Control Technology Of Interlayer Spacing And Energy Storage Rate Capability Of Graphene-like Materials

Graphene-like materials are wildly employed as the electrode materials in electrochemical energy storage devices due to the large specific surface area,abundant accessible active sites,and fast ions diffusion channels in interlayers.However,graphene-like materials also exhibit some disadvantages such as the stacking of layered structure,obvious volume expansion and slow ions diffusion dynamics,which limits the rate capability and cycling stability of graphene-like materials.In the paper,based on the performance of materials determined by structure,different technologies were employed to tune the interlayer spacing of graphene-like materials,and the effects of interlayer spacing on ions diffusion dynamics and rate capability were explored.According to the selection principle of insertion material size from small to large,ions,atoms,nanosheets and organic molecule were used to expand the interlayer spacing of graphene-like materials.The research works are as follows:(1)La³⁺was pillared between the interlayer of Ti₃C₂(La/e-Ti₃C₂)by electrostatic self-assembly.The interlayer spacing of Ti₃C₂ is enlarged to 1.46 nm and the self-assembly is avoided due to the existence of La³⁺,which improves the capacitance performance and cycling stability when employing La/e-Ti₃C₂ as the electrode material of supercapacitor.La/e-Ti₃C₂ exhibits the best ions diffusion dynamics and rate capability compared with multilayer Ti₃C₂ and exfoliative Ti₃C₂.(2)Co atoms were pillared between the interlayer of Ti₃C₂(x-Co/m-Ti₃C₂)via in-situ thermal anchoring.The interlayer spacings of x-Co/m-Ti₃C₂ are 1.21 nm,1.36 nm and 1.33 nm when the thermal anchoring temperatures are 45?,65? and 85?,respectively.Co atoms not only display pillaring effects for preventing the self-stacking and increasing the interlayer spacing of Ti₃C₂,but also act as protective layers to reduce the formation of SEI and protect the structure integrity.The Li⁺diffusion dynamics and rate capability of x-Co/m-Ti₃C₂ possess a consistent variation tendency with the interlayer spacing,and they can obtain the best value when the interlayer spacing of x-Co/m-Ti₃C₂ equals 1.36 nm.(3)MoS₂ nanosheets were vertically pillared between Ta₄C₃(M-Ta₄C₃)through one-step hydrothermal.M-Ta₄C₃ demonstrates a large interlayer spacing as 1.69 nm.The self-stacking of Ta₄C₃ and the volume expansion of MoS₂ are effectively inhibited due to the cooperative effect of Ta₄C₃ and MoS₂ during the Na⁺insertion/extraction,which leads to M-Ta₄C₃ demonstrates an excellent cycling stability.The Na⁺diffusion dynamics and rate capability of M-Ta₄C₃ are more outstanding than that of MoS₂ and Ta₄C₃.(4)The molecular welding was designed and employed in controllably tuning the interlayer spacing of GO and Ti₃C₂.The diamine molecules(H₂N(CH₂)_xNH₂)are welded between the interlayer of GO via a dehydration condensation reaction between-NH₂ on both sides of diamine molecules and-COOH on the surface of GO(x DM-GO).The interlayer spacings of x DM-GO is 0.90,0.95 and 0.97 nm through welding different diamine molecules.Flexible diamine molecules between GO layers displays straining and pillaring effects.The diamine molecules act as chains/pillars to strain/pillar the adjacent layers during the Na⁺insertion/extraction,which prevents the volume expansion and self-stacking of GO.The same method was applied to welding diacid molecules(HOOC(CH₂)_nCOOH)between-NH₂ functionalized Ti₃C₂(x DA-Ti₃C₂).The interlayer spacings of x DA-Ti₃C₂ are 1.24,1.30,1.35,1.38 and 1.45 nm,when the length of diacid molecules is different.The diacid molecules between the interlayer of Ti₃C₂also possess straining/pillaring effects.The tendency of Na⁺diffusion dynamics and rate capability for x DM-GO and x DA-Ti₃C₂ increase first and then decrease with the enlargement of interlayer spacing.The Na⁺diffusion dynamics and rate capability for x DM-GO and x DA-Ti₃C₂ display the best value when their interlayer spacings equal0.95 and 1.38 nm,respectively.In summary,the research reveals the influences of interlayer spacing on the ions diffusion dynamics and rate capability of graphene-like materials.Different graphene-like materials own specific interlayer spacing for achieving the best ions diffusion dynamics and rate capability.In addition,the molecular welding was designed to controllably tune the interlayer spacing of graphene-like materials,and the universality of this method was also verified.The research provides a novel direction for controllably tuning the interlayer spacing of other graphene-like materials.