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 battery, 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 a 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 the outer layer CuO and excellent structural stability with the 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 1.5 V 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.