Fluorinated High-Voltage Electrolytes To Stabilize Nickel-Rich Lithium Batteries

Christopher Poches; Amir Abdul Razzaq; Haiden Studer; Regan Ogilvie; Bhubnesh Lama; Tula R Paudel; Xuguang Li; Krzysztof Pupek; Weibing Xing

doi:10.1021/acsami.3c06586

Fluorinated High-Voltage Electrolytes To Stabilize Nickel-Rich Lithium Batteries

ACS Appl Mater Interfaces. 2023 Sep 20;15(37):43648-43655. doi: 10.1021/acsami.3c06586. Epub 2023 Sep 11.

Authors

Christopher Poches¹, Amir Abdul Razzaq¹, Haiden Studer¹, Regan Ogilvie¹, Bhubnesh Lama², Tula R Paudel², Xuguang Li³, Krzysztof Pupek⁴, Weibing Xing¹

Affiliations

¹ Department of Mechanical Engineering, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701, United States.
² Department of Physics, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701, United States.
³ Lynntech Inc., College Station, Texas 77845, United States.
⁴ Argonne National Laboratory, Lemont, Illinois 60439, United States.

PMID: 37696006
DOI: 10.1021/acsami.3c06586

Abstract

As state-of-the-art (SOA) lithium-ion (Li-ion) batteries approach their specific energy limit (∼250 Wh kg^-1), layer-structured, nickel-rich (Ni-rich) lithium transition metal oxide-based cathode materials, e.g., LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811), have attracted great interest owing to their practical high specific capacities (>200 mAhg^-1). Coupled with their high average discharge voltages (∼4 V vs Li/Li⁺), Ni-rich cathode-based lithium batteries possess a great potential to achieve much higher specific energies (>350 Wh kg^-1 at the cell level) than the SOA Li-ion counterparts. In addition, Ni-rich oxides are low-cost battery cathode materials due to their low cobalt contents. However, Ni-rich cathode-based lithium batteries suffer quick capacity degradations upon cycling, particularly at high upper cutoff voltages (e.g., ≥4.5 V vs Li/Li⁺), due to crystal structure changes of the active cathode materials and parasitic side reactions at the electrolyte/electrode interfaces. In this study, a fluorinated-solvent-based, high-voltage stable electrolyte (HVE), i.e., 1 M Li bis(trifluoromethanesulfonyl)imide (LiTFSI) in fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate (FDEC), and methyl (2,2,2-trifluoroethyl) carbonate (FEMC) with Li difluoro(oxalate)borate (LiDFOB) additive, was formulated and evaluated in Li/NMC811 battery cells. To the best of our knowledge, this class of electrolyte has not been investigated for Ni-rich cathode-based lithium batteries. Li/NMC811 cells with HVE exhibited a superior long-term cycle performance stability, maintaining ∼80% capacity after ∼500 cycles at a high cutoff voltage of 4.5 V (vs Li/Li⁺) than a baseline carbonate-solvent-based electrolyte (BE). The superior cycle stability of the Li/NMC811 cells is attributed to the inherently high-voltage stability of HVE, supported by the physical and electrochemical analyses. This conclusion is supported by our density functional theory (DFT) modeling where HVE shows a less tendency of deprotonation/oxidation than BE, leading to the observed cycle stability. The findings in this study are important to help tackle the technical challenges facing Ni-rich cathode-based lithium batteries to realize their high energy density potentials with a long cycle life.

Keywords: density functional theory modeling; fluorinated high-voltage electrolytes; fluorinated solvents; lithium-ion batteries; nickel-rich cathodes.