Visualizing Local Electrical Properties of Composite Electrodes in Sulfide All-Solid-State Batteries by Scanning Probe Microscopy

Abstract

Studies on local conduction paths in composite electrodes are essential to the realization of high-performance sulfide all-solid-state lithium batteries. Here, we directly evaluate the electrical properties of individual LiNi1/3Mn1/3Co1/3O2 (NMC) electrode active material particles in composite positive electrodes by scanning probe microscopy (SPM) techniques. Kelvin probe force microscopy (KPFM) and scanning spreading resistance microscopy (SSRM) are combined. The results indicate that all NMC particles exhibit a charged state with increasing potential, but low electronic conduction paths exist at point of contacts of some NMC particles. Furthermore, the I–V characteristics measured by conductive atomic force microscopy (C-AFM) suggest that these specific NMC particles show low charge–discharge reactivity. The results of the SPM techniques indicate that poor conduction locally limits the charge–discharge reactivity of electrode active materials, leading to the degradation of battery performance. Such an SPM combination accelerates the morphological optimization of composite electrodes by facilitating the investigation of the intrinsic electrical properties of the electrodes.

Emerging Characterization Techniques for Electrode Interfaces in Sulfide‐Based All‐Solid‐State Lithium Batteries

“…One benefit of using AFM or scanning probe microscopy (SPM)‐related characterizations is their capabilities to study the local electrical properties of the electrode. Sakuda and co‐workers [ 77 ] rationally used SPM and conductive AFM (C‐AFM) to measure the resistance and current distribution of the sulfide cathode composition, respectively. They found that the poor conduction locally limits the charge−discharge reactivity of CAMs, which originated from the poor and uniform interface contact between sulfide SEs and CAM particles.…”

A critical discussion on the analysis of buried interfaces in Li solid-state batteries. Ex situ and in situ/operando studies

“…In order to address this challenge, Atsushi Sakuda et al have successfully developed a single sample holder allowing for performing BIB polishing and the analysis of the prepared cross-section by SPM and scanning electron microscopy -energy-dispersive X-ray spectroscopy (SEM-EDS) in the three different instruments. 40 Another adventitious problem with cross-sections prepared by mechanical methods or BIB polishing is pollution due to sample handling for changing of sample holder or contact with the atmosphere of the gloves box. This fortuitous degradation can makes difficult, in some cases, probing the chemical composition of cross-sections with surface analytical techniques, particularly with methods characterised by thin sampling depths like time-of-flight secondary ion mass Spectrometry (ToF-SIMS).…”

“…As discussed in the introduction of section 3.1.1, this operation can ruin the analysis step. A significant advancement to overcome this issue Please do not adjust margins Please do not adjust margins has been recently developed 40 by Atsushi Sakuda et al, which was also discussed in the introduction of section 3.1.1.…”

“…The ESM experiments evidenced the emergence of strain at grain boundaries due to Li + accumulation after local negative polarization of the surface. More recently, Atsushi Sakuda et al have published an outstanding study 40 combining three different SPM techniques and SEM/EDS measurements to assess the electrical properties of a composite cathode, containing only the active material and the solid electrolyte, in a LiNi0.33Mn0.33Co0.33O2 (NMC 111)/LPS/Li battery. In order to prepare a flat and reproducible cross-section of the layered sample, BIB polishing was carried out under cryogenic conditions (-100 °C).…”

Spatially Resolved Potential and Li-Ion Distributions Reveal Performance-Limiting Regions in Solid-State Batteries

“…Here, sharp composition changes at the interface between materials with different Li chemical potentials μ Li ( x ) drive the buildup of the Galvani potential ϕ­( x ) and the electrochemical potential of electrons across the interface. Despite recent experimental measurements of electric potential distributions using electron holography , and Kelvin probe force microscopy (KPFM), − these results have been challenging to interpret because they have not yet been correlated with ion distributions or directly related to battery performance. Here, we use KPFM combined with neutron depth profiling (NDP) − to correlate CPD distributions and Li-ion concentrations across interfaces in similar SSBs.…”