Electrostatic Interaction-directed Construction of Hierarchical Nanostructured Carbon Composite with Dual Electrical Conductive Networks for Zinc-ion Hybrid Capacitors with Ultrastability

Metal-organic framework(MOF)-derived carbon composites have been considered as the promising materials for energy storage.However,the construction of MOF-based composites with highly controllable mode via the liquid-liquid synthesis method has a great challenge because of the simultaneous heterogeneous nucleation on substrates and the self-nucleation of individual MOF nanocrystals in the liquid phase.Herein,we report a bidirectional electrostatic generated self-assembly strategy to achieve the precisely controlled coatings of single-layer nanoscale MOFs on a range of substrates,including carbon nanotubes(CNTs),graphene oxide(GO),MXene,layered double hydroxides(LDHs),MOFs,and SiO_(2).The obtained MOF-based nanostructured carbon composite exhibits the hierarchical porosity(V_(meso)/V_(micro)∶2.4),ultrahigh N content of 12.4 at.%and"dual electrical conductive networks."The assembled aqueous zinc-ion hybrid capacitor(ZIC)with the prepared nanocarbon composite as a cathode shows a high specific capacitance of 236 F g^(-1)at 0.5 A g^(-1),great rate performance of 98 F g^(-1)at 100 A g^(-1),and especially,an ultralong cycling stability up to 230000 cycles with the capacitance retention of 90.1%.This work develops a repeatable and general method for the controlled construction of MOF coatings on various functional substrates and further fabricates carbon composites for ZICs with ultrastability.

3D Carbon Frameworks for Ultrafast Charge/Discharge Rate Supercapacitors with High Energy‑Power Density

Carbon-based electric double layer capacitors(EDLCs)hold tremendous potentials due to their high-power performance and excellent cycle stability.However,the practical use of EDLCs is limited by the low energy density in aqueous electrolyte and sluggish diffusion kinetics in organic or/and ionic liquids electrolyte.Herein,3D carbon frameworks(3DCFs)constructed by interconnected nanocages(10-20 nm)with an ultrathin wall of ca.2 nm have been fabricated,which possess high specific surface area,hierarchical porosity and good conductive network.After deoxidization,the deoxidized 3DCF(3DCFDO)exhibits a record low IR drop of 0.064 V at 100 A g^−1 and ultrafast charge/discharge rate up to 10 V s^−1.The related device can be charged up to 77.4%of its maximum capacitance in 0.65 s at 100 A g^−1 in 6 M KOH.It has been found that the 3DCF-DO has a great affinity to EMIMBF4,resulting in a high specific capacitance of 174 F g^−1 at 1 A g^−1,and a high energy density of 34 Wh kg^−1 at an ultrahigh power density of 150 kW kg^−1 at 4 V after a fast charge in 1.11 s.This work provides a facile fabrication of novel 3D carbon frameworks for supercapacitors with ultrafast charge/discharge rate and high energy-power density.