Fully activated Li 2 MnO 3 nanoparticles were prepared by a chemical based oxidation reaction. All of the diffraction peaks of the prepared samples were well matched to a monoclinic phase (space group: C2/m) with no impurity peaks and refined using the General Structure Analysis System (GSAS) program. The activated Li 2 MnO 3 sample showed homogeneously well-dispersed nanoparticles with a size of $10 nm. The oxidation state of Mn was confirmed by XPS. The activated Li 2 MnO 3 nanoparticles delivered a high charge capacity of 302 mA h g À1 above 4.5 V and discharge capacity of 236 mA h g À1 during the first cycle. Interestingly, the cycle performance of the activated Li 2 MnO 3 nanoparticles during extended cycles exhibited somewhat stable discharge capacities without any drastic capacity fading, even when cycled in the high voltage range of 2.0-4.9 V and after the phase transition to spinel. In terms of the rate performance, the activated Li 2 MnO 3 sample exhibited significantly superior properties compared to the bulk Li 2 MnO 3 sample, probably due to the nano-size particles with high crystallinity.

Despite nanomaterials with unique properties playing a vital role in scientific and technological advancements of various fields including chemical and electrochemical applications, the scope for exploration of nano-scale applications is still wide open. The intimate correlation between material properties and synthesis in combination with the urgency to enhance the empirical understanding of nanomaterials demand the evolution of new strategies to promising materials. Herein we introduce a rapid pyro-synthesis that produces highly crystalline functional nanomaterials under reaction times of a few seconds in open-air conditions. The versatile technique may facilitate the development of a variety of nanomaterials and, in particular, carbon-coated metal phosphates with appreciable physico-chemical properties benefiting energy storage applications. The present strategy may present opportunities to develop “design rules” not only to produce nanomaterials for various applications but also to realize cost-effective and simple nanomaterial production beyond lab-scale limitations.

No abstract

Li 4 Ti 5 O 12 was successfully synthesized by solvothermal techniques using cost-effective precursors in polyol medium. The x-ray diffraction ͑XRD͒ pattern of the sample ͑LTO-500͒ was clearly indexed to the spinel shaped Li 4 Ti 5 O 12 and in order to accurately determine the lattice parameters, synchrotron powder XRD pattern was fitted by the whole-pattern profile matching method using the model space group, Fd3m. The particle size, morphology, and crystallinity of LTO-500 were identified using field-emission scanning electron microscopy and transmission electron microscopy. The electrochemical performance of the sample revealed fairly high initial discharge/charge specific capacities of 230 and 179 mAh/g, respectively, and exhibited highly improved rate performances at C-rates as high as 30 and 60 C, when compared to Li 4 Ti 5 O 12 by the solid-state reaction method. This was attributed to the achievement of small particle sizes in nanoscale dimensions, a reasonably narrow particle size distribution and, hence, shorter diffusion paths combined with larger contact area at the electrode/electrolyte interface.

Reduced graphene oxide (rGO) sheets were synthesized by a modified Hummer's method without additional reducing procedures, such as chemical and thermal treatment, by appropriate drying of graphite oxide under ambient atmosphere. The use of a moderate drying temperature (250°C) led to mesoporous characteristics with enhanced electrochemical activity, as confirmed by electron microscopy and N 2 adsorption studies. The dimensions of the sheets ranged from nanometres to micrometres and these sheets were entangled with each other. These morphological features of rGO tend to facilitate the movement of guest ions larger than Li + . Impressive electrochemical properties were achieved with the rGO electrodes using various charge-transfer ions, such as Li + , Na + and K + , along with high porosity. Notably, the feasibility of this system as the carbonaceous anode material for sodium battery systems is demonstrated. Furthermore, the results also suggest that the high-rate capability of the present rGO electrode can pave the way for improving the full cell characteristics, especially for preventing the potential drop in sodium-ion batteries and potassium-ion batteries, which are expected to replace the lithium-ion battery system

Nano-LiFePO 4 possessing plate, rod and multi shaped morphologies are synthesized by a low temperature solvothermal route. The prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies. The XRD patterns indicate the formation of phase-pure orthorhombic olivine structure designated to the space group of Pnma. Synthesized samples reveal plate, rod and multi-morphous (a combination of plate, rod and spherical shaped particles) morphologies, respectively, in the SEM study. The growth of the plate-type olivine nanocrystals is identified to be along [100] and [010] crystallographic directions while the rod-shaped particles indicate growth along the crystallographic ac planes, as estimated from the TEM studies. The first discharge capacities of the olivine with plate-type, rod-type, and multi-morphous olivine samples are 131, 144, and 161 mAhg À1 with minimal capacity fading for deeply extended cycles, respectively. Especially, in rate performance, the multi-morphous LiFePO 4 sample having mixed morphologies maintains capacity of about 110 mAh g À1 until 8 C rates, while the plate and rod samples show severe capacity decline at corresponding rates. The reason for the high rate-performance of multi-morphous LiFePO 4 cathode is ascertained to the nano-sized particles and enhanced intimate connectivity between the multi-shaped nanoparticles.Orthorhombic olivine structure LiFePO 4 is intensively investigated as the most attractive cathode to replace commercialized LiCoO 2 in rechargeable lithium-ion batteries because it is not only inexpensive, nontoxic, and environmentally benign but also has relatively high theoretical capacity of 170 mAh g À1 and a suitably flat voltage-region of 3.45 V within the electrolyte window. 1 However, despite these advantages, its unimpressive rate performance due to intrinsic problems of low ionic and electronic conductivities still remain as a major obstacle for commercial applications. Progressive efforts to circumvent this obstacle by carbon coating on particle surface, 2 developing composites via mixing conductive materials, 3 aliovalent cation substitution, 4 particle-size minimization, 5,6 and customizing particle morphologies 7-11 have been undertaken.Among these approaches, with respect to Li-ion batteries, nanosized electrodes have been intensively investigated for high power density applications as the advantage of using such electrodes remains two-fold. 12,13 Firstly, nanomaterials provide a favorable structural framework that ensures shorter diffusion paths for the Liions to traverse from the core of the particles to the surface through the lattice, thereby yielding excellent electrochemical properties. Secondly, the large surface area of nanomaterials ensures enhanced electrode/electrolyte interfacial contact, thus leading to higher charge/discharge rates and good capacity retentions. 14,15 In addition, it is also evident that customizing particle morphologies is becoming highly important si...

Mo doped Li excess transition metal oxides formulated as 0.3Li[Li(0.33)Mn(0.67)]O(2)·0.7Li[Ni(0.5-x)Co(0.2)Mn(0.3-x)Mo(2x)]O(2) were synthesized using the co-precipitation process. The effects of the substitution of Ni and Mn with Mo were investigated for the density of the states, the structure, cycling stability, rate performance and thermal stability by tools such as first principle calculations, synchrotron X-ray diffraction, field-emission SEM, solid state (7)Li MAS nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), elemental mapping by scanning TEM (STEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and a differential scanning calorimeter (DSC). It was confirmed that high valence Mo(6+) doping of the Li-excess manganese-nickel-cobalt layered oxide in the transition metal enhanced the structural stability and electrochemical performance. This increase was due to strong Mo-O hybridization inducing weak Ni-O hybridization, which may reduce O(2) evolution, and metallic behavior resulting in a diminishing cell resistance.

No abstract