A Novel Strategy to Overcome the Hurdle for Commercial All‐Solid‐State Batteries via Low‐Cost Synthesis of Sulfide Solid Electrolytes

Abstract

Unlike commercial lithium‐ion batteries, the high cost and low ionic conductivity of solid electrolytes (SEs) continues to be a big hurdle in commercially available all‐solid‐state batteries (ASSBs). Rather than the conventional dry‐process and high‐energy ball milling processes, the productive solution synthesis of bulk‐type SEs is the most crucial issue in the successful application of high‐energy‐density ASSBs. In this study, the way is paved to overcome the hurdle for commercial lithium phosphorus sulfide chloride (LPSCl) SEs via a readily processable bulk‐type solution‐based synthesis without acquiring any high‐energy ball‐milling processes. By incorporating an elemental sulfur additive during the preparation process, Li2S and S form a polysulfide, and P2S5 is induced to react readily to provide LPSCl with excellent ion conductivity as high as 1.8 mS cm−1. Surprisingly, the purity of bulk type precursors does not affect the final composition and ionic conductivity of sulfide electrolytes, which show the same electrochemical characteristics of ASSB cells with a high discharge capacity of 185.6 mA h g−1. The study offers a promising strategy for saving the production cost of sulfide SEs, possibly up to 92%, and their commercial ASSBs are expected to be achieving a competitive cost per energy density of ≈0.46 $ W−1.

A Low-Cost Liquid-Phase Method of Synthesizing High-Performance Li6PS5Cl Solid-Electrolyte

“…After removing ethanol via distillation, the collected lc-Li 6 PS 5 Cl powder was then calcined under argon to obtain hc-Li 6 PS 5 Cl. The popular color of the Li 6 PS 5 Cl solution reported in the literature was brown, , which was also observed if we used a different brand of P 2 S 5 . The reasons are under investigation and to be reported in the future.…”

“…Finally, we conducted a comprehensive comparison between our method and literature methods for making Li 6 PS 5 Cl solid electrolytes (Figure ). ,− ,− ,,,,− The ionic conductivity of Li 6 PS 5 Cl electrolytes made via solid-phase methods scattered in the range of 1–10 mS/cm, where the higher values seemed mainly from hot-pressing or fast-sintering treatments during the pellet fabrications. , The liquid-phase methods could also make Li 6 PS 5 Cl electrolytes with the ionic conductivity around 2 mS/cm, ,,, including ours herein (Figure a). Regarding the cyclability, our electrolyte presented the second best performance with 400 cycles at 1 C, leaving far behind the third best with 250 cycles at 1 / 10 C and all others below 100 cycles (Figure b).…”

“…In the solid-state strategy, typically, Li 2 S, P 2 S 5 , and LiCl powders at the appropriate molar ratio are ball-milled together to first collect a low-crystallinity Li 6 PS 5 Cl (lc-Li 6 PS 5 Cl) and then calcined to obtain the electrolyte powder of high-crystallinity Li 6 PS 5 Cl (hc-Li 6 PS 5 Cl). − While the solid-state strategy generally produces Li 6 PS 5 Cl electrolytes with higher ionic conductivity, it will be energy-intensive and difficult to scale up for massive production, if it has to start with premade/commercial Li 2 S because such a raw material is troublesome in many aspects (such as high cost and difficulties in purification, transportation, storage, and operation) . The liquid-phase strategy, which is suitable for large-scale fabrication, usually consists of two steps: , (1) Li 2 S reacts with P 2 S 5 in a aprotic organic solvent (such as tetrahydrofuran, acetonitrile, or N -methylformamide) to make Li 3 PS 4 , eq ; (2) Li 3 PS 4 reacts with Li 2 S and LiCl in ethanol to produce lc-Li 6 PS 5 Cl precipitate after removing the solvent, , Equation . A subsequent calcination at 550 °C for 5–10 h produces hc-Li 6 PS 5 Cl. …”

Green synthesis of the battery material lithium sulfide via metathetic reactions

“…The trace amount of LiCl residual, although desired to be fully removed for applications of Li 2 S cathodes in lithium–sulfur batteries, seemed not a problem for making Cl-containing SSEs ( vide infra ), because LiCl is a key raw material therein. 16 To compensate for the inability of SEM to observe individual nanocrystals, 17 a transition electron microscope (TEM) was employed to analyze a carbon-protected Li 2 S product. The bright field image (Fig.…”

One-Dimensional Porous Li-Confinable Hosts for High-Rate and Stable Li-Metal Batteries

“…Metallic lithium (Li) has attracted increasing attention as a promising next-generation anode material owing to its attractive properties, such as high theoretical capacity (3860 mAh g –1 ) and low operating potential (−3.04 V vs standard hydrogen electrode). − However, poor Coulombic efficiency (CE) and catastrophic safety issues, mainly originating from the undesirable dendritic Li growth, have impeded its practical applications. To overcome these inherent shortcomings, considerable efforts have been devoted to realizing Li anodes in Li-metal batteries, including the development of three-dimensional (3D) conductive hosts, − functional electrolytes, − protection layers, − and solid electrolytes. − Among them, the 3D structures consisting of Cu nanowires or carbon materials such as graphite, graphene, and carbon nanotubes can reduce the effective current density and store metallic Li in the inner space of the host; the Li dendrite growth and drastic volume expansion during cycling can be largely mitigated in the 3D Li host. ,,, However, despite these advantages, internal short circuits can take place by the preferential Li deposition on the top surface of the structure (i.e., top plating) due to its conductive nature, eventually hindering the use of the bottom region of the host as Li storage space.…”