Amorphization Stabilizes Te-Based Aqueous Batteries via Confining Free Water

Abstract

Tellurium (Te), with its rich valence states (−2 to +6), could endow aqueous batteries with potentially high specific capacity. However, achieving complete and stable hypervalent Te⁰/Te⁴⁺ electrochemistry in an aqueous environment poses significant challenges, owing to the sluggish reduction kinetics, easy dissolution of Te⁴⁺ species, and a controversial energy storage mechanism. Herein, we demonstrate a crystallographic regulation strategy for robust aqueous Te redox electrochemistry. With strong hydrogen bonding, NH₄Ac confines free water, prompting the amorphization of TeO₂ (a-TeO₂). In situ synchrotron characterization, spectroscopy analysis, electrochemical evaluation, and theoretical calculations reveal a specific 4 e⁻ solid-solid transition pathway (Te to a-TeO₂) with accelerated diffusion and charge transfer kinetics, attributed to a closer unoccupied electron orbital to the Fermi level and a reduced water desorption energy barrier in a-TeO₂. Impressively, the a-TeO₂/Te redox exhibits a high reversible capacity of 834 mAh g⁻¹ (99% of Te redox utilization), superior rate performance (644 mAh g⁻¹ at 10 A g⁻¹), and an ultralong lifespan (over 3000 cycles). These findings prove a new tactic to advance aqueous Te redox electrochemistry toward high-energy aqueous batteries.