Browsing by Author "Gullapalli, Hemtej"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    2D material integrated macroporous electrodes for Li-ion batteries
    (Royal Society of Chemistry, 2017) Gullapalli, Hemtej; Kalaga, Kaushik; Vinod, Soumya; Rodrigues, Marco-Tulio F.; George, Antony; Ajayan, Pulickel M.
    Three-dimensionally structured architectures are known to improve the performance of electrodes used in Li ion battery systems. In addition, integration of select 2D materials into 3D structures, for enhancing both electrical conductivity and electrochemical activity, will prove advantageous. Here a scalable one-step chemical vapor deposition technique is demonstrated for the controlled etching and simultaneous graphene growth on stainless steel substrates resulting in a 3D micro-mesh architecture that is ideal for high rate/high capacity electrodes; the graphene coated 3D stainless steel current collector is used with an MoS2 electrode material for demonstrating high stability and rate capacity in Li-ion batteries.
  • Thumbnail Image
    Item
    Composition for energy generator- storage- and strain sensor and methods of use thereof
    (2012-11-13) Ajayan, Pulickel M.; Kumar, Ashavani; Botello-Mendez, Andres Rafael; Gullapalli, Hemtej; Terrones Maldonado, Mauricio; Rice University; United States Patent and Trademark Office
    Compositions and devices for harvesting electrical energy from mechanical and thermal energy, storing such produced energy, and sensing strain based on low cost materials and processes. In embodiments, the compositions are flexible and include a flexible polymer embedded and coated with a nanostructured piezoelectric material.
  • Thumbnail Image
    Item
    Engineered Nanomaterials for Energy Harvesting and Storage Applications
    (2014-11-03) Gullapalli, Hemtej; Ajayan, Pulickel M; Vajtai, Robert; Biswal, Sibani L; Arava, Leela Mohana Reddy
    Energy harvesting and storage are independent mechanisms, each having their own significance in the energy cycle. Energy is generally harvested from temperature variations, mechanical vibrations and other phenomena which are inherently sporadic in nature, harvested energy stands a better chance of efficient utilization if it can be stored and used later, depending on the demand. In essence a comprehensive device that can harness power from surrounding environment and provide a steady and reliable source of energy would be ideal. Towards realizing such a system, for the harvesting component, a piezoelectric nano-composite material consisting of ZnO nanostructures embedded into the matrix of ‘Paper’ has been developed. Providing a flexible backbone to a brittle material makes it a robust architecture. Energy harvesting by scavenging both mechanical and thermal fluctuations using this flexible nano-composite is discussed in this thesis. On the energy storage front, Graphene based materials developed with a focus towards realizing ultra-thin lithium ion batteries and supercapacitors are introduced. Efforts for enhancing the energy storage performance of such graphitic carbon are detailed. Increasing the rate capability by direct CVD synthesis of graphene on current collectors, enhancing its electrochemical capacity through doping and engineering 3D metallic structures to increase the areal energy density have been studied.
  • Thumbnail Image
    Item
    Recycling Li-ion batteries using green chemicals and processes
    (2023-02-28) Tran, Mai K.; Rodrigues, Marco-tulio F.; Babu, Ganguli; Gullapalli, Hemtej; Ajayan, Pulickel M.; Rice University; William Marsh Rice University; United States Patent and Trademark Office
    A process for extracting, recovering and recycling metals and materials from spent lithium ion batteries (LIB) that comprises the contacting battery waste products with a deep eutectic solvent, and leaching the metal from the battery waste product and extracting the metal into the deep eutectic solvent with heat and agitation. After the leaching and extracting, the process further includes recovering the dissolved metals ions from the deep eutectic solvent solution, followed by a step of regeneration of cathode materials.
  • Thumbnail Image
    Item
    Supercapacitor Operating At 200 Degrees Celsius
    (Nature Publishing Group, 2013) Borges, Raquel S.; Reddy, Arava Leela Mohana; Rodrigues, Marco-Tulio F.; Gullapalli, Hemtej; Balakrishnan, Kaushik; Silva, Glaura G.; Ajayan, Pulickel M.
    The operating temperatures of current electrochemical energy storage devices are limited due to electrolyte degradation and separator instability at higher temperatures. Here we demonstrate that a tailored mixture of materials can facilitate operation of supercapacitors at record temperatures, as high as 2006C. Composite electrolyte/separator structures made from naturally occurring clay and room temperature ionic liquids, with graphitic carbon electrodes, show stable supercapacitor performance at 2006C with good cyclic stability. Free standing films of such high temperature composite electrolyte systems can become versatile functional membranes in several high temperature energy conversion and storage applications.