Carbon-reinforced Ni3S2/Ti3C2Tx 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 Ni3S2-based anode, highly conductive Ti3C2Tx MXene sheets were introduced to sever as the carrier of Ni3S2 nanoparticles and simultaneously an amorphous carbon layer which coats onto the surface of Ni3S2 nanoparticles was in-situ generated by the carbonization of dopamine reactant. The as-synthesized Ni3S2/Ti3C2Tx/C composite exhibits a high specific surface area (112.6 m2/g) because of the addition of Ti3C2Tx that can reduce the aggregation of Ni3S2 nanoparticles and the in-situ generated amorphous carbon layer that can suppress the growth of Ni3S2 nanoparticles. The Ni3S2/Ti3C2Tx/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 Ni3S2/Ti3C2Tx/C//SLPC LIC device with optimal cathode/anode mass ratio has a satisfactory energy density ranging from 32.8 to 119.1 Wh kg-1 at the corresponding power density of 8799.4 to 157.5 W kg-1, together with a prominent capacity retention (95.5 %@1 A/g after 10,000 cycles).

Hydrothermal Synthesis of Co-Doped NiSe2 Nanowire for High-Performance Asymmetric Supercapacitors.

Co@NiSe2 electrode materials were synthesized via a simple hydrothermal method by using nickel foam in situ as the backbone and subsequently characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and a specific surface area analyzer. Results show that the Co@NiSe2 electrode exhibits a nanowire structure and grows uniformly on the nickel foam base. These features make the electrode show a relatively high specific surface area and electrical conductivity, and thus exhibit excellent electrochemical performance. The obtained electrode has a high specific capacitance of 3167.6 F·g-1 at a current density of 1 A·g-1. To enlarge the potential window and increase the energy density, an asymmetric supercapacitor was assembled by using a Co@NiSe2 electrode and activated carbon acting as positive and negative electrodes, respectively. The prepared asymmetrical supercapacitor functions stably under the potential window of 0⁻1.6 V. The asymmetric supercapacitor can deliver a high energy density of 50.0 Wh·kg-1 at a power density of 779.0 W·kg-1. Moreover, the prepared asymmetric supercapacitor exhibits a good rate performance and cycle stability.