A Comprehensive Understanding of the Aging Effects of Extreme Fast Charging on High Ni NMC Cathode

Tanvir Tanim, Zhenzhen Yang, Donal Finegan, Parameswara Chinnam, Yulin Lin, Peter Weddle, Ira Bloom, Andrew Colclasure, Eric Dufek, Jianguo Wen, Yifen Tsai, Michael Evans, Kandler Smith, Jeffery Allen, Charles Dickerson, Alexander Quinn, Alison Dunlop, Stephen Trask, Andrew Jansen

Research output: Contribution to journalArticlepeer-review

34 Scopus Citations

Abstract

Extreme fast charging (XFC, =10-15 min charging) is expected to increase the adoption of electric vehicles (EVs), but currently accelerates degradation in Li ion cells. As the battery industry shifts toward high Ni content cathodes, such as LiNi0.8Mn0.1Co0.1O2 [NMC811] -- due to its higher specific capacity, better transport properties, and lower Co content -- a complete understanding of the degradation mechanisms of NMC811 under XFC conditions, and how those compare to lower Ni content cathodes, like LiNi0.5Mn0.3Co0.2O2 [NMC532], is needed. Such comprehensive understanding would identify the most critical materials gaps that need to be addressed for enabling XFC long-life cells for EVs. Using well-defined cells and charging protocols, this study maps out the key aging mechanisms for NMC811 cycled at different XFC conditions [at 1C-9C to 4.1V (~100% state-of-charge [SOC]) and at 9C to 3.63V (~35% SOC), 3.77V (~60% SOC), and 3.94V (~80% SOC)] for up to 1000 cycles. To acquire a fundamental understanding of utilization and degradation, cells were evaluated using a range of electrochemical techniques, and a suite of multimodal and multiscale microscopy techniques to quantify chemical, structural, and crystallographic degradation as a function of cycling conditions for the NMC cathode. When comparing NMC532 to NMC811, it is observed that NMC811 has a greater subsurface crystallographic degradation from layered to rock salt structures and displays a similar magnitude of sub particle cracking. However, the NMC811 maintains superior performance despite those advanced degradations. The superior cycle life performance is attributed to the NMC811 particles having radially oriented grains and improved transport properties. NMC811 showed between 4.6× to 3.15× reduction in capacity fade than NMC532 for charging rates between 4C (e.g., 15-minute charging) and 6C (10-minute charging).
Original languageAmerican English
Article number2103712
Number of pages17
JournalAdvanced Energy Materials
Volume12
Issue number22
DOIs
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 Wiley-VCH GmbH.

NREL Publication Number

  • NREL/JA-5700-81576

Keywords

  • cathode degradation
  • extreme fast charging
  • lithium-ion batteries

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