Sodium storage of -Sn/TiO2/Sn/TiO2- Superlattice heterojunctions

Electrochemistry of heterostructures plays a fundamental role in developing high-performance energy storage and conversion devices. However, current superlattice heterostructures based on assembling 2D materials are limited to a small number of alternating units with weak interfacial interaction and ambiguous function mechanism. Herein, the high-order -Sn/TiO₂/Sn/TiO₂- (S/TO) superlattice heterojunctions with built-in electric fields (BIEFs) are designed for sodium storage using a strain release method. The results show that the accommodated BIEFs and the spatial confinement effect in this periodic nanostructured electrode co-contribute to the outstanding electrochemical performance. The nanosizing and pulverization of Sn are effectively space-limited in between the TiO₂ slabs and the notorious catalytic reaction between electrolyte and TiO₂ surface region is sophisticatedly mitigated by the electron accumulation in the TiO₂ component, synergistically accelerating sodium storage and transfer kinetics of S/TO superlattice electrodes. The covalent Sn-O-Ti interactions further enhance the robustness to sustain repeated (de)sodiation processes. These findings provide a rewarding avenue towards the development of high-performance electrodes by heterostructural electrochemistry.