Multi-characterization of LiCoO2 cathode films using advanced AFM-based techniques with high resolution

Abstract

AbstarctThe thin film Li-ion batteries have been extensively used in micro-electronic devices due to their miniaturization, high capacity density and environmental friendliness, etc. In order to further prolong the lifetime of the film batteries, one of important tasks is to explore the aging mechanisms of the cathode films. In this paper, we especially focused on the multi-characterization of the LiCoO2 film in nanoscale, which is carried out by combining advanced AFM-based techniques with capacity measurement. The surface morphology, contact stiffness as well as surface potential were measured by amplitude modulation-frequency modulation (AM-FM) and kelvin probe force microscope (KPFM), respectively. Remarkable changes after different numbers of charge/discharge cycling were observed and the intrinsic reasons of them were discussed in detail. To acknowledge the relationship with these microscopic changes, the macro-capacity of the thin films was also measured by the galvanostatic charge/discharge method. These comprehensive results would provide a deep insight into the fading mechanism of the cathode film, being helpful for the design and selection of the cathode film materials for high performance batteries.

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

“…The surface potential decrease is related to the irreversible Li + intercalation/de‐intercalation and CEI formation. From these results, they find that the capacity fading is attributed to the degradation of contact stiffness and surface potential …”

“…Grain size and stiffness and RMS surface roughness and stiffness with different cycle number. Copyright 2017, Springer Nature . d) In situ AFM images of the CEI formation on the edge plane of LiCoO 2 crystal.…”

“…The AFM tip keeps neutral in delicate imaging process; therefore, accurate in situ information about surface evolution can be obtained with minimal destruction. The mechanical properties of materials can be measured by nano‐indentation ( Figure c) and amplitude modulation–frequency modulation (AM–FM) (Figure d) . The dynamic strain response to applied electric bias to tip is detected by electrochemical strain microscopy (ESM) (Figure f) .…”

“…c) nano‐indentation, Copyright 2012, American Chemical Society . d) AM – FM , Copyright 2017, Springer Nature . e) c‐ AFM , Copyright 2016, American Chemical Society .…”

Monitoring dynamic electrochemical processes with in situ ptychography

“…Experimental access to localization descriptors of electrochemical phase formation processes is currently possible, thanks to a suite of advanced, mainly synchrotron-based in situ microspectroscopic methods with imaging, topological, chemical and structural capability. Thus, the use of these methods, exhibiting space resolution suitable to address the functionally relevant scales, is starting to gain recognition in the battery community (Wu et al 2017;Lee et al 2017). In particular, imaging and structural methods based on X-rays, such as absorption near-edge spectroscopy, fluorescence, diffraction and scattering, are regarded as the cutting-edge tools for the study of buried electrochemical interfaces (Ebner et al 2013;Lin et al 2017;Sun et al 2017).…”