Hitachi Metals, Ltd.

Sho Furutsuki

Shin Takahashi

Hisato Tokoro

Akira Gunji

Takashi Nakabayashi

Tatsuya Toyama

Shuichi Takano

Xiaoliang Feng

A compound having a layered structure that is used for a positive electrode active material for a lithium ion secondary battery achieves both a high energy density and a high cyclability. The positive electrode active material for a lithium ion secondary battery contains a compound having a layered structure belonging to a space group R-3m, in which the compound having a layered structure is represented by a compositional formula: LiM1Owherein M1 represents a metal element or metal elements other than Li, and contains at least Ni, &#x2212;0.03&#x2264;a&#x2264;0.10, and &#x2212;0.1&#x3c;&#x3b1;&#x3c;0.1, a proportion of Ni in M1 is larger than 70 atom %, and a site occupancy of a transition metal or transition metals at a 3a site obtained by structural analysis by a Rietveld method is less than 2%, and a content of residual lithium hydroxide in the positive electrode active material is 1 mass % or less.

Positive electrode active material for lithium ion secondary battery, manufacturing method thereof, and lithium ion secondary battery

A positive electrode active material includes a primary particle represented by Compositional Formula (1):NiCoMO&#x2003;&#x2003;(1),where x is a number satisfying a relation represented by an expression &#x2212;0.12&#x2264;x&#x2264;0.2; y is a number satisfying a relation represented by an expression 0.7&#x2264;y&#x2264;0.9; z is a number satisfying a relation represented by an expression 0.05&#x2264;z&#x2264;0.3; and M is at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo, and Nb; or a secondary particle into which the primary particle aggregates. The primary particle or the secondary particle includes a free lithium compound in a weight proportion of 0.1% or more and 2.0% or less, and the weight of lithium hydroxide in the free lithium compound is 60% or less of the weight of lithium carbonate in the free lithium compound.

Positive electrode active material for lithium ion secondary battery, and positive electrode for lithium ion secondary battery and lithium ion secondary battery comprising the same

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Tokyo, Japan

Sho Furutsuki