A report discusses physicochemical issues affecting a fluoride-intercalating cathode that operates in conjunction with a lithium ion-intercalating anode in a rechargeable electrochemical cell described in a cited prior report. The instant report also discusses corresponding innovations made in solvent and electrolyte compositions since the prior report. The advantages of this cell, relative to other lithium-ion-based cells, are said to be greater potential (5 V vs. 4 V), and greater theoretical cathode specific capacity (0.9 to 2.2 A-h/g vs. about 0.18A-h/g). The discussion addresses a need for the solvent to be unreactive toward the lithium anode and to resist anodicoxidation at potentials greater than about 4.5 V vs. lithium; the pertinent innovation is the selection of propylene carbonate (PC) as a solvent having significantly more stability, relative to other solvents that have been tried. The discussion also addresses the need for an electrolyte additive, denoted an anion receptor, to complex the fluoride ion; the pertinent innovation is the selection of tris(hexafluoroisopropyl) borate as a superior alternative to the prior anion receptor, which was tris(pentafluorophenyl) borate.
This work was done by William West of Caltech for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free online at www.techbriefs.com/tsp under the Physical Sciences category.
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Anion-Intercalating Cathodes for High-Energy-Density Cells
(reference NPO-42316) is currently available for download from the TSP library.
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Overview
The document titled "Anion-Intercalating Cathodes for High-Energy-Density Cells" from NASA's Jet Propulsion Laboratory discusses advancements in battery technology, particularly focusing on a novel dual ion intercalating battery system. This system is designed to utilize anion intercalation, specifically targeting fluoride ions, to significantly enhance the performance of lithium-ion batteries.
The proposed battery architecture aims to achieve a higher cell voltage, exceeding 5V, compared to the current state-of-the-art lithium-ion cells, which typically operate around 4V. This increase in voltage is coupled with a theoretical specific capacity for the cathode that ranges between 900 to 2200 mAh/g, which is substantially higher than conventional cathode materials.
The document outlines the experimental results related to solvent selection for the battery cells. It highlights the challenges associated with using standard lithium-ion solvents, such as ethylene carbonate-dimethyl carbonate, which exhibit poor stability at high voltages. Instead, the research explores alternative solvents, including aliphatic asymmetric sulfones and propylene carbonate. While the sulfones showed acceptable anodic stability, they were found to be reactive with lithium metal anodes. Propylene carbonate emerged as a more suitable solvent, demonstrating superior stability at the lithium anode and excellent anodic oxidation stability at high charge voltages.
The document also presents findings from x-ray diffraction studies that provide strong evidence of reversible fluoride intercalation. The x-ray diffraction plots reveal a single graphite (002) reflection in the discharged state, while charging the cell introduces a new lower angle reflection indicative of fluoride staging. This new peak disappears upon discharge, confirming the reversible nature of the intercalation process.
Overall, the research demonstrates a promising approach to developing high-energy-density batteries that could significantly outperform existing lithium-ion technologies. The findings suggest that the proposed dual ion intercalating battery system could lead to advancements in energy storage solutions, with potential applications in aerospace and other fields requiring high-performance batteries. The document serves as a technical support package, providing insights into ongoing research and technology development in this area, and emphasizes the importance of continued innovation in battery technology for future applications.
