Unleashing Anion Chemical Adsorption with Pore-Confined Single Atom Zinc for Enabling High-Performance Lithium-Ion Capacitors

Single-atom metal (SAM) doping of carbon materials shows promise for energy storage applications. However, the design and application of SAMs in high-performance porous carbon (PC) cathodes for lithium-ion capacitors (LICs) remain less explored. This study focuses on confining SAMs within the pores of PC cathodes and investigating their influence on the anion adsorption behavior. We propose a sustainable "pore-making-doping" strategy to create Zn atom-doped PC (PCNM-Zn). Zn atoms are confined within mesopores with an average diameter of 3.64 nm, forming a Zn-O-4 configuration. The X-ray absorption fine structure spectra and density functional theory calculations reveal that PF6 - anions chemically adsorb onto Zn atoms, forming Zn-O-4-F-3 configurations that enhance the adsorption energy of PF6 (-). Consequently, the presence of Zn atoms improves the reversible capacity and rate performance for anion adsorption/desorption. PCNM-Zn exhibits a specific capacity of up to 130 mAh/g at 0.1 A/gand 95 mAh/g even at 10 A/g. Conversely, the removal of Zn atoms significantly reduces the capacity and rate performance. A symmetric PCNM-Zn//PCNM-Zn full cell demonstrates an operating voltage of 4.5 V, a high energy density of 182.3 Wh/kg, and a high power density of 22.5 kW/kg. These findings highlight the promising prospects of SAMs as cathodes for high-performance LICs.