Excimer ultraviolet-irradiated exfoliated graphite loaded with carbon-coated SnOx small nanoparticles as advanced anodes for high-rate-capacity lithium-ion batteries

Abstract

This paper reports a fast and efficient excimer ultraviolet (EUV) radiation method to prepare carbon-coated mixed tin oxide-loaded exfoliated graphite (SnO_x@C-G) nanocomposites. The SnO_x small nanoparticles (SNPs) are isolated using oxidized sucrose and uniformly deposited onto mildly oxidized exfoliated graphite during the 20-minute EUV radiation process. XPS and ESR analyses suggest the existence of abundant oxygen vacancies in the SnO_x SNPs. The electrochemical kinetics of SnO_x@C-G, which are determined by in situ electrochemical impedance analysis, demonstrated a high reversible capacity of approximately 740 mA h g⁻¹ after 250 cycles at a current density of 1.6 A g⁻¹, and an impressive reversible rate performance exceeding 450 mA h g⁻¹ can be obtained even at a high current density of 3.2 A g⁻¹ when applied as an anode for lithium storage. This improved cycling stability and rate capability benefit from the carbon coating, which not only buffers the volume change of SnO_x SNPs but also provides a path for electron transport on the surface of the SnO_x SNPs during the electrochemical process. Furthermore, the oxygen vacancies in SnO_x SNPs result in a large capacitive contribution to capacity. The EUV radiation method used to synthesize SnO_x@C-graphite nanosheets is universally applicable to prepare a high-performance SNPs/carbon-based anode for lithium-ion batteries.