High-performance Zinc-ion hybrid MEMS supercapacitors with high energy density

In energy harvesting applications, consumer electronics, and other power-demanding industrial sectors, energy storage with high power and energy efficiency along with long cycling life are key demands. The goal of this project is to fabricate an innovative MEMS-based hybrid supercapacitor with energy density > 100 µWh/cm2 (one of the greatest values reported for micro-supercapacitors), high potential density (at least 2x greater than most efficient LIBs at different current rates), and excellent cycling life (over 10,000 cycles; 6.7X greater than LIBs) through a cost-effective process. Through the Small Business Technology Transfer (STTR) Phase I program, we will investigate the feasibility of fabricating all-solid-state zinc-ion hybrid MEMS supercapacitor microdevices as high-performance energy storage devices, for energy harvesting applications that solve the conventional limitation of low gravimetric and areal energy densities, and poor lifetime. To this end, we will first perform a study to select a cost-effective technique for mass production of MEMS supercapacitors, relying on the maximization of the material index (energy density × power density × cycling life /cost per unit cm2). Our preliminary results confirmed that a highly porous supercapacitor-type carbon nanofiber (CNF) cathode and Zn nanosheets-electrodeposited carbon-based anode in the presence of solid-electrolyte ZnCl2 in a single package as zinc-ion hybrid supercapacitor has the potential to fabricate one of the most efficient MEMS devices. Interestingly, electrodes can be mass-produced through already-matured fabricating processes and the proposed solid electrolyte can be deposited by a simple spray coating, implying ease scale up in the next phases. Inspired by the preliminary results from aqueous ZnCl2 electrolyte, the PVA-ZnCl2 will be initiated for the first time as an electrolyte to address the tradeoff between cycling life and energy density. Reducing the interfacial resistance in the presence of solid electrolyte will realize the fabrication of an efficient micro-sized energy storage as the outcome of this project. Different techniques for microfabrication of MEMS supercapacitors and associated challenges and tradeoffs, process development, reducing the interfacial resistance effects, selection of efficient and cost-effective materials, and identification of the optimum conditions associated with changing paper-type micro supercapacitors to MEMS will be delivered in Phase I. The proposed innovative evolutions to these technical challenges will de-risk the Zn-ion hybrid MEMS supercapacitors product prototyping in the following project phases to make ready the technology for commercialization. These research activities will also advance the scientific understanding and technological development of micro-structured electrode process through electrospinning and property control, and particularly supercapacitor technology.