Thermally Regenerative Battery Using Needle-Like Composite Electrodes with Hierarchical Porous Surface: Nanostructure Regulation and Performance Enhancement

Thermally regenerative batteries (TRB) hold significant promise for low-grade waste heat recovery due to their unique advantages, such as high power density and simple structure. To address the issues of limited and unstable reaction interfaces in conventional electrodes, this study proposes a hierarchically porous composite electrode fabricated via dynamic hydrogen bubble template (DHBT) electrodeposition. By adding the crystal modifier Janus Green B (JGB), the copper deposition morphology was tailored to form needle-like nanostructures. SEM results confirm the successful synthesis of the nanostructured electrode. Compared with conventional Cu/Ni electrodes, the TRB equipped with the nanocopper electrode demonstrated significantly enhanced performance, primarily attributable to its markedly increased specific surface area. After constructing a porous nickel framework via the DHBT method, the specific surface area was further enlarged, and copper detachment was effectively mitigated, leading to an additional 44.2% improvement in battery performance. The concentration of JGB considerably influenced the nanostructure and battery performance. As the JGB concentration increased, the TRB performance first improved and then declined, with an optimal concentration identified at 0.25 mg/mL. This trend is attributed to the fact that low JGB concentrations have a limited effect on Cu2+ deposition and provide little improvement in specific surface area, whereas excessive JGB molecules occupy active sites on the nickel skeleton, hindering Cu2+ adsorption and deposition, thereby reducing reactive sites. Furthermore, the nanostructured composite electrode developed in this work maintained a stable operation over more than 16 discharge cycles, demonstrating excellent long-term durability. This study provides valuable guidance for electrode design and performance enhancement in thermally regenerative battery technology.