Global energy demands are expected to increase by about one-third between 2014 and 2040 and will surely be met from a combination of wind, solar, and among other renewable sources. The shift away from fossil fuels and towards renewable energies will ensure a clean and sustainable future. The main issue with these sources is that they are intermittent energy sources and thus, energy storage is necessary to make these sources viable to meet increasing energy demands. Available storage technologies include solid oxide fuel cells (SOFC), solid oxide flow batteries (SOFB), secondary cells, and several others. The secondary cell, such as Li-ion batteries is more favorable to pursue due to room temperature operation whilst SOFC and SOFB require high temperatures to operate. Current secondary cells are unable to achieve the necessary degrees of energy and power densities for grid-level storage which prompts an interdisciplinary approach to tackle these issues. The focus of this thesis is to investigate multicomponent electrodes and how each component can influence the electrochemical performance in relation to cycling stability, capacity, and reaction pathway. To best understand these relationships between structure and performance of complex conversion-based electrodes, a Cu-substituted nickel fluoride with control of Cu concentration is used to reveal how it can influence the reaction kinetics with the aid of electron microscopy techniques, accompanied with electrochemical analytical techniques. Moving on to an intercalation-based cathode, LiNi0.5Mn0.3Co0.2O2 (NMC), a similar principle of introducing an additional component, LiFe5O4, into the system can influence the surface chemistry, thus improving lithiation kinetics for increased cycling stability. The final system, Fe3O4/graphite composite, studied invokes both intercalation and conversion-based reactions to maximize performance. This system investigates utilizing structure to mitigate the biggest crux of conversion-based electrodes, volume expansion, by sandwiching Fe3O4 nanoparticles between reduced graphite flakes. The combination of electron microscopy and electrochemical analytical techniques are leveraged to bring to light the relationship between the observed structural evolutions and electrochemical performance to guide future design that will allow us to meet expected energy demands as global population grows.

Creator

• Villa, Cesar J

DOI

• https://doi.org/10.21985/n2-dn52-sw73

Subject

• Energy

Language

• en

Alternate Identifier

• etdadmin_upload_788935
• http://dissertations.umi.com/northwestern:15440

Keyword

• Lithium
• electron microscopy
• Battery
• anode
• cathode

Date created

• 2020-01-01

Resource type

• Dissertation

Rights statement

• In Copyright