Fabian Peters

Spatiotemporal Changes of the Solid Electrolyte Interphase in Lithium‐Ion Batteries Detected by Scanning Electrochemical Microscopy

The solid electrolyte interphase (SEI) in lithium-ion batteries separates the highly reductive lithiated graphite from reducible electrolyte components. It is critical for the performance, durability, and safe operation of batteries. In situ imaging of the SEI is demonstrated using the feedback mode of scanning electrochemical microscopy (SECM) with 2,5-di-tert-butyl-1,4-dimethoxy benzene as mediator. The formation of the SEI is indicated by a decrease of the mediator regeneration rate. Prolonged imaging of the same region revealed fluctuation of the passivating properties on time scales between 2 min and 20 h with an inhomogeneous distribution over the sample. The implications of the approach for in situ assessment of local SEI properties on graphite electrodes are discussed with respect to studying the influence of mechanical stress on SEI reliability and the mode of action of electrolyte additives aiming at improving SEI properties.

Lithiation Behavior of Silicon Nanowire Anodes for Lithium-Ion Batteries: Impact of Functionalization and Porosity

Metal-assisted chemical etching (MACE) provides a versatile way to synthesize silicon nanowires (SiNW) of different morphologies. MACE was used to synthesize oxide-free porous and nonporous SiNW for use as anodes for lithium-ion batteries. To improve their processing behavior, the SiNW were functionalized using acrylic acid. Differential capacity plots were used as a way to identify the degradation processes during cycling through tracking the formation of Li15 Si4 and changes in polarization. The cycling performance between porous and nonporous SiNW differed regarding Coulombic efficiency and cycling stability. The differences were attributed to the porous hull and its ability to reduce the volume expansion, although not through its porous nature but the reduced uptake of Li ions.