Carbon-free conversion of SiO₂ to Si via ultra-rapid alloy formation: towards the sustainable fabrication of nanoporous Si for lithium ion batteries

Fan, Z., Liu, W.-R., Sun, L., Nishio, A., Szczesny, R., Lin, Y.-G., Okada, S. and Gregory, D. H. (2023) Carbon-free conversion of SiO₂ to Si via ultra-rapid alloy formation: towards the sustainable fabrication of nanoporous Si for lithium ion batteries. ACS Applied Materials and Interfaces, 15(30), pp. 36076-36085. (doi: 10.1021/acsami.3c02197) (PMID:37466273) (PMCID:PMC10401573)

Abstract

Silicon has the potential to improve lithium-ion battery (LIB) performance substantially by replacing graphite as an anode. The sustainability of such a transformation, however, depends on the source of silicon and the nature of the manufacturing process. Today’s silicon industry still overwhelmingly depends on the energy-intensive, high-temperature carbothermal reduction of silica─a process that adversely impacts the environment. Rather than use conventional thermoreduction alone to break Si–O bonds, we report the efficient conversion of SiO2 directly to Mg2Si by a microwave-induced Mg plasma within 2.5 min at merely 200 W under vacuum. The underlying mechanism is proposed, wherein electrons with enhanced kinetics function readily as the reductant while the “bombardment” from Mg cations and electrons promotes the fast nucleation of Mg2Si. The 3D nanoporous (NP) Si is then fabricated by a facile thermal dealloying step. The resulting hierarchical NP Si anodes deliver stable, extended cycling with excellent rate capability in Li-ion half-cells, with capacities several times greater than graphite. The microwave-induced metal plasma (MIMP) concept can be applied just as efficiently to the synthesis of Mg2Si from Si, and the chemistry should be extendable to the reduction of multiple metal(loid) oxides via their respective Mg alloys.

• Item Type: Articles
• Additional Information: DHG and ZF thank the University of Glasgow and the China Scholarship Council for the co-funding of a studentship for ZF, the Royal Society, RSC and EPSRC for associated funding un-der an International Exchange grant (IEC\R3\183040), an RSC COVID-19 Head of Department Grant (H20-118) and grant EP/N001982/1, respectively.
• Keywords: Microwave-Induced Metal Plasma (MIMP), SiO2 reduction, dealloying, nano Si, Lithium-Ion Batteries (LIBs).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Fan, Zhen and Szczesny, Dr Robert and Sun, Lin and Gregory, Professor Duncan
• Authors: Fan, Z., Liu, W.-R., Sun, L., Nishio, A., Szczesny, R., Lin, Y.-G., Okada, S., and Gregory, D. H.
• College/School: College of Science and Engineering; College of Science and Engineering > School of Chemistry
• Journal Name: ACS Applied Materials and Interfaces
• Publisher: American Chemical Society
• ISSN: 1944-8244
• ISSN (Online): 1944-8252
• Published Online: 19 July 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in ACS Applied Materials and Interfaces 15(30):36076-36085
• Publisher Policy: Reproduced under a Creative Commons license

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
190912		High throughput microwave synthesis of Li-ion battery materials	Serena Corr	Engineering and Physical Sciences Research Council (EPSRC)	EP/N001982/1	Chemistry
305672		New non-oxide electrolytes for all-solid-state Li-ion batteries	Duncan Gregory	The Royal Society (ROYSOC)	IEC\R3\183040	Chemistry