Combining In Situ Synchrotron X‐Ray Diffraction and Absorption Techniques with Transmission Electron Microscopy to Study the Origin of Thermal Instability in Overcharged Cathode Materials for Lithium‐Ion Batteries

Abstract

The thermal instability of the cathode materials in lithium‐ion batteries is an important safety issue, requiring the incorporation of several approaches to prevent thermal runaway and combustion. Systematic studies, using combined well‐defined in situ techniques, are crucial to obtaining in‐depth understanding of the structural origin of this thermal instability in overcharged cathode materials. Here time‐resolved X‐ray diffraction, X‐ray absorption, mass spectroscopy, and high‐resolution transmission electron microscopy during heating are combined to detail the structural changes in overcharged LixNi0.8Co0.15Al0.05O2 and LixNi1/3Co1/3Mn1/3O2 cathode materials. By employing these several techniques in concert, various aspects of the structural changes are investigated in these two materials at an overcharged state; these include differences in phase‐distribution after overcharge, phase nucleation and propagation during heating, the preferred atomic sites and migration paths of Ni, Co, and Mn, and their individual contributions to thermal stability, together with measuring the oxygen release that accompanies these structural changes. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.

Manganese based layered oxides with modulated electronic and thermodynamic properties for sodium ion batteries

“…5a, and its magnified pre-edge region is shown in its figure inset. In the pre-edge region, two peaks are observable, which is consistent with previous reports 47,48 . However, these Mn pre-edge peaks look similar for both pristine NLMO and NLMO-Zn owing to their weak intensities.…”

Distinct Surface and Bulk Thermal Behaviors of LiNi0.6Mn0.2Co0.2O2 Cathode Materials as a Function of State of Charge

“…Peaks become better defined at 300 °C and above and can be assigned to a mixture of rock salt and M 3 O 4 spinel. These phenomena are consistent with the observations in other thermally treated layered materials reported by Bak et al and Nam et al, even though different onset temperatures for the phase changes were reported because different compositions of materials were used in these reports.…”

Oxygen activation-triggered thermal instability in Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 cathode

“…Meanwhile, the (101) R peak begins to split near 37 • , transforming into the (311) S and (222) S peaks of the spinel phase within the Fd3m space group (enlarged view in the inset). [6] The XRD evolution indicates that layered NCM starts to transform into the spinel phase as low as 150 The XRD peak evolution is consistent with previous works by Yang et al [6] and Nam et al [5] . Such changes imply that the delithiated NCM811 fully transforms from the spinel to the rock-salt phase at 450 • C. The structural transformation from the layered (R 3m) to spinel (Fd3m), and finally to rock-salt (Fm3m) phase is consistent with the SEM morphology change, where internal strain from lattice mismatch gradually leads to crack formation.…”