Journal
JOURNAL OF MATERIALS CHEMISTRY A
Volume 4, Issue 7, Pages 2651-2656Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c5ta09973k
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Funding
- Korea Institute of Science and Technology (KIST)
- National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea [NRF-2012M1A2A2671792]
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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 x 10(-6) cm(2) s(-1).
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