Unveiling the triple enhancement mechanism of phosphorus doping: a carbon cathode with a precise mesoporous structure for advanced zinc-ion energy storage

Abstract

The development of high-performance carbon-based cathodes for zinc-ion hybrid capacitors (ZIHCs) is often constrained by a fundamental trade-off between high specific surface area and structural stability. To address this challenge, a synergistic strategy combining precise pore-structure regulation via molecular self-assembly with in situ phosphorus anchoring was used, yielding phosphorus-doped starch-derived porous carbon (SPC-6-20) with exceptional structural robustness. Specifically, CTAB template self-assembly created a hierarchical pore architecture with 98.6% mesopores narrowly distributed between 2–4 nm. Concurrently, 2.77 at% phosphorus was firmly anchored in the carbon matrix via stable P–C and P–O covalent bonds. The resulting material delivers outstanding electrochemical performance: 216.9 mAh g⁻¹ at 0.2 A g⁻¹ and 91.5 mAh g⁻¹ at 40 A g⁻¹. The assembled ZIHC device exhibits an ultra-long cycle life, with 97.86% capacity retention after 60 000 cycles. Mechanistic studies reveal that n-type doping enhances the electrical conductivity, while in situ Raman spectroscopy directly confirms the reversible coordination between P–O⁻ groups and Zn²⁺ ions. This work provides a new paradigm for advanced ZIHC cathode design and fundamental insights into heteroatom doping mechanisms.