Interface engineering with porous graphene as deposition regulator of stable Zn metal anode for long-life Zn-ion capacitor

The zinc (Zn) dendrite accumulation leads to poor Coulombic efficiency, continuously failing life and severe safety risks, which seriously impede the commercial application of Zn ion capacitors (ZICs). Herein, an interface engineering is proposed for the Zn metal anode to restrain the dendrite by using porous flame reduced graphene oxide (FRGO) as the ex-situ protective and regulated layer to induce the Zn crystal growth and restricts the side reactions. The FRGO possesses extensive nanoscale pores and zincophilic oxygen-containing functional groups, which can absorb Zn2+ and nucleate preferentially on the surface of FRGO, then induce the growth of Zn parallel to the graphene sheet by matching the basal (002) plane of metallic Zn to minimize lattice strain. As a result, it eliminates the tip effect and achieves the deposited Zn with a uniform and flat surface. Therefore, The FRGO on the Zn (FRGO@Zn) anode significantly reduces the nucleation overpotential and improves the cycling life during the plating/stripping process. Notably, FRGO@Zn based ZIC can achieve 91.0% capacity retention after more than 20,000 cycles at 5 A g-1, and its capacity and maximum energy density are 150.6 mAh g-1 and 118.8 Wh kg-1, respectively. This interface engineering of FRGO for the Zn metal anode has excellent application potential and theoretical guidance in the ZICs field.