Observation of Reversible Pore Change in Mesoporous Tin Phosphate Anode Material during Li Alloying/Dealloying

We observed the pore expansion and contraction of mesoporous tin phosphate during Li alloying/dealloying using small-angle X-ray scattering and transmission electron microscopy. As-prepared mesoporous tin phosphate showed pore and porewall sizes of 3 and , respectively. During lithium alloying (discharging), pore size was slightly contracted, but porewall size was slightly expanded within the range of . However, during lithium dealloying (charging), pore and porewall sizes recovered to their original sizes before cycling. The charged sample had a nanoscale pore array with a more or less uniformly sized open-porewall structure of amorphous lithium phosphates with metallic face-centered-cubic nanocrystals in diameter.