Strain dependent Li-ion conductivity modulation in model amorphous LiPON glassy-type solid electrolyte

Subhash Chandra^a, Bilge Yildiz^a^,^b

^aDepartment of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States

^bDepartment of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States

Proceedings of 24th International Conference on Solid State Ionics (SSI24)

Fundamentals: Experiment and simulation

London, United Kingdom, 2024 July 14th - 19th

Organizers: John Kilner and Stephen Skinner

Poster, Subhash Chandra, 605
Publication date: 10th April 2024

All solid-state chemistry is considered as the next generation Li-ion battery technology promising significant enhancement in energy and power densities. However, it faces challenges of interfacial instability and relatively lower ionic conductivity of solid electrolyte, which has hindered the realization of promising benefits of this technology. Unlike the liquid electrolytes, which can accommodate large magnitudes of strain arising from reversible Li (de)intercalation of active material, interfaces in solid state batteries faces electrochemical induced stresses. Additionally, undesirable reactions at the interfaces which necessitates volume change could also potentially induces stresses. The magnitudes of these stresses could go as high as 10s of GPa. [1] These stresses, hence the induced lattice strain can be thought to be a factor in controlling local Li-ion mobility. The mechanical coupling of ion transport is relatively widely known in solid oxide fuel cells (SOFCs) community pertaining to oxygen ion conductors, where 4 % strain is known to induce conductivity change by almost 4 orders of magnitude. [2] However, 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 setup to characterize the strain dependent electrochemical impedance spectroscopy with model lithium phosphorous oxynitride (LiPON) solid electrolyte. This approach allows us to separate the strain effects and quantify the Li-ion conductivity dependency on strain. The study shows that the conductivity of LiPON enhances by up to ~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 >3 GPa [1], this means that strain of even >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.

References:

[1] H.-K. Tian, A. Chakraborty, A. A. Talin, P. Eisenlohr, and Y. Qi, “Evaluation of The Electrochemo-Mechanically Induced Stress in All-Solid-State Li-Ion Batteries,” J Electrochem Soc, vol. 167, no. 9, p. 090541, May 2020

[2] B. Yildiz, “‘Stretching’ the energy landscape of oxides—Effects on electrocatalysis and diffusion,” MRS Bull, vol. 39, no. 2, pp. 147–156, Feb. 2014

[3] Y. Inaguma, J. Yu, Y. Shan, M. Itoh, and T. Nakamuraa, “The Effect of the Hydrostatic Pressure on the Ionic Conductivity in a Perovskite Lanthanum Lithium Titanate,” J Electrochem Soc, vol. 142, no. 1, pp. L8–L11, Jan. 1995

[4] J. Glenneberg, I. Bardenhagen, F. Langer, M. Busse, and R. Kun, “Time resolved impedance spectroscopy analysis of lithium phosphorous oxynitride - LiPON layers under mechanical stress,” J Power Sources, vol. 359, pp. 157–165, Aug. 2017

[5] V. Faka et al., “Pressure-Induced Dislocations and Their Influence on Ionic Transport in Li+-Conducting Argyrodites,” J Am Chem Soc, vol. 146, no. 2, pp. 1710–1721, Jan. 2024

[6] C. Lin, L. Zhang, and Y. Dong, “Strain effects on Li3OXX=Cl,Br anti-perovskite solid lithium-ion electrolytes: DFT study,” Journal of Physics and Chemistry of Solids, vol. 187, p. 111775, Apr. 2024

[7] K. Thai and E. Lee, “Effects of Mechanical Strain on Ionic Conductivity in the Interface between LiPON and Ni-Mn Spinel,” J Electrochem Soc, vol. 164, no. 4, pp. A594–A599, Jan. 2017

[8] E. G. Herbert, W. E. Tenhaeff, N. J. Dudney, and G. M. Pharr, “Mechanical characterization of LiPON films using nanoindentation,” Thin Solid Films, vol. 520, no. 1, pp. 413–418, Oct. 2011

[9] C. Korte, J. Keppner, A. Peters, N. Schichtel, H. Aydin, and J. Janek, “Coherency strain and its effect on ionic conductivity and diffusion in solid electrolytes – an improved model for nanocrystalline thin films and a review of experimental data,” Physical Chemistry Chemical Physics, vol. 16, no. 44, pp. 24575–24591, Oct. 2014

Acknowledgements:

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.

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