Controllable Heterojunctions with a Semicoherent Phase Boundary Boosting the Potassium Storage of CoSe₂/FeSe₂

Abstract

Heterostructure construction is an efficient method for reinforcing K+ storage of transition metal selenides. The spontaneously developed internal electric fields give a strong boost to charge transport and significantly reduce the activation energy. Nevertheless, perfection of the interfacial region based on the energy level gradient and lattice matching degree is still a great challenge. Herein, rich vacancies and ultrafine CoSe2–FeSe2 heterojunctions with semicoherent phase boundary are simultaneously obtained, which possess unique electronic structures and abundant active sites. When employed as anodes for potassium‐ion batteries (PIBs), CoSe2–FeSe2@C composites display a reversible potassium storage of 401.1 mAh g−1 at 100 mA g−1 and even 275 mAh g−1 at 2 A g−1. Theoretical calculation also reveals that the potassium‐ion diffusion can be dramatically promoted by the controllable CoSe2–FeSe2 heterojunction.

Interphases in the electrodes of potassium ion batteries

“…A heterogeneous mixture with rich boundaries is considered as an effective approach for efficient potassium storage, as a built-in electric field can be formed at the heterogeneous interphase and the electronic properties can be improved by modifying the surface reaction kinetics, thus significantly accelerating charge transport [39,103]. A face-to-face CoSe 2 /FeSe 2 @C heterojunction with rich vacancies and low lattice misfits was controllably tuned by Qin et al [37]. On the one hand, the semi-coherent CoSe 2 /FeSe 2 phase boundary and vacancies, which was confirmed by the high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), caused the two individual planes of CoSe 2 /FeSe 2 to form a staggered angle of 20.48 • with a low lattice misfit of 12.07% (figure 9(a)).…”

“…For heterojunction active materials, the heterojunction interphases can result in synergistic effects such as rich phase boundaries and vacancies as well as a built-in electric field, which can considerably accelerate charge transport. A large amount of phase boundaries and vacancies can lead to the formation of defects that offer capacitive active sites with facile ion transport pathways for K-ion storage [37]. A built-in electric field can fasten the movement of ions due to electrostatic force, overcoming high energy barriers of K-ion migration when passing through the interphase.…”

“…A built-in electric field can fasten the movement of ions due to electrostatic force, overcoming high energy barriers of K-ion migration when passing through the interphase. More interestingly, the direction of the built-in electric field can alter during charging and discharging processes due to (de)potassiation of active materials, thereby constantly favouring ion transport [37][38][39].…”

Preparation of Porous Zn0.76Co0.24S Yolk‐Shell Microspheres with Enhanced Electrochemical Performance for Sodium Ion Batteries

“…Room-temperature rechargeable batteries are treated as one of the most potential solutions for worldwide energy storage. [5][6][7] Among them, lithium-ion batteries (LIBs) have been extensively studied for related merits, such as high energy density and excellent cycling performance. [8][9][10] Nonetheless, with the largescale application of LIBs, the increasing shortage of lithium resources has restricted their development.…”

FeSe2/CoSe2 Heterostructure with an Adjusting Electronic Structure for the Oxygen Evolution Reaction

“…Herein, the FeSe 2 /CoSe 2 bimetallic selenide with heterostructure was successfully synthesized by cation exchange using the MOFs template. [33] FeSe 2 /CoSe 2 catalyst exhibits the superior OER performance with a low overpotential of 344 mV at the current density of 10 mA cm À 2 , a small Tafel slope of 42 mV dec À 1 , and an excellent stability of 60 h. This performance is much higher than those of FeSe 2 , CoSe 2 , and RuO 2 commercial catalysts, resulting from its unique heterostructure and the introduction of Fe, which modulates the electronic structure to create the abundant active sites. This work provides a feasible way to prepare heterostructure electrocatalysts and enriches the applications of transition metal-based selenides for OER electrocatalytic.…”