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Complex Charge Compensation Mechanisms in Lithium-Rich Chalcogenide Cathodes


Zak, Joshua Joseph (2023) Complex Charge Compensation Mechanisms in Lithium-Rich Chalcogenide Cathodes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/1k50-3811.


Lithium-ion batteries have revolutionized the world by enabling long-lasting portable electronics, electrified transportation, and grid storage solutions for renewable energy implementation. However, current commercialized technologies are limited by the one electron transfer per transition metal paradigm utilized by cathode materials that operate with an intercalation-based charge storage mechanism. Finding ways to increase the charge storage capabilities of the cathode into the multielectron regime has long been a focus of research efforts, and involvement of structural anions in the redox has been demonstrated as a promising way to accomplish multielectron storage. Layered lithium-rich oxide materials have been shown to afford dramatic improvements to overall storage capacity but are plagued by complex mechanisms and unwanted side reactions that lead to poor cycling stability and characterization difficulties. This thesis expands upon previous understanding of oxide-based anion redox materials and extends the exploration into sulfide and selenide systems, which allow the study of anion redox without the side processes that affect oxides. First, a dynamic charge compensation mechanism of late group metal-poor, lithium-rich oxide, Li2Ru0.3Mn0.7O3, is uncovered and found to involve an irreversible anion oxidation that leads to involvement of redox states on transition metals previously thought to be unavailable. Second, active electrolyte additives are explored as a method of stabilizing the cathode-electrolyte interface of anion redox material, Li2RuO3. Third, reversible anion redox is demonstrated in alkali-rich sulfides, Li2FeS2 and LiNaFeS2, and proven to occur through oxidation of sulfides (S2-) to persulfides ([S2]2-). Understanding of the structural ramifications of anion oxidation in Li2FeS2 is further expanded through computational and experimental methods. Fourth, the role of metal-anion covalency is systematically investigated through anion substitution of Li2FeS2 with S2-, highlighting the importance of a holistic understanding of changes to the electronic and physical structure of anion redox materials to predict long-term performance. Finally, detailed perspectives and future outlooks on sulfur redox in lithium battery systems are offered with an exhaustive survey of thermodynamically stable binary and ternary persulfide materials.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:lithium ion batteries; lithium-rich cathodes; anion redox; electrochemistry; spectroscopy
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • See, Kimberly A.
Thesis Committee:
  • Cushing, Scott K. (chair)
  • Giapis, Konstantinos P.
  • Faber, Katherine T.
  • Hadt, Ryan G.
  • See, Kimberly
Defense Date:20 September 2022
Non-Caltech Author Email:joshuajzak (AT)
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1745301
Record Number:CaltechTHESIS:06022023-055053747
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for ch. 1 and ch. 7 adapted for ch. 2 adapted for ch. 4 adapted for ch. 6
Zak, Joshua Joseph0000-0003-3793-7254
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15279
Deposited By: Joshua Zak
Deposited On:02 Jun 2023 18:24
Last Modified:09 Jun 2023 19:14

Thesis Files

[img] PDF (Redacted thesis, ch. 5 excluded) - Final Version
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