The effect of Ag or Zn composite on the electrochemical performance of Li2FeSiO4 cathode materials

The Li2FeSiO4/Ag-x and Li2FeSiO4/Zn-x (x = 0.01, 0.02, 0.03, 0.05) were synthesized through high-temperature solid-state method. Constant current charging-discharging, cyclic voltammetry, and electrochemical impedance spectroscopy analysis were conducted on the materials mentioned above. According to the test data, the Li2FeSiO4/Ag-0.02 shows stable electrochemical performance, and the initial discharge capacity is 161.2 mAh/g. After 10 cycles at 0.1 C, its capacity retention ratio is 91.4%. The diffusion coefficient of Li+ is higher than pure-phase materials by one order of magnitude, and it also has lower charge transfer resistance. The initial discharge capacity of Li2FeSiO4/Zn-0.02 is 147.5 mAh/g, and its capacity could sustain at 118.4 mAh/g after 10 cycles at 0.1 C. The diffusion coefficient of Li+ is an order of magnitude higher than that of pure-phase materials. It can be observed from the SEM image that the particle size of the Li2FeSiO4/Ag-0.02 is relatively uniform, and there is no obvious agglomeration. It can be seen from the XRD spectrum that there is no impurity peak in Li2FeSiO4/Ag-0.02 while the characteristic peak of Li2Fe3O4 could be found in the Li2FeSiO4/Zn-0.02. The cell volume of the Li2FeSiO4/Ag-0.02 increases and is larger than that of the pure-phase material.