| Abstract | The formation of c-Li₃.₇₅Si is known to be detrimental to silicon anodes in lithium-ion batteries. To suppress the formation of this crystalline phase and improve the electrochemical performance of Si-based anodes, three approaches were amalgamated: addition of a nickel adhesion sublayer, alloying of the silicon with titanium, and addition of either carbon or TiO₂ as a capping layer. The silicon-based films were analyzed by a suite of methods, including scanning electron microscopy (SEM) and a variety of electrochemical techniques, as well as X-ray photoelectron spectroscopy (XPS) to provide insights into the composition of the resulting solid-electrolyte interphase (SEI). A nickel adhesion layer decreased the extent of delamination of the silicon from the underlying copper substrate, compared to Si deposited directly on Cu, which resulted in less capacity loss. Alloying of silicon with titanium (85% silicon, 15% titanium) further increased the stability. Finally, capping these multilayer electrodes with either a thin 10 nm layer of carbon or TiO₂ resulted in the best electrode behavior and lowest cumulative relative irreversible capacity. TiO₂ is slightly more effective in enhancing the capacity retention, most likely due to differences in the resulting solid-electrolyte interphase (SEI). The combination of an adhesion layer, alloying, and surface coatings shows a cumulative suppression of the formation of c-Li₃.₇₅Si and SEI, resulting in the greatest improvement of capacity retention when all three are incorporated together. However, these strategies appear to only delay the onset of the c-Li₃.₇₅Si phase; eventually, the c-Li₃.₇₅Si phase will form, and at that point, the capacity degradation rate of all the electrodes becomes similar. |
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