Lithium trapping, hydrogen content, and solid electrolyte interphase growth in electrodeposited silicon anodes by ion beam analysis

Techniques for quantitatively characterizing electrode composition are crucial for comprehending battery degradation. However, these methods are typically destructive and lack sensitivity to light elements like lithium and hydrogen. In our study, we utilize non-destructive ion beam analysis techniques to quantitatively determine the accumulation and depth profiles of trapped lithium and solid electrolyte interphase (SEI) components during the cycling of electrodeposited silicon thin film anodes (EDEP-Si, ∼300 nm). Our quantitative findings reveal that lithium begins to be trapped during the initial SEI formation cycle, with its concentration increasing from ∼20 % to ∼40 % within the first 10 cycles. The total quantity of lithium in the anode continues to increase until plateauing after 20 cycles. Lithium tends to interact with oxygen, forming buffer matrix lithium silicates and lithium oxides, which contribute to favorable cycling performance. Additionally, hydrogen, carbon, oxygen, and fluorine are quantified during anode cycling, with hydrogen exhibiting a similar trend to oxygen, while carbon and fluorine concentrations remain at 6 % or less. Energy-dispersive X-ray spectroscopy (EDS) is employed to validate NRA results. Thus, quantitative NRA analysis offers insights into lithium behavior within both the bulk electrode and electrode surface.