Preparation Of Camellia Shell-derived Carbon And Their Electrochemical Properties For Sodium And Potassium Storage

Sodium-ion batteries（SIBs）and potassium-ion batteries（PIBs）are new electrochemical energy devices with great potential to replace lithium-ion batteries（LIBs）.The advancement of suitable anode materials plays an important role in the development of SIBs and PIBs.Hard carbon possesses a disordered structure,larger interlayer spacing and rich defect sites with reference to graphite,which is considered a potential anode material for SIBs and PIBs.Specifically,biomass is widely used as a precursor for hard carbon preparation due to its abundant sources and strong renewability.Camellia shell is a cheap agricultural waste,and using it in the preparation of SIBs and PIBs anode materials will take into account the needs of both cost controllable and biomass solid waste resource utilization.In this work,biomass camellia shell-derived carbon with tailored morphology and internal structure was obtained through hydrothermal and pre-oxidation processes,followed by high-temperature treatment.The electrochemical properties of the biomass camellia shell-derived carbon used as anode material for sodium and potassium storage were tested.The specific work contents are as follows:（1）Porous carbon microspheres（CSHP）were prepared by pulverization,ball milling,and two-step hydrothermal treatment using camellia shells as biomass precursors.The structure of the porous carbon microspheres was characterized by SEM,TEM,Raman and BET methods.It is found that the obtained porous carbon microspheres have a large number of micropores and a large specific surface area.The porous carbon microspheres are used as a negative material for SIBs with a reversible specific capacity of 250 m Ah·g^-1 at 100 m A·g^-1.When used for PIBs,it has a reversible specific capacity of 264.5 m Ah·g^-1 at 100 m A·g^-1,and has good cycling stability,with a capacity retention rate of 89.8%after 100 cycles.Various characterization results collectively confirm that the excellent electrochemical performance of porous carbon microspheres is attributed to their unique carbon sphere structure and abundant micropores.（2）An advanced oxygen-enriched hard carbon was designed and synthesized from camellia shell powder through mild low-temperature pre-oxidation and high-temperature carbonization.Utilizing TEM,SAED,XPS,infrared spectroscopy,and elemental analysis,it is shown that oxygen-containing functional groups（C-O and C=O）can be introduced by pre-oxidation at 200°C,which stabilizes the structure of carbon materials and prevents graphitization during high-temperature carbonization.Pre-oxidation increased the degree of disorder of the biomass camellia shell-derived carbon,increasing more defects and active sites for the electrochemical reaction.Oxygen-rich carbon material derived from camellia shell was used for energy storage as anode materials for SIBs and PIBs,which exhibited reversible specific capacities of282 and 220 m Ah·g^-1 at 100 m A·g^-1,and also exhibited good cycling stability performance.