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Title: Mapping Ionic Currents and Reactivity on the Nanoscale: Electrochemical Strain Microscopy

Solid-state electrochemical processes in oxides underpin a broad spectrum of energy and information storage devices, ranging from Li-ion and Li-air batteries, to solid oxide fuel cells (SOFC) to electmore »roresistive and memristive systems. These functionalities are controlled by the bias-driven diffusive and electromigration transport of mobile ionic species, as well as intricate a set of electrochemical and defect-controlled reactions at interfaces and in bulk. Despite the wealth of device-level and atomistic studies, little is known on the mesoscopic mechanisms of ion diffusion and electronic transport on the level of grain clusters, individual grains, and extended defects. The development of the capability for probing ion transport on the nanometer scale is a key to deciphering complex interplay between structure, functionality, and performance in these systems. Here we introduce Electrochemical Strain Microscopy, a scanning probe microscopy technique based on strong strain-bias coupling in the systems in which local ion concentrations are changed by electrical fields. The imaging capability, as well as time- and voltage spectroscopies analogous to traditional current based electrochemical characterization methods are developed. The reversible intercalation of Li and mapping electrochemical activity in LiCoO2 is demonstrated, illustrating higher Li diffusivity at non-basal planes and grain boundaries. In Si-anode device structure, the direct mapping of Li diffusion at extended defects and evolution of Li-activity with charge state is explored. The electrical field-dependence of Li mobility is studied to determine the critical bias required for the onset of electrochemical transformation, allowing reaction and diffusion processes in the battery system to be separated at each location. Finally, the applicability of ESM for probing oxygen vacancy diffusion and oxygen reduction/evolution reactions is illustrated, and the high resolution ESM maps are correlated with aberration corrected scanning transmission electron microscopy imaging. The future potential for deciphering mechanisms of electrochemical transformations on an atomically-defined single-defect level is discussed.« less
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Title: Mapping Ionic Currents and Reactivity on the Nanoscale: Electrochemical Strain Microscopy
Authors:
Publication Date: 2010-10-19
OSTI Identifier: 1008014
DOE Contract Number: AC04-94-AL85000
Other Number(s): TRN: US201122%%7
Resource Type: Multimedia
Resource Relation: Conference: Energy Research Frontier Center Seminar Presentation, October 2010
Research Org: SNL (Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States))
Sponsoring Org: USDOE Office of Science (SC)
Subject: 30 DIRECT ENERGY CONVERSION ; CHARGE STATES ; DEFECTS ; DIFFUSION ; ELECTROPHORESIS ; GRAIN BOUNDARIES ; MICROSCOPY ; OXIDES ; OXYGEN ; PERFORMANCE ; PROBES ; RESOLUTION ; SOLID OXIDE FUEL CELLS ; STORAGE ; STRAINS ; TRANSFORMATIONS ; TRANSMISSION ELECTRON MICROSCOPY ; TRANSPORT
Country of Publication: United States
Language: English
Run Time: 1:09:59
System Entry Date: 2016-01-27