Lattice Expanded Titania as an Excellent Anode for an Aqueous Zinc-Ion Battery Enabled by a Highly Reversible H+-Promoted Zn2+ Intercalation.

Aqueous Zn-ion batteries have garnered significant attention as promising and safe energy storage systems. Due to the inevitable dendrite and corrosion in metallic Zn anodes, alternative anodes of intercalation-type materials are desirable, but they still suffer from low energy efficiency, unsatisfactory capacity, and insufficient cycle life. Here, we develop a high-performance anode for aqueous Zn-ion batteries via a lattice expansion strategy in combination with a Zn²⁺/H⁺ synergistic mechanism. The anatase TiO₂ with expanded lattice exhibits an appropriate deintercalation potential of 0.18 V vs Zn/Zn²⁺ and a high reversible capacity (227 mAh g^-1 at 2.04 A g^-1) with an outstanding rate capability and excellent cycle stability. The high electrochemical performance is attributed to a decrease in the Zn²⁺/H⁺ diffusion barriers, which results from lattice expansion and also a H⁺-promoted Zn²⁺ intercalation effect. The anode intercalates Zn²⁺/H⁺ via a solid-solution mechanism with a minor volume change, which contributes to the high reversibility and thus high energy efficiency. When paired with different types of cathodes, including NV, I₂, and activated carbon, to construct corresponding full cells, high specific energy, high specific power, long cycle life, and extremely high energy efficiency can be achieved. This study provides a prospect for developing high-performance Zn-ion batteries.