Elastic Strain Effects on Li-Ion Conductivity in LiPON Solid Electrolyte

The solid-state lithium-ion batteries holds a promising future for high energy density applications. In last decade, there have been lot of progress in development of fast lithium solid ion conductors. However, the stress generated at the solid-state interfaces dues to (un)desirable (electro)chemical reactions can lead to build of large local stresses, which could go as high as 10s of GPa. [1] The electro-chemo-mechano coupling to the performance of these batteries is an emerging field enabling us to elucidate the strain effects. The mechanical strain coupling of oxygen ion transport is relatively widely known in solid oxide fuel cells (SOFCs) community, where 4 % elastic strain is could change ionic conductivity by ~4 orders of magnitude. [2] On the other hand, it is relatively new for solid Li-ion conductors with a few earlier studies. [3], [4], [5], [6], [7] In this study, we introduce a custom 3-point bending to apply elastic strain on model systems and simultaneously characterize using electrochemical techniques. We studied model lithium phosphorous oxynitride (LiPON) solid electrolyte for strain effects on Li-ion conductivity. Our data shows that the conductivity of LiPON enhances ~15 % with only ~0.4 % tensile strain. This is remarkable because, given the elastic constant of LiPON of ~77 GPa [8], and interfaces in solid state cells could experience local tensile stresses as of the order of &gt;3 GPa [1], this means that strain of even &gt;4% becomes relevant for LiPON. With addition of the fact that for typical ion conductors’ ionic conductivity could experience an exponential dependence on the strain [9], we could expect much larger local Li-ion conductivity modulation at the interfaces of all solid-state batteries utilizing LiPON as solid electrolyte.<br/><br/><i>Acknowledgements: </i>The work is supported by the Mechano-Chemical Understanding of Solid Ion Conductors, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, contact DE-SC0023438. This work was carried out in part through the use of MIT.nano's facilities. We would also like to acknowledge Yen-Ting Chi and Andrew I Ryan for helpful feedback for designing the experiment platform.<br/><br/>References<br/>[1] H.-K. Tian, A. Chakraborty, A. A. Talin, P. Eisenlohr, and Y. Qi, <i>J Electrochem Soc</i>, vol. 167, no. 9, p. 090541, May 2020.<br/>[2] B. Yildiz, <i>MRS Bull</i>, vol. 39, no. 2, pp. 147–156, Feb. 2014.<br/>[3] Y. Inaguma, J. Yu, Y. Shan, M. Itoh, and T. Nakamuraa, <i>J Electrochem Soc</i>, vol. 142, no. 1, pp. L8–L11, Jan. 1995.<br/>[4] J. Glenneberg, I. Bardenhagen, F. Langer, M. Busse, and R. Kun, <i>J Power Sources</i>, vol. 359, pp. 157–165, Aug. 2017.<br/>[5] V. Faka <i>et al.</i>, <i>J Am Chem Soc</i>, vol. 146, no. 2, pp. 1710–1721, Jan. 2024<br/>[6] C. Lin, L. Zhang, and Y. Dong, <i>Journal of Physics and Chemistry of Solids</i>, vol. 187, p. 111775, Apr. 2024.<br/>[7] K. Thai and E. Lee, <i>J Electrochem Soc</i>, vol. 164, no. 4, pp. A594–A599, Jan. 2017, doi: 10.1149/2.0661704JES/XML.<br/>[8] E. G. Herbert, W. E. Tenhaeff, N. J. Dudney, and G. M. Pharr, <i>Thin Solid Films</i>, vol. 520, no. 1, pp. 413–418, Oct. 2011.<br/>[9] C. Korte, J. Keppner, A. Peters, N. Schichtel, H. Aydin, and J. Janek, <i>Physical Chemistry Chemical Physics</i>, vol. 16, no. 44, pp. 24575–24591, Oct. 2014.