Failure mechanisms of LiNi0.5Mn1.5O4 electrode at elevated temperature

Anodic Oxidation of Conductive Carbon and Ethylene Carbonate in High-Voltage Li-Ion Batteries Quantified by On-Line Electrochemical Mass Spectrometry

“…Finally, by quantifying the evolution rates of 12 CO/ 12 CO 2 and 13 CO/ 13 CO 2 at 5.0 V, we demonstrate that the anodic oxidation of carbon and electrolyte can be substantial, especially at high temperature and in the presence of trace water, posing significant challenges for the implementation of 5 V cathode materials. The requirements placed on Li-ion battery technology have changed from powering small portable electronics to applications demanding high energy and high power density, such as hybrid and plug-in electric vehicles.1,2 As a result, high-voltage cathode materials have been developed that raise the cell voltage from 3.7 V in the case of a traditional LiMO 2 (M = Co, Ni, Mn) cathode to 4.8 V in new cathodes such as the high-voltage spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) or LiCoPO 4 (LCP).3-6 The state-of-the-art electrolyte, a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), dimethyl carbonate (DMC), and/or ethyl methyl carbonate (EMC) with dissolved LiPF 6 salt, tends to decompose on the surface of the delithiated cathode at potentials higher than 4.5 V vs. Li/Li + , especially at high temperature.7-12 Thus, the practical application of these high-voltage materials remains hindered by several obstacles: [13][14][15][16][17][18] (i) the limited anodic stability of electrolyte solvents and salts as well as of binders, (ii) the loss of active Li + -ions, (iii) the corrosion of the aluminum current collector, and (iv) the instability of conductive carbon additives due to anion intercalation and/or carbon oxidation.While the corrosion of conductive carbons is suggested by the frequently observed increase of the electrical resistivity of long-term cycled high-voltage cathodes, 15 quantitative measurement on the anodic decomposition of carbons have only been made in the context of Li-air battery research, making use of isotopically labeled battery components to decouple electrode and electrolyte related CO 2 evolution. For example, Thotiyl et al used a 13 C carbon cathode in DMSO and tetraglyme-based electrolyte to study CO 2 evolution from decomposition products formed with the carbon electrode ( 13 CO 2 ) and the electrolyte ( 12 CO 2 ) by in-situ differential electrochemical mass spectrometry (DEMS).…”

Effect of Pre-Cycling Rate on the Passivating Ability of Surface Films on Li4Ti5O12 Electrodes

“…2(b) implies that the initial precycling condition critically affects the subsequent charge/discharge cycling behavior of the LTO electrode. Generally, the capacity degradation of the electrodes with cycling may be attributed to two factors: 1) loss of active material and 2) increased polarization [30][31][32]. The former frequently occurs when the active material undergoes irreversible structural changes to form inactive phases.…”

Hollow spherical LiNi0.5Mn1.5O4 built from polyhedra with high-rate performance via carbon nanotube modification

“…Fig. 4a manifests the CV curves of all samples at the scan rate of 0.1 mV s −1 between 3.5-4.9 V. All samples exhibit two pairs of peaks at around 4.7 V, which can be attributed to the Ni 2+ /Ni 3+ and Ni 3+ /Ni 4+ redox pairs [33,34]. Minor redox peaks (inset of Fig.…”