A layered Bi2Te3@PPy cathode for aqueous zinc ion batteries: Mechanism and application in printed flexible batteries

Low‐cost, safe, and environmental‐friendly rechargeable aqueous zinc‐ion batteries (ZIBs) are promising as next‐generation energy storage devices for wearable electronics among other applications. However, sluggish ionic transport kinetics and the unstable electrode structure during ionic insertion/extraction hampers their deployment. Herein,  we propose a new cathode material based on a layered metal chalcogenide (LMC), bismuth telluride (Bi<jats:sub>2</jats:sub>Te<jats:sub>3</jats:sub>), coated with polypyrrole (PPy). Taking advantage of the PPy coating, the Bi<jats:sub>2</jats:sub>Te<jats:sub>3</jats:sub>@PPy composite presents strong ionic absorption affinity, high oxidation resistance, and high structural stability. The ZIBs based on Bi<jats:sub>2</jats:sub>Te<jats:sub>3</jats:sub>@PPy cathodes exhibit high capacities and ultra‐long lifespans of over 5000 cycles. They also present outstanding stability even under bending. In addition,  we analyze here the reaction mechanism using in situ X‐ray diffraction, X‐ray photoelectron spectroscopy, and computational tools and demonstrate that, in the aqueous system, Zn<jats:sup>2+</jats:sup> is not inserted into the cathode as previously assumed. In contrast, proton charge storage dominates the process. Overall, this work not only shows the great potential of LMCs as ZIBs cathode materials and the advantages of PPy coating, but also clarifies the charge/discharge mechanism in rechargeable ZIBs based on LMCs.