Nonuniform Ionic and Electronic Transport of Ceramic and Polymer/Ceramic Hybrid Electrolyte by Nanometer‐Scale Operando Imaging for Solid‐State Battery

Abstract

Replacing the liquid electrolyte in lithium batteries with solid‐state ion conductor is promising for next‐generation energy storage that is safe and has high energy density. Here, nanometer‐resolution ionic and electronic transport imaging of Li3PS4 (LPS), a solid‐state electrolyte (SSE), is reported. This nm resolution is achieved by using a logarithm‐scale current amplifier that enhances the current sensitivity to the fA range. Large fluctuations of ion current—one to two orders of magnitude on the LPS and on the LPS region of a polymer/LPS bulk hybrid SSE—that must be mitigated to eliminate Li dendrite formation and growth, are found. This ion current fluctuation is understood in terms of highly anisotropic transport kinetic barriers along the different crystalline axes due to different grain orientations in the polycrystalline and glass ceramic materials. The results on the bulk hybrid SSE show a sharp transition of ionic and electronic transport at the LPS/polymer boundary and decreases in average ionic current with decreasing polyimine particle size and with extensive cycling. The results elucidate the mechanism of polyimine extension into interparticles to prevent Li dendrite growth. This work opens up novel characterization of charge transport, which relates to Li plating and stripping for solid‐state‐batteries.

Mesoscale Interrogation Reveals Mechanistic Origins of Lithium Filaments along Grain Boundaries in Inorganic Solid Electrolytes

“…A very recent study has developed nanometer‐scale operando imaging and detected ionic current fluctuations of one to two orders of magnitude in a Li 3 PS 4 (LPS) system. [ 30 ] While the occupation ratios in the grain and GB regions captured by our simulations (for E a − GB = 0.40 eV) are of comparable magnitudes, we observed larger differences in the ion occupation ratios upon increasing the activation barrier in the GB. Results for E a − GB = 0.43 eV have been presented in Section S2 of the Supporting Information.…”

Polymer-based hybrid battery electrolytes: theoretical insights, recent advances and challenges

“…The spatial heterogeneity in materials properties may lead to non-uniform contact and potentially non-uniform ionic ux at electrode interface. 193 In situ AFM recently performed on a LPS/polyimine hybrid solid electrolyte found that ionic transport through the electrolyte could vary by an order of magnitude depending on where a measurement was taken. The non-uniform ionic ux was attributed to the highly complicated, tortuous pathway.…”

“…The non-uniform ionic ux was attributed to the highly complicated, tortuous pathway. 183,193 Regions with greater polymer content demonstrate less ionic and electronic current, which suggests that the dominant transport pathway was through the sulde solid electrolyte. This observation contradicts ndings on oxides, 4 and suggests that transport in these hybrid systems is highly complex and depends on the variety of factors: the polymer, the ller, the salt and the interplay between these components.…”

Characterizing Batteries by In Situ Electrochemical Atomic Force Microscopy: A Critical Review

“…[ 293 ] With a biased probe scanning the sample surface, AFM was also used to investigate the nanoscale inhomogeneity of ionic and electronic transport in Li 3 PS 4 and its Li 3 PS 4 /polymer electrolytes. [ 294 ] The local ionic conductivity was found to differ by one to two orders‐of‐magnitude across the Li 3 PS 4 SSE. The ionic conductivity mapping indicated a sharp transition of ion transport at the boundary of polyimine/Li 3 PS 4 grains due to different grain orientations in the polycrystalline and glass ceramic materials (Figure 14c–e).…”

“…Reproduced with permission. [ 294 ] Copyright 2020, Wiley‐VCH. f) Schematic of the in situ C‐AFM measurement on the all‐solid‐state thin‐film battery.…”