SnO₂ as Advanced Anode of Alkali-Ion Batteries: Inhibiting Sn Coarsening by Crafting Robust Physical Barriers, Void Boundaries, and Heterophase Interfaces for Superior Electrochemical Reaction Reversibility

Superior reaction reversibility of electrode materials is urgently pursued for improving the energy density and lifespan of batteries. Tin dioxide (SnO₂) is a promising anode material for alkali-ion batteries, having a high theoretical lithium storage capacity of 1494 mAh g⁻ based on the reactions of SnO₂ + 4Li⁺ + 4e⁻ ↔ Sn + 2Li₂O and Sn + 4.4Li⁺ + 4.4e⁻ ↔ Li_4.4Sn. The coarsening of Sn nanoparticles into large particles induced reaction reversibility degradation has been demonstrated as the essential failure mechanism of SnO₂ electrodes. Here, three key strategies for inhibiting Sn coarsening to enhance the reaction reversibility of SnO₂ are presented. First, encapsulating SnO₂ nanoparticles in physical barriers of carbonaceous materials, conductive polymers or inorganic materials can robustly prevent Sn coarsening among the wrapped SnO₂ nanoparticles. Second, constructing hierarchical, porous or hollow structured SnO₂ particles with stable void boundaries can hinder Sn coarsening between the void-divided SnO₂ subunits. Third, fabricating SnO₂-based heterogeneous composites consisting of metals, metal oxides or metal sulfides can introduce abundant heterophase interfaces in cycled electrodes that impede Sn coarsening among the isolated SnO₂ crystalline domains. Finally, a perspective on the future prospect of the structural/compositional designs of SnO₂ as anode of alkali-ion batteries is highlighted.