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1.
The cycling efficiencies and cycling performance of a lithium metal anode in a vinylene carbonate (VC)-containing electrolyte were evaluated using Li/Ni and LiCoO2/Li coin type cells. The cycling efficiencies of deposited lithium on a nickel substrate in an EC + DMC (1:1) electrolyte containing LiPF6, LiBF4, LiN(SO2CF3)2 (LiTFSI), or LiN(SO2C2F5) (LiBETI) at 25 and 50 °C were improved by presence of VC. However, the lithium cycling efficiencies at low temperature (0 °C) decreased by adding VC to the EC+DMC (1:1) electrolyte. The deposited lithium at low temperature exhibited a dendritic morphology and a thicker surface film. The lithium ion conductivity of the VC derived surface film was lower than that of the VC-free surface film at low temperature. Therefore, we concluded that the cycling efficiency decreased with decreasing temperature. On the other hand, the cell containing VC additive has excellent performance at elevated temperature. The deposited lithium at 50 °C in the VC-containing electrolyte exhibited a particulate morphology and formed a thinner surface film. The VC derived surface film, which consists of polymeric species, suppressed the deleterious reaction between the deposited lithium and the electrolyte.  相似文献   

2.
FTIR spectroscopic investigations coupled with ionic conductivity and viscosity measurements on lithium imide (LiN(CF3SO2)2)-propylene carbonate (PC)-poly(methyl methacrylate) (PMMA) based liquid and gel electrolytes over a wide range of salt (0.025-3 M) and polymer (5-25 wt.%) concentration range furnish a novel insight into the ion-ion and ion-solvent-polymer interactions. Vibrational spectral data for LiN(CF3SO2)2-PC electrolytes reveal that the solvation of lithium ions manifests from Li+OC and Li+O (ring oxygens) interactions as the νs(CO), the ring breathing and the δ(CH) modes of the pentagonal solvent ring are strongly perturbed for all salt concentrations. The split of the ν(SO2) mode (that appears at 1355 cm−1 for the “free imide ion”) into two components at 1337 and 1359 cm−1 confirms the existence of contact ion-pairs possessing two different stable optimized geometries wherein the Li+ ion coordinates in a bidentate fashion in liquid and gel electrolytes of 3 M LiN(CF3SO2)2-PC strength. Perturbations observed for the νa(SNS) and νs(SNS) modes of the imide ion and the symmetric ring deformation mode of PC confirms the presence of ion-pairs in both 2 and 3 M electrolytes. Incorporation of even upto 25 wt.% of PMMA in a solution of LiN(CF3SO2)2-PC of 3 M strength results in an insignificant conductivity decline (as σ25>10−3 S cm−1) which is simultaneously accompanied by a massive increase in its macroscopic viscosity (as η25>108 cSt). Gels containing 25 wt.% of PMMA exhibit a complex pattern of Li+-PMMA interactions through the carbonyl oxygen of its ester group which is evidenced from the perturbations observed for the νs(CO) mode of PMMA. Ionic conductivity decline that occurs at salt concentrations ≥1.25 M LiN(CF3SO2)2-PC in both liquid and gel electrolytes, is therefore attributable to (i) ion-pairing phenomenon and (ii) an enhancement in the solution viscosity due to a high salt proportion.  相似文献   

3.
Electrochemical properties of graphite electrode are studied in propylene carbonate (PC) electrolytes containing both LiN(SO2CF3)2 and Ca(N(SO2CF3)2)2 salts, and the influence of the salt concentrations on the intercalation/de-intercalation properties of graphite electrode is clarified. In the higher concentration electrolytes, reversible lithium-ion intercalation/de-intercalation at graphite electrode takes place. In contrast, only the exfoliation of graphite occurs in the lower concentration electrolytes. The effect of the salt concentrations on the electrochemical properties of graphite is discussed.  相似文献   

4.
Gel type electrolyte was formulated by blending of PEDGA and PAN. PEDGA is a UV curable polymer which forms a chemical crosslink by UV or heat. Gel type electrolyte is very stable in ionic conductivity and interfacial resistance for a long storage time. It has the advantage of manufacturing the battery in a continuous process because oligomer crosslinking occurs in few seconds without heating. Discharge capacity and cycle life were increased by using LiPF6/LiCF3SO3 mixed lithium salt and adding inorganic filler such as TiO2.  相似文献   

5.
An electrochemical technique based on concentration cell e.m.f. measurements is used to determine the lithium transference number and diffusion coefficient in poly(ethylene oxide)-lithium salt complexes. Measurements were carried out at 90°C on PEO–LiI, PEO–LiClO4 and PEO–LiCF3SO3 electrolytes. According to the phase diagram of the PEO-lithium salt system these complexes are fully amorphous at 90°C. Accurate determination oft Li + by the e.m.f. concentration cell method generally requires knowledge of the mean salt activity coefficients. However, this becomes unnecessary when the two electrolyte concentrations differ only slightly. As a first step the mean salt activity coefficient was estimated using a galvanic cell of the lithium/PEO-LiX/MX n /M type withM n+=Ag+ or Pb2+, and X=I or CF3SO3 . The resulting lithium transference numbers are 0.34 for the PEO–LiI complex and 0.7 for PEO–LiCF3SO3. Discrepancies between thet Li + values can be explained by the formation of triplets in the PEO–LiCF3SO3 electrolyte. By recording concentration cell potential versus time and comparing with theoretical curves, the salt lithium diffusion coefficient was obtained.D LiI was found to be around 4×10–8 cm2 s–1 in PEO–LiI and 8×10–8 cm2 s–1 in PEO–LiCF3SO3 at 90°C. These results suggest a liquid-like behaviour for the microscopic transport mechanism.  相似文献   

6.
-Butyrolactone-ethylene carbonate (BL-EC) mixtures have been investigated as electrolytes for Li-ion batteries using LiPF6 and LiBF4 as lithium salt. The thermal stability of the electrolytes in a large range of temperatures (–90 °C to 40 °C) have been studied by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). From the results of these experiments, the phase diagram of the BL-EC system has been determined. It is characterised by a eutectic point at –56.3 °C and a molar fraction in EC: x EC = 0.1. A metastable compound has been demonstrated below –90 °C at x EC = 0.4. Conductivity measurements of BL-EC solutions, in the presence of LiPF6 and LiBF4, indicate that LiPF6 in the eutectic mixture is the most conducting electrolyte in the range of temperatures investigated (–30 °C to room temperature). Nevertheless, at low temperature, LiBF4 based electrolytes compete well with LiPF6, especially when the amount of EC in the mixture is as high as x EC = 0.5. Moreover, recrystallisation of the salt below –20 °C is avoided when LiBF4 is used as salt. A large increase in viscosity of the solvent mixture is observed when a salt is added, but the increase is lower for LiBF4 than LiPF6. When EC is added to BL at constant salt concentration (1 M), the conductivity of LiPF6 solutions decreases more rapidly than LiBF4 solutions. This has been attributed, at least partially, to the dissociating power of EC. The electrochemical windows of BL-EC (equimolar) mixtures in the presence of LiPF6 and LiBF4 are comparable but it is shown that the solvents oxidation rate at high potentials is lower when LiBF4 is used.  相似文献   

7.
A new gel-type polymer electrolyte (GPE) was made by the copolymerizing acrylonitrile (AN) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). The copolymer mixed with a plasticizer—propylene carbonate (PC) and lithium salt to form GPE. The lithium salts are LiCF3SO3, LiBr and LiClO4. FT-IR spectra show that the lithium ion in the LiClO4 system has the strongest interaction with the group based on the plasticized polymer. FT-IR spectra also indicate that CF3SO3 prefers producing anion-cation association. Moreover, the 13C solid state NMR spectra for the carbons attached to the PC of GPE exhibited different level of chemical shift (158.5 ppm) when the different lithium salts were added to the electrolyte. The results of differential scanning calorimeter (DSC) also indicate that the LiClO4 system has more free lithium ions; therefore, it has the maximum conductivity. In this study, the highest conductivity 2.98 × 10−3 S cm−1 exists in AG2/PC = 20/80 wt.% system which contain 3 mmole (g-polymer)−1 LiClO4. Additionally, the polymer electrolytes, which contain GMA-IDA have better interfacial resistance stability with lithium electrode.  相似文献   

8.
Composite polymer electrolytes (CPEs) based on poly (ethylene oxide) (PEO) (Mol.Wt ∼6×105) complexed with LiN(CF3SO2)2 lithium salt and SrBi4Ti4O15 ferroelectric ceramic filler have been prepared as films. Citrate gel technique and conventional solid state technique were employed for the synthesis of the ferroelectric fillers in order to study the effect of particle size of the filler on ionic conductivity of the polymer electrolyte. Characterization techniques such as X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and temperature dependant DC conductivity studies were taken for the prepared polymer composite electrolytes. The broadening of DTA endotherms on addition of ceramic fillers to the polymer salt complex indicated the reduction in crystallinity. An enhancement in conductivity was observed with the addition of SrBi4Ti4O15 as filler to the (PEO)8-LiN(CF3SO2)2 polymer salt complexes. Among the investigated samples (PEO)8-LiN(CF3SO2)2 +10 wt% SrBi4Ti4O15 (citrate gel) polymer composite exhibits a maximum conductivity.  相似文献   

9.
Organoboron-based anion trapping polymer electrolytes were synthesized through hydroboration or dehydrocoupling reaction between poly(propylene oxide) (PPO) oligomer (Mn = 400, 1200, 2000 and 4000) and 9-borabicyclo[3.3.1]nonane (9-BBN). Obtained oligomers were added various lithium salts (LiN(CF3SO2)2, LiSO3CF3, LiCO2CF3 or LiBr) to analyze the ionic conductivity and lithium ion transference number (tLi+). The ionic conductivity of the oligomer in the presence of LiN(CF3SO2)2 showed higher ionic conductivity than other systems, however, the tLi+ was less than 0.3. When LiSO3CF3 or LiCO2CF3, was added high tLi+ over 0.6 was obtained. Such difference in tLi+ can be explained by HSAB principle. Since boron is a hard acid, soft (CF3SO2)2N anion can not be trapped effectively. High ionic conductivity of 1.3 × 10−6 S cm−1 and high tLi+ of 0.73 was obtained when PPO chain length was 2000. These values of facilely prepared polymer electrolytes are comparable to those of the PPOs having covalently bonded salt moieties on the chain ends.  相似文献   

10.
Shanshan Wang 《Polymer》2010,51(13):2864-2871
Thermoplastic polyurethane (TPU) electrolytes with lithium salts were prepared by an in-situ polymerization method. Three different lithium salts were used to study the effects of the anion structure on the properties of polyurethane electrolytes: LiCl, LiClO4, LiN(SO2CF3)2 (LiTFSI). The effects of the anion structure on monomer (PTMG) prior to polymerization and on the properties of TPU electrolytes post polymerization were investigated. The anion structure of lithium salt has a significant influence on the ionic conductivity, thermal stability and tensile property of TPU electrolytes. The TPU electrolytes with LiTFSI demonstrated a high ionic conductivity up to 10−5 S/cm at 300 K. The ionic conductivity of polyurethane electrolytes with lithium salts is in the order: LiCl < LiClO4 < LiTFSI. It was found that the lithium salts with larger anions were easily dissociated in TPU and had stronger interaction with TPU, which provided more charge carriers and gave higher ionic conductivity.  相似文献   

11.
《Electrochimica acta》1987,32(2):299-305
Mixed solutions of dimethyl sulfoxide (DMSO) and low viscosity solvents have been examined as a solvent of the electrolyte for rechargeable lithium (Li) batteries. The electrolytic conductivities of LiClO4. LiBF4 and LiPF6 were measured as a function of the solvent composition. Maximum conductivities were observed in the DMSO concentration ranges of 60–80 mol% for LiClO4 and LiBF4, and 20–60 mol% for LiPF6. The highest conductivity of all examined systems was 1.6 × 10−2 S cm−1 in the solution containing 1,2-dimethoxyethane (DME) and LiPF6 as the co-solvent and the electrolyte, respectively. Polarization behavior and charge-discharge characteristics of the lithium electrode were investigated in the DMSO-based solutions. The cycling efficiency was markedly dependent not only on the co-solvent but also the Li salt. The highest efficiency on the nickel substrate was observed in LiPF6 (1 mol dm−3)/DMSO-DME (1:1 by volume). High rechargeability of Li was also expected in the solution containing LiClO4 or LiBF4 when aluminum was used as the substrate.  相似文献   

12.
Hexanoyl chitosan that exhibited solubility in tetrahydrofuran was prepared by acyl modification of chitosan. Films of hexanoyl chitosan‐based polymer electrolyte were prepared by the technique of solution casting. Ethylene carbonate, propylene carbonate, and diethyl carbonate with different dielectric constants were employed as the plasticizing solvents and lithium trifluoromethanesulfonate (LiCF3SO3) was used as the salt. The importance of dielectric constant affecting conductivity and transport properties of hexanoyl chitosan:LiCF3SO3 electrolytes have been examined in the present study. An enhancement in the ionic conductivity has been found on plasticization, and the magnitude of conductivity increment strongly depended on the dielectric constant of the plasticizer. Transport properties such as activation energy and charge carrier concentration have been calculated to obtain information that may be used to elucidate the mechanism of conductance. In addition to conductivity studies, thermal studies and transference number measurements were performed to correlate the phase structure and diffusion phenomena to the conductivity behavior of hexanoyl chitosan‐based polymer electrolyte. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101:4474–4479, 2006  相似文献   

13.
Morphological properties of composite polymer electrolytes based on blends of polyethylene oxide (PEO) and a perfluorinated polyphosphazene (PPz) containing LiPF6 as lithium salt and a finely divided ceramic filler, γ-LiAlO2, were studied by using polarizing optical microscopy and differential scanning calorimetry (DSC). A parallel study was performed on propylene carbonate plasticized composite polymer electrolytes. Results indicate that both the morphology and the thermal properties depend upon the composition of the polymer host, a result not observed in composite polymer electrolytes having the same polymer composition containing LiCF3SO3 as lithium salt. The incorporation of the ceramic filler at the lower concentration tested (10% by wt) has practically no effect on the thermal behavior of the samples; whereas, differences were clearly distinguished at a concentration of ceramic material of 20 wt %. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1023–1030, 1999  相似文献   

14.
The surface layer and elemental composition of a lithium‐metal electrode before and after in contact with nanocomposite polymer electrolytes (NCPEs) comprising poly(ethylene oxide)/Ca3(PO4)2/LiX (X = N(CF3SO2)2, ClO4) were analyzed by X‐ray photoelectron spectroscopy. The presence of Li2CO3/LiOH in the outer layer of the native film was identified. The formation of LiF was detected on lithium surface when in contact with NCPE containing LiN(CF3SO2)2 and is attributed to the reaction between the native film and impurities. Li/NCPE/Li symmetric cells were assembled, and the thickness of the solid electrolyte interface as a function of time was analyzed at 60°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

15.
The anodic polarization behavior of aluminum (Al) as a current collector of lithium (Li) ion battery has been investigated in organic electrolyte solutions containing different lithium salts. The Al current collector has suffered serious corrosion in the solution containing Li(CF3SO3)2N (LiTFSI) under an anodic polarization condition, whereas, it was anodically stable in the LiPF6 solution. In the solution of Li(C2F5SO2)2N (LiBETI), the Al anode showed an intermediate character between those in the LiPF6 and LiTFSI solutions. The corrosion behavior of the Al electrode was much influenced by its surface condition. The addition of LiPF6 in the imide-salts (LiTFSI and LiBETI) solutions suppressed the anodic corrosion of Al. The results of electrochemical quartz crystal microbalance (EQCM) experiments proved that the anodic processes on Al in the organic electrolytes consist of the formation of surface films and their dissolution. The X-ray photoelectron spectroscopy (XPS) analysis suggests that the anodic stability of the Al electrode in the imide-salts solutions containing LiPF6 is associated with the formation of a fluoride (AlF3)-rich film on the Al surface.  相似文献   

16.
The high flash point solvent adiponitrile (ADN) was investigated as co-solvent with ethylene carbonate (EC) for use as lithium-ion battery electrolyte. The flash point of this solvent mixture was more than 110 °C higher than that of conventional electrolyte solutions involving volatile linear carbonate components, such as diethyl carbonate (DEC) or dimethyl carbonate (DMC). The electrolyte based on EC:ADN (1:1 wt) with lithium tetrafluoroborate (LiBF4) displayed a conductivity of 2.6 mS cm−1 and no aluminum corrosion. In addition, it showed higher anodic stability on a Pt electrode than the standard electrolyte 1 M lithium hexafluorophosphate (LiPF6) in EC:DEC (3:7 wt). Graphite/Li half cells using this electrolyte showed excellent rate capability up to 5C and good cycling stability (more than 98% capacity retention after 50 cycles at 1C). Additionally, the electrolyte was investigated in NCM/Li half cells. The cells were able to reach a capacity of 104 mAh g−1 at 5C and capacity retention of more than 97% after 50 cycles. These results show that an electrolyte with a considerably increased flash point with respect to common electrolyte systems comprising linear carbonates, could be realized without any negative effects on the electrochemical performance in Li-half cells.  相似文献   

17.
Limiting current densities equivalent to the transport-controlling step of lithium ions in organic electrolytes were measured by using a rotating disk electrode (RDE). The diffusion coefficients of lithium ion in the electrolyte of PC/LiClO4, EC : DEC/LiPF6 and EC : DMC/LiPF6 were determined by the limiting current density data according to the Levich equation. The diffusion coefficients increased in the order of PC/LiClO4<EC : DEC/LiPF6<EC : DMC/ LiPF6 with respect to molar concentration of lithium salt. The maximum value of diffusivity was 1.39x10-5cm2/s for 1M LiPF6 in EC : DMC=1 : 1. Exchange current densities and transfer coefficients of each electrolyte were determined according to the Butler-Volmer equation.  相似文献   

18.
Polymer electrolytes of poly(ethylene oxide) matrix with lithium imide salt LiN(CF3SO2)2 were prepared by casting from solution. Thin films with compositions corresponding to molar ratios 6:1, 3:1 and 2:1 EO:Li were investigated by impedance spectroscopy, impedance spectroscopy simultaneous with polarizing microscope observation, X-ray diffraction and differential scanning calorimetry. The presence of PEO:LiTFSI stoichiometric complexes was found to significantly decrease conductivity at temperature of crystallization, which indicates that those complexes should be regarded as poorly conductive. Changes of properties of amorphous phase related to crystallization were also observed. Crystallization induced phase segregation, which in some cases caused considerable shift of the glass transition temperature of amorphous phase remaining in a semicrystalline system. For PEO:LiTFSI electrolyte with molar ratio of 3:1 EO:Li this effect was found to be responsible for enhancement of conductivity of semicrystalline sample in respect to the amorphous one, which was observed at low temperatures. Phase separation involving precipitation of LiTFSI salt was also found to be a likely explanation for significant enhancement of conductivity for PEO:LiTFSI 2:1 electrolyte subjected to rapid cooling below the glass transition temperature.  相似文献   

19.
Three types of transition metal oxide/carbon composites including Fe2O3/C, NiO/C and CuO/Cu2O/C synthesized via spray pyrolysis were used as anode for lithium ion battery application in conjunction with two types of ionic liquid: 1 M LiN(SO2CF3)2 (LiTFSI) in 1-ethyl-3-methyl-imidazolium bis(fluorosulfonlyl)imide (EMI-FSI) or 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (Py13-FSI). From the electrochemical measurements, the composite electrodes using Py13-FSI as electrolyte show much better electrochemical performance than those using EMI-FSI as electrolyte in terms of reversibility. The Fe2O3/C composite shows the highest specific capacity and the best capacity retention (425 mAh g−1) under a current density of 50 mA g−1 for up to 50 cycles, as compared with the NiO/C and CuO/Cu2O/C composites. The present research demonstrates that Py13-FSI could be used as an electrolyte for transition metal oxides in lithium-ion batteries.  相似文献   

20.
A survey of the electrochemical stability of electrostatic spray deposited thin film of LiMn2O4 was performed in LiClO4-EC-PC, LiBF4-EC-PC, and LiPF6-EC-PC solutions at 55 °C. The solution resistance, the surface film resistance, and the charge-transfer resistance were all found to depend on the electrolyte composition. Among the LiX-salts studied, the lowest charge transfer-resistance, and surface layer resistance were obtained in LiBF4-EC-PC solution. There is no major influence of the electrolyte solution compositions upon lithium ion transport in the LiMn2O4 bulk at 55 °C. The diffusion coefficient of lithium in the solid phase varied within 10−10-10−8 cm2 s−1 in the three solutions. In general, it seems that in LiBF4 solutions, the surface chemistry is the most stable in the three solutions examined, and hence the electrode impedance in LiBF4 solutions was the lowest. In LiPF6 solutions, HF seems to play an important role, and thus, the electrode impedance is relatively high due to the precipitation of surface LiF.  相似文献   

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