Optimized Preparation Of Heteroatom-doped Porous Carbon Materials And Their Potassium Ion Storage Propertie

The exploration of high energy density and low cost energy storage system is of great significance.Potassium ion battery has the advantages of low reduction potential and high energy density.Thus,potassium ion storage has the potential advantages of fast kinetics and magnification capacity.Carbon materials have been widely studied in potassium storage due to their abundant raw materials,stable properties and high safety.However,the larger potassium ions cause the volume change and slow kinetics,leading to the severe decay in the electrochemical properties.B and P doping of carbon materials can effectively expand the layer spacing and avoid large structural changes.Doping of pyridine nitrogen can increase the active site and defect to a greater extent,so as to effectively improve the conductivity and ion diffusion rate,optimize the rate performance and long cycle stability.In this paper,three kinds of porous carbon materials with heteroatom doping are synthesized with heteroatom doping as the core and studied the effect of heteroatomic on the electrochemical properties.The main content includes:（1）CdS nanowires as the template were synthesized by hydrothermal method,and polydopamine（PDA）polymerization was constructed on the surface of Cd S nanowires to form the uniform coating.Boric acid and urea were selected as dopants,and a series of tubular porous carbon were calcined by adjusting the ratio of dopants.It was found that the relatively low doping of HCNT-0.3 negative electrode showed the advantage of fast potassium ion storage:Large specific capacity(383 m A h g^-1 at 0.02 A g^-1),greater rate capacity(189 m A h g^-1 at 1.0 A g^-1)and excellent cyclic stability(70%capacity after 500cycles at 1.0 A g^-1).In-situ Raman and ex-situ SEM studies after cycling demonstrated a highly reversible evolution of the G and D bands of HCNT-0.3,confirming the highly reversible structural properties of HCNT-0.3.Electrochemical kinetic analysis showed that the main potassium storage process was capacitor potassium storage and had a higher average K⁺diffusion coefficient.（2）ZIF-67 was used as a precursor to study the effects of different carbonization temperatures（550-650℃）on pyridine nitrogen content and potassium storage performance.The porous carbon NC-600 doped with ultra-high pyridine nitrogen（60.37%of total nitrogen atoms）can be obtained at 600℃.The NC-600 shows high capacity and excellent cycle stability(approximately 92%capacity retention after 500 cycles at 0.1 A g^-1 current density).Meanwhile,NC-600 anode also demonstrate a higher rate capability than other,with a highly reversible capacity of 138 m A h g^-1 at the current density of 1 A g^-1.The high diffusion coefficient(6.43×10^-11)cofirmed that NC-600 with high pyridine processed fast kinetics for large potassium ions.These excellent electrochemical behaviors can be attributed to the high pyridine nitrogen content achieved by the decomposition of 2-methylimidazole at appropriate reaction temperatures.（3）Using SiO₂ as the template and phytic acid as the dopant,nitrogen/phosphorus co-doped hollow bowl porous carbon was synthesized as high performance anode.NPC-2 with high doping phosphorus content shows uniform structure and high specific surface area. The NPC-2 anode can develiver a high capacity of 480 m A h g^-1 after 150 cycles at 0.1 A g^-1 current density.In the high rate capability test,the anode can display a capacity of 565m A h g^-1 when the current density returns to 0.02 m A h g^-1 again.The excellent electrochemical performance is expected to be extended to commercial applications.The porous structure and the large specific surface area ffectively adjust the structural strain and reduce the volume expansion.