Browsing by Author "John, George"

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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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    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.