Production of LiFePO4 by glass-ceramic and solid state reaction methods and investigation of it's electrochemical performance

In this master thesis, lithium-based lead doped cathodes were produced for use in electrical devices and platforms. Glass ceramic method was used for this production. First of all, pure LiFePO4 was produced and then lead (Pb) doped cathodes were produced. This is done using the formula Li1,4Fe1-xPbxPO4 in the study, the variable x was determined as 0-0.03-0.06-0.09 and 0.12. By using Li₂O, Fe₂O₃, PbO and P₂O₅ chemicals with 99.9% purity in the synthesized cathode materials, acetone was mixed in a ball mill at 450 rpm for 18 hours. Grinding powders were put into crucibles and placed in an electric furnace for 2 hours at 1200˚C for melting. The glass material removed from the furnace was frozen using liquid nitrogen for instant cooling. The material, wich was homogenized and pulverized with acetone in a mortar, was ground with 10% glucose. The prepared humune was subjected to heat treatment by rising to 850˚C in 5 minutes and waiting for 12 hours. This heat treatment was carried out in a quartz tube furnace with 7% Ar/H₂ gas. In contrast to a less applied glass ceramic method in terms of reliability and comparison of the study; by following a different procedure with the frequently used solid state method, production was carried out with the same formula and doping ratios. In this method, Li2CO3, FeC2O4.2H2O, NH4H2PO4, PbO and C6H12O6 with 99.9% purity were used. All materials were mixed in a ball mill with acetone at 350 rpm at stoichiometric ratios for 5 hours and dried in an oven. Then, it was subjected to heat treatment at 350˚C for 10 hours and the obtained material was ground in a ball mill again with acetone at 500 rpm for 5 hours. The resulting mixture was finally heat treated at 650˚C for 12 hours. Separately for both procedures; physical characterization and electrochemical analyzes were carried out. As a result of these datas, a rechargeable lithium battery was produced. When their morphological structures were examined, it were observed that no impurities were observed, crystallization took place and olivine structure was obtained, and Pb-Fe substitution took place. Obtained capacites, current and voltage values were evaluated with graphics. An increase was observed in the capacity value with doping, and the highest capacity was 80 mAh/g in the glass-ceramic method, and the highest capacity was 140 mAh/g in the solid state method. Keywords: lithium, battery, energy, LFP, glass-ceramics, solid state, Li-ion.