Kinetics-Favorable Ultrathin NiCo-MOF Nanosheets with Boosted Pseudocapacitive Charge Storage for Quasi-Solid-State Hybrid Supercapacitors.

Bimetallic metal-organic frameworks (MOFs) with an ultrathin configuration are compelling materials for developing high-performance energy storage devices on account of their unique structural merits. Herein, a hydrangea-like NiCo-MOF is well prepared using controllable solvothermal and cation-exchange processes, synchronously achieving bimetallic nodes and hierarchical ultrathin architecture. The structural superiority enables NiCo-MOF of expanded electrons' transfer pathways and multitudinous electrolytes' diffusion channels, resulting in a significant enhancement in pseudocapacitive performance. Coupling with the bimetallic nature and constructional advantages, NiCo-MOF shows superior gravimetric capacity (832.6 C g at 1 A g) and electrochemical kinetics to those of monometallic Ni-MOF and Co-MOF. Importantly, the quasi-solid-state hybrid supercapacitor (HSC) based on the NiCo-MOF cathode and active carbon (AC) anode delivers a desirable energy density (45.3 Wh kg at 847.8 W kg), a favorable power density (7160.0 W kg at 23.3 Wh kg), a remarkable cyclability (82.4% capacity retention over 7000 cycles), and a capability of driving miniature electronics, exhibiting its potential in practical applications. This work presents an efficient design strategy to develop kinetics-favorable MOF materials for energy storage.