Electrochemical performance of hybrid supercapacitor (HSC) utilizing surface sculpted Li4Ti5O12 (LTO) insertion electrode having nanoplatelet-like morphology and activated carbon (AC) electrode is investigated for energy storage application. Cyclic voltammetry (CV) at variable scan rates 0.5 to 60 mV.s-1 in the 0-3.2 V range show pseusocapacitive behavior and fast rate of current change indicating rapid Faradaic kinetics. Nyquist impedance study show charge transfer resistance due to kinetic effects of electron transfer and Li+ de-intercalation process at the LTO anode. Low capacity (0.2 C-1C) charge-discharge (CD) curves show high Coulomb efficiency with marginal reduction at high 5-10 C rates due to irreversibility of adsorbed PF6 anions at the electrolyte-AC interface. Galvanostatic CD cycling tests over 50 cycles at different C-rates show decline in storage capacity due to electrode polarization effects. Reduction, broadening and shift of the Raman line at 678 cm-1 from Ti-O bonds in TiO6 octahedra after cycling indicates Li insertion reactions in functioning of hybrid supercapacitor. The hybrid supercapacitor cells have shown energy density, 29 Wh.kg-1 and power density, 350 W.kg-1.

Aluminum–silicon alloys are an important class of commercial casting materials having wide applications in automotive and aerospace industries. Etching the Al–Si eutectic leads to selective dissolution of Al, resulting in novel morphology – macroporous Si spheres with a three-dimensional nano network. Up to 5% Al is dissolved in Si, leading to an expansion of the crystal lattice. The resulting porous Si is electrochemically active with lithium and thus can be used as a high capacity anode for lithium-ion batteries. The etching of Al–Si provides a simple and low-cost method of producing nano-structured Si materials.

LiFePO4 has shown considerable promise as a cathode material in Li-ion batteries due to its stability, low toxicity and high cyclability. However, the data on thermodynamic stability of olivine phase FePO4 (o-FePO4), the delithiated form of o-LiFePO4, remains scarce and contradictory. In this work, o-FePO4 was synthesized by chemical delithiation of o-LiFePO4 and characterized structurally and thermally. X-ray diffraction and absorption data indicate pure olivine phase, but with residual amount of Fe2+, most likely due to incomplete delithiation. Differential scanning calorimetry and thermal gravimetric analysis reveal that o-LixFePO4 decomposes exothermally above 550 °C with about 9% weight loss, the products being trigonal phase FePO4, Fe7(PO4)6, and LiPO3.

Flywheel energy storage systems use the kinetic energy stored in a rotor; they are often referred to as mechanical batteries. On charging, the fywheel is accelerated, and on power generation, it is slowed. Because the energy stored is proportional to the square of the speed, very high speeds are used, typically 20,000–100,000 revolutions per minute (rpm). To minimize energy loss due to friction, the rotors are spun in a vacuum and use magnetic bearings. The rotors today are typically made of high-strength carbon composites. One of the main limits to fywheels is the strength of the material used for the rotor: the stronger the rotor, the faster it can be spun, and the more energy it can store.

During the past two decades, the demand for the storage of electrical energy has mushroomed both for portable applications and for static applications. As storage and power demands have increased predominantly in the form of batteries, the system has evolved. However, the present electrochemical systems are too costly to penetrate major new markets, still higher performance is required, and environmentally acceptable materials are preferred. These limitations can be overcome only by major advances in new materials whose constituent elements must be available in large quantities in nature; nanomaterials appear to have a key role to play. New cathode materials with higher storage capacity are needed, as well as safer and lower cost anodes and stable electrolyte systems. Flywheels and pumped hydropower also have niche roles to play.

Vanadium oxide nanorods intercalated with lithium cations have been successfully formed by the hydrothermal treatment of electrospun precursors. The novelty of this synthesis method is the control of the morphology of the vanadium nanorod precursor by the electrospinning process, and then to convert to the desired compound with loss of the organic polymer while maintaining the morphology through a hydrothermal treatment. Transmission llectron microcopy shows that the single nanorods formed have a square shape cross-section with a width of less than 100nm. Electron diffraction shows that each nanorod is a single crystal, and X-ray diffraction shows that the nanorods have a layered structure with a 10.5 Å layer spacing. Their characterization, magnetic and electrochemical behavior and variable chemical composition are described together with the opportunities electrospinning presents for forming novel materials.

Li1+z[Ni0.45Mn0.45Co0.1]1-zO2(0.8≤1+z≤1.2) has been synthesized by the co-precipitation method. It was found that 5% excess lithium must be added to obtain the desired composition. XRD results show that an apparent single-phase structure appears except for the lowest lithium content. The layered character of the structure increases with increasing lithium content and Rietveld refinement reveals that cation disorder decreases rapidly as more lithium is added. This conclusion is further confirmed by magnetic studies in which only Li0.8[Ni0.45Mn0.45Co0.1]1.2O2 and Li0.9(Ni0.45Mn0.45Co0.1)1.1O2 show magnetization hysteresis loops. The electrochemical behavior of this series of samples is compared to figure out the best lithium to transition metal ratio.

This study focusses on optimizing the parameters of the hydrothermal synthesis to produce iron phosphates for lithium ion batteries, with an emphasis on pure LiFePO4 with the olivine structure and compounds containing a higher iron:phosphate ratio. Lithium iron phosphate (LiFePO4) is a promising cathode candidate for lithium ion batteries due to its high theoretical capacity, environmentally benign and the low cost of starting materials. Well crystallized LiFePO4 can be successfully synthesized at temperatures above 150 °C. The addition of a reducing agent, such as hydrazine, is essential to minimize the oxidation of ferrous (Fe2+) to ferric (Fe3+) in the final compound. The morphology of LiFePO4 is highly dependent on the pH of the initial solution. This study also investigated the lipscombite iron phosphates of formula Fe1.33PO4OH. This compound has a log-like structure formed by Fe-O octahedral chains. The chains are partially occupied by the Fe3+ sites, and these iron atoms and some of the vacancies can be substituted by other cations. Most of the protons can be ion-exchanged for lithium, and the electrochemical capacity is much increased.

The magnetic properties of layered LiNi0.5Mn0.5O2 and NaNi0.5Mn0.5O2 cathode materials are studied using AC susceptibility and DC magnetization techniques in order to elucidate magnetic interactions within transition metal (TM) layers and between them in samples with various TM distributions. In NaNi0.5Mn0.5O2 antiferromagnetic (AF) ordering transition is found at 60 K and a spin-flop transition at high magnetic field. In LiNi0.5Mn0.5O2 obtained by ion exchange from NaNi0.5Mn0.5O2 ferrimagnetic ordering is found at around 100 K. The saturation magnetization and the hysteresis loop size of ion-exchanged compounds vary from sample to sample, which implies that the Ni2+ ions migrate upon ion exchange process. Magnetic properties of high-temperature and ion-exchanged LiNi0.5Mn0.5O2 are compared; magnetic ordering models for all compounds are proposed based on experimental results and Goodenough-Kanamori rules.

Well-crystalline LiFePO4 particles were successfully prepared in the temperature range between 120 and 220°C, and complete ion ordering was obtained above 175°C where the unit cell dimensions were identical to high temperature material. The use of a soluble reductant, such as sugar or ascorbic acid, was found to minimize the oxidation of the iron to ferric. The electronic conductivity was enhanced by the deposition of carbon from the sugar, or by the addition of carbon nanotubes to the hydrothermal reactor when over 90% of the lithium could be de-intercalated electrochemically. We have extended the hydrothermal synthesis method to the Mn, Co and Ni analogs as well as to the mixed phosphates, such as LiMnyFe1-yPO4.

The carbon anode presently used in commercial lithium ion batteries has a relatively low capacity and may pose safety problems particularly under fast charging. Nanosized amorphous materials have excellent electrochemical behavior when applied as anodes for lithium ion batteries; especially they have advantages over bulk materials on capacity retention and rate capability. The initial studies on some amorphous compounds are promising. A commercialized tin-cobalt-carbon amorphous material, which is composed of ∼5nm nanoparticles, shows a capacity retention of >350 mAh/g for 50+ cycles. Manganese oxide nanofibers were synthesized by polymer templated electrospinning followed by calcinations. The fibers have 200-500 nm diameter and the main composition is Mn3O4. The capacity remains 400 mAh/g for at least 50 cycles.

A better understanding of magnetic interactions, charge distribution, and redox properties of vanadium oxide nanotubes (VONTs) is necessary for accurate structure and mechanism of formation determination. Magnetic properties have been determined for pristine and lithiated VONTs and for the VONTs arranged in nanourchin morphology. Presence of paramagnetic V4+ ions and V4+ ions coupled in magnetic dimers is found, and their amounts are estimated. Both lithiation and change of morphology to nanourchin destroy the spin-gap behavior, which indicate changes in charge distribution. No ferromagnetic response is observed in lithiated VONTs. Magnetic properties of vanadium oxide nanorods with δ-V4O10 structure are also characterized.