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)C4H6O3102.09-55 24099.7%1L $80.9Ethylene carbonate(EC)C3H4O388.06 35~38 99%1L $144Diethyl carbonate(DEC)(C2H5O)2CO118.13-431L $81.3Dimethyl carbonate(DMC)(CH3O)2CO90.082~4901L $51.5Ethyl methyl carbonate(EMC)C4H8O3104.10-14.0510750mL $132Methyl formateHCO2CH360.05-10032-341L $93.50Methyl acryrateCH2=CHCOOCH386.09-75801L $39.10Methyl butylateCH3CH2CH2COOCH102.18-95500mL $64.5Ethyl acetateCH3COOC2H588.11-8499.8%1L $67.9The 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.
4 The window of oxidation/reduction of electrolyte Solvent Oxidation Potential Li/Li+1M LiClO41 M LiPF6Propylene arbonate(PC)5.8V>6.0VEthylene carbonate(EC)5.8V*Dimethyl carbonate(DMC)5.7VDiethyl 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 LiClO4SolventPotential values for solvent Reduction (Li/Li+) composite carbonPC1.00~1.60VEC1.36VDEC1.32VDMCVinylene Carbonate (VC)1.40V3.5(volt)(lithium salt LiPF6)SolventGlassy CarbonActivated CarbonReduction(V)Oxidation(V)EC0.1096.7021.9404.602PC0.2325.9812.2534.422EC/DMC0.1536.6862.2074.521PC/DMC0.1845.7832.2004.101EC/EMC0.1006.6832.0554.576PC/EMC0.1146.2012.0324.237Acetonitrile(AN)0.0735.5062.2014.018
7 Mixed solvent electrolyte for high voltage lithium metal secondary cells 1.0 M LiClO4, PC-mixed with varioussolvents (1:1)1.0 M LiClO4, EC-mixed with varioussolvents (1:1)1.0 M LiPF6, PC-mixed with varioussolvents (1:1)1.0 M LiPF6, EC-mixed with varioussolvents (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/DMCand (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.
10 Dependence of conductance, κ, on molality, m. 40oC35oC30oC25oC20oCthe curves to the calculated according to Eq. (1) values.15oCEq. (1)μ is the molality that corresponds to the maximum conductivity, κ(max), and a, b constants.
11 at 25◦ CLiAsF6LiPF6LiClO4LiBF4The 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 ionicdissociation 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 .LiAsF6LiPF6LiClO4LiBF4specific 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 electrolytesLithium salts have been usedLiClO4, LiCF3SO3, LiPF4, LiPF6 X Low solubility. σ(25oC)~10-7LiC(CF3SO2)3, LiN(SO2CF2CF3)2 σ(25oC)~10-5PlasticizersPoly(ethylene glycol)-dimethacrylate (PEGMA)Poly(ethylene glycol)-monomethacrylate (PME)
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 thesolution 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
21 Effect of concentration and grain size of alumina filler on the ionic conductivity enhancement of the (PEO)9LiCF3SO3:Al2O3 composite polymer electrolyteThe 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 fillerconcentration 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 electrolyteImpedance response at various temperatures of the LiPF6/DMC/PAN +6wt%Al2O3 composite gel electrolyte.Adding of Al2O3 improve the stability of the electrolyte
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 numberContribution from hoppingMeasured conductivityContribution from polymer chain motionVolume fraction of ceramic phase1.00.7220.127.116.11
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.