Preparation And Sodium-storage Performance Of Wheat Bran-derived Carbon Materials

Sodium-ion batteries(SIBs) are known as the most promising candidate for Lithium-ion batteries.However,sodium-ion has larger ionic radius and higher standard electrode potential than lithium-ion,which make it difficult to find a suitable anode material.Carbon plays a significant role in energy storage electrodes.In particular,biomass-derived carbon(BDC)materials have become the most commercially promising material for Sodium-ion batteries due to the low cost,environment-friendly and renewable.But how to improve the yield and Initial Coulombic Efficiency are open problems.In this paper,wheat bran was selected to be biomass precursor,and the BDC materials with different structures were obtained by high-temperature carbonization,ball-milling activation and heteroatom doping.We aim to find a suitable anode material for Sodium-ion batteries by a simple and energy-efficient synthetic method.(1)By Comparing the sodium storage performances of the BDC materials prepared by high-temperature carbonization and ball-milling activation,we found the latter is better.Ball-milling activation prepared the BDC materials through high-energy ball milling and KOH activation.When the mass ratio of KOH to precursor material is 2:1,a structure with small particles and multi-channels is obtained.The structure is beneficial to the transmission of sodium ions,and not easy to be damaged by the expansion and shrink due to the deintercalation of sodium ions.The reversible capacity is about 325 m Ah/g at 50 m A/g.Therefore,the material shows a good sodium storage performance.The material with irregular particles prepared by high-temperature carbonization at 1000℃ has the best performance through this method.After 100 cycles,the specific reversible capacity only delivers 120 m Ah/g at 50 m A/g;(2)The electrochemical performance of BDC materials prepared by N-doping and S-doping were compared,and the latter is better.The N-doping BDC material was prepared by a simple carbonization with melamine,which exhibits an aggregated foam-like structure.The specific capacity delivers 245 m Ah/g at 50 m A/g.But the stability is poor,and the capacity is below 100 m Ah/g after 100 cycles;Sulfur powder was served as sulfur source in the preparation of S-doping BDC material,which exhibits an irregular structure.Sulfur atoms expand the carbon layer spacing and cause more defects.Therefore,the active material shows an excellent sodium storage performance,which delivers a high specific capacity of 487 m Ah/g at 50 m A/g,and the Initial Coulombic Efficiency reaches 70%.The sodium storage performance is more prominent than the BDC materials in previous reports.