means of the synergistic effects of the layered MnO2/CNTs cathode, sodium‐ion water‐in‐salt electrolyte (NaWiSE) and polyimide organic anode, the as‐assembled ASIC achieves a high energy density of 78.5 Wh kg−1, accompanied by high power density of 11000 W kg−1 and excellent cycle performance (even 77 % capacity retention after 10000 cycles). Design and charge‐storage mechanism of the present aqueous sodium ion capacitor. [ABSTRACT FROM AUTHOR]

In this contribution, a facile two‐step hydrothermal protocol to prepare hierarchical uniform hollow mesoporous NiCo2S4 microdumbbells (NCS‐MDs) for advanced supercapacitors is developed. Physicochemical investigations reveal that the as‐obtained NCS‐MDs with mesoporous channels in nanoshells possess high‐content Co(III) and Ni(III) species, large surface area (≈80 m2 g−1)/pore volume (≈0.12 m3 g−1), and high tap density (≈0.8 g cm−3). When evaluated as an attractive pseudocapacitive electrode, the unique NCS‐MDs with mass loading of 7 mg cm−2 exhibit remarkable gravimetric/volumetric specific capacitances of ≈912 F g−1 (≈729 F cm−3) at 3 A g−1, and even ≈767 F g−1 (≈613 F cm−3) at high current density of 10 A g−1. Additionally, capacitive degradations of ≈13% and ≈18% are observed over 5000 continous cycles at current rates of 6 and 10 A g−1, respectively. Furthermore, a high‐energy‐density hybrid device is fabricated by using hollow NCS‐MDs and biomass‐derived activated carbon as positive and negative electrodes, respectively, and delivers striking energy density of ≈35.4 Wh kg−1 at power density of ≈381.2 W kg−1, and excellent electrochemical stability at various rates over 11 000 consecutive cycles. These fascinating features strongly highlight that the as‐resulted hollow mesoporous NCS‐MDs could be highly anticipated as a promising electrode platform for next‐generation hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

To push the energy density limit of supercapacitors, a new class of electrode materials with favorable architectures is strongly needed. Binary metal sulfides hold great promise as an electrode material for high-performance energy storage devices because they offer higher electrochemical activity and higher capacity than mono-metal sulfides. Here, the rational design and fabrication of NiCo2S4 nanosheets supported on nitrogen-doped carbon foams (NCF) is presented as a novel flexible electrode for supercapacitors. A facile two-step method is developed for growth of NiCo2S4 nanosheets on NCF with robust adhesion, involving the growth of Ni-Co precursor and subsequent conversion into NiCo2S4 nanosheets through sulfidation process. Benefiting from the compositional features and 3D electrode architectures, the NiCo2S4/NCF electrode exhibits greatly improved electrochemical performance with ultrahigh capacitance (877 F g−1 at 20 A g−1) and excellent cycling stability. Moreover, a binder-free asymmetric supercapacitor device is also fabricated by using NiCo2S4/NCF as the positive electrode and ordered mesoporous carbon (OMC)/NCF as the negative electrode; this demonstrates high energy density (≈45.5 Wh kg−1 at 512 W kg−1). [ABSTRACT FROM AUTHOR]

Highlights: A green water-in-salt electrolyte was developed using lithium acetate as solute with a wide electrochemical stability window of 2.8 V. Molecular dynamics simulation confirmed the nature of water-in-salt electrolyte, where hydrogen bonds of water–water were disrupted and ionic interactions became stronger than dilute solution. Nb18W16O93-based lithium-ion capacitors delivered unexceptionable stability over 50,000 cycles. Aqueous hybrid supercapacitors are attracting increasing attention due to their potential low cost, high safety and eco-friendliness. However, the narrow operating potential window of aqueous electrolyte and the lack of suitable negative electrode materials seriously hinder its future applications. Here, we explore high concentrated lithium acetate with high ionic conductivity of 65.5 mS cm−1 as a green "water-in-salt" electrolyte, providing wide voltage window up to 2.8 V. It facilitates the reversible function of niobium tungsten oxide, Nb18W16O93, that otherwise only operations in organic electrolytes previously. The Nb18W16O93 with lithium-ion intercalation pseudocapacitive behavior exhibits excellent rate performance, high areal capacity, and ultra-long cycling stability. An aqueous lithium-ion hybrid capacitor is developed by using Nb18W16O93 as negative electrode combined with graphene as positive electrode in lithium acetate-based "water-in-salt" electrolyte, delivering a high energy density of 41.9 W kg−1, high power density of 20,000 W kg−1 and unexceptionable stability of 50,000 cycles. [ABSTRACT FROM AUTHOR]

Lithium‐ion capacitors (LICs) are emerging as one of the most advanced energy storage devices by combining the virtues of both supercapacitor and lithium‐ion battery. The key point of constructing high‐performance LICs is to balance the electrochemical kinetics and capacity mismatch between battery‐type anode and capacitive‐type cathode materials. Herein, a strategy is presented for simultaneous manipulation of a MoS2/N‐doped carbon microspheres anode and hierarchical porous carbon cathode by using polyimide precursor. Owing to the fast lithium diffusion rate, high pseudocapacitive behavior, and expanding the interlayer of the MoS2 composite network architecture, the material can achieve excellent rate capacity and cyclic stability. Hierarchical porous carbon has an ultrahigh specific surface area and superior capacitive behavior. A high‐performance LIC is successfully constructed by using the superior anode and cathode materials. The device can deliver a maximum energy density of 120 Wh kg−1 and keep the capacity retention of 85.5% after 4000 cycles, revealing the competition in advanced energy storage devices. Accordingly, the simultaneous manipulation of metal sulfide and hierarchical porous carbon by the same precursor can be used toward fabricating other ideal electrode structures for energy storage. [ABSTRACT FROM AUTHOR]

The 2D carbon sheets have great potential for the construction of compact electrodes with high volumetric performance for electrical double‐layer capacitors (EDLCs), by virtue of their excellent electrical conductivity, high exposed surface area, free of interpores, and unimpeded ion‐diffusion channels. However, 2D nanosheets restack and aggregate during the preparation processes of electrodes, reducing available surface area, and limiting transport of ions. Herein, a facile and scalable method is presented to prepare highly porous crumple carbon balls (PCCBs) assembled by 2D carbon nanosheets. Such a unique nanostructure endows the PCCB electrode with large electrolyte‐accessible surface area and short ion‐diffusion pathways even when compressed at 40 MPa. Electrochemical evaluations in 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte indicate that the compressed PCCB electrodes still show superior gravimetric (103 F g−1) and volumetric capacitances (127 F cm−3) at 1 A g−1. The highest volumetric energy density of symmetrical EDLC based on compressed PCCB‐based electrode is 53.9 Wh L−1. This work provides a new direction for the development of high volumetric energy density carbon‐based EDLCs. [ABSTRACT FROM AUTHOR]

The composite solid electrolyte (TMSB-PVDF-HFP-LLZTO-LiTFSI, PLFB) modified by tris(trimethylsilyl) borate (TMSB) construct a dendrite-free interface and achieve high ion transference numbers at room temperature. Eventually, the PLFB-based solid-state battery assembled by LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode and lithium anode exhibits a high capacity retention of 86% after loop 400 cycles at 0.3 mA cm−2. [Display omitted] Solid-state batteries (SSBs) are considered as the most promising option to replace commercial lithium-ion batteries due to their ability to address the flammability of liquid organic electrolytes and facilitate the energy density of lithium batteries. Herein, by introducing tris(trimethylsilyl) borate (TMSB) as anion acceptors, we successfully develop the light and thin electrolyte (TMSB-PVDF-HFP-LLZTO-LiTFSI, PLFB) with a wide voltage window to couple the lithium metal anode with the high-voltage cathodes. Consequently, as-prepared PLFB can greatly boost the generation of free Li+ and improve the Li+ transference numbers (t Li+ =0.92) at room temperature. Moreover, combined with theoretical calculation and experimental results, the changes in the composition and properties of the composite electrolyte membrane with the addition of anionic receptors are systematically studied, which further implies the intrinsic mechanism of the stability difference. In addition, the PLFB-based SSB assembled by LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode and lithium anode exhibits a high capacity retention of 86% after loop 400 cycles. This investigation on boosted battery performance by immobilized anions not only contributes to the directional construction of dendrite-free and lithium-ion permeable interface, but also brings new opportunities for the screening and design of the next generation of high-energy SSBs. [ABSTRACT FROM AUTHOR]

The Fe 7 Se 8 @NC nanorods were prepared via an in-situ self-polymerization and carbonization-selenization strategy. With the optimization of voltage range and electrolyte parameters, the Fe 7 Se 8 @NC electrode delivers desirable rate capability and long-term cyclability. Coupled with activated carbon (AC), the assembled sodium-ion capacitor (Fe 7 Se 8 @NC//AC) delivers a maximum energy density of 81 Wh kg−1 and remarkable capacity retention of 94.4% after 5000 cycles. [Display omitted] With the associated advantages of low costs and abundant resources, sodium-ion capacitors (SICs) present a suitable means for large-scale energy storage. However, their practical application is still significantly limited by the sluggish electrochemical reaction kinetics of battery-type anodes. Herein, the nitrogen-doped carbon-encapsulated Fe 7 Se 8 nanorods (Fe 7 Se 8 @NC) with a core–shell structure were prepared via an in-situ self-polymerization and carbonization–selenization approach, which improves ion transport and maintains the structural stability of the nanorods. The designed Fe 7 Se 8 @NC nanorods exhibit desirable rate capability with a capacity of 290.7 mAh/g at 10 A/g and long-term cyclability with 84.6 % retention over 6000 cycles at 5 A/g. Moreover, research has shown that the diffusion dynamics of Na+ is improved in ether-based electrolytes and that the irreversible reactions at low voltages can be inhibited by a high discharge cut-off voltage. Furthermore, we demonstrated the specific sodium storage mechanism and excellent electrochemical reversibility of the Fe 7 Se 8 @NC electrode through in-situ and ex-situ characterization techniques. As expected, the assembled SICs with the Fe 7 Se 8 @NC anode and active carbon cathode deliver prominent energy/power densities and an ultra-long cycle life over 5000 cycles, shedding new light on the design of transition metal dichalcogenides as anode materials for advanced energy storage systems. [ABSTRACT FROM AUTHOR]

The low capacitance utilization and capacitance fading of manganese dioxide (MnO 2) is mainly due to poor electro-conductivity and irreversible phase transform. This work proposes a new method of designing hierarchical and binder-free electrode based on MnO 2 material for stable supercapacitor with high specific capacitance. Herein, we fabricated the self-standing electrode of MnO 2 on nitrogen-doped graphene and single wall carbon nanotubes (SWCNTs) self-standing film (NGCF) by electrochemical deposition. As a result, as-prepared MnO 2 /NGCF cathode showed excellent electrochemical performance of 489.7 F g-1 at 1 A g-1. Assembled symmetric aqueous supercapacitor (SC) manifests high voltage of 2.4 V and presents excellent high energy density of 106.7 Wh kg-1 at 1200 W kg-1 and outstanding long-life stability without no decay after 10 000 charge-discharge circuits. This work proposes a new view of designing hierarchical and binder-free electrode with high energy density and long cycling stability based on MnO 2 material for stable symmetric supercapacitor. [ABSTRACT FROM AUTHOR]

Secondary batteries with high energy density, high specific energy and long cycle life have attracted increasing research attention as required for ground and aerial electric vehicles and large-scale stationary energy-storage. Lithium–sulfur (Li–S) batteries are considered as a particularly promising candidate because of their high theoretical performance and low cost of active materials. In spite of the recent progress in both fundamental understanding and developments of electrode and electrolyte materials, the practical use of liquid electrolyte-based Li–S batteries is still hindered by their poor cycling performance and safety concerns. Solid-state Li–S batteries have the potential to overcome these challenges. In this review, the mechanisms of Li ion transport and the basic requirements of solid-state electrolytes are discussed. We focus on recent advances in various solid-state Li–S battery systems, from quasi-solid-state to all-solid-state Li–S batteries. We also describe the remaining challenges and plausible solutions, including improved designs and compositions of electrode materials, solid-state electrolytes and the electrode/electrolyte interfaces. Though many fundamental and technological issues still need to be resolved to develop commercially viable technologies, solid-state Li–S batteries offer an attractive opportunity to address the present limitations. [ABSTRACT FROM AUTHOR]

Developing lithium ion capacitors (LICs) with high energy density is still challenging, due to the kinetic mismatch between the capacitor-type cathode and the battery-type anode. In addition, metal-free LICs are preferred over high-cost and unsustainable metal-containing electrode materials. Exploring appropriate metal-free cathode and anode materials with high capacity and excellent rate performance is one of the keys to attain such goal. Herein, nanoarchitectured graphene-based LICs are successfully constructed by using 2D polydopamine-graphene heterostructured anode and porous graphene cathode. The 2D nature of polydopamine-graphene facilitate the transport of electrolyte ions while graphene promotes electron transfer. The high specific surface area of the porous graphene endows ions with accessibility and fast transport. The metal-free LIC device achieves a high energy density (135.6 Wh kg−1 at 210.4 W kg−1), high power density (21.0 kW kg−1 at 78.9 Wh kg−1), high low-temperature performance (76.4 Wh kg−1 at −20 °C), and reasonably long cycling life. This work provides an effective strategy to design metal-free LIC with high performance at wide temperature range. Image 1 [ABSTRACT FROM AUTHOR]

The defect-rich and N -doped anode was prepared from the renewable sepia by a simple pyrolysis process. The electrochemical kinetic analyses and density functional theory calculations have confirmed its prominent pseudocapacitive behaviors and excellent Li+ storage capability. A high-energy lithium-ion capacitor has been constructed by this low-cost hard carbon anode, which shows great potential for next-generation energy storage device. Lithium-ion capacitors (LICs) are regarded as the most potential devices in the energy storage systems. Unfortunately, the mismatched in the intrinsic kinetics and specific capacities between anode and cathode lead to a depressed electrochemical performance. Thus, designing an advanced electrode material that combines high performance with low-cost is one of the main challenges for LICs, especially in a sustainable anode material until now. Here, a high-energy LIC has been successfully developed using the defect-rich and N -doped hard carbon (DNC) as anode, which is prepared through the carbonization process of the low-cost biowaste sepia without additional template or catalyst. The DNC shows nanospherical structure with a diameter of about 100 nm. Owing to the two-pronged strategy of N -doping and defect engineering, it delivers a high specific capacity (580.3 mAh g−1 at 0.05 A g−1), excellent rate capability, and long cycle stability (1000 cycles). The electrochemical kinetic analysis and density functional theory (DFT) calculations have confirmed its prominent pseudocapacitive behaviors and excellent Li+ storage capability. As expected, the as-fabricated LIC delivers a remarkable energy density (101.7 Wh kg−1), an outstanding rate capability (56.3 Wh kg−1 at 12.5 kW kg−1), and a superior cycle lifespan (3000 cycles), demonstrating the tremendous potential for the next-generation energy storage systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • The HKCO-DANT-COF anode delivers superior electrochemical properties. • 94.4% of capacity is contributed from the ultralong discharged plateau. • The unique proton-dominated charge storage behavior facilitates the fast redox kinetics. • The full batteries show improved energy density of 93.8 Wh kg−1 (based on the total active mass of cathode and anode). Traditional Zn metal anode in aqueous Zn ion batteries (AZIBs) involved the reversible plating/stripping of Zn2+ suffers from dendrite growth, hydrogen evolution reaction (HER), and surface corrosion. Developing organic anode to pair with cathode material is an effective strategy to avoid above challenges. However, the organic anode that hosts the reversible Zn2+ storage has been restrained by low energy density (∼30–60 Wh kg−1) and unstable operated voltage. Herein, for the first time, we report a new polyarylimide covalent organic framework (HKCO-DANT-COF) as organic anode with rich redox active centers, well-ordered pore channels, and extraordinary structural stability, that delivers a considerable specific capacity (256 mAh g−1 at 0.1 A g−1), high-rate performance (147 mAh g−1 even at 10 A g−1) and long cycling stability (over 16,000 cycles). Impressively, 94.4 % of capacity is contributed from its ultralong discharged plateau. The in/ex-situ characterizations and theory calculation are employed to reveal Zn2+/H+ co-storage behavior and stable discharge configuration. More importantly, the rocking-chair AZIBs assembled by HKCO-DANT-COF anode and MnO 2 cathode deliver a superior energy density of 93.8 Wh kg−1 (based on the total active mass of cathode and anode), which is better than the most reported rocking-chair AZIBs. [ABSTRACT FROM AUTHOR]

Conductive polymer and porous carbon hold critical promise as capacitive materials. However, individual use of these materials seriously limits their applications due to poor rate capability and short lifetime or low capacitance. Herein, we successfully fabricate hierarchical polyaniline@N-doped porous carbon (PANI@NPC) double-shell frameworks by in-situ coating of PANI on the NPC surface, and achieve high charge-storage performance. The whole design involves multiple strategies of nanostructurization, constructing hierarchical structure, and hybridization, which will address the above electrochemical concerns. The best specific capacitance for PANI@NPC-2 with 32% NPC reaches 660.0 F g−1 at 0.5 A g−1 and remains 479.8 F g−1 at 5 A g−1, significantly higher that the results of PANI and other hybrids. Moreover, the symmetric supercapacitor using PANI@NPC-2 electrodes demonstrates good performance with an energy density of 8.0 Wh kg−1 at 0.5 A g−1 and a power density of 1750.0 W kg−1 at 10 A g−1. The promoted performance relies largely on the synergy of desirable properties of building blocks in hybrids. This research manifests a general yet efficient method for high-performance hybrid materials for promoting the development of sustainable energy. Display Omitted • Multiple strategies are proposed to design hybrid double-shell 3D frameworks. • Optimal hybrid delivers high capacitance and good rate performance. • The symmetric supercapacitor assembled exhibits high energy and power densities. [ABSTRACT FROM AUTHOR]

Lithium ion capacitors combine the complementary advantageous characteristics of batteries and supercapacitors are expected to deliver both high energy and high power density. However, this technology suffers from the kinetics imbalance between battery electrode and capacitive electrode. Here, two dimensional T -Nb 2 O 5 /N-doped carbon nanosheets with a well-continuous ionic/electronic conducting network demonstrate superior rate capability of 142.3 mA h g−1 at 20 C (1 C = 200 mA g−1). A majority of charge storage in the T -Nb 2 O 5 /N-doped carbon nanosheets was proved to be intercalation pseudocapacitive processes by kinetic analysis, enabling fast charge storage performance. A lithium ion capacitor is based upon these T -Nb 2 O 5 /N-doped carbon nanosheets was successfully fabricated, demonstrating high energy density (70.3 W h kg−1) and high power density (16,014 W kg−1). Unlabelled Image • A well-continuous ionic/electronic conducting network of Nb 2 O 5 /C was rational design and constructed. • The T - Nb 2 O 5 /NC NSs electrode exhibits remarkable rate capability and long cycle life. • T -Nb 2 O 5 /NC NSs//PSC lithium ion capacitor demonstrates high energy density, high power density and long cycle life. [ABSTRACT FROM AUTHOR]

Abstract To obtain high performance supercapacitors suitable for tiny, compact and portable electronic devices, a new type of electrode with high energy density, high speed performance and long cycling-stability is essential. In practical applications, both volumetric capacitance and gravimetric capacitance should be regarded as equally important parameters. Due to their high open surface structures, high compressibility and high conductivity, low-density three-dimensional (3D) carbon scaffolds hold great promise for excellent electrochemical performance, high diffusion rates and low ion transport resistance. Here, a new 3D elastic sponge composed of single-walled carbon nanotubes/graphene (SWNT-rGO-S) was successfully prepared by a superfast and facile flame burning method in an open environment within 20 s. Moreover, the hierarchical NiCo 2 O 4 nanosheets were deposited on the SWNT-rGO-S scaffold through the hydrothermal method and the annealing treatment. Due to the 3D open pore and compositional features, the compressed NiCo 2 O 4 /SWNT-rGO-S electrode exhibits a high gravimetric capacitance of 2050 F g−1 and a volumetric capacitance of 1200 F cm−3, together with a high cycling stability with 115.3% capacitance retention after 6800 cycles at the current density of 20 A g−1 and a high rate performance of 73.2% capacitance retention with the current density being increased from 2 to 80 A g−1. Additionally, a high performance asymmetric supercapacitor was fabricated by using NiCo 2 O 4 /SWNT-rGO-S as the positive electrode and activated polyaniline derived carbon (APDC) as the negative electrode, presenting high gravimetric and volumetric energy densities of 53.5 Wh kg−1 and 26.9 Wh L−1, respectively, and exhibiting a very high 83.5% capacitance retention after 10,000 cycles. Highlights • Carbon nanotube/graphene sponge was prepared by a fast flame burning method. • 3D SWNT-rGO-S could provide fast electron conduction and ion transportation. • Compressible NiCo2O4/SWNT-rGO-S exhibits advanced electrochemical behaviour. • Asymmetric device shows high gravimetric, volumetric energy density with long life. [ABSTRACT FROM AUTHOR]

Given the safety and cost involved, aqueous electrolyte is an extremely attractive candidate for large-scale energy storage systems. However, limited electrochemical stability window of water (decomposition potential <1.23 V) usually confines the energy density of aqueous energy storage systems. Herein, an aqueous electrolyte based on NaClO 4 solution with a high concentration of 17 m is demonstrated to enlarge the practical stability window to approximately 2.75 V, because the scarcity of free water molecules in high salt concentration contributes to their inactivity. An aqueous sodium-ion hybrid capacitor is assembled by using the electrolyte and could be operated at a large voltage of 2.0 V, in which aromatic polyimide (PI) is used as anode material and ultrahigh specific surface PI derived porous carbon microspheres as cathode. This enhanced electrochemical window of the aqueous electrolyte ensures that the sodium-ion capacitor delivers an energy density of 65.1 Wh kg −1 with high power density and good cycle stability. Most importantly, compared to most used host materials with conventional intercalation mechanisms, fast reaction kinetics and structural insensitivity of PI to the ion radius are responsible for the excellent sodium storage properties. [ABSTRACT FROM AUTHOR]

• The synergistic effect exists in V s -NiCo 2 S 4 @NiCoS 2 core-shell electrode materials with interfacial sulfur vacancy modification. • The V s -NiCo 2 S 4 @NiCoS 2 provides a capacitance of 3200 f g −1 with the 1 + 1>2 effect compared to V s -NiCo 2 S 4 and NiCoS 2. • The V s -NiCo 2 S 4 @NiCoS 2 @AC devices deliver up to 46.3 Wh kg−1 energy density at 799.8 W kg−1 power density. Nickel-cobalt based bimetallic sulfide has attracted much attention as positive electrode materials for supercapacitors due to its microstructure designability. However, charge storage occurs mostly on the surface of the material, which limits the full utilization of the active material inside. Here, rich sulfur vacancies modified NiCo 2 S 4 @NiCoS 2 (V s -NiCo 2 S 4 @NiCoS 2) core-shell structures are grown tightly on a nickel foam substrate and prepared as positive material for supercapacitors. The rich sulfur vacancies in the V s -NiCo 2 S 4 "core" increase the electrochemical active sites and electron transport rates, while the amorphous NiCoS 2 "shell" facilitates the rapid diffusion of ions. The results show that V s -NiCo 2 S 4 @NiCoS 2 core-shell structure has a specific capacitance of 3200 F g −1, achieving the effect of "1 + 1>2". The excellent electrochemical performance is attributed to the surface/interface modification of rich sulfur vacancies and the synergistic effect induced by heterogeneous core-shell boundaries. Moreover, the asymmetric supercapacitor V s -NiCo 2 S 4 @NiCoS 2 //AC exhibits an energy density of 46.3 Wh kg−1 and a power density of 799.8 W kg−1, as well as excellent cyclic stability (nearly 80% capacity retention after 10,000 cycles). This work provides a new idea and strategy for core-shell structure design of nickel-cobalt sulfide electrode materials combined with surface/interface modification. Sulfur vacancy modified V s -NiCo 2 S 4 @NiCoS 2 core-shell structure electrode material has been synthesized by hydrothermal, chemical reduction and electrochemical deposition. [Display omitted] [ABSTRACT FROM AUTHOR]

High energy density batteries and high power density supercapacitors have attracted much attention because they are crucial to the power supply of future portable electronic devices, electric automobiles, unmanned aerial vehicles, etc. The electrode materials are key components for batteries and supercapacitors, which influence the practical energy and power density. Metal-organic frameworks possessing unique morphology, high specific surface area, functional linkers, and metal sites are excellent electrode materials for electrochemical energy storage devices. Herein, we review and comment on recent progress in metal-organic framework-based lithium-ion batteries, sodium-ion batteries, lithium-air batteries, lithium-sulfur/selenium batteries, and supercapacitors. Future perspectives and directions of metal-organic framework-based electrochemical energy storage devices are put forward on the basis of theoretical knowledge from the reported literature and our experimental experience. [ABSTRACT FROM AUTHOR]

The manufacturing processes of electrodes have a prominent influence on the cost and performance of lithium-ion capacitors (LICs), which are limited by the conventional wet-coated method due to the usage of solvent. Herein, the solvent-free Li 4 Ti 5 O 12 (LTO) electrodes are prepared with electrostatic spraying deposition using for LICs. Owing to the solvent being avoided during the manufacturing, the dry-sprayed electrode exhibits a higher porosity (∼40%) than that of the wet-coated electrode (∼30%), together with a larger electrochemically active surface area. The optimized microstructure improves electrolyte infiltration and offers effective Li-ion transport paths, which reduces the electrochemical polarization and boosts the specific capacity of the dry-sprayed electrode. When the current density increases from 0.5 C to 10 C, the reversible capacity retention of the dry-sprayed electrode is 74%, which is higher than that of the wet-coated electrode (56%). In addition, the powder resistivity of the dry-sprayed electrode decreases sharply by introducing two-dimension (2D) graphene nanoplate (GN) as the conductive agent, thus side effects have been effectively suppressed during the spraying process. As a result, the assembled LICs using the dry-sprayed LTO electrodes show superior energy density and excellent cycling performance, demonstrating this novel fabrication method has practical application prospects. [Display omitted] • Solvent-free Li 4 Ti 5 O 12 electrodes are prepared by electrostatic spraying. • The differences between dry-sprayed and wet-coated electrodes are explored. • The optimization of electrode microstructure helps properties improve. • Adopting graphene nanoplates as conductive agents perfects spraying results. • Li-ion capacitors with solvent-free electrodes exhibit better performance. [ABSTRACT FROM AUTHOR]

In recent years, transition metal sulfides, especially nickel-cobalt sulfide materials play a crucial role for supercapacitor applications. In this work, the Ni 5 P 2 @Ni 9 S 8 /CoS 1.097 (Ni-P@NCS) core-shell material has been synthesized by simply phosphating the nickel mesh and subsequent electrodeposition of NCS to obtain a nanosheet heterostructure on nickel foam. The Ni-P@NCS composite material has a higher gravimetric capacitance of 2445.7 F g−1 than pure Ni-P of 1116.6 F g−1 and NCS materials of 1104.3 F g−1 at 1 A g−1. At the same time, Ni-P@NCS electrode yields excellent cycling stability (91.4% capacitance retention after 5000 charge–discharge cycles). An asymmetric supercapacitor (ASC) device assembled from Ni-P@NCS and activated carbon electrodes can deliver a highest energy/power density of 42.8 Wh kg−1/799.8 W kg−1, with 94.3% capacitance retention after 10,000 cycles at 5 A g−1. The improvement of electrochemical performance makes it possible to use it as an electrode material. • The Ni 5 P 2 @Ni 9 S 8 /CoS 1.097 electrode has high specific capacitance, working potential window. • The Ni 5 P 2 @Ni 9 S 8 /CoS 1.097 composite material has a higher gravimetric capacitance of 2445.7 F g-1. • The potential window of Ni 5 P 2 @Ni 9 S 8 /CoS 1.097 //AC is 0–1.6 V and the energy density is 42.8 Wh Kg-1. [ABSTRACT FROM AUTHOR]

Because carbon based supercapacitor electrode has low energy density, so birnessite electrode material has attracted more and more attention due to its low cost, environmental friendliness, high oxygen evolution potential and high theoretical specific capacitance. In this work, novel nanoneedle-like rGO/V-Na x MnO 2 /CC cathode material with oxygen vacancies has been prepared, where rGO and CC represent reduced graphene oxide and carbon cloth, respectively. By using surface-protection strategy and introduction of abundant oxygen vacancies, high capacitance of rGO/V-Na x MnO 2 /CC is obtained with 362.5 F g−1 at 1 A g−1. After the current density increases to 24 A g−1, the capacitance retention is 56.56%, presenting excellent rate performance. In addition, after 10,000 charge/discharge cycles at 5 A g−1, the capacitance retention rate is 90.17%, showing excellent cycle stability. The aqueous asymmetric supercapacitor (ASC) of ACMK-3 // rGO/V-Na x MnO 2 /CC has a wide potential window of 0 ~ 2.5 V. And the energy density is as high as 72.2 Wh kg−1 at 1254 W kg−1. After 10,000 charge-discharge cycles at 4 A g−1, the ASC still remains a capacitance retention rate of 88.5%. This work provides a facial method to improve electrochemical properties and shed a light on fabricating a novel cathode for aqueous supercapacitors. ● The rGO/V-Na x MnO 2 /CC electrode with high specific capacitanceand high rate capability has been prepared. ● The cover of rGO and introduction of oxygen vacancies make Na x MnO 2 /CC high specific capacitance and high rate capability. ● ACMK-3//rGO/V-Na x MnO 2 /CC delivers a high energy density of 72.2 Wh kg−1 under the wide potential window of 0–2.5 V. [ABSTRACT FROM AUTHOR]

Nickel cobalt sulfur is attracting more attention due to its great electrical conductivity and high specific capacitance for faraday pseudo-capacitors. Here, by evaporation-induced drying, heterostructure NiS 2 /NiCo 2 S 4 nanosheets on self-supporting substrate of nitrogen-doped single-walled carbon nanotubes sponge (NSCS) are obtained with the sponge volume significantly being reduced. With the electrode film thickness being 80 μm, the as-prepared heterostructure NiS 2 /NiCo 2 S 4 /NSCS electrode shows outstanding areal/gravimetric/volumetric capacitance of 10.5 F cm−2/2905 F g−1/1307.2 F cm−3 at 1 A g−1. With the increase of current density from 1 to 60 A g−1, the current retention rate maintains at 61%. When the active material loading is increased to 14 mg cm−2, the gravimetric capacitance can still maintain at 1725 F g−1, indicating the high ratio performance. After 10,000 cycles, the capacity retention still remains 83% at current density of 10 A g−1. In addition, an asymmetric supercapacitor (ASC) delivers have high gravimetric/volumetric energy density of 58.1 W h kg−1/52.3 W h L−1 with excellent cycle stability after 20,000 cycles. Therefore, the electrode material with high loading and high rate performance can be realized by this method. • By evaporation-induced drying, the volume of NiS 2 /NiCo 2 S 4 /NSCS shrinks obviously. • The electrode has high areal and volumetric capacitance with high loading. • Heterostructure material of NiS 2 /NiCo 2 S 4 greatly improves the electrochemical performance. • The asymmetric supercapacitor delivers high gravimetric/volumetric energy density. [ABSTRACT FROM AUTHOR]

Abstract: In the work, we developed an aqueous symmetric Ru–Cr binary oxide (Ru0.83Cr0.17O2·nH2O)-based electrochemical capacitor (EC) with unwonted high operating voltage in 1M KOH aqueous solution. Electrochemical performance of the symmetric EC was investigated by current-potential response and galvanostatic charge–discharge techniques. Electrochemical data demonstrated that the symmetric EC with a specific capacitance (SC) of ca. 148Fg−1 surprisingly can operate in a large electrochemical window of 1.4V in 1M KOH electrolyte, ensuring that the symmetric EC delivered an energy density of ca. 40Whkg−1. Moreover, the extended cycle life and good power property were obtained meanwhile, indicating that the Ru0.83Cr0.17O2·nH2O-based EC is a promising candidate for aqueous symmetric devices with high energy density and desirable power property. [Copyright &y& Elsevier]

• A copper hyperaccumulator is used to synthesize nanoporous carbon. • The structure of nanoporous carbon was rationally optimized. • Nanoporous carbon anode shows a capacitance-dominated dynamic process. • High specific surface area carbon cathode reveals a high specific capacity. • A high energy Li-ion capacitors with dual carbon configuration has been assembled. Biomass-based porous carbons as electrode materials in asymmetric Li-ion capacitors (LICs) have shown broad prospect application. In this work, one kind of copper hyperaccumulator-elsholtzia splendens was selected as biomass source to synthesize micro-/nanoporous carbons to be used as both anode and cathodefor LICs due to the need of waste disposal. On the basis of separate charge storage mechanisms of anode and cathode in this system, corresponding strategies were adopted to rationally optimize the microstructure of micro-/nanoporous carbons to promote their electrochemical performance. Electrochemical tests showed that hierarchical porous carbon microsphere (PECS) anode exhibited an excellent rate capability (215.6 mA h g−1 at 2 A g-1) and a long lifespan (87.1% capacity retention over 1000 cycles). Carbon cathode with an ultrahigh specific surface area of 2819 m2 g-1 revealed a high specific capacity of 90.9 mA h g−1 at 5 A g-1. Benefiting from the high rate capability of anode and the high specific capacity of cathode, the as-assembled LIC delivered a high energy density of 129.4 W h kg−1 and 51.9 W h kg−1 at a power density of 205.5 W kg−1 and 10.3 kW kg−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • An eco-friendly yet facile approach is proposed to fabricate nano porous fibers. • The porous carbon fibers exhibit satisfactory electrochemical performance. • A high-performance supercapacitor is constructed. Recently, tremendous attention has been paid to carbon-based fibers, particularly porous carbon fibers (PCFs), because of their great potential as electrodes for advanced supercapacitors (SCs). However, the relatively complex preparation and monotonous pore structure are still the most important challenge that PCFs needs to counter. In this work, an eco-friendly yet facile approach has been applied to synthesis PCFs with tunable multi-level pores and satisfactory electrochemical performance. By using the combinations of electrospinning technology, hard-template method and carbonization process, nanofibers with interconnected multi-level pores can be achieved. It is demonstrated that the pore engineered PCF possesses enhanced electrochemical performance. For instance, the PCF electrode possesses a high capacitance of 211 F g−1 in 6 mol L−1 KOH at a density of 0.5 A g−1 together with excellent rate capability. Meanwhile, a high areal capacitance of 1.2 F cm−2 also can be achieved at a mass loading of 10 mg cm−2. Additionally, symmetrical supercapacitor assembled by PCF electrodes exhibits good capacitance of 101.9 F g−1 at the current density of 0.5 A g−1, such device also can deliver an energy density up to 60.1 Wh kg−1 with ionic liquid electrolyte. [ABSTRACT FROM AUTHOR]

[Display omitted] • New hybrid system adopts lithium/sodium mixed organic solvent as electrolyte. • The potential window of LTO MS L/SIB system is broadened. • A four-step charge storage mechanism is proposed. • New hybrid supercapacitors (LTO MS//PSC L/SIC) show excellent electrochemical properties. Reportedly, Li 4 Ti 5 O 12 could provide the novel characteristics of both Li+ insertion and Na+ insertion. In this work, we firstly take advantage of this unique feature and use lithium/sodium mixed organic solvent as electrolyte for evaluating the electrochemical performance of as-synthesized Li 4 Ti 5 O 12 nano-microspheres (LTO MS). As a result, the potential window of LTO MS is broadened, leading to full utilization of Li 4 Ti 5 O 12. In addition, the difference between insertion potentials of Li+ and Na+ inserting into LTO MS is applied to reasonably intercept the potential windows of LTO MS, ensuring its remarkable cycling stability and high rate property. Therefore, LTO MS using lithium/sodium mixed electrolyte (LTO MS-L/SIB system) can provide a broadened potential window of 0.4–2.5 V, leading to a high specific capacity without sacrificing rate performance and cycling stability. We also systemically analyze the charge storage mechanism of LTO MS-L/SIB by ex-situ XRD technologies. For the first time, the lithium-sodium hybrid ion capacitor (LTO MS//PSC L/SIC) is constructed with LTO MS as anode, peanut shell derived carbon (PSC) as cathode, and lithium-sodium mixed organic solvent as electrolyte. Compared with the as-constructed lithium ion capacitors (LTO MS//PSC LIC) and sodium ion capacitors (LTO MS//PSC SIC), LTO MS//PSC L/SIC device provides the highest gravimetric energy density of ~65.3 Wh kg−1, a remarkable cycling stability, and an ultra-low self-discharge rate. [ABSTRACT FROM AUTHOR]

The development of carbon materials with large specific surface area (SSA) and abundant porosity is very essential to construct high-performance supercapacitors. In consideration of the superiority of polymer-based carbon sources on structure and yield, herein, a unique organic polymer is selected to prepare hierarchical porous carbon material, where the key to converting polymer into porous carbon is to combine the activation process of potassium hydroxide with ammonia, which not only relieves the porosity collapse, but also introduces heteroatoms in the carbon matrix. By adjusting temperature, the optimized porous carbon achieves a high SSA of 3270 m2 g−1, a large pore volume of 2.74 cm3/g, and an appropriate nitrogen-doping level of 2.81%. Benefiting from the favorable structure and interface features of the polymer-derived porous carbon electrode, the as-fabricated symmetric supercapacitor exhibits excellent electrochemical performances (184 F g−1 at 0.5 A g−1 and capacity retention of 72% at 10 A g−1) in an ionic liquid-based electrolyte. Meanwhile, the assembled supercapacitor delivers an ultrahigh energy density (92.2 Wh kg−1 is achieved at 950 W kg−1), together with a long cycling life (capacity retention of 90.2% after 30,000 cycles). More importantly, such devices in series can light up the logo made of forty LED lights, showing great potential as a power-type device in practical application. We present a novel strategy by using the porous organic polymers-derived hierarchical porous carbon as electrode material to construct an ionic liquid-based surpercapacitor, which delivers a maximum energy density of 92.2 Wh kg−1 and capacity retention of 90.2% over 30,000 cycles. Unlabelled Image • A unique organic polymer was employed to prepare hierarchical porous carbon with ultrahigh surface area. • Excellent performances in both capacitance and ratability were achieved for the porous carbon. • The as-constructed supercapacitor shows a great practical potential along with long-term durability. [ABSTRACT FROM AUTHOR]

The electrochemical performance of NiCo 2 O 4 currently still faces inherently limited active sites and less available surface areas, hindering its application as the pseudocapacitive electrode in supercapacitors. Accordingly, the cross-linked NiCo 2 O 4 nanosheets with low crystallinity and rich oxygen vacancies on nickel foam (Pd–NCO/NF) by introducing noble metal palladium (Pd2+) has been fabricated. The results show that the lattice orientation of NiCo 2 O 4 nanoparticles is disordered by Pd doping, leading to a decrease in crystallinity. In addition, low crystallinity with a large number of lattice boundaries results in the high electrochemical activity with 2484.4 F g−1. At high current density of 10 A g−1, the capacitance retention could remain 95% after 8000 cycles. An asymmetric supercapacitor of Pd–NCO/NF//activated polyaniline derived carbon (APDC) demonstrates high energy density of 47.5 W h kg−1 at 425.4 W kg−1 and promotes excellent cycle stability, with a capacity retention rate of 86% after 10,000 cycles. • The NiCo 2 O 4 nanosheets present low crystallinity and abundant rich vacancies after introduction of noble metal palladium. • The Pd-NCO/NF exhibits both long cycle life and excellent high gravimetric capacitances. • An assembled asymmetric supercapacitor (ASC) demonstrates high energy density and high capacity retention rate. [ABSTRACT FROM AUTHOR]