Surface Study of Lithium–Air Battery Oxygen Cathodes in Different Solvent–Electrolyte pairs

Abstract

The O2/Li2O2 electrode reaction has been studied on low surface area Au electrodes in three solvent-electrolyte pairs (0.1 M LiPF6/DMSO, LiPF6/ACN, and LiBF4/ACN) using an electrochemical cell coupled to UHV XPS spectrometer, EQCM, AFM, and DEMS. The XPS spectra of the surfaces after treatment at selected electrode potentials for the O2 reduction and reoxidation of the surface show the presence of C and S from solvent decomposition and of F and P from electrolyte decomposition. Furthermore, Li 1s and O 1s peaks due to Li2O2 and decomposition products such as carbonate, organics, LiF, high oxidation sulfur, and phosphorus compounds were also observed. Using ACN instead of DMSO results in less solvent decomposition, whereas using LiBF4 results in less electrolyte decomposition. XPS, AFM, and EQCM show that O2 reduction products removal only takes place at very high overpotentials. In agreement with XPS which shows removal of carbonate surface species, DEMS confirms evolution of CO2 and consumption of O2 at 4.5 V, but LiF cannot be removed completely in a round trip of the Li-O2 battery cathode.

Notable Reactivity of Acetonitrile Towards Li2O2/LiO2 Probed by NAP XPS During Li–O2 Battery Discharge

“…For these reasons, few works only have been devoted to the evaluation of MeCN chemical stability in Li-O 2 batteries up to now. In some reports, ex situ X-ray photoelectron spectroscopy (XPS) showed that MeCN is stable both in contact with Li 2 O 2 [33] and under Li-O 2 battery operation conditions [10]. It is also supported by cyclic voltammetry results [19].…”

“…As a result of side reactions, Coulombic efficiency of the battery drops down, and electrode surface is passivated by side products. Currently many research efforts are focused at studying the chemical stability of electrolyte components-both solvents and salts-under Li-O 2 battery operation conditions [10][11][12]. Reactions of the electrolytes with commercially available and synthesized in-house Li 2 O 2 [13,14] and KO 2 [15], which is used instead of unstable LiO 2 [16], are also often investigated.…”

Re‐weighted random series path integral simulations of molecular clusters: Applications to lithium solvated by a mixed Stockmayer cluster

“…Even though the body of knowledge gathered to date on clusters is vast, we find surprisingly little work dedicated to the study of Stockmayer and ion‐Stockmayer clusters in the literature. The present goals are of fundamental importance for the research and development of lithium ion batteries, as a practical application. Lithium ion batteries are complex bulk systems, and their direct simulations will likely require more realistic models to extend the scope of the present investigation.…”

Influence of Binders and Solvents on Stability of Ru/RuOx Nanoparticles on ITO Nanocrystals as Li–O2 Battery Cathodes

“…For the Li–O 2 system, high charge overpotentials and limited cyclability are still critical challenges to overcome. The search for highly stable electrolytes paired with stable and efficient oxygen cathodes is paramount for improving the electrochemical efficiencies and performances of non‐aqueous Li–O 2 cells, as many recent studies on surface compositions at the electrode–electrolyte interface have underlined …”

“…The search for highly stable electrolytes paired with stable and efficient oxygen cathodes is paramount for improvingt he electrochemical efficien-cies andp erformances of non-aqueous Li-O 2 cells, [7,8] as many recent studies on surfacec ompositionsa tt he electrode-electrolyte interface have underlined. [9] As far as the oxygen electrode is concerned, there is still some debate on the real need for an electrocatalyst at the cathode of the Li-O 2 system; [10] however,t he high oxidation potentiala ffects the efficiency and rechargeability on the cathode side. Some carbon structures, such as hierarchically porous graphene, effectively provide large tunnels for O 2 diffusion and small pores for an ideal oxygen reduction process.…”