Recently, biomass derived carbons received great attention as a renewable source of carbon with different morphologies[1,2]. Among various carbon material preparation methods such as carbonization of polymer precursors, arc discharge, chemical vapor deposition and chemical synthesis, carbonization / hydrothermal carbonization of biomass to yield carbon looks promising due to abundant availability of precursor. A variety of biomass derived carbon materials are well studied as an electrode material for energy storage devices like lithium ion battery, supercapacitors, lithium-sulphur battery and sodium ion batteries.  Rice husk, tea leaves, coconut fibers, coffee shell, neem seed etc., derived activated carbons shown promising anode material for lithium ion storage. Typically, these biomass derived carbons found to be hard carbons in nature but their morphology varied with precursor material. Neem (Azadirachta indica) derived carbon was used as electrode material for supercapacitor application and shows excellent performance. However, there is no study available on lithium ion intercalation in need derived carbon to the best of our knowledge. In present work, we have investigated the electrochemical performance of neem leaves derived carbon as anode material for lithium ion battery application.
Neem leaves collected from fields were washed with DI water minimum for three times and dried in an oven at 65 °C for overnight. Thus collected samples were crushed in a mortar to obtain fine powder prior to pyrolysis in alumina tube furnace at 900 °C to yield carbon powder. As prepared carbon powder was then used as an active material (anode) in slurry coated electrode preparation.
Results and discussions:
The structure of as-prepared neem leaves derived carbon powder was investigated by X-ray diffraction (XRD) and Raman spectroscopy. From Raman and XRD analysis neem derived carbon was found to be hard carbon and with the short arrangement of crystallites and in-planar width. Electrochemical performance of neem derived carbon was investigated with cyclic voltammetry and galvanostatic charge discharge experiments. Figure 1 (c) shows the typical hard carbon cyclic voltammetry plot where the broad peak in the first cycle corresponds to solid electrolyte formation close to 0.5 V and a peak corresponding to intercalation near 0 V. Figure 1 (d) shows the cyclic performance of charge-discharge experiments at 37.2 mAh/g current density. Even after 100 cycles of continuous charge/discharge, there is a very minor capacity fade that confirms the excellent cyclic stability. Further, the columbic efficiency after initial few cycles is maintained to be constant above 95%. The performance is significantly better than any other biomass derived carbon materials ever reported in literature without adding further processing cost in physical or chemical activation. Further detailed electrochemical performance comparison with biomass derived carbons and its correlation with structural characterization of the neem derived carbon will be presented during the conference.
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