Thermal stability in the blended lithium manganese oxide – Lithium nickel cobalt manganese oxide cathode materials: An in situ time-resolved X-Ray diffraction and mass spectroscopy study

Abstract

Thermal stabilities of a series of blended LiMn 2 O 4 (LMO)-LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) cathode materials with different weight ratios were studied by in situ time-resolved x-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25°C to 580°C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn 3 O 4 phase at around 250°C. Formation of MnO with rock-salt structure started at 520°C. This observation is in contrast to the previous report for chemically delithiated LMO in air, in which a process of λ-MnO 2 transforming to β-MnO 2 was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumption by the carbon or detection limit. CO 2 profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO 2 profile due to different MO (M=Ni, Mn, Co) phases; secondly, the onset temperature of CO 2 release is lowered, implying lowered oxygen

Multiscale Understanding of Surface Structural Effects on High‐Temperature Operational Resiliency of Layered Oxide Cathodes

“…In addition to the phase transformation, we simultaneously monitored the oxygen outgassing of 4.5 V‐charged NCM811 cathodes during heating, which can trigger the breakdown of layered structures. [ 38–41 ] As shown in Figure 5b; and Figure S8 (Supporting Information), the oxygen outgassing of delithiated bare NCM811 cathode started from ≈220 °C, which is consistent with critical temperature of the aforementioned phase transformation process, and then abruptly increased to the maximum O 2 release rate of 7.1 µL min −1 mg −1 at 265 °C. Strikingly, the coated NCM811 cathode suppressed the oxygen release with a rate of only 3.2 µL min −1 mg −1 and at a higher temperature of 276 °C.…”

Anti‐Oxygen Leaking LiCoO2

“…Considering the importance of the layered oxide cathode materials in the commercialization of the lithium‐ion batteries, various experimental studies using in situ X‐ray diffraction/absorption spectroscopy, thermal analysis, in situ transmission electron microscopy (TEM) and computational efforts were carried out to characterize and understand the oxygen‐release phenomenon and the thermal degradation mechanisms in these materials. Overall, it is understood that the extraction of Li‐ions from the cathode unit cell results in the formation of under‐coordinated oxygen atoms, which destabilizes the structure .…”

Correlation between thermal stabilities of nickel‐rich cathode materials and battery thermal runaway

“…27,28 The cracks will further lead to the decay of the surface and interior of the particles from the layered structure to the rock salt structure, releasing a large amount of oxygen and increasing the risk of thermal runaway. 29 Bak et al 30 found that for the LiNi x Mn y Co 1-x-y O 2 cathode materials, the more Ni and less Co and Mn, the lower the onset temperature of the thermal decomposition and the larger amount of oxygen release. Several researchers have also investigated the thermal stabilities of Ni-rich cathode materials and derived similar conclusions.…”