Interface Structure Design And Studies Of Tin Oxide Composites As Lithium-ion Battery Anodes

The rapid development of electric vehicles and portable electronic devices increases the demand for high-energy density lithium ion batteries.High-capacity electrode materials is one of the important approach to increasing the specific energy of lithium-ion batteries.Among many anode materials,tin dioxides have received extensive attention because of their high theoretical capacity.The capacity of tin dioxide is provided by a two-step reaction.The first step is the conversion reaction of tin dioxides,and the second step is the alloying reaction of tin metal.Among them,the formation of Li4.4Sn by alloying reaction can provide a capacity of 994 mAh g-1.However,the first-stage conversion reaction has poor reversibility of Li2O,which restricts the cycleability of the conversion reaction,resulting in irreversible capacity loss during the charging and discharging of tin dioxides.Previous studies have reported that the reversibility of Li2O generated during discharge can be improved by doping the transition metal in tin dioxides,but the mechanism of improving the reversibility of the reaction is not revealed yet.In order to design a better lithium ion battery anode,the nano-metal and lithium oxide reaction interface was studied at the atomic scale and a nanoporous manganese-tin binary metal oxide was prepared.The first principle calculation leads to the finding that the Mn/Li2O interface energy is smaller than the Sn/Li2O interface energy,so in the lithium oxide matrix,the nucleation particle size of manganese is smaller than that of tin.Based on this theoretical calculation,we infer that when the designed manganese-tin binary metal oxide is electrochemically cycled as a negative electrode material for lithium ion batteries,the ultrafine manganese nanocrystals formed during lithiation can suppress the grain coarsening of tin during the reaction of the battery,improving the contact interface between tin and lithium oxide promotes the reversible conversion of Li2O.The large amount of manganese-tin interface produced by designing this composite can greatly increase the reversible capacity of tin dioxide during the reaction.Through the corresponding electrochemical performance test,we are able to demonstrate the composite having an initial capacity of up to 1620.6 mAh g-1 at a current density of 0.05 A g-1.Because the presence of manganese inhibits the agglomeration of metallic tin particles,the composite exhibits good cycling properties.Even after 1000 cycles,the nanoframe anode could deliver a capacity of 547.3 mAh g-1 at 2 A g-1.In general,we demonstrate a strategy of nanostructuring interfaces with low interface energy to enhance the Li-ion storage capability of binary tin oxides and revealed the mechanism of property enhancement,which might be applied to analyze other tin oxide composites.The results of this work provide a high-performance anode material and help the in-depth understanding of property enhancement,which may be applied to other composite oxide systems.