Electrochemically in situ formed rocksalt phase in titanium dioxide determines pseudocapacitive sodium-ion storage.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40016257.
- Also identified by DOI 10.1038/s41467-025-57310-x and PMC identifier 11868394.
- Licence recorded as CC BY-NC-ND.
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Abstract
Earth-abundant TiO<sub>2</sub> is a promising negative electrode for low-cost sodium-ion batteries (SIBs) owing to its high capacity, rapid (dis)charging capability, safe operation potential and nonflammability. Crystalline anatase TiO<sub>2</sub> is not suitable for reversible Na<sup>+</sup> (de)intercalation, but it displays pseudocapacitive response after repeated cycles. Herein, we find and demonstrate that ordered rocksalt (RS) NaTiO<sub>2</sub> nanograins are in situ formed by electrochemically cycling with Na<sup>+</sup> ions in anatase and amorphous TiO<sub>2</sub>. The in situ formed RS-NaTiO<sub>2</sub> follows a solid-solution reaction with small volume changes of only 2.0%, that determines the pseudocapacitive "mirror-like" cyclic voltammetry curve with a couple of broad redox peaks at 0.75 V vs. Na<sup>+</sup>/Na, a high capacity of 253 mAh g<sup>-1</sup>, high-rate capability and thousands of stable cycles. The multistep crystalline-to-amorphous-to-RS transformations are able to be electrochemically activated during the aging process of assembled full cells. Our finding provides a direction for developing unconventional Ti-based high-performance active materials for SIBs with both high energy and power densities.