Hitachi Metals, Ltd.

Proterial, Ltd.

Tatsuya Tooyama

Hisato Tokoro

Akira Gunji

Shuichi Takano

Takashi Nakabayashi

Shin Takahashi

Xiaoliang Feng

Making a positive electrode active material for lithium ion secondary batteries includes: weighting and mixing lithium carbonate and a compound containing respective metallic elements other than Li in a composition formula LiNiCoM2M2Oso as to have a metallic constituent ratio of the formula to obtain a mixture, and firing the mixture to obtain a lithium composite compound. Performing, on the mixture, a first heat treatment at 200&#xb0; C. to 400&#xb0; C. for 0.5 to 5 hours to obtain a first precursor. A step of performing a heat treatment on the first precursor under an oxidizing atmosphere at 450&#xb0; C. to 800&#xb0; C. for 0.5 to 50 hours, and reacting 92 mass % or more of the lithium carbonate to obtain a second precursor, and a finishing step of performing a heat treatment on the second precursor under an oxidizing atmosphere at 755&#xb0; C. to 900&#xb0; C. for 0.5 to 50 hours to obtain the lithium composite compound.

Method for producing positive electrode active material for lithium ion secondary batteries

Provided are a cathode active material used for a lithium ion secondary battery having a high discharge capacity, and a small increase in internal resistance caused following charge/discharge cycles; a method for producing the same; and a lithium ion secondary battery. The cathode active material has a layered structure assigned to a space group of R-3m represented by the formula: LiM1O(where M1 represents metal elements other than Li containing at least Ni, &#x2212;0.05&#x2264;a&#x2264;0.15, &#x2212;0.1&#x2264;&#x3b1;&#x2264;0.1). A content of Ni is 70 atom % or more, and a generating amount of oxygen gas in the range from 200&#xb0; C. to 450&#xb0; C. is 30 mass ppm or less. The method comprises the steps of grinding and mixing a lithium raw material, and firing the resultant mixture in the range of 650&#xb0; C. or more and 900&#xb0; C. or less.

Cathode active material used for lithium ion secondary battery, method for producing same, and lithium ion secondary battery

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Tokyo, Japan

Tatsuya Tooyama