Comparing cycling and rate response of SnO₂ macroporous anodes in lithium-ion and sodium-ion batteries

Tin oxide (SnO₂) is a useful anode material due to its high capacity (1493 mAh g⁻¹ and 1378 mAh g⁻¹ vs Li/Li⁺ and vs Na/Na⁺, respectively) and natural abundance (tin is one of the thirty most abundant elements on Earth). Unfortunately, only moderate electrical conductivity and significant volume expansion of up to 300% for Li-ion, and as much as 520% for Na-ion can occur. Here, we use an ordered macroporous interconnected inverse opal (IO) architectures to enhance rate capability, structural integrity, and gravimetric capacity, without conductive additives and binders. Excellent capacity retention is shown during cycling vs Na/Na⁺ relative to Li/Li⁺. Cyclic voltammetry (CV) analysis, galvanostatic cycling, and differential capacity analysis extracted from rate performance testing evidence the irreversibility of the oxidation of metallic Sn to SnO₂ during charge. This behavior allows for a very stable electrode during cycling at various rates. A stable voltage profile and rate performance is demonstrated for both systems. In a Na-ion half cell, the SnO₂ retained >76% capacity after 100 cycles, and a similar retention after rate testing.