Preparation And Lithium-ion Batteries Anode Properties Of Spherical Stannic Oxide-Low-Dimensional Carbon Composite

Due to the high theoretical capacity of SnO₂as negative electrode materials ofLi-ion battery, SnO₂has attracted much attention. However, if SnO₂was used to benegative electrode materials of commercial Li-ion battery, it had a few barriers. Onthe one hand, the poor electronic conductivity of SnO₂enhances the internal resistanceof battery. On the other hand, during charge-discharge process, insertion andextraction of Li-ion are likely to cause strong volume change and high internal stressof negative electrode material, which lead to breakdown and disconnection ofnegative electrode materials. To prepare special structures of SnO₂and composites ofSnO₂and carbon materials, using various excellent characters of them solve theproblems to solve/remit the problems from being negative electrode material.Graphene and carbon nanotube have application prospect at different fields of storageequipment. They are good matrix of SnO₂because of high conductivity and specialstructures.In this paper, the surface of SnO₂hollow sphere prepared through hydrothermalmethod was modified by APS. Then the APS-modified SnO₂hollow sphere wasencapsulated by graphene sheet or carbon nanotube, which gained the composite ofSnO₂hollow sphere and graphene sheet/carbon nanotube. Comparing with commonSnO₂, SnO₂hollow sphere have preferably good cycle performance. After SnO₂hollow sphere was encapsulated by graphene sheet/carbon nanotube, its cycleperformance and electrochemical performance were obviously enhanced. Concretecontent as follows:（1）In the alkaline environment of urea, SnO₂hollow sphere was synthesized byhydrothermal method, potassium stannate as precursor and ethanol solution as solvent.The first invertible capacity of SnO₂hollow sphere was1028mAh/g, higher thancommon SnO₂（800mAh/g）, at electric current density of156mA/g. It showedexcellent cycle performances over more electric current density.（2） At first, we selected SnO₂hollow sphere that had appropriate size and highelectronic performance. The SnO₂hollow sphere was modified by APS. ThenAPS-modified SnO₂hollow sphere and graphene self-assembled through theelectrostatic interaction of them, which obtained graphene-encapsulated SnO₂hollowsphere. When mass ratio of the composite was83%, the first invertible capacity was only924mAh/g at electric current density of156mA/g, but the30th invertiblecapacity was788mAh/g. It showed excellent cycle performances over more electriccurrent density.（3）The size choice and surface modification of SnO₂hollow sphere were the sameas （2）. In the air atmosphere and acid solvent, APS-modified SnO₂hollow sphere andcarbon nanotube activated by strong acid were simply stirred to gain carbonnanotube-encapsulated SnO₂hollow sphere. When mass ratio of the composite was71%, the first invertible capacity was995mAh/g at electric current density of156mA/g and the30th invertible capacity was653mAh/g. It showed excellent cycleperformances over more electric current density.