INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Electrochemical and Spectroscopic Studies of Carbon Cathodes for Oxygen Reduction in DMSO Lithium Electrolytes
Autor/es:
ERNESTO JULIO CALVO; MARIA DEL POZO VAZQUEZ; SANTIAGO HERRERA; FLORENCIA MARCHINI; NATALIIA MOZHZHUKHINA; ALVARO YAMIL TESIO; WALTER RÁMON TORRES; FEDERICO WILLIAMS
Lugar:
Angra dos Reis
Reunión:
Conferencia; 16th Topical Meeting of the International Society of Electrochemistry. Electrochemical Properties and Applications of Advanced Carbon Materials; 2015
Resumen:
The rechargeable Li?air battery exhibits a very large theoretical energy density that can compete with fossil fuels for electric vehicle applications with an extended mileage range. The non-aqueous Li?air battery introduced in 1996 by Abraham consists of a lithium metal anode that dissolves in a non aqueous electrolyte and the resulting Li+ ions react with oxygen reduction products to form insoluble lithium peroxide Li2O2 at a porous carbon cathode during discharge. Among non-aqueous solvents, DMSO with a very large dipole moment and the appropriate geometry to coordinate Li+ ions stabilizes lithium ion and it has been recently proposed for rechargeable Li?O2 batteries.1 However there is a controversy at present on the stability of carbon, DMSO and lithium salts in contact with solid Li2O2.2-3We will present experimental evidence on the surface products of oxygen reduction on carbon electrodes as a function of potential and time during the discharge (ORR) and recharge of the positive electrode in lithium-air batteries.4-8Different carbon materials such as highly oriented pyrolytic graphite (HOPG), glassy carbon and Vulcan carbon black have been investigated with a variety of experimental techniques such as rotating ring-disc electrode (RRDE), differential electrochemical mass spectrometry (DEMS), X-Ray Spectroscopy with an electrochemical transfer system (EC-XPS), electrochemical quartz crystal microbalance (EQCM) and atomic force microscopy (AFM). EQCM detects co-deposition of DMSO with Li2O2 during ORR6 while AFM has shown the growth of Li2O2 at terrace edges of HOPG in the early stages of ORR and RRDE detects soluble lithium superoxide during ORR due to the solvation of Li+ by DMSO.8-9These studies have shown that while Li2O2 is the main reduction product of oxygen in DMSO lithium electrolyte, a small fraction of that is re-oxidized at 3 V since carbon, DMSO and PF6- undergo hetero-genous decomposition by contact with solid Li2O2 at potentials where ORR occur as shown in XPS experiments. The large overpotential needed to recharge these cathodes is due to oxidation of other species such as organics, carbonates, lithium fluoride, sulfate and phosphorous compounds formed in the presence of surface peroxide. During re-oxidation above 4.3 V, in situ FTIR resuls shows electrochemical oxidation of DMSO to dimethyl sulfone5, while DEMS detects formation of CO2 and consumption of O2 which reacts with DMSO oxidation intermediates.1.Peng Z., Freunberger, S.A., Chen, Y. Bruce, P.G., Science, 2012, 337, 563.2.Sharon, D., Afri, M., Noked, M, Garscuh, A., Frimer, A.A. Aurbach. D, J. Phys. Chem. Lett., 2013, 4, 2929.3.B. D. McCloskey, A. Valery, A. C. Luntz, S. R. Gowda, G. M. Wallraff, J. M. Garcia, T. Mori and L. E. Krupp, Physical Chemistry Letters, 4, 2989 (2013).4.E.J. Calvo, N. Mozhzhukhina, Electrochemistry Communications, 31 (2013) 56?58.5.N. Mozhzhukhina, L. P. Méndez De Leo, E.J. Calvo, J. Phys. Chem. C., 2013, 117, 18375−18380.6.W.R. Torres, A.Y. Tesio, E.J. Calvo, Electrochemistry Communications, 49 (2014) 38?41.7.Santiago E. Herrera, Alvaro Y. Tesio, Romain Clarenc and Ernesto J. Calvo, Physical Chemistry Chemical Physics, 2014,16, 9925-9929.8.W. Torres, N. Mozhzhukhina, A.Y. Tesio, E.J. Calvo, J. Electrochem. Soc., 161 (14) A2204-A2209 (2014).9.Semino R., Zaldivar G., Laria, D.H., Calvo, E.J., J. Chem. Phys., accepted 2014.