The electrochemical reactions of SnO₂ with Li and Na: A study using thin films and mesoporous carbons

In this work we have determined the room temperature electrochemical reactions of SnO₂ thin films and mesoporous carbons filled with SnO₂ anodes with Na, and compare the results with those obtained during the reaction with Li. We show that SnO₂ can reversibly deliver up to 6.2 Li/SnO₂ whereas the reaction with Na is significantly limited. The initial discharge capacity is equivalent to less than 4 Na/SnO₂, which is expected to correspond to the formation of 2 Na₂O and Sn. This limited discharge capacity suggests the negative role of the formed Na₂O matrix upon the reversible reaction of Sn clusters. Moreover, the reversible cycling of less than 1 Na/SnO₂, despite the utilization of 6-7 nm SnO₂ particles, is indicative of sluggish reaction kinetics. The origin of this significant capacity reduction is probably due to the formation of a diffusion limiting interface. Furthermore, there is a larger apparent hysteresis compared to Li. These results point to the need to design composite structures of SnO₂ nanoparticles with suitable morphological and conductivity components.