Alleviating zinc dendrites on acid-functionalized vertical graphene for high-performance flexible zinc-ion hybrid capacitors

Due to the growing demand for wearable electronics, flexible zinc-ion supercapacitors (f-ZIHCs) have attracted considerable scientific and technological attention. However, their widespread adoption is hindered by critical challenges such as limited anode flexibility and inadequate cycling stability. To overcome these limitations, this study introduces a dendrite-free Zn anode fabricated through a strategic combination of plasma-enhanced chemical vapor deposition growth of three-dimensional (3D) vertical graphene (VG) on carbon cloth substrate and a subsequent simple, rapid acid functionalization step that incorporates oxygen and nitrogen heteroatoms onto the VG surface. The resulting anode, denoted as VG–HH–Zn, leverages the 3D hierarchical VG array to regulate Zn deposition behavior and promote a highly reversible Zn plating/stripping process. When integrated into an f-ZIHC with an activated carbon cathode, the VG–HH–Zn anode enables outstanding electrochemical performance: a specific capacity of 650.6 F g⁻¹ (289.6 mAh g⁻¹) at 0.3 A g⁻¹, a high energy density of 229.5 Wh kg⁻¹ at 238.1 W kg⁻¹, and exceptional cycling stability with 95 % capacity retention after 10,000 cycles at 20 A g⁻¹. Moreover, the assembled quasi-solid-state device maintains stable electrochemical performance under various mechanical deformation modes, including bending and folding, underscoring its suitability for flexible electronics. The straightforward and scalable fabrication strategy presented here offers a promising route for the development of advanced flexible electrodes and accelerates the commercialization of f-ZIHCs.