Figure 3. In situ SEM images of a Si nanoparticle aggregate anode (D_avg for aggregates: approximately 10 μm; D_avg for nano-Si particles: approximately 100 nm) during the 1st charge/discharge process.

The charge/discharge conditions were 0.25 C (constant current mode) at cut-off voltages of −3.88 V and −2.40 V (vs. LiCoO₂). (a–c) In situ SEM images of Si nanoparticle aggregates. (d) The relative frequencies as a function of the volume change in Si nanoparticle aggregates after (blue) the charge and (red) discharge processes relative to the initial volume.