A synthesis strategy of 3D carbon nanosheet anode with adsorption/intercalation-filling hybrid mechanism for high-performance sodium/potassium-ion batteries.

The waste cooking oil is upcycled into N-doped carbon nanosheets, enabling fast Na+/K+ storage by means of surface charge modulation. [Display omitted] • Waste cooking oil was selected as precursor to prepare hard carbon anode materials. • NWCOC650 takes on a porous nanosheet structure with turbo layers. • NWCOC650 has a coexistence storage mechanism of adsorption/intercalation-filling. • Head group (–NH 2) can produce a synergistic effect with N-5/6/Q and graphene. • NWCOC650 exhibits excellent performances for sodium/potassium-ion batteries. Hard carbons are significant in sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). However, the structural defects of hard carbons lead to poor rate performance and cycling stability, which need further improvement. The waste cooking oil was used as the precursor to synthesize 3D carbon nanosheets (NWCOC) with amino nitrogen functional groups, multi-layered pores, and expanded interlayer spacing. The excellent electrochemical properties of NWCOC were investigated and it was demonstrated that NWCOC can significantly improve the adsorption of Na+/K+ on hard carbons, substantially enhancing the embedding/de-embedding of Na+/K+, reducing the diffusion distance of ions and electrons, and improving their adaptability to volume changes. In situ XRD and Raman characterization reveal that the Na storage mechanism of NWCOC is mainly based on adsorption/intercalation-filling. Combined with density functional theory, it is shown that the porous structures doped with nitrogen have a greater propensity for ion adsorption, resulting in increased ion capture and storage. As expected, NWCOC650 exhibits high capacities of 489.4 and 388.3 mAh/g in SIBs and PIBs. NWCOC650 displays superior performance in the Na 3 V 2 (PO 4) 3 /NWCOC650 full cell, achieving a capacity of 107.84 mAh/g. This work presents a new perspective on the synthesis and mechanisms of high-performance anodes for SIBs and PIBs. [ABSTRACT FROM AUTHOR]