Search

Vanadium oxides with fast and stable Zn2+ storage are of great significance to the development of high‐performance aqueous zinc ion batteries (ZIBs), and yet they commonly suffer from structural instability and sluggish diffusion kinetics. Herein, a new "dual‐ion‐in‐sequence" intercalation strategy based on quenching is proposed to address these issues. Interestingly, it is found that the Zn2+ storage mechanism evolves from the common solid‐state ion diffusion kinetic into an intercalation pseudocapacitance as a result of the enlarged interlayer spacing of V2O5. Together with the expanded interlayer spacing arising from the "dual‐ion‐in‐sequence" intercalation, oxygen defects are simultaneously generated at the sub‐surface of the reconstructed Li@MnVO materials. Benefitting from the improved ionic diffusivity, intercalation pseudocapacitance, and fast charge transferability, full cell based on Li@MnVO cathode shows impressive rate capability and excellent cycling stability of 5000 cycles with a high energy density of 253 Wh kg‐1 at 10 A g‐1. More importantly, the capacity can maintain at 125 mAh g‐1 at 4 A g‐1 even under a raised mass loading of 10 mg cm‐2. The proposed "dual‐ion‐in‐sequence" intercalation strategy of manipulating V2O5 structure at atomic scales is a viable pathway for the high‐performance layered metal oxides, not only for ZIBs but also for other energy storage systems. [ABSTRACT FROM AUTHOR]

Cobalt silicate (CoSi) is a promising electrode material for supercapacitors (SCs) and an electrocatalytic material for the oxygen evolution reaction (OER). How to synthesize cobalt silicate with excellent energy storage and OER properties has not been reported and it is a great challenge for researchers to accomplish it. In this work, we find that the electrochemical properties of CoSi are particularly affected by critical factors during the synthesis process. Three types of CoSi compounds are synthesized using Stöber SiO2 as the self-sacrificing template via a hydrothermal reaction. The CoSi compounds generated from different reaction systems have obvious differences in the macrostate, microscopic morphology, composition and valence, leading to different electrochemical performances for energy storage and OER properties. The findings reveal that the differences (especially valence) among CoSi are determined by the formation of the metal source in the reaction system. The specific capacitance of CoSi-3 obtained from the system with basic salts as the metal source is eight times higher than that of CoSi-1 obtained from the system with coordination compounds as the metal source, whereas CoSi-1 has a greater advantage in electrocatalytic activity. This work provides insight for the synthesis of cobalt silicates applied to energy storage and conversion. [ABSTRACT FROM AUTHOR]

The design and preparation of electrode materials with excellent performance is particularly important due to the current global scarcity of energy supplies, especially those using sustainable and renewable materials. In this work, it is first proposed to apply iron silicate (FeSi), which is synthesized using environmentally friendly biomass as a raw material, as an electrode material for supercapacitors (SCs). FeSi is derived from the calcination of reed leaves (RLs) in combination with a hydrothermal method, and spherical FeSi retains the porosity of the RL precursors and shows remarkable electrochemical performance. The specific capacitance of FeSi as a SC electrode can reach 575 F g−1 at 0.5 A g−1 in the voltage window from −1 to −0.5 V. Simultaneously, the FeSi electrode exhibits favorable cycling stability with 76% capacitance retention after 10 000 cycles and outstanding electrical conductivity. This finding provides a novel method of preparing a kind of untapped electrode material, porous FeSi nanoparticles derived from RLs, and the resulting FeSi material shows enormous potential for energy storage via high-performance SCs. [ABSTRACT FROM AUTHOR]

In recent decades, tremendous attention has been paid to the development of new electrode materials with high capacitance to meet the requirements of electrode materials in supercapacitors. Among vanadium oxides, VO2(A) has recently received increasing attention due to its unique layered structure, phase transformation and applications in Li-ion batteries. However, few studies have focused on the electrochemical properties of VO2(A) as electrochemical capacitors. Herein, we develop a facile hydrothermal method to prepare VO2(A)@C core–shell structured composites by carbonization of glucose in the presence of V2O5 nanowires. The electrochemical properties of the VO2(A)@C core–shell composites are investigated as a supercapacitor electrode material for the first time; the composites show excellent pseudocapacitive behavior and display a specific capacitance as high as 179 F g−1 at 1 A g−1. A flexible asymmetric supercapacitor device is fabricated using VO2(A)@C composites and activated carbon and delivers an excellent capacitance of 0.5 F cm−2 at a scan rate of 5 mV s−1. Replacing the aqueous electrolyte with a LiCl/PVA gel electrolyte can efficiently improve the cycling performance to 85% retention after 1600 cycles. The good electrochemical performance of the composites indicates their high potential as electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Inspired by the desire to solve a series of problems such as the easy mottling and peeling of the physically attached artificial interfacial layer on the surface of Zn anode, ZnSiO 3 with a nanosheet morphology was constructed on the surface of Zn foil through the self-growth reaction. The ZnSiO 3 nano-interfacial layer effectively slices the surface of the Zn foil into individual microscopic interfacial layers, and this study provides a new perspective for the interfacial engineering of the protection of Zn anodes. [Display omitted] Among battery technologies, aqueous zinc ion batteries (AZIBs) have hit between the eyes in the next generation of extensive energy storage devices due to their outstanding superiority. The main problem that currently restricts the development of AZIBs is how to obtain stable Zn anodes. In this study, taking the improvement of a series of problems caused by the physically attached artificial interfacial layer on Zn anode as a starting point, a nanosheet morphology of ZnSiO 3 (denoted as ZnSi) is constructed by self-growth on Zn foil (Zn@ZnSi) by a simple hydrothermal reaction. The ZnSi nano-interfacial layer effectively slices the surface of the Zn foil into individual microscopic interfacial layers, constructing abundant pores. The nanosheets of Zn@ZnSi construct rich nanoscale Zn2+ transport channels, which provide higher electron and ion transport paths, thus achieving the effect of effectively homogenizing the electric field distribution and decreasing the local current density. Thanks to its inherent and structural properties, the Zn@ZnSi anode has a high specific capacity and good cycling stability compared with the Zn electrode. The lifetime of the Zn@ZnSi//Zn@ZnSi symmetric cell is much higher than that of the Zn//Zn symmetric cell at 1 mA cm−2. The capacity of the Zn@ZnSi//NH 4 V 4 O 10 full cell can still reach 98 mAh g−1 after 1000 cycles at 1 A/g. The low-cost and scalable synthesis of ZnSi nano-interfacial layer on Zn is expected to provide new perspectives on interfacial engineering for Zn anodic protection. [ABSTRACT FROM AUTHOR]

The presence of VO 3 - promotes the transformation from the α -MoO 3 to the h -MoO 3. Compared to conventional α -MoO 3 and h -MoO 3 , the insertion of VO 3 - helps to improve the zinc storage performance. [Display omitted] Molybdenum trioxide (MoO 3) has been widely studied in the energy storage field due to its various phase states and unique structural advantages. Among them, lamellar α -phase MoO 3 (α -MoO 3) and tunnel-like h -phase MoO 3 (h- MoO 3) have attracted much attention. In this study, we demonstrate that vanadate ion (VO 3 -) can transform α -MoO 3 (a thermodynamically stable phase) to h -MoO 3 (a metastable phase) by altering the connection of [MoO 6 ] octahedra configurations. h -MoO 3 with VO 3 - inserted (referred to as h -MoO 3 -V) as the cathode material for aqueous zinc ion batteries (AZIBs) exhibits excellent Zn2+ storage performances. The improvement in electrochemical properties is attributed to the open tunneling structure of the h -MoO 3 -V, which offers more active sites for Zn2+ (de)intercalation and diffusion. As expected, the Zn// h -MoO 3 -V battery delivers specific capacity of 250 mAh·g−1 at 0.1 A·g−1 and rate capability (73% retention from 0.1 to 1 A·g−1, 80 cycles), well exceeding those of Zn// h -MoO 3 and Zn// α -MoO 3 batteries. This study demonstrates that the tunneling structure of h -MoO 3 can be modulated by VO 3 - to enhance the electrochemical properties for AZIBs. Furthermore, it provides valuable insights for the synthesis, development and future applications of h -MoO 3. [ABSTRACT FROM AUTHOR]

A core–shell V 2 O 5 · n H 2 O@polyaniline composite is fabricated by wrapping, directed against the capacity attenuation brought by structural collapse of V 2 O 5 · n H 2 O. [Display omitted] Aqueous zinc-ion batteries (AZIBs) are regarded as attractive candidates for next-generation energy storage devices. Among various cathode materials, V 2 O 5 · n H 2 O (VOH) possesses a high theoretical capacity but poor cycle stability due to the susceptibility of its open structure to damage by the quick shuttling of Zn2+. Herein, the structural stability of VOH is directly improved by wrapping polyaniline (PANI) on the VOH nanobelts (VOH@PANI). As a cathode material for AZIBs, the VOH nanobelts@PANI core–shell structures exhibit an outstanding cycle stability of 98% after 2000 cycles at 2 A g−1. The improved conductivity and additional energy storage contribution of the PANI endow VOH@PANI with a specific capacity as high as 440 mAh g−1 at 0.1 A g−1, substantially higher than pure VOH (291 mAh g−1). At the same time, high energy and power densities of 349 Wh kg−1 and 3347 W kg−1 are achieved. This work not only demonstrates that p- type doped PANI coatings on VOH can boost the Zn2+ storage of VOH, but also provides a novel method to enhance cathode materials for high electrochemical performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electrochemical performance of VOOH hollow spheres for NH 4 + was evaluated for the first time. • The hollow structure of VOOH facilitates the insertion/extraction of NH 4 +. • Specific capacitance of 221F·g−1 at 0.1 A·g−1 in NH 4 Cl/PVA electrolyte was achieved. • Areal capacitance of VOOH//AC HSC device was 67 mF·cm−2 at 0.147 mA·cm−2. • This study can help fill the gap of low-valence vanadium oxides in NH 4 + energy storage. The performance of vanadium hydroxide (VOOH) in ammonium-ion (NH 4 +) storage is currently unknown and attractive. Herein, low crystallinity VOOH hollow spheres are synthesized by a template-free hydrothermal method for investigating NH 4 +-storage properties. The hollow structure of VOOH, unlike the precursor V(OH) 2 NH 2 solid spheres, promotes NH 4 +-insertion/extraction, resulting in improved NH 4 +-storage performance. The specific capacitance of VOOH hollow spheres is 221 F·g−1 (265 C·g−1) at 0.1 A·g−1. The quasi-solid-state VOOH//AC hybrid supercapacitor (HSC) device exhibits the capacitance of 67 mF·cm−2 at 0.147 mA·cm−2. The above results indicate that VOOH aims to become an excellent electrode material for NH 4 +-storage. [ABSTRACT FROM AUTHOR]

• A nanowire-structured xonotlite (CaSi) is successfully synthesized as the Zn anode protecting layer. • CaSi featuring 4.38 Å nanopore channels can facilitate the desolvation of hydrated Zn2+. • CaSi showing the zincophilic behavior and ion confinement effect to guide inerratic Zn deposition. • The symmetric cell with CaSi coating runs smoothly for 1580 h at a current density of 1 mA cm−2. Aqueous Zn-ion batteries (AZIBs) have garnered huge attention for grid-scale energy storage systems owing to the following advantage: eco-friendliness, affordability, safety, and high specific capacity. Nonetheless, the recyclability is hindered by the corrosion, zinc dendrite and hydrogen evolution reaction. The development of protecting layer for Zn anode is of great meaningful and challenge. In this work, a nanowire-structured xonotlite (calcium silicate hydrate, Ca 6 Si 6 O 17 (OH) 2 , denoted as CaSi) is successfully synthesized by a facile green route and it is used to construct the protecting layer for Zn anode (named as Zn@CaSi), where CaSi functions as an artificial interfacial layer with zincophilic behavior to guide inerratic Zn deposition by the interaction between electrolyte and anode. Owing to the numerous pores of CaSi nanowires, the Zn@CaSi anode offers vast and stable avenues for facilitating the enhancement of Zn2+ deposition kinetics. Regarding the crystal structure, CaSi featuring 4.38 Å nanopore channels can facilitate the desolvation of hydrated zinc ion via the ion confinement effect, therefore effectively inhibiting the hydrogen evolution reaction and accumulation of by-products. Compared to bare Zn, the significant improvement in the overall performance of the Zn@CaSi anode is achieved. The symmetric cell runs smoothly for 1580 h at the current density of 1 mA cm−2, which is approximately 13 times than that of the bare Zn//Zn symmetric cell. The full cell with the enhanced electrochemical performances also demonstrates the CaSi layer can boost the charge transfer and plating/stripping kinetics. Reconstruction of the electrolyte/anode interface using nanowire-formulated CaSi with zincophilic behavior and porous structure is expected to provide new ideas for the engineering of zinc anode interfaces to achieve high-performance AZIBs. [ABSTRACT FROM AUTHOR]

A dual-polymer strategy can greatly boost the electrochemical properties of HVO for ammonium-ion storage since PANI expands the interlayer space and stabilizes the structure of VO layer and PVA gel electrolyte inhibits the electrochemical dissolution and prevents the collapse of PVO crystal structure. [Display omitted] Recently, aqueous rechargeable batteries employing ammonium-ions (NH 4 +) as charge carriers have received increasing interest because of their merits of eco-friendly, low cost and sustainability. However, the supercapacitor based on NH 4 + charge carriers has rarely been reported probably owing to the lack of a suitable system to achieve acceptable capacitance and cycle performance for NH 4 + storage. Herein, we develop a dual-polymer strategy to boost the electrochemical properties of hydrated vanadium oxide (HVO) for outstanding NH 4 + storages based on a supercapacitor. One polymer polyaniline (PANI) is intercalated into the interlayer space of HVO (11.0 Å) to synthesize PANI-intercalation-HVO (PVO) with the expanded interlamellar spacing of 13.9 Å, which enhances the kinetics and stabilizes the structure during the NH 4 + (de)intercalation. The capacitance at 1 A·g−1 is significantly improved from 156F·g−1 (HVO) to 351F·g−1 (PVO). The other polymer polyvinyl alcohol (PVA) is used to get the quasi-solid-state (QSS) PVA/NH 4 Cl electrolyte, in which the cycle stability of PVO electrode is effectively improved. The PVO exhibits the capacitance retentions of 82% after 2000 cycles and 56% after 10,000 cycles, whereas this value is only 29% after 3000 cycles in NH 4 Cl electrolyte. The findings reveal that this strategy can effectively reduce the diffusion resistance of ammonium ions and improve the energy storage efficiency of PVO. The flexible QSS PVO//active carbon hybrid supercapacitor (FQSS PVO//AC HSC) device is assembled and exhibits outstanding capacitance, long cycle stability, good mechanical stability and potential practical applications. This work may open up a new window for the study on the improved electrochemical properties of electrode materials for NH 4 + storage. [ABSTRACT FROM AUTHOR]

MnVOH/rGO with Mn2+ acting as the "spearhead" to connect with the V 2 O 5 · n H 2 O laminates by electrostatic interreaction and rGO improving the conductivity is synthesized and exhibits the enhanced electrochemical properties by their synergic impact. [Display omitted] • Mn2+ act as the "spearhead" to avoid the electrostatic bog for moving Zn2+ ions. • The synergic impact of Mn2+ and rGO makes the electrochemical properties vastly improved. • The Zn//MnVOH/rGO cell behaves good rate performance (∼97% of initial capacity). Vanadium oxides attract much attention and are concerned as one of the most promising cathodes for aqueous zinc-ion batteries (AZIBs) owing to the layered structures. However, their intensive development is limited by the fragile structures and laggard ion-transferring. Herein, Mn2+ inserted hydrated vanadium pentoxide nanobelts/reduced graphene oxide (Mn x V 2 O 5 · n H 2 O/rGO, abbreviated as MnVOH/rGO) was prepared by a simple one-pot hydrothermal process, delivering excellent electrochemical properties for AZIBs. The Zn//MnVOH/rGO cell operates well even at changing current densities over 45 cycles, behaving 361 mAh·g−1 at 0.1 A·g−1, 323 mAh·g−1 as the current density gradually increasing to 2 A·g−1 and 350 mAh·g−1 when gradually back to 0.1 A·g−1 (∼97% of initial capacity). Such a superb cycling and rate performance is ascribed to the unique stable structure with the compact electrostatic attraction between Mn2+ and V 2 O 5 · n H 2 O (VOH) laminate. On the one hand, Mn2+ generates electrostatic network with [VO 6 ] polyhedrons and suppresses the following electrostatic trap for the moving Zn2+. On the other hand, rGO improves the conductivity, endowing the high capacity and energy density. The performance of the MnVOH/rGO cathode exceeds most of vanadium-based cathodes applying in AZIBs and paves the way to the ideal energy storage system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pre-intercalation of NH 4 + in vanadium-oxide host has great influence on its NH 4 + storage properties. • The appropriate quantity of pre-inserted ammonium ions boosts the (de)intercalation of NH 4 +. • NVO-1 (V/N = 5) exhibits a specific capacitance of 341F·g−1 at 0.5 A·g−1 and stable cycle performance. • The areal capacitances of NVO-1//AC HSC device is achieved to be 330 mF·cm−2 at 1 mA·cm−2. Aqueous energy storage systems have garnered significant attention due to their inherent advantages, including low cost, high eco-sustainability, and enhanced safety profiles. Nonmetal ion as a charge carrier is a fascinated paradigm shift just recently. Vanadium-based materials for ammonium ion (NH 4 +) storage have received considerable interest and have been demonstrated to serve as highly efficient NH 4 + (de)intercalation host materials. However, tuning their structure for enhanced NH 4 + storage presents significant challenges. Herein, we report a strategy for the pre-intercalation of NH 4 + in vanadium oxide framework to study on the influence of the amount of ammonium ions on their NH 4 + storage properties. The results from the experiments and density functional theory (DFT) calculations demonstrate that the appropriate quantity of pre-inserted ammonium ions boosts the (de)intercalation of NH 4 + and exhibits the superior electrochemical properties. Moreover, excessive pre-inserted ammonium ions in vanadium oxide framework occupy the active sites for storing NH 4 +, whereas insufficient pre-inserted ammonium ions in vanadium oxide framework do not support the interlayer space enough for rapid (de)intercalation of NH 4 +. All results elucidate that modulating NH 4 + in vanadium oxide framework enables highly efficient aqueous ammonium ion storage for supercapacitors (SCs). At 0.5 A·g−1, the specific capacitance of 341F·g−1 (171 mAh·g−1) and stable cycle performance of nearly 100 % after 10,000 cycles are achieved. The assembled hybrid supercapacitor exhibits the capacitance with 330 mF·cm−2 at 1 mA·cm−2, and energy density with 13.7 Wh·kg−1 at 22.1 W·kg−1, complemented by commendable mechanical durability and energy output characteristics. The profound insights gleaned from this study illuminate the strategic modulation of NH 4 + ions, unveiling the vast potential of vanadium-based materials for efficient NH 4 + storage applications. [ABSTRACT FROM AUTHOR]

Exploring electrode materials with excellent electrochemical performance is the key to the development of applications in energy storage and conversion. Herein, three-dimensional (3D) vanadium sulfide/carbon nanotubes/reduced graphene oxide (VS 4 /CNTs/rGO) composite is synthesized by a simple one–step hydrothermal method. VS 4 short nanorods cover the both sides of the rGO sheets, and CNTs distribute at the edge of the composite to form a sandwich-like structure, which effectively prevents the accumulation of rGO. Due to the special 3D hierarchical structure, VS 4 /CNTs/rGO exhibits a large specific surface area and a rich pore structure, and the addition of CNTs and rGO also improves the electrochemical properties of VS 4. At 1 A·g−1, VS 4 /CNTs/rGO exhibits a capacitance of 497 F·g−1 (1374.0 C·g−1) in the voltage range of −1.4 to 1.4 V, which is much higher than those binary materials including CNTs/rGO, VS 4 /CNTs and VS 4 /rGO. The VS 4 /CNTs/rGO symmetric supercapacitor (SSC) device shows a remarkable electrochemical performance in a large potential window up to 2.2 V. The capacitance of VS 4 /CNTs/rGO SSC device can reach 1003.5 mF·cm−2 (2207.6 mC·cm−2) at 0.5 mA·cm−2, and it exhibits an energy density of 6.75 Wh·m−2 (72.07 Wh·kg−1) at a power density of 1.38 W·m−2 (14.69 W·kg−1). The high capacitance and energy density of the VS 4 /CNTs/rGO composite in the high voltage interval make it as the potential energy storage material. [ABSTRACT FROM AUTHOR]

Fabrication of a novel electrode material with efficient storage mechanism is a desirable strategy to build a better supercapacitors. Herein, a novel intercalation pseudocapacitance material, VO(OH) 2 /CNT binary composite with cross-linked structure, is first successfully synthesized by a facile one-step hydrothermal method. This composite combines the intrinsic positive traits of each component, in which the synergistic efforts greatly enhance to achieve a considerable electrochemical performance. In the three-electrode system, VO(OH) 2 /CNT composite electrode exhibits a capacitance of 256 F·g−1 (512C·g−1) at 0.5 A·g−1 within the wide potential range of −0.8–1.2 V. More remarkably, the VO(OH) 2 /CNT-based flexible symmetric supercapacitor delivers a high energy density of 32.08 Wh·kg−1 at a power density of 63.65 W·kg−1 in a large operating voltage of 2.2 V. As well as, it performs a well cycling stability that the capacitance retention is about 90% after 3000 cycles. For the factual application measurement, two devices in series can light red LED for 5 min after charging 100 s. This work enriches the exploration of vanadium oxyhydroxides' pseudocapaicitance performance, which is of great significance to the future application of vanadium oxyhydroxides in energy storage. VO(OH) 2 /CNT electrode material with cross-linked structure performs the excellent intercalation pseudocapacitance. VO(OH) 2 /CNT flexible SSC device can deliver a high energy density of 32.08 Wh·kg−1 at a power density of 63.65 W·kg−1 in a large operating voltage of 2.2 V. And after charging for 100 s, two devices in series can light red LED for 5 min. Unlabelled Image • A novel VO(OH) 2 /CNT composite with cross-linked structure was synthesized. • VO(OH) 2 /CNT performs intercalation pseudocapacitance. • VO(OH) 2 /CNT as the electrode and device extend the voltage to −0.8~1.2 V and 0~2.2V, respectively. • VO(OH) 2 /CNT SSC device delivers the energy density of 32.08 Wh·kg−1 at 63.65 W·kg−1. • After charging for 100s, two devices in series can light red LED for 5 min. [ABSTRACT FROM AUTHOR]

Vanadium sulfide (VS 4) is recognized as a good anode material for energy storage devices because of its chain-like structure and high content of sulfur. Herein, the patronite VS 4 anchored on carbon nanocubes (denoted as VS 4 /CNTs) with a petal-shape structure consisting of nanolayers is successfully prepared through a one-step hydrothermal reaction. The influence of the optimal ratio of VS 4 and CNTs on the electrochemical properties of VS 4 /CNTs composite is studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The addition of CNTs increases the conductivity and relieves the volume expansion/contraction, resulting excellent electrochemical properties of VS 4 /CNTs. In the potential window of −1.4 V to 1.4 V, the VS 4 /CNTs composite electrode delivers an outstanding specific capacitance of 330 F g−1 (924 C g−1) at 1 A g−1, which is much higher than that of VS 2 with 105 F g−1 (294 C g−1). The VS 4 /CNTs symmetric supercapacitor (SSC) device exhibits the areal capacitance as high as 676 mF cm−2 (1488 mC cm−2) at 0.5 mA cm−2, and the energy density of 4.55 W h m−2 (51.2 W h kg−1) at the power density of 2.75 W m−2 (30.95 W kg−1) within a large voltage up to 2.2 V. All the results confirm that VS 4 /CNTs composite with petal-shape structures is a promising material for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

V 2 O 5 hollow spheres coated Ni-foam (VO-HS/FN) is hydrothermally synthesized by an in-situ strategy and explored as the binder-free electrode for the SSC device for the first time. VO-HS/NF SSC device exhibits excellent electrochemical performance with the specific capacitance of 135 mF·cm−2 at 0.5 mA·cm−2, and the energy density of 356 mW·h·m−2 at the power density of 3.5 W·m−2. • VO-HS/NF is hydrothermally synthesized by an in-situ strategy. • VO-HS/NF is explored as binder-free electrode for SSC device for the first time. • VO-HS/NF SSC device exhibits the excellent electrochemical performance. • VO-HS/NF SSC devices can light red and blue LED. V 2 O 5 hollow spheres coated Ni-foam (VO-HS/NF) is hydrothermally synthesized by an in-situ strategy. Diameter of VO-HS ranges from 300 nm to 500 nm, and the shell thickness is about 40 nm on average. The electrochemical properties of VO-HS/NF electrode demonstrate that it chemically stores charges by redox via the intercalation pseudocapacitance. The symmetrical supercapacitor (SSC) device is assembled using VO-HS/NF as the binder-free electrode and its electrochemical performance is studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). VO-HS/NF SSC device exhibits the pseudocapacitive behavior with specific capacitance of 135 mF·cm−2 at 0.5 mA·cm−2 and energy density of 356 mW·h·m−2 at 3.5 W·m−2 owing to the good ion response and high-quality contact between VO-HS and NF. This work provides an effective and facile strategy for synthesizing additive-free VO-HS/NF as high-performance electrodes for energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spindle-like ferric silicate (s-FeSi) nanoparticles are derived from clay. • The s-FeSi nanoparticles are assembled from nanosheets. • The small size and the layered sub-structure effectively improve the electrochemical performance. • The s-FeSi exhibits a high capacitance of 533 F·g−1 at 1 A·g−1. Cheap and eco-friendly electrochemical materials with high performance have been a critical point of their development. Here, we develop a simple method to prepare ferric silicate as supercapacitor electrodes with good electrochemical performances. Spindle-like ferric silicate (named s-FeSi) nanoparticles, which are composed of stacked nanosheets, are derived from magadiite (mag) through a one-pot hydrothermal method. The nanoparticles are uniform spindle-granule like "rice" with a size of ∼100 nm in length, ∼50 nm in width and composed of layers with a thickness of 3 nm. The layered structure inside nanoparticles significantly enhances the electrochemical performances of s-FeSi with the high specific capacitance of 533F·g−1 at 1 A·g−1 and excellent cycle stability of approximately 100 % retention after 10,000 cycles. This work provides a new route for synthesizing s-FeSi derived from mag for energy storage and opens the use of clay minerals. [ABSTRACT FROM AUTHOR]

Polymer-intercalated vanadium oxide hydrate (VOH) coated on the activated carbon cloth (ACC) as the binder-free ACC@VPP electrode exhibits the excellent NH 4 +-storage performances. [Display omitted] • PEDOT/PSS intercalated vanadium oxide hydrate (VOH) is reported for NH 4 + storage. • PEDOT/PSS effectively increases the interlayer distance of VOH. • The binder-free electrode delivers a specific capacitance of 511 F·g−1 at 0.5 A·g−1. • The insertion/extraction of NH 4 + is accompanied by hydrogen bond formation/fracture. Aqueous energy storage systems based on ammonium-ion (NH 4 +) as charge carrier have attracted increasing interest owing to their great potential for large-scale application. Developing suitable cathodes (especially binder-free electrodes) for excellent NH 4 + storage is still in their infancy. Herein, a binder-free ACC@VPP electrode, activated carbon cloth (ACC) coated by polymer-intercalated vanadium oxide hydrate (VOH), is demonstrated to be an effective cathode to store NH 4 + for the first time. The polymer not only expands V-O interlayer space facilitating rapid ion diffusion, but also benefits VPP coated on ACC. The reversible (de)insertion of NH 4 + is along with hydrogen-bond fracture/formation between NH 4 + and V-O layers, ensuring encouraging electrochemical properties: a high superior capacitance of 511 F·g−1 (170 mAh·g−1) at 0.5 A·g−1 and durable lifetime over 10,000 cycles. The achieved performances exceed the state-of-the-art NH 4 +-hosting materials. Assembled flexible quasi-solid-state hybrid supercapacitor (QSS HSC) device delivers an areal capacitance of 411 mF·cm−2 and energy density of 3.2 Wh·m−2 at 1 mA·cm−2. The performances of the QSS HSC devices in different deformation, series and parallel states show greatly potential practicability in the wearable energy supply. This contribution elucidates a new view to design binder-free electrodes for high-performance aqueous NH 4 +-SCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A double-sandwich-like C@Co,CoO/Co 2 SiO 4 /rGO structure with enhanced performance is prepared. • The intimal rGO plays the role of supporting structure and conductive core for Co 2 SiO 4. • The outer layer C@Co,CoO acts as the protective and conductive carapace for the whole electrode. • C@Co,CoO/Co 2 SiO 4 /rGO achieves the specific capacitance of 360F·g−1 at 0.5 A·g−1 in − 0.4 V ∼ 0.5 V. • C@Co,CoO/Co 2 SiO 4 /rGO delivers super long lifespan with 88 % after 15,000 cycles. The research on developing cobalt silicate (Co 2 SiO 4)-based materials with high energy and power densities for energy storage devices has sprung up in the field of transition metal silicates (TMSs)-type supercapacitors (SCs). However, the electrochemical performances of the reported Co 2 SiO 4 -based materials are not enough desirable owing to the poor conductivity and narrow voltage ranges originated from the intrinsic shortcomings of Co 2 SiO 4. Herein, we design a double-sandwich-like composite, C@Co,CoO/Co 2 SiO 4 /rGO/Co 2 SiO 4 /C@Co,CoO (denoted as C@Co,CoO/Co 2 SiO 4 /rGO) architecture, to improve the electrochemical performance of Co 2 SiO 4 , where, reduced graphene oxide (rGO) is inside, both sides of rGO are coated by Co 2 SiO 4 , and carbon@cobalt/cobalt oxide (C@Co,CoO) are formed on the surface of Co 2 SiO 4. This integrated construction can not only avert the sluggish mass/electron transfer progress caused by the conventional Co 2 SiO 4 , C@Co,CoO and rGO multi-phase mixture system, but also improve the cycle stability by protecting Co 2 SiO 4 from the dissolution and structural collapse during the electrochemical process. As expected, the double-sandwich-like C@Co,CoO/Co 2 SiO 4 /rGO displays promising electrochemical performances. At 0.5 A·g−1, it achieves the specific capacitance of 360 F·g−1 (324 C·g−1) in the potential interval of − 0.4 V ∼ 0.5 V, and super long lifespan with 88 % after 15,000 cycles. Moreover, the hybrid supercapacitor (HSC) device C@Co,CoO/Co 2 SiO 4 /rGO//AC displays the capacitance with 687 mF·cm−2 at 1 mA·cm−2, energy density with 1.373 Wh·m−2 at 1.5 W·m−2, and even shows practical application for lightening the LED bulb. This work provides an idea for the preparation of the integrated double-sandwich-like carbon/TMSs/carbon architecture to boost the electrochemical performance of TMSs. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ammonium vanadium oxide framework (NVO) is reported for NH 4 + storages. • The NH 4 Cl/PVA gel electrolyte can greatly improve the NH 4 + storage performance of NVO. • NVO delivers a specific capacitance of 339 F·g−1 at 0.5 A g−1 in NH 4 Cl/PVA electrolyte. • The mechanism of capacitance upgrade and structure stability using NH 4 Cl/PVA gel electrolyte is discussed. • The flexible NVO//AC HSC is achieved with high capacitance, long lifespan and practical applications. Aqueous energy storage systems show great promise because of their merits of high safety, low cost and environmentally friendliness. Huge efforts, in recent years, have been focused on these systems employing metal cations as charge carriers. In aqueous rechargeable batteries, a paradigm shift has recently moved to nonmetal ions as charge carriers (e.g.: H+, NH 4 +). Herein, we report an ammonium vanadium oxide framework (NVO) displaying excellent NH 4 + storages. The capacitance and cycle performance of NVO are greatly improved using NH 4 Cl/PVA gel electrolyte. In three-electrode configuration, at 0.5 A g−1, the NVO electrode delivers a specific capacitance of 339 F·g−1 (610 C·g−1, 169 mAh·g−1) in NH 4 Cl/PVA electrolyte, which is much higher than the value of 268 F·g−1 (483 C·g−1, 134 mAh·g−1) in NH 4 Cl electrolyte. It shows 71% capacitance retention after 14,000 cycles in NH 4 Cl/PVA electrolyte. The intercalation pseudocapacitance and double layer capacitance are contributed to the charge storage mechanism of NVO. The flexible quasi-solid-state NVO//AC hybrid supercapacitor is assembled and displays outstanding electrochemical performances with high capacitance, long lifespan and practical applications with good mechanical stability and flexibility in various bending states and excellent series and parallel performance. This work not only demonstrates that NVO has great potential for NH 4 + storages, but also sheds a light on NH 4 Cl/PVA electrolyte for flexible aqueous NH 4 +-supercapacitors. [ABSTRACT FROM AUTHOR]

In this work, the V 2 O 5 nH 2 O/rGO-PVA film is synthesized by a one-step hydrothermal method combination with the filtration, and the film exhibits high capacity as free-standing cathode for AZIBs. Recently aqueous zinc-ion batteries (AZIBs) have been widely studied on the aspects of electrode materials and electrolytes, but it is still far from practical application. The limitation of AZIBs is that it is difficult to have both high specific capacity and good cycle stability. Herein, a free-standing cathode V 2 O 5 nH 2 O/reduced graphene oxide-polyvinyl alcohol (denoted as V 2 O 5 nH 2 O/rGO-PVA) film was synthesized by one-step hydrothermal method and vacuum filtration. As the cathode for the coin-typed AZIBs, the V 2 O 5 nH 2 O/rGO-PVA film cathode delivers the ultrahigh capacity of 553 mA h g−1 at the current density of 0.1 A g−1. And the capacity is 194 mA h g−1 at 0.5 A g−1, after 300 cycles, it still remains 152 mA h g−1. At the power density of 183 W·kg−1, the high energy density is calculated as 354 Wh·kg−1 based on the mass of the cathode. The energy storage mechanism was studied by some ex-situ characterizations as well. This work not only proposes a strategy for the synthesis of V 2 O 5 ∙nH 2 O/rGO-PVA film, but also demonstrates that the as-obtained free-standing cathode is beneficial to the assembly of coin-typed AZIBs and exhibits excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

• Co 2 SiO 4 @Ni(OH) 2 core–shell composite is synthesized. • Co 2 SiO 4 @Ni(OH) 2 electrode shows the specific capacitance of 1101 F g−1 at 1 A g−1. • The specific capacitance of Co 2 SiO 4 @Ni(OH) 2 is much higher than Co 2 SiO 4 and Ni(OH) 2. • Co 2 SiO 4 @Ni(OH) 2 can improve the specific capacitance of Co 2 SiO 4. Cobalt silicate (Co 2 SiO 4) have been received increasing attention as the electrode for energy storage devices recently, however, its specific capacitance achieved is far from being desired for supercapacitor electrode. Herein, nickel hydroxide coated on Co 2 SiO 4 nanobelts [denoted as Co 2 SiO 4 @Ni(OH) 2 core–shell structure was synthesized using Co 2 SiO 4 nanobelts as the template to improve electrochemical properties of Co 2 SiO 4. The as-synthesized Co 2 SiO 4 @Ni(OH) 2 displays surface area with 270 m2 g−1. As the supercapacitor electrode, at 1 A g−1, the specific capacitance of Co 2 SiO 4 @Ni(OH) 2 is achieved to be 1101 F g−1, which is superior to that of Co 2 SiO 4 (193 F g−1) and Ni(OH) 2 (380 F g−1). This work demonstrates that Co 2 SiO 4 @Ni(OH) 2 core–shell structure can improve the specific capacitance of Co 2 SiO 4 and it can be considered as a promising candidate for supercapacitor electrode. [ABSTRACT FROM AUTHOR]

(NH 4) 2 V 3 O 8 /C is first reported as a high performing cathode for ARZIBs, and the Zn//(NH 4) 2 V 3 O 8 /C battery exhibits significantly enhanced electrochemical performance with specific capacities of 356 mA h g−1 at 0.1 A g−1, a high rate performance, an excellent cycle lifespan (135 mA h g−1 after 2000 cycles at 1 A g−1) and a high energy density of 334 Wh kg−1 at 294 W kg−1. • (NH 4) 2 V 3 O 8 /C is reported as a high capacity cathode for ARZIBs for the first time. • (NH 4) 2 V 3 O 8 /C is demonstrated to exhibit much enhanced overall electrochemical performance. • Zn//(NH 4) 2 V 3 O 8 /C battery shows excellent cycle lifespan with the capacity of 135 mA h g−1 after 2000 cycles at 1 A g−1. • Zn//(NH 4) 2 V 3 O 8 /C battery delivers a high energy density of 334 Wh kg−1 at 294 W kg−1. Aqueous rechargeable Zn-ion batteries (ARZIBs) are being extensively investigated for large scale energy storage applications owing to their high safety, low cost, sustainability and environmental friendliness. Tremendous attention has been paid to developing the high capacity cathode materials, with stable host structures and fast channels for diffusions of Zn2+ giving rise to high performance. Herein, we report (NH 4) 2 V 3 O 8 nanoparticles encapsulated into amorphous carbon matrix [denoted as (NH 4) 2 V 3 O 8 /C] as a high capacity cathode for ARZIBs, for the first time. It is demonstrated to exhibit much enhanced overall electrochemical performance, including high capacities of 356, 327, 299, 261 and 232 mA h g−1 at 0.1, 0.2, 0.3, 0.4 and 0.5 A g−1, respectively, high rate capacity as well as excellent cycle lifespan with 212 mA h g−1 after 50 cycles at 0.1 A g−1, 201 mA h g−1 after 100 cycles at 0.2 A g−1, and 135 mA h g−1 after 2000 cycles at 1 A g−1, respectively. The Zn//(NH 4) 2 V 3 O 8 /C battery thus assembled delivers a high energy density of 334 Wh kg−1 at 294 W kg−1, which are superior to some of the state-of-the-art cathode materials for ARZIBs. In parallel with the electrochemical performance demonstrated, we have clarified the key reaction mechanisms involved in the reversible (de)intercalation of Zn2+, studied by multiple analytical methods. [ABSTRACT FROM AUTHOR]