As a new type of energy storage device, supercapacitors have the advantages of high-power densities, high safety factors, and low maintenance costs, so they have attracted widespread attention among researchers. However, a major problem with supercapacitors is that their energy densities are not high enough, which limits their application. Therefore, it is crucial to expand the application scenarios of supercapacitors to increase their energy density as much as possible without diminishing their advantages. The classification and working principles of supercapacitors are introduced in this paper. The electrochemical properties of pure NiS materials, NiS composites with carbon materials, NiS composites with sulfide materials, and NiS composites with transition metal oxides for supercapacitors are summarized. This paper may assist in the design of new electrode materials for NiS-based supercapacitors.

As a representative boundary, interphase-interface may affect the strength or ductility of multilayered composites dramatically. However, the effect of the interface with mismatch dislocations on the mechanical behavior of multilayered composites is still not clear. In the present work, we performed molecular dynamics simulations to investigate the effect of interface structures and layer spacing on the mechanical properties of the Ti/Al nanolaminate. The results indicate that there are two transitions of the plastic deformation mechanism in the Ti layer with the increase of layer spacing in the sample with a coherent interface. The plastic deformation mechanism evolves from one that is dominated by dislocation to the phase transformation from the hcp-Ti to the fcc-Ti mode, which transfers to the dislocation slip deformation again. For the samples with an incoherent interface, the plastic deformation is dominated by the transformation from hcp-Ti to fcc-Ti, regardless of the variation of layer spacing, while the plastic deformations in the Al layers are mainly dislocations confined in the layer slip in the samples with both coherent and incoherent interfaces. When the layer spacing is larger than 6.6 nm, an obvious second hardening is observed due to the superior dislocation storage ability of the Ti/Al laminate with the incoherent interface. Meanwhile, extraordinary ductility is obtained when optimal layer spacing is employed in the Ti/Al laminate. Moreover, the phase transformation mechanism of hcp-Ti to bcc-Ti has also been explicated in the present work. The general conclusions derived from this work may provide a guideline for the design of high-performance Ti/Al multilayer and alloy devices.

Dual-phase nanoscale lamellar microstructures containing alternating regions of soft phase and hard phase are known to produce alloys with an exceptional combination of strength and plasticity. Here, the effect of layer thickness on the mechanical properties and deformation mechanism of the fcc/bcc dual-phase CoNiFeAl_xCu_1−x high-entropy alloys multilayers are investigated by the molecular dynamics simulation method. The results show that the deformation behavior of the multilayers is strongly related to the layer thickness. At the yield point, the deformation behavior of the small thickness multilayer is caused by the dislocation slip in the fcc phase, while the plastic deformation of the large thickness multilayer is initiated by the bcc → hcp phase transformation in the bcc phase. During the subsequent plastic deformation, the phase transformation of bcc → fcc also occurred in the bcc phase of the multilayer, which depended on the relative size of the bcc phase in the multilayer. Especially for the multilayer with the layer thickness of 2 nm, the bcc → fcc phase transformation promotes the formation of twins, and the fcc/bcc phase interface transforms into a perfect twin boundary. The twin formation mechanism and phase transformation mechanism are also discussed in detail.

High-entropy alloys (HEAs) break the design concept of traditional alloys and exhibit excellent mechanical properties. However, as a new member of the alloy family in recent years, the dependence of the deformation behavior of the HEAs on alloy composition and twin boundary (TB) is still unclear, and many phenomena urgently need to be revealed. Here, the effects of TB spacing and Ni concentration on the mechanical properties and deformation behavior of the nano-twinned (CoCrFeCu)_1−XNi_X HEA (nt-HEA) under tensile loading are investigated by molecular dynamics simulation. The results show that with the decrease in TB spacing, the average flow stress of the nt-HEA changes from Hall–Petch strengthening to inverse Hall–Petch softening. When the TB spacing is greater than a critical value, the plastic deformation mechanism is dominated by the slip of partial dislocations. However, when the TB spacing is less than the critical value, the plastic deformation mechanism is transformed into the formation of voids induced by the amorphous phase, which becomes the key factor for the softening of the nt-HEA. It is also found that the mechanical properties of the nt-HEA can also change from strengthening to softening by adjusting Ni concentration, which is closely related to the change of stacking fault energy of the nt-HEA. In addition, the plastic deformation mechanism and voids formation mechanism of the nt-HEA are also discussed in detail.