Lithium Thiophosphate Glasses and Glass–Ceramics as Solid Electrolytes: Processing, Microstructure, and Properties

Abstract

Lithium solid electrolytes are of major interest for solid‐state batteries and electrochemical capacitors (ECs). Currently, the material selection space of liquid electrolytes is dominated by lithium salts paired with organics. Improved safety, as well as the need for higher temperature and high voltage operation, opens up opportunities for glass and ceramic alternatives in these important solid‐state energy storage technologies. Lithium thiophosphates in the family x Li2S + (1−x) P2S5 (mol fraction) possess room temperature ionic conductivities greater than 10−3(Ω‐cm)‐1 in crystallized x = 0.70 (almost the highest in inorganic solid‐state electrolytes). Within this review article, we address recent progress made in this class of material. We consider the role of densification on the Li‐ion conductivity, as well as our recent data on the effect of densification on the electrochemical properties of the system. We cover the processing techniques of mechanical milling and pressure‐forming, discuss microstructure, bulk versus surface conduction, and device integration. The systematic improvement in ionic conductivity with increased density suggests that bulk conduction dominates surface conduction and demonstrates that dense, rather than porous, lithium thiophosphate solid electrolytes are important in the design of solid‐state batteries and ECs.

Ultra‐thin Solid‐State Li‐Ion Electrolyte Membrane Facilitated by a Self‐Healing Polymer Matrix

“…This value closely matches with what others have reported for similar near full-dense variations. [ 17 ] Theoretical densities of polyimine materials were measured by pressing polyimine powders into translucent fi lms using the method outlined previously.…”

“…This method takes advantage of the fact that the solid electrolyte pellet is about 15% porous in the green body state. [ 17 ] By fi lling empty voids with an organic polymer, we can create a crosslinked polymer matrix in situ to provide mechanical robustness while preserving lithium-ion transport pathways in between solid electrolyte particles. Using a newly derived malleable thermoset polymer paired with an Li 2 S-P 2 S 5 inorganic electrolyte, we produce a stand-alone membrane of 64 µm in thickness, high inorganic material loading (80%), and near theoretical density.…”

Recent progress in sulfide-based solid electrolytes for Li-ion batteries

“…Several approaches such as ball milling process, pulsed laser deposition (PLD) technique, etc. have been explored as effective routes [25,26,60,61]. The electrode/solid electrolyte interface formation and solid-state battery fabrication, however, are not discussed here since they are beyond the topic of this review.…”

“…Moreover, Anantharamulu et al [22] summarized the comprehensive information of NASICON-type compositions; the recent developments in garnet solid electrolytes were reviewed by Teng et al [23]; meanwhile, Thangadurai et al [24] also compared the garnet-type solid-state Li-ion conductors for lithium batteries; the development of sulfide solid electrolytes was reported from the viewpoint of processing and fabrication of all-solid-state lithium batteries by Berbano et al [25] and Tatsumisago et al [26], respectively. In present work, we review the recent progress of the sulfidebased solid electrolytes for lithium batteries.…”

“…But unlike ref. [25] and [26], we mainly focus on the sulfide-based solid electrolytes from a structural point of view. Especially, the structural developments of Li 2 S-P 2 S 5 glass and glass-ceramic are firstly reviewed.…”