Preparation Of CU-SNO2 Composites And Their Lithium Storage Properties

With the advantages of high energy density,long cycle-life,environment friendly and safety,lithium ions batteries are dominating people's social production activities profoundly.However,with poor theoretical capacity of 370 mAh/g,the traditional commercial battery anode material of graphite is difficult in adapting to the requirement of portable devices,electric vehicles and large-scale storage in recent years.Therefore,the development of next-generation lithium-ion battery with higher capacity,safety and environment friendly is extremely necessary.Among many alternatives for graphite,tin oxide based material has attracted extensive attention due to its high theoretical specific capacity and rich storage.However,its problems of poor conductivity and huge volume expansion/contraction during the Li+insertion/extraction reaction are the essential factors that limit the application.Nowadays,in order to resolve these deficiencies,many studies have devoted to improve the conductivity and buffer the volume expansion by doping the second type of inert metal or providing a buffer zone through growing buffer matrix.The common method is hydrothermal reaction though,the flaws of low productivity,process-complicated and unmanageable make it impossible to satisfy the large-scaled applications.Based on these issues,we prepared the Cu-SnO₂ composites applied as lithium ions battery negative material by ball milling,followed with oxidation and selective reduction process.Ball milling process is simple,which can obtain batches of copper-tin alloy powder.After oxidizing the as-prepared CuSn power,the formed tin oxide can provide lithium storage performance.The Cu-SnO₂ composite with three-dimensional?3D?metal cluster conducting architecture is easily achieved through reducing the copper oxide with H2 atmosphere selectively.The research contents as follows:?1?Copper-tin alloys with different atomic proportions of CuxSn5?x=1,2...6?were prepared by ball milling for 50 hours.The results of XRD showed that the Cu6Sn5 alloy phases were achieved.The Sn-riched composite is also formed,which depends on the content of Cu in all ball milled component.Six kinds of Cu-Sn02 composites were prepared by oxidation at 700? and reduction at 250?.The SEM analyses illustrated that the morphology after reduction changes from microscopic pores to micropore structure due to the agglomeration of small particles.By contrast,the Cu6Sns based material show the best performance after testing with assembled batteries.?2?In order to enhance the performance of Cu-SnO₂ electrode,we controlled the oxidation and reduction temperature of Cu6Sns alloy.There was incomplete oxidation at 700? and the presence of SnO could put the electrode material in a favorable position during lithiation reaction.?3?The reduction reaction at different temperatures were carried out.The figure of XRD explained that the tin oxide has been reduced when the reduction temperature was above 300?.The Cu-SnO₂-based composite prepared at 250? had an unique morphology of 400 nm cooper constitutes three dimensional?3D?metal cluster conducting architecture,which can effectively buffer the volumetric expansion during charging and discharging process 'and improve the electrode conductivity.After the 200th charge-discharge cycle,the specific discharge capacity retained 536.1 mAh/g,which was higher than the theoretical capacity of commercial graphite.