Modification Of Mesocarbon Microbeads For High Performance Potassium Ion Battery

Graphite has the advantages of low cost and stable discharge platform,which is one of the most promosing anode materials for potassium ion batteries（PIBs）.However,the insertion/extraction of potassium ions causes intense volume change of graphite,and much consumption of electrolyte,thus leading to poor rate performance of graphite.In this paper,a new type of graphitized negative electrode was designed using the coal tar pitch derived mesocarbon microbeads（MCMB）by potassium hydroxide treatment and amorphous carbon coating.The research contents are as follows:Potassium hydroxide treated mesocarbon microbeads.In order to solve the problem of bad rate performance of graphite,herein,the potassium storage performance of MCMB with Brooks-Taylor structure as well as KOH treated MCMB were investigated.After KOH treatment,the surface of MCMB was slightly oxidized and an expanded layer with enlarged interlayer spacing formed,which significantly improves the potassium ion diffusion rate.As a result,the modified MCMB act as high-performance anodes for PIBs in terms of superior rate capabilities(160 m Ah g^-1 at 1.0 A g^-1),long cycle life(184 m Ah g^-1 at 100 m A g^-1after 100cycles),as well as high initial coulombic efficiency（ICE）（79.2%with CMC as binder）.More importantly,the high graphitization degree of bulk phase was preserved,by which the KOH treated MCMB exhibits a high plateau capacity below 0.25 V(271 m Ah g^-1).These are important to construct PIBs with excellent rate performance and high energy density.Nitrogen-doped amorphous carbon coated mesocarbon microbeads.In order to solve the problem of poor negative magnification performance of graphitized carbon,amorphous carbon coated MCMB were obtained with MCMB and dopamine hydrochloride as raw materials.The amorphous carbon significantly improves the potassium ion diffusion rate.As a result,the modified MCMB as anodes for PIBs exhibits superior rate capabilities(109 m Ah g^-1 at 1.0 A g^-1)and high cycling capacity(134 m Ah g^-1 at 100 m A g^-1after 100 cycles).Meanwhile,nitrogen-doped amorphous carbon coated MCMB exhibits a high plateau capacity below 0.25V(243 m Ah g^-1).These are important to construct PIBs with excellent rate performance and high energy density.