Aging Property of Halide Solid Electrolyte at the Cathode Interface

Abstract

Halide solid electrolytes have recently emerged as a promising option for cathode‐compatible catholytes in solid‐state batteries (SSBs), owing to their superior oxidation stability at high voltage and their interfacial stability. However, their day‐ to month‐scale aging at the cathode interface has remained unexplored until now, while its elucidation is indispensable for practical deployment. Herein, the stability of halide solid electrolytes (e.g., Li3InCl6) when used with conventional layered oxide cathodes during extended calendar aging is investigated. It is found that, contrary to their well‐known oxidation stability, halide solid electrolytes can be vulnerable to reductive side reactions with oxide cathodes (e.g., LiNi0.8Co0.1Mn0.1O2) in the long term. More importantly, the calendar aging at a low state of charge or as‐fabricated state causes more significant degradation than at a high state of charge, in contrast to typical lithium‐ion batteries, which are more susceptible to high‐state‐of‐charge calendar aging. This unique characteristic of halide‐based SSBs is related to the reduction propensity of metal ions in halide solid electrolytes and correlated to the formation of an interphase due to the reductive decomposition triggered by the oxide cathode in a lithiated state. This understanding of the long‐term aging properties provides new guidelines for the development of cathode‐compatible halide solid electrolytes.

A Full Oxide-Based Solid-State Lithium Battery and Its Unexpected Cathode Degradation Mechanism

“…The robust cycle attributes of these oxide ASSBs enabled us to explore what intrinsically causes capacity fading of cathode composites in ASSBs, an area where previous studies have been lacking. While earlier research conducted on sulfide- and halide-based ASSB has suggested that the cathode degradation primarily arises from the deterioration of the interface between CAM and solid electrolyte due to repeated volume change of CAM during cycle, − we discover that residual stress on CAM unexpectedly plays a critical role in the cathode degradation in oxide-based ASSBs. It is proposed that the cosintering of two oxides results in significant thermal mismatch during cooling, and this residual stress exacerbates the mechanical degradation of both the interface and CAM itself during the electrochemical cycles.…”

Bridging the gap between academic research and industrial development in advanced all-solid-state lithium–sulfur batteries

“…This feature enables their compatibility with cathode materials like LiCoO 2 (LCO) and high-nickel NCM without necessitating surface protective coatings, a challenge commonly encountered with sulfides. 91 However, a significant limitation of halide electrolytes pertains to their inadequate reductive stability, resulting in a restricted electrochemical stability range of 0.5–3 V. 92,93 The insufficient stability at the anode necessitates the incorporation of at least one supplementary solid electrolyte partner when interfacing with lithium metal, 94 thereby presenting a subsequent challenge due to the disparity in solid electrolyte compatibility. 95 Similar to sulfide electrolytes, halide electrolytes are also susceptible to humidity-related issues.…”

Halide Superionic Conductors for All-Solid-State Batteries: Effects of Synthesis and Composition on Lithium-Ion Conductivity

“…Some reactivity between them was previously reported. 27 , 28 However, due to the challenges in the characterization of buried interphases, it remains unclear what reaction products are produced and how they can affect the cycling stability. Further studies in this area are required.…”

“…We believe this is mostly due to the interactions between the halide SE and the cathode active materials and the resulting reaction products. Some reactivity between them was previously reported. , However, due to the challenges in the characterization of buried interphases, it remains unclear what reaction products are produced and how they can affect the cycling stability. Further studies in this area are required.…”

“…In the Li 3 MX 6 family, Li 3 YCl 6 (LYC) and its derivatives (hereafter termed Li–Y–Cl) have shown outstanding chemical/electrochemical stabilities and good compatibility with NMC-type cathodes. − While SS-synthesized LYC typically has low conductivities (∼0.02 mS cm –1 ), highly conducting LYC (∼0.4 mS cm –1 ) can be made by MC synthesis. The latter often adopts a disordered trigonal lattice with various defects, which evolves into a more crystalline and ordered structure upon heat treatment.…”