In Situ Electrochemical Mapping of Lithium–Sulfur Battery Interfaces Using AFM–SECM

Abstract

Although lithium–sulfur (Li–S) batteries are explored extensively, several features of the lithium polysulfides (LiPS) redox mechanism at the electrode/electrolyte interface still remain unclear. Though various in situ and ex situ characterization techniques have been deployed in recent years, many spatial aspects related to the local electrochemical phenomena of the Li-S electrode are not elucidated. Herein, we introduce the atomic-force-microscopy-based scanning electrochemical microscopy (AFM–SECM) technique to study the Li–S interfacial redox reactions at nanoscale spatial resolution in real time. In situ electrochemical and alternating current (AC) phase mappings of Li2S particle during oxidation directly distinguished the presence of both conducting and insulating regions within itself. During charging, the conducting part undergoes dissolution, whereas the insulating part, predominantly Li2S, chemically/electrochemically reacts with intermediate LiPS. At higher oxidation potentials, as-reacted LiPS turns into insulating products, which accumulate over cycling, resulting in reduction of active material utilization and ultimately leading to capacity fade. The interdependence of the topography and electrochemical oxidative behavior of Li2S on the carbon surface by AFM–SECM reveals the Li2S morphology–activity relationship and provides new insights into the capacity fading mechanism in Li–S batteries.

Optimizing Redox Reactions in Aprotic Lithium–Sulfur Batteries

“…One step forward, in situ AFM‐based scanning electrochemical microscopy (AFM–SECM) was proposed for real‐time studying the Li–S redox reaction interface in nanoscale spatial resolution. [ 68 ] In situ electrochemical and alternating current (AC) phase mappings of Li 2 S particle during charging can distinguish the electrochemically insulative inactive and conductive active regions. Figure 5d depicts the phase mappings recorded on the Li 2 S/Li 2 S 2 particle at various oxidation potentials (2.5–2.7 V), respectively.…”

In-situ/operando characterization techniques in lithium-ion batteries and beyond

“…What's more, the evolution of cathode electrolyte interface (CEI) and surface chemical properties were studied in various battery systems as well [177][178][179]. Together with other techniques, in-situ SECM proved that the emergence of CEI on LiMn 2 O 4 cathode was the result of salt decomposition [178].…”

Scanning Probe Microscopy Facility for Operando Study of Redox Processes on Lithium ion Battery Electrodes

“…These changes are converted into corrective movements of the probe that ensure that the probe accurately follows the surface. This technique can be used to create a 3D surface scan of all conceivable and measurable parameters between sample and probe with resolutions up to the nanometer scale (Nagpure et al, 2010;Amanieu et al, 2015;Kim et al, 2018;Benning et al, 2019;Mahankali et al, 2019).…”

“…More and more researchers are using in-situ measurement methods (Doi et al, 2008;Inaba et al, 2011;Demirocak and Bhushan 2014;Wang et al, 2014;Huang et al, 2018;Benning et al, 2019;Mahankali et al, 2019) where information about interface processes can be investigated without influencing them. In general, to perform in situ measurements, the battery process is temporarily or completely stopped, after which measurements are taken.…”