CROSS REFERENCE

This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2018/020304, filed on May 28, 2018, which claims the benefit of Japanese Application No. 2017-108483, filed on May 31, 2017 and Japanese Patent Application No. 2017-193112, filed on Oct. 2, 2017, the entire contents of each are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery.

Priority is claimed on Japanese Patent Application No. 2017-108483 filed in Japan on May 31, 2017 and Japanese Patent Application No. 2017-193112 filed in Japan on Oct. 2, 2017, the content of which is incorporated herein by reference.

BACKGROUND ART

Lithium-containing metal composite oxides have been used as positive electrode active materials for lithium secondary batteries. Lithium secondary batteries have already been put into practical use not only for small power sources for mobile phones and notebook computers, but also for medium and large power sources for automobiles and power storage.

In order to further expand the applications of lithium secondary batteries, lithium secondary batteries with higher capacity and excellent output characteristics are required.

For the purpose of improving charge/discharge efficiency in addition to a high capacity, for example, Patent Document 1 describes a positive electrode active material for a lithium secondary battery having a pore radius of not more than 50 nanometers.

Patent Document 2 describes a technique that focuses on the pores of the positive electrode active material. Patent Document 2 aims to provide a positive electrode active material in which is specified the proportion of pores having a diameter of not more than 1 μm and exhibits good battery characteristics even in a low-temperature environment.

CITATION LIST

Patent Literature

Patent Document 1: Japanese Unexamined Patent Application, First Publication No. H9-82312Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2005-310421

DISCLOSURE OF INVENTION

Problem to be Solved by Invention

However, in order to further improve the output characteristics of the lithium secondary battery, the positive electrode active materials obtained by the methods described in Patent Documents 1 and 2 can be further improved from the viewpoint of durability when used as a lithium secondary battery, particularly when it is charged for a long time in a high temperature environment.

The present invention has been made in view of such circumstances, and an object is to provide a positive electrode active material for a lithium secondary battery with improved durability at high temperature and long-time charging when used as a lithium secondary battery, a positive electrode, and a lithium secondary battery which use the positive electrode active material.

Solution to Problem

The present invention includes the following [1] to [8].

[1] A positive electrode active material for a lithium secondary battery including secondary particles which are aggregates of primary particles that are capable of being doped and dedoped with lithium ions, in which the secondary particles have a total specific surface area of pores having a pore radius of 10 nm or more and 50 nm or less of 0.27 m2/g or more and 0.90 m2/g or less in the pore distribution measured by a mercury porosimetry method.

[2] The positive electrode active material for a lithium secondary battery according to [1], in which the secondary particles are composed of a lithium-containing metal composite oxide whose compositional formula is represented by the following formula (I).
Li[Lix(Ni(1-y-z-w)CoyMnzMw)1-x]O2(I)

(in the formula (I), −0.1≤x≤0.2, 0<y≤0.4, 0≤z≤0.4, 0≤w≤0.1, M is one or more metals selected from the group consisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge. Fe, Cu, Cr, V, W, Mo, Sc, Y. Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

[3] The positive electrode active material for a lithium secondary battery according to [1] or [2], in which a content of lithium carbonate contained in a residual alkali salt on a surface of the secondary particles measured by neutralization titration is 0.3% by mass or less with respect to the total mass of the secondary particles, and a content of lithium hydroxide contained in the residual alkali salt on the surface of the secondary particles measured by neutralization titration is 0.3% by mass or less with respect to the total mass of the secondary particles.

[4] The positive electrode active material for a lithium secondary battery according to any one of [1] to [3], in which a tap density is 2.3 g/cc or more.

[5] The positive electrode active material for lithium secondary battery according to any one of [1] to [4], in which an average secondary particle diameter is 5 μm or more and 20 μm or less.

[6] The positive electrode active material for a lithium secondary battery according to any one of [1] to [5], in which, in the pore distribution measured by mercury porosimetry method, a pore specific volume of pores having a pore radius of 50 nm or more and 200 nm or less is 0.005 cm3/g or less.

[7] A positive electrode for a lithium secondary battery including the positive electrode active material for a lithium secondary battery according to any one of [1] to [6].

[8] A lithium secondary battery including the positive electrode for a lithium secondary battery according to [7].

Advantageous Effects of Invention

According to the present invention, when used as a lithium secondary battery, the positive electrode active material for a lithium secondary battery with improved durability at high temperature and long-term charge, the positive electrode using the positive electrode active material for a lithium secondary battery, and the lithium secondary battery can be provided.

