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| Home > Publications database > Investigation of the Degradation Mechanism of Ni-rich NMC Cathode Material in Lithium-Ion Batteries |
| Conference Presentation (After Call) | FZJ-2024-00493 |
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2023
Abstract: Lithium-ion batteries (LIBs) are state-of-the-art battery systems for electrical vehicles (EVs) and thus a key-technology for an emission-reduced future [1]. Besides anode and electrolyte, the cathode site plays an important role for the performance of a battery. Ni-rich NMC (LixNiyMnzCo1-y-zO2, with x > 0, y > 0.6) is the most promising candidate of cathode materials due to its high capacity, high energy density and low costs [1]. However, structural instability is a drawback of a high nickel content leading e.g., to phase transition under high voltages, washing and heat treatment [1,2]. Although it is clear, that a phase transition from layered structure (space group R-3m) over an intermediate spinel-phase (space group Fd-3m) to rocksalt structure (space group Fm-3m) takes place, it is controversially discussed how fast and thick the rocksalt layer grows and if it has a positive influence on the electrochemical performance up to a certain thickness [3-5].One urgent question is, how fast and heavily Ni-rich NMC degrades if it is held at high voltages for long timespans. To answer this question, battery cells were set to 4.5 V for a varying number of days.The formed rocksalt layers were imaged at the atomic scale using scanning transmission electron microscopy (STEM) to obtain valuable information about the phase transition occurring at the surface of the particles. Figure 1 shows STEM images of a battery cell after 30 days, where a pronounced rocksalt layer of roughly 20 nm is visible, indicating degradation of the cathode.The time-dependent study provides a better understanding of the aging of Ni-rich NMC cathodes caused by cut-off voltages.
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