Use of a Be-dome holder for texture and strain characterization of Li metal thin films via sin²(ψ) methodology

Abstract

Residual strain in electrodeposited Li films may affect safety and performance in Li metal battery anodes, so it is important to understand how to detect residual strain in electrodeposited Li and the conditions under which it arises. To explore this Li films, electrodeposited onto Cu metal substrates, were prepared under an applied pressure of either 10 or 1000 kPa and subsequently tested for the presence or absence of residual strain via sin2(ψ) analysis. X-ray diffraction (XRD) analysis of Li films required preparation and examination within an inert environment; hence, a Be-dome sample holder was employed during XRD characterization. Results show that the Li film grown under 1000 kPa displayed a detectable presence of in-plane compressive strain (−0.066%), whereas the Li film grown under 10 kPa displayed no detectable in-plane strain. The underlying Cu substrate revealed an in-plane residual strain near zero. Texture analysis via pole figure determination was also performed for both Li and Cu and revealed a mild fiber texture for Li metal and a strong bi-axial texture of the Cu substrate. Experimental details concerning sample preparation, alignment, and analysis of the particularly air-sensitive Li films have also been detailed. This work shows that Li metal exhibits residual strain when electrodeposited under compressive stress and that XRD can be used to quantify that strain.

Effects of Applied Interfacial Pressure on Li-Metal Cycling Performance and Morphology in 4 M LiFSI in DME

“…There are several mechanisms by which applied interfacial pressure may improve Li cycling. Soft metal deposits are physically constrained through interfacial pressure, which can lead to denser deposits. ,, Pressure may improve Coulombic efficiency (CE) by increasing the probability of reconnecting disconnected or “dead” Li, , modifying how the SEI forms, maintaining a constant elastic stress on Li to affect growth, and causing residual strain in Li metal that may affect how cycling and SEI evolution proceed. − Finally, a mechanical overpotential is associated with depositing Li in regions of high interfacial stress because mechanical work must be performed to displace the compressed interface; this mechanical overpotential provides an incentive for minimizing the work under high pressure by formation of dense deposits to minimize interfacial displacement …”

Cryogenic electron microscopy reveals that applied pressure promotes short circuits in Li batteries

“…Therefore, the mechanical overpotential discourages continued growth at asperities and smooths out morphology ( Zhang et al., 2019 ). Finally, applied pressure may also affect Li material properties by inducing creep ( Zhang et al., 2020 ) and residual strain ( Rodriguez et al., 2020 ; Campbell et al., 2018 ; Lu et al., 2018 ; Kushima et al., 2017 ; Cho et al., 2020 ; Herbert et al., 2018 ) or by influencing SEI reactions ( Harrison et al., 2017 ).…”

Texture and strain analysis of tungsten films via Tilt-A-Whirl methodology

“…To verify the proper alignment of the instrument, a LaB 6 standard (NIST 660) was scanned to determine if there was any variation in peak location with ψ angle for an effectively zero-strain powder XRD standard. As in previous work, the LaB 6 (311) peak at ~75.8° 2 θ was employed (see Rodriguez et al , 2020). The strain for the powder was determined to be −0.00019 or −0.019(5)% based on the slope of the sin 2 ( ψ ) plot (i.e.…”

“…−0.019 ± 0.005%). The strain error value of ±0.005% was based on the fit and deviation of the straight line to the observed Δ d / d o values (Rodriguez et al , 2020). The measured strain is very close to zero and confirms suitable alignment of the diffractometer for residual strain measurements.…”