Constructing amorphous/crystalline heterointerface in cobalt sulfide for high-performance supercapacitors

Transition metal sulfides (TMSs) are promising cathode materials due to their high theoretical specific capacitance, but developing high-performance TMS-based supercapacitors still is a challenge. Constructing the amorphous/crystalline heterointerface in TMSs is deemed to be an effective strategy for boosting ion/electron transport and reaction kinetics, thus endowing electrode materials with intriguing properties and innovative applications. In this work, the cobalt sulfide (donated as a/c-CoS) with the heterointerface between crystalline and amorphous coordinated with aluminum, nitrogen and carbon is rationally designed and prepared via a facile sulfuration using CoAl-MOF as the self-sacrificing template. The electrochemical performance can be tuned by controlling the sulfur source concentration at a modest level during the sulfuration. The optimal a/c-CoS(10) displays a high electrochemical performance with a specific charge of 1487.0C g−1 at 1 A g−1, good rate capability, and satisfactory cycling stability (87.4 % retention after 5000 cycles at 1 A g−1). Density functional theory (DFT) calculations reveal that the amorphous-crystalline heterophase structure has a stronger adsorption to OH− and higher electrochemical reaction activity compared to the crystalline Co3S4 counterpart, resulting in faster ion/electron transport and reaction kinetics. Accordingly, the as-fabricated a/c-CoS(10)//AC device provides a great energy density of 39.3 Wh kg−1 at a power density of 800 W kg−1. The unique heterophase structure (donated as a/c-CoS) was composed of crystalline Co3S4 and amorphous CoS coordinated with aluminum, nitrogen and carbon was rationally designed and prepared via the sulfuration of self-sacrificing template CoAl-MOF. [Display omitted] •Cobalt sulfide (a/c-CoS) with amorphous/crystalline heterointerface was prepared.•The a/c heterointerface provided abundant active sites and high conductivity.•DFT verified the a/c heterostructure endowed a higher OH− adsorption capacity.•The optimal a/c-CoS(10) exhibited excellent electrochemical performances.•Assembled a/c-CoS//AC delivered an energy density of 39.3 Wh kg−1 at 800 W kg−1.