The Study of Surface Phenomena Related to Electrochemical Lithium Intercalation into Li[sub x]MO[sub y] Host Materials (M = Ni, Mn)

Abstract

We report herein on the comparative study of LiNiO2 and LiMn2O4 electrodes in three salt solutions, namely, LiAsF6 , LiPF6 , and normalLiCfalse(SO2CF3)3 in a mixture of the commonly used ethylene and dimethyl carbonates. The surface chemistry of the electrodes in these solutions was studied by surface‐sensitive Fourier transform infrared spectroscopy. X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray analysis, and their electrochemical behavior was studied by variable‐scan‐rate voltammetry and impedance spectroscopy. It was found that the electrochemical behavior of these electrodes is strongly dependent on their surface chemistry. Complicated reactions between the active mass and solution components, which include the solvents, the salt anions, and unavoidable contaminants such as HF and perhaps, HSO3CF3 , lead to the precipitation of surface films through which the Li ion has to migrate in order to reach the active mass. The impedance spectroscopy of these electrodes clearly reflects their surface chemistry. It demonstrates the serial nature of the Li insertion‐deinsertion processes, which includes, in addition to solid‐state diffusion and accumulation, Li‐ion migration through surface films and their charge transfer across the surface film/active mass interface, which strongly depends on the chemical composition of the surface films and hence, the solution chosen. LiNiO2 is considerably more reactive with these solutions than LiMn2O4 , probably due to its stronger nucleophilic nature. In addition, in LiPF6 solutions, the electrodes' impedance is higher due to precipitation of films comprising LiF, which is highly resistive to Li ion transport (probably produced by reactions of the LixMOy active mass with trace HF). © 2000 The Electrochemical Society. All rights reserved.

Effect of Calcination Temperature of Size Controlled Microstructure of LiNi0.8Co0.15Al0.05O2Cathode for Rechargeable Lithium Battery

“…The I (003) /I (104) ratio has been used as an indicator of cation mixing, 17 that is, values lower than 1.3 indicate a high degree of cation mixing, due to occupancy by other ions in the lithium interslab region 18 and the reversible capacity of the cathode material tends to decrease when the ratio is less than 1.2. [19][20][21] In this work, the calcined at 750 o C sample shows the highest ratio I(003)/I(104) of 1.65, indicating that this sample has the lowest amount of cation mixing, meaning a very small concentration of Ni 2+ ions in the Li (3b) interlayer sites. However, as the calcination temperature increases to 850 o C, the ratio of I(003)/I(104) decreases dramatically, indicating that this sample has a high cation mixing.…”

Von Lithium‐ zu Natriumionenbatterien: Vorteile, Herausforderungen und Überraschendes

“…Die sogenannte Kathoden-Elektrolyt-Grenzschicht wurde fürv erschiedene positive Lithium-Elektroden bereits vor einiger Zeit diskutiert, z. B. von Aurbach et al [35] sowie Edstrom et al [36] Das Verständnis dieser Filmbildung sowie die gezielte Einstellung der Filmeigenschaften durch Additive stellt eine anspruchsvolle und wichtige Aufgabe dar, um die Langzeitstabilitätd er positiven Elektroden weiter zu verbessern. Dies ist insbesondere fürH ochspannungsmaterialien wie LiNi 0.5 Mn 1.5 O 4 relevant.…”

Characterization of SEI layers on LiMn2O4 cathodes with in-situ spectroscopic ellipsometry

“…Peled (1979) introduced the idea of the SEI layer on alkali and alkaline earth metals in organic electrolytes [1]. SEI layer formation has been observed for various electrode materials such as Li foil, carbon, and transition metal oxides [2][3][4][5][6][7][8][9][10][11][12]. The SEI layer plays a key role in the electrochemical performance and calendar life of Li-ion batteries because it prevents the electrode surface from further reacting with the electrolyte components, thereby increasing the cell impedance and decreasing its cycling efficiency [13].…”

“…The SEI layer plays a key role in the electrochemical performance and calendar life of Li-ion batteries because it prevents the electrode surface from further reacting with the electrolyte components, thereby increasing the cell impedance and decreasing its cycling efficiency [13]. Due to its important role in Li-ion batteries, a number of analytical techniques, such as X-ray photoelectron spectroscopy (XPS) [2-4, 10,11], nuclear magnetic resonance (NMR) [8], Fourier transform infrared (FTIR) spectroscopy [9][10][11], etc., have been employed to study the nature and formation mechanisms of the SEI layer.…”

“…Aurbach et al. found that a SEI layer, which consisted mainly of ROLi, ROCO 2 Li, polycarbonates 4 and some salt-reduction products such as LiF, replaced the nascent Li 2 CO 3 surface films on cathode particles (LiNiO 2 and LiMn 2 O 4 ) when batteries were stored or cycled [9,10].…”