Abstract: Despite its high capacity behavior as the anode for lithium-ion batteries (LIBs), SnO₂ suffers the poor electronic conductivity and high volume expansion, which lead to poor cycling stability and rate capability. In this study, we employ defect engineering to design SnO_2-x (x = 0, 0.12, 0.2, and 0.3) nanoparticles with varied oxygen vacancies. Notably, the SnO_1.80 electrode with 20 % oxygen vacancies exhibits excellent electrochemical performance. Advanced physical characterizations combined with density functional theory (DFT) simulations demonstrate that the improved electrochemical performance can be attributed to the formation of a stable, uniform, and LiF-rich solid-electrolyte interface (SEI) layer through the optimization of oxygen vacancies. This study shows novel insights into the application of defect engineering within oxides for the rational design of the uniform surface layer toward high-energy-density LIBs.

Key words: SnO₂, Oxygen vacancy, SEI, Reversible intercalation, Li-ion batteries