Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1995-09-15
1997-11-04
Langel, Wayne
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
423599, C01G 4512, H01M 450
Patent
active
056838352
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method for the preparation of lithium manganese oxide which is used as an intercalation compound in secondary batteries.
A low temperature method for the preparation of lithiated manganese oxide LiMn.sub.2 0.sub.4 is described in U.S. Pat. No. 5,135,732 in which solutions of manganese acetate and hydroxides of lithium and ammonium are reacted in amounts sufficient to yield the stoichiometric phase of LiMn.sub.2 0.sub.4. The reaction is conducted in an inert atmosphere and results in a gelatinous precipitate which is dried to produce a pure LiMn.sub.2 0.sub.4 phase with a small grain size.
An object of the present invention is to provide an improved method for the preparation of lithium manganese oxide, and a method of producing lithium manganese oxide which gives improved performance in secondary batteries.
According to one aspect, the invention consists of adding carbon to a manganese-containing solution prior to reacting said solution with a lithium-containing compound in an inert atmosphere to produce LiMn.sub.2 0.sub.4+x, where 0.ltoreq..times..ltoreq.0.2.
Preferably, the carbon takes the form of powder, such as carbon black, and is present in a proportion up to 8 percent by weight of the LiMn.sub.2 0.sub.4+x produced; preferably, in the range 2 to 6 per cent by weight, with an optimum level of substantially 4 per cent by weight.
A lithium manganese oxide prepared by this method gives improved performance when used in the cathode of a secondary battery, especially in regard to the rate of decline of battery capacity with repeated charge/discharge cycling.
According to a second aspect, the invention consists in reacting a manganese-containing compound with a lithium carbonate to produce LiMn.sub.2 0.sub.4+x, where 0.ltoreq..times..ltoreq.0.2.
Preferably, lithium carbonate Li.sub.2 CO.sub.3 is reacted with manganese acetate (CH.sub.3 CO.sub.2).sub.2 Mn.4H.sub.2 0 to produce the LiMn.sub.2 0.sub.4+x as a precipitate, which is then dried.
Carbon may be added to the solution to improve the performance of the LiMn.sub.2 0.sub.4+x when used in batteries.
This method of preparation does not involve the need for an inert atmosphere, and thus it is easier to implement than the prior art method of U.S. Pat. No. 5,135,732.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a graph showing the variation of the specific discharge capacity of a battery with repeated charge/discharge cycling, the cathode of the battery incorporating LiMn.sub.2 0.sub.4+x which in curve I, is prepared according to a first method of the invention, and in curve II is prepared according to the prior art method of U.S. Pat. No. 5,135,732;
FIG. 2 is a graph showing the variation of the specific discharge capacity of a battery with repeated charge/discharge cycling, the cathode of the battery incorporating LiMn.sub.2 0.sub.4+x prepared according to the first method of the invention but with different proportions by weight of carbon in different samples;
FIG. 3 is a graph showing the variation of the specific discharge capacity of a secondary battery with repeated charge/discharge cycling, the cathode of the battery incorporating LiMn.sub.2 0.sub.4+x which in curve I, is prepared according to a second method of the invention, and in curve II is prepared according to the prior art method of U.S. Pat. No. 5,135,732; and
FIG. 4 is a graph showing the variation of the specific discharge capacity of a secondary battery with repeated charge/discharge cycling, the cathode of the battery incorporating LiMn.sub.2 0.sub.4+x which in curve I, is prepared according to the second method of the invention but without carbon, and in curve II is prepared according to the second method of the invention but with carbon.
In the first method of the invention, 0.3 grams of carbon black was added to 100 milliliters of manganese acetate solution (CH.sub.3 CO.sub.2).sub.2 Mn.4H.sub.2 0 and stirred by bubbling argon through it. A measure o
REFERENCES:
patent: 4828834 (1989-05-01), Nagaura et al.
patent: 5135732 (1992-08-01), Barboux et al.
Langel Wayne
Ultralife Batteries (UK) Limited
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