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<p>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.</p>

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Electrochemically in situ formed rocksalt phase in titanium dioxide determines pseudocapacitive sodium-ion storage

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年2月27日

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  • Dafu Tang,
  • Ruohan Yu,
  • Yalong Jiang,
  • Jiantao Li,
  • Zerui Yan,
  • Sicheng Fan,
  • Xiaojuan Huang,
  • Sungsik Lee,
  • Tianyi Li,
  • Qingshui Xie,
  • Liqiang Mai,
  • Dong-Liang Peng,
  • Qiulong Wei

摘要

Earth-abundant TiO2 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 TiO2 is not suitable for reversible Na+ (de)intercalation, but it displays pseudocapacitive response after repeated cycles. Herein, we find and demonstrate that ordered rocksalt (RS) NaTiO2 nanograins are in situ formed by electrochemically cycling with Na+ ions in anatase and amorphous TiO2. The in situ formed RS-NaTiO2 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+/Na, a high capacity of 253 mAh g−1, 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.