As mentioned above, the different charge storage performances and frequencydependent behaviors of VG-M and VG-S may be suggestively related to the morphology. The lower capacitance of VG-S may be attributed to the fiber-like morphology, which the self-folding caused by free reduction leads to the decrease of surface area. Due to the increase of hydrophobicity, electrolyte ions cannot access the depth of the particles. However, from a macroscopic perspective, the large pores created from the stacking of particles provide an ion diffusion path for high-speed ion migration, and thus improves the rate capability. As a contrast, VG-M with a sheet morphology achieves a much higher capacitance. This can be explained that the much thinner sheets improve the surface area where more electrolyte ions can access. In addition, the sheet-to-sheet attachment enables better connection for electron migration, and then activates more sheets to store charges. As a price, this better material connection and more compact material structure to some extent limit the ion diffusion channel and result in a slightly lower rate capability.