Highly efficient ion-transport "polymer-in-ceramic" electrolytes boost stable all-solid-state Li metal batteries.

"Polymer-in-ceramic" (PIC) electrolytes are widely investigated for all-solid-state batteries (ASSBs) due to their good thermal stability and mechanical performance. However, achieving fast and diversified lithium-ion transport inside the PIC electrolyte and uniform Li ⁺ deposition at the electrolyte/Li anode interface simultaneously remains a challenge. Besides, the effect of ceramic particle size on Li ⁺ transport and Li anodic compatibility is still unclear, which is essential for revealing the enhanced mechanism of the performance for PIC electrolytes. Herein, PIC with moderate ceramic size and contents are prepared and studied to strike a balance between ionic conductivity and anodic compatibility. Through moderate filler-filler interfacial impedance and appropriate surface roughness, a particle size of 17 μm is optimized to facilitate homogeneous Li ⁺ flux on anode and enhance Li ⁺ conductivity of the electrolyte. The PIC electrolyte with ceramic particle size of 17 μm achieves a high lithium ion transference number (0.74) and an ionic conductivity of 4.11 × 10 ^-4 S cm ^-1 at 60 °C. The Li/PIC/Li symmetric cell can stably cycle for 2800 h at 0.2 mA cm ^-2 with 0.2 mAh cm ^-2 . Additionally, the Li/PIC/LiFePO ₄ cell also delivers a superior cycling performance at 0.5C, a high capacity retention of 93.28% after 100 cycles and 83.17% after 200 cycles, respectively.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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