Practical conversion-type titanium telluride anodes for high-capacity long-lifespan rechargeable aqueous zinc batteries

Abstract

Rechargeable aqueous zinc batteries (RAZBs) with high safety and low cost offer great hopes for complementing lithium-ion batteries. However, realizing practical high-safety and long-lifespan RAZBs is held back by the low coulombic efficiency and non-negligible dendrite issues in Zn anodes. Here, we report a layered TiTe₂ prepared by a one-step vacuum sintering technique as the metal-free anode for RAZBs, bypassing the above challenges of Zn metal. The density functional theory (DFT) calculations with ab initio molecular dynamics (AIMD) simulations predict the Zn-storage mechanism, thermodynamic stability, and ionic mobility properties of TiTe₂. The TiTe₂ electrode in the half cell shows a low charging voltage (∼0.7 V vs. Zn²⁺/Zn), a high reversible capacity of 225 mA h g⁻¹ at 0.1 A g⁻¹, and stable cycling properties with a 95% capacity retention over an exceptionally long life of 30 000 cycles at 5 A g⁻¹. As demonstrated by in situ diffraction and ex situ spectra, the sustained high reversible capacity relies on the conversion chemistry involving the ZnTe formation/dissociation process with the charge compensation by two-electron redox of Ti²⁺/Ti⁴⁺. In regard to practical implementation, the TiTe₂‖Zn_xCo₃O₄ pouch-type full battery displays a competitive energy density of 149 W h kg⁻¹ on the electrode level, exceeding state-of-the-art metal-free RAZBs. A high capacity retention of 94% is achieved in the pouch cells over 5000 cycles, verifying the bright application prospects of the TiTe₂ anode.