POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY, POSITIVE ELECTRODE AND LITHIUM ION SECONDARY BATTERY

• Main Author: NAGATA HIROAKI
• Format: Patent
• Language: English; Japanese
• Published: 19.08.2021
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRICITY; PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSIONOF CHEMICAL INTO ELECTRICAL ENERGY

To provide a positive electrode active material for lithium ion secondary batteries, which is high in capacity and exhibits a high output.SOLUTION: A positive electrode active material includes first positive electrode active material particles A and second positive electrode active material particles B. The first positive electrode active material particles A have a solid structure, and have a tap density of 2.1 g/cm3 or more and an average particle size (D50) of 8 μm or more and 30 μm or less. The second positive electrode active material particles B have a hollow structure, and have a tap density of 1.8 g/cm3 or less and an average particle size (D50) of 1 μm or more and 8 μm or less, the average particle size (D50) of the second positive electrode active material particles B being smaller than the average particle size (D50) of the first positive electrode active material particles A. When a positive electrode material including the positive electrode active material is pressed down with a linear pressure of 200 N/mm, the average aspect ratio (W/L) of gaps of the second positive electrode active material particles B is 0.5 or less, and the mass (WA)of each first positive electrode active material particle A and the mass (WB)of each second positive electrode active material particle B satisfy an expression (1). 0.001≤WB/(WA+WB)≤0.5...(1)SELECTED DRAWING: Figure 1 【課題】高容量であるとともに、高出力を示す、リチウムイオン二次電池用正極活物質の提供。【解決手段】第１の正極活物質粒子Ａと、第２の正極活物質粒子Ｂとを含み、第１の正極活物質粒子Ａは、中実構造を有し、タップ密度が２．１ｇ／ｃｍ３以上であり、かつ、平均粒径（Ｄ５０）が８μｍ以上３０μｍ以下であり、第２の正極活物質粒子Ｂは、中空構造を有し、タップ密度が１．８ｇ／ｃｍ３以下であり、平均粒径（Ｄ５０）が１μｍ以上８μｍ以下、かつ、第１の正極活物質粒子Ａの平均粒径（Ｄ５０）より小さく、正極活物質を含む正極材料を線圧２００Ｎ／ｍｍで圧下したとき、第２の正極活物質粒子Ｂの空隙の平均アスペクト比（Ｗ／Ｌ）が０．５以下であり、第１の正極活物質粒子Ａの質量（ＷＡ）と第２の正極活物質粒子Ｂの質量（ＷＢ）との比率が式（１）を満たす、正極活物質。０．００１≦ＷＢ／（ＷＡ＋ＷＢ）≦０．５・・・（１）【選択図】図１