Editors: | F. Kongoli, H. Dodds, M. Mauntz, T. Turna, K. Aifantis, A. Fox, V. Kumar |
Publisher: | Flogen Star OUTREACH |
Publication Year: | 2019 |
Pages: | 112 pages |
ISBN: | 978-1-989820-11-7 |
ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Silicon (Si) has been widely considered as potential high capacity anode material in Li-ion batteries due to its desirable properties: (i) high theoretical specific capacity (1672 mA h g-1), (ii) nontoxicity and (iii) low cost and natural abundance [1]. Despite its favourable comparison to commercial graphite anodes (theoretical capacity of 372 mA h g-1), the implementation of bulk Si anode has been hindered by the large volume change during the charging and discharging cycle (~ 300%). Such structural instability results in loss of contact with the other electrode constituents and self-destruction [2]. Another adverse feature is the limited Li+ ion diffusivity and electronic conductivity of bulk Si at room temperature.
A scalable method of producing carbon (ultrafine silicon composite electrode) was developed using the Virtual Cathode Deposition technique [3]. As-deposited coatings contained silicon nano-crystallites encapsulated in a novel polymorph of mesoporous disordered carbon matrix. The architecture of the electrode offers close-order integration of both materials ensuring fast Li+ ion diffusivity and mixed-(ionic/electronic) conductivity as well as alleviating Si volume change during cycling. The composite carbon polymorph-silicon anode tested versus Li displayed a first cycle specific capacity of more than 2000 mAh g-1 retaining in the following cycles ~1200 mAh g-1 at a 0.1C rate. The good cyclability (over 80 cycles) demonstrated the effectiveness of such Si - carbon encapsulation, addressing the instability issues of Si-based anodes.