A Transient Pseudo-capacitor Using a Bioderived Ionic Liquid with Na ions

A pseudo-capacitor with transient behavior was applied in implantable, disposable, and bioresorbable devices, incorporating an Na ion-doped bioderived ionic liquid, molybdenum trioxide (MoO3)-covered molybdenum foil, and silk sheet as the electrolyte, electrode, and separator, respectively. Sodium lactate is dissolved in choline lactate as a source of Na ions. The Experimental results reveal that the Na ions are intercalated into the van der Waals gaps in MoO3, and the pseudo-capacitor shows an areal capacitance (1.5 mF/cm2) that is three times larger than that without the Na ion. The fast ion diffusion of the electrolyte and the low resistance of the MoO3 and Mo interface resulted in an equivalent series resistance of 96 Ω. A cycle test indicated that the pseudo-capacitor exhibited a high capacitance retention of 82.8% after 10 000 cycles. The transient behavior was confirmed by the dissolution of the pseudo-capacitor into phosphate-buffered saline solution after 101 days. Potential applications of transient pseudo-capacitors include electronics without the need for device retrieval after use, including smart agriculture, implantable, and wearable devices.