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.