Tailoring Synergistic Ion Environment for Copper Telluride toward High‐Capacity and Ultrastable Acidic Multivalent‐Ion Batteries

Abstract Acidic batteries permit a reliable energy supply at low temperatures with low cost and intrinsic safety, yet the development of stable acid‐resistant electrodes with high capacity and a reliable lifespan is still challenging. Herein, nonstoichiometric copper telluride (Cu 2‐x Te) nanosheets are first explored as high‐performance electrodes for acidic batteries to provide a stable capacity release of 409 mAh g −1 with a record‐breaking lifespan of 40 000 cycles and excellent kinetics, enabling operation at a high current density of 20 A g −1 . In contrast to the inherent perception of corrosive destruction of electrode materials by strongly acidic environments, the electrolyte environment enriched with copper ions and hydrogen ions synergistically stabilizes the Cu 2‐x Te electrode and drives reversible multielectron transfer asymmetric deep conversion, which is confirmed by in situ synchrotron X‐ray diffraction, X‐ray absorption spectroscopy, first‐principal calculations, and composite electrochemical characterization. Therefore, Cu 2‐x Te provides an impressive accumulation capacity of over 4764 Ah g −1 , exceeding that of most acidic batteries, and works well at −20 °C. High‐performance Cu 2‐x Te electrodes also promote the establishment of Cu 2‐x Te//Mn 2 O 3 and Cu 2‐x Te//Fe acidic full cells enabling stable operation at room temperature and low temperature, offering promising opportunities for electrode progress in advanced acidic batteries.