Browsing by Author "Kato, Keiko"

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    A common tattoo chemical for energy storage: henna plant-derived naphthoquinone dimer as a green and sustainable cathode material for Li-ion batteries
    (The Royal Society of Chemistry, 2018) Miroshnikov, Mikhail; Kato, Keiko; Babu, Ganguli; Divya, Kizhmuri P.; Arava, Leela Mohana Reddy; Ajayan, Pulickel M.; John, George
    The burgeoning energy demands of an increasingly eco-conscious population have spurred the need for sustainable energy storage devices, and have called into question the viability of the popular lithium ion battery. A series of natural polyaromatic compounds have previously displayed the capability to bind lithium via polar oxygen-containing functional groups that act as redox centers in potential electrodes. Lawsone, a widely renowned dye molecule extracted from the henna leaf, can be dimerized to bislawsone to yield up to six carbonyl/hydroxyl groups for potential lithium coordination. The facile one-step dimerization and subsequent chemical lithiation of bislawsone minimizes synthetic steps and toxic reagents compared to existing systems. We therefore report lithiated bislawsone as a candidate to advance non-toxic and recyclable green battery materials. Bislawsone based electrodes displayed a specific capacity of up to 130 mA h g−1 at 20 mA g−1 currents, and voltage plateaus at 2.1–2.5 V, which are comparable to modern Li-ion battery cathodes.
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    Energy storage devices including at least one electrode comprising a metal diboride, and related methods
    (2020-09-15) Zhou, Zhou; Kato, Keiko; Babu, Ganguli; Khabashesku, Valery N.; Ajayan, Pulickel M.; Rice University; Baker Hughes, a GE company, LLC; United States Patent and Trademark Office
    An energy storage device including a first electrode comprising lithium, a second electrode comprising a metal diboride, an electrolyte disposed between the first electrode and the second electrode and providing a conductive pathway for lithium ions to move to and from the first electrode and the second electrode, and a separator within the electrolyte and between the first electrode and the second electrode. A method of forming an energy storage device including forming a first electrode to include lithium, forming a second electrode to include a metal diboride, disposing an electrolyte between the first electrode and the second electrode, the electrolyte providing a conductive pathway for lithium ions to move to and from the first electrode and the second electrode, and disposing a separator within the electrolyte and between the first electrode and the second electrode.
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    Material engineering for Li-ion capacitors and Li-ion batteries
    (2019-12-05) Kato, Keiko; Ajayan, Pulickel M; Tang, Ming
    Electrochemical energy storage devices are fundamental driving force behind personal and industrial electronics. Li-ion batteries became the most prevalent rechargeable energy storage technology in market because of a high energy density. However, a power density (especially charging) of Li-ion batteries is not satisfactory for certain applications. In this regard, supercapacitors serve as a complementary role. To combine the advantages of Li-ion batteries and supercapacitors and bridge the technological gap, Li-ion capacitors (LICs) are invented. A typical Li-ion capacitor consists of a battery-type anode and supercapacitor-type cathode in Li-ion containing carbonate-based electrolytes. The major challenge of LICs arises from such disparity in charge-storage mechanism and kinetic. The present work addresses the issue by engineering electrode and electrolyte materials. 1) Two-dimensional material (vanadium disulfide anode and nitrogen-doped reduced graphene oxide cathode) are developed to combat the low power density of battery-type electrodes and the low energy density of supercapacitor-type electrodes. 2) We demonstrated that the energy and power densities achievable by LICs are largely influenced (and perhaps determined) by the anion adsorption at the positive electrodes, and by the ion transport within the electrolytes. Another challenge of the current Li-ion battery technology is an environmental and sustainability aspects because of a use of toxic and scarce transitional metals. Electroactive organic molecule-based cathodes which can reversibly store Li-ions are environmentally benign alternatives. Here, we assessed electrochemical performance of a plant-based organic molecule (lawsone) and showed that its oligomer structure stabilizes the molecules, which led to an improvement in a capacity retention over repeated cyclings. Next, we exploited the light-harvesting and Li-storing capabilities of the organic molecules to demonstrate light charging capability of the molecule. This work sheds light on the unique capability of organic cathode materials and paves the way for the future development of environmentally friendly and light rechargeable Li-ion batteries.