fig8

Figure 8. Strain engineering on energy storage and its mechanism analysis. (A) Schematic showing the different chemical reaction pathways of the nanosheets. Ex-situ Raman spectroscopy reveals different electrochemical signatures based on the Raman of polysulfides for pristine MoS₂ and interface-strained MoS₂ at (B) OCV, (C) 1.75V and (D) 0.01 V. Normalized differential capacity measurement for MoS₂ (E) and vertically stacked C-MoS₂ nanosheets (F), with two arrows indicate the potential of direct chemical conversation and intercalation reactions; (A-F): quoted with permission from Oakes et al.^[106]; (G) Schematic illustration of the reversible intercalation mechanism of K⁺ ions in 2D VOPO₄-graphene multilayer heterostructures; (H) Charge and discharge profiles of VOPO₄-graphene cathodes for K⁺ ion batteries and corresponding in-situ XRD patterns; (I) The interlayer spacing of VOPO₄-graphene calculated from the XRD pattern during the process of charge and discharge; (J) Comparison of cycle performance of VOPO₄-graphene heterostructure, restacked VOPO₄ nanoflakes, and bulk VOPO₄·2H₂O at 0.1 C; (K) Rate capability comparison of VOPO₄-graphene heterostructure, restacked VOPO₄ nanoflakes, and bulk VOPO₄·2H₂O at various current densities from 0.1 to 20 C; (G-M): quoted with permission from Xiong et al.^[80]. OCV: Open-circuit voltage; XRD: X-ray diffraction; 2D: two-dimensional.