Manganese oxide, lithium manganese complex oxide and cobalt-coated lithium manganese complex oxide, and preparation processes thereof
AssigneeToda Kogyo Corporation
InventorsShoichi Fujino, Hiroshi Takahama, Mitsuaki Hatatani, Norimiki Sugiyama, Hideaki Sadamura
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Abstract
A manganese oxide which has a calcium or/and magnesium content of 0.01 to 2.50 mol % based on the moles of manganese, a lithuim manganese complex oxide using the manganese oxide, and a cobalt-coated lithuim manganese complex oxide are disclosed. These provide a particularly high discharge capacity and are useful for the improvement of cycle characteristics of a secondary battery as an active material of a positive electrode for a secondary battery with a nonaqueous electrolyte.
Claims12
A manganese oxide which has a calcium or/and magnesium content of 0.01 to 2.50 mol % based on the moles of manganese.
A process for preparing the manganese oxide, comprising the steps of:
- adding to an aqueous magnesium salt solution, a calcium salt or/and magnesium salt such that the calcium or/and magnesium content based on the moles of manganese is 0.01 to 2.50 mol % and an aqueous alkali solution at an alkali equivalent ratio of between 0.1 and 10 based on the total of the manganese and the calcium or/and magnesium to obtain an aqueous suspension of manganese (II) hydroxide,
- supplying an oxygen-containing gas into the aqueous suspension heated to a temperature of 20 to 100° C. to produce a precipitate by the oxidation of the manganese ions, and
- collecting the precipitate after filtration, washing and drying.
A cobalt-coated lithium manganese complex oxide, wherein the coating amount of cobalt (Z wt %) in relation to a BET specific surface area (S m2/g) of the lithium manganese complex oxide is within the range expressed by the following equation (1):
- 0.05×S≦Z≦1.50×S (1)
A process for preparing the cobalt-coated lithium manganese complex oxide, comprising the steps of:
- oxidizing lithium manganese complex oxide particles dispersed in an aqueous alkali solution and a cobalt compound at a temperature of 20 to 100° C. so that a cobalt oxide epitaxially grows on the lithium magnesium complex oxide, and
- collecting the resulting oxide after filtration, washing and drying.
Dependencies are inferred from the claim text.