Preparation And Electrochemical Properties Of High-capacity Glucose-based Hard Carbon Anode Materials

As a lithium-ion anode material,hard carbon has high gram specific capacity,excellent rate performance and low temperature performance,and at the same time,because of its low cost and wide range of sources.It has received extensive attention and research in the scientific and industrial circles.However,the current hard carbon anode materials still have the problems of low coulombic efficiency for the first cycle,which seriously affect their industrial application.In this paper,the glucose-based hard carbon precursor was prepared by a simple hydrothermal reaction using cheap glucose as raw material,and the glucose-based hard carbon anode material was prepared through subsequent coke removal and carbonization heat treatment.The effects of decoking carbonization process and pre-lithiation treatment on the structure and electrochemical properties of hard carbon anode materials were investigated.The specific research contents and results are as follows:(1)Using glucose as raw material,a glucose-based hard carbon precursor with microsphere morphology was prepared by a simple hydrothermal method,and the glucose-based hard carbon negative electrode material was prepared after subsequent coke removal and carbonization treatment.The results show that the glucose-based hard carbon anode material still maintains the microsphere morphology of the precursor,and the particle size is about 3-5 μm.Through orthogonal experimental design,the effects of coke removal and carbonization of glucose-based hard carbon precursors on the structure and electrochemical properties of the materials were studied.For the discharge capacity of glucose-based hard carbon anode materials,the most important Process condition is carbonization temperature,followed by heating rate,carbonization time and decoking time;For the first coulombic efficiency of glucose-based hard carbon anode materials,the most important Process condition is carbonization time,followed by coke removal time,carbonization temperature and heating rate.The optimal coke removal and carbonization process was as follows:firstly,the temperature was raised from room temperature to 300 ℃ at a heating rate of 1 ℃/min,and then the coke removal was maintained for 2 h,and then the temperature was raised to 900 ℃ for 3 h at a heating rate of 5 ℃/min.The glucose-based hard carbon anode material obtained under the optimized conditions showed good electrochemical performance,at 37.2 mA/g,the first discharge capacity and coulombic efficiency were 569.4 mAh/g and 67.4 %,at 186 mA/g,the first discharge capacity and coulombic efficiency are 489.4 mAh/g and 65.9 %,respectively;at 372 mA/g,the first discharge capacity and coulombic efficiency are418.2 mAh/g and 67.2 %,(2)In order to further improve the first coulombic efficiency of the glucose-based hard carbon anode material,self-discharge and electrochemical pre-lithiation were performed on the electrode sheet.The results show that both self-discharge and electrochemical pre-lithiation treatments can form a stable electrode interface on the surface of the hard carbon anode in advance,thereby reducing the lithium loss in the first cycle and improving the first coulombic efficiency.The first coulombic efficiencies of the hard carbon anode after self-discharge pre-lithiation for 45 min are 96.5 % and 98.9 % at 37.2 and 74.4 mA/g.The performance of the hard carbon anode after electrochemical pre-lithiation treatment is similar to that of the hard carbon anode after self-discharge pre-lithiation treatment,the first coulombic efficiency at 37.2 mA/g is 96.7 %,which is much higher than that of hard carbon anodes without prelithiation...