An investigation of nanofibers applications as a lithium-ion battery separator

In this thesis, the production and characterization of polyvinylidene fluoride (PVDF) and silicon dioxide (SiO2)-based nanofibers were conducted for use as separator materials in lithium-ion batteries. In the study, PVDF polymer was used as the raw material, dimethylformamide (DMF) and acetone were employed as solvents, and SiO2 served as the functional additive. In the initial stage, the properties of PVDF-based polymer solutions containing different concentrations of SiO2 were determined through conductivity, viscosity, and surface tension tests. Subsequently, nanofibers were produced using the electrospinning method under optimum process parameters. Various analyses were conducted for the characterization of the produced PVDF/SiO2 nanofibers. Scanning Electron Microscopy (SEM) was utilized to examine fiber morphology, while (EDS) analysis was performed to confirm the presence of SiO2. Fourier-Transform Infrared Spectroscopy (FT-IR) was employed to investigate the chemical structure of the polymer and additive, and Differential Scanning Calorimetry-Thermogravimetric Analysis (DSC-TGA) was applied to assess the thermal stability and behavior of the nanofibers. Additionally, pore size, porosity, and electrolyte uptake tests were conducted to evaluate the feasibility of the nanofibers as separator materials for lithium-ion batteries. At the conclusion of the study, the solution properties, fiber morphology, chemical, thermal, and mechanical properties of the nanofibers, and their performance results were analyzed in detail and correlated. As a result of the analyses conducted in the study, the nanofiber material obtained from a solution with 11% PVDF and 3% SiO₂ concentrations were determined to be ideal as a lithium-ion battery separator. The nanofiber-based separator materials produced in this study are considered to possess high performance and strong potential for use as separators in lithium-ion batteries.