Browsing by Author "Gowda, Sanketh R."

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    Conformal coating on nanostructured electrode materials for three-dimensional applications
    (2016-04-12) Ajayan, Pulickel M.; Ou, Fung Suong; Shajiumon, Manikoth M.; Gowda, Sanketh R.; Reddy, Arava L. M.; Rice University; United States Patent and Trademark Office
    A fabrication process for conformal coating of a thin polymer electrolyte layer on nanostructured electrode materials for three-dimensional micro/nanobattery applications, compositions thereof, and devices incorporating such compositions. In embodiments, conformal coatings (such as uniform thickness of around 20-30 nanometer) of polymer Polymethylmethacralate (PMMA) electrolyte layers around individual Ni—Sn nanowires were used as anodes for Li ion battery. This configuration showed high discharge capacity and excellent capacity retention even at high rates over extended cycling, allowing for scalable increase in areal capacity with electrode thickness. Such conformal nanoscale anode-electrolyte architectures were shown to be efficient Li-ion battery system.
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    Lithium storage mechanisms in purpurin based organic lithium ion battery electrodes
    (Nature Publishing Group, 2012) Reddy, Arava Leela Mohana; Nagarajan, Subbiah; Chumyim, Porramate; Gowda, Sanketh R.; Pradhan, Padmanava; Jadhav, Swapnil R.; Dubey, Madan; John, George; Ajayan, Pulickel M.
    Current lithium batteries operate on inorganic insertion compounds to power a diverse range of applications, but recently there is a surging demand to develop environmentally friendly green electrode materials. To develop sustainable and eco-friendly lithium ion batteries, we report reversible lithium ion storage properties of a naturally occurring and abundant organic compound purpurin, which is non-toxic and derived from the plant madder. The carbonyl/hydroxyl groups present in purpurin molecules act as redox centers and reacts electrochemically with Li-ions during the charge/discharge process. The mechanism of lithiation of purpurin is fully elucidated using NMR, UV and FTIR spectral studies. The formation of the most favored six membered binding core of lithium ion with carbonyl groups of purpurin and hydroxyl groups at C-1 and C-4 positions respectively facilitated lithiation process, whereas hydroxyl group at C-2 position remains unaltered.
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    Three dimensional nanostructured designs for lithium ion batteries
    (2012) Gowda, Sanketh R.; Ajayan, Pulickel M.
    The reversible electrochemistry and the superior gravimetric and volumetric energy storage capacities of lithium ion batteries (LIBs) have propelled them as the dominant power source for a range of portable electronic devices. Thin film LIBs are a class of LIBs that have been extensively used for powering Microelectromechanical systems devices, Radio-frequency Identification tags, biomedical sensors and several other low power electronic systems. Thin film electrodes and electrolytes are characteristic of short lithium ion diffusion paths and hence show fast charge/discharge rates. But the thin film battery technology has the major drawback of possessing low energy per footprint area. The three dimensional design for thin film LIBs has been proposed to improve electrode mass loading per footprint area thereby improving the energy delivered by the device. Hence there is interest in assembling the entire battery (current collectors, anode, electrolyte, and cathode) in a three dimensional (3D) nanostructured architecture. This thesis deals with the development and assembly of nanostructured three dimensional designs for Li ion battery components. Several template-based techniques have been used to fabricate nanostructured materials which serve as building blocks for the 3D energy storage devices. Firstly we have addressed the challenging task of fabricating conformal nanostructured polymer electrolytes around nanowire electrode material. The polymer coatings helped in controlling the secondary electrolyte interphase formation and hence in the improvement of cycling characteristics of the nanowire electrode material. We have also fabricated 3D current collectors with both ordered and disordered pore structure. Electrodes coated on 3D nanostructured current collectors showed improved rate capability and energy per footprint area. Finally, we have used a bottom up approach to assemble all essential components (anode, electrolyte, and cathode) of an electrochemical energy storage device onto a single nanowire, and have tested a parallel array of such nanowire devices for its electrochemical performance, hence demonstrating the ultimate miniaturization possible for energy storage devices.