Mechanism of Formation of Li₇P₃S₁₁ Solid Electrolytes through Liquid Phase Synthesis

Abstract

Crystalline Li7P3S11 is a promising solid electrolyte for all solid-state lithium/lithium ion batteries. A controllable liquid phase synthesis of Li7P3S11 is more desirable than conventional mechanochemical synthesis, but recent attempts suffer from reduced ionic conductivities. Here we elucidate the mechanism of formation of crystalline Li7P3S11 synthesized in the liquid phase [acetonitrile (ACN)]. We conclude that crystalline Li7P3S11 forms through a two-step reaction: (1) formation of solid Li3PS4·ACN and amorphous “Li2S·P2S5” phases in the liquid phase and (2) solid-state conversion of the two phases. The implication of this two-step reaction mechanism for morphology control and the transport properties of liquid phase synthesized Li7P3S11 is identified and discussed.

Solvent‐assisted ball milling for synthesizing solid electrolyte Li7P3S11

“…Step (1): The dissociation of coordinate bonds in the complex results in the release of coordinating solvent molecules and the formation of the thio‐LISICON III analogous phase; Step (2): The transition from the thio‐LISICON III analogous phase to Li 7 P 3 S 11 occurs. A recent study by Wang et al on liquid phase synthesis of Li 7 P 3 S 11 in ACN revealed the same evolution of the crystalline phase as this work. They also pointed out that besides the thio‐LISICON III analogous phase (they assigned as β‐Li 3 PS 4 ), the intermediate also contains an amorphous phase which is not detected by XRD.…”

Synthesis and Properties of NaSICON‐type LATP and LAGP Solid Electrolytes

“…Moreover,i norganic solid electrolytes are also beneficial for lithium-ion batteries and lithium-air batteries, in which they functiona se ither surface modification layers or lithium-ion conductors. [19][20][21] Sulfide solid electrolytes include Li 2 SÀP 2 S 5 , [22,23] Li 3 PS 4 , [24][25][26] Li 7 P 3 S 11 , [27,28] Li 7 PS 6 ,a nd Li 6 PS 5 X( X = Cl, Br). Suc-cessfule xamples in oxidesi nclude garnet oxides, [15,16] perovskite-type oxides, [17,18] and antiperovskite oxides.…”

“…Suc-cessfule xamples in oxidesi nclude garnet oxides, [15,16] perovskite-type oxides, [17,18] and antiperovskite oxides. [19][20][21] Sulfide solid electrolytes include Li 2 SÀP 2 S 5 , [22,23] Li 3 PS 4 , [24][25][26] Li 7 P 3 S 11 , [27,28] Li 7 PS 6 ,a nd Li 6 PS 5 X( X = Cl, Br). [29][30][31] Popular phosphate solid electrolytes include sodium superionic conductor (NaSICON)structured lithium-ion conductors, [32][33][34][35][36] such as LiTi 2 (PO 4 ) 3 (LTP), Li 1 + x Al x Ti 2Àx (PO 4 ) 3 (LATP), and Li 1 + x Al x Ge 2Àx (PO 4 ) 3 (LAGP).…”

Advances and Prospects of Sulfide All‐Solid‐State Lithium Batteries via One‐to‐One Comparison with Conventional Liquid Lithium Ion Batteries

“…Greater understanding of the formation mechanism of the liquid‐phase synthesized sulfide SEs is required. To identify this formation mechanism, Wang et al synthesized crystalline Li 7 P 3 S 11 through the reaction between acetonitrile (ACN) solvent and the precursor powders . They not only synthesized the crystalline Li 7 P 3 S 11 sulfide SE but also revealed the mechanism of formation of Li 7 P 3 S 11 through verification of the phase change and the dissolved phase ( Figure a,b).…”

“…c) Powder X‐ray diffraction (PXRD) pattern of samples with the various synthesizing temperature. d) Ionic conductivity plot for the total and intergrain of the crystalline Li 7 P 3 S 11 a–d) Reproduced with permission . Copyright 2018, American Chemical Society.…”