Fabrication And Electrochemical Performance Of Carbon-based Anode Materials For Lithium/Sodium Ion Batteries

Due to the rapid development of portable electronic devices,electric vihicles and energy storage station,advanced lithium-ion batteries?LIBs?should be further developed.However,traditional anode material,like graphite,can not meet the demand of the developmemt of lithium-ion batteries because of the limit theoretical capacity(372 mA h g^-1)and the poor rate capability.In addition,the limited content and high cost of lithium resource hinder the future of LIBs.Therefore,exploring advanced anode materials for LIBs or developing alternative battery systems have become research hotspots.Silicon has been considered as an ideal candidate anode material for LiBs due to the superior high capacity(⁴200 mA h g^-1).In addition,benefiting from abundant resources reserve and similarities in the chemical properties between sodium ions and lithium ions,sodium-ion batteries?NIBs?are going on fast development as alternatives to LIBs.Among various anode materials,carbon-based anode materials are regard as the most promising anode material for LIBs or SIBs because of the low-cost,high conductivity and structurally controlled properties.In this thesis,we studied and prepared the high performance carbon-based anode materials for LIBs/NIBs.The main results are as follows:1.Graphite/silicon composite anode material is prepared by mixed with expanded graphite and a small amount of nano-silicon,further coated with pyrolytic carbon using pitch as a precusor.The composite material shows the improved electrochemical performance as anode material for LiBs,indicates the pyrolytic carbon strengthen the connection between silicon and expanded graphite matrix.The composite exhibits initial coulombic efficiency of 74%and the high reversible capacity(540 mA h g^-1)at a low current density of 0.1 A g^-1,239 mA h g^-11 at high current density of 1.6 A g^-1.Forthermore,after 100 cycles at current density of 0.4 A g^-1,the electrode remains a reversible capacity of⁴50 mA h g^-1.2.A 3D amorphous carbon?3DAC?is fabricated by a NaCl template method from low-cost pitch and phenolic resin.Due to the controlled introduction of the porosity and more disordered microstructure,3DAC exhibits a relatively high initial Coulombic efficiency?75%?,high reversible capacity(280 mA h g^-1 at 0.03 A g^-1),and excellent rate capability(66 mA h g^-1 at 9.6 A g^-1).These results indicate that the microstructure is a key factor which can affect the electrochemical performance of carbon-based anode materials for SIBs.3.A series of amorphous carbon?AC?are fabricated from a mixture of pitch and phenolic resin.The microstructure of AC is controlled by the variation of oxidative stabilization time,which leads to different electrochemical performances for anode material in SIBs.Furthermore,after oxidative stabilization process,the carbon yield is significant improved,which can reach up to 73%.The optimal sample?20AC?shows a reversible capacity of 262 mA h g^-1,a high initial coulombic efficiency of 81%and good rate performance for SIBs?105 mA h g^-11 at 4C?,which manifests the critical role of microstructure in amorphous carbon on the electrochemical performance.