Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Reexamination Certificate
2000-11-10
2003-05-27
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
C429S326000, C429S213000, C029S623100
Reexamination Certificate
active
06569573
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to the field of electrochemical cells. More particularly, this invention pertains to lithium batteries in which the cathode comprises an electroactive sulfur-containing material and the electrolyte comprises reactive components that enhance the capacity of the lithium battery.
BACKGROUND
Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
As the evolution of batteries continues, and particularly as lithium batteries become more widely accepted for a variety of uses, the need for safe, long lasting high energy batteries becomes more important. There has been considerable interest in recent years in developing high energy density cathode-active materials for use in high energy primary and secondary batteries with lithium containing anodes. Various types of cathode materials for the manufacture of lithium batteries are known in the art.
One class of lithium batteries known in the art are rechargeable lithium batteries where the battery is able to undergo multiple discharge and recharge cycles. During discharge of a lithium cell, lithium ions are formed and extracted from the anode and inserted into the cathode. On recharge, the reverse process occurs. The electrodes used in these batteries can have a dramatic effect on the performance of the battery and, in particular, on cycle life.
Another class of lithium batteries known in the art are primary lithium batteries. A primary battery differs from a rechargeable battery in that it is only designed to be discharged once. In fact, because of the design, attempts to recharge a primary battery may create safety problems and may be only partially effective for a very limited number of cycles. Examples of lithium primary cells are described by Nishio et al. in
Handbook of Battery Materials
, Chapter 2, “Practical Batteries”, pp. 31-40, Elsevier, Amsterdam, (1999) and by Linden in
Handbook of Batteries
, Chapter 14, pp. 5-6, McGraw-Hill, N.Y. (1995). Primary, non-rechargeable cells, with their single discharge, have a short lifetime and their disposal burden is high, which makes the choice of the cathode material and its impact on the environment of great importance. Sulfur is an attractive cathode-active material for primary cells, both from an environmental perspective and from its very high theoretical specific capacity of 1675 mAh/g in the lithium-sulfur couple.
U.S. Pat. No. 4,410,609 to Peled et al. describes a primary cell comprising an anode consisting of lithium or a dischargeable alloy of lithium, an electrolyte comprising a solvent to dissolve both an electrolyte salt and polysulfides at a low concentration, and an inert porous cathode current collector, which may be loaded with sulfur. Yamin et al., in
Electrochemical Society Proceedings
, 1984, Volume 84-1, 301-310, describe low rate lithium/sulfur batteries in which the primary cells have a porous carbon cathode current collector impregnated with sulfur and in which the cell's electrolyte is a lithium polysulfide saturated solution of 1M LiClO
4
in tetrahydrofuran-toluene mixtures. The room temperature energy density for these cells is reported to be 730 Wh/Kg.
In a study of dioxolane-based solvents for lithium-sulfur batteries, Peled et al., in
J. Electrochem. Soc
., 1989, 136, 1621-1625, report that dioxolane-rich solvents are compatible with lithium but that sulfur utilization is only 50% due to the final reduction (discharge) product, Li
2
S
2
.
There is a need to enhance the performance of primary and rechargeable lithium electrochemical cells. In studies on lithium/thionyl chloride cells, performance enhancement has been achieved by the addition of halide additives. For example, Linden, in
Handbook of Batteries
, Chapter 14, pp. 44-47, McGraw-Hill, New York (1995), summarizes data showing an increase in cell voltage and energy density by the addition of BrCl to lithium/thionyl chloride cells. In U.S. Pat. Nos. 4,784,925 and 4,784,927 to Klinedinst et al., small quantities of iodine or iodine monochloride are reported to act as catalysts to increase output voltage and output capacity of lithium/thionyl chloride cells.
Sodium-sulfur cells, which typically operate at high temperatures, such as 300° C. to 350° C., also typically operate at a capacity less than theoretical to avoid precipitation of insoluble Na
2
S and Na
2
S
2
. U.S. Pat. No. 4,018,969 to Fisher et al., and U.S. Pat. Nos. 4,184,013, 4,216,276, and 4,238,553 to Weddigen et al. describe additives which increase the solubility of Na
2
S and Na
2
S
2
in the liquid sulfur cathode and thereby increase the capacity of high temperature sodium-sulfur cells.
Despite the various approaches proposed for the fabrication of lithium cells, there remains a need for higher energy density and safer and more environmentally acceptable primary and rechargeable lithium cells.
It is, therefore, an object of the present invention to provide lithium cells which have higher energy density.
It is another object of the present invention to provide cells which are safe and which comprise environmentally acceptable materials.
SUMMARY OF THE INVENTION
The present invention pertains to a lithium electrochemical cell comprising: (a) a solid lithium anode; (b) a solid cathode comprising an electroactive sulfur-containing material; and (c) a non-aqueous electrolyte interposed between the solid anode and the solid cathode, which electrolyte comprises: (i) one or more lithium salts; (ii) one or more non-aqueous solvents; and (iii) one or more capacity-enhancing reactive components.
In one embodiment, the one or more capacity-enhancing reactive components comprise an anion receptor. In one embodiment, the one or more capacity-enhancing reactive components comprise an electron transfer mediator.
In one embodiment, the anion receptor comprises a polyalkyleneamine compound of the formula (—N(R)—CH
2
—CH
2
—)
q
, where q is an integer equal to or greater than 2, and R is a substituent selected from the group consisting of CF
3
SO
2
, CF
3
CO, CN, SO
2
CN, and (—CH
2
—CH
2
—N(R
1
)—)
p
, where R
1
is selected from the group consisting of H, CF
3
SO
2
, CF
3
CO, CN, and SO
2
CN, and p is an integer from 1 to 4.
In one embodiment, the anion receptor is a boron moiety, BX
3
, where X, is the same or different at each occurrence and is an electron withdrawing moiety selected from the group consisting of F, perfluoroalkyl, CF
2
═CF—, pentafluorophenyl, 3,4,5-trifluorophenyl, CF
3
SO
2
, N(CF
3
SO
2
)
2
, C(CF
3
SO
2
)
3
, and
where R
2
is the same or different at each occurrence and is selected from the group consisting of H, F, CF
3
, COCF
3
, SO
2
CF
3
, and SO
2
F.
In one embodiment, the anion receptor is present in the amount of 0.2% to 25% by weight of the electrolyte. In one embodiment, the anion receptor is present in the amount of 0.5% to 10% by weight of the electrolyte.
In one embodiment, the capacity-enhancing reactive component comprises components of formula:
wherein:
R
4
is the same or different at each occurrence and is selected from the group consisting of H, alkyl, alkenyl, aryl, or substituted derivatives thereof;
E is the same or different at each occurrence and is selected from the group consisting of O, NR
5
, and S, where R
5
is alkyl, aryl, or substituted derivatives thereof;
a is an integer from 0 to 1; and
r is an integer from 2 to 5.
In one embodiment, the electron transfer mediator is of the formula:
wherein:
Z is the same or different at each occurrence and is selected from the group consisting of O, S, Se, and NR
5
, where R
5
is alkyl, aryl, or substituted derivatives thereof;
R is the same or different at each occurrence, is selected from the group consisting of alkyl, aryl, F, Cl, CF
3
, CF
3
SO
2
, and N
Mikhaylik Yuriy V.
Skotheim Terje A.
Trofimov Boris A.
Kalafut Stephen
Moltech Corporation
Nicol Jacqueline M.
Squire, Sander & Dempsey L.L.P.
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