Abstract
Understanding how particle size and morphology influence ion insertion dynamics is critical for a wide range of electrochemical applications including energy storage and electrochromic smart windows. One strategy to reveal such structure–property relationships is to perform ex situ transmission electron microscopy (TEM) of nanoparticles that have been cycled on TEM grid electrodes. One drawback of this approach is that images of some particles are correlated with the electrochemical response of the entire TEM grid electrode. The lack of one-to-one electrochemical-to-structural information complicates interpretation of genuine structure/property relationships. Developing high-throughput ex situ single particle-level analytical techniques that effectively link electrochemical behavior with structural properties could accelerate the discovery of critical structure-property relationships. Here, using Li-ion insertion in WO3 nanorods as a model system, we demonstrate a correlated optically-detected electrochemistry and TEM technique that measures electrochemical behavior of via many particles simultaneously without having to make electrical contacts to single particles on the TEM grid. This correlated optical-TEM approach can link particle structure with electrochemical behavior at the single particle-level. Our measurements revealed significant electrochemical activity heterogeneity among particles. Single particle activity correlated with distinct local mechanical or electrical properties of the amorphous carbon film of the TEM grid, leading to active and inactive particles. The results are significant for correlated electrochemical/TEM imaging studies that aim to reveal structure-property relationships using single particle-level imaging and ensemble-level electrochemistry.
Highlights
Nanoscale materials are attractive ion insertion hosts for applications such as electrochemical energy conversion and electrochromic smart windows (Bourderau et al, 1999; Li et al, 1999; Graetz et al, 2003; Arico et al, 2005; Manthiram et al, 2008)
Another major challenge is that the aforementioned single particle-level methods typically correlate electrochemical and composition/structure information using ex situ scanning electron microscopy (SEM)
We used bright field optical microscopy to measure the rate of Li-ion insertion in single WO3 nanorods
Summary
Nanoscale materials are attractive ion insertion hosts for applications such as electrochemical energy conversion and electrochromic smart windows (Bourderau et al, 1999; Li et al, 1999; Graetz et al, 2003; Arico et al, 2005; Manthiram et al, 2008). Understanding how variations among particles contribute to ion insertion dynamics is critical to the design and optimization of electrodes Toward this goal, single particle-level electrochemical methods have been applied to battery materials (Heubner et al, 2020). A major disadvantage of the ex situ approach is that it removes any possibility of correlating realtime electrochemical and structural dynamics Another major challenge is that the aforementioned single particle-level methods typically correlate electrochemical and composition/structure information using ex situ scanning electron microscopy (SEM). The limited spatial resolution of SEM imaging does not permit discovery of atomic scale structure–property relationships
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