Robust Li₆PS₅I Interlayer to Stabilize the Tailored Electrolyte Li_9.95SnP₂S_11.95F_0.05/Li Metal Interface

Abstract

All-solid-state lithium-metal batteries (ASSLMBs) with sulfide electrolytes have attracted attention owing to their superior safety and high energy density. However, interfacial instability of sulfide electrolytes against Li metal still hinders their applications. Herein, F-doping is adopted to optimize the structure of Li10SnP2S12. It is demonstrated that the Li9.95SnP2S11.95F0.05 (LSPSF) electrolyte exhibits a high ionic conductivity of 6.4 mS cm–1 because of F-doping, which can reduce the impurity Li2SnS3 and generate Li+ vacancies. In addition, the Li6PS5I (LPSI) glass–ceramic interlayer is employed to enhance the interfacial stability between the sulfide electrolyte and Li metal by restraining the reduction of Sn4+ cations, as indicated by X-ray photoelectron spectroscopy (XPS). As a result, the assembled ASSLMBs with the LPSI interlayer deliver high initial discharge capacity and remarkable cycling stability. This work provides a new design route for manufacturing high-performance ASSLMBs.

Recent progress of sulfide electrolytes for all-solid-state lithium batteries

“…To further improve the ionic conductivity of a sulfide electrolyte, the resulting ball-milled materials were annealed. A series of sulfide electrolytes has been developed via mechanical milling plus annealing, including 70Li 2 S-30P 2 S 5 (mol%, 3.2 × 10 -3 S cm -1 ) [29] , 75Li 2 S-25P 2 S 5 (mol%, 5 × 10 -4 S cm -1 ) [30] , 80Li 2 S-20P 2 S 5 (mol%, 7.2 × 10 -4 cm -1 ) [31] , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 (2.5 × 10 -2 S cm -1 ) [10] , Li 10 SnP 2 S 12 (3.8 × 10 -3 S cm -1 ) [32] and Li 5.5 PS 4.5 Cl 1.5 (1.2 × 10 -2 S cm -1 ) [33] . Recently, Liu et al [34] synthesized a Li 5.6 PS 4.6 I 1.4 glass-ceramic electrolyte using an ultimate-energy mechanical alloying method.…”

“…For instance, at x < 70 mol%, the formation of Li 2 P 2 S 6 or Li 4 P 2 S 6 phases with low ionic conductivity decreases the overall conductivity of the glass ceramic [71,72] . However, for x ≥ 70 mol%, the crystalline phases of Li 3.25 P 0.95 S 4 and Li 7 P 3 S 11 with high ionic conductivity precipitate in the glass materials and significantly increase the ionic conductivity [29,31,73] . Very recently, a high-energy ball-milling method was utilized to produce glass-ceramic electrolytes in a one-pot process.…”

“…Even with the same stoichiometry, the electrochemical and mechanical properties of sulfides can be different. Therefore, a considerable selection for sulfides with satisfactory electrochemical and mechanical properties would benefit 6 Li, (B) 31 P and (C) 119 Sn MAS NMR spectra of Li 10 SnP 2 S 12 powder with different treatments. (D) Decomposition mechanism of Li 10 SnP 2 S 12 powder after ball-milling.…”

“…Solid-state NMR results of Li 10 SnP 2 S 12 before and after treatment. (A)6 Li, (B)31 P and (C)119 Sn MAS NMR spectra of Li 10 SnP 2 S 12 powder with different treatments. (D) Decomposition mechanism of Li 10 SnP 2 S 12 powder after ball-milling.…”

Cl-Doped Li10SnP2S12 with Enhanced Ionic Conductivity and Lower Li-Ion Migration Barrier

“…According to the components of solid electrolytes, they can be roughly classified into inorganic solid electrolytes, polymer solid electrolytes, and composite solid electrolytes. Sulfide solid electrolytes (SSEs), as a kind of inorganic electrolytes, are one of the most promising solid electrolytes with higher ionic conductivity, lower grain boundary resistance, and good mechanical ductility …”