CN-115117295-B - Positive electrode and nonaqueous electrolyte secondary battery

CN115117295BCN 115117295 BCN115117295 BCN 115117295BCN-115117295-B

Abstract

The present invention relates to a positive electrode and a nonaqueous electrolyte secondary battery. The positive electrode was used for a nonaqueous electrolyte secondary battery. The positive electrode includes a positive electrode base material and a positive electrode active material layer. The positive electrode active material layer is disposed on the surface of the positive electrode base material. The positive electrode active material layer includes a1 st layer and a2 nd layer. Layer 2 is disposed between the positive electrode substrate and layer 1. Layer 1 contains the 1 st positive electrode active material. The 1 st positive electrode active material contains 1 st agglomerated particles. The 2 nd layer contains the 2 nd positive electrode active material. The 2 nd positive electrode active material contains 2 nd aggregated particles and single particles. The 1 st agglomerated particle and the 2 nd agglomerated particle are each formed by agglomerating 50 or more primary particles. The single particles have an arithmetic average diameter larger than that of the primary particles.

Inventors

KAJIMOTO HIROSHI
Ping Zhongxiuhe
TERAUCHI MASUMI
WATANABE HIROYASU

Assignees

泰星能源解决方案有限公司

Dates

Publication Date: 20260505
Application Date: 20220317
Priority Date: 20210318

Claims (4)

1. The positive electrode is a positive electrode for a nonaqueous electrolyte secondary battery, Comprises a positive electrode base material and a positive electrode active material layer, The positive electrode active material layer is disposed on the surface of the positive electrode base material, The positive electrode active material layer includes a1 st layer and a2 nd layer, The 2 nd layer is disposed between the positive electrode substrate and the 1 st layer, The 1 st layer contains a1 st positive electrode active material, The 1 st positive electrode active material contains 1 st agglomerated particles, The 2 nd layer contains a2 nd positive electrode active material, The 2 nd positive electrode active material contains 2 nd agglomerated particles and single particles, The 1 st agglomerated particle and the 2 nd agglomerated particle are each formed by agglomerating 50 or more primary particles, The 1 st agglomerated particle has an arithmetic average diameter of 5 to 20 μm, The arithmetic mean diameter of the 2 nd agglomerated particles is 5 to 20 μm, The primary particles have an arithmetic mean diameter of 0.05 to 0.2 μm, The single particles have an arithmetic average diameter larger than that of the primary particles, The 2 nd agglomerated particle and the 1 st agglomerated particle are the same particle.
2. The positive electrode according to claim 1, wherein the 1 st aggregated particle and the 2 nd aggregated particle each have an arithmetic average diameter larger than that of the single particle.
3. The positive electrode according to claim 1 or claim 2, wherein the relation of formula (I) is satisfied: 0.2≦T1/(T1+T2)≦0.5...(I) in the formula (I), T1 represents the thickness of the 1 st layer, and T2 represents the thickness of the 2nd layer.
4. A nonaqueous electrolyte secondary battery comprising the positive electrode according to any one of claims 1 to 3.

Description

Positive electrode and nonaqueous electrolyte secondary battery Technical Field The present technology relates to a positive electrode and a nonaqueous electrolyte secondary battery. Background Japanese patent application laid-open No. 2020-087879 discloses a lithium metal composite oxide powder composed of secondary particles formed by aggregation of primary particles and single particles. Disclosure of Invention In general, a positive electrode of a nonaqueous electrolyte secondary battery (hereinafter, may be abbreviated as "battery") includes a positive electrode base material and a positive electrode active material layer. The positive electrode active material layer is formed on the surface of the positive electrode base material. The positive electrode active material layer contains a positive electrode active material. In many cases, the positive electrode active material is an agglomerated particle. The aggregated particles are secondary particles in which a plurality of primary particles are aggregated. It has been proposed to mix single particles with agglomerated particles. The single particles are primary particles which grow relatively large. The single particles may be present independently of the agglomerated particles. The filling property of single particles is good. By mixing the single particles with the aggregated particles, the filling property of the positive electrode active material layer can be improved. The filling property of the positive electrode active material layer is improved, and thus the energy density of the battery can be improved. However, single particles tend to have higher resistivity than agglomerated particles. By mixing the single particles with the aggregated particles, the resistivity of the positive electrode active material layer tends to increase. The resistivity of the positive electrode active material layer increases, and thus, for example, the input/output characteristics of the battery may be degraded. The purpose of the present technology is to achieve both the filling properties and the resistivity of a positive electrode active material layer. The constitution and the operational effects of the present technology will be described below. However, the mechanism of action of the present specification includes estimation. The mechanism of action does not limit the scope of the present technology. [1] The positive electrode was used for a nonaqueous electrolyte secondary battery. The positive electrode includes a positive electrode base material and a positive electrode active material layer. The positive electrode active material layer is disposed on the surface of the positive electrode base material. The positive electrode active material layer includes a1 st layer and a2 nd layer. The 2 nd layer is disposed between the positive electrode substrate and the 1 st layer. Layer 1 contains the 1 st positive electrode active material. The 1 st positive electrode active material contains 1 st agglomerated particles. The 2 nd layer contains the 2 nd positive electrode active material. The 2 nd positive electrode active material contains 2 nd aggregated particles and single particles. The 1 st agglomerated particle and the 2 nd agglomerated particle are each formed by agglomerating 50 or more primary particles. The single particles have an arithmetic average diameter larger than that of the primary particles. Hereinafter, in this specification, the 1 st aggregated particle and the 2 nd aggregated particle may be collectively referred to as "aggregated particles". The 2 nd agglomerated particle may be the same as or different from the 1 st agglomerated particle. The positive electrode active material layer of the present technology has a multilayer structure. That is, the positive electrode active material layer includes a1 st layer (upper layer) and a2 nd layer (lower layer). The 1 st layer (upper layer) is disposed on the surface side of the positive electrode active material layer compared to the 2 nd layer (lower layer). According to the new knowledge of the present technology, the resistivity of the entire positive electrode active material layer tends to be strongly influenced by the resistivity in the vicinity of the surface layer of the positive electrode active material layer. Layer 1 (upper layer) is mainly composed of agglomerated particles. The agglomerated particles may have a relatively low resistivity. The upper layer is mainly composed of aggregated particles, so that the increase in resistivity associated with the mixing of single particles can be reduced. Layer 2 (lower layer) is composed of a mixture of agglomerated particles and single particles. By mixing the single particles in the lower layer, the increase in resistivity is reduced, and the filling property of the positive electrode active material layer can be improved. [2] For example, the 1 st agglomerated particle and the 2 nd agglomerated particle may each have an arithmetic average