The roles of oxygen non-stoichiometry on the electrochemical properties of oxide-based cathode materials

Journal Article · Sat Oct 01 04:00:00 EDT 2016 · Nano Today

DOI:https://doi.org/10.1016/j.nantod.2016.08.011· OSTI ID:1373873

Zheng, Jianming; Xiao, Jie; Zhang, Ji-Guang

The capacity degradation mechanism in lithium nickel-manganese-cobalt oxide (NMC) cathodes (LiNi1/3Mn1/3Co1/3O2 (NMC333) and LiNi0.4Mn0.4Co0.2O2 (NMC442)) during high-voltage (cut-off of 4.8 V) operation has been investigated. In contrast to NMC442, NMC333 exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure, as well as interfacial degradation during high-voltage cycling, leading to a rapid increase of the electrode resistance and fast capacity decline. The fundamental reason behind the poor structural and interfacial stability of NMC333 was found to be correlated to its high Co content and the significant overlap between the Co3+/4+ t2g and O2- 2p bands, resulting in oxygen removal and consequent structural changes at high voltages. In addition, oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species, which then attack the electrode surface and form highly resistive LiF. These findings highlight that both the structural and interfacial stability should be taken into account when tailoring cathode materials for high voltage battery systems.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1373873
• Report Number(s): PNNL-SA-118289; VT1201000
• Journal Information: Nano Today, Journal Name: Nano Today Journal Issue: 5 Vol. 11; ISSN 1748-0132
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Cathode materials
High voltage spinel
Li-rich Mn-rich
Lithium ion battery
Ni-rich material
Oxygen non-stoichiometry