Precisely Integrated Mesoporous Anode Enabling Fast Pseudocapacitive Sodium-Ion Storage

Sodium-ion batteries (SIBs) are considered potential alternatives to lithium-ion batteries (LIBs) due to the abundant resources and low sodium cost. The rational nanostructural design for anode materials plays a crucial role in SIBs. TiO2, as a common electrode material, suffers from the drawbacks of low specific surface area and poor conductivity. To overcome these limitations, we propose a strategy combining solvent evaporation-induced self-assembly and chemical oxidative polymerization to construct an ultrathin polypyrrole (PPy)-coated mesoporous TiO2 microsphere (meso-TiO2@PPy) core–shell structure. The combination of the mesoporous structure and the conductive coating endows the micrometer-sized TiO2 spheres with high specific surface area, excellent conductivity, and abundant sodium-ion diffusion pathways, leading to a dominant pseudocapacitance (94%) of total charge storage. Remarkably, such integration allows for a high reversible capacity of 160.6 mAh g–1 at 1 A g–1, good rate performance, and stable cycling performance (capacity retention of 80.8% after 2000 cycles). Our research provides a pathway for the design of compositive anode materials for high-performance SIBs.