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This work is part of ongoing and systematic investigations by our groups on the synthesis, electrochemical behavior, structural investigations, and computational modeling of the Ni-rich materials Li[NixCoyMnz]O2 (x+y+z=1; x≥0.8) for advanced lithium-ion batteries. This study focuses on the LiNi0.85Co0.10Mn0.05O2 (NCM85) material and its improvement upon doping with B3+ cations. The data demonstrate the substantial improvement of the doped electrodes in terms of cycling performance, lower voltage hysteresis and reduced self-discharge upon high temperature storage. The electronic structure of the undoped and B-doped material was modelled using density functional theory (DFT), which identified interstitial positions as the preferential location of the dopant. DFT models were also used to shed light on the influence of boron on surface segregation, surface stability, and oxygen binding energy in NCM85 material. Experimental evidence supports the suggestion that the boron segregates at the surface, effectively reducing the surface energy and increasing the oxygen binding energy, and possibly, as a result, inhibiting oxygen release. Additionally, the presence of borate species near the surface can reduce the nucleophilicity of surface oxygens. Cycling of the Li-cells did not cause noticeable changes in the microstructure of the B-doped materials, whereas significant microstructural changes, like a propagating network of cracks, was observed across all grains in the cycled undoped NCM85 cathodes. Analysis by high-resolution microscopy and 6Li and 11B solid-state nuclear magnetic resonance (ss NMR) allowed for the correlation of capacity fade and degradation of the different NCM85 materials with their structural characteristics.

Co-location patterns in spatial dataset are the interesting collection of dissimilar objects which are located in proximity. We keep similar objects in an entity set and maintain that no two objects in a co-location pattern belong to an entity set. Location proximity is based on Euclidean distance measure. However, algorithms for mining patterns in transactional datasets are not directly applicable to spatial datasets for mining co-location patterns. Conventional methods are not applicable to distributed temporal data and many applications generating spatial dataset are inherently distributive in nature. In this paper, a Map-Reduce based approach is proposed to find all co-location patterns from a spatial dataset distributed over nodes. This approach is modularized one and consists of four algorithms. With the first three algorithms in the first approach and by proposing an algorithm for dynamic datasets, this paper contains another approach for the co-location patterns set, that also updates in an incremental manner (not from scratch) whenever certain changes occur in the dataset. Experimental results on larger datasets are also presented.

Ni-rich layered oxide LiNi1 - x - yCoxMnyO2 (1 - x - y > 0.5) materials are favorable cathode materials in advanced Li-ion batteries for electromobility applications because of their high initial discharge capacity. However, they suffer from poor cycling stability because of the formation of cracks in their particles during operation. Here, we present improved structural stability, electrochemical performance, and thermal durability of LiNi0.85Co0.1Mn0.05O2(NCM85). The Nb-doped cathode material, Li(Ni0.85Co0.1Mn0.05)0.997Nb0.003O2, has enhanced cycling stability at different temperatures, outstanding capacity retention, improved performance at high discharge rates, and a better thermal stability compared to the undoped cathode material. The high electrochemical performance of the doped material is directly related to the structural stability of the cathode particles. We further propose that Nb-doping in NCM85 improves material stability because of partial reduction of the amount of Jahn-Teller active Ni3+ ions and formation of strong bonds between the dopant and the oxygen ions, based on density functional theory calculations. Structural studies of the cycled cathodes reveal that doping with niobium suppresses the formation of cracks during cycling, which are abundant in the undoped cycled material particles. The Nb-doped NCM85 cathode material also displayed superior thermal characteristics. The coherence between the improved electrochemical, structural, and thermal properties of the doped material is discussed and emphasized.

Here, three types of surface coatings based on adsorption of organic aromatic acids or their Li salts are applied as functional coating substrates to engineer the surface properties of high voltage LiNi

We demonstrate a novel surface modification of Li- and Mn-rich cathode materials 0.33Li2MnO3·0.67LiNi0.4Co0.2Mn0.4O2 for lithium-ion batteries (high-energy Ni-Co-Mn oxides, HE-NCM) via their heat treatment with trimesic acid (TA) or terephthalic acid at 600 °C under argon. We established the optimal regimes of the treatment-the amounts of HE-NCM, acid, temperature, and time-resulting in a significant improvement of the electrochemical behavior of cathodes in Li cells. It was shown that upon treatment, some lithium is leached out from the surface, leading to the formation of a surface layer comprising rock-salt-like phase Li0.4Ni1.6O2. The analysis of the structural and surface studies by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy confirmed the formation of the above surface layer. We discuss the possible reactions of HE-NCM with the acids and the mechanism of the formation of the new phases, Li0.4Ni1.6O2 and spinel. The electrochemical characterizations were performed by testing the materials versus Li anodes at 30 °C. Importantly, the electrochemical results disclose significantly improved cycling stability (much lower capacity fading) and high-rate performance for the treated materials compared to the untreated ones. We established a lower evolution of the voltage hysteresis with cycling for the treated cathodes compared to that for the untreated ones. Thermal studies by differential scanning calorimetry also demonstrated lower (by ∼32%) total heat released in the reactions of the materials treated with fluoroethylene carbonate (FEC)-dimethyl carbonate (DEC)/LiPF6 electrolyte solutions, thus implying their significant surface stabilization because of the surface treatment. It was established by a postmortem analysis after 400 cycles that a lower amount of transition-metal cations dissolved (especially Ni) and a reduced number of surface cracks were formed for the 2 wt % TA-treated HE-NCMs compared to the untreated ones. We consider the proposed method of surface modification as a simple, cheap, and scalable approach to achieve a steady and superior electrochemical performance of HE-NCM cathodes.

We present in this paper a modification and stabilization approach for the surface of a high specific capacity Ni-rich cathode material LiNi0.85Co0.10Mn0.05O2 (NCM85) via SO2 gas treatment at 250–4...

High-Ni-rich layered oxides [e.g., LiNi

Behaviour of objects are determined from collections of responses, reactions, movements, properties, which are noted as attributes along with time and location in some spatial dataset. Behavioural Pattern finds a set of objects having similar behaviour. We have explored all types of possible measures to define similarity among objects having some similar features. Objects from same entity will have same set of features, whereas objects from different entity may have some similar features. A similarity measure has been proposed for mining behavioural patterns in different entity set. An approach for computing behavioural patterns is also proposed in this paper. Recent applications are focusing to understand the interaction between objects from various entity set, needs to measure behavioural similarity among objects within a region of interest. This newly defined measure and mining approach will defiantly help many applications to analyse data and extract important knowledge. Keywords: Similarity measure, Behavioural similarity, Behavioural patterns, Multiple datatype, Spatial data

We demonstrate a novel surface modification of Li- and Mn-rich cathode materials 0.33Li

Ternary transition metal oxides offer several advantageous features compared to the binary analogs due to presence of hetero transition metals with multiple valence states and the possible synergistic effects. Recently, metal organic frameworks have emerged as exotic template for synthesis of morphologically pre-designed metal oxide nanostructures. Nonetheless, synthesis of heteroatom ternary metal oxides through bi-metal organic framework (BMOF) route has proved to be challenging. Herein, we report a scalable single-step synthesis protocol for obtaining Ni/Mn-1,3,5-benzenetricarboxylate BMOF from which interconnected multi-faceted particles of NiMn2O4 spinel could be derived by thermal calcination at 800 °C. When applied as an anode for lithium-ion battery, the BMOF-derived mesoporous NiMn2O4 delivered a high reversible capacity (1049 mAh g−1), good rate performance (413 and 258 mAh g−1 at 503 and 1257 mA g−1) and good electrochemical stability highlighting the MOF-derived morphological advantages. The present results would help designing ternary metal oxide nanostructures for electrochemical energy storage application.

Aqueous rechargeable batteries (ARB) offer reasonably higher energy density and cycle life than their non-aqueous counterparts. Yet, the bottleneck is a limited choice of positive electrodes coupled with low-rate capability and inadequate cycle life. We report here a wet chemical approach to synthesize in-situ three-dimensional (3D) ‘cotton-ball’ shaped porous iron-nickel sulfide (FeNi2S4) (henceforth referred to as PINS) as a diffusion-controlled ARB electrode. It shows a high specific capacity of 177 mA h g−1 at 1 A g−1 vs Pt in the alkaline electrolyte with excellent rate capability (89 mA h g −1 at 40 A g−1) and ultra-long cycle life (10,000 cycles). Furthermore, a pouch-type full-cell ARB (FeNi2S4//AC) delivers an energy density of 56.7 Wh kg−1 at a power density of 871.5 W kg−1 with high cycling stability (10,000 cycles). The present study offers a straightforward and efficient approach for developing nanostructured transition metal sulfide-based cathode materials for practical ARB.

Hybrid organic–inorganic materials, particularly with a framework structure, have recently attracted much attention as redox electrode. In this work, we report for the first time, the electrochemical properties of redox-active organic molecular Li-salt derived from 1,2,4-benzenetricarboxylic acid (1,2,4-H 3 BTC) as lithium-ion battery (LIB) anode. The organic molecular salt (1,2,4-Li-BTC), prepared by a simple low temperature (80 °C) solvothermal process, delivers a first cycle charge capacity of 162 mAhg −1 . Further, it is shown that preparing a composite electrode with 8 wt% MWCNT improves charge transport and alleviates the dissolution problem, resulting in steady cycling behaviour and good rate performance. The results show promise for this new class of anode with flat charge discharge profiles and a convenient working potential of ∼1.2 V vs. Li + /Li.

Metal oxide conversion electrodes suffer from low power density and cycling stability desired for high rate lithium-ion battery (LIB). Herein, we present a method of integrating nanoscale discrete Mn3O4 particles (20 nm) into a two-dimensional sheet-like N-incorporated mesoporous carbon by a simple synthetic protocol using NaCl crystallites as an exo-template. The encapsulated structure of Mn3O4@C greatly supresses the mechanical stress induced by repeated volumetric expansion/contraction and at the same time, N-incorporation in the carbon matrix facilitates charge transport. When tested as a 2.0 V LIB anode, Mn3O4@C showed an excellent rate performance (406 mAh g-1 at 2.5 A g-1 and 188 mAh g-1 at 12.5 A g-1) and outstanding cycling stability (capacity retention of 90% after 10000 cycles at 2.5 A g-1). Such remarkable performance could be linked to fast charge transportation through the 2D carbon sheets and also, to the encapsulated structure avoiding direct contact with the electrolyte precluding growth of SEI layer upon cycling. Furthermore, a LiFePO4//Mn3O4@C full cell delivers specific capacities of 136 mAh g-1 and 92 mAh g-1 (with respect to the mass of cathode) at current densities of 0.25 and 0.5 mA g-1. The cell shows excellent cycling stability with 76% retention of capacity after 350 cycles demonstrating the practical viability.

Porous carbon nanofibers (CNF) with high surface area were synthesized by electrospinning a mixture of polymerized sucrose and poly(vinyl alcohol) (PVA) in water. This green method provides an excellent environment friendly alternative to the toxic polymers and solvents commonly used for synthesis of CNF/metal nanoparticle composites. Stabilization at 350 degrees C and subsequent carbonization of the electrospun polymer at 950 degrees C in reducing environment formed semigraphitic CNF. In situ doping of Ag nanoparticles in CNF resulted in a ten-fold increase in electrical conductivity of CNF for as low as 0.1 wt% Ag doping. When tested as electrode in aqueous electrochemical supercapacitor, the positive effect of Ag-doping is revealed by two-fold improvement in capacitance over the pristine CNF at a high current density of 5.0 A g(-1). Interestingly, a continuous increase in capacitance by -65% was observed during 5000 continuous cycling which is attributed to increase in active charge storage sites due to gradual opening up of the pores and increasing diffusion of electrolyte ions triggered by enhanced wettability of the electrodes.

We report here a controllable large-scale synthesis protocol for TiO2-rGO nanocomposites with a hollow spherical morphology by a novel aerosol-assisted spray drying method followed by calcination. The developed strategy is easy to scale-up without significant change in morphology. The precursors used for the synthesis are aqueous titanium ammonium peroxo-carbonate complex (TAPCC) solution, being decomposable at low temperatures, and an aqueous graphene oxide (GO) suspension; no additive or structure-directing agent is required. Both the precursors play vital roles in hollow sphere formation. The enhanced internal pressure inside the atomized droplets built-up in situ through decomposition of TAPCC forming gaseous CO2, NH3, O2 and H2O vapour, helps overcome the crumpling effect of GO. The sheet structure of GO provides sufficient mechanical strength to prevent bursting of the expanded droplets. The synthesized TiO2-rGO hollow spheres are porous, composed of 10–20 nm TiO2 particles dispersed on the surfaces of rGO with a surface area of 86 m2 g−1. The synthesized TiO2-rGO composites showed superior electrochemical performance as lithium-ion battery (LIB) anode with capacity values of 265 mA h g−1 (10 wt% rGO) and 274 mA h g−1 (20 wt% rGO) at 18.8 mA g−1 as compared to 236 mA h g−1 for the pristine sample with a 2D flake-like morphology. This is due to the unique thin-walled hollow-spherical structure of TiO2-rGO composites, which provides a large number of electrochemically accessible active sites, favorable diffusion paths for Li+ ions and enhanced charge transport. Thus, the present synthetic method has great potential for large scale production of TiO2-rGO hollow spheres for application as anode in practical high-rate lithium-ion batteries.

Synthesis of nanostructures with pre-designed morphology has recently gained tremendous research attention for achieving enhanced performance. Herein, we report synthesis of hetero-dimensional hybrid nanostructure of Fe 2 (MoO 4 ) 3 consisting of nanorods (length 90–170 nm, dia ∼30 nm) in which spherical nanoparticles (dia 5–10 nm) are embedded. We also report the electrochemical properties of synergic Fe 2 (MoO 4 ) 3 /MWCNT composites as lithium-ion battery anode for the first time. Here, 1D Fe 2 (MoO 4 ) 3 nanorods serve as a strain accommodative matrix imparting stability while the entrenched 0D Fe 2 (MoO 4 ) 3 nanoparticles offer a large number of active sites yielding high capacity. Due to high surface to volume ratio of the composites, the Li + ion diffusion length is shortened leading to a faster kinetics and improved the rate performance. Moreover, MWCNT provides an effective conduction network for electron transport during lithiation/delithiation process and at the same time, serves as a strain-buffer preserving mechanical integrity of the composite electrode. This three-way strategy results in a specific capacity of 1321 mAh g −1 for a 50:50 wt% composite of Fe 2 (MoO 4 ) 3 and MWCNT. Even at a high current density of 1.0 mA cm −2 (1200 mA g −1 ), capacity of 600 mAh g −1 could be obtained. Further, 82% retention of capacity is observed after 200 cycles at 0.1 mA cm −2 . Importantly, no appreciable change in morphology is observed with discharge-charge cycling.

Synthesis of nanocomposites of metal oxide and reduced graphene oxide (rGO) in a hollow spherical form has been proved to be challenging due to the crumbling effect of rGO. In this paper, we report a simple, cost-effective and large-scale synthetic strategy for producing porous NiCo2O4 hollow spheres as well as rGO–NiCo2O4 hollow spheres through spray drying of respective metal ammonium carbonate complex solutions followed by calcination. During the synthesis process, ammonium carbonate played a pivotal role in hollow sphere formation through easy decomposition into CO2 and NH3 and enhancement of internal pressure of atomized droplets helped to overcome the crumbling effect of rGO. The synthesized hollow spheres are porous, made of 7–12 nm particles with an average diameter of 2–3 μm and a surface area of 76 m2 g−1 for pristine NiCo2O4 and 21 m2 g−1 for rGO–NiCo2O4. Observance of distinct redox peaks in cyclic voltammetry (CV) indicates that the electrochemical charge storage mechanism of NiCo2O4 is non-capacitive and somewhat battery type in nature. The synthesized rGO–NiCo2O4 hollow spheres showed a specific capacity as high as 427 C g−1 (971 F g−1) at a current density of 0.5 A g−1 which is much superior to that of pristine NiCo2O4 hollow spheres (183 C g−1). rGO–NiCo2O4 also exhibited an excellent rate performance with capacities of 385.3, 345.4, 256, 169 and 89 C g−1 at current densities of 1, 2, 5, 10 and 20 A g−1, respectively and 76% retention of capacity after 5000 cycles at 10 A g−1. Furthermore, studies on AC//rGO–NiCo2O4 asymmetric cells show that the energy storage performance of rGO–NiCo2O4 hollow spheres obtained by the present scalable and cost-effective process is quite comparable, or even superior to those reported for NiCo2O4 synthesized through sophisticated and costly synthetic protocols.

Transition-metal oxide hollow yolk–shell micro/nanostructures combined with a conducting substance have gained significant attention as efficient electrode materials for electrochemical energy storage applications due to their large surface area, internal void space, and structural stability. Herein, we report a facile aqueous solution-based soft template method using sucrose–CTAB for the synthesis of a hollow yolk–shell structure of carbon-incorporated MoO2 (C@MoO2) with a diameter of 0.9–1.1 μm, wall thickness of 100 nm, inner yolk size of 400–450 nm, and BET surface area of 40 m2 g−1. During the synthesis process, sucrose plays a dual role, both as a template and a carbon source. The electrochemical charge storage mechanism follows a battery-type behaviour when tested as a faradaic electrode in 3.0 M KOH electrolyte. C@MoO2 exhibits a high specific capacity of 188 C g−1 at the current density of 0.5 A g−1, good rate performance (50.6 C g−1 at 10 A g−1), and 78% retention of capacity after 5000 cycles at 5 A g−1. The obtained performance is superior to those obtained for pure MoO2 hollow spheres (137.1 C g−1 at 0.5 A g−1) as well as previously reported MoO2 and MoO3, indicating the potential applicability of the as-synthesised yolk–shell C@MoO2.

We report herein a facile metal–organic framework (MOF) derived route for the synthesis of carbon embedded CeO2 (CeO2@C) with a pre-designed shape-specific morphology by varying the organic linker and by using PVP as the structure directing agent. It is found that the general morphological features of the parent MOF are mimicked by the derived oxide. Four different linkers have been used to prepare CeO2@C particles with three different shapes – spherical, bar-shaped and thin plate-like. A probable formation mechanism is discussed based on metal–ligand coordination. Influence of the morphology on the electrochemical properties as a lithium-ion battery (LIB) anode has been studied in coin cells vs. Li/Li+. The spherically shaped CeO2@C-14 shows a superior performance with a maximum specific capacity of 715 mA h g−1 at 0.05 mA cm−2, good rate performance (413 mA h g−1 at 0.5 mA cm−2) and cycling stability (∼94% capacity retention after 100 cycles). The present results demonstrate that the major limitations of metal oxide anodes – volume expansion during lithiation/delithiation, rate performance and capacity fading upon cycling – could be overcome to a great extent by adopting the two-way approach of morphology design through the MOF route and in situ embedded carbon matrix.

Well-controlled hollow-porous nanostructures can provide enhanced charge storage capacity owing to the rapid diffusion of electrolyte ions into their interior. However, interface engineering of stable hollow-porous nanostructures with reversible faradaic reactions for efficient energy conversion/storage devices is still a challenge. Herein, we report solvothermal synthesis of spinel ZnMn2O4 with a hollow-porous spherical (ZMOHS) morphology. The formation mechanism of such a hierarchical nanostructure has been discussed. The ZMOHS exhibits a specific capacity of ~187 mAh g−1 at a current density of 2 A g−1 when tested as a faradaic electrode (vs Pt) for a rechargeable aqueous battery (RAB) in alkaline electrolyte. Furthermore, a full cell RAB constituting of ZMOHS//activated carbon (AC) demonstrates energy and power densities of ~215.7 Wh Kg−1 and ~1184.5 W kg−1 respectively, with ultra-long cycling stability (~106% capacitance retention after 10,000 cycles), making it a very promising material for next-generation energy storage device applications.

In continuation of the work on the stabilization of the electrochemical performance of Li and Mn‐rich LixNiyCozMnwO2 (HE‐NCM, x > 1, w > 0.5, x + y + z + w = 2) cathode materials via atomic layer deposition (ALD) surface coatings, herein, the active role of aluminum oxides‐based coatings, during prolonged cycling in battery prototypes with graphite anodes, is discussed. Notable progress in electrochemical cycling and rate performance of Na‐aluminate‐coated Li1.142Mn0.513Ni0.230Co0.115O2 cathode material is established. These coated electrodes delivered a stable discharge capacity of 145 mAh g−1 (66% retention), compared to only 118 mAh g−1 (55% retention) for the uncoated sample at a 1.0 C rate after 400 cycles. Steady average discharge potential, lower voltage hysteresis, and stable energy density profiles are the noteworthy achievements for the coated material during cycling. Significant improvement in the coated material's thermal stability compared with the uncoated one has also been confirmed. The present study also enlightens about the Na‐aluminate coating's orientation and distribution on HE‐NCM material's surface. 23Na and 27Al solid‐state nuclear magnetic resonance (NMR) studies reveal the Na‐aluminate coating's crystalline constituent's disappearance upon cycling. The partial dissolution of Na5AlO4 coating, followed by forming a secondary disordered edge‐site phase that remains even after long‐term cycling, is disclosed.

Ternary metal sulfides are emerging as a new class of electrochemical energy storage materials outperforming their oxide counterparts. We report here a facile and scalable solvothermal synthetic approach for growth of carbon doped MnCo 2 S 4 microcubes (edge length, 10 μm) directly on Ni foam. The simple approach of binder-free design, in-situ carbon doping and the use of 3D current collector resulted in an extraordinarily high specific capacity of 1892C g −1 (525.7 mAh g −1 ) at 5 A g −1 and outstanding rate performance of 516C g −1 (143.3 mAh g −1 ) at a very high current density of 100 A g −1 when tested as a faradaic electrode in aqueous KOH electrolyte. X-ray photoelectron spectroscopy (XPS) results indicate concurrent intercalation of both H + and OH − ions from the electrolyte during the electrochemical processes. In two-electrode symmetric MnCo 2 S 4 //KOH//MnCo 2 S 4 cells, mimicking the physical configuration of practical cells, specific capacity of 215C g −1 (59.7 mAh g −1 ) could be achieved at 1 A g −1 . Further, the symmetric cell delivers energy densities of 106.5 and 15.2 Wh kg −1 at power densities of 0.85 and 18 kW kg −1 demonstrating great application prospects.

Versatility and diversity in the nature of bonding between metal ions and polyfunctional organic molecules render metal organic frameworks (MOFs) as interesting materials for a variety of applications. In this work, we have examined the electrochemical properties of solvothermally synthesized Cu-1,3,5-benzenetricarboxylate MOF as a novel anode material for lithium-ion battery (LIB). At a current density of 96 mAg −1 , reversible capacity of 740 mAhg −1 is achieved, the highest ever reported for a MOF. Even at a high current density of 383 mAg −1 , specific capacity of 474 mAhg −1 is observed with no apparent fading up to 50 cycles. Ex-situ studies on the electrode material in the charged and discharged state by X-ray diffraction, Fourier transformed infra-red spectroscopy and X-ray photoelectron spectroscopy suggest that Li storage in Cu 3 (BTC) 2 MOF might not be fully explained by the conventional conversion mechanism that involves reduction into corresponding metal and subsequent oxidation. Rather, redox participation of the organic moiety is indicated. The present results would help in designing new MOFs for LIB applications.

In recent times, a great deal of attention has been paid to the balanced design and fabrication of core-shell heterostructures for enhanced pseudocapacitor (SC) performance. In this paper, we report the synthesis of ZnO@Co3O4 based core-shell heterostructures with controllable shell thickness for the first time by a simple low-temperature solution-based method and their detailed electrode performance as SC wherein a highly enhanced pseudocapacitance of 296 C g(-1) at a current density of 0.5 A g(-1) has been observed. Further, modifying the surface of ZnO by its sulfur analogue (i.e., by creating a ZnO/ZnS heterostructure), an improved capacitance of 317 C g(-1) at a current density of 0.5 A g(-1) for ZnO/ZnS@Co3O4 has been obtained along with a better rate performance. This is attributed to an efficient charge transfer from ZnS to ZnO. Impressively, the core-double shell heterostructure exhibits high energy density of 36 Wh kg(-1) at a power density of 204.3 W kg(-1). Even at a very high power density of 10.9 kW kg(-1), it shows an energy density of 14.7 Wh kg(-1). To the best of our knowledge, this is the first study of the electrochemical properties of ZnO/ZnS@Co3O4 heterostructure.

Tailoring the morphology of mesoporous nanostructures toward performance enhancement plays a key role in developing efficient energy storage devices. Herein, we report the formation of well crystallized Mn2O3 mesoporous nanobars through simple exo-templating of a manganese 1,3,5-benzenetricarboxylate metal–organic framework (Mn-BTC MOF) by thermal treatment whereby the general morphology of the parent MOF is conserved, but with more voids and spaces. The parent Mn-BTC MOF was synthesized by solvothermal reaction of trimesic acid with manganese nitrate in alcoholic solution. The MOF-derived Mn2O3 was characterized by XRD, field-emission SEM, high-resolution TEM, and N2 adsorption/desorption isotherm measurements. When examined as an anode material for lithium-ion batteries in the potential windows of 0.01–3.0 V and 0.01–2.0 V, high reversible specific capacities of 849 and 778 mAh g−1 were obtained. It was found that the electrochemical processes are more reversible when cycled in the 2 V window. A steady capacity of ∼410 mAh g−1 was observed after 300 continuous cycles at ∼C/5.5 exhibiting good cycling stability in the 2 V window. When tested as a pseudocapacitor electrode in a three-electrode configuration, a specific capacitance of 250 F g−1 at 0.2 A g−1 could be achieved. Further, to demonstrate practical applicability, two-electrode asymmetric supercapacitor pouch cells were assembled with Mn2O3 as the positive electrode and commercial activated carbon as the negative electrode which showed an ultrahigh energy density of 147.4 W h kg−1 at a power density of 1004 W kg−1. The present work shows the potential of a MOF derived route for obtaining metal oxides with desired nano-architectures for electrochemical applications with high performance.

Metal organic frameworks (MOFs) with diverse structural chemistry are being projected as futuristic electrode materials for Li-ion batteries. In this work, we report synthesis of Mn-1,3,5-benzenetricarboxylate MOF by a simple solvothermal method and its application as an anode material for the first time. Scanning electron microscopy of the synthesized MOF shows a bar shaped morphology where these bars, about 1 μm wide and of varied lengths between 2 and 20 μm, are made of porous sheets containing mesoporous walls and macroporous channels. The MOF anode, when examined in the potential window of 0.01-2.0 V versus Li/Li(+), shows high specific capacities of 694 and 400 mAh g(-1) at current densities of 0.1 and 1.0 A g(-1) along with good cyclability, retention of capacity, and sustenance of the MOF network. Ex situ X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy studies on the electrode material at different states of charge suggest that the usual conversion reaction for Li storage might not be applicable in this case. Conjugated carboxylates being weakly electron withdrawing ligands with a stronger π-π interaction, a probable alternative Li storage mechanism has been proposed that involves the organic moiety. The present results show promise for applying Mn-1,3,5-benzenetricarboxylate MOF as high performance2 V anode.

Use of room temperature ionic liquids (ILs) as electrolytes with a wider potential window offers scope for developing high energy density supercapacitors for efficient energy storage. In this work, a comparative study on the performance of nanostructured MnO2 hollow spheres as electrochemical supercapacitor was made by fabricating activated carbon (AC)//MnO2 asymmetric supercapacitor cells using imidazolium-based ILs as electrolytes. Mesoporous MnO2 hollow spheres were synthesized through a simple low temperature (80 °C) solvothermal method by reduction of KMnO4 under acidic condition in presence of Cu3(1,3,5-benzenetricarboxylate)2 metal organic framework (MOF) in the precursor solution, which acts as the source of Cu2+ playing a crucial role for the formation of the hollow spheres. Four different ILs were investigated from combinations of two different cations [1-ethyl-3-methylimidazolium (EMI+) and 1-butyl-3-methylimidazolium (BMI+)] and four different anions [hexaflurophosphate (PF6−), tetrafluoroborate (BF4−), trifluromethanesulfonate (Otf−) and bis(trifluromethylsulfonyl)imide (TFSI−)]. Influences of the physico-chemical properties such as ionic size, nucleophilicity, viscosity of the IL on the electrochemical properties are discussed. A high energy density of 163 W h kg−1, which is comparable to the energy density of a lithium-ion battery, could be achieved with EMIMBF4 as electrolyte. The present findings would help in further research for developing IL-based supercapacitors.

Developing new materials for electrochemical supercapacitors with higher energy density has recently gained tremendous impetus in the context of effective utilization of renewable energy. Herein, we report a simple one-pot synthesis of bundled nanorods of Cu(OH)2 embedded in a matrix of reduced graphene oxide (Cu(OH)2@RGO) under mild hydrothermal conditions of 80 °C for 1 h. The synthesized material shows a high BET surface area of 78.7 m(2) g(-1) and a mesoporous nature with a broad pore-size distribution consisting of structural pores as well as inter-particle pores. Raman spectroscopy suggests an intimate interaction between Cu(OH)2 and reduced graphene oxide (RGO) creating more defects by destruction of sp(2) domains which would help the defect-assisted charge transport during electrochemical processes. When investigated as an electrochemical supercapacitor, Cu(OH)2@RGO shows a high capacitance of 602 F g(-1) at 0.2 A g(-1) in 1 M KOH in a three-electrode cell configuration. Detailed electrochemical studies indicate that the Faradic processes are diffusion controlled and follow a quasi-reversible kinetics. Further, a two-electrode symmetric cell shows good energy density and power density (84.5 Wh kg(-1) at 0.55 kW kg(-1) and 20.5 Wh kg(-1) at 5.5 kW kg(-1)) characteristics demonstrating superior application potential of this common low-cost transition metal hydroxide for high performance energy storage devices.

Conversion electrodes, the materials of choice for the next generation lithium-ion battery (LIB), are mainly limited to metal oxides. In this work, we have investigated the electrochemical performance of chemically synthesized Cu(OH)2 nanoflower arrays. A 50 : 50 composite of Cu(OH)2 and multiwalled carbon nanotubes (MWCNTs) showed a reversible capacity of 522 mA h g−1 at a current density of 0.1 mA cm−2 with 95% retention of capacity after 50 cycles. The results demonstrate that it can be a competitive choice over the corresponding oxides as an anode for LIB.

Low electronic conductivity and slow faradic processes limit the performance of MnO2 as an electrochemical pseudocapacitor with respect to cycling and power density. Herein, we report preparation of single-phase α-MnO2, composed of an interconnected nanowire network with "cocoonlike" morphology, and its application as electrode in a symmetric aqueous supercapacitor. Increased "effective" surface area, coexistence of micropores and mesopores, and enhanced electron transport in these nanowire networks result in a specific pseudocapacitance (CS) of 775 F·g(-1) in 3 M KOH, derived from cyclic voltammetry in the potential window of -1 to +1 V at a scan rate of 2 mV·s(-1), the highest reported for two-electrode symmetric configuration. Furthermore, introduction of K4Fe(CN)6 as a redox-active additive to KOH results in ∼7 times increase in energy density at a power density of ∼6000 W·kg(-1). The presence of the Fe(CN)6(4-)/Fe(CN)6(3-) redox couple provides an electron buffer source compensating for the slow faradic reactions. The results demonstrate that this simple approach might be an effective way to enhance the redox kinetics and reversibility of transition metal oxide-based pseudocapacitors.

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.

Exploring new electrode materials is the key to realize high performance energy storage devices for effective utilization of renewable energy. Natural clays with layered structure and high surface area are prospective materials for electrical double layer capacitors (EDLC). In this work, a novel hybrid composite based on acid-leached montmorillonite (K10), multi-walled carbon nanotube (MWCNT) and manganese dioxide (MnO2) was prepared and its electrochemical properties were investigated by fabricating two-electrode asymmetric supercapacitor cells against activated carbon (AC) using 1.0M tetraethylammonium tetrafluroborate (Et4NBF4) in acetonitrile (AN) as electrolyte. The asymmetric supercapacitors, capable of operating in a wide potential window of 0.0-2.7V, showed a high energy density of 171Whkg(-1) at a power density of ∼1.98kWkg(-1). Such high EDLC performance could possibly be linked to the acid-base interaction of K10 through its surface hydroxyl groups with the tetraethylammonium cation [(C2H5)4N(+) or TEA(+)] of the ionic liquid electrolyte. Even at a very high power density of 96.4kWkg(-1), the cells could still deliver an energy density of 91.1Whkg(-1) exhibiting an outstanding rate capability. The present study demonstrates for the first time, the excellent potential of clay-based composites for high power energy storage device applications.

MOF derived CeO2 showed a pseudocapacitance of 1204 F g(-1) at 0.2 A g(-1), far exceeding its theoretical capacitance (560 F g(-1)). The present study demonstrates that combination of a two-way strategy, controlled nano-architecture and redox active electrolyte additive, could potentially alleviate both low energy density and capacitance fading issues plaguing the current metal oxide pseudocapacitors.

The authors report a novel strategy to fabricate electrospun anatase TiO2–rGO composite nanofibers with 3D cubic ordered mesoporosity. Such synthesis route not only ensures molecular level composite formation between rGO and TiO2 but also retains the rGO content and orders mesostructure after calcination of the nascent fiber at an optimum condition that only removes the surfactant and polymer. Transmission electron microscopic and low angle X-ray diffraction studies confirm the presence of ordered mesoporosity within the nanofibers. Raman and X-ray photoelectron spectroscopy studies reveal the molecular level composite formation between rGO and TiO2 with chemical bonding. This composite nanofiber with high surface area (155 m2 g–1) is tested as an anode material in lithium-ion batteries. Intrinsically formed TiO2–rGO composite structural features with channel like interconnected 3D order mesopores within 1D fibrous morphology help in achieving 94% of the theoretical capacity (335 mAh g–1 for one electron transfer) at a current density of 16.75 mA g–1, the highest reported so far. It shows specific capacity of 212 and 168 mAh g–1 even at moderately high current densities of 335 and 838 mA g–1, respectively. Moreover, 85.3% of capacity retains after 500 continuous discharge/charge cycles at 335 mA g–1.

In this paper, a set of 21 variables have been identified that affects the dividend payout by a company. Also a set of variables in terms of ratios or financial report figures have been identified that represent these variables. Data of 15 different companies from the First Moving Consumer Goods (FMCG) sector in India has been extracted for the years 2006-2011 and these variables are calculated for each of the companies. Firstly factor analysis has been performed on the different variables identified. Then multiple regression is conducted on these factors to identify the determinants of dividend decisions in the FMCG sector in India.