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Among the cathode materials for advanced Li-ion batteries, nickel-rich Ni-Co-Mn (NCM) LiNixCoyMnyO2 (x > 0.5, x + 2y = 1) attracts great interest as promising materials owing to their high capacity, low cost, good cycling stability, safety and the fact that their stable capacity can be extracted by charging up to 4.3 V vs. Li. In this work, the effect of the synthesis route—freeze-drying, self-combustion, solid state and co-precipitation on the performance of NCM622 (LiNixCoyMnyO2, x = 0.6, y = 0.2) cathodes—in Li cells was thoroughly studied. The material prepared by freeze-drying exhibited superior electrochemical properties. The effect of in situ and ex situ Zr4+ cations doping on the electrodes’ capacity, stability and average voltage was also studied. Doping via a top–down, ex situ mode improved the performance in terms of capacity stabilization, whereas electrodes comprising materials that were doped via a bottom–up in situ approach showed stable average voltage upon prolonged cycling. These effects are discussed and explained herein.

Although liquid mercury (Hg) has been known since antiquity, the formation of stable solid nano forms of Hg at room temperature has not been reported so far. Here, for the first time, we report a simple sonochemical route to obtain solid mercury nanoparticles, stabilized by reduced graphene oxide at ambient conditions. The as-formed solid Hg nanoparticles were found to exhibit remarkable rhombohedral morphology and crystallinity at room temperature. Extensive characterization using various physicochemical techniques revealed the unique properties of the solid nanoparticles of Hg compared to its bulk liquid metal phase. Furthermore, the solid nature of the Hg nanoparticles was studied electrochemically, revealing distinctive properties. We believe that solid Hg nanoparticles have the potential for important applications in the fields of electroanalytical chemistry and electrocatalysis., Formation of the stable solid mercury nanoparticles by acoustic cavitation and their electrochemical activity compared to its bulk liquid metal.

A key issue in the development of sustainable Na-ion batteries (NIBs) is the stability of the electrolyte solution and its ability to form effective passivation layers on both cathode and anode. In this regard, the use of fluorine-based additives is considered a promising direction for improving electrode performance. Fluoroethylene carbonate (FEC) and trans-difluoroethylene carbonate (DFEC) were demonstrated as additives or cosolvents that form effective passivating surface films in Li-ion batteries. Their effect is evaluated for the first time with cathodes in NIBs. By application of systematic electrochemical and postmortem investigations, the role of fluorinated additives in the good performance of Na0.44MnO2 (NMO) cathodes was deciphered. Despite the significant improvement in the performance of Li-ion cells enabled by the use of FEC and FEC + DFEC, the highest stability for NIBs was observed when only FEC was used as an additive. Mechanistic insights and analytical characterizations were carried out to shed light on the inferior effect of FEC + DFEC in NIBs, in contrast to its positive effect on the stability of Li-ion batteries.

Carbon Xerogel electrodes' materials were prepared by polycondensation of resorcinol and formaldehyde. They show accommodation of anions in preference to cations by their porous structure. In addition, their selectivity toward anion electroadsorption was found to be pH dependent, with an increase in electrodes' capacitance in acidic solutions. This dependence of the capacitance on the pH of the solution is explained by the presence of functional carboxylic surface groups in the Xerogel carbon micropores, determined by Boehm titration to be 3.26 meq/g. These functional surface groups give rise to the Donnan exclusion effect, whereby they cause partial repulsion of anions from the microporous structure. When the pH of the electrolyte solution is acidic ( The pH dependent capacitance of these carbons was utilized to examine the feasibility of energy extraction from mixing of saline and acidic solutions following the four basic steps of capacitive mixing processes – charge, solution exchange, discharge, and another solution exchange. As opposed to what we expected, a potential rise was observed when the solution was exchanged from acidic to saline, rather than during the other exchange, from saline to acidic solution. It appears that upon exchange of the solutions from saline to acidic, the expected potential rise resulting from the change in the electrodes capacitance, is cancelled by the new quinone-hydroquinone equilibrium that is established on the electrodes by their surface groups. The ability of these surface redox functional groups to store charge provides a basis for energy extraction from the neutralization of acidic solutions, as described herein.

Wastewater reclamation is becoming a top global interest as population growth and rapid industrialization pose a major challenge that requires development of sustainable cost-effective technologies and strategies for wastewater treatment. Carbon nanomembranes (CNMs)-synthetic 2D carbon sheets-can be tailored chemically with specific surface functions and/or physically with nanopores of well-defined size as a strategy for multifunctional membrane design. Here, we explore a bifunctional design for combined secondary wastewater effluent treatment with dual action of membrane separation and advanced oxidation processes (AOP), exploiting dissolved oxygen. The bifunctional membrane consists of a CNM layer on top of a commercial ultrafiltration membrane (Microlon (TM)) and a spray-coated reduced graphene oxide (rGO) thin film as the bottom layer. The CNM/support/rGO membrane was characterized by helium ion and atomic force microscopy, FTIR, XPS with a four-point conductivity probe, cyclic voltammetry, galvanostatic measurements, and impedance spectroscopy. Combined treatment of water by nanofiltration and AOP was demonstrated, employing a unique three electrode-dead end filtration setup that enables concurrent application of potential and pressure on the integrated membrane. For the model organic compound methylene blue, oxidation (by the Fenton reaction) was evaluated using UV-vis (610 nm). The rejection rate and permeability provided by the CNM layer were evaluated by dissolving polyethylene glycol (400 and 1000 Da) in the feed solution and applying pressure up to 1.5 bar. This demonstration of combined membrane separation and AOP using an integrated membrane opens up a new strategy for wastewater treatment.

Aqueous salt batteries with high concentrations of salt or water in salt aqueous systems have received considerable attention with focus on improving working voltage range and energy density. Here, the effect of NaClO4 salt concentration on the electrochemical performance and stability of tunnel-type Na0.44MnO2 (NMO) cathodes and organic polyimide (PI) derivative anodes was studied. High capacity retention and 100% coulombic efficiency were shown for NMO/PI full cell in saturated NaClO4 electrolyte. A high, stable capacity of 115 mAh/g was achieved for the PI anode material, and the full cell showed a stable capacity of 41 mAh/g at 2C rate for 430 cycles (calculated for the weight of NMO cathode). Even at a fast 5C rate, a discharge capacity of 33 mAh/g was maintained for 2,400 prolonged cycles with nearly 100% efficiency. The full cell device can achieve an average voltage of 1 V with energy density of 24 Wh/kg. This study highlights concentrated sodium perchlorate as a promising electrolyte solution for stabilization of electrodes and enhancement of electrochemical performance in aqueous media.

While many studies have been devoted to the development of new active materials for Na-ion aqueous batteries, much less attention has been given to the binders and other passive components, which largely determine the battery performance. This study demonstrates a beneficial use of MXene as a highly efficient binder for Na-ion anodes operating in aqueous electrolyte solutions. The high conductivity of 2D titanium carbide (Ti3C2Tx; T = terminal groups, mostly –OH, 0

Layered composite samples of lithium-rich manganese oxide (Li1.2Mn0.6Ni0.2O2) are prepared by a reverse microemulsion route employing a soft polymer template and studied as a positive electrode material. The product samples possess dual porosity with distribution of pores at 3.5 and 60 nm. Pore volume and surface area decrease on increasing the temperature of preparation. Nevertheless, the electrochemical activity of the composite increases with an increase in temperature. The discharge capacity value of the samples prepared at 800 and 900 °C is about 240 mA h g−1 at a specific current of 25 mA g−1 with a good cycling stability. The composite sample heated at 900 °C possesses a high rate capability with a discharge capacity of 100 mA h g−1 at a specific current of 500 mA g−1. The high rate capability is attributed to porous nature of the composite sample.

In the present study, a microwave-assisted, solution-based route has been employed to obtain porous CoO nano structures. Detailed characterization reveals that the flower-like nanostructures comprise petal-like sheets, each of which is made of an ordered, porous arrangement of crystallites of CoO measuring about 6 nm. TEM analysis shows that each ``petal'' is an oriented aggregate of CoO nanocrystals, such aggregation promoted by the hydroxyl moieties derived from the solution. The structure provides a large specific area as well as the porosity desirable in electrodes in Li-ion batteries. Electrochemical measurements carried out on electrodes made of nanostructured CoO show excellent Li ion-storing capability. A specific capacitance of 779 mAh g(-1) has been measured at a specific current of 100 mA g(-1). Measurements show also excellent cyclability and coulombic efficiency. Impedance spectroscopy provides evidence for charge transfer occurring in the porous networks. (C) 2015 Elsevier B.V. All rights reserved.

A porous layered composite of Li2MnO3 and LiMn1/3Ni1/3Fe1/3O2 (composition: Li1.2Mn0.53Ni0.13Fe0.13O2) is prepared by reverse microemulsion method employing tri-block co-polymer, F068 as a soft-polymer template. The Co-free composite is studied as a cathode material for Li-ion battery. Several samples are prepared by heating the precursor in the temperature range between 500 and 900 degrees C. The N-2 adsorption/desorption studies reveal that the product samples possess mesoporosity with broadly distributed pores around 15-50 nm diameter. Pore volume and surface area decrease by increasing the temperature of preparation. Charge-discharge, cycling and rate capability are investigated. The discharge capacity of the sample prepared at 900 degrees C is about 170 mAh g(-1) at a specific current of 25 mA g(-1) with a good cycling stability. A value of 140 mAh g(-1) is obtained at the end of 50 charge-discharge cycles. Discharge capacity of 91 mAh g(-1) is obtained at a specific current of 206 mA g(-1). A high rate capacity of the composite is attributed to its porous nature. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

Porous flower-like alpha-Fe2O3 nanostructures have been synthesized by ethylene glycol mediated iron alkoxide as an intermediate and studied as an anode material of Li-ion battery. The iron alkoxide precursor is heated at different temperatures from 300 to 700 degrees C. The alpha-Fe2O3 samples possess porosity and high surface area. There is a decrease in pore volume as well as surface area by increasing the preparation temperature. The reversible cycling properties of the alpha-Fe2O3 nanostructures have been evaluated by cyclic voltammetry, galvanostatic charge discharge cycling, and galvanostatic intermittent titration measurements at ambient temperature. The initial discharge capacity values of 1063, 1168,1183, 1152 and 968 mAh g(-1) at a specific current of 50 mA g(-1) are obtained for the samples prepared at 300, 400, 500, 600 and 700 degrees C, respectively. The samples prepared at 500 and 600 degrees C exhibit good cycling performance with high rate capability. The high rate capacity is attributed to porous nature of the materials. As the iron oxides are inexpensive and environmental friendly, the alpha-Fe2O3 has potential application as anode material for rechargeable Li batteries. (C) 2015 Elsevier Ltd. All rights reserved.

The partially exfoliated and reduced graphite oxide (PE-RGO) is prepared by low temperature thermal exfoliation of graphite oxide under air atmosphere. A symmetric carbon/carbon supercapacitor is studied in a Na2SO4 aqueous electrolyte. The discharge capacitance is 92 F g � 1 , when symmetric cell is cycled between the potential ranges from 0 to 1.6 V. This system demonstrates a stable charge/discharge cycle behavior up to 3000 cycles when the cell is operated at a voltage window of 1.6 V. The utilization ratio of potential window is 90% for this system is attributed to the more negative value of electrodes potential when the cell voltage is set to 0 V. The low-temperature exfoliation approach is convenient for mass production of graphenes at low cost and it can be used as electrode material for energy storage applications.

In the present work, Li2-x MnO3-y (LMO) thin films have been deposited by radio frequency (RF) reactive magnetron sputtering using acid-treated Li2MnO3 powder target. Systematic investigations have been carried out to study the effect of RF power on the physicochemical properties of LMO thin films deposited on platinized silicon substrates. X-ray diffraction, electron microscopy, surface chemical analysis and electrochemical studies were carried out for the LMO films after post deposition annealing treatment at 500 A degrees C for 1 h in air ambience. Galvanostatic charge discharge studies carried out using the LMO thin film electrodes, delivered a highest discharge capacity of 139 mu Ah mu m(-1) cm(-2) in the potential window 2.0-3.5 V vs. Li/Li+ at 100 W RF power and lowest discharge capacity of 80 mu Ah mu m(-1) cm(-2) at 75 W RF power. Thereafter, the physicochemical properties of LMO films deposited using optimized RF power 100 W on stainless steel substrates has been studied in the thickness range of 70 to 300 nm as a case study. From the galvanostatic charge discharge experiments, a stable discharge capacity of 68 mu Ah mu m(-1) cm(-2) was achieved in the potential window 2.0-4.2 V vs. Li/Li+ tested up to 30 cycles. As the thickness increased, the specific discharge capacity started reducing with higher magnitude of capacity fading.

a b s t r a c t A porous layered composite of Li2MnO3 and LiMn0.35Ni0.55Fe0.1O2 (composition:Li1.2Mn0.54Ni0.22Fe0.04O2) is prepared by inverse microemulsion method and studied as a positive electrode material. The precursor is heated at several temperatures between 500 and 900 ◦C. The X-ray diffraction, scanning electron microscopy, and transmission electron microscopy studies suggested that well crystalline submicronsized particles are obtained. The product samples possess mesoporosity with broadly distributed pores around 10∼50 nm diameter. Pore volume and surface area decrease by increasing the temperature of preparation. However, the electrochemical activity of the composite samples increases with an increase in temperature. The discharge capacity values of the samples prepared at 900 ◦ C are about 186 mAh g −1 at a specific current of 25 mA g −1 with an excellent cycling stability. The composite sample also possesses high rate capability. The high rate capability is attributed to the porous nature of the material.

Porous α-Fe2O3 nanostructures have been synthesized by a simple sol–gel route. The α-Fe2O3 nanostructures are poorly crystalline and porous with BET surface area of 386 m 2 g � 1 . The high discharge capacitance of α-Fe2O3 electrodes is 300 F g � 1 when the electrodes are cycled in 0.5 M Na2SO3 at a current density of 1 A g � 1 . The capacitance retention after 1000 cycles is about 73% of the initial capacitance at a current density of 2 A g � 1 . The high discharge capacitance of α-Fe2O3 in comparison with the literature reports are attributed to high surface area and porosity of the iron oxide prepared in the present study. As the iron oxides are inexpensive, the capacity of α-Fe2O3 is expected to be of potential use for supercapacitor application.

Carbon has been prepared by pyrolysis of grated, milk-extracted coconut kernel at 600 o C under nitrogen atmosphere. The disordered carbon has sheet like morphology. The carbon exhibits a high reversible Li + intercalation capacity in a non-aqueous electrolyte. The initial charge and discharge capacities are 990 and 400 mAh g -1 , thus resulting in an irreversible capacity loss of 590 mAh g -1 . Nevertheless, subsequent discharge capacity is stable over a large number of charge-discharge cycles. The electrodes withstand charge-discharge currents as high as 1257 mA g -1 and they deliver discharge capacity of 80 mAh g -1 . Diffusion coefficient of Li + obtained from galvanostatic intermittent titration is 6.7 x 10 -12 cm 2 s -1 . Thus the coconut kernel derived carbon is a suitable anode material for Li-ion batteries. Copyright © 2014 VBRI press.

Reduced graphene oxide (RGO) is prepared by thermal exfoliation of graphite oxide in air. Symmetric RGO/RGO supercapacitors are constructed in a non-aqueous electrolyte and characterized. The values of energy density are 44 Wh kg−1 and 15 Wh kg−1, respectively at 0.15 and 8.0 kW kg−1. The symmetric supercapacitor exhibits stable charge/discharge cycling tested up to 3000 cycles. The low-temperature thermal exfoliation approach is convenient for mass production of RGO at low cost and it can be used as electrode material for energy storage applications. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0031508eel] All rights reserved.

A porous layered composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) is prepared by reverse microemulsion method employing a soft polymer template and studied as a positive electrode material. The precursor is heated at several temperatures between 500 and 900 degrees C. The product samples possess mesoporosity with broadly distributed pores of about 30 nm diameters. There is a decrease in pore volume as well as in surface area by increasing the temperature of preparation. Nevertheless, the electrochemical activity of the composite increases with an increase in temperature. The discharge capacity values of the samples prepared at 800 and 900 degrees C are about 250 mAh g(-1) at a specific current of 40 mA g(-1) with an excellent cycling stability. A value of 225 mAh g(-1) is obtained at the end of 30 charge-discharge cycles. Both these composite samples possess high rate capability, but the 800 degrees C sample is marginally superior to the 900 degrees C sample. A discharge capacity of 100 mAh g(-1) is obtained at a specific current of 1000 mA g(-1). The high rate capability is attributed to porous nature of the composite samples. (C) 2013 The Electrochemical Society. All rights reserved.

Lithium-rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template and studied as a positive electrode material. The as-prepared sample possesses good crystalline structure with a broadly distributed mesoporosity but low surface area. As expected, cyclic voltammetry and charge–discharge data indicate poor electrochemical activity. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g−1 is obtained. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g−1. The rate capability study suggests that the sample provides about 150 mAh g−1 at a specific discharge current of 1.25 A g−1. Although the cycling stability is poor, the high rate capability is attributed to porous nature of the material.

Poorly crystalline porous δ-MnO 2 is synthesized by hydrothermal route from a neutral aqueous solution of KMnO 4 at 180 °C and the reaction time of 24 h. The as-synthesized sample and also the sample heated at 300 °C have nanopetals morphology with large surface area. On heating at temperatures ⩾400 °C, there is a decrease in BET surface area and also a change in morphology from nanopetals to clusters of nanorods. Furthermore, the poorly crystalline δ-MnO 2 converts into well crystalline α-MnO 2 phase. The electrochemical lithium intercalation and de-intercalation studies in a non-aqueous electrolyte provide a high discharge specific capacity (275 mAh g −1 ) at a specific current of 40 mA g −1 for the poorly crystalline δ-MnO 2 samples. The rate capability is also high. There is a decrease in capacity on repeated charge–discharge cycling. The specific capacity values of the crystalline α-MnO 2 samples are considerably less than the values of poorly crystalline δ-MnO 2 samples. Thus, the hydrothermal route facilitates preparation of poorly crystalline electrochemically active porous MnO 2 .

Porous flower-like alpha-Fe2O3 nanostructures synthesized by an ethylene glycol mediated self-assembly process are crystalline and porous with BET surface area of 64.6 m(2) g(-1). The discharge capacitance is 127 F g(-1) when the electrodes are cycled in 0.5 M Na2SO3 at a current density of 1 A g(-1). Capacitance retention after 1000 cycles is about 80% of the initial capacitance. The high discharge capacitance and its retention are attributed to high surface area and porosity of the iron oxide. As the iron oxides are inexpensive, the nano alpha-Fe2O3 is expected to be of potential use for supercapacitor application.

Amongst a number of different cathode materials, the layered nickel-rich LiNiyCoxMn1−y−xO2 and the integrated lithium-rich xLi2MnO3·(1 − x)Li[NiaCobMnc]O2 (a + b + c = 1) have received considerable attention over the last decade due to their high capacities of ~195 and ~250 mAh·g−1, respectively. Both materials are believed to play a vital role in the development of future electric vehicles, which makes them highly attractive for researchers from academia and industry alike. The review at hand deals with both cathode materials and highlights recent achievements to enhance capacity stability, voltage stability, and rate capability, etc. The focus of this paper is on novel strategies and established methods such as coatings and dopings.

TIN thin films with (200) fibre texture are deposited on Cu substrate at room temperature using reactive magnetron sputtering. They exhibit a discharge capacity of 172 mu Ah cm(-2) mu m(-1) (300 mAh g(-1)) in a non-aqueous electrolyte containing a Li salt. There is a graded decrease in discharge capacity when cycled between 0.01 and 3.0 V. Electron microscopy investigations indicate significant changes in surface morphology of the cycled TiN electrodes in comparison with the as deposited TiN films. From XPS depth profile analysis, it is inferred that Li intercalated TIN films consist of lithium compounds, hydroxyl groups, titanium sub oxides and TiN. Lithium diffusivity and reactivity decrease with increase in depth and the major reaction with lithium takes place at film surface and grain boundaries. (C) 2014 Elsevier Ltd. All rights reserved.