A Long-Life Lithium Ion Battery with Enhanced Electrode/Electrolyte Interface by Using an Ionic Liquid Solution

Abstract

In this paper, we report an advanced long-life lithium ion battery, employing a Pyr14 TFSI-LiTFSI non-flammable ionic liquid (IL) electrolyte, a nanostructured tin carbon (Sn-C) nanocomposite anode, and a layered LiNi1/3 Co1/3 Mn1/3 O2 (NMC) cathode. The IL-based electrolyte is characterized in terms of conductivity and viscosity at various temperatures, revealing a Vogel-Tammann-Fulcher (VTF) trend. Lithium half-cells employing the Sn-C anode and NMC cathode in the Pyr14 TFSI-LiTFSI electrolyte are investigated by galvanostatic cycling at various temperatures, demonstrating the full compatibility of the electrolyte with the selected electrode materials. The NMC and Sn-C electrodes are combined into a cathode-limited full cell, which is subjected to prolonged cycling at 40 °C, revealing a very stable capacity of about 140 mAh g(-1) and retention above 99 % over 400 cycles. The electrode/electrolyte interface is further characterized through a combination of electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) investigations upon cell cycling. The remarkable performances reported here definitively indicate that IL-based lithium ion cells are suitable batteries for application in electric vehicles.

Keywords: electrochemistry; ionic liquids; lithium-ion batteries; nanostructures.