Effect of Pore Size and Pore Wall Thickness of Mesoporous Phase in Tin Phosphate Composite on Electrochemical Cycling

摘要

We synthesized mesoporous/crystalline composite with a mass ratio of 1:2 (mesoporous: crystalline), and the resulting mesoporous tin phosphate has different pore size depending on the alkyl chain length (n - 11, 13, 15, and 17) of the surfactant CH_3(CH_2)_nN(CH_3)_3Br. Because the crystalline phase (Sn_2P_2O_7) to mesoporous phase mass ratio is fixed, a decrease in the capacity retention is mainly attributed to the deterioration of the mesophase. The mesoporous phase with smaller pore size causes higher capacity retention, with n = 11 showing the highest capacity retention corresponding to 82 percent. This decreased to 67, 63, and 59 percent with increasing pore size, n = 13. 15, and 17, respectively.