The properties of rechargeable lithium-ion batteries are determined by the electrochemical and kinetic properties of their constituent materials as well as by their underlying microstructure. In this paper a method is developed that uses microscopic information and constitutive material properties to calculate the response of rechargeable batteries. The method is implemented in OOF, a public domain finite element code, so it can be applied to arbitrary two-dimensional microstructures with crystallographic anisotropy. This methodology can be used as a design tool for creating improved electrode microstructures. Several geometrical two-dimensional arrangements of particles of active material are explored to improve electrode utilization, power density, and reliability of the Li y C 6 ͉Li x Mn 2 O 4 battery system. The analysis suggests battery performance could be improved by controlling the transport paths to the back of the positive porous electrode, maximizing the surface area for intercalating lithium ions, and carefully controlling the spatial distribution and particle size of active material. Important advances in materials have paved the way to the introduction of new devices of ever-increasing functionality. 1 In many cases, however, the full potential of these devices remains unreachable due to limitations of the batteries that power them. These limitations find their origin on the constituents of the battery: the different ohmic contributions, the low diffusivity of the involved charged species, the underlying oxidation-reduction processes, etc. Thus, battery technology improvement is critical to the development of many electric-based applications.In this context, modeling the galvanostatic cycling of a rechargeable battery provides valuable insight into optimizing the performance of the device. Furthermore, an analysis that simultaneously resolves the microstructural details and includes the nonlinearities and history from successive charge-discharge cycles will be useful for improving cell design.The discharging and recharging process involves electronic and ionic flow and their spatial relationships to conductivity in multiple phases as well as interfacial contact potential. Stress distributions that arise due to concentration-induced strains and resistive heating affect battery performance and reliability. Fundamentally, these processes depend on the structure, size, and spatial distribution of electrolyte and active material phases. The incorporation of microstructure into battery models can provide design criteria for improved battery performance. In this paper, a two-dimensional microstructural model for battery discharge is presented and accounts for geometry, connectivity, electrochemical properties of the component phases as well as elastic stresses that develop during battery use. The model presented in this paper links previously developed models for the homogeneous behavior of individual battery components and interfaces. The models are coupled together in a way that geometrically and physica...
In this article, thin solid films are processed via pulsed-pressure metal organic chemical vapour deposition (PP-MOCVD) on FTO substrates over a range of processing times to produce a range of thicknesses and microstructures. The films are highly nanostructured anatase-rutile TiO2 composite films with unique single crystal dendrites. After annealing, carbon was removed, and materials showed improved water splitting activity; with IPCEs above 80 % in the UV, photocurrents of ~1.2 mA.cm-2 at 1.23 VRHE at 1 sun irradiance and an extension of photoactivity into the visible range. The annealed material exhibits minimal recombination losses and IPCEs amongst the highest reported in the literature; attributed to the formation of a high surface area nanostructured material and synergetic interactions between the anatase and rutile phases.
TiO2 photocatalyst is of interest for antimicrobial coatings on hospital touch-surfaces. Recent research has focused on visible spectrum enhancement of photocatalytic activity. Here, we report TiO2 with a high degree of nanostructure, deposited on stainless steel as a solid layer more than 10 μm thick by pulsed-pressure-MOCVD. The TiO2 coating exhibits a rarely-reported microstructure comprising anatase and rutile in a composite with amorphous carbon. Columnar anatase single crystals are segmented into 15–20 nm thick plates, resulting in a mille-feuilles nanostructure. Polycrystalline rutile columns exhibit dendrite generation resembling pine tree strobili. We propose that high growth rate and co-deposition of carbon contribute to formation of the unique nanostructures. High vapor flux produces step-edge instabilities in the TiO2, and solid carbon preferentially co-deposits on certain high energy facets. The equivalent effective surface area of the nanostructured coating is estimated to be 100 times higher than standard TiO2 coatings and powders. The coatings prepared on stainless steel showed greater than 3-log reduction in viable E coli after 4 hours visible light exposure. The pp-MOCVD approach could represent an up-scalable manufacturing route for supported catalysts of functional nanostructured materials without having to make nanoparticles.
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