A new functionalized ionic liquid (IL) based on cyclic quaternary ammonium cations with ester group and bis(trifluoromethanesulfonyl)imide ([TFSI]?) anion, namely, N-methyl-N-methoxycarbonylpiperidinium bis(trifluoromethanesulfonyl)imide ([MMOCPip][TFSI]), was synthesized and characterized. Physical and electrochemical properties, including Li-ion transference number, ionic conductivity, and electrochemical stability, were investigated. The electrochemical window of [MMOCPip][TFSI] was 6 V, which was wide enough to be used as a common electrolyte material. The Li-ion transference number of this IL electrolyte containing 0.1 M LiTFSI was 0.56. The half-cell tests indicated that the [MMOCPip][TFSI] obviously improved the cyclability of a Li/LiFePO4 cell. For the Li/LiFePO4 half-cells, after 20 cycles at room temperature at 0.1 C, the discharge capacity was 109.7 mAh g?1 with 98.7% capacity retention in the [MMOCPip][TFSI]/0.1 M LiTFSI electrolyte. The good electrochemical performance demonstrated that the [MMOCPip][TFSI] could be used as electrolyte for lithium-ion batteries. 相似文献
The ionic liquid polymer electrolyte (IL-PE) membrane is prepared by ultraviolet (UV) cross-linking technology with polyurethane acrylate (PUA), methyl methacrylate (MMA), ionic liquid (Py13TFSI), lithium salt (LiTFSI), ethylene glycol dimethacrylate (EGDMA), and benzoyl peroxide (BPO). N-methyl-N-propyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py13TFSI) ionic liquid is synthesized by mixing N-methyl-N-propyl pyrrolidinium bromide (Py13Br) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The addition of Py13TFSI to polymer electrolyte membranes leads to network structures by the chain cross-linking. The resultant electrolyte membranes display the room temperature ionic conductivity of 1.37 × 10?3 S cm?1 and the lithium ions transference number of 0.22. The electrochemical stability window of IL-PE is about 4.8 V (vs. Li+/Li), indicating sufficient electrochemical stability. The interfacial resistances between the IL-PE and the electrodes have the less change after 10 cycles than before 10 cycles. IL-PE has better compatibility with the LiFePO4 electrode and the Li electrode after 10 cycles. The first discharge performance of Li/IL-PE/LiFePO4 half-cell shows a capacity of 151.9 mAh g?1 and coulombic efficiency of 87.9%. The discharge capacity is 131.9 mAh g?1 with 95.5% coulombic efficiency after 80 cycles. Therefore, the battery using the IL-PE exhibits a good cycle and rate performance. 相似文献
Vinyl ethylene carbonate (VEC) is investigated as an electrolyte additive to improve the electrochemical performance of LiNi0.4Mn0.4Co0.2O2/graphite lithium-ion battery at higher voltage operation (3.0–4.5 V) than the conventional voltage (3.0–4.25 V). In the voltage range of 3.0–4.5 V, it is shown that the performances of the cells with VEC-containing electrolyte are greatly improved than the cells without additive. With 2.0 wt.% VEC addition in the electrolyte, the capacity retention of the cell is increased from 62.5 to 74.5 % after 300 cycles. The effects of VEC on the cell performance are investigated by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), x-ray powder diffraction (XRD), energy dispersive x-ray spectrometry (EDS), scanning electron microscopy (SEM), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR). The results show that the films electrochemically formed on both anode and cathode, derived from the in situ decomposition of VEC at the initial charge–discharge cycles, are the main reasons for the improved cell performance. 相似文献
Ionic liquids are promising additives for Li-ion batteries owing to its desirable physicochemical properties. Triethylbutylammonium bis(trifluoromethanesulphonyl)imide ([N2224][Tf2N]) ionic liquid was synthesized and their physical and electrochemical properties were investigated. Among several quaternary ammonium ionic liquids, [N2224][Tf2N] exhibited higher conductivity (1.31 mS?cm?1), better thermal and electrochemical stabilities, and wide electrochemical window, i.e., more than 5.9 V. Standard solution was prepared by dissolving lithium bis(trifluoromethanesulphonyl)imide (LiTf2N) in ethylene carbonates/dimethyl carbonate (1:1, by weight). The conductivity for the electrolyte containing [N2224][Tf2N] and the mixed electrolyte without additives at 25 °C are 10.24 and 8.79 mS?cm?1, respectively. LiFePO4 half-cell containing 0.6 mol?L?1 LiTf2N-based organic electrolyte with [N2224][Tf2N] showed relatively high initial discharge capacity and coulombic efficiency at first cycle. It is found that the mix [N2224][Tf2N] electrolyte exhibits relatively high-rate capacity. The capacity retention of half-cell containing [N2224][Tf2N] is 2 % more than without additive at 0.2 C. However, the rate capacity retention of the half-cell with mix [N2224][Tf2N] electrolyte is above 10 % more than without additive at 0.5 C. The results showed that [N2224][Tf2N] was an effective electrolyte additive in LiFePO4 half-cell. 相似文献
Organic electrolyte is widely used for lithium-ion rechargeable batteries but might cause flammable fumes or fire due to improper use such as overcharge or short circuit. That weakness encourages the development of tools and materials which are cheap and environmental friendly for rechargeable lithium-ion batteries with aqueous electrolyte. Lithium iron phosphate (LiFePO4) with olivine structure is a potential candidate to be used as the cathode in aqueous electrolyte lithium-ion battery. However, LiFePO4 has a low electronic conductivity compared to other cathodes. Conductive coating of LiFePO4 was applied to improve the conductivity using sucrose as carbon source by heating to 600 °C for 3 h on an Argon atmosphere. The carbon-coated LiFePO4 (LiFePO4/C) was successfully prepared with three variations of the weight percentage of carbon. From the cyclic voltammetry, the addition of carbon coatings could improve the stability of cell battery in aqueous electrolyte. The result of galvanostatic charge/discharge shows that 9 % carbon exhibits the best result with the first specific discharge capacity of 13.3 mAh g?1 and capacity fading by 2.2 % after 100 cycles. Although carbon coating enhances the conductivity of LiFePO4, excessive addition of carbon could degrade the capacity of LiFePO4. 相似文献
In order to overcome the severe capacity decay of LiMn2O4 at high temperature, TiN is used as an active materials additive in this paper. The XRD and XPS test results indicate that the TiN can effectively prevent Mn from dissolving in electrolyte; galvanostatic charge-discharge test shows that LiMn2O4 electrode with TiN exhibits remarkably improved capacity retention at high temperature with capacity of 105.1 mAh g?1 at 1 C in the first cycle at 55 °C and the capacity maintains 88.9% retention after 150 cycles. And the electrochemical impedance spectroscopy result demonstrates TiN’s effectiveness in easing the increase of charge-transfer resistance during cycling. Therefore, we can conclude that TiN, as an addictive, made obvious contribution to the greatly improved electrochemical cycling performance of LiMn2O4. 相似文献
Fluoroethylene carbonate (FEC) is investigated as the electrolyte additive to improve the electrochemical performance of high voltage LiNi0.6Co0.2Mn0.2O2 cathode material. Compared to LiNi0.6Co0.2Mn0.2O2/Li cells in blank electrolyte, the capacity retention of the cells with 5 wt% FEC in electrolytes after 80 times charge-discharge cycle between 3.0 and 4.5 V significantly improve from 82.0 to 89.7%. Besides, the capacity of LiNi0.6Co0.2Mn0.2O2/Li only obtains 12.6 mAh g?1 at 5 C in base electrolyte, while the 5 wt% FEC in electrolyte can reach a high capacity of 71.3 mAh g?1 at the same rate. The oxidative stability of the electrolyte with 5 wt% FEC is evaluated by linear sweep voltammetry and potentiostatic data. The LSV results show that the oxidation potential of the electrolytes with FEC is higher than 4.5 V vs. Li/Li+, while the oxidation peaks begin to appear near 4.3 V in the electrolyte without FEC. In addition, the effect of FEC on surface of LiNi0.6Co0.2Mn0.2O2 is elucidated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The analysis result indicates that FEC facilitates the formation of a more stable surface film on the LiNi0.6Co0.2Mn0.2O2 cathode. The electrochemical impedance spectroscopy (EIS) result evidences that the stable surface film could improve cathode electrolyte interfacial resistance. These results demonstrate that the FEC can apply as an additive for 4.5 V high voltage electrolyte system in LiNi0.6Co0.2Mn0.2O2/Li cells. 相似文献
Li-ion battery cathode material lithium-vanadium-phosphate Li3V2(PO4)3 was synthesized by a carbon-thermal reduction method, using stearic acid, LiH2PO4, and V2O5 as raw materials. And stearic acid acted as reductant, carbon source, and surface active agent. The effect of its content on the crystal structure and electrochemical performance of Li3V2(PO4)3/C were characterized by XRD and electrochemical performance testing, respectively. The results showed that the content of carbon source has no significant effect on the crystal structure of lithium vanadium phosphate. Lihtium vanadium phosphate obtained with 12.3% stearic acid demonstrated the best electrochemical properties with a typical discharge capacity of 119.4 mAh/g at 0.1 C and capacity retention behavior of 98.5% after 50 cycles. And it has high reversible discharge capacity of 83 mAh/g at 5 C with the voltage window of 3 to 4.3 V. 相似文献
Electrodeposition of aluminum from ionic liquids has been considered a promising approach to low-temperature aluminum electrolysis. In this study, we first investigated the electrochemical stability of 1-ethyl-3-methylimidazolium chloride ([Emim][Al2Cl7]) electrolyte, which is a typically used electrolyte for aluminum electrodeposition. It was found that part of imidazole ions decomposed on the cathode during the electrolysis process, especially when the temperature was at or over 353 K. In order to enhance the stability of the electrolyte, we further studied the effects of lithium salt and lithium bis(oxalato)borate (LiBOB), on the electrochemical stability of the [Emim][Al2Cl7] ionic liquid system. It was found that the electrochemical window of the electrolyte was broadened from 2.59 to 2.74 V at 373 K by addition of 1 mol% LiBOB. With the existence of LiBOB, the reduction current density of Al2Cl7- increased before ?0.58 V and the electrodissolution of Al was more complete. The possible mechanism on the LiBOB increases the stability of the electrolyte systems also discussed based on our theoretical calculations. 相似文献
Although LiFePO4/C has been successfully put into practical use in lithium-ion batteries equipped on new energy vehicles, its unsatisfactory low temperature results in poor low performance of lithium-ion batteries, leading to a much smaller continue voyage course at extreme environments with low temperature for electric vehicles. In this paper, the electrochemical performance of the LiFePO4/C prepared by polyol route was investigated at a temperature range from 25 to ?20 °C. Compared to commercial ones, as-prepared LiFePO4/C shows a much better low-temperature performance with a reversible capacity of 30 mA h g?1 even at 5 C under ?20 °C and a capacity retention of 91.1 % after 100 cycles at 0.1 C under 0 °C. Moreover, high-resolution transmission electron microscopy (HRTEM) revealed that this outstanding performance at low temperatures could be assigned to uniform carbon coating and the nano-sized particles with a highly crystalline structure. 相似文献
High molecular weight polymer poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP), ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI), and salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based free-standing and conducting ionic liquid-based gel polymer electrolytes (ILGPE) have been prepared by solution cast method. Thermal, electrical, and electrochemical properties of 80 wt% IL containing gel polymer electrolyte (GPE) are investigated by thermogravimetric (TGA), impedance spectroscopy, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). The 80 wt% IL containing GPE shows good thermal stability (~?200 °C), ionic conductivity (6.42?×?10?4 S cm?1), lithium ion conductivity (1.40?×?10?4 S cm?1 at 30 °C), and wide electrochemical stability window (~?4.10 V versus Li/Li+ at 30 °C). Furthermore, the surface of LiFePO4 cathode material was modified by graphene oxide, with smooth and uniform coating layer, as confirmed by scanning electron microscopy (SEM), and with element content, as confirmed by energy dispersive X-ray (EDX) spectrum. The graphene oxide-coated LiFePO4 cathode shows improved electrochemical performance with a good charge-discharge capacity and cyclic stability up to 50 cycles at 1C rate, as compared with the without coated LiFePO4. At 30 °C, the discharge capacity reaches a maximum value of 104.50 and 95.0 mAh g?1 for graphene oxide-coated LiFePO4 and without coated LiFePO4 at 1C rate respectively. These results indicated improved electrochemical performance of pristine LiFePO4 cathode after coating with graphene oxide. 相似文献
A new series of nanocomposite polymer electrolyte (NCPE) system comprising of polyethylene oxide (PEO) and polypropylene glycol (PPG) as blended polymer host, zinc trifluoromethanesulfonate [Zn(CF3SO3)2] as dopant salt and nanocrystalline alumina [Al2O3] as filler was prepared by solution casting technique. The present system consisting of five different compositions of 87.5 wt% (PEO:PPG)–12.5 wt% Zn(CF3SO3)2 + x wt% Al2O3 [where x = 1, 3, 5, 7 and 9, respectively] has been thoroughly characterized by various analytical techniques such as electrical impedance spectroscopy, X-ray diffraction (XRD) studies, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) analysis and linear sweep voltammetry (LSV). The maximum room temperature ionic conductivity exhibited by the NCPE was found to be 2.1 × 10?4 S cm?1 for 3 wt% loading of Al2O3 which is an order higher than that of the optimized filler-free zinc salt doped polymer electrolyte system at 298 K. The evidence of a decrease in the degree of crystallinity responsible for the enhanced conductivity was revealed by the XRD data and further confirmed by DSC and SEM results. Moreover, the electrochemical stability window of the highly conducting electrolyte matrix has been experimentally determined by linear sweep voltammetry and found to be 3.6 V which is fairly adequate for the construction of zinc primary batteries as well as zinc-based rechargeable batteries at ambient conditions. 相似文献
The olivine-type LiFe1-xYxPO4/C (x?=?0, 0.01, 0.02, 0.03, 0.04, 0.05) products were prepared through liquid-phase precipitation reaction combined with the high-temperature solid-state method. The structure, morphology, and electrochemical performance of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive spectroscopy (EDS), galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). We found that the small amount of Y3+ ion-doped can keep the microstructure of LiFePO4, modify the particle morphology, decrease charge transfer resistance, and enhance exchange current density, thus enhance the electrochemical performance of the LiFePO4/C. However, the large doping content of Y3+ ion cannot be completely doped into LiFePO4 lattice, but existing partly in the form of YPO4. The electrochemical performance of LiFePO4/C was restricted owing to YPO4. Among all the doped samples, LiFe0.98Y0.02PO4/C showed the best electrochemical performance. The LiFe0.98Y0.02PO4/C sample exhibited the initial discharge capacity of 166.7, 155.8, 148.2, 139.8, and 121.1 mAh g?1 at a rate of 0.2, 0.5, 1, 2, and 5 C, respectively. And, the discharge capacity of the material was 119.6 mAh g?1 after 100 cycles at 5 C rates. 相似文献
Proton-conducting polymer electrolytes based on biopolymer, agar-agar as the polymer host, ammonium bromide (NH4Br) as the salt and ethylene carbonate (EC) as the plasticizer have been prepared by solution casting technique with dimethylformamide as solvent. Addition of NH4Br and EC with the biopolymer resulted in an increase in the ionic conductivity of polymer electrolyte. EC was added to increase the degree of salt dissociation and also ionic mobility. The highest ionic conductivity achieved at room temperature was for 50 wt% agar/50 wt% NH4Br/0.3% EC with the conductivity 3.73?×?10?4 S cm?1. The conductivity of the polymer electrolyte increases with the increase in amount of plasticizer. The frequency-dependent conductivity, dielectric permittivity (ε′) and modulus (M′) studies were carried out. 相似文献
Solid polymer electrolytes based on potato starch (PS) and graphene oxide (GO) have been developed in this study. Blending GO with PS has improved the ionic conductivity and mechanical properties of the electrolytes. In this work, series of polymer blend consisting of PS and GO as co-host polymer were prepared using solution cast method. The most amorphous PS-GO blend was obtained using 80 wt% of PS and 20 wt% of GO as recorded by X-ray diffraction (XRD). Incorporation of 40 wt% lithium trifluoromethanesulfonate (LiCF3SO3) into the PS-GO blend increases the conductivity to (1.48 ± 0.35) × 10?5 S cm?1. Further enhancement of conductivity was made using 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]). The highest conductivity at room temperature is obtained for the electrolyte containing 30 wt% of [Bmim][Cl] with conductivity value of (4.8?0 ± 0.69) × 10?4 S cm?1. Analysis of the Fourier transform infrared spectroscopy (FTIR) spectra confirmed the interaction between LiCF3SO3, [Bmim][Cl], and PS-GO blend. The variation of the dielectric constant and modulus studies versus frequency indicates that system of PS-GO-LiCF3SO3-[Bmim][Cl] obeys non-Debye behavior. 相似文献
A novel approach has been made to tailor Niobium pentoxide (Nb2O5) as a coating material on the surface of lithium iron phosphate (LiFePO4) via a facile polyol technique. The coating content was optimized at 1 wt%. The superficial coating demonstrated superior discharge capacity than the pristine LiFePO4. However, increasing the coating content further would result in a capacity loss. This may be due to the electrochemical inactiveness that increases with the content of the coating material, and 1 wt% of Nb2O5-coated LiFePO4 sample exhibits initial discharge capacity of 163 mAh g?1 at a current of 0.1 C and retains a stable discharge capacity of 143 mAh g?1 up to 400 cycles at 1 C rate with a coulombic efficiency of 98%.
Li-rich layered-layered-Spinel structure spherical Li1.3Mn4/6Ni1/6Co1/6O2.40 particles was successfully prepared and coated with a uniform layer by a two-step co-precipitation method and evaluated in lithium cells. The structures and electrochemical properties of pristine Li1.3Mn4/6Ni1/6Co1/6O2.40 and AlF3-coated Li1.3Mn4/6Ni1/6Co1/6O2.40 were characterized. When the coating amount was 2 wt%, the cathode showed the best cycling performance and rate capability compared to others. The AlF3-coated Li1.3Mn4/6Ni1/6Co1/6O2.40 Li-ion cell cathode had a capacity retention of 90.07 % after 50 cycles at 0.5 C over 2.0–4.8 V, while the pristine Li1.3Mn4/6Ni1/6Co1/6O2.40 exhibited capacity retention of only 80.73 %. Moreover, the rate capability and cyclic performance also improved. Electrochemical impedance spectroscopy testing revealed that the improved electrochemical performance might attribute to the AlF3 coating layer which can suppress the increase of impedance during the charging and discharging process by preventing direct contact between the highly delithiated active material and electrolyte. 相似文献
To suppress the capacity fade of Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 material as cathode materials for lithium-ion battery, we introduce a LiF coating layer on the surface to improve the cycling performance of Li1.2Ni0.13Co0.13Mn0.54O2 material. The modified sample shows a capacity of 163.2 mAh g?1 with a capacity retention of 95% after 100 cycles at a current density of 250 mA g?1, while the pristine sample only delivers a capacity of 129.9 mAh g?1 with a capacity retention of 82%. Compared with the pristine material, the LiF-modified sample exhibits an obvious enhancement in the electrochemical performance, which will be very beneficial for this material to be commercialized on the new energy vehicles and other related areas. 相似文献
Carbon-coated olivine-structured LiFe0.5Co0.5PO4 solid solution was synthesized by a facile rheological phase method and applied as cathode materials of lithium-ion batteries. The nanostructure’s properties, such as morphology, component, and crystal structure for the samples, characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer, Emmett, and Teller (BET) determination, X-ray photoelectron spectroscopy (XPS), and the electrochemical performances were evaluated using constant current charge/discharge tests and electrochemical impedance spectroscopy (EIS). The results indicate that nanoplatelet- and nanorod-structured LiFe0.5Co0.5PO4/C composites were separately obtained using stearic acid or polyethylene glycol 400 (PEG400) as carbon source, and the surfaces of particles for the two samples are ideally covered by full and uniform carbon layer, which is beneficial to improving the electrochemical behaviors. Electrochemical tests verify that the nanoplatelet LiFe0.5Co0.5PO4/C shows a better capacity capability, delivering a discharge specific capacity of 133.8, 112.1, 98.3, and 74.4 mAh g?1 at 0.1, 0.5, 1, and 5 C rate (1 C?=?150 mA g?1); the corresponding cycle number is 5th, 11th, 15th, 20th, and 30th, respectively, whereas the nanorod one possesses more excellent cycling ability, with a discharge capacity of 83.3 mAh g?1 and capacity retention of 86.9% still maintained after cycling for 100 cycles at 0.5 C. Results from the present study demonstrate that the LiFe0.5Co0.5PO4 solid solution nanomaterials with favorable carbon coating effect combine the characteristics and advantage of LiFePO4 and LiCoPO4, thus displaying a tremendous potential as cathode of lithium-ion battery. 相似文献
The poor electronic conductivity and low lithium-ion diffusion are the two major obstacles to the largely commercial application of LiFePO4 cathode material in power batteries. In order to improve the defects of LiFePO4, a novel carbon source polyacrylonitrile (PAN), which would form the hierarchical porous structure after carbonization, is fabricated and used. This work comes up with a simple and facile carbothermal reduction method to prepare porous-carbon-coated LiFePO4 (C-LiFePO4-PC) composite and to study the effect of carbon-coated temperature on ameliorating the electrochemical performance. The obtained C-LiFePO4-PC composite shows a high initial discharge capacity of 164.1 mA h g?1 at 0.1 C and good cycling stability as well as excellent rate capacity (49.0 mA h g?1 at 50 C). The most possible factors that improve the electrochemical performance could be related to the enhancement of electronic conductivity and the existence of porous carbon layers. In a word, the C-LiFePO4-PC material would become an excellent candidate for application in the fields of lithium-ion batteries. 相似文献