Despite progress in solid-state battery engineering, our understanding of the chemo-mechanical phenomena that govern electrochemical behavior and stability at solid-solid interfaces remains limited compared to solid-liquid interfaces. Here, we use operando synchrotron X-ray computed microtomography to investigate the evolution of lithium/solid-state electrolyte interfaces during battery cycling, revealing how the complex interplay between void formation, interphase growth, and volumetric changes determines cell behavior. Void formation during lithium stripping is directly visualized in symmetric cells, and the loss of contact at the interface between lithium and the solid-state electrolyte (Li 10 SnP 2 S 12) is found to be the primary cause of cell failure. Reductive interphase formation within the solid-state electrolyte is simultaneously observed, and image segmentation reveals that the interphase is redox-active upon charge. At the cell level, we postulate that global volume changes and loss of stack pressure occur due to partial molar volume mismatches at either electrode. These results provide new insight into how chemo-mechanical phenomena can impact cell performance, which is necessary to understand for the development of solid-state batteries. File list (2) download file view on ChemRxiv Manuscript Updated.pdf (1.08 MiB) download file view on ChemRxiv Supplementary Information.pdf (1.02 MiB)

We describe a hybrid photocatalytic system for hydrogen production consisting of nanocrystalline CdSe/CdS dot-in-rod (DIR) structures coupled to [NiFe] soluble hydrogenase I (SHI) from Pyrococcus furiosus.

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Although solid-state batteries with lithium metal could enable higher energy density and better safety characteristics than Li-ion batteries, the complex electro-chemo-mechanical evolution of the Li− solid-state electrolyte interface can diminish performance. Here, we measure the stack pressure in real time to provide new insights into the effects of applied stack pressure and electrolyte processing on the interfacial behavior of two representative solid-state electrolytes, Li 10 SnP 2 S 12 and Li 6 PS 5 Cl; these materials exhibit different degradation mechanisms through either interphase formation or Li filament growth. We find that stack pressure evolution sensitively depends on interphase formation and that tracking stack pressure coupled with impedance can distinguish between various reaction phenomena and degradation mechanisms within cells. Furthermore, Li filament growth exhibits distinct stack pressure signatures that depend on electrolyte density. The findings advance our understanding of the interfacial evolution of two important classes of solid-state electrolytes, and they demonstrate the utility of electro-chemomechanical measurements to understand solid-state battery behavior.

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Solid-state batteries (SSBs) with lithium metal anodes offer higher specific energy than conventional lithium-ion batteries, but they must utilize areal capacities >3 mAh cm -2 and cycle at current densities >3 mA cm -2 to achieve commercial viability. Substantial research effort has focused on increasing rate capabilities of SSBs by mitigating detrimental processes such as lithium filament penetration. Less attention has been paid to understanding how areal capacity impacts plating/stripping behavior, despite the importance of areal capacity for achieving high specific energy. Here, we investigate and quantify the relationships among areal capacity, current density, and plating/stripping stability using both symmetric and full-cell configurations with a sulfide solid-state electrolyte (Li6PS5Cl). We show that unstable deposition and short circuiting readily occur at rates much lower than the measured critical current density when a sufficient areal capacity is passed. A systematic study of continuous plating under different electrochemical conditions reveals average "threshold capacity" values at different current densities, beyond which short circuiting occurs. Cycling cells below this threshold capacity significantly enhances cell lifetime, enabling stable symmetric cell cycling at 2.2 mA cm -2 without short circuiting. Finally, we show that full cells also exhibit threshold capacity behavior, but they tend to short circuit at lower current densities and areal capacities. Our results quantify the effects of transferred capacity and demonstrate the importance of using realistic areal capacities in experiments to develop viable solid-state batteries.

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Anode-free" solid-state batteries (SSBs), which have no active material at the anode and undergo in situ lithium plating during the first charge, can exhibit extremely high energy density (~1500 Wh L -1 ). However, there is a lack of understanding of lithium plating/stripping mechanisms at bare solid-state electrolyte (SSE) interfaces since excess lithium is often used. Here, we demonstrate that commercially relevant quantities of lithium (> 5 mAh cm -2 ) can be reliably plated at relatively high current densities (1 mA cm -2 ) using the sulfide SSE Li6PS5Cl. Investigations of lithium plating/stripping mechanisms, in conjunction with cryo-focused ion beam (FIB) and ex situ synchrotron tomography, reveal that the cycling stability of these cells is intrinsically limited by spatially uneven plating/stripping. Local lithium depletion toward the end of stripping decreases electrochemically active area, which results in high local current densities and void formation, accelerating subsequent filament growth and short circuiting compared to lithium-excess cells.Despite this governing degradation mode, we show that anode-free cells exhibit comparable Coulombic efficiencies to lithium-excess cells before short circuiting, and improved resistance to short-circuiting is achieved by avoiding local lithium depletion through retention of lithium at the interface. These new insights provide a foundation for engineering future high-energy anode-free SSBs.