Open AccessTransition Metal Dissolution and Degradation in NMC811-Graphite Electrochemical Cells
Author(s) -
Zachary Ruff,
Chao Xu,
Clare P. Grey
Publication year - 2021
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/ac0359
Subject(s) - dissolution , anode , cathode , materials science , electrolyte , electrochemistry , nickel , graphite , manganese , transition metal , degradation (telecommunications) , chemical engineering , oxide , leaching (pedology) , metallurgy , inorganic chemistry , chemistry , electrode , telecommunications , biochemistry , environmental science , computer science , soil science , engineering , soil water , catalysis
Nickel-rich lithium nickel-manganese-cobalt oxide cathodes, in particular Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 (NMC811), are currently being commercialized as next generation cathode materials, due to their increased capacities compared to current materials. Unfortunately, the higher nickel content has been shown to accelerate cell degradation and a better understanding is needed to maximize cell lifetimes. NMC811/graphite cells were tested under stressed conditions (elevated temperature and cell voltages) to accelerate degradation focusing on transition metal (TM) dissolution from the cathode. Increasing the cell temperature, upper cut-off voltage (UCV) and number of cycles all accelerated capacity fade and diffraction studies showed that under stressed conditions, additional degradation mechanisms beyond lithium loss to the SEI are present. Significant TM dissolution and subsequent deposition on the graphite anode is seen, particularly at stressed conditions. The concentration of TMs in the electrolyte remained invariant with cycling conditions, presumably reflecting the limited solubility of these ions and emphasizing the role that TM deposition on the anode plays in continuing to drive dissolution. Significant deposits of metals from the cell casings and current collectors were also detected at all cycling conditions, indicating that corrosion and metal leaching can be as important as TM dissolution from the active material in some cell formats.