High-Performance Anodes Made of Metallic Lithium Layers and Lithiated Silicon Layers Prepared by Vacuum Technologies

Abstract

Replacing conventional electrode materials is one of the most pressing challenges for next-generation lithium-ion batteries since state-of-the-art systems have almost reached their limitations for performance gains. For anodes, ambitious candidates include lithium and silicon because of their extremely high capacity. In this paper, a physical vapor deposition process for the preparation of pure metallic lithium layers and lithiated silicon layers in the layer thickness range of 1–20 µm is demonstrated. The lithium layers were deposited by thermal evaporation. Static coating rates up to 120 nm/s and dynamic deposition rates up to 1 µm·m/min were realized. Furthermore, the deposition of lithiated silicon alloy layers with various compositions was performed via the co-evaporation of lithium and silicon, where silicon was evaporated by an electron beam. The process was characterized regarding the deposition rate, heat loads, and effects of substrate pre-treatment. To achieve a porous microstructure, the layer morphology needed to be manipulated by adapting process parameters. Stripping experiments revealed high electrochemical activity of the lithium up to 85 %. The innovative approach carried out via vacuum processing showed capabilities for overcoming the current bottlenecks experienced with high-capacity anode materials in combination with the potential for upscaling to high throughput production.