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Elucidating the Role of Electrochemically Formed LiF in Discharge and Aging of Li-CFx Batteries.
Schoetz, Theresa; Robinson, Loleth E; Gordon, Leo W; Stariha, Sarah A; Harris, Celia E; Seong, Hui Li; Jones, John-Paul; Brandon, Erik J; Messinger, Robert J.
Affiliation
  • Schoetz T; Department of Chemical Engineering, The City College of New York, CUNY, New York, New York 10031, United States.
  • Robinson LE; Department of Chemical Engineering, The City College of New York, CUNY, New York, New York 10031, United States.
  • Gordon LW; Department of Chemical Engineering, The City College of New York, CUNY, New York, New York 10031, United States.
  • Stariha SA; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States.
  • Harris CE; Department of Chemical Engineering, The City College of New York, CUNY, New York, New York 10031, United States.
  • Seong HL; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States.
  • Jones JP; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States.
  • Brandon EJ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States.
  • Messinger RJ; Department of Chemical Engineering, The City College of New York, CUNY, New York, New York 10031, United States.
ACS Appl Mater Interfaces ; 16(15): 18722-18733, 2024 Apr 17.
Article in En | MEDLINE | ID: mdl-38587415
ABSTRACT
Fifty years after its introduction, the lithium-carbon monofluoride (Li-CFx) battery still has the highest cell-level specific energy demonstrated in a practical cell format. However, few studies have analyzed how the main electrochemical discharge product, LiF, evolves during the discharge and cell rest periods. To fill this gap in understanding, we investigated molecular-level and interfacial changes in CFx electrodes upon the discharge and aging of Li-CFx cells, revealing the role of LiF beyond that of a simple discharge product. We reveal that electrochemically formed LiF deposits on the surface of the CFx electrode and subsequently partially disperses into the electrolyte to form a colloidal suspension during cell aging, as determined from galvanostatic electrochemical impedance spectroscopy (EIS), solid-state 19F nuclear magnetic resonance (NMR), dynamic light scattering (DLS), and operando optical light microscopy measurements. Electrochemical LiF formation and LiF dispersion into the electrolyte are distinct competing rate processes that each affect the cell impedance differently. Using knowledge of LiF dispersion and saturation, an in-line EIS method was developed to compute the depth of discharge of CFx cells beyond coulomb counting. Solid-state 19F NMR measurements quantitatively revealed how LiF and CF moieties evolved with discharge. Covalent CF bonds react first, followed by a combination of covalent and ionic CF bonds. Quantitively correlating NMR and electrochemical measurements reveals not only how LiF formation affects cell impedance but also that CF bonds with the most ionic character remain unreacted, which limits realization of the full theoretical specific capacity of the CFx electrode. The results reveal new insights into the electrochemical discharge mechanism of Li-CFx cells and the unique role of LiF in cell discharge and aging, which suggest pretreatment strategies and methods to improve and measure the performance of Li-CFx batteries.
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Full text: 1 Collection: 01-internacional Database: MEDLINE Language: En Journal: ACS Appl Mater Interfaces Journal subject: BIOTECNOLOGIA / ENGENHARIA BIOMEDICA Year: 2024 Document type: Article Affiliation country:

Full text: 1 Collection: 01-internacional Database: MEDLINE Language: En Journal: ACS Appl Mater Interfaces Journal subject: BIOTECNOLOGIA / ENGENHARIA BIOMEDICA Year: 2024 Document type: Article Affiliation country: