A single lithium-ion conducting monomer as a SEI-forming additive for lithium-ion batteries

Abstract

A novel single lithium-ion conducting (SLIC) monomer, lithium((4-(methacryloyloxy)phenyl)sulfonyl)((trifluoromethyl)sulfonyl)imide (LiMPTFSI) was designed and synthesized as a solid-electrolyte interphase (SEI)-forming additive. The formation of a single lithium-ion conducting polymeric SEI on the surface of a graphite anode was confirmed by nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The thin and stable SLIC polymer layer formed by LiMPTFSI on the graphite anode effectively suppressed the reductive decomposition of the liquid electrolyte. Based on the excellent electrochemical properties of the polymeric SEI, the graphite/LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) full cells employing LiMPTFSI exhibited a high capacity retention of 71.0% after 1000 cycles at a rate of 1.0C and 25 °C. The cell containing LiMPTFSI also exhibited excellent rate capability, which was approximately 2-fold higher than the discharge capacity of the lithium-ion cell without the additive at 5.0C rate.