Kirkendall Growth of Hollow Mn3O4 Nanoparticles upon Galvanic Reaction of MnO with Cu2+ and Evaluation as Anode for Lithium-Ion Batteries

We report the formation of high surface area hollow Mn 3 O 4 nanoparticles that form as a result of the galvanic reaction of Cu 2+ with MnO nanocrystals concomitant with a nanoscale Kirkendall effect. The MnO nanocrystals were prepared according to the ultralarge scale synthesis reported by Hyeon, which allowed the preparation of hollow Mn 3 O 4 in multigram quantities. Ex-situ analyses with transmission electron microscopy and powder X-ray diffraction show the morphology and phase stability of the hollow particles correlate with DSC-TGA data and show collapse of the hollow particles at temperatures greater than 200 °C. Electrodes fabricated from hollow Mn 3 O 4 exhibited excellent initial Li ion storage capability (initial discharge capacity = 1324 mAh/g) but poor cycling performance (97% loss of discharge capacity after 10th cycle), whereas Mn 3 O 4 -MWCNT electrodes exhibited good reversibility and discharge capacity of 760 mAh/g after 100 cycles.