Battery electrolytes and batteries

Details Battery electrolytes and batteries Battery electrolytes and batteries

1998-12-10

2001-01-02

Nuzzolillo, Maria (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

C429S323000, C429S326000

Utility Patent

active

06168889

ABSTRACT:

TECHNICAL FIELD
The invention pertains to batteries and battery electrolyte.
BACKGROUND OF THE INVENTION
Small, thin lithium-anode batteries, such as button-type batteries, are commonly used in modern devices. For instance, button-type batteries are utilized as power sources for calculators and watches. Button batteries can be extremely thin (for example, button-batteries are sometimes produced to thickness of less than or equal to about 1 millimeter). A difficulty in forming batteries having thickness of 1 millimeter or less can be in maintaining good electrical transfer between the thin anode and the thin cathode of the battery. It can therefore be desired to develop new electrolyte compositions.
A prior art button-type battery
10
is shown in the FIGURE. Battery
10
comprises a lower terminal housing member, or can
12
, and an upper terminal housing member, or lid
14
. Can
12
and lid
14
are sealingly joined together at a crimp
16
. Battery
10
is typically in the shape of a circle, with crimp
16
extending entirely around a periphery of the circle. A gasket material
18
is provided within crimp
16
to form a fluid-tight seal within the crimp. A cathode
20
and an anode
22
are provided between terminal housing members
12
and
14
. Cathode
20
and anode
22
are separated by a porous separator
24
. An electrolyte
26
is provided within the battery and within porous separator
24
.
Battery anode
22
typically comprises lithium, and battery cathode
20
typically comprises a mixture of an active material and a conductive medium, or diluent. The active material can be, for example at least one of manganese dioxide and (CF)
x
. The manganese dioxide provides a source of oxidizing component in a battery cell. As manganese dioxide is itself a poor conductor, the conductive medium is added to provide electrical conductivity. The conductive medium can be, for example, elemental carbon. The elemental carbon is typically in the form of graphite, although other materials, such as, acetylene black can also be used. Natural graphites can be used in alkaline cells, but typically cells are made with very pure synthetic graphite to reduce impurities which might lead to corrosion in a battery cell.
The choice of electrolyte for lithium batteries is “critical”, (D. Linden,
Handbook of Batteries
, (1995) McGraw-Hill, Inc. at p. 36.13). The electrolyte should have characteristics of (1) ionic conductivity of greater than 10
−3
S/cm at from −40° C. to 90° C. to minimize internal resistance, (2) a lithium ion transference number approaching unity to limit concentration polarization, (3) a wide electrochemical voltage window of from 0 volts to 5 volts, (4) thermal stability up to 90° C., and (5) compatibility with other cell components.
It can be extremely difficult to develop good electrolytes for lithium batteries. Electrolyte chemistry is highly unpredictable, with electrolyte mixtures of similar composition have markedly different electrolytic properties. The search for good electrolytes is thus a tedious process wherein even minor adjustments to composition can constitute critical changes having significant impact on electrolytic properties. In spite of the difficulty of finding good electrolytes, the importance of electrolyte chemistry to battery life and performance requires that the search continue for additional good electrolytes. It would therefore be desirable to develop additional electrolytes for lithium batteries.
SUMMARY OF THE INVENTION
The invention encompasses battery electrolytes and batteries.
In one aspect, the invention encompasses a battery electrolyte which includes lithium salts comprising at least two salts selected from the group consisting of LiN(CF
3
SO
2
)
2
, LiAsF
6
, LiBF
4
, LiPF
6
and LiCF
3
SO
3
in a solvent blend comprising ethylene carbonate, propylene carbonate, and 1,2-dimethoxyethane.
In another aspect, the invention encompasses a battery. The battery includes a first electrode, a second electrode, and an electrolyte between the first and second electrodes. The electrolyte comprises lithium salts in a solvent blend comprising ethylene carbonate, propylene carbonate, and 1,2-dimethoxyethane. The lithium salts comprise at least two salts selected from the group consisting of LiN(CF
3
SO
2
)
2
, LiAsF
6
, LiBF
4
, LiPF
6
and LiCF
3
SO
3
.
In yet another aspect, the invention encompasses another embodiment of a battery. The battery includes a cathode comprising at least one of MnO
2
and (CF)
x
, and an anode comprising lithium. The battery further includes a non-aqueous electrolyte between the cathode and the anode. The non-aqueous electrolyte comprises lithium salts in a solvent blend comprising ethylene carbonate, propylene carbonate, and 1,2-dimethoxyethane. The lithium salts comprise at least two salts selected from the group consisting of LiN(CF
3
SO
2
)
2
, LiAsF
6
, LiBF
4
, LiPF
6
and LiCF
3
SO
3
.


REFERENCES:
patent: 5272022 (1993-12-01), Takami
patent: 5639577 (1997-06-01), Takeuchi
patent: 6017656 (1993-12-01), Crespi
patent: 6025069 (2000-02-01), Hope
Linden, D., “Handbook of Batteries”, Second Ed., pp. 36.13-36.16, No date available.

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