Tetrakisfluoroalkylborate salts and their use as conducting...

Details Tetrakisfluoroalkylborate salts and their use as conducting... Tetrakisfluoroalkylborate salts and their use as conducting...

2001-11-09

2004-11-09

Ryan, Patrick (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

C429S307000, C429S313000, C429S314000, C429S317000, C361S527000, C556S172000, C556S175000, C556S176000, C556S187000

Reexamination Certificate

active

06815119

ABSTRACT:

The present invention relates to tetrakisfluoroalkylborate salts, methods of producing same, and their use in electrolytes, batteries, capacitors, supercapacitors, and galvanic cells.
In recent years, the spreading of portable electronic devices such as laptop and palmtop computers, cell telephones, or video cameras and thus, the demand for light-weight and high-performance batteries has dramatically increased worldwide.
In view of such rapidly increasing demand for batteries and the associated ecological problems, the development of rechargeable batteries having long service life has become more and more important.
Starting in the early nineties, rechargeable lithium ion batteries have been traded commercially. Most of these batteries work with lithium hexafluorophosphate as conducting salt. However, this lithium salt is a compound which is extremely sensitive to hydrolysis and has low thermal stability and therefore, due to such properties of this salt, appropriate batteries can only be produced by means of highly expensive and thus, exceedingly cost-intensive processes. Also, the sensitivity of this lithium salt reduces the service life and the performance of such lithium batteries, impairing their use under extreme conditions, such as high temperatures.
Therefore, numerous attempts have been made to provide lithium salts having improved properties. Thus, U.S. Pat. Nos. 4,505,997 and 5,273,840 describe the use of lithium [tris(trifluoromethylsulfonyl)imide] or lithium [tris(trifluoromethylsulfonyl)methanide] salts as conducting salts in batteries. Both of these salts have high anodic stability, forming solutions of high conductivity with organic carbonates. However, lithium bis(trifluoromethylsulfonyl)imide has the drawback of insufficient passivation of the aluminum metal functioning as cathodic current conductor in lithium batteries. On the other hand, the production and purification of lithium tris(trifluoromethylsulfonyl)methanide is only possible with exceedingly high efforts, so that the use of this salt as conducting salt in batteries massively increases the production cost of such lithium batteries.
Another lithium salt used in battery cells is lithium tetrafluoroborate. However, this salt has a relatively low solubility in most solvents, so that solutions thereof generally have low ionic conductivities.
It is therefore the object of the present invention to provide conducting salts that would exhibit no or only slight evidence of hydrolytic decomposition over a long period of time. Furthermore, these conducting salts also should have high ionic conductivity, high thermal stability and from good to very good solubility in usual solvents. Another object of the present invention is to improve or enhance the service life and performance of primary and secondary batteries, capacitors, supercapacitors and/or galvanic cells.
Said object is accomplished by providing tetrakisfluoroalkylborate salts of general formula (I)
M
n+
([BR
4
]
−
)
n
  (I)
wherein
M
n+
is a univalent, bivalent, or trivalent cation, each of the ligands R are the same and straight-chained or branched and represent (C
x
f
2x+1
), with 1≦x≦8, and n=1, 2 or 3.
Preferred are those tetrakisfluoroalkylborate salts of the invention having the general formula (I), wherein MM
n+
is an alkali metal cation, preferably a lithium, sodium or potassium cation, and more preferably a lithium cation, a magnesium or aluminum cation.
Furthermore, those tetrakisfluoroalkylborate salts of general formula (I) are preferred wherein the M
n+
cation is an organic cation, preferably a nitrosyl cation, a nitryl cation, or a cation of general formula [N(R
7
)
4
]
+
, [P(N(R
7
)
2
)
k
R
4−k
]
+
, with 0≦k≦4, or [C(N(R
7
)
2
)
3
]
+
, wherein each of the substituents R
7
are the same or different, representing
H,
C
o
F
2o+1−p−q
H
p
A
q
, or
A,
wherein
1≦o≦10, 0p≦2o+1, 0≦q≦2o+1, preferably 1≦o≦6, 0≦p≦2o+1, and 0≦q≦2o+1, and A represents an aromatic residue optionally having heteroatoms, or a preferably 5- or 6-membered cycloalkyl residue.
All of the aromatic, heteroaromatic or cycloaliphatic compounds well-known to those skilled in the art and suitable in the preparation of [N(R
7
)
4
]
+
, [P(N(R
7
)
2
)
k
R
4−k
]
+
, with 0≦k≦4, or [C(N(R
7
)
2
)
3
]
+
cations can be used as aromatic or cycloaliphatic residue A optionally including heteroatoms.
Preferably, A represents a 5- or 6-membered aromatic or cycloaliphatic residue optionally including nitrogen and/or sulfur and/or oxygen atoms, more preferably a phenyl or pyridine residue.
In another preferred embodiment of the present invention, the cation M
n+
is a heteroaromatic cation selected from the group of heteroaromatic cations of general formulas (II) to (IX):
The residues R
1
to R
6
, each of which may be the same or different, represent H, a halogen, preferably fluorine, or a C
1-8
alkyl residue optionally substituted by F, Cl, N(C
a
F
(2a+1−b)
H
b
)
2
, O(C
a
F
(2a+1−b)
H
b
), SO
2
(C
a
F
(2a+1−b)
H
b
), or C
a
F
(2a+1−b)
H
b
substituents wherein 1≦a≦6,and 0≦b≦2a+1.
Likewise, two of the residues R
1
to R
6
together may represent a C
1-8
alkyl residue optionally substituted by F, Cl, N(C
a
F
(2a+1−b)
H
b
)
2
, O(C
a
F
(2a+1−b)
H
b
), SO
2
(C
a
F
(2a+1−b)
H
b
), or C
a
F
(2a+1−b)
H
b
substituents wherein 1≦a≦6, and 0≦b≦2a+1.
Also preferred are tetrakisfluoroalkylborate salts of general formula (I) wherein each of the ligands R are the same, representing (C
x
F
2x+1
), and x=1 or 2. Those tetrakisfluoroalkylborate salts are particularly preferred wherein each of the ligands R are the same, representing a CF
3
residue.
The salts of the invention having the general formula (I) can be used both in pure form and in the form of mixtures thereof as conducting salts in electrolytes, primary and secondary batteries, capacitors, supercapacitors and/or galvanic cells. As conducting salts, it is also possible to use the salts according to the invention in mixture with other lithium salts well-known to those skilled in the art.
They can be used in amounts of between 1 and 99% in combination with other conducting salts that find use in electrochemical cells. For example, conducting salts selected from the group of LiPF
6
, LiBF
4
, LiClO
4
, LiAsF
6
, LiCF
3
SO
3
, LiN(CF
3
SO
2
)
2
, LiC(CF
3
SO
2
)
3
and mixtures of at least two of these compounds are suitable.
The salts of formula (I) and mixtures thereof can also be used in electrolytes for electrochemical cells.
The electrolytes may also include organic isocyanates (DE 100 42 149) to reduce the water content.
Compounds of general formula
[([R
1
(CR
2
R
3
)
k
]
l
A
x
)
y
Kt]
+
(CF
3
)
2
N—
wherein
Kt represents N, P, As, Sb, S, Se,
A represents N, P, P(O), O, S, S(O), SO
2
, As, As(O), Sb, Sb(O),
R
1
, R
2
and R
3
, same or different, represent H, halogen, substituted and/or unsubstituted alkyl C
n
H
2n+1
, substituted and/or unsubstituted alkenyl having 1-18 carbon atoms and one or more double bonds, substituted and/or unsubstituted alkynyl having 1-18 carbon atoms and one or more triple bonds, substituted and/or unsubstituted cycloalkyl C
m
H
2m−1
, mono- or polysubstituted and/or unsubstituted phenyl, substituted and/or unsubstituted heteroaryl,
A may be included at different positions in R
1
, R
2
and/or R
3
,
Kt may be included in cyclic or heterocyclic rings; the groups bound to Kt may be the same or different, with
n
1-18,
m
3-7,
k
0, 1-6,
l
0 or 2 if x = 1, and 1 if x = 0,
x
0, 1,
y
1-4,
may also be included (DE 99 41 566). The method of preparing these compounds is characterized in that an alkali salt of general formula
D
+
(CF
3
)
2
N
−
with D
+

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