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Effect of Lithium Borate Additives on Cathode Film Formation in LiNi 0.5 Mn 1.5 O 4/Li Cells

Effect of Lithium Borate Additives on Cathode Film Formation in LiNi 0.5 Mn 1.5 O 4/Li Cells

Yingnan Dong, Benjamin T Young, Yuzi Zhang, Taeho Yoon, David R Heskett, Yongfeng Hu, Brett L Lucht

ACS Appl Mater Interfaces. 2017 Jun 21;9(24):20467-20475.

PMID: 28562011

Abstract:

A direct comparison of the cathode-electrolyte interface (CEI) generated on high-voltage LiNi0.5Mn1.5O4 cathodes with three different lithium borate electrolyte additives, lithium bis(oxalato)borate (LiBOB), lithium 4-pyridyl trimethyl borate (LPTB), and lithium catechol dimethyl borate (LiCDMB), has been conducted. The lithium borate electrolyte additives have been previously reported to improve the capacity retention and efficiency of graphite/LiNi0.5Mn1.5O4 cells due to the formation of passivating CEI. Linear sweep voltammetry (LSV) suggests that incorporation of the lithium borates into 1.2 M LiPF6 in EC/EMC (3/7) electrolyte results in borate oxidation on the cathode surface at high potential. The reaction of the borates on the cathode surface leads to an increase in impedance as determined by electrochemical impedance spectroscopy (EIS), consistent with the formation of a cathode surface film. Ex-situ surface analysis of the electrode via a combination of SEM, TEM, IR-ATR, XPS, and high energy XPS (HAXPES) suggests that oxidation of all borate additives results in deposition of a passivation layer on the surface of LiNi0.5Mn1.5O4 which inhibits transition metal ion dissolution from the cathode. The passivation layer thickness increases as a function of additive structure LiCDMB > LPTB > LiBOB. The results suggest that the CEI thickness can be controlled by the structure and reactivity of the electrolyte additive.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP244761293	Lithium bis(oxalato)borate		244761-29-3	Price

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