Regulation effects of Co2+ on the construction of a Cu-Ni(OH)2@CoO nanoflower cluster heterojunction: a critical factor in obtaining a high-performance battery-type hybrid supercapacitor

A Se-induced heterostructure electrode with polymetallic-CoNiFe towards high performance supercapacitors

Rational regulation of electrode materials with high conductivity and unexceptionable cycling stability is crucial to meet the requirements of high-performance supercapacitors (SCs). Herein, a hierarchical porous kebab-like heterostructure (CoNiFe-Se) is prepared by a facile solvothermal reaction and selenization step. Both experimental and computational results demonstrate that incorporating Se via hydrothermal reaction contributes to modulating the morphology and electronic structure of transition metal carbonate hydroxides. The heterostructured electrode with abundant active sites composed of electroactive polymetallic-CoNiFe imparts excellent charge storage. Additionally, the unique structure of CoNiFe-Se with its heterogeneous interface, oxygen vacancies and cavities improves electrochemical activity, accelerates electron transfer and suppresses the volume expansion during the cycling. As a result, the CoNiFe-Se exhibits excellent electrochemical performance of 5040 mF cm-2 at 1 mA cm-2 and long-term durability with 85.7% retained capacitance after 10 000 cycles. Interestingly, an integrated asymmetric supercapacitor performs well for energy storage. This finding opens a new avenue for developing transition metal carbonate hydroxides using selenization strategies in the field of SCs.

1D-on-1D core-shell cobalt iron selenide @ cobalt nickel carbonate hydroxide hybrid nanowire arrays as advanced battery-type supercapacitor electrode

Sluggish kinetics and poor structural stability are two main obstacles hampering the exploration of transition metal selenides (TMSs) for supercapacitor. Developing a reasonable core-shell heterostructure with unique morphology is an effective approach to resolve these issues. Herein, a core-shell cobalt iron selenide (CoFe₂Se₄) @ cobalt nickel carbonate hydroxide (CoNi-CH) heterostructure is directly fabricated on carbon cloth via an electrodeposition method followed by a hydrothermal reaction. In this well-defined heterostructure, one-dimensional (1D) CoFe₂Se₄ nanowires function as the cores and CoNi-CH nanowires as the shells, which combines the merits of highly conductive CoFe₂Se₄ for rapid electron transfer and highly electroactive CoNi-CH for multiple redox reactions. Further, the intimate interaction between CoNi-CH and CoFe₂Se₄ realizes large surface area with hierarchical network and generates rich heterointerfaces with modified the electronic structure. By virtue of its facile 1D-on-1D nanoarchitecture and synergistic effect, the CoFe₂Se₄@CoNi-CH electrode delivers a increased specific capacity of 218.6 mAh g^-1 at 1 A^-1 and enhanced rate capability (65.5% at 20 A g^-1) compared with pure CoFe₂Se₄ and CoNi-CH. Besides, a hybrid supercapacitor is established by coupling CoFe₂Se₄@CoNi-CH cathode and porous carbon anode, which enjoys a maximum energy density of 67.3 Wh kg^-1 at 765.9 W kg^-1 and prominent durability with 85.4% of capacity retention over 20,000 cycles.