Martin Halim

Phenyl-rich silicone oil as a precursor for SiOC anode materials for long-cycle and high-rate lithium ion batteries

Silicon oxycarbide (SiOC) is gaining increasing attention as a promising anode material for lithium ion batteries due to its higher reversible capacity compared to incumbent graphite. The kinetic processes at a SiOC anode result in rapid capacity fading even at a relatively low current density, thereby hindering its commercialization. Herein, a distinctive, phenyl-rich silicone oil is used as a precursor for producing SiOC anode materials via simple pyrolysis. We find that only silicone oil with phenyl-rich rings can be converted into SiOC materials. The phenyl group was crucial for carbon incorporation to allow Si–O–C bonding and the formation of a free-carbon phase. The resulting SiOC anode exhibited stable cyclability up to 250 cycles, with a discharge capacity of 800 mA h g−1 at a current density of 200 mA g−1. The remarkable cycle performance of SiOC was correlated with its low dimensional expansion (7%) during lithiation, which maintains its structure over cycling. Rate capability tests showed a highly stable performance with a maximum discharge capacity of 852 mA h g−1 at a current density of 100 mA g−1. When the discharge current density was increased 64-fold, the reversible capacity of the SiOC anode was 90% of its maximum capacity, 772 mA h g−1. The excellent electrochemical performance of SiOC could be attributed to the rapid mobility of Li+ within the SiOC matrix, as indicated by a Li+ diffusion coefficient of 5.1 × 10−6 cm2 s−1.

Preparation of Orange Peel Based Activated Carbons as Cathodes in Lithium Ion Capacitors

In this work, activated carbon was prepared from Indonesian local orange peel using ZnCl2 activation method at various chemical ratios. The structural and morphological characteristics of orange peel based activated carbons were investigated using scanning electron microscope (SEM), Brunaeuer-Emmett-Teller surface analyzer. The highest surface area was estimated as 1200 m2g-1, obtained by the mass ratio of 1:2 (biomass : ZnCl2). The obtained carbon samples were then tested as cathodes in Lithium Ion Capacitors. Electrochemical measurement was examined by half cell configuration, using 1 M LiPF6 in EC/EMC/DMC solution (1:1:1 v/v) as electrolyte and Li metal as reference electrode. From cyclic voltammetry (CV) test, it was shown that orange peel based activated carbon demonstrated a stable electrochemical characteristics, with specific capacitance of 56 Fg-1 measured at scan rate of 1 mVs-1 under cut-off voltages between 2.5 and 4 V.

The effect of activated carbon support surface modification on characteristics of carbon nanospheres prepared by deposition precipitation of Fe-catalyst

In this study the effect of activated carbon support modification to synthesis of CNSs was observed. Modification of activated carbon was done by using nitric acid. The effect of modification was analyzed from its FTIR spectra. The Fe catalysts were deposited on to the support by using urea deposition precipitation method at various initial catalysts concentration. CNSs was synthesized by utilizing cooking palm oil as renewable carbon source, and pyrolized at 700°C for 1 hour under nitrogen atmosphere. The products obtained then analyzed using SEM-EDS, TEM, XRD, and Raman spectroscopy. The modification of activated carbon support had increased the oxygen functional group. This increase resulted on increase of metal catalysts deposited on activated carbon surface. Peak of C (100) was observed, while ID/IG of samples were obtained around 0.9, which is commonly obtained for CNSs. High catalysts loading on modified activated carbon support caused decomposition of CNSs and formation carbon onion.

Structural and preliminary electrochemical characteristics of palm oil based carbon nanospheres as anode materials in lithium ion batteries

Copyright