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Spinel Ni-dopped MnCo 2 O 4 powder with fast Li + intercalation pseudocapacitance is prepared from transition metal carbonates of Ni, Co and Mn as precursors through a solvothermal synthesis followed by an annealing treatment. As-made products are nanovoids submicron-spheres (the diameter is 500 nm–700 nm) with an obvious yolk-shell structure and uniform elements distribution. As an anode material with fast Li + intercalation pseudocapacitance for lithium-ion battery (LIB), the Ni-dopped MnCo 2 O 4 submicron-spheres exhibit an impressively first discharge efficiency (70%) and outstanding large-current cycling performance. The excellent electrochemical performance is closely ascribed to Li + intercalation pseudocapacitance and the yolk-shell structure, which can effectively prevent the particles from being pulverized, and alleviate the volume changes of particles during the cycling process. In addition, the doping of Ni metal element to MnCo 2 O 4 greatly enhances the electrochemical stability of MnCo 2 O 4 , due to the complementarities and synergies between the three metallic elements during the process of Li insertion or extraction reactions. [ABSTRACT FROM AUTHOR]

Aqueous electrolytes are important charge transport media in various electrochemical applications. However, the water splitting seriously limits the operation voltage of aqueous electrolytes. Thus, further widening the electrochemical stability window (ESW) of aqueous electrolytes is great of importance. Here, based on the high charge density and high electro-negativity of halogen anions (F-), we proposed a "cation/anion with co-solvation" type 16 m KF aqueous electrolyte that can achieve a high conductivity of 196 mS cm−1, a record 3.4 V ESW based on stainless steel mesh and even 6.72 V ESW based on Al metal electrode that is much higher than the highest value currently reported. Such excellent feature is attributed to the strong hydrogen bonds between the F- anions and the water molecules at high concentrations. This work is helpful to provide a new path for design of ideal high-voltage aqueous electrolytes and to understand the important role of anions in aqueous electrolytes at the molecular level. A new "cation/anion with co-solvation" type 16 m KF aqueous electrolyte with a record high ESW of 6.72 V has been developed, which could be attributed to its unique bulk/interface structure constructed by the strong hydrogen bonds between anion and water. [Display omitted] • Developed a new "cation/anion with co-solvation" type 16 m KF aqueous electrolyte. • The electrolyte has record voltage window of 6.72 V based on Al. • The electrolyte has high conductivity of 196 mS cm−1. • Pointed out the important role of the strong hydrogen bonds. • Revealed the unique transformation of the bulk/interface structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • A low-cost NaClO 4 -based water-in-salt electrolyte enabled the controllable EC exfoliation of graphite. • The structure of NaClO 4 -based solutions studied by Raman spectroscopy and DFT-MD simulations. • The amount of free water determines the EC exfoliation behaviors of graphite. Development of aqueous electrolytes in anodic electrochemical (EC) exfoliation is regarded as the preferred choice to prepare single or few layered graphene. Generally, in diluted aqueous electrolytes, however, the uncontrollable decomposition of water often provides excess driving forces, leading to the low ratio of single/few layered graphene nanosheets. Here, we employed a low-cost sodium perchlorate (NaClO 4)-based water-in-salt electrolyte (WIS) for the controllable EC exfoliation of graphite. Benefiting from the high salt-to-water ratio of the electrolyte, their thickness and oxidation extent of the resultant graphene nanosheets were able to be effectively controllable. Moreover, density-functional-theory-based molecular dynamics (DFT-MD) simulations exhibit a revolution from free water to bound water in WIS electrolytes as the salt-to-water ratio increases. Combined with the deconvolution peaks of the Raman spectra, the results further disclose that only at high concentration, free water molecules can be effectively restricted in WIS electrolyte, and they need to overcome more hindrance to arrive at the electrode surface for EC exfoliation than that in dilute electrolytes, therefore, the reaction rate of EC exfoliation can be controlled easily by reducing the amount of free water. Overall, this work demonstrated that controllable graphite exfoliation by changing the decomposition activity of water molecules. [ABSTRACT FROM AUTHOR]

Abstract: In this study, graphene multilayer films with controlled thicknesses deposited on indium tin oxide glass substrates were fabricated using electrostatic layer-by-layer self-assembly of negatively charged graphene oxide followed by hydrazine hydrate reduction. X-ray diffraction spectroscopy, Raman spectroscopy, UV–vis spectroscopy, field emission scanning electron microscopy and atomic force microscopy were used to characterize the microstructures and morphologies of the as-fabricated multilayer films. The supercapacitive properties of the multilayer film electrodes were investigated via cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrometry in a 0.5M Na2SO4 electrolyte. The graphene multilayer films employed as the electrode materials not only exhibited nearly rectangular cyclic voltammetry curves at an exceedingly high scan rate of 2000mV/s, but also exhibited highly linear and symmetrical charge/discharge curves, which indicated that they have ideal electric double-layer capacitive behavior. Furthermore, the supercapacitive performance of the as-prepared graphene multilayer films exhibited a strong dependence on the number of self-assembled layers. Moreover, the specific capacitance per surface area for each self-assembled graphene film exhibited almost no decay after 1500 cycles, implying excellent stability and reversibility. These electrochemical tests indicated that the as-prepared graphene films have great potential for supercapacitor applications. [Copyright &y& Elsevier]

As an emerging multivalent-ion-based energy storage device, aqueous zinc-ion capacitors (AZICs) combine the merits of zinc-ion batteries with high energy density, excellent safety, low cost and environmental friendliness, and the advantages of supercapacitors with high power density and superior cycling performance. Therefore, AZICs have been considered as a new promising electrochemical energy storage system. Though great progress of AZICs has been made recently, they are still in the infant stage and face many challenges. Specially, the unsatisfactory energy density needs to be improved to realize their practical applications, which calls for high-capacity cathode materials. In this review, after a brief introduction of progress and mechanism for AZICs, we provide a systematical overview of the latest advances in the state-of-art cathode materials. The synthesis route, structure and morphology, electrochemical performance, energy storage mechanism as well as the merits and drawbacks of various cathode materials are comprehensively compared and discussed. Finally, a summary and outlook of the challenges and future perspectives of AZICs were presented. With these, this review might offer some guidance for the future design of dedicated novel cathode materials to realize the great potential of AZICs. In this review, we provide a systematical overview of the latest advances in the state-of-art electrode materials for aqueous zinc-ion capacitors (AZICs). The synthesis routes, structure and morphology, electrochemical performance, energy storage mechanism as well as the merits and drawbacks of various cathode materials are comprehensively compared and discussed. In the end, a summary and outlook of the challenges and future perspectives of AZICs are presented. [Display omitted] [ABSTRACT FROM AUTHOR]

Zinc-ion batteries, known for safety and efficiency, are a hotspot in electrochemical energy storage field. Nonetheless, the emergence of dendrites on zinc anodes during electrochemical cycles can lead to capacity attenuation and even failure, particularly under low temperatures. In this study, we develop a novel dendrite-free and low-temperature resistant Zn(ClO 4) 2 /Li 2 SO 4 /Dimethyl sulfoxide (DMSO) hybrid electrolyte by using DMSO as a hydrogen bond acceptor and solvation regulator. Our research demonstrates that, by reducing the desolvation energy barrier of the Zn2+ solvation sheath and the nucleation overpotential of Zn deposition, DMSO effectively inhibits zinc dendrites and side reactions. Furthermore, DMSO disrupts hydrogen bonding between water molecules, preventing electrolyte freezing at low temperatures. As a result, at 0.5 mA cm−2, the Zn||Zn symmetric device using this hybrid electrolyte exhibits consistent operation for over 4000 h even at -25 °C, featuring a minimal deposition/dissolution overpotential of approximately 0.045 mV. Additionally, at -20 °C, the Zn||Zn(ClO 4) 2 -Li 2 SO 4 -DMSO||LiFePO 4 battery demonstrates stable cycling for over 600 cycles at 0.6 C (1 C = 170 mA g − 1), delivering a capacity of 103 mA h g−1. [ABSTRACT FROM AUTHOR]

Aqueous zinc ion chemistry is the hot topic of new energy storage technologies nowadays for its high intrinsic safety as well as its advantages in terms of environmental protection and price. However, the freezing of water at low temperatures limits the practical application to a broad range of temperatures. Herein, in view of the disturbing effect of Mg(ClO 4) 2 on hydrogen bond of water molecules, a novel anti-freezing electrolyte (0.4 m ZnSO 4 + 2.7 m Mg(ClO 4) 2) is developed, which features ultra-low freezing point (<−80 °C) and superior conductivity (7.50 mS cm−1 at −60 °C). Consequently, this organics-free hybrid electrolyte renders the as-built aqueous zinc ion hybrid capacitors (AZHCs) available to operate even at −60 °C with a high potential window of 2.4 V. Moreover, at −30 °C, such AZHC devices exhibit the highest specific capacity (123 mA h g−1), the maximum energy density (126 Wh kg−1 at 1050 W kg−1), an excellent rate performance (75.8 Wh kg−1 at 10495.4 W kg−1) and a stable working life over 32 000 cycles. This research points to a feasible strategy to improve the cryogenic performance of AZHCs with high energy density. • The addition of Mg(ClO 4) 2 can break the hydrogen bonding between water molecules. • The organics-free aqueous hybrid electrolyte possesses an ultra low freezing point. • The AZHCs exhibit excellent electrochemical performance at low temperatures. • The AZHCs possess a wider ESW at low temperatures. • Provide insights for other AZHCs to have superior low temperature performance. [ABSTRACT FROM AUTHOR]

• A polymeric ionic liquid is synsthesized and served as an electrolyte additive. • PVEIm.TFSI can improve the electrochemical stability of EMIm.TFSI/PC based electrolytes. • The operational voltage of EDLC with PIL additive increases from 2.8 V to 3.2 V. • Equivalent circle model and bode plots demonstrate changes in interface behaviors. • PIL additive reduces each element of impedance and improves the ions diffusion. Improving the energy density of electrochemical double layer capacitors (EDLC) is an important but challenging research topic. Electrolytes with wide operating potential windows are key materials for current EDLC technology. In this work, an ether branch polymeric imidazole ionic liquid (PVEIm.TFSI) is synsthesized and served as an electrolyte additive in common electrolyte to optimize the working potential ranges of carbon-based EDLC. The addition of PVEIm.TFSI can improve the electrochemical stability of electrolytes and effectively adjust the upper limit potential (P U), lower limit potential (P L). Under the optimal addition ratio of 10%, the operational voltage of EDLC increases from 2.8 V to 3.2 V, which lead to an approximately 41.5% energy density increase compared with EDLC without additive. Cycling stabibity of EDLC containing 10% PVEIm.TFSI is significantly enhanced under both 3.0 V and 3.2 V. Furthermore, an equivalent circuit model and Bode plots are proposed from the electrochemical impedance spectroscopy (EIS) measurements. Both simulated and measured date dedicate that PVEIm.TFSI reduces each element of resistance, which result in more ions movement and smaller energy barrier for the diffusion processes, thereby improving the electrochemical performance of cells. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of KNiF 3 @carbon nanotubes (CNTs) are synthesized via a facile solvothermal method and applied as supercapacitor electrodes. The addition of carbon nanotubes can significantly overcome the rate capability defect of bare KNiF 3 and improve the specific capacity to a certain extent, which mainly owing to the increase of conductivity and electron/ion transports capacity. In addition, the cross-linked structure of carbon nanotubes and the evenly anchoring of KNiF 3 nanoparticles can increase the stability of the composites. As a result, the optimal candidate KNiF 3 @CNTs-8 (the content of carbon nanotubes is 8 mg and the mass fraction is 1.0%) shows highest specific capacity (821.4 C g−1 at 1 A g−1) and capacity retention (83.6% at 16 A g−1). The asymmetric supercapacitor AC//KNiF 3 @CNTs-8 delivers extremely high energy density of 63.7 Wh kg−1. More importantly, the ASC device shows ultra-long cycling stability, with 95.9% capacity retention after 5000 cycles. These results prove that KNiF 3 @CNTs can be a promising material for supercapacitor. Image 1 • KNiF 3 @CNTs-8 presented high specific capacity and excellent rate capability. • The optimal composite material exhibited high electrical conductivity. • An asymmetric supercapacitor AC//KNiF 3 @CNTs-8 was fabricated and investigated. • The ASC device exhibited ultra-high energy density and excellent cycling life. [ABSTRACT FROM AUTHOR]