;This thesis investigates the synthesis of NASICON-structured Na₃V₂(PO₄)₃ (NVP) batteries using citric acid as a surfactant. The batteries are coated with a carbon film and doped with 1% and 3% magnetic elements. By applying a magnetic field, the internal lattice size is altered, and various battery performance metrics are tested. At high temperatures (800K), doping elements can react with phosphorus, potentially forming crystalline structures, leading to impurity formation at high doping levels. To avoid impurities affecting the sample structure, 1% and 3% doping levels are chosen for experimentation.
First, XRD is used to confirm whether the samples are NASICON-structured NVP. Raman spectroscopy is then employed to analyze the disordered carbon film on the surface and to determine the ratio of disordered carbon to ordered graphite carbon. Different current collectors, copper foil and aluminum foil, are used to test the sodium-ion intercalation and deintercalation capabilities of the samples in low-voltage and high-voltage batteries, respectively.
The initial three charge-discharge cycles are tested to identify the charge-discharge platforms of the batteries. A 50-cycle test under varying magnetic fields evaluates the battery lifespan, while Crate tests under varying magnetic fields assess the battery′s fast charge-discharge performance. Finally, EIS equivalent circuit analysis is conducted to ascertain various internal resistances and diffusion rates within the battery.
The study finds that using 3% Fe on aluminum foil and 1% and 3% Co improves battery performance under a magnetic field. For Ni, 1% doping on copper foil enhances performance due to the magnetic field.
