Insights into Chemical Prelithiation of SiO_x/Graphite Composite Anodes through Scanning Electron Microscope Imaging

Abstract

Initial Coulombic efficiency (ICE) is critical for determining the energy density of lithium-ion batteries (LIBs) used for practical applications; however, it is typically disregarded in anode research. We used SiO x and graphite composite anodes for commercial lithium-ion batteries in our preliminary research to achieve a balance between ICE, capacity, and cycling life. ICE reached 88%; however, it needs further improvement for commercial applications. Prelithiation is a process that involves the introduction of extra lithium ions into LIBs during their manufacturing to enhance the overall performance of the LIBs. We applied a chemical prelithiation method on our SiO x /graphite composite anodes, which comprised 95 wt % of the active material mass loading on the electrode. The ICE increased from 88% to 98% using an aryllithium reagent impregnation method within 2 min of prelithiation. The anode’s specific capacity density, rate, and cycle performance also significantly improved. Scanning electron microscopy (SEM) imaging enhanced by an osmium tetroxide staining method indicated that the P-anode contained a stable solid electrolyte interface (SEI) layer after the prelithiation process and cycling electrochemical test. The P-anode’s stable charge differential peak over 500 cycles also showcases a robust artificial SEI layer that was generated by the prelithiation procedure. This prelithiation process has significant potential for adoption in the LIB industry’s current electrode manufacturing process.

Lithium sulfide: a promising prelithiation agent for high‐performance lithium‐ion batteries

“…The extra charge capacities in the first few cycles correspond to SEI formation. [48][49][50][51][52] The prelithiation agents as extra lithium sources irreversibly release active Li + in the first cycle, during the process of which the unstable electrolyte decomposes by intaking Li + to form Li-containing compounds on the anode surface (Figure 1A). These compounds, including LiF, Li 2 CO 3 , Li x PF y , Li x SiF y , Li x SiO y and lithium alkyl carbonate components, are so thermodynamically stable that the SEI formation is irreversible.…”