Fast Ag-Ion-Conducting GeS₂–Sb₂S₃–AgI Glassy Electrolytes with Exceptionally Low Activation Energy

Abstract

Silver-ion-sconducting solid electrolytes with low activation energy are important because of their distinctive application potential in solid-state batteries operated within a broad temperature range, especially below room temperature. Achieving glassy solid electrolytes with high ionic conductivity, low activation energy, and good thermal stability is a continuous challenge for the design and synthesis of novel fast ion-conducting glasses. Here, we report markedly low activation energy and high room-temperature ionic conductivity in melt-quenched GeS2–Sb2S3–AgI chalcogenide glasses. Homogeneous 2.5GeS2–27.5Sb2S3–70AgI glass presenting high glass transition temperature of 135 °C shows high ionic conductivity of 9.18 × 10–3 S/cm at 25 °C and low activation energy of 0.07 eV, which is the lowest among those of Ag-ion glassy electrolytes. Structural characterization by using Raman spectra suggests that, in the disordered network structure of GeS2–Sb2S3–AgI glasses, the formation of chain fragments composed by [SbS3–x I x ] n , which is similar to the double chain of [(SbSI)∞]2 in the SbSI crystal structure, provides possible diffusion pathways to facilitate low-barrier concerted migration of silver ions.

Effect of heat treatment on AgI‐rich chalcogenide glasses with enhanced ionic conductivity

“…Second, increase in the amount of precipitated AgI crystals, especially the superionic conductor α‐AgI phase, partly improves ionic conductivity at prolonged heat‐treatment time. In fact, the formed structure of SbSI units in a network can present a ribbon framework and forms an effective ionic transport channel for Ag + ions benefiting for the raise of the ionic conductivity . Similar structure units were constructed in the present work, as indicated by the Raman results, for the transport of the Ag + ions.…”

“…The first was the increased amplitude of 107 cm −1 and decreased amplitude of the shoulder peak at 138 cm −1 . According to many research studies, the shoulder peak around 107 cm −1 is corresponding to [SbSI] and β‐AgI, and that at 138 cm −1 corresponds to [SbI 3 ] unit. The crystallization of AgI decreased I − concentration in the glass matrix and converted the [SbI 3 ] structural units to [SbSI].…”

“…This approach improves the thermo‐mechanical properties, particularly thermal expansion, thermal shock sensitivity, and resistance to crack propagation of chalcogenide glasses . Notably, microcrystals of AgI contained chalcogenide glass‐ceramic have become a focus research because of their potential application in solid‐state batteries, in which Ag + ions exhibit high ionic conductivity exceeding 10 −3 S/cm at room temperature. Superionic conductor α‐AgI has a high ionic conductivity of 1 S/cm when it is thermodynamically stable above 147°C.…”

Structural Origins of the Enhancement in Ionic Conductivity of a Chalcogenide Compound by Adding AgI

“…Compared to the liquid electrolytes currently used in commercial batteries, solid electrolytes have obtained extensive attention mainly due to their highly applicable perspectives in stability (non‐volatility), safety (non‐explosiveness) and device fabrication (easy shaping, patterning, and integration) . As one kind of important solid‐state electrolytes, Ag‐based ionic conductors achieved several important breakthroughs in recent years about the improvement of room temperature ionic conductivity . In addition, based on the silver fast ionic conductor, the prototypes of all‐solid‐state batteries were also reported .…”

Physical and electrochemical behaviors of AgX (X = S/I) in a GeS2–Sb2S3 chalcogenide-glass matrix

“…electrolytes are isotropic, possess grain-free boundaries, can be conveniently processed into various shapes, and have higher ionic conductivity and wider electrochemical window than their oxide counterparts [4,5]. In contrast to traditional liquid electrolytes, solid electrolytes are environment-friendly materials devoid of safety issues, such as liquid leakage, fire hazards and explosion risk.…”