Determination of Lithium-Ion Distributions in Nanostructured Block Polymer Electrolyte Thin Films by X-ray Photoelectron Spectroscopy Depth Profiling

Abstract

X-ray photoelectron spectroscopy (XPS) depth profiling with C60(+) sputtering was used to resolve the lithium-ion distribution in the nanometer-scale domain structures of block polymer electrolyte thin films. The electrolytes of interest are mixtures of lithium trifluoromethanesulfonate and lamellar-forming polystyrene-poly(oligo(oxyethylene)methacrylate) (PS-POEM) copolymer. XPS depth profiling results showed that the lithium-ion concentration was directly correlated with the POEM concentration. Furthermore, chemical state and atomic composition of the film were analyzed through the deconvolution of the C1s signal, indicating that the lithium ions appear to be uniformly distributed in the POEM domains. Overall, the unique capabilities of C60(+) depth profiling XPS provide a powerful tool for the analysis of nanostructured polymer thin films in applications ranging from energy storage and generation to surface coatings and nanoscale templates.

Lithium Salt-Induced Microstructure and Ordering in Diblock Copolymer/Homopolymer Blends

“…5,11,12 In such systems, lithium salts have been shown to partition exclusively to the PEO domain. 13,14 Wang and co-workers have suggested that this selective partitioning is primarily due to the large solvation energy gained when the lithium salts complex and associate with the polar PEO domains, leading to a large increase in the effective segregation strength with lithium salt loading. 15,16 Experimental studies have taken advantage of this intriguing behavior to readily and dramatically tune the segregation strength of PS−PEO block copolymers through the addition of a lithium salt, and these studies have shown that a wide range of morphologies can be accessed without the need to modulate temperature.…”

Directional Self‐Assembly of Fluorinated Star Block Polymer Thin Films Using Mixed Solvent Vapor Annealing

“…Rigaku Globalfit software was used to fit the XRR profile with repeating lamellae models. The XRR profiles facilitated determination of the polymer densities and interfacial roughnesses through fitting of the oscillation amplitudes, while the layer thicknesses were evaluated by fitting the oscillation periods . The XRR fitting herein used a multiresponse nonlinear regression approach .…”

Depth resolution in sputter profiling revisited

“…Multilayers are frequently used to disclose the depth dependence of the depth resolution . If the distance of the single layers is large enough (and Δ z is small enough) to ensure that the profiles of layers of A are separated by layers of B and do not overlap, the layers of A can be treated like single layers, and Eqn applies (see Fig.…”

“…In contrast to the UDS model, the MRI model correctly predicts the shift of the measured interface or delta layer profile with respect to the original layer location, and it has been successfully applied to SIMS, AES and XPS depth profiles. The MRI‐DRF can be presented either as an analytical or as a numerical solution both for delta layers and single (thicker) layers.…”

“…In the MRI model, the DRF is represented by three fundamental, physically well‐defined parameters: atomic Mixing, Roughness and Information depth (with every parameter given by a quantity characteristic for the analysis method applied). Thus, the depth resolution Δ z directly depends on the respective values of the above parameters which establish the DRF (see section on Asymmetric, non‐Gaussian DRF for interfaces and delta layers). For simplicity, matrix effects and preferential sputtering are ignored in the following.…”