Electrochemical Performance of Anatase TiO₂Nanotube Arrays Electrode in Ionic Liquid Based Electrolyte for Lithium Ion Batteries

Abstract

Ternary electrolyte composed of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid (PYR 14 TFSI), γ-butyrolactone (GBL) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and anatase TiO 2 nanotube arrays (NTAs) electrode are investigated for the application in new generation of lithium-ion batteries (LIBs). The electrical conductivity and viscosity are measured in the whole composition range at several temperatures. Also, cyclic voltammetry experiments are performed at different temperatures and scan rates. At all scan rates, up to 100 mV · s −1 Ti 4+ /Ti 3+ redox peaks appear designating exceptionally fast intercalation/deintercalation reaction. At the end of cycling the intercalation/deintercalation capacity was 144.8/140.7 mAh · g −1 at current rate 3 C. The diffusion coefficient for Li + extraction from TiO 2 nanotubes (NTs) have been calculated for temperatures from (25 to 55) • C. Activation energy for diffusion was found to be 54.7 kJ/mol (0.57 eV The rapid development of portable electronic devices and technologies significantly increased demand for the next generation of energy storage systems.1 Because of enhanced energy and power density, efficiency and long life, LIBs are currently one of the most promising energy storage devices.2,3 Improvement of safety standards and low impact on human health and environment is essential for large-scale application of LIBs. 4 Safety concerns related to utilization of highly volatile and flammable organic solvents in commercial cells can be addressed by introducing ionic liquids (ILs) as emerging class of fluids.5 Numerous advantages of ILs such as negligible vapor pressure and high chemical and thermal stability make them ideal candidates for their application in LIBs. Potential application of ILs based on a combination of the pyrrolidinium (PYR + ) cation and bis(trifluoromethanesulfonyl)imide (TFSI -) anion as electrolytes in LIBs with long term cycling stability and very good capacity utilization, has been confirmed by several research groups. [6][7][8][9][10][11][12] Nevertheless, the utilization of IL-based electrolytes is usually limited by their high viscosity, which reduces transport capabilities and slows down the chemical processes that occur in these solvents. Mixing of ionic liquids with molecular solvents such as organic carbonates or lactones can reduce viscosity of applied electrolyte. 12-15Among other aprotic solvents, γ-butyrolactone (GBL) is usually applied in new generation of LIBs and other electrochemical devices. Besides its low cost, GBL has wide liquidus range and better thermal stability comparing to alkyl carbonate solvents. 16 In our previous papers we demonstrated that binary mixture of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, (IM 14 TFSI), and GBL has around 20% higher specific conductivity at low IL mole fractions compared to IM 14 TFSI + propylene carbonate (PC) binary mixture.15,17 Xu et al. observed similar trend in the case of 1-ethyl-3-methylimidazolium dicyanamide (IM 12 DC...

Electrochemical Behaviour of Nb‐Doped Anatase TiO2 Microbeads in an Ionic Liquid Electrolyte

“…The four first CVs for the different Nb‐doping concentrations, and for the undoped reference material, are shown in Figure 2. The CV response in the 1 st cycle is similar for the all electrodes and are similar to previous results for anatase [16,18] . The insertion peak in the first cycle is located around −1.3 to −1.4 V (vs Ag/Ag + ) and can thus be related to the two‐phase intercalation region [19] .…”

“…However, an irreversible capacity loss when using common organic electrolytes limits the applicability of TiO 2 [16,17] . To mitigate this problem different electrolyte formulations have been proposed and a promising route is the use of ionic liquid (IL) based electrolytes [18,19] . It has been suggested that the presence of an IL stabilizes the surface of the active material and in this way reduces the irreversible capacity loss.…”

Electrochemical study of anatase TiO2 nanotube array electrode in electrolyte based on 1,3-diethylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid

“…As continuation of our scientific work [37,38], in this research study are examined the physicochemical and electrochemical properties of 0.5 mol•dm −3 LiTFSI ionic liquid 1,3diethylimidazolium bis(trifluoromethylsulfonyl)imide, C 2 C 2 imTFSI, as well as the performance of anatase Ti/TiO 2 nanotube array (NTA) cells-that electrode material enhances the capacity and energy density of the battery upon lithiumion (Li + ) intercalation and the ability of nanotubes to intercalate/deintercalate Li + large number of times [39]. In order to examine temperature effect on cell performances, cyclic voltammetry (CV) and galvanostatic charge/discharge experiments are performed in a wide temperature range 298.15 to 328.15 K. The electrochemical testing was conducted in order to compare the stability of selected electrolyte with previous one, which contains γ-butyrolactone, GBL, as cosolvent [37], where it is assumed that there is a possibility of stabilization effect between the carbonyl group of GBL and acidic C2-H from 1,3-dialkylimidazolium cation.…”

“…Figure 6 a shows that values of the overall capacity of anatase TiO 2 NTAs, which exceeds theoretical capacity, come from the large contribution of lithium surface storage capacity, which does not depend on bulk diffusion time. The relative contribution of surface storage capacity decreases with the temperature increase because of the increased diffusion coefficient of lithium-ion [37,38], but remains significant. The decrease in the difference between voltage plateaus in charge and discharge with the temperature increase shows the expected diminution of overall resistance of the cell at higher temperatures.…”

Physicochemical Investigations of a Binary Mixture Containing Ionic Liquid 1-Butyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide and Diethyl Carbonate

“…15 By reducing viscosity and altering other physicochemical properties, it was shown that this mixture could be applied as an electrolyte for Li-ion batteries. 21 Therefore, as a continuation of our previous studies toward the understanding and comprehension of the basic properties of (IL + molecular solvent) binary mixtures, the volumetric and transport properties of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid, [bmpyrr][NTf 2 ], with DEC were for the first time investigated in this work. Computational analysis based on both density functional theory (DFT) calculations and molecular dynamics (MD) simulations were performed to achieve an additional insight into the interactions between constituting components of a binary mixture, understanding better the interactions between IL and DEC.…”