Carbon-reinforced NiS/TiCT MXene composite as an anode for superior-performance lithium-ion capacitors.

Lithium ion capacitors (LICs) are a new generation of energy storage devices that combine the super energy storage capability of lithium ion batteries with the satisfactory power density of supercapacitors. The development of high-performance LICs still faces great challenges due to the unbalanced reaction kinetics at the anode and cathode. Therefore, it is an inevitable need to enhance the electron/ion transfer capability of the anode materials. In this paper, to obtain a superior-rate and high-capacity NiS-based anode, highly conductive TiCT MXene sheets were introduced to sever as the carrier of NiS nanoparticles and simultaneously an amorphous carbon layer which coats onto the surface of NiS nanoparticles was in-situ generated by the carbonization of dopamine reactant. The as-synthesized NiS/TiCT/C composite exhibits a high specific surface area (112.6 m/g) because of the addition of TiCT that can reduce the aggregation of NiS nanoparticles and the in-situ generated amorphous carbon layer that can suppress the growth of NiS nanoparticles. The NiS/TiCT/C anode possesses a remarkable reversible discharge specific capacity (626.0 mAh/g under 0.2 A/g current density), which increases to 1150.8 mAh/g after 400-cycle charge/discharge measurement at the same measurement condition indicating eminent cyclability, along with superior rate capability. To construct a superior-performance LIC device, a sterculiae lychnophorae derived porous carbon (SLPC) cathode with an average discharge specific capacity of 73.4 mAh/g@0.1A/g was prepared. The NiS/TiCT/C//SLPC LIC device with optimal cathode/anode mass ratio has a satisfactory energy density ranging from 32.8 to 119.1 Wh kg at the corresponding power density of 8799.4 to 157.5 W kg, together with a prominent capacity retention (95.5 %@1 A/g after 10,000 cycles).