High-Performance Soft Supercapacitors Obtained Using Shape-Transformed Liquid Metal Rods Decorated with NiCo₂O₄ Nanoneedles via Interfacial Galvanic Replacement

Gallium-based liquid metals (LMs) are considered promising electrodes for supercapacitors owing to their metallic conductivity and high deformability. LMs can form nanoparticles via ultrasonication and can be further transformed into rod morphologies via hydrothermal treatment. Remarkably, LM rods exhibit a larger surface area than particles, allowing them to be highly decorated with different metals via galvanic replacement. In this study, a novel electrode is introduced, shape-transformed liquid metal rods decorated with NiCo₂O₄ nanoneedles anchored on activated carbon. Electrodes with hierarchical structures enhanced the pseudocapacitive performance in an alkaline electrolyte (1.0 m KOH), achieving a high specific capacitance of 749.6 F g⁻¹ at 1 A g⁻¹. Owing to the deformability of the LM electrodes as well as the use of LM current collectors, the devices are endowed to be fully soft and exhibited mechanical and electrochemical stability even after cycles of deformation. When assembled into an asymmetric soft supercapacitor with activated carbon as a cathode, the device delivered a specific capacitance of 45 F g⁻¹ at 2 A g⁻¹ and retained 96% of its initial capacitance even after 10 000 galvanostatic charge–discharge (GCD) cycles and after 1 000 mechanical bending cycles with 50% compression, and stretching cycles with 30% elongation.