Advanced Garnet-Polymer Hybrid Electrolytes for Enhanced Lithium Metal Battery Performance

Abstract

Traditional lithium-ion batteries (LIBs) with liquid electrolytes offer high ionic conductivity (~10-3S/cm) but face risks like flammability and leakage. Solid-state electrolytes (SSEs) emerge as promising alternatives, minimizing safety concerns and improving performance. This study introduces a tape-casting technique to produce stable and flexible quasi-hybrid polymer electrolytes (QHPEs) for lithium-ion batteries. These membranes integrate Poly (vinylidene fluoride-co-hexa-fluoropropylene) (PVDF-HFP) as a polymer matrix, a single-ion conducting polymer (SICs), and Ta-doped LLZO for enhanced mechanical stability and ionic conductivity. The addition of plasticizers is also explored to increase the ionic conductivity, addressing the low ionic conductivity of SICs at room temperature despite their high lithium transference number approaching unity. These plasticizers ethylene carbonate/propylene carbonate (EC/PC) remain inside the QHPE membrane, facilitating lithium-ion transport and thereby enhancing overall performance Comprehensive thermal, structural, and electrochemical characterization techniques validate their performance. The optimized QHPE exhibits impressive ionic conductivity (0.11 mS/cm at 25°C), a broad electrochemical voltage window up to 4.5V (j≤0.01mAcm-2), and excellent cycling stability (146 mAh/g at 1C, retaining 84.2% capacity after 250 cycles). Compatibility with lithium metal electrodes and successful integration with various cathode materials like LiFePO4 (LFP), NMC811, and NCA highlight the potential of these membranes for advanced battery applications.

Keywords: Composite Solid Electrolyte, Garnet, Hybrid Polymer electrolyte, Lithium Metal, Single-Ion-Conductor