The modification of Li2FeSiO4 materials by dual doping with Ag and PO43- or BO33-

In this paper, dual doped Li2Fe0.98Ag0.02(SiO4)(1 - x)(PO4)(x)/C and Li2Fe0.98Ag0.02(SiO4)(1 - x)(BO3)(x)/C (x = 0.01, 0.02, 0.03, 0.05) materials were synthesized by high temperature solid state method. Among all the materials dual-doped with Ag+ and PO43-, the initial discharge capacity of Li2Fe0.98Ag0.02(SiO4)(0.97)(PO4)(0.03)/C is the highest, which is 167.7 mAh/g, which is equivalent to 1.01 Li+ deintercalation, and its lithium-ion diffusion coefficient is also the largest. For the materials dual-doped with Ag+ and BO33-, the initial discharge capacity of Li2Fe0.98Ag0.02(SiO4)(0.99)(BO3)(0.01)/C is the highest , which is 150.8 mAh/g. After 10 cycles of charging and discharging at 0.1 C, the capacity becomes 131.2 mAh/g, and the retention rate is 87%. The above-mentioned materials which have good electrochemical performance were analyzed by SEM and XRD. According to the SEM images, no obvious agglomeration was found in Li2Fe0.98Ag0.02 (SiO4)(0.97)(PO4)(0.03)/C and Li2Fe0.98Ag0.02 (SiO4)(0.99)(BO3)(0.01)/C. Meanwhile, XRD analysis showed that the overall structure is still Li2FeSiO4 with monoclinic structure, but there are traces of Li2Fe3O4 characteristic peaks.