Solid electrolytes (SEs) are vital for all-solid-state batteries (ASSBs) since they replace the flammable liquid electrolytes to make the ASSBs safer and compacter.¹ In order to boost the energy density of ASSBs, a practical SE is not only expected possessing high ionic conductivity, but also good compatibility with both cathode and anode to allow the use of high-voltage cathode and Li metal.^{2, 3} However, most of the developed SEs show limitations on directly contact with either high-voltage cathode materials or Li metal. As such, SE modification is required to address the interfacial issues between SE and electrodes.

In this work, fluorinated sulfide- and halide-based SEs are proposed to stabilize the SE/Li metal and SE/high-voltage cathode interfaces, respectively. Our results firstly show that fluorinated argyrodite Li₆PS₅Cl (LPSCl) can enhance the interfacial stability toward the Li metal anode.⁴ The in-situ formed interface between Li and LPSCl_1−xF_x are of highly fluorinated and condense, which enables ultrastable Li plating/stripping behavior over 250 hrs at a high current density of 6.37 mA cm⁻² and a cutoff capacity of 5 mAh cm⁻². The Li metal treated by the LPSCl_1−xF_x SE is then demonstrated to deliver good durability and rate capability in full cells. Other than anode side improvement, F is introduced into a superionic conductor Li₃InCl₆ to widen the oxidation limit to over 6 V (vs. Li/Li⁺).⁵ Both experimental and computational results identify that F-containing passivating interphases are generated to contribute to the enhanced oxidation stability of Li₃InCl_6-xF_x and stabilization the surface of cathodes at high cut-off voltages. The optimized composition Li₃InCl_4.8F_1.2 is directly matched with bare high-voltage LiCoO₂, enabling ASSBs to stably operate at room temperature at a cut-off voltage of 4.8 V (vs Li/Li⁺). Our studies provide a new strategy of interface engineering by introducing F in SEs, realizing the good compatibility between SE and electrodes and opening up the applications of ASSBs.

References

1. Manthiram, A., Yu, X. W., Wang, S. F. Lithium battery chemistries enabled by solid-state electrolytes. Nat. Rev. Mater. 2, 1-16 (2017).
2. Wang, C. H., Liang, J. W., Zhao, Y., Zheng, M. T., Li, X. N., Sun, X. L. All-solid-state lithium batteries enabled by sulfide electrolytes: from fundamental research to practical engineering design. Energy Environ. Sci. 14, 2577-2619 (2021).
3. Li, J. C., Ma, C., Chi, M. F., Liang, C. D., Dudney, N. J. Solid Electrolyte: the Key for High-Voltage Lithium Batteries. Adv. Energy Mater. 5, 1401408 (2015).
4. Zhao, F. P., et al. Ultrastable Anode Interface Achieved by Fluorinating Electrolytes for All-Solid-State Li Metal Batteries. ACS Energy Lett. 5, 1035-1043 (2020).
5. Zhang, S. M., et al. Advanced High-Voltage All-Solid-State Li-Ion Batteries Enabled by a Dual-Halogen Solid Electrolyte. Adv. Energy Mater. 11, 2100836 (2021).