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Fundamental Understanding And Designing Of Nickel And Cobalt Free Cathodes For Lithium-Ion Batteries
Access Type
WSU Access
Date of Award
January 2025
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Mechanical Engineering
First Advisor
Leela Mohana Reddy Arava
Abstract
Despite 30 years of active research in the field of Li-ion battery chemistry, the current energy demands attracted materials researchers, engineers, and chemists to develop new battery materials or redox mechanisms with high capacity and high energy density properties. In addition to fundamental issues in chemical design, raw materials scarcity and geopolitical issues are driving the shift away from critical raw materials such as nickel (Ni) and cobalt (Co) elements. Current state-of-the-art Li-ion batteries are reaching their theoretical limit with respect to their capacity, a property largely limited by cathode materials that so far relied solely on cationic-redox of transition-metal ions (e.g., M3+/4+ in LiMO2 where M is Co, Ni, and Mn) for driving electrochemical reactions. Recently, the introduction of new anion-redox (O2-/On-, n<2) cathode materials can lead to a doubling of capacity by accommodating multielectron (> 1 e- or Li+ transfer per formula unit) redox chemistries that gained research interest. However, current anion-redox cathode materials based on Li-rich layered oxides (represented by the formula Li1+xM1-xO2 where M is Co, Ni, and Mn) suffer from voltage fade, large hysteresis, and sluggish kinetics, which originate mysteriously from the anionic redox activity of oxygen ligand itself. It is proven that the covalent interaction (tightness between metal – ligand bond) between transition metal – oxygen ligand in traditional cathode materials (LiCoO2, LiNixMnyCozO2, LiFePO4) needs to be altered to take advantage of anion redox chemistry. Here, in this dissertation work, an alternative approach of introducing improved metal – ligand covalency is presented by utilizing less electronegative chalcogen ligands (Sulfur (S), Selenium (Se) in the cathode structural framework where the metal d-band penetration into ligand p-band thereby utilizing mixed anionic and cationic redox chemistry. The experimental insights provide a significant design approach that will accelerate the search for prospective Ni and Co free chalcogen based cathodes in the pursuit of next generation energy storage materials. Tuning covalency by Ni and Co free metals and highly reversible chalcogen ligands (S, Se) led to address broader scientific impact: (i) eliminating the reliance on Ni and Co-based cathodes; (ii) high lithium storage capacity in liquid and solid-state systems; (iii) fast charging capability without crystal structure degradation; and (iv) improving thermal safety by eliminating detrimental O2 release. In summary, the dissertation research addresses the technological bottleneck in the field of anion redox cathode materials through fundamental materials chemistry, synchrotron spectroscopy, imaging, and electronic structure calculations. The presented ideas and strategies through this dissertation work will cover a broad spectrum of engineering principles, solid-state materials chemistry, and electronic structure for addressing one of the critical research problems in renewable energy materials space.
Recommended Citation
Nagarajan, Sudhan, "Fundamental Understanding And Designing Of Nickel And Cobalt Free Cathodes For Lithium-Ion Batteries" (2025). Wayne State University Dissertations. 4229.
https://digitalcommons.wayne.edu/oa_dissertations/4229