The use of inorganic solid-state electrolytes is considered a viable strategy for developing high-energy Li-based metal batteries. However, suppression of parasitic interfacial reactions and growth of unfavorable Li metal depositions upon cycling are challenging aspects and not yet fully addressed. Here, to better understand these phenomena, we investigate various sulfide inorganic solid electrolytes (SEs), i.e., Li7−xPS6−xClx (x = 0.6, 1.0, 1.3, 1.45, and 1.6), via ex situ and in situ physicochemical and electrochemical measurements. We found that the Cl distribution and the cooling process applied during the SE synthesis strongly influence the evolution of the Li|SE interface in terms of microstructure, interphase composition, and morphology. Indeed, for a SE with a moderate chlorine content (i.e., x = 1.3) and obtained via a slow cooling process after sintering, the Cl atoms are located on the surface of the SE grains as interconnected LiCl nanoparticles that form an extended LiCl-based framework. This peculiar microstructure facilitates the migration of the Cl ions to the Li|SE interface during electrochemical cycling, thus, favouring the formation of a LiCl-rich interphase layer capable of improving the battery cycling performances.

Solid/solid interface is the major challenge for high‐performance solid‐state batteries. Solid electrolytes (SEs) play a crucial role in the fabrication of effective interfaces in solid‐state batteries. Herein, the electrolyte distribution with varied particle sizes is tuned to construct solid‐state batteries with excellent performance at different operating temperatures. Solid‐state batteries with the configuration S/L (small‐sized SE in composite cathode and large‐sized SE in electrolyte layer) show the best performance at room temperature (168 mA h g−1 at 0.2 C, retention of 99%, 100 cycles) and −20 °C (89 mA h g−1 at 0.05 C), while the configuration S/S displays better performance at elevated temperature. The superior performance of S/L battery is associated with faster lithium‐ion dynamics due to the better solid/solid interface between active materials and electrolytes. Moreover, the inferior performance at 60 °C is caused by the formation of voids and cracks in the electrolyte layer during cycling. In contrast, the S/S battery delivers superior performance at elevated operating temperature because of the integrated structure. This work confirms that tailoring electrolyte size has significant effect on fabricating all‐climate solid‐state batteries.

promising applications in energy storage devices meet the multiplying demands regarding high energy densities and safety concerns. [1] As a key part of ASSLBs, the SEs possess merits including decent thermal properties, mechanical strengths, and electrochemical stability windows; high Li transference numbers; and stable ion transports. [2] Among diverse SEs, sulfides show high ionic conductivity comparable to the commercial liquid electrolytes at room temperature, and good deformability favorable for battery assembling, [3] which are prime candidates for practical applications. [4] Nonetheless, sulfide SEs are electrochemically incompatible with metallic Li, which generates electronic conductive interphases. [5] This not only promotes the interfacial reaction of Li/sulfide causing a large interface resistance but also accelerates the Li-dendrites growth, leading to a rapid deterioration of battery performance and finally short circuits. [6] Despite the progress achieved, how to suppress Li dendrites in SEs to date is still a major issue to hinder the practical applications of lithium metal anode. Yet, no significant breakthrough has been achieved. ASSLBs using sulfide SEs and Li metal anode can only work for a few hundred cycles (<300 cycles) at room temperature, even at relatively small current densities (<0.3 mA cm −2 ), while the long-life batteries always use Li composite anodes such as Li-In, [7] Li-C, [8] and Ag-C. [4a] However, considering the high theoretical capacity (3860 mAh/g) and low electrochemical potential (−3.04 V vs SHE), Li metal remains the ultimate choice for Li batteries. [9] Moreover, a Li metal anode is important for developing next-generation Li-S batteries, [10] along with the sulfide SEs to restrain the polysulfide dissolution. It is thus significant to improve the electrochemical stability of sulfide SEs to Li. Many efforts based on external routes have been made so far to successfully mitigate the reactivity of Li/sulfide-SEs, including Li alloying (e.g., In-Li), surface decorations, construction of artificial interfaces, and incorporation of organic/ionic-liquid buffer layers. [6a,11] Combined with these external routes, if the sulfides themselves can be optimized via the intrinsic routes, for example, doping, phase transition, and microstructural modification, the interfacial stability of Li/sulfide is expected to be effectively enhanced.Compared with other sulfide-based SEs, Li-argyrodites Li 7-a PS 6-a X a (X = Cl, Br, I) as an important family member of sulfide-based SEs not only possess a low cost and high ionic A stable interface and preventing dendrite-growth are two crucial factors to realize long-life all-solid-state Li batteries (ASSLBs) using sulfide-based solid electrolytes (SEs) and Li metal anodes. But it remains a challenge to accomplish the two factors simultaneously. Here, an effective strategy is reported to realize this goal in Li-argyrodites via self-engineered metastable decomposition that is enabled by Si doping in Cl-rich argyrodites. It is shown that Cl...

A viscous feature is beneficial for a solid electrolyte with respect to assembling solid-state batteries, which can change the solid-solid contacts from point to face. Here, novel halide-based deep eutectic solid electrolytes (DESEs) prepared by a facile ball milling method is reported. The mixture of halides triggers the deep eutectic phenomena by intermolecular interactions, leading to diverse morphologies and viscous statuses in terms of composition. Chemical-and micro-structure analyses via the cryogenic technique reveal that the LiCl and LiF nanoparticles are dispersed in an amorphous halide matrix, which endow freely mobile ions for fast ion transport. The optimized DESE thus achieves low activation energy and high ionic conductivity of 16 mS cm −1 at room temperature, one of the highest values among various electrolytes so far. By integrating with the active materials to form a composite cathode, the viscous DESE yields a super-dense composite pellet which possesses intensively enhanced ionic conductivity in contrast to those formed by the sulfide-based electrolyte additives, demonstrating an attractive application prospect.

The severe parasitic interface reaction and dendrite growth retard the practical applications of all‐solid‐state (ASS) Na batteries with sulfide solid electrolytes (SEs). Here, a novel composite SE is proposed, with a high ionic conductivity, composed of Na3SbS4 (NSS) and oxysulfide glass. The study reveals that the P2S7‐aOa and PS4‐aOa units in oxysulfide play various roles: The former is deoxidized to release free O ions, which reacts with the anode via migrating to form oxides, favoring an improved interface stability. The latter is highly stable upon cycling, thereby maintaining an ion transport network. Meanwhile, NSS acts as a dendrite predator via reacting with penetrated Na. These advantages enable the resulting ASS Na battery with superior long‐term cycling performance at a high current density at room temperature, one of the best results so far. This discovery sheds light on innovative advanced SE materials through an oxysulfide‐based composite design.