Insight into the Effects of Operation Temperature on the Electrochemical Reactions of SnO2 as an Anode in Sodium-Ion Batteries

The operation temperature is one of the key factors affecting the electrochemical reactions and further performances of secondary-ion batteries. In this work, the electrochemical reactions of the SnO2 nanoparticles supported on reduced graphene oxide (SnO2/rGO) as an anode in sodium-ion batteries at the operating temperatures from 10 to 50 degrees C are systematically investigated. It is illustrated that the alloying reaction between metallic Sn and Na+ is hard to take place at relatively lower temperature (10 degrees C), and there is dead tin accumulated at relatively high temperature (50 degrees C) during sodiation/desodiation, which results in the lower specific capacity of SnO2/rGO for sodium storage. The reason why the alloying reaction takes place hardly at low temperature is mainly attributed to the severe polarization of electrodes, but not the low diffusion coefficient of Na+ within tin. The formation of dead tin at 50 degrees C arises from the agglomeration of larger SnO2 nanograins in which the Sn generated during the sodiation cannot be fully oxidized during the following desodiation process forming finally the dead Sn after long-term cycling.