Oxygen vacancy-enriched TiO2 nanosheets filled PVDF electrolyte for semi-solid-state batteries: Synergistic effects of conformational transition and defect sites

Abstract

The advancement of polymer solid electrolytes is essential for the development of solid-state lithium-ion batteries (LIBs). Polyvinylidene fluoride (PVDF), recognized for its unique piezoelectric properties and hydrophobicity, emerges as a promising candidate for polymer solid-state electrolyte applications. Nevertheless, its practical usage is hindered by low ionic conductivity at room temperature. To overcome this limitation, we engineered a novel PVDF/LiTFSI/TiO₂-ov (PLTO) electrolyte by incorporating oxygen-rich vacancy titanium dioxide with PVDF, resulting in significant enhancements in both ionic conductivity and mechanical performance—crucial factors for the long-term stability of batteries. D33 measurements and Fourier transform infrared spectroscopy analyses revealed an increase in the β-phase (TTTT conformation) content of the doped PVDF, which substantially contributes to the improved piezoelectric performance. Furthermore, density functional theory (DFT) analysis indicated that oxygen vacancies facilitate the decomposition of lithium salts and enhance anion adsorption, thereby boosting ion transport efficiency. When integrated into a Li/PLTO/LiFePO₄ semi-solid-state battery, this electrolyte membrane achieved an impressive specific capacity of 154.22 mAh/g at room temperature and 0.5 C, maintaining 95.31 % capacity over 850 cycles, demonstrating exceptional durability. Additionally, lithium/lithium symmetric batteries constructed with PLTO exhibited long-term stability exceeding 3800 hours. The stability of this battery in practical applications, such as LED lighting and subtitle control, underscores its practicality and potential contribution to energy sustainability. This study offers new perspectives for the development of high-performance electrolyte membranes.