Nanoporous Electrodes By Laser-Induced Carbonization and Patterning of Polymer Resins for Flexible Energy Storage

Improvements to miniaturized and flexible energy storage are required for a variety of current and next-generation applications ranging from wearable devices to smart credit cards. IR laser patterning of commercially available polymer substrates (ex. Kapton) has become a versatile platform for the rapid prototyping and final fabrication of electrodes for such devices.¹ However, the carbonized structures formed, which have been termed “laser-induced graphene”, are largely macroporous and possess a low bulk density which currently limits the achievable energy density and flexibility of such thin film devices.

In this work, we explore improved substrate materials, morphologies and device architectures that lead to more energy dense systems. Specifically, the development of composites based on the waste biomass-derived polymer polyfurfuryl alcohol (PFA) will be discussed. This resin-forming polymer is known to carbonize at high yield and form a microporous carbon upon high temperature thermal treatment. We demonstrate that this material can be carbonized by the CO₂ laser but only in the presence of graphene oxide. Thermal treatment of resins with incorporated graphene oxide suggest a significant catalytic effect on the process of graphitization. Furthermore, when the film is made into a porous vs. non-porous resin, we observe no expansion or macropore development such that the electrodes remain embedded in the film – likely due to the short path length in the porous network for decomposition gases to escape. The improved electrode structure results in interdigitated electrodes achieving nearly five-fold increased areal capacitance and improved flexibility.

In addition to supercapacitor development, we will also discuss our recent efforts to develop flexible batteries based on the laser-induced graphene approach. In particular, we demonstrate the ability to nucleate/grow sulfur onto laser-induced graphene electrodes which can be melt-imbibed into the microporous network. We also demonstrate the ability to electroplate lithium metal directly onto the laser-scribed anode using a combination of pulse-reverse-pulse deposition² and Ag-nanoparticles as a nucleation aid.³ While promising for device applications, the resulting flexible Li-S battery system is also useful for in situ investigations of speciation during battery operation