A Stretchable and Self‐Healing Energy Storage Device Based on Mechanically and Electrically Restorative Liquid‐Metal Particles and Carboxylated Polyurethane Composites. Issue 1 (2nd November 2018) - Park, Sangbaek
Abstract: Stretchable and self‐healing (SH) energy storage devices are indispensable elements in energy‐autonomous electronic skin. However, the current collectors are not self‐healable nor intrinsically stretchable, they mostly rely on strain‐accommodating structures that require complex processing, are often limited in stretchability, and suffer from low device packing density and fragility. Here, an SH conductor comprising nickel flakes, eutectic gallium indium particles (EGaInPs), and carboxylated polyurethane (CPU) is presented. An energy storage device is constructed by the two SH electrodes assembled with graphene nanoplatelets sandwiching an ionic‐liquid electrolyte. An excellent electrochemical healability (94% capacity retention upon restretching at 100% after healing from bifurcation) is unveiled, stemming from the complexation modulated redox behavior of EGaIn in the presence of the ligand bis(trifluoromethanesulfonyl)imide, which enhances the reversible Faradaic reaction of Ga. Self‐healing can be achieved where the damaged regions are electrically restored by the flow of liquid metal and mechanically healing activated by the interfacial hydrogen bonding of CPU with an efficiency of 97.5% can be achieved. The SH conductor has an initial conductivity of 2479 S cm −1 that attains a high stretchability with 700% strain, it restores 100% stretchability even after breaking/healing with the electrical healing efficiency of 75%. Abstract : An elastic conductor composed of nickel flakes, liquid metal, and carboxylated polyurethane is highly conductive, intrinsically stretchable, self‐healing, and electrochemically stable, and it can be utilized in rechargeable soft energy storage applications by means of the complexation of Ga with ligands, which shifts the redox potential of Ga(III)/Ga into the stable electrochemical window of an ionic‐liquid electrolyte.