Organic compounds -- part of the class 532-570 series – Organic compounds – Borate esters
Reexamination Certificate
2000-07-10
2002-08-27
Vollano, Jean F. (Department: 1745)
Organic compounds -- part of the class 532-570 series
Organic compounds
Borate esters
C558S286000
Reexamination Certificate
active
06441216
ABSTRACT:
The invention relates to a method of preparing lithium complex salts and to the use of these in electro-chemical cells.
Lithium ion batteries are amongst the most promising systems for mobile applications, the fields of application extending from sophisticated electronic appliances (e.g. mobile phones, camcorders) to batteries for electrically driven motor vehicles.
These batteries consist of cathode, anode, separator and a nonaqueous electrolyte. The cathodes used are typically Li(MnMe
z
)
2
O
4
, Li (CoMe
z
)O
2
, Li(CoNi
x
Me
z
)O
2
or other lithium intercalation and insertion compounds. Anodes can consist of lithium metal, carbon materials, graphite, graphitic carbon materials or other lithium intercalation and insertion compounds or alloy compounds. The electrolyte used is in the form of solutions comprising lithium salts such as LiPF
6
, LiBF
4
, LiClO
4
, LiAsF
6
, LiCF
3
SO
3
, LiN(CF
3
SO
2
)
2
or LiC(CF
3
SO
2
)
3
and mixtures of these in aprotic solvents.
The standard conducting lithium salts have various drawbacks. Some conducting salts having low cycling yields (e.g. LiBF
4
). Other conducting salts have low thermal stability (e.g. LiPF
6
), and yet other conducting salts are not particularly suitable because of their toxicity and poor environmental safety (e.g. LiAsF
6
).
WO 98/07729 therefore describes a novel class of conducting salts, the lithium borate complexes. These compounds gave particularly good results in cycling trials and proved especially stable. In combination with other salts, these complexes exhibit a synergistic stabilizing effect with respect to oxidation.
A description of lithium bis[5-fluoro-2-olato-benzene-sulfonato(2)-O,O′]borate(1−) reveals a conducting salt which, on the basis of its properties, must be regarded as a very promising conducting salt for use in lithium ion batteries. It does, however, present the problem of the cost-intensive and complicated synthesis of the precursors.
The only previous literature reference (Speier, The Preparation and Properties of (Hydroxyorgano)-silanes and related compounds, J. Am. Chem. Soc. 74 (1952), 1003) on the synthesis of 2-hydroxybenzenesulfonic acids and its derivatives describes this as a laborious three-step procedure with overall yields in the range of between 40 and 70%.
It is therefore a feature of the present invention to provide a simple method for the synthesis of lithium complex salts.
This feature is achieved by a method of preparing lithium complex salts of the general formula
where
R
1
and R
2
are identical or different, are directly linked or not directly linked to one another via a single or double bond, each, individually or jointly, have the meaning of an aromatic ring from the group phenyl, naphthyl, anthracenyl or phenanthrenyl, which can be unsubstituted or mono- to hexasubstituted by alkyl (C
1
to C
6
), alkoxy groups (C
1
to C
6
) or halogen (F, Cl, Br),
or each, individually or jointly, have the meaning of an aromatic heterocyclic ring from the group pyridyl, pyrazyl or pyrimidyl, which can be unsubstituted or mono- to tetrasubstituted by alkyl (C
1
to C
6
), alkoxyl (C
1
to C
6
) or halogen (F, Cl, Br),
or each, individually or jointly, have the meaning of an aromatic ring from the group hydroxybenzene-carboxyl, hydroxynaphthalenecarboxyl, hydroxyben-zenesulfonyl and hydroxynaphthalenesulfonyl, which can be unsubstituted or mono- to tetrasubstituted by alkyl (C
1
to C
6
), alkoxy groups (C
1
to C
6
) or halogen (F, Cl, Br),
R
3
-R
6
can each, individually or pairwise, being directly linked or not directly linked to one another (i.e., are optionally directly linked to an adjacent ring substituent) via a single or double bond, have the following meaning:
1. alkyl (C
1
to C
6
), alkyloxy (C
1
to C
6
) or halogen (F, Cl, Br)
2. an aromatic ring from the groups
phenyl, naphthyl, anthracenyl or phenanthrenyl, which can be unsubstituted or mono- to hexasubstituted by alkyl (C
1
to C
6
), alkoxy groups (C
1
to C
6
) or halogen (F, Cl, Br),
pyridyl, pyrazyl or pyrimidyl, which can be unsubstituted or mono- to tetrasubstituted by alkyl (C
1
to C
6
), alkoxyl (C
1
to C
6
) or halogen (F, Cl, Br), characterized in that
a) 3-, 4-, 5-, 6-substituted phenol (III) in a suitable solvent is admixed with chlorosulfonic acid,
b) the intermediate (IV) from a) is reacted with chlorotrimethylsilane, and the product is filtered and subjected to fractional distillation,
c) the intermediate (II) from b) is reacted with lithiumtetramethanolate borate(1−) in a suitable solvent and the end product (I) is isolated therefrom.
We have found that, starting from 3-, 4-, 5-, 6-substituted phenol (III), it is possible to prepare lithium complex salts in a 3-step synthesis. The starting material is a compound of the general formula:
R
3
-R
6
can each, individually or pairwise, being directly linked or not directly linked to one another via a single or double bond, have the following meaning:
1. alkyl (C
1
to C
6
), alkyloxy (C
1
to C
6
) or halogen (F, Cl, Br)
2. an aromatic ring from the groups
phenyl, naphthyl, anthracenyl or phenanthrenyl, which can be unsubstituted or mono- to hexasubstituted by alkyl (C
1
to C
6
), alkoxy groups (C
1
to C
6
) or halogen (F, Cl, Br),
pyridyl, pyrazyl or pyrimidyl, which can be unsubstituted or mono- to tetrasubstituted by alkyl (C
1
to C
6
), alkoxy groups (C
1
to C
6
) or halogen (F, Cl, Br).
The intermediate of the general formula (II):
where R
1
and R
2
each, individually or jointly, have the following meanings:
R
1
, R
2
: H, alkyl having from 1 to 6 C atoms and trialkylsilyl (containing alkyl C
1
to C
6
),
R
3
-R
6
can each, individually or pairwise, being directly linked or not directly linked to one another via a single or double bond, have the following meaning:
1. alkyl (C
1
to C
6
), alkyloxy (C
1
to C
6
) or halogen (F, Cl, Br)
2. an aromatic ring from the groups
phenyl, naphthyl, anthracenyl or phenanthrenyl, which can be unsubstituted or mono- to hexasubstituted by alkyl (C
1
to C
6
), alkoxy groups (C
1
to C
6
) or halogen (F, Cl, Br),
pyridyl, pyrazyl or pyrimidyl, which can be unsubstituted or mono- to tetrasubstituted by alkyl (C
1
to C
6
), alkoxy groups (C
1
to C
6
) or halogen (F, Cl, Br),
can be synthesized in yields of between 80 and 90%.
The end product of the general formula (I) can be used in electrolytes of lithium batteries, either on its own on in combination with other lithium salts and/or borate complexes. In so doing it is important to make sure that the level of sodium-containing impurities is very low. Given the electrochemical properties (sodium is baser than lithium), sodium ions would otherwise be inserted into the structure of the negative electrodes. Ultimately this results in failure of the battery. The method according to the invention can dispense with the use of sodium.
Consequently, the lithium borate complexes prepared according to the invention are suitable in particular for use in electrochemical cells. The lithium borate complexes can be used, together with other lithium salts or alternatively with borate complexes, in electrolytes for secondary lithium batteries.
Alternatively, the lithium borate complexes can also be used in electrolytes comprising conventional conducting salts. Suitable, for example, are electrolytes comprising conducting salts selected from the group LiPF
6
, LiBF
4
, LiClO
4
, LiAsF
6
, LiCF
3
SO
3
, LiN(CF
3
SO
2
)
2
or LiC(CF
3
SO
2
)
3
and mixtures of these. The electrolytes may also comprise organic isocyanates (DE 199 44 603) to reduce the water content. Equally, the electrolytes can comprise organic alkali metal salts (DE 199 10 968) as an additive. A suitable example is that of alkali metal borates of the general formula
Li
+
B
−
(OR
1
)
m
(OR
2
)
p
where
m and p are 0, 1, 2, 3 or 4, with m+p=4, and R
1
and R
2
are identical or different,
are linked or not linked directly to one another via a single or double bond,
each, individually or jointly, have the meaning of an aromatic or aliphatic carboxylic, di
de Meijere Armin
Leonov Andrei
Schmidt Michael
Merck Patent Gesellschaft mit beschraenkter Haftung
Vollano Jean F.
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