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鋰電池的電介質=鋰鹽+有機溶劑+聚合物+其他添加物

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Presentation on theme: "鋰電池的電介質=鋰鹽+有機溶劑+聚合物+其他添加物"— Presentation transcript:

1 鋰電池的電介質=鋰鹽+有機溶劑+聚合物+其他添加物
液態電解質:鋰鹽+有機溶劑 固態電解質:鋰鹽+聚合物 膠態電解質:鋰鹽+有機溶劑+聚合物 電解質中常用的鋰鹽 名稱 化學式 莫耳重(g) 熔點( °C) 純度與價錢(美金) Lithium hexafluoroarsenate LiAsF6 195.86 349 98% 10g $112 Lithium hexafluorophosphate LiPF6 151.91 200 99.99% 5g $76.5 Lithium tetrafluoroborate LiBF4 93.75 99.998% 5g $125 Lithium trifluoromethanesulfonate CF3SO3Li 156.01 >300 99.995% 5g $45 Lithium perchlorate LiClO4 106.39 236 10g $48.8 LiAsF6 須考慮毒性, LiBF4 與 CF3SO3Li 導電係數較低, LiClO4 可能會爆炸, LiPF6 價錢較貴。 battery grade是指純度達99.9%以上。

2 電解質中常用的有機溶劑 名稱 化學式 莫耳重(g) 熔點(°C) 沸點(°C) 純度與價錢(美金) Propylene arbonate
(PC) C4H6O3 102.09 -55  240 99.7% 1L $80.9 Ethylene carbonate (EC) C3H4O3 88.06  35~38  99% 1L $144 Diethyl carbonate (DEC) (C2H5O)2CO 118.13 -43   1L $81.3 Dimethyl carbonate (DMC) (CH3O)2CO 90.08 2~4 90 1L $51.5 Ethyl methyl carbonate (EMC) C4H8O3 104.10 -14.05 107 50mL $132 Methyl formate HCO2CH3 60.05 -100 32-34 1L $93.50 Methyl acryrate CH2=CHCOOCH3 86.09 -75 80 1L $39.10 Methyl butylate CH3CH2CH2COOCH 102.18 -95 500mL $64.5 Ethyl acetate CH3COOC2H5 88.11 -84 99.8% 1L $67.9 The electrolyte in lithium batteries may have a mixture of lithium salts and organic solvents. The electrolyte’s concentration in the solvent ranges from 0.1 to 2 mol/L, with an optimal range of 0.8–1.2 mol/L.

3 電解質中常用的聚合物 名稱 化學式 玻璃轉換點(°C) 熔點(°C) 純度與價錢 (美金) Poly(ethylene oxide) PEO
–(CH2CH2O)n– -64 65 mw=100000 250g $106.50 Poly(acrylonitrile) PAN –(CH2–CH(–CN))n–  85 317 mw=150000 100g $184.5 Poly(propylene oxide) PPO –(CH(–CH3)CH2O)n– -60 ~67 Mn=2700 500g $110 Poly(vinylidene fluoride) PVDF –(CH2–CF2)n– -40 171 mw=180000 100g $87.30 Poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP (-CH2CF2-)x[-CF2CF(CF3)-]y -90 135 mw=400000 100g $41.50 Poly(methyl methacrylate) PMMA –(CH2C(–CH3)(–COOCH3))n 125 mw=350000 1kg $121 Poly(vinyl chloride) PVC –(CH2–CHCl)n 85 150~300 mw=80000 500g $46.00 Poly(acrylonitrile-co-methyl acrylate) [CH2CH(CN)]x[CH2CH(CO2CH3)]y acrylonitrile, ~94 wt. % 10g $70.3

4 The window of oxidation/reduction of electrolyte Solvent
Oxidation Potential Li/Li+ 1M LiClO4 1 M LiPF6 Propylene arbonate (PC) 5.8V >6.0V Ethylene carbonate (EC) 5.8V* Dimethyl carbonate (DMC) 5.7V Diethyl carbonate (DEC) 5.5V >6.0V** 1,2-Dumethoxy ethane (DME) 4.9V* 4.9V** 1,2-Diethoxy ethane (DEE) 4.7V* (PC) OH- CH3CH(OH)CH2OH + COH3-2 * Mixed with PC ** Mixed with EC

5 Potential values for solvent Reduction (Li/Li+) composite carbon
Lithium salt LiClO4 Solvent Potential values for solvent Reduction (Li/Li+) composite carbon PC 1.00~1.60V EC 1.36V DEC 1.32V DMC Vinylene Carbonate (VC) 1.40V 3.5 (volt) (lithium salt LiPF6) Solvent Glassy Carbon Activated Carbon Reduction(V) Oxidation(V) EC 0.109 6.702 1.940 4.602 PC 0.232 5.981 2.253 4.422 EC/DMC 0.153 6.686 2.207 4.521 PC/DMC 0.184 5.783 2.200 4.101 EC/EMC 0.100 6.683 2.055 4.576 PC/EMC 0.114 6.201 2.032 4.237 Acetonitrile (AN) 0.073 5.506 2.201 4.018

6 Conductivity(20oC)(Ω-cm)-1×10-3
Co-solvent Conductivity(20oC)(Ω-cm)-1×10-3 PC mixed solvent electrolyte EC mixed solvent electrolyte 1M LiClO4 1M LiPF6 DME 12 14 15 DEE 7.5 9.5 8.5 10 DMC 6.5 8 DEC 4 7 6

7 Mixed solvent electrolyte for high voltage lithium metal secondary cells
1.0 M LiClO4, PC-mixed with various solvents (1:1) 1.0 M LiClO4, EC-mixed with various solvents (1:1) 1.0 M LiPF6, PC-mixed with various solvents (1:1) 1.0 M LiPF6, EC-mixed with various solvents (1:1) (1) DME, (2) DEE, (3) DMC, (4) DEC

8 conductivity using each 1. 0 M solute EC/DMC electrolyte
conductivity using each 1.0 M solute EC/DMC electrolyte. (1) LiClO4, (2) LiBF4, (3) LiPF6, (4)LiAsF6. conductivity using (1) 1.0M-LiPF6-EC/DMC and (2) 1.5M-LiPF6-EC/DMC. conductivity is LiAsF6 > LiPF6 > LiClO4 > LiBF4 > electrolyte. Cycling performance of Li/LiMn1.9Co0.1O4 cells using (1) 1.0M-LiPF6-EC/DMC and (2) 1.5M-LiPF6-EC/DMC. 1.5M-LiPF6-EC/DMC are less advantageous than those of 1.0M-LiPF6-EC/DMC. Cycling performance of Li/LiMn1.9Co0.1O4 cells using each 1.0 M solute EC/DMC electrolyte. (1) LiClO4, (2) LiBF4, (3)LiPF6.

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10 Dependence of conductance, κ, on molality, m.
40oC 35oC 30oC 25oC 20oC the curves to the calculated according to Eq. (1) values. 15oC Eq. (1) μ is the molality that corresponds to the maximum conductivity, κ(max), and a, b constants.

11 at 25◦ C LiAsF6 LiPF6 LiClO4 LiBF4 The higher conductivities of LiAsF6 and LiPF6 can be explained with the larger anion radius of these salts, compared with that of LiClO4 and LiBF4, which means that the ionic dissociation ability of LiAsF6 and LiPF6 is higher than that of LiClO4 and LiBF4 as the coulombic force between Li+ and the anion is weaker for larger radii . LiAsF6 LiPF6 LiClO4 LiBF4 specific capacity for Li/Li1.05Mn2O4 cells with electrolyte solutions 1m salt in PC 50.7%–DEC 49.3% (temperature 25 ◦C).

12 Lithium polymer electrolytes
The lithium polymer electrolytes have a full plastic structure. Such plastic lithium ion batteries are expected to be less expensive and more easily scaled up than their liquid counterparts. In addition, the absence of free liquid allows packaging in light-weight plastic containers unlike conventional batteries which require metallic casing. Finally, since the electrolyte membrane and the associated plasticized electrodes can be formed as 1aminates, the plastic battery can be fabricated in any desired shape or size, a target difficult to be achieved with liquid electrolyte cells. All these features make the plastic lithium battery a very appealing product. The key component of the plastic battery is the polymer electrolyte membrane that has to fulfill a series of stringent requirements, including among others: i) good mechanical properties (to assure easy battery fabrication), ii) high ionic conductivity (to assure low internal resistance), iii) high lithium ion transport (to avoid concentration polarization), iv) wide electrochemical stability (to be compatible with high voltage electrodes), v) low cost (in order to fill a large market), and vi) benign chemical composition (to be environmentally compatible).

13 Solid Polymer Electrolytes (No volatile organic solvents)
Basic unit of polymer matrix chains for polymer electrolytes Lithium salts have been used LiClO4, LiCF3SO3, LiPF4, LiPF6 X Low solubility. σ(25oC)~10-7 LiC(CF3SO2)3, LiN(SO2CF2CF3)2 σ(25oC)~10-5 Plasticizers Poly(ethylene glycol)-dimethacrylate (PEGMA) Poly(ethylene glycol)-monomethacrylate (PME)

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17 Two kinds of gelled polymer electrolytes
additive Lithium salts additive solvent gel formed gel formed Soaking gel into liquid electrolyte 加熱與攪拌 加熱與攪拌 Lithium salts solvent Liquid electrolyte

18 Electrolyte composition Conductivity(Ω-cm)-1×10-3 Oxidation Potential (V) Li/Li+ LiClO4-EC-PC-PAN 1.1 5.0 4.9 LiClO4-EC-DMC-PAN 3.9 5.1 LiClO4-EC-DEC-PAN 4.0 4.8 LiClO4-γBL-PAN 2.8 LiAsF6-EC-PC-PAN 0.9 4.3 LiAsF6-γBL-PAN 4.1 4.6 LiPF6-γBL-PAN 4.4 LiPF6-EC-γBL-PAN 5.5 LiPF6-EC-DMC-PAN 4.2 LiN(SO2CF3)2-EC-PC-PAN 1.0 LiN(SO2CF3)2-EC-γBL-PAN 2.6 4.7 LiClO4-EC-PC-PMMA 0.7 LiAsF6-EC-PC-PMMA 0.8 LiN(SO2CF3)2-EC-PC-PMMA LiN(SO2CF3)2-EC-DMC-PMMA LiN(SO2CF3)2-EC-DBF-PVdF 0.017 LiN(SO2CF3)2-EC-DBF-PVdF(C3F6) 0.035 LiN(SO2CF3)2-EC-DBF-PVdF(CTFE) 0.1

19 Composite polymer electrolytes based on PAN, LiClO4 and α-Al2O3
To prepare the electrolyte, first, an appropriate amount of PAN was dissolved with a small amount of DMF. Then, the required quantity (F=[LiClO4]/[CN], where F represents the the molar ratio of salt fed to a PAN repeat unit) of the lithium salt was added, and the solution was stirred well. A designed amount of α-Al2O3 powder was then added and the PAN/LiClO4/α-Al2O3 solution was stirred continuously by a high intensity ultrasonic finger directly immersed in the solution for 24 h to disperse the particles. After this, the solution was cast on a flat glass and dried in a vacuum oven at a proper temperature to remove the solvent for at least 24 h. The mechanically stable membranes obtained have average thickness of about 100 μm. The DMF residue in the membranes estimated from TGA measurement was less than 10 wt.%. The dried samples were stored in an argon-filled glove box (water is less than 5 ppm) to avoid moisture contamination. melting of the microcrystalline domains. Tg

20 NF6A7.5 LiClO4 =0.6 wt.% of Al2O3

21 Effect of concentration and grain size of alumina filler on the ionic conductivity enhancement of the (PEO)9LiCF3SO3:Al2O3 composite polymer electrolyte The nanoporous Al2O3 powder have a pore size 5.8 nm, particle size 104 μm, surface area 155 m2/g and acidic surface groups, and the Al2O3 powder have grain size<10 μm, 37 and 10–20 nm.

22 Variation of ionic conductivity at 30oC with specific surface area of alumina grains for the composite polymer electrolyte PEO9LiTf t -Al2O3. the nano-porous alumina grains with 5.8 nm pore size and 150 m2/g specific area and 15 wt.% filler concentration exhibited the maximum enhancement.

23 The composite polymer electrolyte system at low filler concentrations may be imagined as a conducting medium where filler grains are randomly and uniformly distributed throughout the volume. The presence of the filler grains could give rise to additional favourable conducting pathways in the vicinity of the surface of the grains as described earlier. The number of such additional high conductivity pathways is expected to increase with increasing filler surface area. At low enough filler concentrations, where the grains are still well separated these surface interactions can therefore account for the observed conductivity increase with increasing filler concentration. At somewhat higher filler concentrations, however, the blocking effect or the geometrical constrictions imposed bythe more abundant alumina grains could make the long polymer chains more ‘‘immobilized’’ leading to a lower conductivity. This would lead to the appearance of the first conductivity maximum and the subsequent drop in conductivity. As the filler concentration is further increased, the filler grains get close enough to each other so that the high conducting regions in the vicinity of the grain surfaces start to get interconnected. The migrating ionic species can now travel along and between these interconnected high conducting pathways giving rise to the second increase in the conductivity. Finally, at still higher filler concentrations, the grains get so close to each other that the blocking effect due to the neutral filler becomes large and the conductivity starts to drop. This can explain the existence of the second maximum in the variation of the conductivity versus composition plots.

24 Sketch depicting how PEO chains enter the nanoporous tunnels of alumina grains in a PEO based nano-composite electrolyte. The observed conductivity enhancement has been attributed to Lewis acid–base type surface interactions of ionic species with O/OH groups on the filler surface, with an additional contribution below 60oC coming from the retention of an increased fraction of the amorphous phase due to the presence of the filler. The conductivity versus filler concentration curves exhibit two conductivity maxima which has been explained in terms of the surface interactions, blocking effect and grain consolidation. The conductivity enhancement appears to saturate beyond 100 m2/g grain surface area.

25 Adding of Al2O3 improve the stability of the electrolyte
Time (days) Time evolution of the conductivity of LiPF6/DMC/PAN +6wt%Al2O3 composite gel electrolyte Impedance response at various temperatures of the LiPF6/DMC/PAN +6wt%Al2O3 composite gel electrolyte. Adding of Al2O3 improve the stability of the electrolyte

26 Li/EC/LiClO4/PAN5+1%Al2O3/LiFePO4
利用交流阻抗分析電池介面,發現添加α-Al2O3有效降低介面阻抗,介面阻抗包含SEI與電荷轉移阻抗,添加α-Al2O3對於降低SEI明顯有所幫助,而且隨添加比重越高電路模擬的擬合阻抗值越低,電荷轉移阻抗則是推論因掃描範圍原因,無法完整檢測阻抗隨比例變化,但還是對於阻抗降低有所幫助。 電壓V.S時間 充放電平台表現圖

27 Contribution from polymer chain motion
Schematic representation of conductivity at ambient temperature; contributions from ion hopping and polymer chain motion and transport number. Conductivity (arbitrary units) Transfer number Contribution from hopping Measured conductivity Contribution from polymer chain motion Volume fraction of ceramic phase 1.0 0.75 0.5 0.25 0.0

28 不合適當添加物 The ceramic particles, depending upon the volume fraction, would tend to minimize the area of lithium electrode exposed to polymers containing O, OH species and thus reduce the passivation process. It is also foreseeable that smaller size particles for a similar volume fraction of the ceramic phase would impart improved performance compared to larger size particles because they cover more surface area. The formation of an insulating layer of ceramic particles at the electrode surface is probable at higher volume fraction of a passive ceramic phase. The experimental evidence is numerous and consistently show that the lithium-composite electrolyte interfaces are more stable and efficient than lithium-polymer electrolyte interfaces. Schematic diagram of lithium-composite electrolytes (a) larger size particles, and (b) smaller size particles.


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