Charge–discharge characteristics of natural graphite electrode in N, N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)amide containing lithium ion for lithium-ion secondary batteries

Abstract

We investigated the electrochemical characteristics of a natural graphite electrode in room-temperature ionic liquids not containing additives. N, N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)amide (DEME-TFSA) containing lithium bis(trifluoromethylsulfonyl)amide (Li-TFSA) as the electrolyte and a natural graphite electrode as the negative electrode material were employed. The charge-discharge tests showed that the discharge capacity and the charge-discharge efficiency of the natural graphite electrode at the 1st cycle were 318 mAh g -1 and 75.6%, respectively. The cycle performance showed that the discharge capacity and the charge-discharge efficiency were stably maintained at ca. 320 mAh g -1 and 100%, respectively, until the initial 10th cycle. The ex-situ X-ray diffraction measurements showed that lithium-graphite intercalation compounds, such as LiC 12 and LiC 6 , were formed after the 1st charge. The structural change in the natural graphite electrode was reversible because graphite recovered to its original structure after the 1st discharge. These results clarified that the graphite electrode could operate as a negative electrode for lithium-ion secondary batteries in DEME-TFSA containing Li-TFSA without organic solvents. Highlights:Initial characteristics of graphite at 25 o C with a capacity close to theoretical.A stable cycle performance was obtained. DEME-TFSA containing Li-TFSA provides reversible lithium ion intercalation/extraction without any additives. DEME-TFSA containing Li-TFSA may provide suitable SEI film. DEME-TFSA containing Li-TFSA may prevent undesirable side reactions.

Effect of β-Cyclodextrin on Physicochemical Properties of an Ionic Liquid Electrolyte Composed of N-Methyl-N-Propylpyrrolidinium bis(trifluoromethylsulfonyl)amide

“…At the initial anodic sweep, an anodic current is observed. This behavior is also observed for pyrrolidinium-based ILs (Towada et al, 2015; Horiuchi et al, 2016). In addition, the maximum current density of the anodic peak slightly shifts to a higher potential value with the increase in cycle number.…”

Physicochemical and electrochemical properties of N-methyl-N-methoxymethylpyrrolidinium bis(fluorosulfonyl)amide and its lithium salt composites

“…The EW value was 5. sweep. This phenomenon is not exclusive to the methoxymethyl substituent in the pyrrolidinium cation: ILs with methoxyethyl substituted ammonium cations also exhibited continuous anodic current at the initial anodic sweep [18]. The maximum current density of the oxidation peak shifted to a higher potential value at higher cycle number.…”

“…It has been reported that ILs with ether side chains, such as the N,N-diethyl-Nmethyl-N-(2-methoxyethyl)ammonium cation ([DEME] þ ) and [Pyr 1,1O2 ] þ , exhibit high ionic mobilities and excellent charge/ discharge characteristics [4e6,10,18]. As a result of the wide EW, it would be expected that [Pyr 1,1O1 ][FSA]/LiTFSA composites would exhibit excellent charge/discharge characteristics when using cathode materials with high oxidation potentials, such as LiFePO 4 , LiCoO 2 , and LiNi 1/3 Mn 1/3 Co 1/3 .Fig.…”

Analysis of Surface Deposit Formed on the Natural Graphite Negative Electrode in N, N-Diethyl-N-Methyl-N-(2-methoxyethyl) Ammonium Bis (trifluoromethylsulfonyl) Amide Containing Lithium Ion

“…In particular, the charge-discharge characteristics of the graphite electrode in the bis (trifluoromethylsulfonyl) amide (TFSA)-based RTILs without organic solvent additives are poor (2,3). In contrast, we have recently found the natural graphite electrode achieved a reasonable cycle performance in N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium (DEME)-TFSA ( Figure 1) containing lithium bis (trifluoromethylsulfonyl) amide (Li-TFSA) without organic compounds (4).…”