A General Interfacial Capacitance Model for Nanomaterial Supercapacitors: Insights from Computational Quantum Mechanics

Electrochemical energy storage devices play a crucial role in the drive towards a sustainable energy future. They are ubiquitously utilized in electric vehicles, distributed renewable energy systems, and are increasingly considered for utility-scale power applications. High-power operation, however, present unique challenges to these devices at the physical and chemical level. Despite decades of experimentally driven research progress, theoretical and computational models of energy storage devices, such as batteries and supercapacitors, are built upon a foundation that was laid more than 150 years ago. The electrode/electrolyte interface is the region of most interest. This is where charge transfer reactions take place in batteries and ion adsorption/polarization take place in supercapacitors. The physicochemical phenomena occurring at the interface depend on a wide variety of quantum mechanical effects which are not accounted for within traditional continuum models based on partial differential equations. While there have been many efforts to address this knowledge gap through traditional methods, they are either limited in applicability or entail simplifying assumptions which exclude whole classes of devices such as those based on low-dimensional nanomaterials. Graphene- based supercapacitors are especially sensitive to quantum interactions since the electrode’s capacitance can be influenced by the presence of substrates, dopants, and/or electrolyte species. Conventional quantum-capacitance-based series models of graphene capacitors assume no electronic interaction between graphene and its interfacial neighbours, which leads to an overestimation of electrode capacitance by an order of magnitude. To address these limitations, we have developed a General Interfacial Capacitance Model (GICM) for nanomaterial-based supercapacitors. The GICM is based on first-principles computational quantum mechanics in the frameworks of Density Functional Theory (DFT) and Ab-Initio Molecular Dynamics (AIMD) combined with the principles of microscopic polarization theory. Three case studies for graphene-based interfaces are presented as applications of the GICM: bilayer graphene on a silica substrate, nitrogen-doped graphene on a copper substrate, and an interface between water and copper-supported graphene. The aim of this work is to improve current understanding of the performance of nanomaterial-based electrochemical supercapacitors and guide their design at the atomic level.

Department dc:contributor.department

Electrical and Computer Engineering

Year dc:date.issued

2022

Author dc:creator

• Elshazly, Mohamed Khaled

Advisors dc:contributor.advisor

• Dawson, Francis
• Huzayyin, Ahmed

• density functional theory
• energy storage
• graphene
• molecular dynamics
• nanomaterial
• supercapacitor

Handle dc:identifier.uri

http://hdl.handle.net/1807/123380

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/123380