Elimination of extraneous irreversible capacity in mesoporous tin phosphate anode by amorphous carbon coating

Mesoporous tin phosphate with a similar to 10 nm pore size was synthesized using a sodium-dodecyl-sulfate surfactant as a new anode for a Li-ion cell. The tin phosphate with body centered cubic (bcc) mesostructure exhibited a initial charge capacity of 540 mAh/g, and showed good capacity retention ratio, corresponding to 87% after 20 cycles. Relatively large irreversible capacity (571 mAh/g) ratio of 51%, which impedes the practical application in Li-ion cell, is reduced by the amorphous carbon coating. The coating leads not only to reduced extraneous irreversible capacity ratio of 26% but also improved capacity retention by 11% without changing the first charge cpacity, compared with the uncoated sample. However, intrinsic irreversible capacity loss from the decomposition reaction to tin metal and lithium phosphate phase is unavoidable. (c) 2006 The Electrochemical Society.