Interface bonding engineering for constructing a battery-type supercapacitor cathode with ultralong cycle life and high rate capability

The low rate and poor cycle greatly limit the large-scale applications of supercapacitors electrodes in energy storage field. In this work, the SnS2/Ni3S2 nanosheets arrays are bonded on N/S co-doped graphene nanotubes though N-Sn/Ni and S-Sn/Ni interface bonds employing a simple hydrothermal method to form a self-supported battery-type supercapacitors cathode. A series of characterization and DFT calculations indicate that the inter-face bonding not only automatically generates the internal electric field and allows more redox reactions to carry out easily, but also effectively reduces the OH- ions adsorption energy and maintains the integration of the electrode structure. This unique design greatly promotes the electronics/ions transfer and reaction kinetics of the cathode, and substantially enhances its rate capability and durability. Detailedly, a high specific capacity of 296.9 mAh g-1 at 2 A g-1 is obtained. More impressively, the cathode still holds 155.6 mAh g-1 when the current density is enlarged to 100 A g-1, as well as it can retain 84% initial capacity over 50,000 cycles. Besides, an assembled asymmetric supercapacitor utilizing the prepared N/S-GNTs@B-SnS2/Ni3S2 nanosheets arrays cath-ode and activated carbon anode presents a large energy density of 51 W h kg-1 at 850 W kg-1 and outstanding cycling stability. This work provides an effective strategy for improving rate capability and cycle lifespan of battery-type supercapacitors electrodes, and pushes the metal compounds forward a significant step in the practical applications of energy storage devices.