| Autor: |
Hestenes JC; Program of Materials Science and Engineering, Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York10027, United States., Sadowski JT; Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York11973, United States., May R; Department of Chemical Engineering, Columbia University, New York, New York10027, United States., Marbella LE; Department of Chemical Engineering, Columbia University, New York, New York10027, United States. |
| Jazyk: |
angličtina |
| Zdroj: |
ACS materials Au [ACS Mater Au] 2022 Nov 10; Vol. 3 (2), pp. 88-101. Date of Electronic Publication: 2022 Nov 10 (Print Publication: 2023). |
| DOI: |
10.1021/acsmaterialsau.2c00060 |
| Abstrakt: |
The high-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) spinel cathode material offers high energy density storage capabilities without the use of costly Co that is prevalent in other Li-ion battery chemistries (e.g., LiNi x Mn y Co z O 2 (NMC)). Unfortunately, LNMO-containing batteries suffer from poor cycling performance because of the intrinsically coupled processes of electrolyte oxidation and transition metal dissolution that occurs at high voltage. In this work, we use operando electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies to demonstrate that transition metal dissolution in LNMO is tightly coupled to HF formation (and thus, electrolyte oxidation reactions as detected with operando and in situ solution NMR), indicative of an acid-driven disproportionation reaction that occurs during delithiation (i.e., battery charging). Leveraging the temporal resolution (s-min) of magnetic resonance, we find that the LNMO particles accelerate the rate of LiPF 6 decomposition and subsequent Mn 2+ dissolution, possibly due to the acidic nature of terminal Mn-OH groups. X-ray photoemission electron microscopy (XPEEM) provides surface-sensitive and localized X-ray absorption spectroscopy (XAS) measurements, in addition to X-ray photoelectron spectroscopy (XPS), that indicate disproportionation is enabled by surface reconstruction upon charging, which leads to surface Mn 3+ sites on the LNMO particle surface that can disproportionate into Mn 2+ (dissolved) and Mn 4+ (s) . During discharge of the battery, we observe high quantities of metal fluorides (in particular, MnF 2 ) in the cathode electrolyte interphase (CEI) on LNMO as well as the conductive carbon additives in the composite. Electronic conductivity measurements indicate that the MnF 2 decreases film conductivity by threefold compared to LiF, suggesting that this CEI component may impede both the ionic and electronic properties of the cathode. Ultimately, to prevent transition metal dissolution and the associated side reactions in spinel-type cathodes (particularly those that operate at high voltages like LNMO), the use of electrolytes that offer improved anodic stability and prevent acid byproducts will likely be necessary.
Competing Interests: The authors declare no competing financial interest.
(© 2022 The Authors. Published by American Chemical Society.) |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
