Carbons Derived From Coal Based Amphiphilic Carbonaceous Material And Their Lithium/Sodium Storage Performances

Due to its unique micro-structure,hard carbon(HC)is a strong competitor for the next generation lithium ion battery(LIB)anode,and it is also an advantageous option for the sodium ion battery(SIB)anode.It is of great significance to explore the cheap and readily preparation technology for the industrialization of HC anodes.And among many raw materials for carbon materials,heavy organics have always been the focus of researchers'attention due to their high carbon content,low cost,and abundance.The coal liquefaction residue(CLR)is a by-product of the coal liquefaction process,which call for an efficient and rational utilization urgently.This hydro-treated mixture is rich in polycyclic aromatic hydrocarbons and their derivatives,with high and widely distributed molecular weight,is an excellent carbon materials precursor.The current dissertation proposed a novel strategy for HC preparation via amphiphilization-carbonization of the heavy organics of CLR,and the performances of HCs and their composites as anode materials for LIBs/SIBs have been investigated.The main contents are as follows.Regarding the complex composition,high and widely distributed molecular weight and high graphitization tendency of the heavy organic matters,firstly,a method of mixed acid oxidation was used to treat heavy organic matters to prepare amphiphilic carbonaceous materials(ACM)ACM-TX,in this work.XRD,elemental analysis,infrared analysis,Raman spectroscopy,XPS,and ~1H-NMR analysis were used to characterize the ACM and the heavy organics of CLR,and a possible formation mechanism of ACM was deduced thereby.Then,a series of ACM-TX-T HCs was prepared by carbonization of ACM-TX in the range of 700°C to 1600°C.The micro-structure,the elemental composition and the specific surface area of HCs was characterized by XRD,Raman,elemental analysis,and N2 adsorption,and the lithium/sodium storage properties were studied.In order to study the mechanism of sodium storage,a relationship between the sodium storage performance and the structural parameters of the ACM-TX-T series HCs was established via mathematical fitting.It is considered that the low-voltage plateau capacity of HC anode stemmed from the interlayer storage of sodium in the quasi-graphitized zone in HC.The actual rate performance was evaluated by a three-electrode electrochemical system,and the proposed mechanism of sodium storage was verified further.At last,a full cell composed by ACM-TX-1200 and Sodium vanadium phosphate(NVP)cathode exhibits not only a voltage platform of 3.3 V during charge and discharge,which is similar to the iron phosphate-based lithium-ion batteries,but also a high energy density and an outstanding rate performance.