Study On Synthesis Of SnO₂ Composite And Its Application

With the advantage of low charge/discharge potential platform?⁰.6 V?,perfect safety,higher theoretical specific capacity?782 mA h g-1?and fast electron mobility which is much higher than other n-type semiconductors,SnO₂ has been one of the potential candidates of lithium-ion battery anode material.But low conductivity and columbic efficiency of first charge/discharge progress,large volume expansion which makes the active material exploited from current collector limit its application as anode material of lithium-ion battery.Meanwhile,the forming of metal tin will agglomerate seriously during insertion/extraction of lithium-ion,this will also result in the decay of capacity.In this paper,LiSn2?PO4?3,SnO₂/C composite and SnO₂@C composite were investigated to solve the problem of SnO₂ electrode above.LiO₂ is the buffer matrix for metal tin during the charge/discharge progress of SnO₂ electrode.As the low conductivity and limit capability of LiO₂,LiSn2?PO4?3 whose buffer matrix is Li3PO4 was prepared by solid-state method.SnO₂ nano-particle was prepared by hydrothermal process and used as the precursor of fabricating rhombohedral structure single crystal LiSn2?PO4?3.XRD?TEM and SEM method were used to characterize the morphology and lattice structure.Compared with SnO₂ electrode,LiSn2?PO4?3 electrode presents much better in electrochemical performance.LiSn2?PO4?3 retain 88% of the entail capacity which is much higher than SnO₂ nano-particle when charging/discharging at current density of 100 mA g-1,which indicates that the structure of material is protected well and this will be meaningful to solve tin based electrode to some extent.Hierarchical hollow flower-like SnO₂ was prepared by hydrothermal process and the effect of the concentration of SnCl4 on morphology and electrochemical performance of materials was studied.SnO₂/C composite was synthesized to solve the difficulty caused by poor conductivity and instability of structure.SEM,TEM,XRD,constant current charge/discharge and CV technology were used to characterize the physical and electrochemical property.Modified SnO₂ by combining the SnO₂ prepared in the optimal situation with amorphous carbon.At current density of 200 mA g-1,SnO₂/C composite electrode exhibits 346.1 mA h g-1 after 50 charge/discharge cycles which is much higher than hollow SnO₂ electrode.All these results indicate that the electrochemi-cal performance of as-prepared SnO₂/C composite is improved by introducing amorphous carbon.In order to enhance the conductivity of SnO₂,hydrothermal process and solid-state method were used to fabricate the carbon coating SnO₂@C composite.The results show that composite prepared by hydrothermal process could retain 245.3 mA h g-1 after 50 cycles while 230.1 mA h g-1 is for composite prepared by solid-state method under the same charge/discharge condition.The content of carbon was calculated by differential thermogravimetry.XRD?SEM and Raman spectrum were used to characterize the morphology,inside construction and the existence of carbon.