Electrochimica Acta 174 (2015) 230–237
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A novel dimethyl sulfoxide/1,3-dioxolane based electrolyte for lithium/ carbon fluorides batteries with a high discharge voltage plateau Chengkai Panga,b , Fei Dingb,** , Wenbin Sunb , Jiaquan Liua , Mingming Haob , Ying Wangb , Xingjiang Liua,b , Qiang Xua,* a b
Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, PR China National Key Laboratory of Science and Technology on Power Sources, Tianjin Institute of Power Sources, Tianjin 300384, PR China
A R T I C L E I N F O
A B S T R A C T
Article history: Received 15 March 2015 Received in revised form 31 May 2015 Accepted 2 June 2015 Available online 3 June 2015
A novel dimethyl sulfoxide/1,3-dioxolane (DMSO/1,3-DO) based electrolyte is proposed for lithium/carbon fluorides (Li/CFx) batteries to enhance the discharge voltage plateau and energy density. Conductivities of the electrolyte of 1 mol L1 LiBF4/DMSO+1,3-DO with different volume ratios are not identical, which have a maximum of 14.85 mS cm1. From the tests of galvanostatic discharge, the discharge voltage plateau of the Li/CFx battery with an electrolyte of 1 mol L1 LiBF4/DMSO+1,3-DO (5:5, v:v) can reach 2.69 V at 0.1 C, delivering a maximum discharge capacity of 831 mAh g1 and the highest energy density of 2196 Wh kg1. Compared to Li/CFx batteries with an electrolyte of 1 mol L1 LiBF4/PC +DME (5:5, v:v), the energy density of Li/CFx batteries with an electrolyte of 1 mol L1 LiBF4/DMSO+1,3DO (5:5, v:v) has been improved more than 12%. With the help of XRD, SEM, TEM, EIS, FT-IR and GC-MS analysis, the results of this work suggest that DMSO/1,3-DO based electrolyte can significantly improve the discharge performance of Li/CFx batteries and keep a good electrochemical stability during discharge. The main reason for improvement of discharge performance is decreasing of both the overpotential of electrochemical polarization of CFx cathodes during discharge and the overpotential of ohmic polarization by increasing the ion conductivity of electrolyte. ã2015 Elsevier Ltd. All rights reserved.
Keywords: Lithium/Carbon fluorides batteries Electrolyte Dimethyl sulfoxide Energy density Discharge voltage
1. Introduction Li/CFx cells are known to have the highest theoretical specific capacity when compared to other primary lithium batteries, such as Li/SOCl2 and Li/MnO2 batteries [1,2]. These batteries with high energy density are being developed for military, spacial and medical applications, such as soldier portable power sources, space long term exploratory missions and implantable medical devices [3,4]. Theoretically, a CFx with x=1 has a high specific capacity of 865 mAh g1, about twice that of SOCl2 currently used in primary Li/SOCl2 batteries [5]. In most non-aqueous liquid electrolyte, CFx (x=1) cathode has an open circuit potential of 3.2-3.5 V (vs. Li/Li+) [6]. However, the discharge voltage plateau of a real Li/CFx cell (x=1)(2.5 V) is much lower than this value, showing significant polarization [7]. The reasons for this high polarization are mostly related to the low electronic conductivity of CFx materials and to the slow kinetics of cell reactions [8].
* Corresponding author. Tel.: +86-022-27890322; fax: +86-022-27401684. ** Corresponding author. Tel.: +86-022-23959712; fax: +86-022-23383783. E-mail addresses:
[email protected] (F. Ding),
[email protected] (Q. Xu). http://dx.doi.org/10.1016/j.electacta.2015.06.004 0013-4686/ ã 2015 Elsevier Ltd. All rights reserved.
In previous reports, much effort has been focused on the improvement of CFx materials. These efforts include the study of various preparation methods of CFx materials, construction of highly conductive collector and surface modification of CFx cathodes [9–17]. Besides the CFx materials, it is noteworthy that the electrolyte is another key factor on discharge performance of Li/CFx batteries [18,19]. It is well known that the electrolyte requires high ionic conductivity, low melting point, high boiling point, and good electrochemical stability for high-performance batteries [20,21]. It is also well known that the electrolyte of Li/CFx cells is composed of a lithium salt and an organic solvent blend. Conventional lithium salts contain LiBF4 [22], LiPF6 [23], LiAsF6 [4], and LiClO4 [24]. The solvents are the mixture of some organic solutions, which include carbonate solvents (EC, PC, DMC, EMC) and ether reagents (DEC, TEE) [25–28]. Recently, some new solvents as a component of electrolyte have been developed to further improve the discharge performance of Li/CFx batteries. G. Nagasubramanian et al. reported a chemical approach to improve the discharge performance of Li/CFx cells by adding an ABA{Tris (1,1,1,3,3,3-hexafluoroisopropyl) borate} additive in the electrolyte of Li/CFx batteries [23]. They found that the ABA additive may dissolve the LiF from the plugging pores on cathode surface and
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keep the bulk of cathode accessible for further discharge reaction. S.S. Zhang et al. used a mixed solution of acetonitrile (AN) and g-butyrolactone (BL) as the solvent of low temperature electrolyte for high energy density Li/CFx batteries. They found that the use of AN/BL electrolyte (0.5 mol L1 LiBF4, 1:1 AN/BL) in Li/CFx cells can improve the power capability and low temperature performance [29]. E. Rangasamy et al. reported a high energy density Li/CFx cell with a solid bifunctional electrolyte of Li3PS4. The bifunctional electrolyte of Li3PS4 may reconcile both inert and active characteristics through a synergistic discharge mechanism of CFx and Li3PS4 [18]. In order to further improve the discharge performance, it is necessary to develop more new electrolyte of Li/CFx batteries. Unfortunately, the study on improvement of the electrolyte of Li/CFx batteries has not been paid enough attention until now. The electrolyte of Li/CFx batteries should satisfy many requirements, i.e. ionic conductivity, volatility, viscosity, electrochemical stability and safety [30]. Dimethyl sulfoxide (DMSO), as a highly polar versatile solvent, has favorable advantages, including high dielectric constant (46.68, at 298 K), large dipole moment (4.3 Debye at 298 K) and low volatility (B.P. 189.1C). Especially, DMSO exhibits a high salt solubility to produce well-conducting solutions with a wide electrochemical window in non-aqueous batteries [31]. However, it is highly desirable but still unexplored to investigate the electrochemical behaviors of DMSO-based electrolyte in Li/CFx batteries. Owing to the high viscosity (1.948 cP), DMSO is commonly used as the electrolyte mixed with other low viscosity solvents [32]. 1,3-dioxolane (1,3-DO), as a cyclic ether with low dielectric constant and low viscosity, has been commonly used as a solvent of non-aqueous electrolyte [33]. In this study, the DMSO/1,3-DO solution as a mixed solvent of electrolyte for Li/CFx batteries was prepared and characterized. Both ionic conductivities and viscosities of the electrolyte of 1 mol L1 LiBF4/DMSO+1,3DO with different volume ratios of solvents have been investigated. Moreover, the discharge behavior of Li/CFx batteries with DMSO/1,3-DO based electrolyte is also studied. It is noteworthy that the electrolyte of 1 mol L1 LiBF4/DMSO+1, 3-DO (v:v, 5:5) can enhance the discharge voltage plateau and energy density of Li/CFx batteries evidently. 2. Experimental CFx (x=0.99-1.08, Daikin Corp Japan) was used as the cathode material. LiBF4 (Battery grade) was obtained from Guotai-Huarong Co.Ltd (China). Dimethyl sulfoxide (DMSO), 1,3-dioxolane (1,3-DO), propylene carbonate (PC), 1,3-dimethoxy ethane (DME) and other organic solvents (battery grade) were purchased from Aladdin and used without further treatment. 2.1. Preparation of the electrolyte The electrolyte was prepared in an argon-filled glove box (Mikrouna Advanced 1440/750, H2O<0.1 ppm, O2<0.1 ppm). DMSO and 1,3-DO solvents were mixed with different volume ratios, and then LiBF4 was dissolved in the mixed solution. Similarly, LiBF4/PC+DME (5:5,v:v) solution was prepared as the
Table 1 Compositions of five electrolyte samples (Concentration of electrolyte: 1 mol L1) Sample
Lithium salt
Solvent
A B C D E
LiBF4 LiBF4 LiBF4 LiBF4 LiBF4
DMSO/1, DMSO/1, DMSO/1, DMSO/1, PC/DME
Solvent volume ratio 3-DO 3-DO 3-DO 3-DO
1:9 3:7 5:5 7:3 5:5
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control electrolyte. Compositions of the five electrolyte samples, which contain the DMSO/1,3-DO based and the PC/DME based solutions, are listed in Table 1. The concentration of LiBF4 salt in every sample is the same, which is 1.0 mol L1. 2.2. Preparation of Li/CFx batteries The electrode film of cathode was mixed by 85 wt% CFx, 9 wt% Super P (M.M.M.Carbon Inc, Belgium) and 6 wt% LA133 aqueous binder (Chengdu Indigo, Co. Ltd, A acrylonitrile copolymer aqueous dispersion) in the distilled water. Then, the obtained slurry (0.4 mm thick) was coated onto an aluminum foil current collector. The coating was dried in an 110 C-oven for 12 h, and the resulting electrode film was cut into small disks with a diameter of 16 mm for coin cell testing. The electrode disks were further dried at 110 C under vacuum for 24 h, and then transferred into a glovebox for cell assembly. Each electrode contains around 8 mg of active materials. Li/CFx coin cells (CR2430) were assembled by using Celgard1 3500 membrane as the separator. A lithium foil (20mm diameter) was used as the anode. 2.3. Characterization The ionic conductivity of electrolyte was measured by using a conductometer (Mettler Toledo SevenExcellenceTM, Switzerland) in an argon-filled glove box. Ionic conductivity constant was determined with a standard KCl solution (0.01 mol L1). The measurements were repeated for three times, and the average value was given. The viscosity of electrolyte was tested by a coneplate viscometer (Brookfield, LVDV-III+CP). Coin cells were discharged on a Land Cell tester (CT2001A, Wuhan Jinnuo Electronics Company,China) and the cut-off voltage was set at 1.5 V. The electrochemical stability of electrolyte was tested on a simulated cell by using both Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) analytical methods before/after discharge (at 0.1 C). The FT-IR spectra were tested by a thermo-model Nicolet 6700 spectrometer. The combined instrument of GC-MS is Agilent Technologies 7890A/5975C. A HP-5MS capillary column (30 m0.32 mm0.25 mm) was used for separation, and a helium gas (99.99%) was used as the carrier gas (constant flow rate: 1 mL min1). X-ray diffraction (XRD) patterns of CFx cathodes were measured by a Rigaku D/max-2500 diffractometer with a Cu Ka radiation in the 2urange of 20 –80 . The surface morphologies of CFx cathodes were observed by a Hitachi S-4800 scanning electron microscopy (SEM). The grain size of LiF were investigated by a transmission electron microscope (TEM, JEM-2100F). Electrochemical impedance spectroscopy (EIS) of a two-electrode electrochemical cell was performed by using a Solartron Instruments Model 1400/1470E. A frequency range from 100 kHz to 0.01 Hz with an AC oscillation of 10 mV was used. All tests were performed at 25 C. 3. Results and discussion The electrochemical properties of electrolyte were firstly investigated. Both viscosities and conductivities of five electrolyte samples were shown in Table 2 and Table 3, respectively. The viscosities of DMSO/1,3-DO based electrolyte increase with decreasing the content of 1,3-DO, indicating that 1,3-DO may dilute the mixed solution effectively. Moreover, the ion conductivity of sample C is the highest among the five samples. The appearance of the maximum is generally explained by the synergetic effect of DMSO and 1,3-DO on ionic conductivity of the solution, which comes from the high solvating power of DMSO and the low viscosity of 1,3-DO [34].
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Table 2 Ionic conductivities of the electrolyte for five samples (mScm1) Sample .
Ionic conductivity
A B C D E
3.25 5.75 14.85 13.13 10
Table 3 Viscosities of the electrolyte for five samples (cP) Sample
Viscosity
A B C D E
1.55 1.98 2.02 2.59 2.03
Fig. 2. Discharge curves of the Li/CFx batteries with both the electrolyte of 1 mol L1 LiBF4/DMSO+1,3-DO (5:5, v:v) and the electrolyte of 1 mol L1 LiBF4/PC+DME (5:5, v:v) at 0.01 C, 0.05 C and 0.2 C.
The galvanostatic discharge curves of Li/CFx batteries with different samples at 0.1 C are represented in Fig. 1. From Fig. 1, it can be seen that the discharge voltage plateau of Li/CFx battery with an electrolyte of sample C has the highest value among these Li/CFx batteries, which may reach 2.69 V. This discharge voltage plateau is significantly superior to that of the Li/CFx battery with an electrolyte of sample E (2.5 V). From Fig. 1, the biggest discharge capacity and the highest energy density may be obtained from the Li/CFx battery with an electrolyte of sample C, which are 831 mAh g1 and 2196 Wh kg1, respectively. Compared to the Li/CFx battery with an electrolyte of sample E (1952 Wh kg1), the energy density of Li/CFx battery has been improved more than 12%. It is also noteworthy that the Li/CFx battery with an electrolyte of sample C has the maximum discharge voltage plateau and the highest ionic conductivity, simultaneously. This result shows that the reduction of ohmic resistance of electrolyte may increase the discharge voltage plateau of Li/CFx battery effectively. To further investigate the discharge performances of Li/CFx batteries with the DMSO/1,3-DO based electrolyte at different rates, Fig. 2 displays the discharge curves of Li/CFx batteries with two kinds of electrolyte at 0.01 C, 0.05 C and 0.2 C, respectively. As shown in Fig. 2, the discharge voltage plateau of Li/CFx batteries with an electrolyte of LiBF4/DMSO+1,3-DO (5:5, v:v) is significantly higher than that
of Li/CFx batteries with an electrolyte of LiBF4/PC+DME (5:5, v:v) at different rates. This result demonstrates that the DMSO/1,3-DO mixed solution with appropriate volume ratio is an ideal solvent of electrolyte for Li/CFx batteries instead of conventional PC/DME solvent. Fig. 3 represents the XRD patterns of CFx cathodes of Li/CFx batteries with different electrolyte after discharge at 0.1 C. In these patterns, the peak at 26.5 is the (002) reflection of graphite and all the peaks at 38 , 45 , 65 and 79 are attributed to reflection of LiF [35]. The sharp LiF peaks indicate the crystalline nature of LiF product. Compared to the XRD pattern of CFx cathode with an electrolyte of sample E, there are no diffraction peaks for CFx cathodes with other electrolyte samples except for LiF and C. This result indicates that the discharge product of CFx cathode with the DMSO/1,3-DO based electrolyte is the same as that of CFx cathode with an electrolyte of LiBF4/PC+DME (5:5, v:v). There is no new phase appeared on the surface of CFx cathodes with the DMSO/1,3DO based electrolyte after discharge. Compared to the XRD pattern for CFx cathode with an electrolyte of sample E, the height of peaks at 38 , 45 for CFx cathodes with the electrolyte of sample A and
Fig. 1. Discharge curves of Li/CFx batteries for five samples at 0.1 C.
Fig. 3. XRD patterns of CFx cathodes after discharge at 0.1 C.
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sample B increases and the height of peaks at 65 and 79 decreases, suggesting that the growth of (200) and (111) planes holds dominant position among the crystal faces of LiF grains [36,37]. Similarly, the height of peaks at 38 , 45 for CFx cathodes with the electrolyte of sample C and D decreases, indicating that the growth of (200) and (111) planes of LiF grains has been suppressed. These results demenstrate that the kinetics of crystallization of LiF grains may be regulated by changing the composition of electrolyte during discharge. The SEM and TEM images of CFx cathodes after discharge at 0.1 C are shown in Fig. 4 and Fig. 5. As shown in Fig. 4, a layer of LiF particles can be found on the surface of all the CFx cathodes. Among these CFx cathodes, the LiF particles for CFx cathodes with the electrolyte of sample A, sample B and sample E are more uniform and compact. From Fig. 5, we can find that the grain size of LiF with different electrolyte samples is not the same, and LiF grains with the electrolyte of sample C and sample D are significantly smaller. These results also indicate that kinetics of crystallization of LiF
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grains can be modified through changing of the electrolyte, which is consistent with the XRD analysis. In general, the cathode reaction mechanism of Li/CFx batteries contains three steps: 1) The diffusion of solvated lithium ions in fluorine layer, 2) Formation of graphite intercalation compound (GIC) intermediate and the injection of electrons from current collector into CFx matrix, 3) Dissociation of GIC intermediate [38]. Furthermore, the volume of Li/CFx cell may swell accompanied by the formation of LiF crystals during discharge. A widely accepted discharge reaction of Li/CFx [39]: Anode: xLi + xS! x Li+ S+ x e
(1)
Cathode: CFx + x Li+ S + x e ! C(Li+ S-F)x
(2)
Overall reaction: CFx + x Li + xS! C(Li+ S-F)x
(3)
Fig. 4. SEM images of CFx cathodes after discharge at 0.1 C.
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Fig. 5. TEM images of CFx cathodes after discharge at 0.1 C.
Where S represents one or more solvent molecules coordinated with each lithium ion and the GIC intermediate subsequently decomposes into the final discharge products, carbon and lithium fluoride, as shown below:
C(Li+S-F)x! C + x LiF+ xS
(4)
During the process of discharge, the discharge product of LiF will continue to dissolve, diffuse and recrystallize in both carbon-shell
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and free volume of the CFx cathode [40]. Because the recrystallization behavior of LiF grains is according to the mechanism of Ostwald ripening under diffusion control in two dimensions [41], the kinetics of crystallization of LiF depends on the migration velocity of solvated lithium ions through the CFx matrix. This results of SEM and TEM indicate that both the crystal shape and the grain size of LiF within CFx cathodes after discharge are related to the size of solvated lithium ions in different solvents of the electrolyte. In order to clarify the improvement of discharge performance of Li/CFx batteries with LiBF4/DMSO+1,3-DO electrolyte, Fig. 6 (a) and (b) display electrochemical impedance spectroscopy (EIS) spectra of Li/CFx batteries with different electrolyte at 30% and 100% depth of discharge (DOD) states, respectively, and the equivalent circuits for EIS patterns of Li/CFx batteries are presented in Fig. 6(c). As shown in the Fig. 6, the EIS spectra of these Li/CFx batteries at 30% and 100% DOD states are similar, and the interpretation of the impedance spectra is based on the equivalent circuit in Fig. 6(c) according to the previous report [42]. The bulk ohmic resistance (Rb) contributed to the combination of current collector, electrolyte, separator and electrode, is low for all the materials. On the interface between the liquid electrolyte and the discharge product shell, the charge-transfer through an existing electric double layer can be characterized by Qct and Rct at high frequency. The discharge product shell on the active material can be characterized by Q1 (a constant phase element) and R1 (resistance to lithium ion diffusion in the discharge product shell) at high frequency. After diffusing through the product shell, lithium ion reacts with CFx readily at the interface. Another constant phase element Qint is applied due to the lack of lithium ion diffusion in the active materials. Rct is the synergetic effects of the constant resistance among conductive particles, product shell resistance and chargetransfer resistance, corresponding to the depressed semicircle in the impedance plot. From Fig. 6(a) and (b), the diameter of semicircle at high frequency (R1) for sample E is larger than that of other samples evidently, indicating that the resistance of lithium ion diffusion into the discharge product shell of CFx cathodes with the DMSO/1, 3-DO based electrolyte is smaller than that of CFx cathode with an electrolyte of LiBF4/PC+DME (5:5, v:v). The onset between the semicircle and the sloped line is indicative of reaction kinetics with higher frequencies representing faster reaction kinetics, which indicates primarily low reaction resistance[25]. The frequencies between the onsets clearly marked in Fig. 6(a) and (b) demonstrate that the reaction kinetics of CFx cathode for sample E is lower than that of CFx cathodes for other samples, and that of CFx cathode for sample C is the fastest. These results suggest that the resistance of Rct through an existing electric double layer of CFx cathode with the DMSO/1, 3-DO based electrolyte is smaller than that of CFx cathode with an electrolyte of LiBF4/PC+DME (5:5, v:v). Compared to those samples at 30% DOD, both R1 and Rct for all the samples at 100% DOD become larger, indicating that the quantity of LiF increases with improvement of the DOD. Because the size of solvated lithium ions in DMSO/1,3-DO based electrolyte is not the same as that of solvated lithium ions in PC/DME based electrolyte [43–45], the resistance of solvated lithium ions intercalated into the CFx matrix can be reduced by using an electrolyte of LiBF4/DMSO+1,3-DO (5:5, v:v) instead of an electrolyte of LiBF4/PC+DME (5:5, v:v) [46]. These results of EIS suggest that the overpotential of electrochemical polarization for CFx cathode with an electrolyte of LiBF4/DMSO+1,3-DO (5:5, v:v) has been decreased. To further investigate the electrochemical stability of DMSO/1,3-DO based electrolyte during discharge, both FT-IR spectra and GC-MS patterns for the electrolyte of sample C before/after discharge at 0.1 C are shown in Fig. 7. As shown in Fig. 7(a), the FT-IR spectra have no difference between the
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Fig. 6. EIS spectra of Li/CFx batteries. (a) 30% DOD, (b) 100% DOD, (c) the equivalent circuit.
electrolyte before/after discharge. The peaks in the range of 2700–3000 cm1 correspond to the stretching mode of C–H bands for both DMSO and 1,3-DO solvents. Peaks at 1313 cm1, 1407 cm1 and 1437 cm1 are related to d(-CH3) of DMSO, and peaks at 1057 cm1 and 699 cm1, respectively, belong to n(S=O) and n(S-C) of DMSO. Moreover, peak at 1475 cm1 belongs to d(-CH2-) of 1,3-DO, and peaks at 1033 cm1 and 1087 cm1 belong to n(–CH2O-CH2-) of 1,3-DO. Compared to the spectrum of FT-IR before discharge, no new functional groups of electrolyte were found after discharge, indicating that the electrolyte of sample C is stable during discharge. As shown in Fig. 7 (b) and (c), no degradation products of electrolyte were detected after discharge, compared to the pattern of GC–MS for the electrolyte before discharge. This result also confirms that DMSO/1, 3DO based electrolyte is stable during discharge.
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Fig. 7. FTIR spectra and GC/MS patterns of the electrolyte of 1 mol L1 LiBF4/DMSO+1,3-DO (5:5, v:v) before and after discharge at 0.1 C. (a) FTIR spectra, (b, c) GC/MS patterns.
4. Conclusions A novel dimethyl sulfoxide/1,3-dioxolane (DMSO/1,3-DO) based electrolyte for Li/CFx batteries is prepared successfully, which may improve the discharge performance of Li/CFx batteries evidently. Conductivities of the electrolyte of 1 mol L1 LiBF4/DMSO+1, 3DO with different volume ratios of solvents are not identical, which has a maximum of 14.85 mScm1. The discharge voltage plateau of Li/CFx batteries with an electrolyte of 1 mol L1 LiBF4/DMSO+1,3DO (5:5, v:v) can reach 2.69 V at 0.1 C, delivering a maximum discharge capacity of 831 mAh g1 and the highest energy density of 2196 Wh kg1. Compared to the Li/CFx battery with an electrolyte of 1 mol L1 LiBF4/PC+DME (5:5, v:v), the energy density of Li/CFx battery with an electrolyte of 1 mol L1LiBF4/ DMSO+1,3-DO (5:5, v:v) has been improved more than 12%. The main discharge products of Li/CFx batteries with DMSO+1,3-DO based electrolyte are LiF and C, which are similar with that of the Li/CFx battery with PC/DME based electrolyte. On the basis of the results of XRD, SEM and TEM analyses, the kinetics of crystallization of LiF grains can be modified by changing of the electrolyte during discharge. From the FT-IR and GC-MS spectra analyses, the electrolyte of 1 mol L1 LiBF4/DMSO+1,3-DO (5:5, v:v) is stable during discharge. The improvement of discharge performance for
Li/CFx batteries with DMSO+1,3-DO based electrolyte is due to decreasing of both the electrochemical polarization of CFx cathodes during discharge and the ohmic polarization of electrolyte. In summary, DMSO/1,3-DO based electrolyte is a promising electrolyte for Li/CFx batteries. Acknowledgments This work was supported by the Foundation of National Key Laboratory of Science and Technology on Power Sources, P R China. References [1] S.J. Cheng, Z.Z. Yuan, X.P. Ye, F.Y. Zhang, J.C. Liu, Empirical prediction model for Li/SOCl2 cells based on the accelerated degradation test, Microelectronics Reliability 55 (2015) 101. [2] W.M. Dose, S.W. Donne, Optimising heat treatment environment and atmosphere of electrolytic manganese dioxide for primary Li/MnO2 batteries, Journal of Power Sources 247 (2014) 852. [3] R. Jayasinghe, A.K. Thapa, R.R. Dharmasena, T.Q. Nguyen, B.K. Pradhan, H.S. Paudel, J.B. Jasinski, A. Sherehiy, M. Yoshio, G.U. Sumanasekera, Optimization of Multi-Walled Carbon Nanotube based CFx electrodes for improved primary and secondary battery performances, Journal of Power Sources 253 (2014) 404. [4] P.J. Sideris, R. Yew, I. Nieves, K. Chen, G. Jain, C.L. Schmidt, S.G. Greenbaum, Charge transfer in Li/CFx-silver vanadium oxide hybrid cathode batteries
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