lithium salt LiPF 6

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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
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)
Lithium hexafluoroarsenate
LiAsF6
195.86
349
Lithium
hexafluorophosphate
Lithium tetrafluoroborate
LiPF6
151.91
200
LiBF4
93.75
293-300
Lithium
trifluoromethanesulfonate
Lithium perchlorate
CF3SO3Li 156.01
LiClO4
106.39
>300
236
純度與價錢
(美金)
98%
10g $112
99.99%
5g $76.5
99.998%
5g $125
99.995%
5g $45
99.99%
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。
電解質中常用的有機溶劑
名稱
化學式
Propylene arbonate
(PC)
Ethylene carbonate
(EC)
Diethyl carbonate
(DEC)
Dimethyl carbonate
(DMC)
Ethyl methyl carbonate
(EMC)
Methyl formate
C4H6O3
Methyl acryrate
CH2=CHCOOCH3
Methyl butylate
CH3CH2CH2COOCH
Ethyl acetate
CH3COOC2H5
C3H4O3
(C2H5O)2CO
(CH3O)2CO
C4H8O3
HCO2CH3
莫耳 熔點(°C) 沸點(°C) 純度與價錢
重(g)
(美金)
102.09 -55
240
99.7%
1L $80.9
88.06
35~38
243-244 99%
1L $144
118.13 -43
126-128 99%
1L $81.3
90.08 2~4
90
99%
1L $51.5
104.10 -14.05
107
99%
50mL $132
60.05 -100
32-34
99%
1L $93.50
86.09 -75
80
99%
1L $39.10
102.18 -95
102-103 99%
500mL $64.5
88.11 -84
76.5-77.5 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.
電解質中常用的聚合物
名稱
Poly(ethylene oxide)
PEO
Poly(acrylonitrile)
PAN
Poly(propylene oxide)
PPO
Poly(vinylidene fluoride)
PVDF
Poly(vinylidene fluorideco-hexafluoropropylene)
PVDF-HFP
Poly(methyl methacrylate)
PMMA
Poly(vinyl chloride)
PVC
Poly(acrylonitrile-comethyl acrylate)
化學式
–(CH2CH2O)n–
–(CH2–CH(–CN))n–
–(CH(–CH3)CH2O)n–
–(CH2–CF2)n–
(-CH2CF2-)x[-CF2CF(CF3)-]y
玻璃轉換 熔點
純度與價錢
點(°C)
(°C)
(美金)
-64
65
mw=100000
250g $106.50
85
317
mw=150000
100g $184.5
-60
~67
Mn=2700
500g $110
-40
171
mw=180000
100g $87.30
-90
135
mw=400000
100g $41.50
–(CH2C(–CH3)(–COOCH3))n
125
–(CH2–CHCl)n
85
[CH2CH(CN)]x[CH2CH(CO2CH3)]y
317
mw=350000
1kg $121
150~ mw=80000
300
500g $46.00
acrylonitrile,
~94 wt. %
10g $70.3
The window of oxidation/reduction of electrolyte
Oxidation Potential Li/Li+
Solvent
1M LiClO4
1 M LiPF6
Propylene arbonate
(PC)
5.8V
>6.0V
Ethylene carbonate
(EC)
5.8V*
>6.0V
Dimethyl carbonate
(DMC)
5.7V
>6.0V
Diethyl carbonate
(DEC)
5.5V
>6.0V**
(PC)
1,2-Dumethoxy ethane 4.9V*
(DME)
4.9V**
4.7V*
4.9V**
1,2-Diethoxy ethane
(DEE)
*
Mixed with PC
**
Mixed with EC
+ 2OH-
CH3CH(OH)CH2OH + COH3-2
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
1.32V
Vinylene Carbonate (VC)
1.40V
3.5
(volt)
(lithium salt
LiPF6)
Solvent
Glassy Carbon
Activated Carbon
Reduction(V)
Oxidation(V)
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
Cosolvent
Conductivity(20oC)(Ω-cm)-1×10-3
PC mixed solvent
electrolyte
EC mixed solvent
electrolyte
1M LiClO4
1M LiPF6
1M LiClO4
1M LiPF6
DME
12
14
14
15
DEE
7.5
9.5
8.5
10
DMC
6.5
10
8
10
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 LiPF6, PC-mixed with various
solvents (1:1)
1.0 M LiClO4, EC-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
conductivity using each 1.0 M solute EC/DMC
electrolyte. (1) LiClO4, (2) LiBF4, (3) LiPF6,
(4)LiAsF6.
conductivity is LiAsF6 > LiPF6 > LiClO4 >
LiBF4 > electrolyte.
conductivity using (1) 1.0M-LiPF6-EC/DMC
and (2) 1.5M-LiPF6-EC/DMC.
Cycling performance of Li/LiMn1.9Co0.1O4 cells
using (1) 1.0M-LiPF6-EC/DMC and (2) 1.5MLiPF6-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.
1.5M-LiPF6-EC/DMC are less advantageous
than those of 1.0M-LiPF6-EC/DMC.
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.
at 25◦ C
LiAsF6
LiPF6
LiClO4
LiBF4
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 .
specific capacity for Li/Li1.05Mn2O4
cells with electrolyte solutions 1m salt
in PC 50.7%–DEC 49.3% (temperature
25 ◦C).
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 lightweight 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).
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)
Two kinds of gelled polymer electrolytes
polymer
Lithium salts
additive
solvent
polymer additive
gel formed
gel formed
加熱與攪拌
加熱與攪拌
Lithium salts
solvent
Liquid electrolyte
Soaking gel into
liquid electrolyte
Electrolyte
composition
Conductivity(Ω-cm)-1×10-3
Oxidation Potential (V) Li/Li+
LiClO4-EC-PC-PAN
8.0-38.0-33.0-21.0
1.1
5.0
LiClO4-EC-PC-PAN
4.5-56.5-23.0-16.0
1.1
4.9
LiClO4-EC-DMC-PAN
4.5-56.5-23.0-16.0
3.9
5.1
LiClO4-EC-DEC-PAN
4.5-53.5-19.0-23.0
4.0
4.8
LiClO4-γBL-PAN
4.5-79.5-16.0
2.8
5.0
LiAsF6-EC-PC-PAN
4.5-56.5-23.0-16.0
0.9
4.3
LiAsF6-γBL-PAN
4.5-79.5-16.0
4.1
4.6
LiPF6-γBL-PAN
4.5-79.5-16.0
4.4
5.1
LiPF6-EC-γBL-PAN
4.5-56.5-23.0-16.0
5.5
4.6
LiPF6-EC-DMC-PAN
4.0-20.0-62.0-14.0
4.2
4.4
LiN(SO2CF3)2-EC-PC-PAN
4.5-56.5-23.0-16.0
1.0
4.6
LiN(SO2CF3)2-EC-γBL-PAN
4.5-56.5-23.0-16.0
2.6
4.7
LiClO4-EC-PC-PMMA
4.5-46.5-19.0-30.0
0.7
4.6
LiAsF6-EC-PC-PMMA
4.5-46.5-19.0-30.0
0.8
4.8
LiN(SO2CF3)2-EC-PC-PMMA
4.5-46.5-19.0-30.0
0.7
4.9
LiN(SO2CF3)2-EC-DMCPMMA
5.0-50.0-20.0-25.0
1.1
4.8
LiN(SO2CF3)2-EC-DBF-PVdF
3.5-36.5-30.0-30.0
0.017
LiN(SO2CF3)2-EC-DBFPVdF(C3F6)
3.5-36.5-30.0-30.0
0.035
4.8
LiN(SO2CF3)2-EC-DBFPVdF(CTFE)
1.2-42.0-16.8-40.0
0.1
4.6
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.
Tg
melting of the
microcrystalline
domains.
NF6A7.5
LiClO4 =0.6
wt.% of Al2O3
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.
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.
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.
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.
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
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
1.0
Transfer
number
Conductivity (arbitrary units)
0.5
Measured
conductivity
Transfer number
0.75
Contribution from
hopping
0.25
Contribution from
polymer chain motion
0
0.0
0.25
0.5
0.75
1.0
Volume fraction of ceramic phase
Schematic representation of conductivity at ambient temperature; contributions from ion hopping and
polymer chain motion and transport number.
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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