Issue 6, 2018

Unsymmetrical fluorinated malonatoborate as an amphoteric additive for high-energy-density lithium-ion batteries

Abstract

High-capacity Si-embedded anodes and Li-rich cathodes are considered key compartments for post lithium-ion batteries with high energy densities. However, the significant volume changes of Si and the irreversible phase transformation of Li-rich cathodes prevent their practical application. Here we report lithium fluoromalonato(difluoro)borate (LiFMDFB) as an unusual dual-function additive to resolve these structural instability issues of the electrodes. This molecularly engineered borate additive protects the Li-rich cathode by generating a stable cathode electrolyte interphase (CEI) while simultaneously tuning the fluoroethylene carbonate (FEC)-oriented solid electrolyte interphase (SEI) on the Si–graphite composite (SGC) anode. The complementary electrolyte design utilizing both LiFMDFB and FEC exhibited an improved capacity retention of 85%, a high Coulombic efficiency of ∼99.5%, and an excellent energy density of ∼400 W h kg−1 in Li-rich/SGC full cells at a practical mass loading after 100 cycles. This dual-function additive approach offers a way to develop electrolyte additives to build a more favorable SEI for high-capacity electrodes.

Graphical abstract: Unsymmetrical fluorinated malonatoborate as an amphoteric additive for high-energy-density lithium-ion batteries

Supplementary files

Article information

Article type
Paper
Submitted
04 Feb 2018
Accepted
06 Apr 2018
First published
06 Apr 2018

Energy Environ. Sci., 2018,11, 1552-1562

Unsymmetrical fluorinated malonatoborate as an amphoteric additive for high-energy-density lithium-ion batteries

J. Han, J. B. Lee, A. Cha, T. K. Lee, W. Cho, S. Chae, S. J. Kang, S. K. Kwak, J. Cho, S. Y. Hong and N. Choi, Energy Environ. Sci., 2018, 11, 1552 DOI: 10.1039/C8EE00372F

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