A comparative study for picosecond and nanosecond laser structuring was performed in order to identify structure geometries and dimensions that efficiently reduce the significant volume changes during electrochemical cycling of SnO2, a promising anode material. Line structures with widths of 20 μm could significantly improve cycling stability of 3 μm thick magnetron sputtered SnO2 thin films. A reduction of structure size led to further improvement of capacity retention. Free-standing conical micro-structures exhibited the best cycling behavior.

We report 3D finite element simulations analyzing scaling effects on the performance of single Silicon Germanium thermoelectric generator with 170 μm tall metal contacts. Temperature dependent material parameters are included to accurately model device performance. Power density was extracted for a range of widths, heights, and operating temperature. Depending upon cross sectional area of the SiGe leg and operating temperature, height can be optimized for maximum power density.

The ability to monitor the status of a battery during charge and discharge is important for predicting its performance and life. This is typically done by measuring the voltage and resistance across the terminals, or by external characterization methods such as X-ray diffraction and Raman spectroscopy. Thermodynamics measurements based on entropy and enthalpy provide another mean to “look inside” a battery, giving us more information to determine the state of health of the battery. In particular, entropy undergoes drastic changes at boundaries of phase transitions taking place in each electrode material at defined states of charge (lithium stoichiometry). Recent work on thermodynamics study on lithium ion battery materials is summarized in this paper.

Hydrogenation properties of some amorphous Zr-Ni-Ti-V based alloys were investigated. Pressure-composition(P-C) isotherms and hydrogen storage capacities at room temperatures were measured and effects of elemental substitution of the components with Pd or Mn were studied. The alloy electrodes were prepared by using amorphous (Zr-Ni-Ti-V)-(Pd,Mn) alloys prepared by the melt spinning method. The amorphous alloys in the electrode kept their amorphous structures during cycles of charge and discharge. The electrochemical hydrogen storage capacities were strongly affected by the substitution amounts of Pd or Mn. Even a small amount of substitution, changed the equilibrium dissociation pressures of the alloy. In the present study, the rechargeable capacity was optimized up to H/M=0.5 for the alloy electrode with the composition of (Zr45Ni30Ti25)-3at%Pd. The slope in the P-C isotherm suggested that the maximum H/M of the alloy would exceed 1.0 at higher hydrogen pressure than 1.0 MPa, however, the wide distribution of hydrogen site energy in the amorphous hydride resulted in extremely large slope in P-C isotherms, and consequently restricted the rechargeable capacities of the electrodes.

This paper reports on electrochemical hydrogen oxidation at atomically smooth single crystal surfaces. These surfaces are considered as planar models for (bi)metallic nanoparticles that are commonly used as catalytically active electrode materials in low-temperature fuel cells. These samples are prepared in ultrahigh vacuum but are characterized under conditions of enhanced mass transport in hydrogen saturated electrolyte. The two examples shown in this paper are Ru(0001) with or without an atomically thin layer of Pt. The Pt thin layer turns out to be more active than pure Ru(0001) by three orders of magnitude and also more active than bulk Pt electrodes. We show that those findings agree very well with predictions based on density functional theory in combination with a simple kinetic model.

The effect of two substituent groups, ortho-methoxy (-OCH3) and methyl (-CH3) in aniline, have been studied for supercapacitor applications. The polyaniline (PANI), poly (o-anisidine) (POA) and poly (o-toluidine) (POT) have been synthesized by oxidative polymerization method, and characterized by Cyclic Voltammetry (CV), UV–visible spectroscopy, Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques. The specific capacitance, charging/discharging and electrochemical impedance characteristics of the supercapacitor fabricated using PANI, POA, as well as POT electrodes are evaluated in 2M H2SO4 electrolytic media. The highest specific capacitance of 400 F/g is calculated for PANI, whereas, POA and POT have exhibited 360 F/g and 325 F/g capacitance in supercapacitor studies.

The economical production of flexible, chemically-functionalized carbon nanotube (CNT) electrodes is appealing for the manufacture of electronic textiles with integrated charge storage capability. In this paper, a commercial CNT sheet is treated with 0.02 M potassium permanganate at room temperature to accomplish in-situ deposition of manganese dioxide. The morphology, elemental oxidation states, and crystallinity of the modified CNT sheet are studied using SEM, EDX, XPS, and XRD. Manganese loading is varied from 4 to 20 weight-percent by tuning solution treatment time, and metal oxide hydration state is influenced by thermal annealing at 200 °C. Electrochemical measurements reveal that charge is stored not only via CNT-induced electrical double-layer capacitance, but also through metal oxide-mediated Faradic reactions. The MnO2-decorated CNT sheet exhibits a specific capacitance of 89.6 F/g at 1 A/g, a tenfold enhancement compared to pristine CNT sheet. Overall, this simplified processing approach holds promise for cost-effective incorporation of electrochemical capacitors into functional fabrics for energy-generation applications.

Solid-electrolyte interphase (SEI) regions play a critical role in stabilizing lithium batteries, but little is known about the detailed mechanism of growth and formation. We have developed a novel method for in situ study of the interfacial regions of SEI layers, using an interface-selective nonlinear vibrational spectroscopy method termed femtosecond broadband multiplex vibrational sum-frequency generation spectroscopy (SFG) and a lithium battery electrochemical cell with optical access. SFG has high sensitivity and high selectivity needed to study vibrational transitions of molecular species during the SEI growth. SFG is most sensitive to interfacial regions, so with SFG we ignore the bulk electrolyte and focus on interface regions just a few molecules thick. During SEI growth there are two such interfaces, the electrode-SEI interface and the electrolyte SEI interface. We will present results obtained using a lithium battery and model materials relevant to Li batteries, where during successive cycles of charge and discharge we selectively probe the structural evolution of these two interfaces on Au, Cu and carbon.

Carbon-coated lithium iron phosphate (C-LiFePO4) particles have been synthesized by a solid-state reaction process. Particles surface morphology, olivine-type phase structures and the carbon shell-core structures are investigated in details by transmission electron microscopy (TEM, HRTEM) imaging and electron diffraction (SAED) patterns. Homogenous features of carbon coating of the LiFePO4 particles surface are obviously revealed. HR-TEM imaging and X-ray photoelectron spectroscopy (XPS) confirmed an amorphous sp2 type conducting coating layer on the surface of LiFePO4 particles. Particles shape and size showed the clear single-crystal nature of the phospho-olivine type structures with the rough spherical features of 50-250 nm size range. The characteristics of sp2 type carbon-coating on the LiFePO4 particles surfaces allows improving the electrical conductivity and reducing the diffusion path of the lithium ions, as directly evidenced from electrochemical tests of charge-discharge cycling.

Graphite electrode surface degradation mechanisms and formation of solid electrolyte layers (SEI) at the interface with the electrolyte were studied as a function of the applied voltage and voltage scan rates using in situ optical microscopy. Voltammetry tests were initiated from a peak voltage of 3.00 V during which the voltage was decreased to a constant base potential (0.02 V) using different scan rates of 0.05-5.00 mV/s. Cross-sectional FIB microscopy indicated that graphite surface and subsurface damage -- in the form of loss of material from graphite -- was reduced when dense and continuous deposits of SEI formed at low scan rates (e.g. 0.05 mV/s).Whereas, non-uniform and discontinuous SEI formed at high scan rates (∼ 5.00 mV/s) was unable to alleviate graphite surface damage.

Wireless power transfer is experimentally demonstrated by transmission between an AC power transmitter and receiver, both realised using thin film technology. The transmitter and receiver thin film coils are chosen to be identical in order to promote resonant coupling. Planar spiral coils are used because of the ease of fabrication and to reduce the metal layer thickness. The energy transfer efficiency as a function of transfer distance is analysed along with a comparison between the theoretical and the experimental results.