(603b) Solution Processing of Solid Electrolytes for Solid-State Lithium Batteries

Solid-state lithium batteries are attracting considerable attention for the next generation of energy storage. Judicious selection of solid electrolytes could enable the use of lithium metal anodes and by combining a thin solid electrolyte layer with a thick cathode, high energy densities can be achieved. Furthermore, by replacing a flammable liquid electrolyte with a solid electrolyte, the safety of the battery can, in principle, be enhanced. Significant progress has been made in identifying promising solid electrolyte materials for lithium batteries, including a variety of metal halides (Li₃InCl₆, Li₃YCl₆, etc.) and metal sulfides (Li₃PS₄, Li₆PS₅Cl, etc.).^1,2 However, integrating these solid electrolytes into a battery architecture often relies on the pressing of solid powders, limiting their use to relatively thick layers (frequently hundreds of microns in thickness).

This work is developing solution deposition methods for solid-state electrolytes to enable high-energy-density batteries. Solution processing methods are widely tunable and can be used with a broad range of materials.^3,4 By adjusting coating parameters, thin films from the nanometer to micron scale can be fabricated. Furthermore, solution-based methods are compatible with deposition on structured electrodes as solvent can infiltrate to produce a conformal coating. Improving control over solid electrolyte deposition could also enable more complex device architectures with multi-layer electrolytes where each layer plays a distinct role in the battery. However, careful consideration needs to be given to the solution chemistry to produce high-quality solid electrolyte materials and ensure compatibility with the rest of the system.

This work shows how solution deposition methods, such as the coating of a fully dissolved molecular precursor ink, can open new opportunities for high-energy-density solid-state batteries. We start by using dense electrodeposited LiCoO₂ cathodes free from inactive additives.⁵ Subsequently, we develop solution deposition approaches for promising solid electrolytes, such as Li₃InCl₆, focusing on tuning the chemistry to produce material with high ionic conductivity and to enable compatibility with the LiCoO₂. With this platform, we then explore how solution processing can enable creative architectures in the pursuit of high-energy-density batteries.

(1) Wang, C.; Liang, J.; Kim, J. T.; Sun, X. Prospects of Halide-Based All-Solid-State Batteries: From Material Design to Practical Application. Sci. Adv 2022, 8, 9516. https://doi.org/10.1126/sciadv.adc9516.

(2) Wang, C.; Liang, J.; Zhao, Y.; Zheng, M.; Li, X.; Sun, X. All-Solid-State Lithium Batteries Enabled by Sulfide Electrolytes: From Fundamental Research to Practical Engineering Design. Energy Environ. Sci. 2021, 14, 2577. https://doi.org/10.1039/d1ee00551k.

(3) Turnley, J. W.; Catherine Vincent, K.; Pradhan, A. A.; Panicker, I.; Swope, R.; Uible, M. C.; Bart, S. C.; Agrawal, R. Solution Deposition for Chalcogenide Perovskites: A Low-Temperature Route to BaMS₃ Materials (M = Ti, Zr, Hf). J. Am. Chem. Soc. 2022, 144 (40), 18234–18239. https://doi.org/10.1021/jacs.2c06985.

(4) Turnley, J. W.; Deshmukh, S. D.; Boulos, V. M.; Spilker, R.; Breckner, C. J.; Ng, K.; Kuan, J.; Liu, Y.; Miller, J. T.; Kenttämaa, H. I.; et al. A Selenium-Based “Alkahest”: Reactive Dissolutions of Metals and Metal Compounds with n-Alkylammonium Polyselenide Solutions. Inorg. Chem. Front 2023, 10, 6032–6044. https://doi.org/10.1039/d3qi01632c.

(5) Zahiri, B.; Patra, A.; Kiggins, C.; Xiao Bin Yong, A.; Ertekin, E.; Cook, J. B.; Braun, P. V. Revealing the Role of the Cathode-Electrolyte Interface on Solid-State Batteries. Nat. Mater. 2021, 20, 1392–1400. https://doi.org/10.1038/s41563-021-01016-0.