Near-Field IR Investigations of the Solid Electrolyte Interphase Layer On Sn

A strong understanding of the solid electrolyte int erphase (SEI) (1,2) layer in lithium-ion batteries is neces sary for further development of the technology, leading the path to application of high energy density intermetallic an odes However, the identification of chemical compounds i n this surface layer, as well as their spatial distri bution, has been limited by diffraction to the 5-10 μm waveleng th scale available to traditional Fourier Transform In frared spectroscopy (FTIR). Here we demonstrate, for the f irst time, deeply subwavelength imaging of the SEI using infrared (IR) near-field scanning optical microscop y (NSOM).