Mechanistic insights into cathode-driven capacity degradation of NMC111/ graphite pouch cells under long-term cycling
Creators
- 1. Marmara Univ, Dept Met & Mat Engn, RTE Campus, Istanbul, Turkiye
- 2. Koc Univ Boron & Adv Mat Applicat & Res Ctr KUBAM, TR-34450 Istanbul, Turkiye
- 3. Rail Transport Technol Inst RUTE, Sci & Technol Res Council Turkiye TUBITAK, Energy Storage Div, Kocaeli, Turkiye
- 4. Taiz Univ, Fac Appl Sci, Dept Chem, Taizi 6803, Yemen
Description
To investigate long-term degradation, 2000 mAh NMC111/graphite (Gr) pouch cells were cycled 5500 times at a 1C rate. After cycling, the resulting degradation mechanisms were systematically analyzed. Structurally, X-ray diffraction (XRD) peak shifts (003, 108, 110) revealed Jahn-Teller (JT) distortion, evidenced by an increase in the c-lattice parameter. This led to the rise in internal resistance, consistent with scanning electron microscopy (SEM) images that revealed pronounced grain deformation on the cathode. Chemically, ex-situ X-ray absorption near-edge structure (XANES) spectroscopy revealed an increase in the valence states of Mn, Ni, and Co ions, indicating significant bulk changes that could potentially destabilize the oxygen lattice. X-ray absorption fine structure (XAFS) analysis further underscored the key role of weakening transition metal-oxygen (TM-O) bonds in driving this structural deformation. At the surface, X-ray photoelectron spectroscopy (XPS) confirmed the formation of a cathode-electrolyte interphase (CEI) comprising lithium fluoride (LiF), LixPFy, and organic carbonates. The progression of these surface reactions is a key contributor to impedance growth and capacity fade over long-term cycling.
Files
bib-3980b8e4-8468-4dac-a10d-d3a9c4793c59.txt
Files
(326 Bytes)
| Name | Size | Download all |
|---|---|---|
|
md5:7a0996d4c83c20d0af8d07eb1bee803c
|
326 Bytes | Preview Download |