High Voltage LiNi0.5Mn1.5O4/Li4Ti5O12 Lithium Ion Cells at Elevated Temperatures: Carbonate- vs. Ionic Liquid-Based Electrolytes

Cao X, He X, Wang J, Liu H, Röser S, Rezaei Rad B, Evertz M, Streiprt B, Li J, Wagner R, Winter M, Cekic-Laskovic I

Abstract

Thanks to its high operating voltage, LiN i 0.5 Mn 1.5 O 4 (LNMO) spinel represents a promising next%generation cathode material candidat e for Lithium ion batteries. However, LNMO based full%cells with organic carbonate solven t electrolytes suffer from severe capacity fading issues, associated with electrolyte decompos ition and concurrent degradative reactions at the electrode/electrolyte interface, especially at elevated temperatures. As promising alternatives, two selected LiTFSI/pyrrolidinium bis(trifluorometh ane%sulfonyl)imide room temperature ionic liquid (RTIL) based electrolytes with inherent ther mal stability were investigated in this work. Linear sweep voltammetry (LSV) profiles of the inve stigated LiTFSI/RTIL electrolytes display much higher oxidative stability compared to the sta te%of%the%art LiPF 6 /organic carbonate based electrolyte at elevated temperatures. Cycling perfo rmance of the LNMO/Li 4 Ti 5 O 12 (LTO) full% cells with LiTFSI/RTIL electrolytes reveals remarka ble improvements in respect to capacity retention and Coulombic efficiency. Scanning electr on microscopy (SEM) images and X%ray diffraction (XRD) patterns indicate maintained pris tine morphology and structure of LNMO particles after 50 cycles at 0.5C. Investigated LiT FSI/RTIL based electrolytes outperform the LiPF 6 /organic carbonate%based electrolyte in terms of cy cling performance in LNMO/LTO full% cells at elevated temperatures.