Lithium Borate Ester Salts for Electrolyte Application in Next-Generation High Voltage Lithium Batteries

Binayak Roy, Pavel Cherepanov, Cuong Nguyen, Craig Forsyth, Urbi Pal, Tiago Correia Mendes, Patrick Howlett, Maria Forsyth, Douglas MacFarlane, Mega Kar

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33 Citations (Scopus)

Abstract

The atmospheric instability and the corrosive tendency of hexafluorophosphate [PF6] and fluorosulfonylimide [FSI] based lithium salts, respectively, are among the major impediments towards their application as electrolytes in high voltage lithium batteries. Herein a new class of Li salts is introduced and their electrochemical behavior is explored. The successful synthesis and characterization are reported, including the crystal structure, of lithium 1,1,1,3,3,3-(tetrakis)hexafluoroisopropoxy borate (LiBHfip). The oxidative stability of electrolytes of this salt in an ethylene carbonate:dimethyl carbonate mixture (v/v, 50:50) is found to be 5.0 V versus Li+/Li on various working electrodes, showing substantial improvement over a LiPF6 based electrolyte. Moreover, a high stability of an aluminum substrate is observed at potentials up to 5.8 V versus Li+/Li; in comparison, a LiFSI based electrolyte shows prominent signs of Al corrosion above 4.3 V versus Li+/Li. Cells tested with high voltage layered LiNi0.8Mn0.1Co0.1O2 (NMC811) and spinel LiMn2O4 (LMO) cathodes show stable cycling over 200 cycles with capacity retention of 76% and 90%, respectively. The LMO|Li cell maintains this same low capacity fade rate for 1000 cycles even after the salt has been exposed for 24 h to atmospheric conditions (water content ≈0.57 mass%).

Original languageEnglish
Article number2101422
Number of pages12
JournalAdvanced Energy Materials
Volume11
Issue number36
DOIs
Publication statusPublished - 23 Sept 2021

Keywords

  • hexafluoroisopropoxyborate
  • high voltage electrolytes
  • Li metal batteries
  • NMC
  • spinel LMO

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