Homologous Nitrogen-Doped Hierarchical Carbon Architectures Enabling Compatible Anode and Cathode for Potassium-Ion Hybrid Capacitors

Coordination engineering of single zinc atoms on hierarchical dual-carbon for high-performance potassium-ion capacitors

Dual-carbon engineering combines the advantages of graphite and hard carbon, thereby optimizing the potassium storage performance of carbon materials. However, dual-carbon engineering faces challenges balancing specific capacity, capability, and stability. In this study, we present a coordination engineering of Zn-N₄ moieties on dual-carbon through additional P doping, which effectively modulates the symmetric charge distribution around the Zn center. Experimental results and theoretical calculations unveil that additional P doping induces an optimized electronic structure of the Zn-N₄ moieties, thus enhancing K⁺ adsorption. A single-atom Zn metal coordinated with nitrogen and phosphorus reduces the K⁺ diffusion barrier and improves fast K⁺ migration kinetics. Consequently, Zn-NPC@rGO exhibits high reversible specific capacities, excellent rate capability, and impressive cycling stability, and remarkable power and energy densities for potassium-ion capacitors (PICs). This study provides insights into crucial factors for enhancing potassium storage performance.

Rationally Tailoring Superstructured Hexahedron Composed of Defective Graphitic Nanosheets and Macropores: Realizing Durable and Fast Potassium Storage

Multipores engineering composed of micro/mesopores is an effective strategy to improve potassium storage performance via providing enormous adsorption sites and shortened ions diffusion distance. However, a detailed exploration of the role played by macropores in potassium storage is still lacking and has been barely reported until now. Herein, a superstructure carbon hexahedron (DGN-900) is synthesized using poly tannic acid (PTA) as precursor. Due to the spatially confined two-step local contraction of PTA along different directions and dimensions during pyrolysis, defective nanosheets with macropores are formed, while realizing a balance between defects content and graphitization degree by regulating temperature. The presence of macropores is conducive to accelerating electrolyte ions rapid infiltration within electrode, and its pore volume can accommodate electrode structure fluctuation upon cycling, while the most suitable ratio of defects to graphitic provides rich ions adsorption sites and sufficient electrons transfer channels, simultaneously. These advantages enable a prominent electrochemical performance in DGN-900 electrode, including high rate (202.9 mAh g^-1 at 2 A g^-1 ) and long cycling stability over 2000 cycles. This unique fabrication strategy, that is, defects engineering coupled with macropores structure, makes fast and durable potassium storage possible.