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, the easy dissolution of Te4+ species, and a controversial energy storage mechanism. Herein, for the first time, we demonstrate an amorphous strategy for robust aqueous TeO2/Te electrochemistry. With strong hydrogen bonding, NH4Ac confines free water, prompting TeO2 amorphous (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 electrochemistry 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 electrochemistry toward high-energy aqueous batteries.