Improved electrochemical performance and solid electrolyte interphase properties of electrolytes based on lithium bis(fluorosulfonyl)imide for high content silicon anodes

Deciphering the Impact of Current, Composition, and Potential on the Lithiation Behavior of Si-Rich Silicon-Graphite Anodes

Adding silicon (Si) to graphite (Gr) anodes is an effective approach for boosting the energy density of lithium-ion batteries, but it also triggers mechanical instability due to Si volume changes upon (de)lithiation reactions. In this work, component-specific (de)lithiation dynamics on Si-rich (30 and 70 wt.% Si) SiGr anodes at various charge/discharge C-rates are unveiled and compared to a graphite-only electrode (100Gr) via operando synchrotron X-ray diffraction coupled with differential capacity plots analysis. Results show preferential lithiation of amorphous Si above ≈200 mV and competing lithiation of Gr, amorphous Si, and crystalline Si below ≈200 mV. Discharge proceeds via sequential delithiation of Gr and amorphous lithium silicide. Si shifts the interconversion potentials of graphite intercalation compounds, lowering the Gr state of charge compared to 100Gr. In the 30% Si electrode, crystalline Si amorphization at potentials <110 mV is found to be kinetically hindered at C-rates higher than C/5, which can be key for enhancing the cycling stability of SiGr anodes. The 70% Si electrode exhibits restricted lithium diffusion in Gr, full Si amorphization, and Li15Si4 formation. These findings related to the potential- and current-dependent dynamic changes on SiGr blends are crucial for designing stable high energy density SiGr anodes.

Imaging the Surface/Interface Morphologies Evolution of Silicon Anodes Using in Situ/Operando Electron Microscopy

Si-based rechargeable lithium-ion batteries (LIBs) have generated interest as silicon has remarkably high theoretical specific capacity. It is projected that LIBs will meet the increasing need for extensive energy storage systems, electric vehicles, and portable electronics with high energy densities. However, the Si-based LIB has a substantial problem due to the volume cycle variations brought on by Si, which result in severe capacity loss. Making Si-based anodes-enabled high-performance LIBs that are easy to utilize requires an understanding of the fading mechanism. Due to its distinct advantage in morphological changes from microscale to nanoscale, even approaching atomic resolution, electron microscopy is one of the most popular methods. Based on operando electron microscopy characterization, the general comprehension of the fading mechanism and the morphology evolution of Si-based LIBs are debated in this review. The current advancements in compositional and structural interpretation for Si-based LIBs using advanced electron microscopy characterization methods are outlined. The future development trends in pertinent silicon materials characterization methods are also highlighted, along with numerous potential research avenues for Si-based LIBs design and characterization.