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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.

Li and Mn-rich Li1+xNiyCozMnwO2 (LMR-NMC, 0 0.5) materials remain commercially relevant owing to their high specific capacity. Due to this stoichiometry, their synthesis forms always at least two phases: monoclinic Li2MnO3 and rhombohedral LiNiaCobMncO2 (a = b = c = 1) layered moieties. However, a complete understanding of their complex crystal structure has not yet been fully realized. The monoclinic phase may become electrochemically active only at high potentials (>4.6 V vs. Li). To complicate matters even more, it has been shown that the electrochemical performance of these materials, having formally the same stoichiometry, can vary with the chosen method of material synthesis. Identification of the chemical and/or structural reasons for these variations in performance is crucial to ensure the promotion of these important cathode materials towards a practical use. Yet most methods of analysis cannot distinguish the subtle, localized variations that account for such differences. Here, solid state 6,7Li NMR was found to be successful in identifying several distinctions between compounds with identical chemical formulae. Many distinctions can be made, and even suggested to account for some of the differences in the electrochemical behaviors noted for the differently prepared materials.

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.

Solid-state batteries have received renewed attention in recent years. The present study compares all-solid-state sodium batteries containing sodium metal anodes, NaTi2(PO4)3 (NTP) cathodes and PEO polymer electrolyte (PE) with two salts—NaPF6 and NaClO4. Electrochemical properties were determined by means of both AC and DC measurements. For fresh symmetric cells, it seems like using NaClO4 as the salt leads to a lower interfacial resistance, but during contact with Na anodes, PEO:NaClO4 PE produces an unstable interface whereas PEO-NaPF6 forms a stable interface upon contact with sodium anodes. Battery prototypes with PEO:NaClO4 showed a better performance than those using PEO:NaPF6 in terms of specific capacity and energy content, as NaPF6 produces HF by-product which impairs the performance of full cells. However, the use of composite solid electrolyte containing PEO:NaPF6 and TiO2 nanotubes alleviates detrimental effects of HF and thus enables a better performance of SS Na battery prototypes. This is probably due to the titania particles acting as a scavenger of HF, an inevitable contaminant in electrolyte systems containing PF6 − anions. On adding TiO2 to polymer electrolytes, of both salts, the performance improves, what means that the TiO2 has several positive effects in these systems.

The use of sodium manganese oxide as an intercalation electrode for water treatment was recently explored, and referred to as a “desalination battery” and “hybrid capacitive deionization”. Here, we examine the feasibility of using such a desalination battery, comprising crystalline Na4Mn9O18 as the cathode and Ag/AgCl/Cl− electrode as the anode, to extract energy from low-grade waste heat sources. Sodium manganese oxide electrode's material was produced via a solid-state synthesis. Electrodes were produced by spray-coated onto graphite foils, and showed a temperature dependence of the electrode potential, namely, ∂ E / ∂ T , of −0.63 mV/K (whereas, the Ag/AgCl/Cl− mesh electrode showed much lower temperature dependence

Layered cathode materials of the type Na1+xLi0.05Mn0.54Co0.13NiyO2−z (0 200 mA h g−1. Analysis by X-ray and electron diffraction reveals that the new materials are initially mixtures of rhombohedral and monoclinic phases. Attempts to prepare layered compounds with similar compositions by chemical means resulted in phases of hexagonal structure with rather poor electrochemical activity, emphasizing the importance of the synthesis by electrochemical ion exchange. Also, the stability of electrochemically prepared Na insertion cathode materials in cycling experiments was insufficient for practical consideration. In turn, cathodes prepared from the same Li precursors coated by a thin layer of alumina via atomic layer deposition, followed by electrochemical Na/Li ion exchange, demonstrated stable capacity (>170 mA h g−1) during prolonged cycling. Their average discharge voltage was 300 mV higher compared to the counterpart uncoated Na intercalation cathodes. The structure and behavior of these electrodes were thoroughly explored by a variety of analytical and surface tools, in conjunction with electrochemical techniques.

Electrodeposited ZnO coatings suffer severe capacity fading when used as conversion anodes in sealed Li cells. Capacity fading is attributed to (i) the large charge transfer resistance, $$R_{\mathrm{ct}}$$ (300–700 $$\Omega $$ ) and (ii) the low $$\hbox {Li}^{+}$$ ion diffusion coefficient, $$D_{\mathrm{Li}}^{+}\ (10^{-15}$$ to $$10^{-13}\hbox { cm}^{2}\hbox { s}^{-1})$$ . The measured value of $$R_{\mathrm{ct}}$$ is nearly 10 times higher and $$D_{\mathrm{Li}}^{+}$$ 10–100 times lower than the corresponding values for $$\hbox {Cu}_{2}\hbox {O}$$ , which delivers a stable reversible capacity.

Li- and Mn-rich layered oxide cathodes are known to suffer from capacity fading and average discharge voltage decay upon cycling. In the present study, the improved cycling stability of a Li- and Mn-rich cathode Li1.2Ni0.27Mn0.40Co0.13O2 in full cells is reported. The electrochemical performance of the Li- and Mn-rich cathodes comprising Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2 was tested in Li-ion full cells with graphite as anode material at 30 °C. The full cells with Li1.2Ni0.13Mn0.54Co0.13O2 cathodes exhibited initially high capacities of about 250 mAh g1, which fades rapidly to 130 mAh g–1 after 120 cycles at C/5 rate. However, full cells comprising Li1.2Ni0.27Mn0.40Co0.13O2 cathodes exhibited an initial capacity of about 190 mAh g–1 with very stable cycle-life, i.e., about 185 mAh g–1 after 150 cycles at C/5 rate. Also, these cathodes possess higher rate capability as compared to full cells comprising Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. Thus, the electrochemical performance of Li1.2Ni...

Na0.6[Li0.2Ni0.2Mn0.6]O2 is synthesized by a self-combustion reaction (SCR) and studied for the first time as a cathode material for Na-ion batteries. The Na0.6[Li0.2Ni0.2Mn0.6]O2 cathode presents remarkable high rate capability and prolonged stability under galvanostatic cycling. A detailed analysis of X-ray diffraction (XRD) patterns at various states of cycling reveals that the excellent structural stability is due to a primarily solid-solution sodiation/desodiation mechanism of the material during cycling. Moreover, a meaningful comparison with Na0.6MnO2 and Na0.6[Li0.2Mn0.8]O2 reveals that the Na0.6[Li0.2Ni0.2Mn0.6]O2 cathode achieves a very high working-average voltage that outperforms most of the lithium-doped manganese-oxide cathodes published to date. Fil: de la Llave, Ezequiel Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Bar-Ilan University; Israel Fil: Nayak, Prasant Kumar. Bar-Ilan University; Israel Fil: Levi, Elena. Bar-Ilan University; Israel Fil: Tirupathi Rao, Penki. Bar-Ilan University; Israel Fil: Bublil, Shaul. Bar-Ilan University; Israel Fil: Hartmann, Pascal. Basf; Alemania Fil: Chesneau, Frederick Francois. Basf; Alemania Fil: Greenstein, Miri. Bar-Ilan University; Israel Fil: Nazar, Linda F.. University of Waterloo; Canadá Fil: Aurbach, Doron. Bar-Ilan University; Israel

Pulsed laser deposited TiNb 2 O 7 thin films are demonstrated as anode materials in rechargeable Li-ion micro-batteries. The monoclinic and chemically pure TiNb 2 O 7 films in different morphologies were successfully deposited at 750 °C. The single phase formation was confirmed by grazing incident X-ray diffraction, micro-Raman spectroscopy, high resolution transmission electron microscopy, field emission scanning electron microscopy and X-ray photoelectron spectroscopy. The oxygen partial pressure during the deposition significantly influenced the properties of TiNb 2 O 7 films. The TiNb 2 O 7 thin films exhibited excellent stability with fast kinetics reversible reaction. The TiNb 2 O 7 films showed initial discharge specific capacity of 176, 143 μAh μm −1 cm −2 at 30, 50 μA cm −2 current densities respectively with 92% coulombic efficiency in a non-aqueous electrolyte consisting of Li + ions. The high discharge specific capacity of TiNb 2 O 7 thin films may be attributed to nanometer grain size with high roughness which offers high surface area for Li-diffusion during charge and discharge process.

A porous, hollow, microspherical composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) was prepared using hollow MnO2 as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g(-1) at a specific current of 25 mA g(-1) with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g(-1) was obtained for this composite at a specific current of 1000 mA g(-1). The high rate capability of this hollow microspherical composite can be attributed to its porous nature.

Co2(OH)3Cl xerogel interconnected mesoporous structures have been prepared by a facile one pot sol-gel process and heat treated at 200 and 400 °C. All samples are studied for their morphology, structure, and electrochemical stability upon cycling. The specific capacitance of the as-prepared Co2(OH)3Cl from single electrode study is 450 F/g, when the electrodes are cycled in 3 M KOH at a specific current 2 A/g. Interestingly, capacity retention after 500 and 1000 cycles is about 92 and 75 %, respectively. Sample heated at 200 °C exhibits 308 F/g at 2 A/g and that heated at 400 °C shows only 32 F/g at 0.2 A/g. With an increase in preparation temperature, amorphous Co2(OH)3Cl is converted to crystalline Co3O4 phases with lower electrochemical performance. In full cell study, as-prepared Co2(OH)3Cl showed a capacity of about 49 F/g as asymmetric capacitor and 32 F/g as symmetric capacitor at 2 A/g current density. Co2(OH)3Cl being a novel porous material with merits of homogeneous porosity, high surface area, and an interconnected three dimensional (3D) structure exhibits considerably high capacitance. With a significant specific capacity and electrochemical stability, the synthesized material is a novel potential candidate for supercapacitors.

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.

Electrodeposited Cu2O coatings with 111 out-of-plane orientation were found to have the lowest reversible discharge capacity as anodes for Li-ion cells. This is attributed to the low surface energy and the consequent high thermodynamic stability of the 111 crystal face of Cu2O. In contrast, the 200 oriented coating has a higher reversible discharge capacity, owing to its polar nature and high surface energy. The highest reversible discharge capacity was observed for unoriented coatings, emphasizing the critical role played by grain boundaries in the conversion electrodes. The morphology of crystallites in the electrodes recovered after cycling is different in the three cases, suggesting that the nature of reversible chemical conversion is guided by physical attributes of the precursor Cu2O crystallites.

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.

Carbonization of milk-free coconut kernel pulp is carried out at low temperatures. The carbon samples are activated using KOH, and electrical double-layer capacitor (EDLC) properties are studied. Among the several samples prepared, activated carbon prepared at 600 °C has a large surface area (1,200 m2 g−1). There is a decrease in surface area with increasing temperature of preparation. Cyclic voltammetry and galvanostatic charge–discharge studies suggest that activated carbons derived from coconut kernel pulp are appropriate materials for EDLC studies in acidic, alkaline, and non-aqueous electrolytes. Specific capacitance of 173 F g−1 is obtained in 1 M H2SO4 electrolyte for the activated carbon prepared at 600 °C. The supercapacitor properties of activated carbon sample prepared at 600 °C are superior to the samples prepared at higher temperatures.

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.

LiCoO2 thin films used as cathode layers in thin-film solid-state batteries have been deposited from LiCoO2 powder target using radio frequency (rf) magnetron sputtering in a cost effective approach in terms of material consumption and processing time. Xray diffraction (XRD) studies of the films after post deposition annealing treatment revealed (104) orientation, which is the characteristic of rf sputtered LiCoO2 films. Raman spectroscopy was used to identify the different modes of vibration of atoms in the film. The surface morphology and cross-section of the samples were characterized using field emission scanning electron microscopy (SEM). The chemical analysis of LiCoO2 thin films was examined by X-ray photoelectron spectroscopy (XPS) showed atomic ratio of Li/Co as 0.9 which is close to the ideal value 1. Electrochemical characterization such as charge – discharge and cyclic voltammetry were conducted for LiCoO2 films deposited on platinized silicon substrates in the potential range 3.0 to 4.2 V vs Li/Li + . The maximum discharge capacity of 64 µAh.µm -1 . cm -2 and 52 µAh. µm -1 .cm -2 were achieved when discharged at a current of 5 µA and 50 µA for the first discharge cycle respectively. Moreover the electrochemical investigations of LiCoO2 thin films on flexible copper substrates also investigated and achieved an initial discharge capacity of 83 mAh/g. The possible reasons for degradation in the electrochemical properties have been discussed. The present work indicates suitability of sputtering from powder targets for thin film battery fabrication. Copyright © 2013 VBRI press.

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 .

Li-ion batteries (LIBs) today face the challenge of application in electrified vehicles (xEVs) which require increased energy density, improved abuse tolerance, prolonged life, and low cost. LIB technology can significantly advance through more realistic approaches such as: i) stable high-specific-energy cathodes based on Li1+ x Niy Coz Mnw O2 (NCM) compounds with either Ni-rich (x = 0, y → 1), or Li- and Mn-rich (0.1 0.5) compositions, and ii) chemically active separators and binders that mitigate battery performance degradation. While the stability of such cathode materials during cell operation tends to decrease with increasing specific capacity, active material doping and coatings, together with carefully designed cell-formation protocols, can enable both high specific capacities and good long-term stability. It has also been shown that major LIB capacity fading mechanisms can be reduced by multifunctional separators and binders that trap transition metal ions and/or scavenge acid species. Here, recent progress on improving Ni-rich and Mn-rich NCM cathode materials is reviewed, as well as in the search for inexpensive, multifunctional, chemically active separators. A realistic overview regarding some of the most promising approaches to improving the performance of rechargeable batteries for xEV applications is also presented.

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.

Lithium manganese oxide (Li2-xMnO3-y) thin films have been deposited from activated Li2MnO3 powder by radio frequency magnetron sputtering for the first time in the literature and subjected to electrochemical characterization. Physicochemical characterization by X-ray diffraction has revealed the formation of the thin films with crystallographic phase identical to that of the powder target made of Li2-xMnO3-y. The Li:Mn atomic ratio for the powder and film are calculated by X-ray photoelectron spectroscopy and it is found to be 1.6:1.0. From galvanostatic charge discharge studies, a specific discharge capacity of 139 mu Ah mu m(-1) cm(-2) was obtained when cycled between 2.00 and 3.50 V vs Li/Li+. Additionally the rate capability of the thin film electrodes was studied by subjecting the cells to charge-discharge cycling at different current densities in the range from 10 mu A cm(-2) to 100 mu A cm(-2). (C) 2013 The Electrochemical Society. All rights reserved.

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.

Since commercializing of the first lithium-ion battery by Sony Corporation in 1991, graphitic carbons have been used as anode materials. Graphitic carbons owe to their favorable characteristics such as eco-friendly, stability upon cycling, low operating potential versus Li/Li+, etc. however, carbon materials also poses several challenges that include limited specific capacity (~ 372 mAh g-1), formation of a solid-electrolyte interphase (SEI), lithium plating or formation of a surface film at high current rates, etc. To overcome these difficulties, research has been focused on transition metal oxides as alternate anode materials. Various metal oxides (to mention a few Co3O4, MnO2, Fe3O4 and Fe2O3) have been reported to undergo conversion reactions while exhibiting lower voltages with high reversible capacities than the traditional graphitic carbon counterparts. This has motivated many researchers to study the conversion reaction of oxide materials.1 Among the transition metal oxides studied, hematite α-Fe2O3 has been intensively studied due to its low cost, excellent stability, environmental friendly properties and also providing high theoretical capacity 1007 mAh g-1 based on 6 Li+per formula unit. One of the challenging issues in conversion reaction of a bulk electrode material is to maintain structural integrity during electrochemical cycling with associated issues such as volume changes, pulverization, etc., which affect the performance.2Congruently, through nanostructured materials such as nanoparticles, nanocubes, nanorods, nanotubes and nanoflowers, we may facilitate an increase in the electrochemical performance due to short diffusion length for Li-ion and electronic transport. Among these, porous materials have been studied widely because of the easy percolation of electrolyte into core of particles which result in high rate capability. Porous materials can also sustain mechanical stress generated by volume expansion/contraction during the electrochemical cycling. In the present work, we report synthesis of iron alkoxide precursors using 4.4 mmol FeCl3.6H20, 90 mmol urea and 124 mmol tetra butyl ammonium bromide are added to 180 ml of ethylene glycol in 250 ml round bottomed flask, stirred for 10 min to get homogeneous solution and refluxed at 195 oC for 30 min. The obtained green precipitate of iron alkoxide is washed with ethanol and dried at 60 oC for 12 h. The resultant dried powder is calcined at a range of temperatures from 300 to 500 oC for 3 h in air.3 A porous flower-like nanostructured α-Fe2O3 is obtained by subsequent calcination of iron alkoxide precursor. The phase purity and morphology of the final product (α-Fe2O3) are studied by XRD, SEM and TEM analysis. The microscopic images show (Fig. 1) a flower-like morphology. The BET surface area and its pore size of the α-Fe2O3 are measured and they are 64 m2 g-1 and 6 nm, respectively. The α-Fe2O3 powder is subjected to galvanostatic charge/discharge experiments between 0.01 and 3.0 V versus Li/Li+. The charge-discharge profile is shown in Fig. 2. The discharge capacities obtained for 1st, 10th and 20th cycle are of 1058, 1044 and 917 mAh g-1 respectively for the sample prepared at 300 oC. These values are greater than the values reported so far on α-Fe2O3. Porous nature of α-Fe2O3 prepared in the present study is responsible for high discharge capacity and also high rate capability. Results of these studies including both physical and electrochemical investigations will be presented. Acknowledgements: SS and TRP acknowledge University Grants Commission (UGC), Government of India for Dr. D. S. Kothari fellowship and Senior Research Fellowship, respectively. References: 1. M. V. Reddy et al, Adv. Funct. Mater., 2007 17,2792. 2. P. G. Bruce et al, Angew. Chem. Int. Ed., 2008, 47, 2930. 3. S. Shivakumara et al, Electrochem. Lett., 2013, 2, A60.