ERI: Molecular-level Characterization of Water-in-Salt Electric Double-Layer Capacitors: Nanoscale Thermal Effects on Differential Capacitance

Energy storage needs are expected to grow substantially in the coming years. Batteries are the most common solution, but they have multiple downsides, such as short lifetime, low performance at low temperatures, and high fire/explosion hazard risks. New generation supercapacitors are promising candidates owing to their light weight, fast charging, safe use, and non-toxic content. Supercapacitors are expected to satisfy high energy needs as well (to replace batteries) and their market size is expected to increase four times over the next six years. However, the thermal behavior of new generation nanoporous supercapacitors designed to work at high potentials is not well understood, hindering their potential use. This project will investigate the temperature influence to make supercapacitors more reliable and support their transformation for future needs. In parallel, educational activities will create nanotechnology awareness in a wide range of education levels to attract students to the Science, Technology, Engineering, and Math (STEM) related professions to support future workforces especially from underrepresented groups from Chattanooga-area schools. Electric double-layer (EDL) capacitor (EDLC) is a promising technology to store energy since the electrode/electrolyte interface holds a large electric potential difference at a very small distance. This creates the main advantage of EDLCs, but also makes accurate calculations very challenging. The EDL formation as well as transfer of built-up heat shows non-continuum behavior since molecular level mechanisms are dominant at nano-levels. Using molecular dynamics, the project will provide the true characterization of coupled behavior of EDL formation and nanoscale heat transfer at the electrode/electrolyte interface. The overall objective of this project is to describe capacitance of new water-in-salt electrolytes with porous graphene as a function of structural and temperature conditions. The project will use molecular-level modeling to explore the behavior of the electrode/electrolyte systems. Goals are to describe (i) the heat transfer through electrolyte domain and electrolyte/electrode interface, (ii) the ionic distributions as a function of resulting temperatures, and (iii) the differential capacitance at corresponding working conditions. The fundamental knowledge created on the coupled behavior of “electric double layer” and “nanoscale heat transfer” will support the development of a wide range of applications from biomedical science to energy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.