Journal
CHEMICAL ENGINEERING JOURNAL
Volume 404, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2020.126520
Keywords
Silicon oxycarbides; Sodium-ion batteries; Sweep gas; C-rich precursor
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Funding
- National Research Foundation of Korea (NRF) - Ministry of Science and ICT, Republic of Korea [2020R1A2C2003947]
- National Research Foundation of Korea [2020R1A2C2003947] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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By adjusting the synthesis conditions and the C content of SiOC precursors, the SiOC enriched with C- and O-rich SiOxCy phases can deliver high reversible capacity and maintain stability after long-term cycling.
Silicon oxycarbides (SiOCs) are considered promising sodium-ion battery anode materials. However, the total and low-voltage plateau capacities of SiOCs are low (below 200 and 95 mAh g(-1), respectively), which hinders the manufacturing of high-density electrodes. Herein a new strategy for improving the electrochemical performance of SiOCs was proposed by considering the Na+ ion storage mechanisms in SiOCs. High-capacity SiOCs were synthesized by increasing the amount of C- and O-rich SiOxCy phases and reducing the amount of inactive SiO2, SiC, and C-free phases. The compositions of SiOCs were controlled by adjusting the synthesis conditions (e.g., sweep gas and pyrolysis time) and C content of the SiOC precursors. The use of N-2 sweep gas instead of H-2/ Ar suppressed the formation of SiC and Cfree. In addition, the amount of inactive SiO2 phase in SiOCs was further suppressed using a C-rich precursor. Consequently, the synthesized SiOC, which was enriched with C- and O-rich SiOxCy phases, delivered a high reversible capacity of 234 mAh g(-1) at a current density of 25 mA g(-1). In constant-current/constant voltage mode, the reversible capacity was further increased to 299 mAh g(-1), which was close to the theoretical maximum capacity of 315 mAh g(-1). After 140 cycles, the reversible capacity was stabilized to 160 mAh g(-1). The initial capacity loss during long-term cycling, which was mostly caused by the progressive decrease in the low-voltage plateau capacities, was attributed to the increase in cell polarization.
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