Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1997-02-14
1999-09-07
Nuzzolillo, Maria
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
4292311, 423 49, H01M 450
Patent
active
059485655
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a spinel lithium manganese oxide based cathode material for lithium secondary batteries and a process and a precursor material for the production.
The use of spinel Li.sub.1+x Mn.sub.2 O.sub.4 cathode material in lithium secondary batteries is well known in the art and e.g. described in Thackeray et al.: "Lithium Insertion Into Manganese Spinels", Mat. Res. Bull., 18, pp. 461-472 (1983).
Spinel Li.sub.1+x Mn.sub.2 O.sub.4 has proven to be a highly suited material for the construction of cathodes for high voltage lithium secondary batteries. There exists, however, still a need for an improvement of the lithium chemical diffusion coefficient of such materials.
It is an object of the present invention to provide a cathode material for lithium secondary batteries which exhibits a higher lithium chemical diffusion coefficient than otherwise obtained for pure spinel Li.sub.1+x Mn.sub.2 O.sub.4.
This object is accomplished by a cathode material for lithium secondary batteries containing as active ingredient Li.sub.y Mn.sub.2-z M.sub.z O.sub.4 in which M is selected from the group consisting of Co, Ni, Ti, V, Fe, in which y is in the range from 0 to 1.5, preferably 1 to 1.5, and in which z is in the range from 0 to 1 and furthermore comprising 1 to 50% by mole of the inactive cathode material .alpha.-Mn.sub.2 O.sub.3 and/or Li.sub.2 MnO.sub.3.
In the present context the expression "active ingredient" refers to a material that, when used as a cathode material in a battery, is capable of being oxidized and reduced in a reversible manner during charge and discharge of the battery. The expression "inactive cathode material" refers to any other material than the active ingredients defined above.
The content of .alpha.-Mn.sub.2 O.sub.3 and/or Li.sub.2 MnO.sub.3 is preferably chosen in the range where maximum improvement in lithium chemical diffusion coefficient is obtained. However, the content of these inactive materials should not be too high, since in that case a reduction in battery energy density may be observed.
Thus, the cathode material according to the invention contains 1 to 50% by mole, preferably 1 to 40% by mole and more preferably 3 to 30% by mole of .alpha.-Mn.sub.2 O.sub.3 and/or Li.sub.2 MnO.sub.3.
At about 25 mole-% of .alpha.-Mn.sub.2 O.sub.3 along with LiMn.sub.2 O.sub.4 and at about 25% of Li.sub.2 MnO.sub.3 along with Li.sub.1.5 Mn.sub.2 O.sub.4 maxima are obtained on the lithium chemical diffusion coefficient curve as can be seen in FIG. 5.
The lithium chemical diffusion coefficient is surprisingly remarkably improved in the instance where the cathode material according to the invention contains about 25 mole-% of .alpha.-Mn.sub.2 O.sub.3 and/or Li.sub.2 MnO.sub.3.
Several methods for the production of spinel lithium Mn.sub.2 O.sub.4 materials are known in the art:
Thus, Mat. Res. Bull., 18, pp. 461-472 (1983) describes preparation of Li.sub.1+x Mn.sub.2 O.sub.4 wherein x=0.96 to 1.24 by calcining a mixture of solid LiCO.sub.3 and Mn.sub.2 O.sub.3, first at a temperature of 650.degree. C. for 12 hours and then at 850.degree. C. for 24 hours.
U.S. Pat. No. 5,266,299 describes preparation of Li.sub.1+x Mn.sub.2 O.sub.4 in which 0<x<1 by reacting a mixture of LiMn.sub.2 O.sub.4 or .lambda.-Mn.sub.2 O.sub.3 with LiI in a sealed container at about 150.degree. C. or with reflux in acetonitrile.
U.S. Pat No. 4,980,251 describes preparation of Li.sub.1-x Mn.sub.2 O.sub.4 in which 0<x<1 by heating a mixture of Li.sub.2 CO.sub.3 and MnCO.sub.3 to a temperature in the range of 200 to 600.degree. C.
A process for synthesising cathode material for lithium secondary batteries using manganese acetate as starting material is described in Barboux et al.: "The Use of Acetates as Precursors of the Low-Temperature Synthesis of LiMn.sub.2 O.sub.4 and LiCoO.sub.2 intercalation Compounds", Jour. Solid State Chem., 94, pp. 185-96 (1991) and in U.S. Pat. No. 5,135,732 to Barboux et al. In this process a gelatinous precipitate is formed from a dilute aqueous solution of manganese
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Miyamoto et al., "Synthesis of lithium manganese oxide . . . " Denki Kagaku oyobi Kogyo Butsuri Kagaku, 61 (10), 1222-3. (No month available), 1993.
Cullity, "Elements of X-Ray Diffraction", second edition, Addison-Wesley, pp. 377-379. (No month available.), 1978.
Chaney Carol
Danionics A/S
Nuzzolillo Maria
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