Li-Rich and Halide-Deficient Argyrodite Fast Ion Conductors

Abstract

We report on a new family of halide-deficient and Li-rich argyrodite fast-ion conductors, Li6+x PS5+x (Cl/Br/I)1–x (0 ≤ x ≤ 0.85). Exploration of the influence of aliovalent anion substitution in Li6PS5X (X = Cl, Br, I)using a combination of high-resolution powder neutron diffraction and electrochemical impedance spectroscopyreveals that aliovalent anion substitution induces higher Li-ion concentration and Li site disorder, and creates S2–/I– anion site disorder on the 4a site. In the series Li6+x PS5+x I1–x (0 ≤ x ≤ 0.4), the resulting conductivity for Li6.4PS5.4I0.6 (0.13 mS·cm–1) represents almost a 100-fold increase over that of the parent phase, Li6PS5I (0.0033 mS·cm–1), and establishes one of the first fast-ion conducting argyrodite thiophosphate iodides. For Cl-argyrodites, the ionic conductivity decreases a little with lower halide-content but ionic conductivity for the Br-argyrodites is almost unchanged. Overall, all Cl/Br-argyrodites Li6+x PS5+x (Cl/Br)1–x (0 ≤ x ≤ 0.75) with a low halide content exhibit surprisingly high ionic conductivities > 1 mS·cm–1 despite a very low degree of sulfur/halogen anion site disorder. Our findings highlight the importance of attaining a disordered Li-ion sublattice and sulfur/halogen anion site disorder (anionic charge homogeneity) in argyrodites, where Li ions occupy high energy sites and activate concerted ion migration that drives the ionic conductivity.

Influence of synthesis and substitution on the structure and ionic transport properties of lithium rare earth metal halides

“…One approach to classify materials according to their activation energies is to look at their pre-exponential factors s 0 in the Arrhenius equation. [46][47][48] By plotting the respective s 0 of the different Li 3 MI 6 against their activation energies according to the Meyer-Neldel rule [49][50][51] (see Fig. S27 †), a Meyer-Neldel energy D 0 of around 20 meV is observed for these lithium rare earth iodides.…”

All-Solid-State Garnet Type Sulfurized Polyacrylonitrile/Lithium-Metal Battery Enabled by an Inorganic Lithium Conductive Salt and a Bilayer Electrolyte Architecture

“…To enable a fast charge transfer process in all-solid-state cells, a solid-state catholyte is necessary to enable Li + transport through the cathode structure, and moreover, it must provide a continuous Li + path from/to the cathode active material (CAM). A number of inorganic solid-state catholyte materials have been investigated including Li 2.3 C 0.7 B 0.3 O 3 (LCBO), Li 6 PS 5 Cl (LPS-Cl), Li 6 PS 5 Br (LPS-Br), and Li 6 PS 5 I (LPS-I). ,,− However, these were typically for co-sintering with oxide CAMs which enable a much higher sintering temperature than is possible for use with sulfur-based cathodes due to their limited thermal stability (e.g., S melts at 112.8 °C and has a high vapor pressure). For example, Wang et al .…”

“…(b) Experimentally measured ionic conductivity of LiFSI and the ionic conductivity of other solid-state catholytes reported in the literature. Ionic conductivity data for Li 2.3 C 0.7 B 0.3 O 3 (LCBO), Li 6 PS 5 Cl (LPS-Cl), Li 6 PS 5 Br (LPS-Br), and Li 6 PS 5 I (LPS-I) were extracted from the references. , (c) Electrochemical stability window of LiFSI obtained by cyclic voltammetry with a carbon-felt/LiFSI+NGW/bilayer-LLZO/Li-metal cell. The voltage range was 100 mV to 5 V with a scanning rate of 0.1 mV/s.…”

“…co-sintered a composite LiCoO 2 and LLZO cathode with LCBO at 700 °C, well above the thermal stability limit of sulfur-based cathodes. Similarly, the majority of halide argyrodite catholytes require a high stacking pressure (i.e., >100 MPa) to have good CAMs/solid-state-catholyte contact and provide good cell performance ,− which is not desirable for practical batteries and can be avoided using our novel bilayer/trilayer LLZO architectures. , …”

New perspectives on the multianion approach to adapt electrode materials for lithium and post-lithium batteries

“…Fig. 5 Structure of Li 6.4 PS 5.4 I 0.6 (space group F % 43m) 165. The tetrahedra PS 4Àx I x are shown.…”