Lithium Difluoro(oxalato)borate as Salt for Lithium-Ion Batteries

Chen, Zonghai; Liu, J.; Amine, Khalil

doi:10.1149/1.2409743

Cited by 76 publications

(64 citation statements)

References 14 publications

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“…This is possibly an advantage, since the properties of the anions at the electrode or current collector/ electrolyte interface is dependent on the type of functional group. 2,12,25 Hence, if necessary, hybrid lithium salts may offer a possibility to fine-tune the properties of electrode and/or aluminum current collector passivation films, without too much of a compromise in the anion stability or the lithium salt dissociation. Finally, in agreement with the phosphoryl imide CPI (P3), the most promising sulfonyl imide is the symmetrically cyano-substituted CSI (S3).…”

Section: Imide Substitution Effectsmentioning

confidence: 99%

“…Similarly, several fluoroalkylborates (e.g. BF 3 (C 2 F 5 ) ¹ , FAB) 24 and difluoro(oxalato)borate, BF 2 (C 2 O 4 ) 25,26 have been developed to remedy the disadvantages of BF 4 ¹ (moderate electrolyte conductivity) and BOB (poor salt solubility and highly resistive solid electrolyte interphases (SEI)), 27,28 respectively. In the spirit of the hybrid anions we here suggest several new linear anions, via a computational screening of TFSI, FSI and ten "look-alikes".…”

Section: Introductionmentioning

confidence: 99%

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Novel Lithium Imides; Effects of -F, -CF3, and -C≡N Substituents on Lithium Battery Salt Stability and Dissociation

et al. 2012

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New lithium imide salts have been studied using computational chemistry methods. Intrinsic anion oxidation potentials and ion pair dissociation energies are presented for six lithium sulfonyl imides (R-O 2 S-N-SO 2 -R) and six lithium phosphoryl imides (R 2 -OP-N-PO-R 2 ), as a function of -F, -CF 3 , and -C7N substitution. The modelled properties are used to estimate the electrochemical oxidation stability of the anions and the relative ease of charge carrier creation in lithium battery electrolytes. The results show that both properties are improved with cyanosubstitution, which in part is corroborated when comparing with other classes of lithium salts. However, the comparison also shows ambiguous oxidation stability results for cyano-substituted reference salts of the type PF x (CN) 6−x − and BF x (CN) 4−x − , using two different approaches -we present a tentative explanation for this. For the imide anions and PF 6 − , the bond dissociation energy is introduced as a third property, to gauge the thermal stability of the imide anions. The results suggest that the C-S and C-P bonds are the most liable to break and that the thermal stability is inversely related to the ion pair dissociation energy.

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Section: Imide Substitution Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Novel Lithium Imides; Effects of -F, -CF3, and -C≡N Substituents on Lithium Battery Salt Stability and Dissociation

et al. 2012

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“…that is significantly higher than that of 1 M LiPF 6 in this solvent mixture (0.33 vs. 0.24) [33,34] and the ability to form a very stable and protecting SEI [35,36] on graphite electrodes, just like LiBOB [29,30,37]. Beyond that, the SEI built in an LiDFOB-based electrolyte is also a very good lithium ion conductor, comparable with the SEIs of LiBF 4 -based electrolytes [29,30]. Furthermore, LiDFOB has higher solubility in organic carbonates than LiBOB [1.4 mol kg in EC-DEC (3:7, by wt.)]…”

Section: Introductionmentioning

confidence: 73%

“…As LiDFOB was recently checked as a possible new salt for secondary lithium metal batteries [27] the influence of this salt on the chemical stability of deposited lithium was investigated as well. Since this salt was first published by Zhang in 2006 [28] its characteristics have been extensively studied, mainly for possible applications in secondary lithium ion batteries [25,[29][30][31][32]. LiDFOB combines the advantages of lithium bis(oxalato)borate (LiBOB) and lithium tetrafluoroborate (LiBF 4 ) when used in electrolytes for lithium ion cells as LiDFOB comprises the same molecular moieties as LiBOB and LiBF 4 [28,29].…”

Section: Introductionmentioning

confidence: 99%

Results from a Novel Method for Corrosion Studies of Electroplated Lithium Metal Based on Measurements with an Impedance Scanning Electrochemical Quartz Crystal Microbalance

et al. 2013

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Abstract:A new approach to study the chemical stability of electrodeposited lithium on a copper metal substrate via measurements with a fast impedance scanning electrochemical quartz crystal microbalance is presented. The corrosion of electrochemically deposited lithium was compared in two different electrolytes, based on lithium difluoro(oxalato) borate (LiDFOB) and lithium hexafluorophosphate, both salts being dissolved in solvent blends of ethylene carbonate and diethyl carbonate. For a better understanding of the corrosion mechanisms, scanning electron microscopy images of electrodeposited lithium were also consulted. The results of the EQCM experiments were supported by AC impedance measurements and clearly showed two different corrosion mechanisms caused by the different salts and the formed SEIs. The observed mass decrease of the quartz sensor of the LiDFOB-based electrolyte is not smooth, but rather composed of a series of abrupt mass fluctuations in contrast to that of the lithium hexafluorophosphate-based electrolyte. After each slow decrease of mass a rather fast increase of mass is observed several times. The slow mass decrease can be attributed to a consolidation process of the SEI or to the partial dissolution of the SEI leaving finally lithium metal unprotected so that a fast film formation sets in entailing the observed fast mass increases.

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“…Lithium difluoro oxalate borate ͑LiDFOB͒ was reported as a promising salt 15,16 and a functional additive, which can also provide excellent protection for graphite negative electrodes 17,18 as LiBOB can, while limiting the initial interfacial impedance increase. A reasonable explanation is that the LiDFOB has only one oxalato ring, and the above cross-linking reaction does not occur during the formation of the artificial SEI layer.…”

Section: ͓1͔mentioning

confidence: 99%

Lithium Tetrafluoro Oxalato Phosphate as Electrolyte Additive for Lithium-Ion Cells

Qin

Chen

et al. 2010

Electrochem. Solid-State Lett.

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Lithium tetrafluoro oxalato phosphate ͑LTFOP͒ was investigated as an electrolyte additive to improve the life of mesocarbon microbead ͑MCMB͒/Li 1.1 ͓Ni 1/3 Co 1/3 Mn 1/3 ͔ 0.9 O 2 ͑NCM͒ cells for high power applications. With the addition of 1-3 wt % LTFOP to MCMB/NCM cells, the capacity retention after 200 cycles at 55°C significantly improved. Electrochemical impedance spectroscopy showed that the LTFOP addition in the electrolyte increased the initial impedance but lowered the impedance growth rate during cycling. Aging tests at 55°C indicated that the capacity retention of the negative electrode significantly benefited as a result of the LTFOP addition. Differential scanning calorimetry showed that the safety of the lithiated MCMB is significantly improved with the LTFOP addition. Lithium-ion batteries are being developed as the power source for hybrid and plug-in hybrid electric vehicles, 1-4 which generally require a battery with 15 years of life, improved safety, and low cost. This requirement is a significant challenge for the current technology of lithium-ion batteries, and a great deal of effort has been devoted to extend their calendar and cycle life. A promising approach is to develop functional electrolyte additives that limit the degradation of electrode materials during cycling by stabilizing the electrode/electrolyte interface. The state-of-the-art nonaqueous electrolyte for lithium-ion batteries is LiPF 6 dissolved in carbonates; however, LiPF 6 is sensitive to a trace amount of moisture, which can trigger the decomposition of LiPF 6 to produce PF 5 , LiF, POF 3 , and HF.5 HF, in turn, attacks the cathode materials to release metal ions. Amine et al. 1 reported that a trace amount of reaction by-products, such as HF, LiF, POF 3 , and Mn 2+ , can attack the electrodes ͑in particular, the negative electrode͒ and dramatically shorten the life of the battery. To overcome this problem, researchers have developed several passivation additives that can polymerize and form a stable passivation film at the electrode surface during the formation cycles. Examples of these additives are vinyl ethylene carbonate, [6][7][8] vinylene carbonate, 7,9-11 lithium bis͑oxalato͒borate ͑LiBOB͒, 12,13 and vinyl pyridine.14 It has been reported that the bis͑oxalato͒borate anion ͑BOB − ͒ of LiBOB can be reduced at 1.7 V vs Li + /Li and form an artificial and stable solid electrolyte interface ͑SEI͒ layer that can improve the capacity retention of graphite negative electrodes. 12,13 Although not yet confirmed, BOB − is believed to be first reduced at 1.7 V vs Li + /Li, after which an oxalato ring forms ͓1͔The free end of the opened oxalato group would then attack another BOB − to initiate a polymerization reaction and form a protective film on the surface of the graphite. Equation 1 also shows that the other oxalato ring of BOB − can be electrochemically activated and trigger a cross-linking reaction between different BOB-based polymer chains. This cross-linking reaction can then lead to the significant growth of the SEI ...

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Lithium Difluoro(oxalato)borate as Salt for Lithium-Ion Batteries

Cited by 76 publications

References 14 publications

Novel Lithium Imides; Effects of -F, -CF3, and -C≡N Substituents on Lithium Battery Salt Stability and Dissociation

Novel Lithium Imides; Effects of -F, -CF3, and -C≡N Substituents on Lithium Battery Salt Stability and Dissociation

Results from a Novel Method for Corrosion Studies of Electroplated Lithium Metal Based on Measurements with an Impedance Scanning Electrochemical Quartz Crystal Microbalance

Lithium Tetrafluoro Oxalato Phosphate as Electrolyte Additive for Lithium-Ion Cells

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