Repository logo
 

Synergistic Degradation Mechanism in Single Crystal Ni-Rich NMC//Graphite Cells

Published version
Peer-reviewed

Repository DOI


Change log

Authors

paragon-plus: 5245930 
Fiamegkou, Eleni; paragon-plus: 6735118 
Gott, James A.; paragon-plus: 6206810 
Wang, Heng; paragon-plus: 6735121 
Temprano, Israel; paragon-plus: 1806052 

Abstract

Oxygen loss at high voltages in Ni-rich NMC//graphite Li-ion batteries promotes degradation, but increasing evidence from full cells reveals that the depth of discharge choice can further accelerate aging, i.e., synergistic degradation. In this Letter, we employ cycling protocols to examine the origin of the synergistic degradation for single crystal Ni-rich NMC//graphite pouch cells. In regimes where oxygen loss is not promoted (V < 4.3 V), a lower cutoff voltage does not affect capacity retention (after 100 cycles), despite significant graphite expansion occurring. In contrast, when NMC surface oxygen loss is induced (V > 4.3 V), deeper depth of discharge leads to pronounced faster aging. Using a combination of post-mortem analysis and density functional theory, we present a mechanistic description of surface phase densification and evolution as a function of voltage and cycling. The detrimental impact of this mechanism on lithium-ion kinetics is used to explain the observed cycling results.

Description

Publication status: Published

Keywords

Is Part Of

Publisher

American Chemical Society
Sponsorship
Faraday Institution (FIRG044)
Faraday Institution (FIRG060)
Faraday Institution (FIRG024)