Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-04-15
2001-05-29
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S220000, C429S221000, C429S223000, C429S224000, C429S231100, C429S231200, C429S231300
Reexamination Certificate
active
06238821
ABSTRACT:
TECHNICAL FIELD
The present invention pertains generally to the field of cathodes and rechargeable electric current producing cells. More particularly, the present invention pertains to composite cathodes which comprise (a) an electroactive sulfur-containing cathode material, wherein said electroactive sulfur-containing cathode material, in its oxidized state, comprises a polysulfide moiety of the formula —S
m
—, wherein m is an integer equal to or greater than 3; and, (b) an electroactive transition metal chalcogenide composition, which encapsulates said electroactive sulfur-containing cathode material, and which retards the transport of anionic reduction products of said electroactive sulfur-containing cathode material. The present invention also pertains to methods of making such composite cathodes, cells comprising such composite cathodes, and methods of making such cells.
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 and alkali-metals as anode materials for high energy primary and secondary batteries. Several types of cathode materials for the manufacture of thin film lithium and sodium batteries are known in the art. The most widely investigated group are metallic or inorganic materials which include transition metal chalcogenides, such as titanium disulfide with alkali-metals as the anode as described in U.S. Pat. No. 4,009,052. Also among the cathode active chalcogenides, U.S. Pat. No. 4,049,879 lists transition metal phosphorous chalcogenides, and U.S. Pat. No. 3,992,222 describes cells using mixtures of FeS
2
and various metal sulfides as the electroactive cathode materials. U.S. Pat. No. 3,639,174 describes primary and secondary voltaic cells utilizing lithium aluminum alloy anodes and a reversible cathode depolarizer such as cupric sulfide, cuprous oxide, cupric carbonate, and the like that have low solubility in the electrolyte. U.S. Pat. No. 4,576,697 describes electroactive cathode materials in alkali-metal non-aqueous secondary batteries comprised of carbon-containing intercalatable layered or lamellar transition metal chalcogenides having the general formula M
n
X
2
C, wherein M is a transition metal selected from the group consisting of Ti, V, Cr, Fe, Zr, and Ta; X is sulfur; and n is 1-2. High energy density solid state cells comprising cathodes using selected ionically and electronically conductive transition metal chalcogenides in combination with other non-conductive electroactive cathode materials are described in U.S. Pat. No. 4,258,109.
Another type of cathode materials disclosed for use in lithium and sodium batteries are organic materials such as conductive polymers. A further type of organic type cathode materials are those comprised of elemental sulfur, organo-sulfur and carbon-sulfur compositions where high energy density is achieved from the reversible electrochemistry of the sulfur moiety with the alkali metal. U.S. Pat. No. 4,143,214 to Chang et al. describes cells having cathodes containing C
v
S wherein v is a numerical value from about 4 to about 50. U.S. Pat. No. 4,152,491 to Chang et al. relates to electric current producing cells where the cathode-active materials include one or more polymer compounds having a plurality of carbon monosulfide units. The carbon monosulfide unit is generally described as (CS)
w
, wherein w is an integer of at least 5, and may be at least 50, and is preferably at least 100.
U.S. Pat. No. 4,664,991 to Perichaud et al. describes an organo-sulfur material containing a one-dimensional electric conducting polymer and at least one polysulfurated chain forming a charge-transfer complex with the polymer. Perichaud et al. use a material which has two components. One is the conducting or conductive polymer, which is selected from a group consisting of polyacetylenes, polyparaphenylenes, polythiophenes, polypyrroles, polyanilines and their substituted derivatives. The other is a polysulfurated chain which is in a charge transfer relation to the conducting polymer. The polysulfurated chain is formed by high temperature heating of sulfur with the conductive polymer to form appended chains of . . . —S—S—S—S— . . . of indeterminate length.
In a related approach, a PCT application (PCT/FR84/00202) of Armand et al. describes derivatives of polyacetylene-co-polysulfurs comprising units of Z
q
(CS
r
)
n
wherein Z is hydrogen, alkali-metal, or transition metal, q has values ranging from 0 to values equal to the valence of the metal ion used, values for r range from greater than 0 to less than or equal to 1, and n is unspecified. These derivatives are made from the reduction of polytetrafluoroethylene or polytrifluorochloroethylene with alkali-metals in the presence of sulfur, or by the sulfuration of polyacetylene with vapors of sulfur monochloride at 220° C.
U.S. Pat. No. 5,441,831 relates to an electric current producing cell which comprises a cathode containing one or more carbon-sulfur compounds of the formula (CS
x
)
n
, in which x takes values from 1.2 to 2.3 and n is equal to or greater than 2.
U.S. Pat. Nos. 4,833,048 and 4,917,974 to De Jonghe et al. describe a class of cathode materials made of organo-sulfur compounds of the formula (R(S)
y
)
n
, where y=1 to 6; n=2 to 20, and R is one or more different aliphatic or aromatic organic moieties having one to twenty carbon atoms. One or more oxygen, sulfur, nitrogen or fluorine atoms associated with the chain can also be included when R is an aliphatic chain. The aliphatic chain may be linear or branched, saturated or unsaturated. The aliphatic chain or the aromatic rings may have substituent groups. The preferred form of the cathode material is a simple dimer or (RS)
2
. When the organic moiety R is a straight or a branched aliphatic chain, such moieties as alkyl, alkenyl, alkynyl, alkoxyalkyl, alkythioalkyl, or aminoalkyl groups and their fluorine derivatives may be included. When the organic moiety comprises an aromatic group, the group may comprise an aryl, arylalkyl or alkylaryl group, including fluorine substituted derivatives, and the ring may also contain one or more nitrogen, sulfur, or oxygen heteroatoms as well.
In the cell developed by De Jonghe et al. the main cathode reaction during discharge of the battery is the breaking and reforming of disulfide bonds. The breaking of a disulfide bond is associated with the formation of an RS
−
M
+
ionic complex. The organo-sulfur materials investigated by De Jonghe et al. undergo polymerization (dimerization) and de-polymerization (disulfide cleavage) upon the formation and breaking of the disulfide bonds. The de-polymerization which occurs during the discharging of the cell results in lower molecular weight polymeric and monomeric species, namely soluble anionic organic sulfides, which can dissolve into the electrolyte and cause self-discharge as well as reduced capacity, thereby severely reducing the utility of the organo-sulfur material as cathode-active material and eventually leading to complete cell failure. The result is an unsatisfactory cycle life having a maximum of about 200 deep discharge-charge cycles, more typically less than 100 cycles as described in
J. Electrochem. Soc
., Vol. 138, pp. 1891-1895 (1991).
A significant drawback with cells containing cathodes comprising elemental sulfur, organosulfur and carbon-sulfur materials relates to the dissolution and excessive out-diffusion of soluble sulfides, polysulfi
Mukherjee Shyama P.
Skotheim Terje A.
Kalafut Stephen
Moltech Corporation
Morrison & Foerster / LLP
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