Morphology and interfacial design of SnO₂ thin-film anodes for high-performance lithium-ion batteries

The continuous demand for high-performance lithium-ion batteries (LIBs) has accelerated the development of microscale energy storage systems with improved specific and volumetric capacities. Tin oxide (SnO₂) is a promising anode material due to its high theoretical capacity and favorable lithiation properties; however, its practical application is hindered by significant volume changes and unstable electrode-electrolyte interfaces during cycling. Here, we systematically investigate the impact of thin film morphology and artificial interface engineering on the electrochemical performance of radio frequency (RF) magnetron-sputtered SnO₂ anodes. By optimizing deposition and annealing parameters, we achieve porous SnO₂ architectures with enhanced cycling stability. A subsequent carbon coating reduces electrolyte contact and buffers volume expansion, while the incorporation of 5 wt% vinylene carbonate (VC) into the electrolyte enables the formation of a robust, elastic solid electrolyte interphase (SEI). The dual approach - combining engineered porosity with interfacial stabilization - significantly improved capacity retention, suppressed polarization, and ensured high coulombic efficiency over 200 cycles. Post-mortem scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) analyses confirm that the carbon coating and VC worked synergistically to preserve structural integrity, minimized side reactions, and promoted favorable SEI composition. These results highlight an effective strategy for designing durable, high-capacity SnO₂-based thin film anodes for next-generation LIBs.