The morphology and internal structure of various particulate metal anodes was examined before and after lithiation, with XRD, SEM and HREM. After one lithiation cycle, fracture was observed in particles of large size (>1μm). However, for all metals tested, the intact cycled metal was also found to form nanocrystallites (<15nm) mixed with an amorphous phase. These nanocrystallites appear to form due to high density nucleation of the lithiated phase. When observed after 50 cycles (maximum capacity range), Sb displayed dispersed nanocrystalline particles of the same size as the nanocrystallites initially observed. This result suggests that a different failure mechanism of these materials systems acts over extended cycles, after which high volume changes no longer drive crack growth. A chemical degradation mechanism is proposed.
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