Abstract
Alkali metals are widely studied in various fields such as medicine and battery. However, limited by the chemical reactivity and electron/ion beam sensitivity, the intrinsic atomic structure of alkali metals and its fundamental properties are difficult to be revealed. Here, a simple and versatile method is proposed to form the alkali metals in situ inside the transmission electron microscope. Taking alkali salts as the starting materials and electron beam as the trigger, alkali metals can be obtained directly. With this method, atomic resolution imaging of lithium and sodium metal is achieved at room temperature, and the growth of alkali metals is visualized at atomic-scale with millisecond temporal resolution. Furthermore, our observations unravel the ambiguities in lithium metal growth on garnet-type solid electrolytes for lithium-metal batteries. Finally, our method enables a direct study of physical contact property of lithium metal as well as its surface passivation oxide layer, which may contribute to better understanding of lithium dendrite and solid electrolyte interphase issues in lithium ion batteries.
Highlights
Alkali metals are widely studied in various fields such as medicine and battery
Atomic-scale imaging of cryo-transferred lithium has been reported at low temperature[7,8], and room temperature imaging is achieved by intercalating lithium into graphene sheets[9], whereas a direct room temperature atomic resolution imaging of bare alkali metals has never been demonstrated
The reaction rate is carefully controlled by tuning the beam intensity so that the reaction process is slow enough to be captured by the detector, and atomic resolution imaging of both lithium and sodium is demonstrated at room temperature
Summary
Alkali metals are widely studied in various fields such as medicine and battery. limited by the chemical reactivity and electron/ion beam sensitivity, the intrinsic atomic structure of alkali metals and its fundamental properties are difficult to be revealed. To understand the formation sequence of alkali metals and their oxides, the growth of particles was traced at high spatiotemporal resolution[18]. Combining low dose AC-HRTEM imaging with in situ fast camera detection, an example of lithium-particle growth is demonstrated at atomic resolution with fast frame rate (40 ms per frame).
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