Electrochemically Activated Cu2-xTe as an Ultraflat Discharge Plateau, Low Reaction Potential, and Stable Anode Material for Aqueous Zn-Ion Half and Full Batteries

The utilization of Zn anodes to build aqueous Zn-metal batteries has captured extensive attention in the domain of energy storage, but this task faces scientific challenges, such as Zn dendrites and unsatisfactory stripping/plating efficiency as well as gas evolution. Herein, cation-deficient Cu2-xTe (Cu1.81Te) is proposed as an attractive intercalated anode material for aqueous Zn-ion batteries. It delivers an ultraflat discharge plateau of 0.2 V (vs Zn2+/Zn) and a capacity of 158 mAh g(-1), of which 86% capacity is contributed from the discharge plateau at 0.2 V. Moreover, it shows superior cyclability with 100% capacity retention over 2000 cycles at 2.5 C (1 C = 242 mA g(-1)). Experimental characterization reveals that it undergoes sequential insertion and conversion mechanism: Zn2+ is first inserted into the Cu2-xTe which is further converted into Cu and ZnTe. Theoretical calculations demonstrate that the crystal defects in Cu2-xTe can manipulate the electronic structure to enhance reactivity and simultaneously reduce diffusion barriers. Moreover, an aqueous "rocking-chair" Cu2-xTe//Na3V2(PO4)(3 )Zn-ion full battery is demonstrated. It delivers an energy density of 58 Wh kg(-1) with a voltage output of 0.98 V, and keeps 92% capacity retention after 1000 cycles. This research provides an ultralow discharge plateau and stable anode material for aqueous Zn-ion batteries.