Jx Nippon Mining Metals Corporation

Hirohito Satoh

Yoshio Kajiya

Ryuichi Nagase

Nagase Ryuichi

The present invention provides a positive electrode active material for lithium ion battery having good rate characteristics. The positive electrode active material for lithium ion battery has a layer structure expressed by a composition formula: Li(NiM)O, wherein M represents Mn and Co, x represents 0.9 to 1.2, y represents 0.6 to 0.9, and z represents 1.8 to 2.4. The positive electrode active material has a particle size ratio D50P/D50 of 0.60 or more, wherein D50 is the average secondary particle size of the positive electrode active material powder, and D50P is the average secondary particle size of the positive electrode active material powder after pressing at 100 MPa. The positive electrode active material contains 3% or less particles having a particle size of 0.4 &#x3bc;m or less in terms of the volume ratio after pressing at 100 MPa.

Positive electrode active material for lithium-ion battery, positive electrode for lithium-ion battery, and lithium-ion battery

Disclosed is a positive electrode active material that provides an improved capacity density. Specifically disclosed is a positive electrode active material for a lithium ion battery with a layered structure represented by Li(NiM)O(wherein M represents at least one element selected from a group consisting of Mn, Co, Mg, Al, Ti, Cr, Fe, Cu, and Zr; x is in the range from 0.9 to 1.2; y is in the range from 0.3 to 0.95; and z is in the range from 1.8 to 2.4), wherein, when a value obtained by dividing an average of peak intensities observed between 1420 and 1450 cmand between 1470 and 1500 cmby the maximum intensity of a peak appearing between 520 and 620 cmin an infrared absorption spectrum obtained by FT-IR is represented by A, A satisfies the following relational formula: 0.20y&#x2212;0.05&#x2266;A&#x2266;0.53y&#x2212;0.06.

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Kitaibaraki, Japan

Hirohito Satoh