To clarify the relationship between Li + transport rate in glyme-based electrolytes and Li deposition/dissolution behavior at Li metal negative electrode (NE) in Li-air batteries (LAB) systems, 1.0 M tetraglyme (G4) electrolytes were prepared containing a Li salt of LiSO 3 CF 3 , LiN(SO 2 CF 3 ) 2 , or LiN(SO 2 F) 2 . Two aspects of Li + transfer between the two phases, i.e., G4 electrolyte | Li metal NE, were evaluated, namely i) Li + supplying rate and ii) Li + charge transfer rate through solid electrolyte interphase (SEI) films. The former was investigated by self-diffusion coefficients D of Li + , anions, and G4 solvent together with ionic conductivity σ, viscosity, density, and apparent dissociation degree α app of the Li salts estimated by the Nernst-Einstein equation. The latter was evaluated with Li | Li symmetric and LAB (Li | O 2 ) cells containing the electrolytes. The Li deposition/dissolution reaction basically depended on the Li + supplying rate in the Li | Li cell; however Li dendrites were formed. Conversely, the LAB cell performance was controlled by Li oxide layers formed on the NE, resulting in similar discharge/charge properties without Li dendrites. The effects of surface-oxidation was also confirmed with Li | Li cells containing O 2 gas, where both SEI and charge transfer resistances were In recent years, rechargeable non-aqueous Li-air batteries (LABs) have received increasing attention as large-scale energy storage devices for long-range electric vehicles (EVs), because of their high energy density, more than five times greater than that of conventional Liion batteries (LIBs).1-4 However, some problems need to be addressed to enable the realization of this technology, including choking of the air electrode by Li 2 O 2 generated during discharging and the high overpotential required by Li 2 O 2 oxidation reaction during charging. These factors lead to oxidative deterioration of the electrolytes and the air electrode, which consists of porous carbon materials. At the Li metal negative electrode (NE), Li dendrite growth during discharge/charge cycles also poses serious safety problems. 15 has been suggested as a way of avoiding the short circuiting of cells caused by Li dendrite growth. However, the additives commonly used to control the solid electrolyte interphase (SEI) film do not effectively work in LAB systems. In these systems the Li dissolution/deposition reaction is repeated many times and O 2 gas is fed in from the air electrode, resulting in destabilization of the SEI films. Furthermore, carbonatetype electrolytes are decomposed by O 2 − radicals generated at the air electrode during the discharge process. Recently, ether-based electrolytes, based on 1,2 dimethoxyethane (DME or G1), diglyme (G2), triglyme (G3), or tetraglyme (G4) as a solvent, have been widely investigated for non-aqueous LAB systems. 16 These ethers have high oxygen solubility and relatively low electric constants, resulting in lower reactivity toward O 2 − radicals than that of carbonate-based electrolytes.17 H...

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Acid-treated Ketjen Black (a-KB) carbon supports were prepared to investigate how oxidation of the carbon surface influences La 0.6 Sr 0.4 MnO 3 (LSM) nanoparticle distribution, and conjugation to the carbon support. 30 wt.% LSMloaded a-KB (LSM/a-KB) materials were prepared as air-electrode catalysts for rechargeable lithium-air batteries (LABs). a-KB exhibited a significant degree of O-containing (C-O, COO) surface functional groups, which resulted in the formation of smaller LSM nanoparticles and enhanced homogeneity over the carbon support when compared with the pristine KB support. Consequently, C-O-Mn bonds were formed, which increased the Mn oxidation state, and concomitantly enhanced conjugation resulting in improved catalytic activity. Additionally, the overpotential was reduced during charging (Li 2 O 2 decomposition). Furthermore, LSM/a-KB enhanced the cyclability of the LAB test cell. Scanning electron microscopy observations revealed that LSM/a-KB efficiently decomposed the Li 2 O 2 deposition layer, even after the 15th charge cycle when compared with LSM/KB. The LSM/a-KB air-electrode exhibited a more homogeneous and smaller-sized (and/or amorphous) Li 2 O 2 deposition after discharging. Therefore, the oxidation of the carbon surface, resulting in enhanced LSM nanoparticle distribution on, and conjugation to, the a-KB surface, influences the homogeneity of the Li 2 O 2 deposition onto the support during the discharge process leading to its facile decomposition during the following charge process.

To clarify the relationship between ion transport behavior and Li deposition/dissolution reaction at Li metal negative electrode (NE) for Li-air batteries, 1.0 M of LiSO 3 CF 3 /tetraglyme(G4) and LiN(SO 2 CF 3 ) 2 /G4 electrolytes were selected, and the Li + transport were evaluated from two aspects, i.e. i) Li + supplying rate to the Li metal NE and ii) charge transfer rate through solid state interphase (SEI) films at Li metal NE. For the former aspect, self-diffusion coefficients D of Li + , anion and G4 solvent together with viscosity , density , ionic conductivity  of electrolytes were measured, and the degree of apparent dissociation  app of Li salts was also estimated from the D and . On the other hand, the later aspect was examined with Li | Li symmetric cells containing the glymebased electrolytes. As a result, the LiN(SO 2 CF 3 ) 2 /G4 having a higher supplying rate, i.e. , owing to its higher  app exhibited an excellent Li deposition/dissolution and Li-air cell performance.

The cycle stability of lithium negative electrodes for Li–air secondary batteries was studied under oxygen atmosphere using Li∣Li symmetric cells with three organic electrolyte solutions: 1.0 M LiCF3SO3/tetraglyme (G4), 1.0 M LiN(SO2CF3)2/G4, and 1.0 M LiNO3/G4. Of these, 1.0 M LiNO3/G4 showed excellent stability without dendrite deposition, even for increased dissolution/deposition capacity from 0.50 to 2.0 mAh cm−2. These results are considered to be due to the stable Li2O passivation layer that was formed, not only by the direct reaction with oxygen, but also by the action of NO3 − as an oxidant, which released NO2 − as a redox mediator. Li–O2 cells with 1.0 M LiNO3/G4 showed a clear charging voltage plateau at 3.7 V, which evidenced the redox mediator effect of NO2 −, and cell cycleability was enhanced to 25 cycles.