Modulating inner Helmholtz layer by electrocatalytically sieving [Zn(H2O)6]2+ for 10000-cycle zinc-ion hybrid capacitors under extremely harsh conditions

Abstract

Zinc-ion hybrid capacitors (ZIHCs) are famous for potential applications in grid-scale energy storage devices with fast-charge capability. However, their industrialization is severely plagued by inferior performance caused by the sluggish Zn2+ desolvation kinetics with large spatial diffusion hinderance of [Zn(H2O)6]2+ in the inner Helmholtz plane (IHP) layer, especially under low-temperature surroundings. Herein, the simultaneous rapid desolvation strategy via pore sieving and electrocatalysis is initially proposed to promote [Zn(H2O)6]2+ dissociation, regulating the isolated Zn2+ behaviors in the IHP. Specifically, heteroatom-decorated carbon microspheres with multi-level channels modulate the local distribution of electronic density, generating abundant catalytic sites to drive the kinetics of [Zn(H2O)6]2+ desolvation and free Zn2+ diffusion. Impressively, the catalytic desolvation behaviors and storage mechanism of ZIHCs are comprehensively investigated using in-situ electrochemical quartz crystal microbalance and various ex-situ/in-situ measurements as well as theoretical simulations, revealing significant interactions of isolated Zn2+ in the IHP. Consequently, the assembled ZIHCs exhibit a superior capacity of 177.2 mAh g−1, corresponding to a high energy density of 158.8 Wh kg−1, and provide a power density as high as 15.7 kW kg−1. Exposed to extreme environment, the ZIHCs encountered with severe solvation structure stabilize for 10000 cycles withcapacity retention of 99.42%, providing new insights of catalytically sieving into modulating IHP for high-performance ZIHCs under extreme conditions.