Study On Synthesis Of Antimony-based Carbon Composites And Their Properties For Lithium/sodium Storage

With the increasing conflict between the world’s energy demand and the growing depletion of fossil fuels,the flexibility lithium/sodium ion batteries with high energy density have become one of the main options for integrating renewable energy into the grid.The anode material plays a significant role in lithium or sodium ion batteries and it largely determines the overall performance of the battery.Antimony-based anode materials have great potential for commercial application because of their suitable embedded lithium/sodium voltage,low price,high theoretical capacity and good electrical conductivity.Therefore,in this thesis,the lithium/sodium storage performance of different antimony-based compounds was investigated in terms of metal particle nanosizing,pore structure modulation and carbon coating as follows.（1）The Sb@rGO@NSC composites were prepared by simple deposition method as well as hydrothermal method by anchoring ultrafine antimony nanoparticles on nitrogen and sulfur double-doped porous carbon.XRD,Raman,SEM,TEM,and the nitrogen adsorption and desorption tests show that Sb@rGO@NSC composites have suitable pore size for lithium ion transport,stable and excellent conductive network and other characteristics increase the wettability of electrolyte and material to ensure that ions and electrons can be reciprocated in the composites for rapid transport;smaller size of Sb nanoinions can effectively shorten the transport path of lithium ions.The synergistic effect of the two improves the reaction kinetics of the composite,which in turn enhances the electrochemical properties of the composite.Sb@rGO@NSC-0.3composite holds a high discharge capacity of 721.1 mAh/g at a high current density of1 A/g after cycling for 1000 times;It has an energy density of 259.7 Wh/Kg when assembled as a negative electrode into a lithium ion full battery.（2）The nitrogen-doped WSC@NaSbS₂ composites were prepared by freeze-drying and high-temperature heat treatment techniques using water-soluble coal pitch and carbon nanotubes as carbon sources.The results of XRD,Raman,SEM,and nitrogen adsorption and desorption tests show that the composite has many macroporous structures,and the surface with a graphene-like thin carbon layer structure also facilitates the storage of lithium ions,and it has a reversible capacity of 1076.2mAh g^-1 after 250 cycles at a current density of 0.1 A/g.（3）The nitrogen-doped MFC@SbPO₄ composites were prepared by a simple water bath method.XRD,Raman,SEM,TEM,XPS,nitrogen adsorption and desorption tests,and TG tests show that the carbon layer skeleton composed of graphene oxide and dense amine resin uniformly supports the ultrafine SbPO₄nanoparticles with unique physicochemical properties,which not only avoids agglomeration of bare SbPO₄ particles,but also effectively inhibits the volume expansion of the active material SbPO₄ particles during sodium storage,which in turn improves the sodium ion diffusion capacity.The sodium ion half-cell was assembled with MFC@SbPO₄-0.5 composite as working electrode,and it has a high specific capacity of 270 mAh/g after 2000 cycles when the current density is 1000 mA/g.