Microwave driven hydrothermal synthesis of LiMn2O4 nanoparticles as cathode material for Li-ion batteries

Among the various cathode materials studied for Li-ion batteries over the past many years, spinet LiMn2O4 is found to be one of the most attractive materials. Nanoparticles of the electrode materials sustain high rate capability due to large surface to volume ratio and small diffusion path length. Nanoparticles of spinel LiMn2O4 have been synthesized by microwave hydrothermal technique using prior synthesized amorphous MnO2 and LiOH. The phase and purity of spinel LiMn2O4 are confirmed by powder X-ray diffraction. The morphological studies have been investigated using field emission scanning electron microscopy and high-resolution transmission electron microscopy. The electrochemical performances of the material for Li insertion/extraction are evaluated by cyclic voltammetry, galvanostatic charge-discharge cycling and AC impedance studies. The initial discharge capacity is found to be about 89 mAh g(-1) at current density of 21 mA g(-1). (C) 2010 Elsevier B.V. All rights reserved.

A crosslinked ``polymer-gel'' rechargeable lithium-ion battery electrolyte from free radical polymerization using nonionic plastic crystalline electrolyte medium

A cross-linked polymer-gel soft matter electrolyte with superior electrochemical, thermal and mechanical properties obtained from free radical polymerization of vinyl monomers in a semi-solid organic nonionic plastic crystalline electrolyte for application in rechargeable lithium-ion batteries is discussed here.

Effect of Li+-ion on enhancement of photoluminescence in Gd2O3:Eu3+ nanophosphors prepared by combustion technique

Gd2O3:Eu3+ (4 mol%) nanophosphor co-doped with Li+ ions have been synthesized by low-temperature solution combustion technique in a short time. Powder X-ray diffractometer (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-VIS and photoluminescence (PL) techniques have been employed to characterize the synthesized nanoparticles. It is found that the lattice of Gd2O3:Eu3+ phosphor transforms from monoclinic to cubic as the Li+-ions are doped. Upon 254 nm excitation, the phosphor showed characteristic luminescence D-5(0) -> F-7(J) (J= 0-4) of the Eu3+ ions. The electronic transition located at 626 nm (D-5(0) -> F-7(2)) of Eu3+ ions was stronger than the magnetic dipole transition located at 595 nm (D-5(0) -> F-7(1)). Furthermore, the effects of the Li+ co-doping as well as calcinations temperature on the PL properties have been studied. The results show that incorporation of Li+ ions in Gd2O3:Eu3+ lattice could induce a remarkable improvement of their PL intensity. The emission intensity was observed to be enhanced four times than that of with out Li+-doped Gd2O3:Eu3+. (C) 2010 Elsevier B.V. All rights reserved,

High energy Li ion irradiation effects in ferroelectric PZT and SBT thin films

The ferroelectric Pb(Zr0.53Ti0.47)O-3 (PZT) and SrBi2Ta2O9 (SBT) thin films were prepared by laser ablation technique. The dielectric analysis, capacitance-voltage, ferroelectric hysteresis and DC leakage current measurements were performed before and after 50 MeV Li3+ ion irradiation. In both thin films, the irradiation produced some amount of amorphisation, considerable degradation in the ferroelectric properties and change in DC conductivity. On irradiation of these thin films, the phase transition temperature [T-c] of PZT decreased considerably from 628 to 508 K, while SBT exhibited a broad and diffuse transition with its T-c decreased from 573 to 548 K. The capacitance-voltage curve at 100 kHz showed a double butterfly loop with a large decrease in the capacitance and switching voltage. There was decrease in the ferroelectric hysteresis loop, remanant polarisation and coercive field. After annealing at a temperature of 673 K for 10 min while PZT partially regained the ferroelectric properties, while SBT did not. The DC conductivity measurements showed a shift in the onset of non-linear conduction region in irradiated SBT. The degradation of ferroelectric properties of the irradiated thin films is attributed to the irradiation-induced partial amorphization and the pinning of the ferroelectric domains by trapped charges. The regaining of properties after annealing is attributed to the thermal annealing of the defects generated during the irradiation. (C) 2003 Elsevier Science B.V. All rights reserved.

Nitrates-melt synthesized LiNi0.8Co0.2O2 and its performance as cathode in Li-ion cells

Layered LiNi0.8Co0.2O2 crystallizing in R (3) over barm space group is synthesized by decomposing the constituent metal-nitrate precursors. Oxidizing nature of metal nitrates stabilizes nickel in +3 oxidation state, enabling a high degree of cation ordering in the layered LiNi0.8Co0.2O2. The powder sample characterized by XRD Rietveld refinement reveals <2% Li-Ni site exchange in the layers. Scanning electron microscopic studies on the as-synthesized LiNi0.8Co0.2O2 sample reflect well defined particles of cubic morphology with particle size ranging between 200 and 250 nm. Cyclic voltammograms suggest that LiNi0.8Co0.2O2 undergoes phase transformation on first charge with resultant phase being completely reversible in subsequent cycles. The first-charge-cycle phase transition is further supported by impedance spectroscopy that shows substantial reduction in resistance during initial de-intercalation. Galvanostatic charge-discharge cycles reflect a first-discharge capacity of 184 mAh g(-1) which is stabilized at 170 mAh g(-1) over 50 cycles.

Benefits of Electronic Wiring and Spacers on Lithium Storage in Nanostructured Lithium-Ion Battery Anodes

The demand for high power density lithium-ion batteries (LIBs) for diverse applications ranging from mobile electronics to electric vehicles have resulted in an upsurge in the development of nanostructured electrode materials worldwide. Graphite has been the anode of choice in commercial LiBs. Due to several detrimental electrochemical and environmental issues, efforts are now on to develop alternative non-carbonaceous anodes which are safe, nontoxic and cost effective and at the same time exhibit high lithium storage capacity and rate capability. Titania (TiO2) and tin (Sn) based systems have gained much attention as alternative anode materials. Nanostructuring of TiO2 and SnO2 have resulted in enhancement of structural stability and electrochemical performances. Additionally, electronic wiring of mesoporous materials using carbon also effectively enhanced electronic conductivity of mesoporous electrode materials. We discuss in this article the beneficial influence of structural spacers and electronic wiring in anatase titania (TiO2) and tin dioxide (SnO2).

Li diffusion through doped and defected graphene

We investigate the effect of nitrogen and boron doping on Li diffusion through defected graphene using first principles based density functional theory. While a high energy barrier rules out the possibility of Li-diffusion through the pristine graphene, the barrier reduces with the incorporation of defects. Among the most common defects in pristine graphene, Li diffusion through the divacancy encounters the lowest energy barrier of 1.34 eV. The effect of nitrogen and boron doping on the Li diffusion through doped defected-graphene sheets has been studied. N-doping in graphene with a monovacancy reduces the energy barrier significantly. The barrier reduces with the increasing number of N atoms. On the other hand, for N doped graphene with a divacancy, Li binds in the plane of the sheet, with an enhanced binding energy. The B doping in graphene with a monovacancy leads to the enhancement of the barrier. However, in the case of B-doped graphene with a divacancy, the barrier reduces to 1.54 eV, which could lead to good kinetics. The barriers do not change significantly with B concentration. Therefore, divacancy, B and N doped defected graphene has emerged as a better alternative to pristine graphene as an anode material for Li ion battery.

Polymer template-assisted microemulsion synthesis of large surface area, porous Li2MnO3 and its characterization as a positive electrode material of Li-ion cells

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 A degrees 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.

Green ionothermal synthesis of hierarchical nanostructures of SnS2 and their Li-ion storage properties

Flower-like hierarchical architectures of layered SnS2 have been synthesized ionothermally for the first time, using a water soluble EMIM]BF4 ionic liquid (IL) as the solvent medium. At lower reaction temperatures, the hierarchical structures are formed of few-layered polycrystalline 2D nanosheet-petals composed of randomly oriented nanoparticles of SnS2. The supramolecular networks of the IL serve as templates on which the nanoparticles of SnS2 are glued together by combined effects of hydrogen bonding, electrostatic, hydrophobic and imidazolium stacking interactions of the IL, giving rise to polycrystalline 2D nanosheet-petals. At higher reaction temperatures, single crystalline plate-like nanosheets with well-defined crystallographic facets are obtained due to rapid inter-particle diffusion across the IL. Efficient surface charge screening by the IL favors the aggregation of individual nanosheets to form hierarchical flower-like architectures of SnS2. The mechanistic aspects of the ionothermal bottom-up hierarchical assembly of SnS2 nanosheets are discussed in detail. Li-ion storage properties of the pristine SnS2 samples are examined and the electrochemical performance of the sample synthesized at higher temperatures is found to be comparable to that reported for pristine SnS2 samples in the literature.

Phase and Dimensionality of Tin Oxide at graphene nanosheet array and its Electrochemical performance as anode for Lithium Ion Battery

We incorporated tin oxide nanostructures into the graphene nanosheet matrix and observed that the phase of tin oxide varies with the morphology. The highest discharge capacity and coulumbic efficiency were obtained for SnO phase of nanoplates morphology. Platelet morphology of tin oxide shows more reversible capacity than the nanoparticle (SnO2 phase) tin oxide. The first discharge capacity obtained for SnO@GNS is 1393 and 950 mAh/g for SnO2@GNS electrode at a current density of 23 mu A/cm(2). A stable capacity of about 1022 and 715 mAh/g was achieved at a current rate of 23 mu A/cm(2) after 40 cycles for SnO@GNS and SnO2@GNS anodes, respectively. (C) 2014 Elsevier Ltd. All rights reserved.

A 3.8-V earth-abundant sodium battery electrode

Rechargeable lithium batteries have ushered the wireless revolution over last two decades and are now matured to enable green automobiles. However, the growing concern on scarcity and large-scale applications of lithium resources have steered effort to realize sustainable sodium-ion batteries, Na and Fe being abundant and low-cost charge carrier and redox centre, respectively. However, their performance is limited owing to low operating voltage and sluggish kinetics. Here we report a hitherto-unknown material with entirely new composition and structure with the first alluaudite-type sulphate framework, Na2Fe2(SO4)(3), registering the highest-ever Fe3+/ Fe2+ redox potential at 3.8V (versus Na, and hence 4.1V versus Li) along with fast rate kinetics. Rare-metal-free Na-ion rechargeable battery system compatible with the present Li-ion battery is now in realistic scope without sacrificing high energy density and high power, and paves way for discovery of new earth-abundant sustainable cathodes for large-scale batteries.

Porous Flower-like alpha-Fe2O3 Nanostructure: A High Performance Anode Material for Lithium-ion Batteries

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.

Improved capacity and stability of integrated Li and Mn rich layered-spinel Li1.17Ni0.25Mn1.08O3 cathodes for Li-ion batteries

A Li-rich layered-spinel material with a target composition Li1.17Ni0.25Mn1.08O3 (xLiLi1/3Mn2/3]O-2.(1 - x) LiNi0.5Mn1.5O4, (x = 0.5)) was synthesized by a self-combustion reaction (SCR), characterized by XRD, SEM, TEM, Raman spectroscopy and was studied as a cathode material for Li-ion batteries. The Rietveld refinement results indicated the presence of monoclinic (LiLi1/3Mn2/3]O-2) (52%), spinel (LiNi0.5Mn1.5O4) (39%) and rhombohedral LiNiO2 (9%). The electrochemical performance of this Li-rich integrated cathode material was tested at 30 degrees C and compared to that of high voltage LiNi0.5Mn1.5O4 spinel cathodes. Interestingly, the layered-spinel integrated cathode material exhibits a high specific capacity of about 200 mA h g(-1) at C/10 rate as compared to 180 mA h g(-1) for LiNi0.5Mn1.5O4 in the potential range of 2.4-4.9 V vs. Li anodes in half cells. The layered-spinel integrated cathodes exhibited 92% capacity retention as compared to 82% for LiNi0.5Mn1.5O4 spinel after 80 cycles at 30 degrees C. Also, the integrated cathode material can exhibit 105 mA h g(-1) at 2 C rate as compared to 78 mA h g(-1) for LiNi0.5Mn1.5O4. Thus, the presence of the monoclinic phase in the composite structure helps to stabilize the spinel structure when high specific capacity is required and the electrodes have to work within a wide potential window. Consequently, the Li1.17Ni0.25Mn1.08O3 composite material described herein can be considered as a promising cathode material for Li ion batteries.

Energy-savvy solid-state and sonochemical synthesis of lithium sodium titanate as an anode active material for Li-ion batteries

Lithium sodium titanate insertion-type anode has been synthesized by classical solid-state (dry) and an alternate solution-assisted (wet) sonochemical synthesis routes. Successful synthesis of the target compound has been realized using simple Na- and Li-hydroxide salts along with titania. In contrast to the previous reports, these energy-savvy synthesis routes can yield the final product by calcination at 650 -750 degrees C for limited duration of 1-10 h. Owing to the restricted calcination duration (dry route for 1-2 h and wet route for 1-5 h), they yield homogeneous nanoscale lithium sodium titanate particles. Sono-chemical synthesis reduces the lithium sodium titanate particle size down to 80-100 nm vis-a-vis solid-state method delivering larger (200-500 nm) particles. Independent of the synthetic methods, the end products deliver reversible electrochemical performance with reversible capacity exceeding 80 mAh.g(-1) acting as a 1.3 V anode for Li-ion batteries. (C) 2015 Elsevier B.V. All rights reserved.

Flower-like porous cobalt(II) monoxide nanostructures as anode material for Li-ion batteries

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.