Mechanistic insights into cathode-driven capacity degradation of NMC111/graphite pouch cells under long-term cycling

Ateş M. N., Zengin F., Whba R., TUNABOYLU B., Aydemir U., Peighambardoust N. S., ...Daha Fazla

Electrochimica Acta, cilt.543, 2025 (SCI-Expanded, Scopus) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 543
  • Basım Tarihi: 2025
  • Doi Numarası: 10.1016/j.electacta.2025.147611
  • Dergi Adı: Electrochimica Acta
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Chimica, Compendex, INSPEC
  • Anahtar Kelimeler: Batteries, Capacity fade, Cathode-electrolyte interphase, NMC111, Pouch cell
  • İnönü Üniversitesi Adresli: Evet

Özet

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.