Using the synergistic effect of co-doping to engineer magnesium and chlorine co-doping to improve the electrochemical performance of Li2FeSiO4/C cathodes

Abstract

To compensate for the insufficiency of single doping and to exert the synergistic effect between the elements, further improving the electrochemical performance, a series of Mg and Cl co-doped Li2Fe1−xMgxSiO4–2xCl2x/C (x = 0, 0.01, 0.02, 0.03) nanocomposites (LFS, LFS-1, LFS-2, and LFS-3) have been synthesized by solvothermal method. Experimentally, Mg and Cl co-doping in Li2Fe1−xMgxSiO4–2xCl2x/C were confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution transmission electron microscope, and field-emission gun scanning electron microscopy elemental mapping, while electrochemical cycling performance showed improved performance. According to the results, LFS-2 outperforms other nanocomposites in terms of electrochemical performance, rate capability, and initial discharge capacity, with a capacity of 238.3 mAh·g−1 after 100 cycles of charging and discharging at 0.05 C. This is because it has a stable monoclinic structure free of impurities, a lower charge transfer resistance, and a higher Li-ion diffusion coefficient. Our findings suggest that Mg and Cl co-doping might be a feasible low-cost technique to enhance the electrochemical performance of silicate-based cathode materials, taking into account potential and electronic conductivity advantages.