The Semicoherent Interface and Vacancy Engineering for Constructing Ni(Co)Se-2@Co(Ni)Se-2 Heterojunction as Ultrahigh-Rate Battery-Type Supercapacitor Cathode

Restricted 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)Se-2@Co(Ni)Se-2 semicoherent heterojunctions with rich Se vacancies (Vr-Ni(Co)Se-2@Co(Ni)Se-2) 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.