Transformations
at interfaces between solid-state electrolytes
(SSEs) and lithium metal electrodes can lead to high impedance and
capacity decay during cycling of solid-state batteries, but the links
between structural/chemical/mechanical evolution of interfaces and
electrochemistry are not well understood. Here, we use in situ X-ray
computed tomography to reveal the evolution of mechanical damage within
a Li1+x
Al
x
Ge2–x
(PO4)3 (LAGP) SSE caused by interphase growth during electrochemical cycling.
The growth of an interphase with expanded volume drives fracture in
this material, and the extent of fracture during cycling is found
to be the primary factor causing the impedance increase, as opposed
to the resistance of the interphase itself. Cracks are observed to
initiate near the edge of the lithium/LAGP interface, which agrees
with simulations. The chemomechanical effects of interphase growth
studied here are expected to play a role in a variety of SSE materials,
and this work is a step toward designing durable interfaces.
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)
<p>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 <i>operando</i> 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<sub>10</sub>SnP<sub>2</sub>S<sub>12</sub>) 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.</p>
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