期刊
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
卷 168, 期 11, 页码 -出版社
ELECTROCHEMICAL SOC INC
DOI: 10.1149/1945-7111/ac39fc
关键词
Batteries-Li-ion; Artifical graphite; natural graphite; long lifetime; safety
资金
- NSERC/Tesla Canada Industry Research Chair program
- Vanier CGS program
- Killam Foundation
- Nova Scotia Graduate scholarship program
This study investigates the impact of graphite materials on the performance of NMC811/graphite cells, revealing differences between natural and artificial graphite and the importance of the electrochemically accessible area in optimizing graphite-containing cells. The research demonstrates that advanced artificial graphite materials can improve safety and cycling performance compared to natural graphite materials.
The impact of graphite materials on capacity retention in Li-ion cells is important to understand since Li inventory loss due to SEI formation, and cross-talk reactions between the positive and negative electrodes, are important cell failure mechanisms in Li-ion cells. Here, we investigate the impact of five graphite materials from reputable suppliers on the performance of NMC811/graphite cells. We show that natural graphites (NG) here have a mixture of 3R and 2H phases, while artificial graphites (AG) were 2H only. We find that there are differences between the N-2 BET surface area and the electrochemically-accessible area where redox reactions can take place and it is the latter that is most important when optimizing graphite-containing cells. Part I of this 2-part series investigates physical and electrochemical differences between the graphite materials of interest here, as well as room temperature cycling to probe improvements in capacity retention. We demonstrate that advanced AG materials with small accessible surface areas can improve safety, 1st cycle efficiency (FCE) and long-term cycling compared to NG materials with higher accessible surface areas. Part II of this work examines elevated temperature cycling, cell swelling, and makes lifetime predictions for the best NMC811/graphite cells.
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