Synthesis And Potassium Storage Properties Of Hollow Porous Carbon Materials

Potassium-based energy storage devices have become a potential alternative to lithium-based energy storage devices due to the advantages of abundant potassium resources,low K⁺/K standard reduction potential,and fast K⁺mobility in organic solutions.Carbon materials are widely used as anode materials in potassium-based energy storage devices;however,the limited cycle life and multiplicative performance of carbon materials make them have great drawbacks in practical applications.Therefore,by developing hierarchical porous nanostructures and introducing heteroatoms into the carbon matrix,K⁺migration paths can be shortened and redox active sites for K⁺storage can be provided to realize potassium-based energy storage devices with excellent performance.In this paper,efficient potassium storage in spun carbon materials is achieved through strategies such as hollow structure design,heteroatom doping and physical activation as follows:1.Preparation of phosphorus-nitrogen co-doped hollow carbon fibers and study of potassium storage properties:Phosphorus-nitrogen co-doped grape bunch-shaped hollow carbon fibers（P-HCNFs）were prepared by electrostatic spinning technique using Si O₂ as a template.P-HCNFs have a continuous and interconnected cavity structure,which can effectively shorten the K⁺transport path and alleviate the volume expansion.The introduction of P and N atoms can create abundant extrinsic/intrinsic defects and additional active sites,reduce the K⁺diffusion barrier and increase the potassium storage capacity.In half-cell performance tests,P-HCNFs provided a high specific capacity of 310 m Ah g^-1 at 0.1 A g^-1 with high multiplicative performance(140m Ah g^-1 at 50 A g^-1),and at 10 A g^-1 after 10,000 cycles and maintains a stable capacity of 87%.In addition,the assembled P-HCNFs||ACNFs potassium ion hybrid capacitor based on P-HCNFs as the negative electrode and activated carbon fibers（ACNFs）as the positive electrode is able to output a high energy density of 115.8 Wh kg^-1,while having 91%capacity retention after 20,000cycles,which provides a new direction for the development of potassium ion hybrid capacitors.2.Preparation and potassium storage properties of flexible activated carbon fibers:flexible activated carbon fibers（ACF）were obtained by physically calcining in an air atmosphere to activate the formation of pores in spun carbon fibers.The results showed that the carbon fiber（ACF-3.5）calcined for 3.5 hours exhibited a large specific surface area and graded porous structure with abundant nitrogen and oxygen co-doping properties.Electrochemical performance tests showed that ACF-3.5 has a high specific capacity of 363.7 m Ah g^-1 at 0.05 A g^-1 and a capacity retention of 88.5%after 2500 cycles at 1 A g^-1.Compared with commercially available activated carbon,ACF-3.5 has a greater advantage in electrochemical potassium storage performance,laying the foundation for the future development of carbon anode materials for potassium-based energy storage devices.