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).

Polypyrrole Modified MoS2 Nanorod Composites as Durable Pseudocapacitive Anode Materials for Sodium-Ion Batteries

As a typical two-dimensional layered metal sulfide, MoS₂ has a high theoretical capacity and large layer spacing, which is beneficial for ion transport. Herein, a facile polymerization method is employed to synthesize polypyrrole (PPy) nanotubes, followed by a hydrothermal method to obtain flower-rod-shaped MoS₂/PPy (FR-MoS₂/PPy) composites. The FR-MoS₂/PPy achieves outstanding electrochemical performance as a sodium-ion battery anode. After 60 cycles under 100 mA g⁻¹, the FR-MoS₂/PPy can maintain a capacity of 431.9 mAh g⁻¹. As for rate performance, when the current densities range from 0.1 to 2 A g⁻¹, the capacities only reduce from 489.7 to 363.2 mAh g⁻¹. The excellent performance comes from a high specific surface area provided by the unique structure and the synergistic effect between the components. Additionally, the introduction of conductive PPy improves the conductivity of the material and the internal hollow structure relieves the volume expansion. In addition, kinetic calculations show that the composite material has a high sodium-ion transmission rate, and the external pseudocapacitance behavior can also significantly improve its electrochemical performance. This method provides a new idea for the development of advanced high-capacity anode materials for sodium-ion batteries.

Fabrication of amorphous hollow mesoporous Si@SiOx nanoboxes as an anode material for enhanced lithium storage performance

Hollow mesoporous Si@SiOx nanoboxes are synthesized successfully by a simple sol–gel reaction of triethoxysilane using Fe2O3 nanocubes as the template, followed by a thermal reduction process and subsequent acid treatment process.