Uniformly growing Co9S8 nanoparticles on flexible carbon foam as a free-standing anode for lithium-ion storage devices

Lithium-ion capacitor (LIC) possesses multiple merits of Faradaic and capacitive behaviors and shows excellent energy and power densities. Herein, Co 9 S 8 nanoparticles embedded on melamine foam derived three-dimensional (3D) carbon foam (M-Co 9 S 8 @NCF) was successfully constructed by an in-situ anchoring and annealing method. When the composite was used as a free-standing anode electrode of lithium-ion battery, volume expansion effect is relieved and reaction kinetic is significantly improved benefitting from the synergistic effect of unique 3D carbon network and ultrafine nanoparticles. Therefore, the M-Co 9 S 8 @NCF free-standing electrode delivers superior rate performance (1024 mAh g −1 at 0.1 A g −1 and 468 mAh g −1 at 2 A g −1 ) and stable cycling performance (617 mAh g −1 at 1 A g −1 for 500 cycles). Moreover, porous nitrogen-doped carbon foam (PNCF) was synthesized as the cathode of LIC. M-Co 9 S 8 @NCF//PNCF LIC device was then fabricated to combine the advantages of battery-type anode and supercapacitor-type cathode, which achieves a high energy density (166 Wh kg −1 at 182 W kg −1 ), high power density (83 Wh kg −1 at 7674 W kg −1 ) as well as satisfactory capacitance retention (83.5% at 5 A g −1 after 5000 cycles). This work offers a convenient method to construct metal sulfide-based free-standing electrode for the advanced lithium-ion storage devices.