Figure 4. SEM images of morphology evolution of ZSONT/CC electrode, CC
electrode, and Cu electrode during the initial cycle: After being plated
with Li of (a, e, i) 5 mA h cm-2 and (b, f, j) 10 mA h
cm-2; after the anode were stripped (c, g, k) 5 mA h
cm-2 and (d, h, l) ~10 mA h
cm-2 Li from the ZSONT/CC, CC, and Cu electrode.
The lithium plating/stripping behavior on ZSONT/CC host was inspected by
a two-electrode cell configuration. Changes in the morphology of the
electrodes were observed (Fig. 4 ). When depositing 5 mA h
cm-2 Li in the ZSONT/CC host (Fig. 4a ), the
empty space in the CC network was almost covered and the porous
structure started to disappear. When the deposition capacity of Li
increases to 10 mA h cm-2 (Fig.4b ), the
carbon fibers were no longer visible (buried) with a flat surface (and
dendrite-like features were not observed when compared to the CC
electrode and Cu electrode (Fig. 4e, 4f, 4i, and 4j ).Figure S3a showed that the lithium can be observed from the
backside of the electrode, suggesting that the deposition of the lithium
was through the entire three-dimensional network of ZSONT/CC, instead of
located on the top surface. A cross-section image of the Li-plated
ZSONT/CC was taken (Fig. S3b ), and a rather uniform lithium
distribution was also found. After the anodes were plated with 10 mA h
cm-2 Li, the stripping process took place, and the
lithium started to be removed from the 3D electrode. As the lithium was
continuously stripped off the anode, the reverse morphological change
was observed, and ZSONT/CC host (fiber-like morphology) appears again
(Fig. 4c and 4d ). In contrast, large lithium patches were
observed on the Cu substrate when stripped to 1.0 V (Fig.4l ), indicating incomplete stripping and thus low coulombic
efficiency. The morphology evolution of the CC electrode upon charging
and discharging was also investigated. From Figure 4e , large
chunks were observed on the electrode surface when 5 mA h
cm-2 lithium was plated. When the plated lithium
capacity was increased to 10 mA h cm-2, the surface
remained bumpy (Fig. 4f ). After stripping (Fig. 4g and
4h ), large patch-like morphology was visible (marked by circles).