The In-situ Growth of Cu₂O-CuO on Cu Foam coated with Carbon Derived from Polydopamine as the Flexible High-Voltage Cathode for Thermal Batteries

Thermal batteries are a type of thermally activated reserve batteries, where the cathode material significantly influences the operating voltage and specific capacity. In this work, Cu₂O-CuO nanowires are prepared by in-situ thermal oxidation method onto Cu foam, which are further coated with carbon layer derived from polydopamine (PDA). The morphology of the nanowires has been examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The material shows a kind of core-shell structure, with CuO as the shell and Cu₂O as the core. To further explore the interaction between the material and lithium-ion (Li⁺), the Li⁺ adsorption energies of CuO and Cu₂O were calculated, revealing a stronger affinity of Li⁺ for CuO. The unique core-shell nanowire structure of Cu₂O-CuO can provide a good Li⁺ adsorption with outer layer CuO and excellent structural stability with inner layer Cu₂O. When applied in thermal batteries, Cu₂O-CuO-C nanowires exhibit specific capacity and specific energy of 326 mAh g^-1 and 697 Wh kg^-1 at a cut-off voltage of 1.5V, both of which are higher than those of Cu₂O-CuO (238 mAh g^-1 and 445 Wh kg^-1). The discharge process includes the insertion of lithium ions and subsequent reduction reactions, ultimately resulting in the formation of lithium oxide and copper.