Lattice Expanded\nTitania as an Excellent Anode for\nan Aqueous Zinc-Ion Battery Enabled by a Highly Reversible H<sup>+</sup>‑Promoted Zn<sup>2+</sup> Intercalation

Aqueous Zn-ion batteries have garnered\nsignificant attention\nas\npromising and safe energy storage systems. Due to the inevitable dendrite\nand corrosion in metallic Zn anodes, alternative anodes of intercalation-type\nmaterials are desirable, but they still suffer from low energy efficiency,\nunsatisfactory capacity, and insufficient cycle life. Here, we develop\na high-performance anode for aqueous Zn-ion batteries via a lattice\nexpansion strategy in combination with a Zn<sup>2+</sup>/H<sup>+</sup> synergistic mechanism. The anatase TiO<sub>2</sub> with expanded\nlattice exhibits an appropriate deintercalation potential of 0.18\nV vs Zn/Zn<sup>2+</sup> and a high reversible capacity (227 mAh g<sup>–1</sup> at 2.04 A g<sup>–1</sup>) with an outstanding\nrate capability and excellent cycle stability. The high electrochemical\nperformance is attributed to a decrease in the Zn<sup>2+</sup>/H<sup>+</sup> diffusion barriers, which results from lattice expansion\nand also a H<sup>+</sup>-promoted Zn<sup>2+</sup> intercalation effect.\nThe anode intercalates Zn<sup>2+</sup>/H<sup>+</sup> via a solid-solution\nmechanism with a minor volume change, which contributes to the high\nreversibility and thus high energy efficiency. When paired with different\ntypes of cathodes, including NV, I<sub>2</sub>, and activated carbon,\nto construct corresponding full cells, high specific energy, high\nspecific power, long cycle life, and extremely high energy efficiency\ncan be achieved. This study provides a prospect for developing high-performance\nZn-ion batteries.