Investigation of non-intercalation electrode materials for next-generation batteries

As new emerging techniques such as electric vehicles and energy storage at large scale are growing, the demands of secondary rechargeable batteries with high energy density increase dramatically. Conversion and alloying electrodes for secondary rechargeable batteries have been studied intensively as alternatives to intercalation materials as they can provide 2 to 5 times larger gravimetric capacities. However, there are many challenges facing the practical application of conversion electrodes. In this dissertation, the problems of conversion and alloying electrodes are discussed and addressed. In Chapter 2, the electrochemical properties of FeF2 conversion cathodes coated on a 3D Ni scaffold with a thin layer of Al2O3 are studied. The 3D scaffold improves the reaction kinetics and enables a high specific capacity by providing an efficient electron pathway to the insulating FeF2 and shortening Li diffusion length. Al2O3 coating appears to improve the cycle life significantly as it prevents the side reaction by limiting the direct contact of the electrode with the electrolyte. In Chapter 3 and 4, this dissertation reports new alloying cathode materials for lithium and sodium ion batteries. The fabrication of a rGO/LiI composite enables the use of LiI as a Li-ion battery cathode. The freestanding rGO/LiI electrodes show stable long-term cycling, reduced shuttling and good rate performance with high specific capacity and small hysteresis. The improved electrochemical performance can be attributed to strong interactions between the active materials and rGO, and the reduced ion and electron transport distances provided by the 3D structured cathode. This dissertation also demonstrates the fabrication of a NaI-loaded CNT mat cathode for Na-ion battery cathode application. The electrodes show a good capacity retention, high specific energy density, and small hysteresis. Adding a CNT mat interlayer between the NaI composite cathode and the separator, and FEC to the electrolyte significantly suppresses shuttling of active materials during cycling. Using ex situ XPS and Raman data, the relevant processes occurring during cycling of the CNT/NaI cathode are examined. In Chapter 5, a volume expansion issue of conversion electrodes is addressed. A 3D Ni supported Sb2O3 electrode is prepared by colloidal templating and pulsed electrodeposition followed by heat treatment. Larger pore interconnects are obtained in the 3D scaffold to increase active materials loading and accommodate a large volume expansion. The electrodes accommodate volume expansion without lowering the overall energy density. The stable cycling performance can be attributed to the 3D metal scaffold which supports active materials undergoing huge volume changes and post heat treatment effect. Finally, the reversibility of conversion reaction is discussed in Chapter 6. The electrochemical properties of SnS, chosen as a representative metal sulfide, are studied in a both solid-state and liquid cell. The solid electrolyte prevents the degradation of the SnS active material, enables a reversible conversion reaction, and suppresses electrolyte reduction, the combination of which leads to a stable cycling performance and small first cycle irreversible capacity. Reaction chemistry of SnS in a solid-state cell is discussed more in detail by ex situ XRD and XAS results.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science & Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2019

Author dc:creator

• Kim, Sanghyeon

Contributors dc:contributor

• Braun, Paul V.
• Dillon, Shen J.
• Evans, Christopher
• Rodríguez-López, Joaquín

• Electrochemistry
• Energy Storage
• Secondary Ion Batteries

Statement dc:rights

• Copyright 2019 Sanghyeon Kim

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/105116

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/105116