Quantifying Degradation Parameters of Single-Crystalline Ni-Rich Cathodes in Lithium-Ion Batteries
Journal article, 2023
Single-crystal LiNixCoyMnzO2 (SC-NCM, x+y+z=1) cathodes are renowned for their high structural stability and reduced accumulation of adverse side products during long-term cycling. While advances have been made using SC-NCM cathode materials, careful studies of cathode degradation mechanisms are scarce. Herein, we employed quasi single-crystalline LiNi0.65Co0.15Mn0.20O2 (SC-NCM65) to test the relationship between cycling performance and material degradation for different charge cutoff potentials. The Li/SC-NCM65 cells showed >77 % capacity retention below 4.6 V vs. Li+/Li after 400 cycles and revealed a significant decay to 56 % for 4.7 V cutoff. We demonstrate that the SC-NCM65 degradation is due to accumulation of rock-salt (NiO) species at the particle surface rather than intragranular cracking or side reactions with the electrolyte. The NiO-type layer formation is also responsible for the strongly increased impedance and transition-metal dissolution. Notably, the capacity loss is found to have a linear relationship with the thickness of the rock-salt surface layer. Density functional theory and COMSOL Multiphysics modeling analysis further indicate that the charge-transfer kinetics is decisive, as the lower lithium diffusivity of the NiO phase hinders charge transport from the surface to the bulk.
Single-Crystal Cathodes
Transfer Kinetics
Structural Stability
Rock-Salt Formation
Multiphysics Analysis
Author
Wengao Zhao
Swiss Federal Laboratories for Materials Science and Technology (Empa)
Karlsruhe Institute of Technology (KIT)
Kuan Wang
Beijing University of Technology
Xinming Fan
Central South University
Fucheng Ren
Xiamen University
Xieyu Xu
Xi'an Jiaotong University
Yangyang Liu
Xi'an Jiaotong University
Shizhao Xiong
Chalmers, Physics, Materials Physics
Xiangsi Liu
Xiamen University
Zhengfeng Zhang
Beijing University of Technology
Mayan Si
Swiss Federal Laboratories for Materials Science and Technology (Empa)
Ruizhuo Zhang
Karlsruhe Institute of Technology (KIT)
Wessel van den Bergh
Karlsruhe Institute of Technology (KIT)
Pengfei Yan
Beijing University of Technology
Corsin Battaglia
Swiss Federal Laboratories for Materials Science and Technology (Empa)
Torsten Brezesinski
Karlsruhe Institute of Technology (KIT)
Yong Yang
Xiamen University
Angewandte Chemie - International Edition
1433-7851 (ISSN) 1521-3773 (eISSN)
Vol. 62 32 e202305281Subject Categories
Materials Chemistry
DOI
10.1002/anie.202305281
PubMed
37279438