Recyclable liquid metal – Graphene supercapacitor
Afsaneh L. Sanati, Pedro Alhais Lopes, Alexandre Chambel, André F. Silva, Diogo M.M. Oliveira, Carmel Majidi, Anı́bal T. de Almeida, Mahmoud Tavakoli
Abstract
Because of their high electrical conductivity, fluidic deformability, self-healing properties, and the possibility of recycling, Ga-based liquid metal alloys like eutectic gallium indium (EGaIn) have tremendous potential as electrodes for stretchable energy storage devices. However, EGaIn droplets could never be used as electrodes in thin-film supercapacitors (SCs) at the desired micro/nano scale, because they rapidly coalesce into bulk EGaIn when contacting acidic/alkaline electrolytes. Here, we show that coating EGaIn droplets with only 0.08 wt% of reduced graphene oxide (GO) nanosheets tremendously improves their chemical stability. We fabricated binder-free GO-coated EGaIn nanocomposite electrodes that show excellent stability in a strong alkaline electrolyte. We demonstrated a symmetric soft-matter pseudo-SC with areal capacitances of 1200mF/[email protected] mA/cm2 and 220mF/cm2@1mA/cm2, which is > 10 × compared to previous SCs based on bulk EGaIn. This SC retains 98.4 % of the initial capacitance after 4000 electrochemical cycles and exhibits comparable self-discharge rates to state-of-the-art flexible pseudo-SCs. Surprisingly, applying mechanical strain results in improved areal capacitance. We demonstrate rapid, laser-based fabrication of a wirelessly chargeable elastic film with an integrated energy harvesting antenna and energy-storage SC that can be used in wearable biomonitoring patches, and e-textiles. Finally, we demonstrate the recovery of the metals from the disposed of SCs through an electrowinning technique.