Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-09-29
2001-06-19
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S231100, C429S231400, C429S231800, C429S231950, C429S324000, C429S340000, C429S341000, C423S592100, C423S595000
Reexamination Certificate
active
06248477
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to intercalation compositions for use as active cathode ingredients in rechargeable lithium batteries, and more particularly, to lithium manganese oxide spinel modified with one or more other metals, its preparation and use.
DESCRIPTION OF THE PRIOR ART
Lithium cobalt oxide has heretofore been utilized as the positive electrode material in commercial four volt rechargeable lithium batteries. Because of their lower cost, environmental friendliness, ease of production and equivalent performance, lithium manganese oxide intercalation compositions have been considered for use as cathode active materials in rechargeable lithium and lithium-ion batteries. The term “intercalation” indicates the ability of the composition to reversibly accommodate guest ions, typically alkali metal ions. A problem that has been encountered in the use of lithium manganese oxide intercalation compositions in batteries has been less than satisfactory performance, especially capacity fade which has been deemed unsatisfactory for today's stringent requirements. The term “capacity” as used herein means the initial discharge capacity of a cathode active material utilized in a rechargeable lithium battery. The term “capacity fade” or “cycle fade” is used herein to mean the decrease in capacity with each cycle, i.e., with each recharge and discharge.
It was established by Gummow et al. [Solid State Ionics 69, 59 (1994)] that stoichiometric LiMn
2
O
4
is an unsuitable cathode ingredient due to its chemical and physical degradation resulting in rapid capacity fade. Thackeray et al. [U.S. Pat. No. 5,316,877 issued May 31, 1994] taught that materials of the formula Li
1
D
x/b
Mn
2−x
O
4+&dgr;
(wherein x is less than 0.33, D is a mono-or multi-valent metal cation, b is the oxidation state of D and &dgr; is the fraction required to produce electroneutrality of the compound) would have enhanced stability but reduced discharge capacity. This deficiency in discharge capacity is noted in most subsequent papers or patents describing doped or modified lithium manganese oxide spinels.
Recent publications which define the preparation and performance of multivalent metal cation (M) doped lithium manganese oxide cathode materials include de Kock et al. [J. Power Sources 70, 247 (1998)], Iwata et al. [E.P. No. 885,845 (Dec. 23, 1998)], Heider et al. [W.O. 99/00329 (Jan. 7, 1999)], Pistoia et al. [W.O. 97/37394 (Oct. 9, 1997)] and Miyasaka [U.S. Pat. No. 5,869,208 issued on Feb. 9, 1999]. Preparations which are representative of those described in the above publications require an intimate mixing, usually by ball milling, of the reaction precursers, followed by an extended reaction at temperatures up to 900° C., generally with multiple calcining and grinding steps. The objective of the multiple calcining and grinding steps is to insure a complete reaction with no detectible by-products such as M oxides, Mn
2
O
3
or Li
2
MnO
3
in the spinel product. The by-product impurities are believed to reduce reversible capacity and contribute to the destabilization of the working battery system. An alternate method [Hemmer et al., W.O. 96/10538 (Apr. 11, 1996)] requires the dissolution and mixing of precurser metal salts which results in mixing at the atomic level. The solvent is subsequently removed prior to thermal treatment.
The theoretical initial discharge capacity of lithium manganese oxide (LiMn
2
O
4
) is 148 mAh/g, but the lattice disorders formed during calcining restrict the availability of intercalation channels, and as a result, initial discharge capacities rarely exceed 130 mAh/g. Unacceptable capacity fade, i.e., fade rates of up to 0.5% per cycle at room temperature, are also characteristic. Excess lithium in the spinel as taught by Thackeray et al. [U.S. Pat. No. 5,316,877 issued May 31, 1994], reduces the capacity fade rate, but it also reduces the capacity. Since lithium (as Li
2
O) is an excellent flux, the additional lithium serves to facilitate the reaction by enhancing reactant cation mobility, thus facilitating the formation of intercalation channels, and capacities closer to theoretical are obtained. Wada et al., [U.S. Pat. No. 5,866,279 issued Feb. 2, 1999] teach that lithium manganese oxide with 3.2 mole % extra lithium will produce 121 mAh/g (122 mAh/g calculated) with only 0.025%/cycle fade.
When a second metal ion modifier (other than lithium) is added to the spinel lattice, a further reduction in capacity is observed, although stability may be enhanced. For example, Li
1.06
Cr
0.1
Mn
1.84
O
4
is listed with 108 mAh/g initial capacity (114 mAh/g calculated) and 0.025%/cycle fade [Iwata et al., E.P. 885,845 (Dec. 23, 1998)], but Li
1.02
M
0.05
Mn
1.93
O
4
materials have approximately 0.3%/cycle fade without a protective coating [Miyasaka [U.S. Pat. No. 5,869,208 issued on Feb. 9, 1999]. Phase-pure Li
1.01
Al
0.01
Mn
1.98
O
4
described by de Kock et al. [J. Power Sources 70, 247 (1998)] produced only 103 mAh/g (146 mAh/g calculated), but had less than 0.03%/cycle capacity fade. The same is true for multiple dopants, i.e., low capacity with low cycle fade, as described in Faulkner et al., [W.O. 98/38648 (Sep. 3, 1998)]. Secondary rechargeable lithium batteries have a broad application in the automotive and other similar industries where the batteries must withstand operations and storage at temperatures up to 65° C. The various publications cited above do not mention whether or not the cathode active materials described are thermally stable, i.e., capable of operating or being stored in the 40° C. to 65° C. range without quickly losing the stated performance characteristics.
Thus, there are continuing needs for improved lithium manganese oxide intercalation materials which can serve as active cathode ingredients in secondary rechargeable lithium or lithium ion batteries having high initial capacities and low cycle fades while operating or being stored at temperatures up to about 65° C.
SUMMARY OF THE INVENTION
The present invention provides metal cation-modified lithium manganese oxide cathode intercalation compositions, methods of preparing the compositions and secondary rechargeable lithium or lithium-ion batteries containing the compositions as active cathode ingredients which meet the needs described above and overcome the above mentioned deficiencies of the prior art. The cathode intercalation compositions of this invention are basically comprised of a trivalent metal cation-modified lithium manganese oxide composition having a spinel structure and having the general formula Li
1+x
M
y
Mn
2−x−y
O
4
with crystallites of M
2
O
3
dispersed throughout the structure wherein x is a number greater than 0 but less than or equal to 0.25, M is one or more trivalent metal cations, y is a number greater than 0 but less than or equal to 0.5 and a portion of M is in the crystallites of M
2
O
3
. The trivalent metals which can be utilized in the intercalation compositions of this invention include one or more of aluminum, chromium, gallium, indium and scandium.
The methods of preparing the above described lithium manganese oxide intercalation compositions of the above formula are basically comprised of intimately mixing particulate solid reactants comprised of lithium, manganese and one or more of the above described trivalent metals in the form of oxides, thermally decomposable salts or mixtures thereof in amounts based on the above formula. The resulting intimately mixed reactants are introduced into a reactor, and the mixed reactants are heated in the reactor, preferably while continuously being agitated, in the presence of air or an oxygen enriched atmosphere at a temperature in the range of from about 550° C. to about 850° C. for a time period of up to about 48 hours. Thereafter, the reacted product formed is gradually cooled to a temperature of less than about 500° C.
The improved second
Bledsoe Joe Lane
Howard, Jr. Wilmont Frederick
Jordan Monte Sean
Sheargold Stephen Wilfred
Dougherty, Jr. C. Clark
Kerr-McGee Chemical LLC
Weiner Laura
LandOfFree
Cathode intercalation compositions, production methods and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cathode intercalation compositions, production methods and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cathode intercalation compositions, production methods and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2528905