In Situ Transmission Electron Microscopy Observation of Pulverization of Aluminum Nanowires and Evolution of the Thin Surface Al₂O₃ Layers during Lithiation–Delithiation Cycles

Abstract

Lithiation-delithiation cycles of individual aluminum nanowires (NWs) with naturally oxidized Al(2)O(3) surface layers (thickness 4-5 nm) were conducted in situ in a transmission electron microscope. Surprisingly, the lithiation was always initiated from the surface Al(2)O(3) layer, forming a stable Li-Al-O glass tube with a thickness of about 6-10 nm wrapping around the NW core. After lithiation of the surface Al(2)O(3) layer, lithiation of the inner Al core took place, which converted the single crystal Al to a polycrystalline LiAl alloy, with a volume expansion of about 100%. The Li-Al-O glass tube survived the 100% volume expansion, by enlarging through elastic and plastic deformation, acting as a solid electrolyte with exceptional mechanical robustness and ion conduction. Voids were formed in the Al NWs during the initial delithiation step and grew continuously with each subsequent delithiation, leading to pulverization of the Al NWs to isolated nanoparticles confined inside the Li-Al-O tube. There was a corresponding loss of capacity with each delithiation step when arrays of NWs were galvonostatically cycled. The results provide important insight into the degradation mechanism of lithium-alloy electrodes and into recent reports about the performance improvement of lithium ion batteries by atomic layer deposition of Al(2)O(3) onto the active materials or electrodes.

Lithium Concentration Dependent Elastic Properties of Battery Electrode Materials from First Principles Calculations

“…The mechanical deformation mechanisms in alloyed electrodes are qualitatively different from intercalation compounds not only because of the enormous strains but also due to some distinct z E-mail: yueqi@egr.msu.edu phase transformations that occur, such as in crystalline Si, 17 Sn, 18 and Al. 19 Based on in-situ experiments and modeling, the phase boundary can limit the lithiation rate and impact the crack propagation and void formation, making failure modeling substantially more challenging. Nevertheless, each of these models is based on equations of solidstate diffusion and continuum mechanics.…”

In situ methods for Li-ion battery research: A review of recent developments

“…A good example of new insight in situ TEM can provide is the study of Liu et al [51] on aluminum nanowires and their native oxide layers. It shows that upon cycling, prior to the metal core, the metal oxide layer (Al 2 O 3 ) is lithiated first, turning into a LieAleO glass.…”

Aluminum-based materials for advanced battery systems

“…Sometimes, the small diameter of Al NWs can strengthen mechanical robustness effectively. Besides, the ion diffusion pathways are shortened in NWs, improving the rate capabilities [185]. Benson et al [186] demonstrated that patterned Al NWs were successfully deposited onto Cu, Ni, and SS substrates by decomposing trimethylamine alane complex at low pressure.…”