(Invited) In Situ TEM Nano Electrochemistry

Abstract

Since the inception of the 1st open cell nanobattery study, significant progress has been made in the field of in situ nano electrochemistry. Many new techniques are emerging, which include combining transmission electron microscopy ― scanning probe microscopy (TEM-SPM) with environmental TEM (ETEM) to enable metal ― gas battery studies; combining TEM-SPM with microelectromechanical system (MEMS) heating devices to enable high temperature battery studies; using large diameter carbon nanotuble as an electrochemical reaction cell to enable in situ liquid cell studies. Our latest results on Li/Na-O2/CO2 batteries, Li/Na-S/Se batteries as well as quantitative measurements of the mechanical properties of Li and Na dendrites will be highlighted [1]. Fig. 1 shows an example of measuring the mechanical property of lithium whiskers. Progress on the in situ studies of solid state batteries will also be presented. Liqiang Zhang, Yongfu Tang, Jianyu Huang et al., Science 330, (2010) 1515; Nature Nano 15, (2020) 94; ACS Nano 14, (2020) 13232; Nano Lett. 18, (2018) 3723; Eng. Env. Sci. 4 (2011) 3844; 14(2021) 602; Adv. Mater. 1900608, 2019; ACS Energy Lett. 5, (2020) 2546; Materials Today 42, (2021) 137. Fig. 1 In-situ ETEM-AFM characterization of stress generation during Li dendrite growth. (a) Schematic of the ETEM-AFM setup used for imaging and measurement of Li dendrite growth. An arc-discharged CNT was attached to a conducting AFM, and this assembly was used as cathode; the scratched Li metal on the top of a sharp tungsten needle was used as anode, and the naturally formed Li2O on the Li surface as a solid electrolyte. (b) A TEM image showing an AFM cantilever was approaching the counter electrode of Li metal. (c) A TEM image showing a CNT was attached to a flattened AFM tip. (d) Time-lapse TEM images of the Li dendrite growth. A nano-sized Li ball nucleated from the CNT, Li2O and gas triple point (1863 s). As the Li ball grew to about 1.26 μm in size, the dendrite emerged underneath the ball (2028 s) which pushed the AFM cantilever up. When the dendrite reached 4.08 mm in length, it collapsed (2177 s) due to the axial compression by the AFM tip. The blue dotted line indicates a fixed reference position, and the red arrow indicates the upward displacement of the AFM tip. Figure 1