Effect of pore size and pore wall thickness of mesoporous phase in tin phosphate composite on electrochemical cycling

Abstract

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 CH3(CH2)nN(CH 3)3Br. Because the crystalline phase (Sn2P 2O7) 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%. This decreased to 67, 63, and 59% with increasing pore size, n = 13, 15, and 17, respectively.