Y-Doped LiZr2(PO4)3 in a PVDF-HFP Composite Electrolyte for Solid-State Li-Metal Batteries

Due to their improved electrochemical behavior, ceramic/polymer solid composite electrolytes (CEs) are the front-runners for application in all-solid-state lithium cells. In this work, a NASICON-type Li1.2Y0.2Zr1.8(PO4)3 (Y-LZP) ceramic powder was prepared by using the solid-state synthesis route. Rietveld refinement of X-ray diffraction (XRD) data showed that Y-LZP exhibited a single rhombohedral phase (R3̅c space group) and a grain conductivity of ∼5.31 × 10–5 S cm–1 at room temperature. Further, the Y-LZP ceramic powder was incorporated in a PVDF-HFP/LiTFSI polymer electrolyte to fabricate free-standing, flexible CE membranes of thickness ∼60 μm. The CE with 15% inorganic filler (CE15) showed the highest conductivity of ∼5.78 × 10–5 S cm–1 at room temperature with an activation energy of ∼0.43 eV. A galvanostatic lithium plating–stripping test was performed on the symmetric Li|CE15|Li cell at a current density of 0.1 mA cm–2, and the sample demonstrated a lithium plating–stripping stability over 400 h. Linear sweep voltammetry measurements on the symmetric cell confirmed the electrochemical stability of the composite electrolyte to be up to ∼4.67 V. The electrochemical behavior of an all-solid-state cell fabricated using the LiMn2O4 cathode and the CE15 electrolyte is also reported.