Fig. 2: Direct observation of sulfur wetting, growth, and de-wetting processes.

a Schematic illustration of the wetting, merging, growth and de-wetting processes of the sulfur droplets on gold electrode. b In situ real-time imaging and c corresponding voltage versus capacity curves for the wetting, merging, growth and de-wetting processes. The numbers shown in (b) refer to the droplets which will merge and grow. Scale bar in (b) is 20 μm. d Plot of the sulfur droplet response time versus overpotential (η). The response time refers to the shape change of the droplets from the wetting state to a near-spherical shape. The dashed line is a guide for the eyes. e Voltage-dependent no-nucleation range (below 2.6 V), nucleation but non-wetting range (2.6–2.9 V) and wetting range (higher than 2.9 V). f Snapshots of sulfur droplet wetting on gold at different voltages for a fixed total capacity of 0.001 mAh. Scale bar in (f) is 50 μm.