Prelithiation of silicon thin film anodes using ion implantation for lithium ion batteries

Silicon is the most promising anode material for lithium ion batteries (LIBs) because of its high theoretical specific capacity of 3590 mAhg −1 in the Li 3.73 Si phase at room temperature. However, two important issues such as volume expansion after the lithiation and the growth of a solid electrolyte interface during the cycling on the anodic side hinder the full use of Si as a negative electrode in modern LIBs. Here, we prelithiate the Si thin film on Cu foil using Li + ion implantation at room temperature with a fluence of 10 16 ions/ cm 2 and three implantation energies of 1, 2 and 3 keV in order to achieve different depth profiles. The ion implantation enables a high controllability and homogeneity of the Li ion profile in the near surface region of the Si anode. Using both a half and full cell configuration versus lithium nickel cobalt aluminum oxide (NCA) in a liquid electrolyte (1 M LiPF 6 , EC:DMC 1:1 and 2 wt% of FEC), the implanted Si anodes were cycled and compared to Si anodes without implantation. The morphology and the structure of the Si anodes were investigated using scanning electron microscopy (SEM) in combination with elemental analysis by energy-dispersive X-ray spectroscopy (EDX) and x-ray diffraction (XRD). Depth profiles of the implanted Li + in the Si anode obtained by elastic recoil detection analysis (ERDA) reveal that the distribution of the implanted Li + extends from the surface to a depth of ca. 80 nm (deeper than predicted by simulations), which is caused by the roughness of the Cu foil. The roughness of the Si anode on Cu was analyzed using atomic force microscopy (AFM). • Prelithiation of a Si anode for a lithium ion battery using ion implantation technology. • Depth profiles of the implanted Si anodes were determined using ERDA. • Capacity improvement of cells with the implanted Si anode shows the potential of this technology. • Full cell discharging up to 10C of the implanted Si anode versus balanced NCA cathode.