Halogen‐Rich Lithium Argyrodite Solid‐State Electrolytes: A Review

Abstract

Exploring solid electrolytes (SEs) with high ionic conductivity, excellent chemical/electrochemical stability, and excellent compatibility with electrodes is important for promoting the development of all-solid-state batteries (ASSBs). Halogen-rich lithium argyrodite electrolytes have received a lot of attention recently due to their ultrahigh room-temperature lithium-ion conductivity and relatively low cost. In this review, the properties of the halogen-rich argyrodite electrolytes are presented in terms of their crystal structure, ionic conduction mechanism, and compatibilities with oxide cathode and Li-metal anode. Secondly, the preparation process of SE film and the performances of ASSBs based on this electrolyte are summarized. Finally, the challenges and the next research directions of the electrolytes are proposed. Halogen-rich lithium argyrodite electrolytes are one of the promising sulfide electrolytes, the collation of this paper can provide us with a better understanding of the current development status of this type of electrolyte and advance their further development.Lithium argyrodite electrolytes Li 6 PS 5 X (X = Cl, Br, I) with cubic crystal structures (F43m), which are composed of PS 4 3À tetrahedra. [46][47][48][49][50] The S 2À and X À anions are disordered on the 4a and 4d (4c) sites in the lattice, while the Li + ion sites form cagelike polyhedra around them. The results of molecular dynamics [a] Dr.

High‐Entropy Lithium Argyrodite Solid Electrolytes Enabling Stable All‐Solid‐State Batteries

“…Recently, such halogen-rich, lithium-deficient argyrodites (e.g., Li 5.5 PS 4.5 Cl 1.5 ) are attracting interest, as they not only possess a high ionic conductivity but also show a better (electro)chemical stability than the parent Li 6 PS 5 Cl. [28][29][30][31][32][33][34] It has also been shown that a second halogen can be introduced, and with that, the conductivity further improves. [35][36][37] From a structural perspective, it has been recognized that anion disorder induced by halogen mixing and varying the halogen content can have a profound effect on ionic conductivity.…”

“…To shed light on this, we prepared a series of (dualsubstituted) halogen-rich lithium argyrodite samples with a total halogen content of 1.5 moles and systematically varied the Cl À to Br À ratio in Li 5.5 PS 4.5 Cl x Br 1.5-x (with x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 and 1.5). Their crystal structure was probed using a combination of neutron powder diffraction (NPD) and 31 P magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, indicating that a maximum anion-disordered sublattice is achieved with Li 5.5 PS 4.5 Cl 0.8 Br 0.7 . Using complementary electrochemical impedance spectroscopy (EIS) and 7 Li pulsed field gradient (PFG) NMR measurements, it is shown that this particular material also possesses the highest ionic conductivity among all prepared samples.…”

Fast and stable charge transfer at the lithium–sulfide (electrolyte) interface via an in situ solidified Li+-conductive interlayer

“…6,7 Solid-state electrolytes, such as oxide electrolytes (OEs) and sulfide electrolytes (SEs), have a high Li transfer number (t Li+ E 1) and sufficient mechanical strength (G SEs 4 2G Li ) for resisting Li dendrite growth, which make them widely accepted as promising candidates to avoid these hazards. [8][9][10][11][12][13] Compared with OEs, SEs possess higher ionic conductivity (10 À2 À 10 À3 S cm À1 ), which is comparable to that of liquid electrolytes (LEs), due to the lower electronegativity and higher ionic radius of sulfur than those of oxygen. 14,15 Moreover, the ductility of SEs is better than that of OEs, which is beneficial to alleviate the stress and strain in batteries.…”

“…6,7 Solid-state electrolytes, such as oxide electrolytes (OEs) and sulfide electrolytes (SEs), have a high Li transfer number ( t Li+ ≈ 1) and sufficient mechanical strength (G SEs > 2G Li ) for resisting Li dendrite growth, which make them widely accepted as promising candidates to avoid these hazards. 8–13…”

High‐Entropy Lithium Argyrodite Solid Electrolytes Enabling Stable All‐Solid‐State Batteries

“…Another approach to boost ionic conductivity in lithium argyrodites is the substitution of sulfur with a halogen (Cl − or Br − ), leading to an increase in Li vacancies and more pronounced S 2− /X − site disorder. Recently, such halogen‐rich, lithium‐deficient argyrodites (e.g., Li 5.5 PS 4.5 Cl 1.5 ) are attracting interest, as they not only possess a high ionic conductivity but also show a better (electro)chemical stability than the parent Li 6 PS 5 Cl [28–34] . It has also been shown that a second halogen can be introduced, and with that, the conductivity further improves [35–37] .…”