Regulation of gradient pores and heteroatom-doped sites in carbonaceous cathodes for promoting Zn-ion storage capability

Carbonaceous cathodes with numerous heteroatom-doped active sites and accessible pore structures can effectively boost the charge storage capacity and energy density of carbon-based aqueous zinc-ion capacitors (AZICs). In this study, N/P-doped gradient porous carbon (GCNP) is constructed to increase the Zn ion storage capacity, owing to the abundant N, P, and O heteroatom active sites and unique gradient-pore structure. The gradient porous structure (micropores and mesopores of approximately 1.19 and 2.67 nm) of the GCNP 2 -1 cathode provides rapid ion/electron pathways, promoting Zn ion diffusion and transfer behaviors. Density functional theory calculation reveals that the incorporated N and P functional groups effectively regulate the charge density distribution in gradient porous (micro-mesoporous) carbonaceous structure, thereby enhancing Zn ion adsorption. Consequently, GCNP 2 -1 based AZICs deliver capacities of 218.1 and 112.3 mAh g −1 at 0.2 and 10 A g −1 . Moreover, the GCNP 2 -1 based AZICs exhibit 70.5 % capacity retention after 30,000 cycles at 10 A g −1 , and excellent energy density with 200.1 and 49.4 Wh kg −1 at 0.159 and 31.2 kW kg −1 . This work provides an effective strategy for designing N/P-doped gradient porous carbon cathodes, highlighting the potential for superior Zn ion capacity cathode materials in practical AZICs applications. The objective of this work is to regulate the gradient porous structure (micropores and mesopores larger than 1.19 and 2.67 nm) and N, P-doped groups within gradient porous carbon materials to boost the Zn-ion storage capability and clarify the energy storage mechanism through various ex -situ methods. • The gradient porous structure features rapid charge carrier conduction pathways. • A energy and ultrahigh power density (200.1 Wh kg −1 , 31.2 kW kg −1 ) are obtained. • Ex -situ tests and DFT are used to explore the energy storage mechanism of AZICs.