Li + -conductive ceramic oxide electrolytes, such as garnetstructured Li 7 La 3 Zr 2 O 12, have been considered as promising candidates for realizing the next-generation solid-state Li-metal batteries with high energy density. Practically, the ceramic pellets sintered at elevated temperatures are often provided with high stiffness yet low fracture toughness, making them too brittle for the manufacture of thin-film electrolytes and straininvolved operation of solid-state batteries. The ceramic powder, though provided with ductility, does not yield satisfactorily high Li + conductivity due to poor ion conduction at the boundaries of ceramic particles. Here we show, with solid-state nuclear magnetic resonance, that a uniform conjugated polymer nanocoating formed on the surface of ceramic oxide particles builds pathways for Li + conduction between adjacent particles in the unsintered ceramics. A tapecasted thin-film electrolyte (thickness: <10 μm), prepared from the polymer-coated ceramic particles, exhibits sufficient ionic conductivity, a high Li + transference number, and a broad electrochemical window to enable stable cycling of symmetric Li/Li cells and all-solid-state rechargeable Li-metal cells.
Single-crystalline
Ni-rich cathodes with high capacity have drawn
much attention for mitigating cycling and safety crisis of their polycrystalline
analogues. However, planar gliding and intragranular cracking tend
to occur in single crystals with cycling, which undermine cathode
integrity and therefore cause capacity degradation. Herein, we intensively
investigate the origin and evolution of the gliding phenomenon in
single-crystalline Ni-rich cathodes. Discrete or continuous gliding
forms are revealed with new surface exposure including the gliding
plane (003) and reconstructed (−108) under surface energy drive.
It is also demonstrated that the gliding process is the in-plane migration
of transition metal ions, and reducing oxygen vacancies will increase
the migration energy barrier by which gliding and microcracking can
be restrained. The designed cathode with less oxygen deficiency exhibits
outstanding cycling performance with an 80.8% capacity retention after
1000 cycles in pouch cells. Our findings provide an insight into the
relationship between defect control and chemomechanical properties
of single-crystalline Ni-rich cathodes.
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