Indigo as Single Additive in Liquid Electrolyte for Lithium Metal Batteries

Rechargeable lithium ion batteries (LIBs) have been successfully developed and widely used to power today’s portable electronic devices. The long term success in electric vehicles and energy storage system relies on rising the energy density, low temperature efficiency, safety and increased cycle life.<br/>In parallel, lithium metal batteries (LMBs), described as a system with Li⁰ as anode and metal oxide as cathode (NMC, LFP, LMO) are arising as aim of research for a plethora of groups. Lithium metal anode is considered as ideal anode due to high theoretical capacity (3860 mAhg^-1), lower negative electrochemical potential and lower density (0.534 g.cm^-3).¹ Researchers used complex liquid electrolyte (ionic liquid, etc.) systems in order to avoid lithium dendrite and degradation, conventional liquid electrolyte (LiPF₆, carbonate solvants) degraded faster than expected, and consequently, generated cells fading. Therefore conventional liquid electrolyte in such cell was not used.<br/>Use of organic additives in electrolyte and/or electrodes is considered as one of the most economical and effective approaches for solving many problems as cited previously. The additive can interact with electrolyte or anode to prevent degradation or enhanced cell performances.<br/>This presentation will outline commercial organic compounds: Indigo and his derivatives use as single additive in NMC/Li batteries with conventional liquid electrolyte, which considerably increased the cycle life of Li metal batteries. Dyes such Indigoïd contain electron density donor (-NH-) and acceptor (-C=O) groups linked by conjugated bonds, which participate to their versatile electrochemical properties.<br/><br/>When used as additive in cathode materials or electrolyte, indigo modified the electrode structure and changed the composition of the Li-ions battery electrolyte and solid electrolyte interface (SEI) on lithium metal.<br/> <br/>^1.Zhang, H., Eshetu, G.G.,Judez, X., Li, C., Armand, M., Angew. Chem. Int. Ed. 2018, 57, 15002-15027