A Hybrid Battery-Capacitor Based on CoNiP Nanoparticles Embedded in Graphene Oxide by Electrophoretic Deposition

A one-pot colloidal synthesis approach and binder-free, environmentally friendly electrophoretic deposition were applied to fabricate a high-performance hybrid battery-capacitor system. Specifically, well-defined CoNiP nanoparticles were prepared in the presence of exfoliated graphene oxide (GO) and a hydrophobic solvent, i.e., oleylamine. The latter maintained the GO interlayer spacing sufficiently large, thus enabling the formation of CoNiP nanoparticles between the graphitic sheets and assisting in the partial reduction of the GO. Comprehensive characterization confirmed the effective integration of CoNiP nanoparticles within the exfoliated reduced GO sheets, resulting in a robust electrode architecture. The hybrid material demonstrated high specific and areal capacities of 100 mAh cm^–2(477 mAh g^–1) and exhibited good cycling stability, with 97% capacity retention over 10,000 cycles. Additionally, it delivered high areal energy and power densities of 75 μWh cm^–2and 7129 μW cm^–2, respectively, while maintaining a low mass loading of less than 0.20 mg cm^–2. This work highlights the potential of combining advanced synthetic techniques with ecofriendly deposition methods to create scalable, high-performance energy storage solutions, paving the way for sustainable energy technologies.