Aqueous Zinc-Tellurium Batteries with Ultraflat Discharge Plateau and High Volumetric Capacity.

Traditional aqueous zinc-ion batteries (ZIBs) based on ion-intercalation or surface redox behaviors at the cathode side suffer severely from an unsatisfactory specific capacity and unstable output potential. Herein, these issues are applied to a conversion-type zinc-tellurium (Zn-Te) battery. Typically, this battery works based on a two-step solid-to-solid conversion with the successive formation of zinc ditelluride (ZnTe2 ) and zinc telluride (ZnTe). It delivers an ultrahigh volumetric capacity of 2619 mAh cm-3 (419 mAh g-1 ), 74.1% of which is from the first conversion (Te to ZnTe2 ) with an ultraflat discharge plateau. Though reported first in a challenging aqueous environment, this Zn-Te battery demonstrates an excellent capacity retention of >82.8% after 500 cycles, which results from the elimination of the notorious "shuttle effect" due to the solid-to-solid conversion behaviors. In addition, a quasi-solid-state Zn-Te battery is also fabricated, exhibiting superior flexibility, robustness, and good electrochemical performance. This work develops a novel cathode material based on conversion-type ion-storage mechanism. The system is attractive due to its ultrastable energy output, which is rarely reported for ZIBs.