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

Abstract

Separators are known to be a mandatory component because of their crucial function in preventing short circuits between positive and negative electrodes, ensuring safety and cycle life of energy storage devices. However, in practice, separators are also a crucial component that affects cell electrochemical performance, especially rate capability and power density, which have been addressed in only 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-effectiveness, desirability and environmentally friendly microbubble process. The as-fabricated symmetric supercapacitor with an as-synthesised separator, prepared under optimal condition of 2 g/mL BC with 1.5 wt% gelatin and a microbubble rate of 200 CC/min (designated as 2BC1.5GT_R200), reduces cell resistance, improves ion transport within the cell, and maximises gravimetric energy density (3.2 Wh/kg) and gravimetric power density (1.6 kW/kg) compared to as-fabricated symmetric supercapacitors using BC, hybridised BC-gelatin under other conditions, and conventional cellulose separators. Additionally, the symmetric device with the 2BC1.5GT_R200 separator achieves excellent cycle life, retaining 89% of its initial capacitance after 20,000 cycles. These data demonstrate that the microbubble synthesis process combined with gelatin hybridisation can maximise electrochemical performance and significantly presents a promising route for developing innovative separators for energy storage applications.