Effects of metal substrate types on Li-ion battery anode properties of Si thin films

Abstract Si anodes are gaining attention as next-generation thin-film batteries owing to their low cost, safety, and high lithium-ion capacity. However, the lifetime of Si anodes is very short because of volume changes during lithium-ion insertion and extraction. In this study, we tested the hypothesis that the electronegativity difference between Si and a metal substrate governs the adhesion strength and thereby affects the electrochemical performance. To verify this hypothesis, we evaluated the performance of Si thin-film anodes for lithium-ion batteries using eight metal substrates. The charge/discharge characteristics of Si anodes were greatly influenced by the type of substrate and substrates with a larger electronegativity difference exhibited stronger adhesion and higher capacity retention. Annealing further improved the adhesion of Si thin films and enhanced their charge/discharge performance, particularly for refractory metals, achieving capacities exceeding those of typical Si thin-film anodes. These results demonstrate that controlling the adhesion between the Si film and the substrate through electronegativity-based design is critical for improving anode performance and extending cycle life. This study highlights the originality of introducing electronegativity difference as a quantitative and universal descriptor for Si thin-film anodes, providing important insights into the development of next-generation thin-film rechargeable batteries.