Interlayer and intralayer co-modified flexible V_(2)CT_(X) MXene@SWCNT films for high-power Li-ion capacitors

As an emerging member of the two-dimensional(2D)material family,V_(2)CT_(X)MXene shows great potential in the application of lithium-ion capacitors(LICs)due to its unique structure and excellent electrical conductivity.However,severe nanosheets stacking and intra-layer transport barriers have limited the further development of V_(2)CT_(X)MXene-based materials.Herein,we prepared Kions and–O functional group co-modified V_(2)CT_(X)MXene(VCT-K)and further incorporated it with single-walled carbon nanotube(SWCNT),obtaining freestanding V_(2)CT_(X)composite films(VCT-K@C)with the 3D conductive network.Significantly,K+ions were introduced into V_(2)CT_(X)MXene to stabilize the interlayer structure and prevent the aggregation of nanosheets,the terminal group of–O was controllably modified on the surface of MXene to improve the Li+ions storage reversible capacities and the SWCNT acted as the bridge between MXene nanosheets to opens up the channels for ion/electron transportation in the longitudinal direction.Benefited from the synergistic effect of VCT-K and SWCNT,the VCT-K@C exhibits superior reversible specific capacities of 671.8 mA h g^(-1)at 0.1 A g^(-1)and 318 mA h g^(-1)at 1.0 A g^(-1).Furthermore,the assembled LICs with VCT-K@C anode coupling activated carbon(AC)cathode deliver an outstanding power density of 19.0 kW kg^(-1)at 67.4 Wh kg^(-1),a high energy density of 140.5 Wh kg^(-1)at 94.8 W kg^(-1)and a stable capacitance retention of 86%after 6000 cycles at 10 A g^(-1).Such unique structures and excellent electrochemical properties are expected to pave the way for the large-scale application in LICs of MXene-based materials.