The Semicoherent Interface and Vacancy Engineering for Constructing Ni(Co)Se2@Co(Ni)Se2 Heterojunction as Ultrahigh‐Rate Battery‐Type Supercapacitor Cathode

Abstract

AbstractRestricted rate capability is the key bottleneck for the large‐scale energy storage of battery‐type supercapacitor cathode due to its sluggish reaction kinetics. Herein, Ni(Co)Se2@Co(Ni)Se2 semicoherent heterojunctions with rich Se vacancies (Vr‐Ni(Co)Se2@Co(Ni)Se2) as cathode are first constructed. Such a vacancy and heterointerface manipulation can not only essentially regulate the electronic structure and enhance ions adsorption capability, but also rationalize the chemical affinities of OH– ions in diffusion pathway revealed by systematic characterization analysis and first‐principle calculations. The as‐prepared cathode delivers large specific capacity of 264.5 mAh g–1 at 1 A g–1 and excellent cycle stability. Surprisingly, it presents ultrahigh rate with the retention of 159.7 mAh g–1 even at 250 A g–1. Moreover, the single phase transition mechanism of the cathode is elucidated systematically using series of ex situ techniques. In addition, contributed by the unique cathode and the self‐synthesized N/S co‐doped corncob‐derived porous carbon (N/S‐BPC, 316.1 F g–1 at 1 A g–1) anode, a high‐performance hybrid supercapacitor (HSC) is developed, which shows the energy density of 68.1 Wh kg–1 at 0.75 kW kg–1 and a superior cycle performance. The findings highlight a coordination strategy for the rational design of ultrahigh‐rate battery‐type HSC cathode, greatly pushing their commercial application processes.