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

Misae Otoyama,Yuki Inagi,Atsushi Sakuda,Hiroyuki Ito,Masahiro Tatsumisago,Takehiro Yamaoka,Akitoshi Hayashi

doi:10.1021/acs.jpcc.0c10148

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.

Highlights

All-solid-state lithium batteries (ASSLBs) are promising power sources for next-generation low-carbon societies.[1,2] One of their primary advantages is their high safety factor as they replace flammable organic liquid electrolytes with nonflammable inorganic solid electrolytes (SEs)
We directly investigated the potential distribution in the electrodes with and without initial charging by Kelvin probe force microscopy (KPFM) to discuss about state of charge (SOC) distributions in each NMC particle
The results showed that charge− discharge reactions proceeded preferentially from the SE-layer side because the rate-determining step was related to Li+-ion conduction, indicating that the potential of NMC increased from the SE-layer side

Summary

Introduction

All-solid-state lithium batteries (ASSLBs) are promising power sources for next-generation low-carbon societies.[1,2] One of their primary advantages is their high safety factor as they replace flammable organic liquid electrolytes with nonflammable inorganic solid electrolytes (SEs). KPFM was conducted on the NMC composite positive electrodes using a scanning probe microscope (AFM5300E; Hitachi High-Tech Corp.).

Results

Conclusion