Preparation Of Hierarchical Porous Carbon Material And Study On Its Potassium/Sodium Storage Performance And Mechanism

Lithium-ion batteries,as typical commercial secondary battery,play an important role in the current energy storage system market,but their further development is greatly restricted due to its resource shortage,uneven distribution and high price.The sodium,potassium and lithium elements are all alkali metal elements and have similar electrochemical properties.In addition,the use of sodium-ion and potassium-ion batteries will reduce battery costs by about 30%according to preliminary predictions,which makes potassium/sodium-ion batteries the most promising candidate for lithium-ion batteries.As an amorphous carbon material,hard carbon has become a potential anode material for potassium/sodium ion batteries because of its expanded interlayer spacing and enriched microporous structure.In this article,we synthesized sulfur-doped hollow porous hemoglobin-like carbon（SHPHC）using hard template method and spray drying technology,which has a multi-scale,multi-bonded state structure.Through a series of tests and characterization methods,its microstructure was revealed,and its electrochemical performance and sodium/potassium storage mechanism at room temperature and high temperature were also studied.In addition,the influence of sulfur-doped on potassium storage kinetics was further explored by DFT calculation.The main content includes the following parts:（1）Using silica of different sizes as hard templates,a series of sulfur-doped hollow porous hemoglobin-like carbon materials（SHPHC）with different pore sizes were synthesized by spray drying technology.In order to further study the influence of the template ratio on the structure and performance of the material,taking 80 nm silica as an example,sulfur-doped hollow porous hemoglobin-like carbon with more abundant pores under different template ratios were synthesized.Then we performed a series of tests to analyze the structural characteristics,element content and bonding state of the material.（2）The electrochemical performance of the SHPHC material as the anode material of the potassium ion battery at room temperature was studied.It was found that SHPHC-80 had an excellent performance.It had a high reversible specific capacity of 347.6 m Ah g^-1 after 350cycles at a current density of 500 m A g^-1.Even at a high current density of 10 A g^-1,the specific capacity of 166.4 m Ah g^-1 could still be released even after 6900 cycles,showing an ultra-long cycle life and excellent rate performance.Such an excellent performance was benefited from our well-designed hollow porous structure and sulfur doping,which enhanced the electronic conductivity of the material and expanded the interlayer spacing,providing more K⁺storage sites.This paper also revealed that the K⁺storage mechanism of SHPHC-80 material was the joint control of surface adsorption and diffusion.Between them,the surface adsorption was dominant.Prussian blue was utilized as the cathode material to form a full battery,which had a good matching performance and showed a high specific capacity of 110.1 m Ah g^-1 at a current density of 100 m A g^-1 for 85 cycles.Furthermore,DFT calculations showed that sulfur doping could reduce the surface migration barrier of K atom.（3）We also studied the Na⁺storage performance of the SHPHC-80 material at room temperature and high temperature,and the full battery performance at room temperature.Exploring the kinetics of sodium storage at high and normal temperatures,it was found that SHPHC-80 materials still had excellent electrochemical performance at high temperatures and could adapt to more severe environments.