Effect of carbonates fluorination on the properties of LiTFSI-based electrolytes for Li-ion batteries (original) (raw)
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ChemSusChem, 2014
In this Full Paper we show that the use of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as conducting salt in commercial lithium-ion batteries is made possible by introducing fluorinated linear carbonates as electrolyte (co)solvents. Electrolyte compositions based on LiTFSI and fluorinated carbonates were characterized regarding their ionic conductivity and electrochemical stability towards oxidation and with respect to their ability to form a protective film of aluminum fluoride on the aluminum surface. Moreover, the investigation of the electrochemical performance of standard lithium-ion anodes (graphite) and cathodes (Li[Ni1/3 Mn1/3 Co1/3 ]O2 , NMC) in half-cell configuration showed stable cycle life and good rate capability. Finally, an NMC/graphite full-cell confirmed the suitability of such electrolyte compositions for practical lithium-ion cells, thus enabling the complete replacement of LiPF6 and allowing the realization of substantially safer lithium-ion batteries.
The Journal of Physical Chemistry C, 2015
Herein, we present an extensive physico-chemical characterization of a series of fluorinated and non-fluorinated carbamates and their application as electrolyte solvents comprising lithium trifluoromethanesulfonyl imide (LiTFSI) as conducting salt. In a second step, these electrolyte compositions were characterized with respect to their ionic conductivity, salt dissociation, and electrochemical stability towards oxidation. In a third step, selected fluorinated electrolytes were studied concerning their ability to enable the utilization of LiTFSI as conducting salt in presence of an aluminum current collector by forming a protective aluminum fluoride surface layer, thus preventing the continuous anodic aluminum dissolution, i.e., aluminum corrosion. Finally, their electrochemical performance in combination with a state-of-the-art lithium-ion cathode material, Li(Ni 1/3 Mn 1/3 Co 1/3)O 2 (NMC), was investigated. It is shown that higher fluorinated carbamates reveal a very stable cycling performance of such cathodes due to their ability to form a sufficiently thick, i.e., protective aluminum fluoride layer on the surface of the aluminum current collector. These findings confirm their suitability as electrolyte solvents in combination with LiTFSI as conducting salt, enabling the successful replacement of toxic and unstable LiPF 6 for the development of intrinsically safer lithium-ion batteries.
Concentrated electrolytes based on dual salts of LiFSI and LiODFB for lithium-metal battery
Electrochimica Acta, 2018
Li-metal battery (LiMB) has received considerable attention as an alternative energy storage device to Li-ion battery in recent years. However, uncontrolled Li dendrite growth prevents the practical applications of LiMB. Herein, we report the use of concentrated electrolytes based on dual salts of lithium bis(fluorosulfonyl) imide (LiFSI) and lithium difluoro(oxalato) borate (LiODFB) to suppress Li dendrite growth. The compatibility of electrolyte and LiFePO 4 cathode was further verified by the long capacity retention and high rate performance of Li/LiFePO 4 battery. The superior electrochemical performance was attributed to the concentrated electrolyte, which could simultaneously suppress Li dendrite growth at the anode side and Aluminum (Al) current collector corrosion at the cathode side. This work provides new insights to develop high-performance LiMBs by carefully tailoring the multivariate composition of concentrated electrolyte.
ACS Applied Materials & Interfaces, 2019
Currently, concentrated electrolyte solutions are attracting special attention because of their unique characteristics such as unusually improved oxidative stability on both the cathode and anode side, the absence of free solvent, the presence of more anion content and the improved availability of Li + ions. Most of the concentrated electrolytes reported are lithium bis(fluorosulfonyl)imide (LiFSI) salt with ether-based solvents due to the high solubility of salts in ether-based solvents. However, their poor anti-oxidation capability hindered their application especially with high potential cathode materials (> 4.0 V). In addition, the salt is very costly, so it is not feasible from cost analysis point of view. Therefore, here we report a locally concentrated electrolyte, 2M LiPF 6 in ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 v/v ratio) diluted with fluoroethylene carbonate (FEC) which is stable within wide potential range (2.5-4.5 V). It shows significant improvement in cycling stability of lithium with an average coulombic efficiency (ACE) of ~98% and small voltage hysteresis (~30 mV) with current density of 0.2 mA/cm 2 for over 1066 hr in Li‖Cu cell. Furthermore, we ascertained the compatibility of the electrolyte for anode free Li-metal battery (AFLMB) using Cu‖LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC, ~2 mAh/cm 2) with a current density of 0.2 mA/cm 2. It shows stable cyclic performance with ACE of 97.8% and 40% retention capacity at 50 th cycle, which is the best result reported for carbonate based solvents with AFLMB. Whereas, the commercial carbonate based electrolyte have < 90% ACE and even cannot proceed more than 15 cycles with retention capacity > 40%. The enhanced cycle life and well retained in capacity of the locally concentrated electrolyte is mainly because of the synergetic effect of FEC as the diluent to increase the ionic conductivity and form stable anion-derived SEI. The locally concentrated electrolyte also shows high robustness to the effect of upper limit cutoff voltage.
Electrochimica Acta, 2013
Electrolyte solutions, containing the lithium salts lithium-cyclo-difluoromethane-1,1-bis(sulfonyl)imide (abbreviated as LiDMSI) and lithium-cyclo-hexafluoropropane-1,1-bis(sulfonyl)imide (LiHPSI) dissolved in organic carbonate solvents, were electrochemically investigated on graphite and LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) electrodes and compared to the electrolyte salt LiPF 6 with regard to conductivity, the electrochemical stability window, the anodic dissolution behavior vs. aluminum as well as the thermal stability behavior at 60 • C. XPS studies were carried out to investigate the influence of the salt on the composition and the thickness of the solid electrolyte interphase (SEI). Constant current cycling experiments proved the potential applicability of the investigated salts for lithium ion batteries.
IOP Conference Series: Materials Science and Engineering, 2018
The ionic conductivities of two different electrolytes, namely lithium hexafluorophosphate (LiPF6) and lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), in carbonate-based solvents have been investigated. The ionic conductivity of LiTFSI electrolyte is slightly larger than the LiPF6 electrolyte, namely 2.7 mS/cm vs. 2.4 mS/cm. The results of cyclic voltammetry and electrochemical impedance spectroscopy measurements show that LiTFSI electrolyte exhibit a better reversible redox reaction. Therefore, in this work, the full-cell battery using LiTFSI electrolyte exhibited higher specific capacity than the battery cell using LiPF6 electrolyte, namely 83.1 mAh/g and 101.5 mAh/g for the LiPF6 and LiTFSI electrolytes, respectively. Higher capacity in LiTFSI battery is thus related to better ionic conductivity and reversible redox reaction of LiTFSI electrolyte.
Nucleation and Atmospheric Aerosols, 2022
Lithium bis(trifluoromethanesulfonyl)imide [LiTFSI, LiN(CF3SO2)2] can be used as an alternative electrolyte salt in Li-ion battery to replace LiPF6 because it has good tolerance to moisture and is thermally stable. However, LiTFSI can cause corrosion to current collectors in Li-ion batteries. To suppress the corrosion rate, mixing LiTFSI with LiBOB salt [lithium bis(oxalato)borate, LiB(C2O4)2] has been recommended. This study aims to determine the effect of different LiBOB salt on Li-ion battery performance. In this study, three types of LiBOB are used: i.e., commercial LiBOB (PA), LiBOB2 synthesized with lithium source from LiOH (PA), and LiBOB5 synthesized by substitution of lithium source using Li2CO3 and brine water (technical grade). Based on the cyclic voltammetry (CV) test results, the current value in the sample mixed with LiBOB is lower than that without LiBOB. The decrease occurs from about 1 mA in the LiTFSI to 0.5 mA, and 0.1 mA in the LiTFSI-LiBOB2 (Mix 2), LiTFSI-LiBOB5 (Mix 3), and commercial LiTFSI-LiBOB (Mix 1), respectively. This result shows that LiBOB addition as co-salt in the LiTFSI electrolyte reduces Cu corrosion. In contrast to the CV results, the results of the charge-discharge (CD) test show that Mix 1 produces the lowest capacity (about 70 mAH/g), while the highest capacity value is produced by Mix 3 (about 104 mAH/g). Based on the results of the electrochemical impedance spectroscopy (EIS), the highest conductivity is produced by Mix 2 (0.0674 mS/cm), while Mix 1 produces the lowest (0.0388 mS/cm).