JP-7856885-B2 - Positive electrode active material for non-aqueous electrolyte secondary batteries and method for producing the same

JP7856885B2JP 7856885 B2JP7856885 B2JP 7856885B2JP-7856885-B2

Inventors

河井健太
宮本佳映
白石大河
吉田泰弘
村山昌宏
松井智也

Assignees

日亜化学工業株式会社

Dates

Publication Date: 20260512
Application Date: 20220125
Priority Date: 20210201

Claims (9)

It has a layered structure and contains secondary particles which are made up of multiple primary particles that contain lithium and nickel-containing lithium transition metal composite oxides, The smoothness of the secondary particle is greater than 0.73, and the circularity of the secondary particle is greater than 0.83. The secondary particle contains cobalt and has a first region with a depth of 150 nm from the particle surface and a second region with a depth of 10 nm or less from the particle surface, and the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium is greater in the second region than in the first region. A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the difference between the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium in the second region and the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium in the first region is 0.02 or more .
The positive electrode active material according to claim 1, wherein the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium in the second region, divided by the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium in the first region, is 2 or more.
It has a layered structure and contains secondary particles which are made up of multiple primary particles that contain lithium and nickel-containing lithium transition metal composite oxides, The smoothness of the secondary particle is greater than 0.73, and the circularity of the secondary particle is greater than 0.83. The secondary particle contains cobalt and has a first region with a depth of 150 nm from the particle surface and a second region with a depth of 10 nm or less from the particle surface, and the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium is greater in the second region than in the first region. A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium in the second region, divided by the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium in the first region, is 2 or more.
The positive electrode active material according to any one of claims 1 to 3, wherein the secondary particles have a volume-average particle size of 1 μm or more and 30 μm or less.
The positive electrode active material according to any one of claims 1 to 4 , wherein the secondary particles are such that the value obtained by dividing the difference between the 90% particle size D90 and the 10 % particle size D10 in the volume-based cumulative particle size distribution by the 50% particle size D50 is less than 0.9.
The ratio of the number of moles of nickel to the total number of moles of metal elements other than lithium is greater than 0 and less than 1. A positive electrode active material according to any one of claims 1 to 5, having a composition in which the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium is greater than 0 and 0.5 or less.
A positive electrode active material according to any one of claims 1 to 6, having a composition represented by the following formula (1). Li p Ni x Co y M 1 z M 2 w O 2 (1) 0.95≦p≦1.5, 0＜x＜1, 0＜y≦0.5, 0≦z≦0.5, 0≦w≦0.1, x+y+z+w≦1, M1 is at least one selected from the group consisting of Al and Mn, and M2 is at least one selected from the group consisting of B, Na, Mg, Si, P, S, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, In, Sn, Ba, La, Ce, Nd, Sm, Eu, Gd, Lu, Ta, W, and Bi.
The present invention provides a cathode active material raw material having a layered structure, comprising secondary particles formed by the aggregation of multiple primary particles containing lithium and nickel-containing lithium transition metal composite oxides, wherein the smoothness of the secondary particles is greater than 0.73 and the circularity of the secondary particles is greater than 0.83. The positive electrode active material raw material is brought into contact with a cobalt compound to obtain a cobalt deposit, A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising heat-treating the aforementioned cobalt deposit at a temperature of 500°C or higher and less than 1100°C to obtain a heat-treated product.
A non-aqueous electrolyte lithium-ion secondary battery comprising a positive electrode containing the positive electrode active material described in any one of claims 1 to 7, a negative electrode, and a non-aqueous electrolyte.

Description

This disclosure relates to a positive electrode active material for non-aqueous electrolyte secondary batteries and a method for producing the same. High power output characteristics are required for electrode active materials in non-aqueous electrolyte secondary batteries used in large power equipment such as electric vehicles. To achieve high power output characteristics, positive electrode active materials with a structure of secondary particles formed by the aggregation of many primary particles are considered effective. In this regard, a technique has been proposed to narrow the particle size distribution of secondary particles formed by the aggregation of primary particles into a nearly spherical shape as a positive electrode active material, enabling higher battery capacity (see, for example, Patent Document 1). Furthermore, a technique for producing spherical nickel-cobalt-aluminum hydroxide precursor material by coprecipitation has been proposed, which is said to improve cycle characteristics (see, for example, Patent Document 2). On the other hand, a technique has been proposed to provide a coating layer containing Co on the surface of the positive electrode active material, which is said to improve storage stability (weather resistance) while maintaining battery characteristics (see, for example, Patent Document 3). International Publication No. 2013/183711International Publication No. 2016/180288Japanese Patent Publication No. 2018-14208 This is a schematic cross-sectional view of secondary particles contained in the positive electrode active material. In this specification, the term "process" includes not only independent processes but also processes that are not clearly distinguishable from other processes, provided that their intended purpose is achieved. Furthermore, the content of each component in a composition refers to the total amount of multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component exist in the composition. The embodiments of this disclosure will now be described in detail. However, the embodiments described below are illustrative examples of positive electrode active materials for non-aqueous electrolyte secondary batteries and their manufacturing methods for embodying the technical concept of this disclosure, and this disclosure is not limited to the positive electrode active materials for non-aqueous electrolyte secondary batteries and their manufacturing methods described below. Positive electrode active material for non-aqueous electrolyte secondary batteries The positive electrode active material for non-aqueous electrolyte secondary batteries (hereinafter also simply referred to as "positive electrode active material") has a layered structure and is composed of secondary particles which are aggregates of primary particles containing lithium and nickel-containing lithium transition metal composite oxides. The smoothness of the secondary particles constituting the positive electrode active material is greater than 0.73, and the circularity of the secondary particles is greater than 0.83. The secondary particles contain cobalt in their composition, and for example, they have cobalt-containing deposits on their surface. The secondary particles having cobalt-containing deposits have a first region with a depth of 150 nm from the particle surface and a second region with a depth of 10 nm or less from the particle surface, and the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium in the composition is greater in the second region than in the first region. The secondary particles constituting the positive electrode active material have a specific shape, defined by their smoothness and circularity. This increases the contact area between the secondary particles and conductive additives within the positive electrode, thus reducing resistance at the interface between the secondary particles and the conductive additives. Furthermore, when depositing cobalt-containing materials onto the surface of the secondary particles, the compound adheres more evenly, reducing the resistive component. Reducing the resistive component in the positive electrode active material improves the output characteristics of non-aqueous electrolyte secondary batteries. Additionally, cracking of secondary particles during pressure molding during positive electrode formation is reduced. This is thought to be because the pressure during pressure molding is applied uniformly to the entire particle. These effects derived from the shape of the secondary particles constituting the positive electrode active material are specifically described, for example, in International Publication No. 2021/020531. In the secondary particles of lithium transition metal composite oxides that constitute the positive electrode active material, cobalt is unevenly distributed near the surface of the par