JP-7854603-B2 - Non-aqueous electrolyte secondary battery

JP7854603B2JP 7854603 B2JP7854603 B2JP 7854603B2JP-7854603-B2

Inventors

神貴志
鈴木慎也
新名史治
鶴田翔
柳田勝功

Assignees

パナソニックＩＰマネジメント株式会社

Dates

Publication Date: 20260507
Application Date: 20240702
Priority Date: 20190329

Claims (5)

A non-aqueous electrolyte secondary battery comprising an electrode body including a positive electrode, a negative electrode, and a separator, and a non-aqueous electrolyte, The positive electrode comprises positive electrode active material A and positive electrode active material B. The positive electrode active materials A and B are secondary particles formed by the aggregation of primary particles, The average primary particle diameter of the positive electrode active material B is 0.5 μm or larger, and is greater than the average primary particle diameter of the positive electrode active material A. The average secondary particle diameter of the positive electrode active material B is 2 μm to 7 μm, and is smaller than the average secondary particle diameter of the positive electrode active material A. The positive electrode active material A is A lithium transition metal composite oxide A contains Ni, Co, and Mn, and also contains a metal M selected from Ti, Nb, W, and Zr, wherein the content of Ni is 82 mol% or more and the content of Co is 8 mol% or less relative to the total number of moles of metal elements excluding Li, A first layer formed on the particle surface of the lithium transition metal composite oxide A, which is composed of a lithium metal oxide containing the aforementioned metal M, A second layer formed on the first layer, composed of a boron compound, Includes, A non-aqueous electrolyte secondary battery, wherein the first layer is formed on the particle surface of the lithium transition metal composite oxide A over its entire surface without intervening through the second layer.
The non-aqueous electrolyte secondary battery according to claim 1, wherein the second layer covers the entire area of the first layer.
The positive electrode active material B contains Ni, Co, and Mn, and also contains a metal M selected from Ti, Nb, W, and Zr, wherein the Ni content is 80 mol% or more of the lithium transition metal composite oxide B relative to the total number of moles of metal elements excluding Li, as described in claim 1 or 2.
The positive electrode active material B includes a surface layer formed on the surface of the secondary particles of the lithium transition metal composite oxide B. The surface layer is composed of a lithium metal oxide containing the metal M. The non-aqueous electrolyte secondary battery according to claim 3, wherein the content of the surface layer in the positive electrode active material B is lower than the content of the first layer in the positive electrode active material A.
The positive electrode active material B includes a second surface layer formed on the surface layer, The non-aqueous electrolyte secondary battery according to claim 4, wherein the second surface layer is composed of a boron compound.

Description

This disclosure relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery containing a lithium transition metal composite oxide as the positive electrode active material. Conventionally, positive electrode active materials have been known in which other compounds are present on the particle surface of lithium transition metal composite oxides in order to improve battery performance such as storage characteristics. For example, Patent Document 1 discloses a positive electrode active material manufactured by firing lithium transition metal composite oxide particles with a compound of a predetermined element (such as TiO2 ) from groups 4 to 6 whose oxide has a melting point of 750°C or higher present on the particle surface. Patent Document 2 also discloses a positive electrode active material manufactured by firing lithium transition metal composite oxide particles with a borate compound present on the particle surface, wherein the carbonate ion content is 0.15% by weight or less and the borate ion content is 0.01% by weight to 5.0% by weight. Japanese Patent Publication No. 2004-253305Japanese Patent Publication No. 2010-040382 This is a perspective view of a non-aqueous electrolyte secondary battery, which is an example of an embodiment.This is a perspective view of an electrode body, which is an example of an embodiment. Conventionally, it has been known that the initial resistance of a battery can be reduced by placing a lithium metal compound represented by the general formula Li x My O z on the particle surface of a lithium transition metal composite oxide. This lithium metal compound is thought to function as a lithium ion conductor and contribute to reducing the charge transfer resistance of the positive electrode. On the other hand, placing a lithium metal compound on the particle surface of a lithium transition metal composite oxide does not suppress the increase in battery resistance during high-temperature cycling, and may even increase the resistance. The inventors have succeeded in reducing initial resistance while suppressing resistance increase during high-temperature cycling by forming a first layer composed of a lithium metal compound and a second layer composed of a boron compound covering the first layer on the particle surface of a lithium transition metal composite oxide. The presence of the second boron compound layer covering the first layer forms a strong film containing M and boron on the particle surface of the positive electrode active material during high-temperature cycling. This is thought to suppress side reactions of the non-aqueous electrolyte in the positive electrode and the elution of metals from the positive electrode active material, thereby suppressing the increase in battery resistance. The following describes in detail an example of an embodiment of the non-aqueous electrolyte secondary battery according to this disclosure. In the following description, a non-aqueous electrolyte secondary battery 10 is exemplified, in which a wound electrode body 14 is housed in an outer casing 11 made of a laminate sheet. However, the outer casing is not limited to this and may be, for example, cylindrical, rectangular, or coin-shaped. Furthermore, the electrode body may be a laminated type in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators in between. Figure 1 is a perspective view showing the external appearance of a non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. As illustrated in Figure 1, the non-aqueous electrolyte secondary battery 10 comprises an outer casing 11 composed of two laminate films 11A and 11B. The non-aqueous electrolyte secondary battery 10 also comprises an electrode body 14 housed in the outer casing 11 and a non-aqueous electrolyte. The outer casing 11, for example, has a roughly rectangular shape in plan view and includes a housing portion 12 that houses the electrode body 14 and the non-aqueous electrolyte, and a sealing portion 13 formed around the housing portion 12. The laminate films 11A and 11B are generally composed of resin films containing a metal layer such as aluminum. The housing portion 12 can be provided by forming a recess capable of housing the electrode body 14 in at least one of the laminate films 11A and 11B. In the example shown in Figure 1, the recess is formed only in the laminate film 11A. The sealing portion 13 is formed by joining the peripheral edges of the laminate films 11A and 11B. In the example shown in Figure 1, the sealing portion 13 is formed in a frame shape with approximately the same width, surrounding the housing portion 12. The non-aqueous electrolyte secondary battery 10 includes a pair of electrode leads (positive electrode lead 15 and negative electrode lead 16) connected to an electrode body 14. In the example shown in Figure 1, the positive electrode lead