Electrochemical Properties of Interface-Modified Li-Metal All-Solid-State Batteries: Li/LLZTO/LVO Cell

Lithium (Li) metal all-solid-state batteries (ASSBs) were developed with a Li/LLZTO (Li₆.₄La₃Zr₁.₄Ta₀.₆O₁₂)/LVO (LiV₃O₈) configuration to enhance energy density and safety for electric vehicle applications. To overcome limitations in ionic conductivity and electrode-electrolyte interfacial resistance, we optimized: (1) Li metal anode, (2) anode/solid electrolyte interface, (3) LLZTO solid electrolyte, (4) cathode/solid electrolyte interface, and (5) nonlithiated LVO cathode. A composite anode of Li powder and poly(ethylene oxide) (PEO) suppressed dendrite growth and improved contact, achieving electrochemical stability for 700 h (vs 246 h for Li foil). A LLZTO/PEO composite electrolyte delivered high ionic conductivity (5 × 10^-4 S cm^-1 at 40 °C). The cathode, coated with poly(3,4-ethylenedioxythiophene) (PEDOT) via vapor-phase polymerization (VPP), combined with PEO and LLZTO, reduced interfacial resistance from 280 to 180 Ω, as confirmed by electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) verified uniform PEDOT coating, while X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy confirmed structural integrity. The Li powder/PEO|LLZTO/PEO|PEDOT-LVO/PEO battery achieved 219.8 mAh g^-1 with 97% capacity retention and >99% Coulombic efficiency over 100 cycles at 0.1C, demonstrating superior performance for scalable ASSBs.