Transition-metal functionalized-carbon nanotubes (CNTs) represent an important genre of hydrogen storage systems that exhibit superior storage capacity and improved storage kinetics when compared with the pristine CNTs. Here, we compare the reversible gravimetric hydrogen storage capacity of platinum-functionalized CNTs with that of pristine tubes, both measured at 300 K and an equilibrium hydrogen pressure of 1.67 MPa. The maximum reversible hydrogen storage capacity exhibited by the nano-composite material is found to be 3.2 ± 0.1 wt%, which is a nearly 50 % enhancement when compared with that of the pristine tubes. The enhanced hydrogen storage capacity of functionalized CNTs is attributed to the spill-over phenomena as suggested by the estimated storage capacity of Pt phase. The hydrogen storage in Pt nanoparticles modeled using the atomic magic number calculation and Pt hydride stoichiometry of PtH4 also suggests that nearly 15 closed shells of Pt atoms reversibly adsorb and spill hydrogen on to CNT binding sites.

This work presents recent advances in the development and the integration of a solid state thin film battery, to work as a high voltage energy source for RF-MEMS powering. Micro-electro-mechanical systems require similarly miniaturized power sources. Up to day, microbatteries are realized with mechanical masks, this method doesn't allow dimensions below several decades of mm2 of active area, and besides the whole process flow is done under controlled atmosphere so as to ensure materials chemical stability (mainly lithiated materials). Within this context, Microelectronics micro-fabrication procedures (photolithography, Reactive Ion Etching…) are used to reach both miniaturisation (100×100 μm2 targeted unit cell active area) and microelectronic IC technological compatibility. The whole process is realized in clean room environment. The thin film battery is composed of three active layers. First the positive electrode layer of crystalline vanadium pentoxide c-V2O5, the next level presents then the solid state electrolyte, a glassy ionic conducting material commonly known as “LiPON”. Finally, a negative electrode top level is realized by the evaporation of metallic lithium. The total stack thickness is of about 10 μm. A final wafer level packaging step is then realized to avoid reactivity with air and moisture. Specific attention will be put on the microfabrication processes developed for the positive electrode and the electrolyte (etching chemistry, resist stripping…). Several electrochemical characterizations (spectroscopic electrochemical impedance, charge-discharge cycling) were performed before and after micro-fabrication process steps so as to evaluate any possible effect on the electrochemical behaviour of the different studied layers.

We have studied the temperature dependence of thermoelectric properties of amorphous InN thin films prepared by reactive radio-frequency sputtering. We fabricated 60-pair and 120-pair InN-chromel films, which were deposited on polyimide films. For the 120-pair device, the maximum open output voltage and the maximum output power were 210 mV and 65 nW, respectively, at temperature difference of 168 K.

We report a monolithic series connected semi-transparent (transmission > 40%) amorphous silicon (a-Si:H) solar cell panel (substrate area 30cm × 40cm), which has an i-layer thickness <2000Å and an active area efficiency, η ∼ 3%. We also report on all laser scribed, series connected mini-modules with an aperture area η > 3% constructed on inexpensive plastic substrates.

A micro (∼1 cm3) dynamic heat engine, capable of producing electrical power from lowgrade heat sources, utilizes a micro-machined diaphragm with a piezoelectric element as a The electromechanical coupling of a piezoelectric diaphragm under large initial stresses and/or large deflections – in the membrane limit – is described here. A simple model is derived for electromechanical transduction of a pressurized piezoelectric membrane and an experiment is described to measure it. Electromechanical coupling initially increases as the square of the center-point deflection as the residual stress is overcome. In the limit of large pressures, the electromechanical coupling approaches a limit that is predicted by the model.

Optimized LiFePO4 positive electrode for Li-ion batteries was obtained after severe control of the fundamental properties of material. The nanoscopic structure and magnetic properties of a series of carbon-coated LiFePO4 particles prepared under various conditions were analyzed with XRD, FTIR, Raman and SQUID magnetometry. We evaluate intrinsic and extrinsic properties. The existence of low content of nano-sized ferromagnetic particles was evidenced by magnetic measurements in samples grown from iron(II) oxalate; such ferromagnetic clusters do not exist in the optimised samples grown from FePO4(H2O)2. Other impurity phases such as Fe2P, Li3Fe2(PO4)3, FeP2O7 were also detected for particular conditions of preparation. The impact of the carbon coating on the electrochemical properties is reported. Li-ion cells show excellent cyclability after 200 cycles at 60 °C without iron dissolution.

Nanostructured carbon materials with a regular array and narrow size distribution of mesopores have been synthesized at Oak Ridge National Laboratory via the self-assembly of block copolymers as soft templates. One promising application for these materials is as electrodes for electrochemical double-layer capacitors. To evaluate the performance, electrodes were prepared by coating the precursor onto fibrous carbon paper, followed by curing and pyrolysis at 850°C. The resulting mesoporous carbon has a surface area of 310 m2/g and an average pore size of 8.5 nm. Results from cyclic voltammetry and impedance spectroscopy experiments using a sulfuric acid electrolyte showed high specific capacitance values of up to 300 F/g. For comparison, a commercially available aerogel carbon coated paper was also examined.

The extremely high surface areas required for supercapacitors has limited the use of metal based electrodes, despite the other advantages such electrodes might have. Self-assembling surfactants and block co-polymers can be used as templates to produce nanostructured thin films that readily give 60-140 fold increases in surface area on both planar and three-dimensional substrates. However, even when relatively high surface area porous metal substrates such as nickel foam are used as a starting point, the resultant material still has surface area density well short of that available in other types of materials. Micro-emulsions offer a method of generating microstructure that bridges the gap between the 100 micron scale structures of foamed metals and the 10-50 nm scale structure of self-assembling block co-polymers. Electrodeposition of nickel and cobalt from micro-emulsions of Tween surfactants gives rise to structure on the 0.1-10 micron length scale. The scale of the microstructure is strongly influenced by the metal ion concentration and the potential at which the electrodeposition. The nature of the metal ion also strongly effects the ease with which the microstructure can be generated and the distribution of the microstructured film on foamed nickel electrodes. For microstructured nickel films ten fold surface area increases can be achieved. The microstructured films are expected to be compatible with a number of the nanostructuring methods to yield cumulative surface area increases of 1000-2000 fold.

Lithium titanium oxide (Li4Ti5O12) spinels are promising negative electrode materials for application in energy technology. In this work, we have synthesized Li4Ti5O12 and investigated its structure, electronic properties, and electrochemical features using several analytical spectroscopy and microscopy techniques. The equally spaced lattice fringes obtained using by the high-resolution transmission electron microscopy (HRTEM) along with electron diffraction reveal that the grown Li4Ti5O12 is well crystallized in the spinel structure without any indication of crystallographic defects such as dislocations or misfits. The electronic structure determination using high-resolution X-ray photoelectron spectroscopy (XPS) coupled with compositional studies using energy dispersive X-ray spectrometry (EDS) indicate excellent chemical quality of the Li4Ti5O12. Under the optimal synthetic condition, the sample delivers a discharge capacity of 161 mAh/g at C/12. The good cyclability of Li4Ti5O12 is attributed to the small expansion (δV≈1%) of the elementary unit-cell.

The effect of iodine doping on the electrochemical performance of activated carbons for non-aqueous symmetric and asymmetric hybrid supercapacitors was investigated. The incorporation of iodine via high energy mechanical milling techniques significantly modified the physical and electrochemical properties of activated carbon precursors. The increasing amount of iodine into carbons leads to a unique combination of lower surface area coupled with higher volumetric and gravimetric electrochemical capacitance. Iodine modification of the carbon resulted in a 100% increase in volumetric capacitance. This improvement was a result of improved non-faradaic capacitance and the development of faradaic capacity.

Polycarbonate (PC) membrane and PC based hydrogen active intermetallic compound Fe0.5Ti0.5 particles doped composite membrane have been prepared by solution cast method. The membranes have been characterized by H2 and CO2 permeability and selectivity measurements with increasing temperature. Higher gas permeation has been observed with increasing temperature. In case of doped composite membrane H2/CO2 gas pair selectivity first increases then decreases with temperature whereas in case of pure PC it decreases with temperature. The effect of doping increases the activation energies for permeation of H2 and CO2 in the doped membrane in comparison to pure PC. Doping was found to suppress plasticization effect in polycarbonate. The doped membrane was analyzed by optical micrograph and XRF study.

The Navy is currently investigating solid oxide fuel cells (SOFCs) for the propulsion of unmanned undersea vehicles (UUVs). SOFCs are being targeted because of their potential to carry out extended missions, which are not possible using current battery technology. In addition, they offer the advantages of being able to utilize energy-dense hydrocarbon fuels and are self-sustaining while supplying heat to reforming processes.

The SOFC system evaluated in this study consisted of a Ni-YSZ-based, 6-cell stack with anode supported cells close-coupled with a micro-channel steam reformer. Various reformate gas compositions, steam to carbon ratios and flow rates were tested to gather a range of data under the expected operating conditions of UUVs. The system was operated for more than 70 hours consuming approximately 0.5 to 0.7 ml/min of fuel and producing about 100 to 230 watts of power. The integrated stack and reformer displayed stable performance with a fuel utilization of 80% and an efficiency of 50% at maximum power output.

For the last several years, we have been developing and characterizing “mobile” micro- and nano-instruments for use on-site (e.g., in the field). Although such portable, battery-operated instruments are much smaller that their laboratory-scale counterparts, sometimes they provide comparable performance and they often offer improved capabilities. As such, they are expected to cause a paradigm shift in classical chemical analysis by allowing practioners to “bring the lab (or part of it) to the sample”. Two classes of examples will be used as the means with which to illustrate the power of micro- and nano-instruments. One class involves a “patient” as the sample and an ingestible capsule-size spectrometer used for cancer diagnosis of the gastro intestinal tack as (part of) “the lab”. The other involves the “environment” as the sample and a portable, battery-operated, miniaturized instrument that utilizes a PalmPilot™ with a wireless interface for data acquisition and signal processing as (part of) “the lab”. To discuss how to electrically power such miniaturized instruments, mobile energy issues will be addressed. Particular emphasis will be paid to current or anticipated future applications and to the paradigm shifts that may prove essential in powering the next generation of miniaturized instruments.

Nanoporous carbon materials with high surface area (1500 – 2000 m2/g) and narrow pore size distribution ranging from 1 – 3 nm were synthesized using polyfurfuryl alcohol/polyethylene glycol diacid and coal tar pitch/polymer blends. Electrical double layer capacitance of synthesized carbon was measured using cyclic voltammetry. There is a strong correlation between the surface area of the carbon and the specific capacitance. Carbon that had surface area smaller than 1000 m2/g had specific capacitance less than 50 F/g while the carbons having surface area from 1000 – 1500 m2/g showed specific capacitances in the order of 200 -250 F/g. It was shown that the mesoporosity and macroporosity in the parent carbon are critical for both activation and as well as the specific capacitance of the material. The use of these carbons in EDLCs was also demonstrated by fabricating a two-electrode ultracapacitor.

An unusual solubility domain for KIO4 in KOH solution is observed, which is consistent with a potential use of periodate as a cathode for alkaline batteries. With increasing alkalinity, the solubility of KIO4 first increases, then drops from 2.9 M to < 10−4 M with increase from 6 to 10 M KOH. The unusual rapid transition from high to low solubility with increasing KOH is attributed to the formation of insoluble periodate complex. Accompanying the favorable low solubility in concentrated KOH is a high degree of cathodic electroactivity in accord with two electron storage: IO4− ⊒ IO3−. Low cathode salt solubility minimizes interference with the anode. Zn anode alkaline batteries are studied with KIO4 and NaIO4 cathodes, have a potential of 1.4-1.5 V and discharge to over 95% of the intrinsic 2e− charge capacity. The cathode also exhibits good quasi reversibility (rechargeability) with an alkaline metal hydride anode.

We present the synthesis, structure, magnetic properties and electrode behaviour of LiMn2-yCoyO4 (0≤y≤0) spinel oxides prepared by the wet-chemitry via the carboxylic acid route. LiMn2-yCoyO4 samples crystallise with the cubic spinel-like structure (Fd3m S.G.). Optical spectra indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Co,Mn)-O bonds. Magnetic susceptibility and electron spin resonance measurements show the compositional dependence of the magnetic parameters, i.e. Curie temperature, Curie-Weiss constant and Néel temperature, when Mn is substituted by Co. The overall electrochemical capacity of LiMn2-yCoyO4 oxides have been reduced due to the 3d6 metal substitution, however, a more stable charge-discharge cycling performances have been observed when electrodes are charged up to 4.3 V as compared to the performance of the native oxide.

We report the electrochemical behavior of various layered oxides in Li cells. A series of LiNiyMnyCozO2 materials (with z=1-2y) was synthesized by “chimie douce” and investigated as positive electrodes in rechargeable lithium batteries. Electrochemical performances of LiNiyMnyCozO2 oxides are tested cell using non-aqueous 1M LiPF6 dissolved in EC-DEC. Charge discharge profiles are investigated as a function of the rate capability, the voltage window and the synthesis parameters of the cathode. A relation is found between the gravimetric capacity and the cation disorder of materials as indicated by magnetometry analysis.

We have prepared a primary film battery which shows improved shelf life and long-term stabiltiy. We tried to optimize a multi-layered packaging film by considering gas permeability, chemical affinity, and film thickness. We also optimized conducting layer thickness, cathode/anode thickness and their compositions taking N/P rato into account. We introduced a variety of hydrogel polymers, newly developed electrolyte solutions, and novel separators to enhance the ionic conductivity value of gel-type polymer electrolyte/separator system for peak power and high power property.

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.