Conferring improved specific capacity and stability in heterostructures by built-in electric field as battery-type electrodes for hybrid supercapacitors

Coupling layered double hydroxides (LDHs) with functional substrate to construct heterostructures has been proved an effective mean to improve the capacity and stability for LDHs. The optimization of such heterostructures usually focuses on the regulation of chemical components, whereas the ordered assembly of them remains lacking. In this work, NiCo-LDH/Mo2TiC2Tx heterostructures with tight contact interface, acting as the battery-type electrodes for hybrid supercapacitors (HSCs), were successfully prepared by tuning the synthesis temperature. Detailed theory calculations reveal that the integration of NiCo-LDH and Mo2TiC2Tx enhances the overall conductivity, electron transport rate and OH- adsorption capacity, owing to the establishment of a strong built-in electric field at the interface. Besides, the optimized NiCo-LDH/Mo2TiC2Tx-120 degrees C heterostructure consists of in-plane hetero-nanosheets with abundant active sites and short ion diffusion paths. As a result, the NiCo-LDH/Mo2TiC2Tx-120 degrees C electrode exhibits a higher specific capacity (989 C g-1 at 1 A g- 1) and stability than other counterparts. Moreover, the assembled NiCo-LDH/Mo2TiC2Tx-120 degrees C//AC (activated carbon) HSCs achieve a high energy density of 44.7 Wh kg- 1 at a power density of 961 W kg- 1, and a desirable durability of 99.4 % capacity retention after 10000 cycles. This work provides in-depth understanding for the design of highperformance heterostructure for HSCs.