Anion Redox in Metal Sulfide Cathodes for Na-Ion Batteries
Abstract
Research Problem: Na-ion batteries are promising candidates for next-generation, mobile energy storage that address the cost and ava,ilability issues of Li-ion. Na has nearly the same standard reduction potential as Li but is much more abundant and less expensive.,Current Na battery cathodes are limited in capacity largely due to the instability of desodiated materials. Objectives: We aim to st,udy anion redox as a strategy to increase the capacity of cathode materials and determine if the structural response as a result of,anion redox can accommodate the strain associated with the removal of large Na cations. Anion redox engages the electronic states of, the anions in charge compensation. Materials that can undergo both anion redox and transition metal redox can store multiple electr,ons, yielding high capacities. Anion redox is more often studied in oxide materials, but the high voltages required for oxide oxidat,ion induce side reactions that convolute the data. We aim to bypass this problem using sulfide materials whose redox potentials are,within the electrolyte window. Furthermore, anion redox in sulfide materials is reversible suggesting that the structural deformatio,ns are also reversible. Technical Approach: We will study anion redox in Na-rich sulfides to develop structure-property relationship,s associated with anion redox in sodium cathodes. Sulfide redox has been shown to reversibly form persulfide moieties in Li material,s. We will determine if the degrees of freedom afforded by the structural changes upon sulfide oxidation are sufficient to accommoda,te the strain imposed by desodiation. In Aim 1, we propose to develop structure-property relationships associated with anion redox i,n Na cathodes using a materials family with known Na ion conductivity and known anion redox capability. The effect of particle size,on the reversibility of the sulfide redox will be determined. The covalency of the metal-anion bond will be tuned through metal subs,titution to modulate the distribution of metal vs. anion charge compensation. In Aim 2, we will target Na-rich sulfide phases with h,igh theoretical capacities. The electrochemistry of Na-rich sulfide cathode materials has yet to be reported. We will systematically,t will be pursued to understand the charge compensation mechanisms and ,proposed work will expand our understanding of anion redox in high strain Na-ion cathodes using both known and new materials. The st,ructure-property relationships that will be discovered as a result of this work will allow for the realization of high-capacity Na-i,on cathodes. Impact on DoD Capabilities: We propose fundamental research that, if successful, will enable breakthrough improvements,in battery capacity and reliability by advancing the state-of-the-art for rechargeable batteries beyond Li-ion technology. High capa,city Na-ion electrochemistry would yield batteries that are much less expensive compared to Li-ion with high energy densities. Recha,rgeable batteries enable missions to proceed and be extended in the absence of local infrastructure or logistical support, and thus,rd high-tech and electronics-laden gear. As that trend continues, our work will improve the technologies available to Navy operatio,ns by providing pathways to future higher-capacity batteries that will allow the time available between battery changes or recharges, to be increased beyond that accessible to Li-ion technologies. These improvements will enable missions to be extended further and,will reduce operational burdens associated with keeping electronic gear functioning. Approved for public release.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 08, 2022
- Source ID
- N000142212329
Entities
People
- Kimberly A. See
Organizations
- California Institute of Technology
- Office of Naval Research
- United States Navy