In situ TEM observation of lithium nanoparticle growth and morphological cycling

Abstract

Lithium fluoride crystals were subjected to electron beam irradiation at 200 and 300 keV using transmission electron microscopy in order to study in situ fabrication of Li nanostructures. We observed that LiF crystals decompose in a unique way different to all other metal halides: Fluorine ablation and salt-to-metal conversion is non-local and due to a rapid lateral diffusion of Li, the life cycle from nucleation to annihilation of fresh Li nano-crystals can be observed at a distance from the Li-source, the irradiated salt. Growth, shape transition and annihilation of Li nanostructures follow at slow enough speed for live video recording with resolution of 25 frames per second. The equilibrium shapes of pure Li nano-crystals range from cubic to rod-shaped and ball-shaped and up to 300 nm size. By varying the e-beam flux of irradiation, transitions from cube to spherical shape can be induced cyclically.

Lithium Electrodeposition Dynamics in Aprotic Electrolyte Observed in Situ via Transmission Electron Microscopy

“…Thus, we presume that the beam-induced SEI may have consisted of components such as LiF that could be reduced back to metallic Li. 27,36 Based on these observations, we conclude that the electron beam induces reactive species in the electrolyte that can diffuse to a surface and deposit as a denser, darker material than the electrolyte. Due to the highly reducing Li metal environment, these species could be the same as those that form a natural SEI such as polymerized carbon chains but at an accelerated rate assisted by the electron beam.…”

Review—Promises and Challenges of In Situ Transmission Electron Microscopy Electrochemical Techniques in the Studies of Lithium Ion Batteries

“…199,200 Note that electron microscopy using electron beams caused a localized electrochemical reaction, resulting in Li salts (LiPF 6 ) to decompose into LiF, PF 5 , and Li more quickly, and finally accelerating lithiation processes. 124,200,201 Cheong, et al, proved that, when using GLC, the volume expansion of SnO 2 during cycling was inhibited at a low magnification ( Figure 5B), which is attributed to the fact that GLC leads to less lithiation. 124,202 Under higher resolution, agglomeration of decomposed electrolytes and diffusion of Li into SnO 2 are seen ( Figure 5C).…”

Zn nanodot patterning in borosilicate glasses by electron irradiation

“…This is similar to other reports of nanoparticle synthesis by in-situ TEM via migration of ablated atoms into a circular zone around the irradiated material on the carbon film where, after sufficient ''cooling'' outside the e-beam, the nuclei stop and ripen into nanoparticles. Although previously reported for noble-metal particles and halide salts 18,27 , this phenomenon is not known from oxide glasses. However, as our images reveal Zn particles aligned on the surface of the glass fragment under irradiation, it is possible that the migrated Zn stems from pre-precipitated particles.…”

“…Against this background ''direct write'' electron beam patterning of initially uniform glasses without a mask appears to be promising due to its greater flexibility and resolution. Outside the field of glasses, electron beam induced preparation of metal nanoparticles from their precursors has been demonstrated in a variety of materials [15][16][17][18] .…”