Enhancing the performance of lithium oxygen batteries through combining redox mediating salts with a lithium protecting salt

Multicomponent Phase Separation in Ternary Mixture Ionic Liquid Electrolytes

“…In a process resembling the phase separation of IL mixtures, − the electrolyte was separated into two domains; a domain primarily composed of ionic species and another domain composed of only G4 molecules. Similar domain formations were recently observed in ternary mixtures of IL, G4, and Li salts by small-angle X-ray scattering experiments . In order to characterize this phenomenon, we investigated multiple cases by (i) changing the volume fraction of G4 and ILs, (ii) changing the salt concentration, and (iii) changing the temperature.…”

“…Recently, ternary mixtures of organic solvents, ionic liquids (ILs), and Li salts have shown outstanding performance in Li-ion and Li–oxygen batteries, outperforming both binary mixtures of organic solvents or ILs with Li salt electrolytes. − The binary IL-based electrolytes, despite their remarkable thermal, chemical, and electrochemical stabilities, very low vapor pressure, and nonflammability, have a high viscosity that negatively affects ion transport. − On the other hand, binary electrolytes based on organic solvents exhibit better transport characteristics, but a majority of them are only stable in a narrow electrochemical potential window. − A common strategy to overcome these issues is to use a combination of ILs and low-viscosity organic solvents with Li salts to form ternary mixtures. − In particular, Li salts such as LiI and LiNO 3 are added to Li–air battery electrolytes to improve cyclability and provide a protective solid electrolyte layer on the anode …”

“…17−20 In particular, Li salts such as LiI and LiNO 3 are added to Li−air battery electrolytes to improve cyclability and provide a protective solid electrolyte layer on the anode. 21 The improved ion transport of ternary mixtures compared to IL-based electrolytes is mainly attributed to the change in the nature of interactions among different components of the mixture. 22−25 Historically, ILs and their mixtures were considered as homogeneous and coherent bulk systems.…”

“…Similar domain formations were recently observed in ternary mixtures of IL, G4, and Li salts by small-angle X-ray scattering experiments. 21 ■ METHODS System Setup. Simulation systems consist of tetraglyme (G4), [EMIM][BF 4 ] IL, and two salts LiNO 3 and LiI (Figure 1).…”

Li-O2 Battery Discharge Redox Mediation by Triarylmethyl Cations

“…However, inability to tune oxidation potentials through synthetic design and negative effects on battery efficiency, resulting from altered discharge products and corrosive side reactions, have led researchers to explore organic compounds for charging redox mediation 26,27,29 . Many compounds and functional groups have been investigated and shown success in reducing the charging overpotential 11,20,24,[30][31][32][33][34][35][36][37][38][39][40] , but the majority of them have shown poor long-term stability and performance loss after many discharge-charge cycles 41,42 . The πsystem containing cores of many redox mediators have a propensity to react with in situ generated 1 O2, leading to deactivation [42][43][44][45] .…”