Synthesis, Characterisation and Electrochemical Performance of Calcium Ion Doped LiFePO4 Cathodes in Phosphogypsum for Advanced Lithium Ion Batteries

Lithium iron phosphate (LiFePO4) is widely acknowledged for its superior thermal stability and cycle endurance, positioning it as a promising cathode material for lithium-ion batteries. However, its application in high-power domains is constrained by its low electrical conductivity. In this paper, calcium ions in phosphogypsum were successfully doped to modify LiFePO4/C composites as anode materials for lithium-ion batteries. The synthesized calcium-ion-modified olivine LiFePO4 was characterized using inductively coupled plasma, x-ray diffraction, scanning electron microscopy, and a constant current test system. The material's crystallinity was observed to increase from 87.1% to 91.3%, and the composites formed irregular yet uniformly distributed particles in the range of 170-270 nm. The initial discharge capacity of the LSG-LFP-1 can reach 163 mAh/g and 156 mAh/g at 0.1 C and 1 C, respectively, and its capacity retention reaches 99% after 200 cycles at 5 C. Impedance measurements revealed that the incorporation of calcium ions significantly reduced the resistive properties of the LiFePO4/C composite. This novel synthesis approach not only enhances the material's performance but also holds potential for the preparation of other advanced electrode materials for lithium-ion batteries.