Microbubble synthesis of hybridised bacterial cellulose–gelatin separators for multifunctional supercapacitors

Abstract

Separators are known to be a mandatory component due to their crucial function in preventing short circuits between positive and negative electrodes, ensuring the safety and cycle life of energy storage devices. However, in practice, separators are a crucial component that affects cell electrochemical performance, especially rate capability and power density, which have been addressed in only a few research studies. To further investigate this topic, this study introduces durable and eco-friendly separators synthesised by hybridising bacterial cellulose (BC) and gelatin through a facile, cost-effective, desirable and environmentally friendly microbubble process. The as-fabricated symmetric supercapacitor with an as-synthesised separator, prepared under optimal conditions of 2 g per mL BC with 1.5 wt% gelatin and a microbubble rate of 200 CC per min (designated as 2BC1.5GT_R200), reduces cell resistance and optimises ion transport within the cell compared to as-fabricated symmetric supercapacitors using BC, hybridised BC–gelatin under other conditions, conventional cellulose and commercial separators. Additionally, symmetric devices with 2BC1.5GT_R200 separators achieve excellent capacitance retention across a wide range of electrolyte environments, including acidic (1 M H₂SO₄), basic (1 M KOH), and neutral (1 M NaNO₃) solutions, retaining over 91%, 87%, and 82% of their initial capacitance after 10 000 cycles, respectively. These data demonstrate that the microbubble synthesis process combined with gelatin hybridisation can maximise electrochemical performance, maintain high cell efficiency, and enable operation in diverse electrolytes, presenting a promising route for developing innovative separators for energy storage applications.