Phase transformation mechanism and stress evolution in Sn anode

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Diffusion-induced stresses in Sn, a promising anode material for Li-ion batteries owing to its high specific capacity, depend significantly on the phase transformation mechanism. In this study, an in-situ X-ray diffraction study is performed to reveal the phase transformation mechanism in Sn as functions of the discharge rate and Sn anode dimensions. In a 500 nm-thick Sn thin-film discharged at C/9 or a 100 nm-thick Sn thin-film discharged at 0.1 C, the Sn phase transforms sequentially to Li2Sn5, followed by β-LiSn and a-Li7Sn3 in three steps, where each step involves reaction-controlled lithiation. However, in a 500 nm-thick Sn thin-film discharged at 2 C or a 2 μm-thick Sn thin-film discharged at 0.1 C, the a-Li7Sn3 phase is directly formed via one-step reaction-controlled lithiation between Sn and a-Li7Sn3. A transition from three-step to one-step results in a steep gradient in the mismatch strain, thereby causing early failure. Finite element simulations show a lower J-integral for the three steps compared with that of a one-step reaction, thereby confirming previously reported experimental observations. For a specified transformation mechanism, the J-integral is lower for smaller Sn micropillars. Therefore, the mechanical reliability of the Sn anode can be enhanced significantly when lithiated under phase transformation mechanism involving three-reaction-controlled lithiations, as well as utilizing a small Sn anode measuring less than 200 nm.
Publisher
ELSEVIER
Issue Date
2022-03
Language
English
Article Type
Article
Citation

ENERGY STORAGE MATERIALS, v.45, pp.101 - 109

ISSN
2405-8297
DOI
10.1016/j.ensm.2021.11.034
URI
http://hdl.handle.net/10203/291472
Appears in Collection
MS-Journal Papers(저널논문)
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