Re-investigating the structure–property relationship of the solid electrolytes Li _3−xIn_1−xZr_xCl₆ and the impact of In–Zr(iv) substitution

Abstract

Chloride based solid electrolytes are considered interesting candidates for catholytes in all solid state batteries due to their high electrochemical stability, which allows the use of high voltage cathodes without...

Halide solid-state electrolytes for all-solid-state batteries: structural design, synthesis, environmental stability, interface optimization and challenges

“…100 Replacing In 3+ with different amounts of Zr 4+ or Hf 4+ in Li 3 InCl 6 could still maintain a monoclinic structure. 88,[106][107][108][109] In Li 3−x In 1−x Zr x Cl 6 , the Zr 4+ only occupied the 2b site (Fig. 9a) and the occupancy of In at the 4g site gradually decreased with the Zr content increasing.…”

“…It was noteworthy that the occupancy of tetrahedral Li3 (8j) sites almost linearly decreased with the increase in Zr content, until complete disappearance. 106,107 Li 3 InCl 6 had two possible Li + diffusion pathways: one was along the c -direction, involving the octahedral 2c site, tetrahedral 8j site, and shared octahedral 4g site. The other was along the Li-layer in the ab -plane, involving both the octahedral Li-sites in the layer and the vacant tetrahedra.…”

“…Tetravalent Zr 4+ and Hf 4+ were usually doped into trivalent metal halides as aliovalent ions. 39,44,88,97,[106][107][108] The introduction of Zr 4+ into Li 3 YCl 6 and Li 3 ErCl 6 by a solid-state reaction at 450 °C resulted in crystal structure changes. 44 As Zr content increased, their crystal structure changed from the trigonal structure, rst to an orthorhombic-I structure and then to an orthorhombic-II structure (Fig.…”

Halide Superionic Conductors for All-Solid-State Batteries: Effects of Synthesis and Composition on Lithium-Ion Conductivity

“…All-solid-state batteries (ASSBs) featuring a lithium metal anode and an inorganic solid electrolyte (SE) have attracted tremendous attention due to their high energy densities and improved safety compared to conventional lithium-ion batteries (LIBs) using liquid electrolytes. − Among various SE candidates, newly emerged halide superionic conductors with a general formula of Li 3 MX 6 (M = Sc, Y, In, Er, Yb; X = Cl, Br) are strong contenders due to their excellent stability at high voltages, enabling the use of 4 V-class cathodes such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) without a protective coating. − However, the ionic conductivities of halide SEs synthesized from the standard solid-state (SS) method are relatively low (<1 mS cm –1 ) compared to other SEs such as sulfides, limiting their application in high-performing ASSBs. To achieve higher ionic conductivities, chemical substitution or mechanochemical (MC) synthesis are often adopted. − For halides, substituting trivalent metal cations with tetravalent cations such as Zr 4+ and Hf 4+ is widely used, − which reduces Li stoichiometry and gives rise to higher ionic conductivities. This is in contrast to the well-known strategy used in inorganic SEs such as LISICON, NASICON, or garnets, where high-valent metal cations are usually replaced by lower-valent ions to increase the Li + content in composition and consequently ionic conductivity. − Furthermore, halide SEs synthesized using the MC method are known to have higher ionic conductivity than their counterparts made by the SS method, yet it remains unclear what contributes to these differences. − …”

Li3–xZrx(Ho/Lu)1–xCl6 Solid Electrolytes Enable Ultrahigh-Loading Solid-State Batteries with a Prelithiated Si Anode

“…However, they also display a low oxidation potential of ∼2.5 V vs Li + /Li. , Currently they are suitable as a solid electrolyte combined with a low-voltage cathode such as S/Li 2 S, , or as a catholyte with a coated high-voltage LiNi 1– x – y Co x Mn y O 2 (NCM)-type cathode. Lithium metal chloride solid electrolytes, on the other hand, are appealing for use in high-voltage cathode composites due to their intrinsic chemical and electrochemical stability with uncoated NCM cathodes. − A number of Li-M-Cl materials have been reported with Li ion conductivities between 0.5 and 2 mS cm –1 , including Li 3 YCl 6 , Li 3 InCl 6 , Li 3 Y 1– x In x Cl 6 , Li x ScCl 3+ x , Li 3– x (Zr/Hf) x (Y/Er/Yb/In)­Cl 6 , − Li 2 (Sc/In) 2/3 Cl 4 , , Li 2 ZrCl 6 , − Li 3–3 x M 1+ x Cl 6 (M = Tb, Dy, Ho, Y, Er, Tm), and Li 0.5 SmCl 3.5 . The recently reported Li­(Ta/Nb)­Cl 5 X (X = F, Cl, O, OH) family exhibits an even higher ionic conductivity of >10 mS cm –1 , , while Li 0.388 Ta 0.238 La 0.475 Cl 3 is reported to form a stable interphase with Li metal and stable cycling of Li symmetrical cells at high current density .…”