Electrode materials derived from polyquinonic ionic...

Details Electrode materials derived from polyquinonic ionic... Electrode materials derived from polyquinonic ionic...

1999-07-28

2004-06-01

Choi, Ling-Siu (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S256000, C526S259000, C429S209000

Reexamination Certificate

active

06743877

ABSTRACT:

FIELD OF THE INVENTION
The present invention is concerned with novel polyquinonic ionic compounds useful as electrode materials used for example in electrochemical generators.
BACKGROUND OF THE INVENTION
Electrode materials derived from transition metals, in particular transition metals binary chalcogenides, such as TiS
2
, VO
x
(2≦x≦2,5), ternary oxides such as LiNiO
2
LiCoO
2
, Li
1+x
Mn
2−x
O
4
(0≦x≦1), et LiV
3
O
8
, are known. These materials are however often relatively toxic. With the exception of vanadium derivatives, the capacities are practically modest, i.e. on the order of 100 Ah.g
−1
, and their potential (about 4 V vs Li
+
/Li
o
) are beyond the domain of stability of solid or liquid electrolytes. They are therefore problematic in terms of safety.
Organic compounds like conjugated polymers work through an insertion mechanism of anions taken from the electrolyte. The mass capacities resulting therefrom are consequently low and the cycling possibilities are disappointing.
Other known compounds are those of the polydisulfide type, which, even if they do not have intrinsic electronic conductivity, possess interesting redox properties and mass capacities ((≧300 Ah.g
−1
), particularly oxidizing coupling derivatives of 2,5-dimercaptothiadiazole. However, the resulting reduction products and intermediates are lithium salts like conjugated thiolates with a nitrogen atom. Delocalization of the charge on the polarisable anionic centers like sulfur and nitrogen, lead to a relatively important solubility in the electrolytes, as well as a reduced cycling life span.
Monoquinones are organic compounds known for their redox properties, but the potentials are of little interest (on the order of 2.2 V vs. Li
+
/Li
o
), and the neutral oxidized compounds are soluble in the electrolytes. Polymers bearing quinonic functions such as those resulting from hydroquinone and formaldehyde polycondensation, are not electrochemically active because of the reduced mobility of the charge carriers, ions and electrons, in the absence of highly polar protic solvents like water.
SUMMARY OF THE INVENTION
The present invention concerns electroactive compounds derived from anion salts bearing at least 2 quinone functions cumulated, conjugated, or both, in the same molecule. More specifically, the invention comprises a redox compound having at least one state of oxidation state represented by the general formula:
wherein
M
+
represents an alkaline metallic cation, an alkaline-earth cation, a transition metal cation, a rare earth cation, an organometallic cation, an organic cation of the “nium” type, a repetitive unit of a cationic oxidized conjugated polymer, or a monomeric or polymeric cation optionally having a redox character;
X is oxygen, NCN, or C(CN)
2
;
Z is C—Y
−
or N
−
;
Y represents oxygen, sulfur, NCN, —C(CN)
2
, with the proviso that when Y is sulfur and n is ≦4, then X is oxygen;
R
1
is absent, O, S, NH, —(C═C)
r
—, —(W═W)
r
— wherein W is independently CR
6
or N; r varies between 1 and 12; and R
6
is H, halogen, CN, or C
1-12
alkyl, C
2-12
alkenyl or C
6-14
aryl optionally having one or more substituents oxa, aza or thia; and wherein 2 R
6
groups can be bonded to form a cycle comprising from 3 to 7 members;
R
2
and R
3
are the same or different and are absent, a carbonated divalent radical, optionally substituted with aza, oxa or thia;
q varies between 0 et p;
p varies between 1 and 5;
n varies between 1 and 10
4
; and
wherein two of R
1
, R
2
and R
3
can be bonded together to form a cycle comprising 3 to 7 members.
For the purposes of the present invention, when n is 4 or less, the compound of the invention is not considered a polymer. In addition, the expression “divalent radical” is defined as an alkylene, an arylene, or an arylalkylene of from 2 to 200 carbon atoms, and optionally comprising one or more substituents aza, oxa or thia.
The present application further concerns an electrode material characterized in that it contains, in whole or in part, a compound of the invention, and an electrical energy storage system such as a primary or secondary generator or a super capacity comprising an electrolyte, at least one negative electrode and at least one positive electrode comprising a compound of the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a new family of electroactive compounds derived from anion salts bearing a plurality of quinone functions cumulated and/or conjugated in the same molecule is described and claimed. It has been found that such type of compounds have a high capacity, i.e. equal or higher than 300 Ah.g
−1
, obtained at potentials comprised between 3.5 et 1 V vs. Li
+
/Li
o
, thus in the domain of stability of conventional aprotic electrolytes, liquid or solid, and allowing the making of positive and negative electrodes for generators. Further, the corresponding salts do not, whatever their degree of oxidation, solubilize significantly in liquid electrolytes or aprotic polymers. The kinetic of theredox reaction in solid phase is noticeable and comparable to that of inorganic insertion materials. It has also been found that by replacing the oxygen atom of the neutral quinonic groups CO with NCN groups or C(CN)
2
, and/or the replacement of the oxygen atom of the quinonic groups negatively charged with anionic groups N
−
, NCN
−
or C(CN)
2
−
had the same interesting properties in terms of the redox activity. The redox potential is displaced of about 300 mV towards the positive values by replacing a neutral quinonic oxygen with an NCN or C(CN)
2
. The chemical methods to perform these substitutions on the quinonic groups are well known to anyone of ordinary skill in the art.
The redox compounds of the present invention include also polyquinones wherein the negatively charged oxygen of the quinonic groups is replaced with sulfur S
−
. In this case, charge conjugation with an oxygenated group CO neutral and weakly polarisable and more electronegative, significantly lowers the solubility of the corresponding ionic derivatives, in particular in electrolytic solutions. An additional degree of oxidation is then obtained by oxidative duplication of CS
−
groups to form disulfide bridges CS—SC.
These polyquinonic compounds can also be part of the polymers into which the charges are conjugated along the polymeric chain. In such a case, the solubility of these rigid macromolecules is null, whatever the charge borne by the polymer, thus including the neutral state.
Because the compounds of the present invention are anion salts, i.e., negatively charged, it is necessary to combine them with a cation in order to have a global neutral charge. The preferred cations comprise the proton, alkaline cations like Li, Na, K, Cs; alkaline-earth cations like Mg, Ca, Ba; transition metal cations like Cu, Zn, Pb, Fe, Ni, Co, Mn, V, Cr; rare earth cations; organometallic cations like metallocenium; cations of the <<ium>> type such as ammonium, amidinium, guanidinium, pyridinium, imidazolium, triazolium, imidazolinium, sulfonium, phosphonium, iodinium; a repetitive unit of an oxidized cationic conjugated polymer such as polypyrrole, polythiophene, polyquinolines; cations in the form of monomers or polymers optionally having a redox character such as viologenes of formula [—(R″NC
5
H
4
—C
5
H
4
N—)
2+
]
n
wherein R″ comprises C
2-12
alkylene, C
6-14
arylene or C
6-14
arylene C
2-12
alkylene, each optionally substituted with oxa, aza ou thia. The lithium cation and the proton are particularly preferred. Other ions can be present in the electrolytic medium and/or in the electrode material, and can contribute to improve the conductivity of the interfacial properties. The potassium ion is advantageously used in such instance, as well as cations derived from quatemized imidazoliumn.
To the redox capacity of the molecules of the present invention can be added that of the cation when the latter p

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