KR-20260064566-A - POSITIVE ELECTRODE ACTIVE MATERIAL, BATTERY, AND METHOD OF PRODUCING POSITIVE ELECTRODE ACTIVE MATERIAL

Abstract

As a positive electrode active material, the positive electrode active material comprises a plurality of secondary particles, each of the plurality of secondary particles comprises a plurality of primary particles, each of the plurality of primary particles comprises an olivine-type phosphate compound, carbon and lithium phosphate are attached to at least a portion of the surface of the secondary particles, and in the cross-section of the secondary particles, the secondary particles are composed of a center, a middle part and an outer periphery, and the relationship 1.05 ≤ C LPO / X LPO is satisfied, wherein C LPO represents the substance amount concentration of lithium phosphate in the outer periphery, and X LPO represents the average value of the substance amount concentration of lithium phosphate in the center, the middle part and the outer periphery.

Inventors

• 이시가키 유키
• 에구치 다츠야
• 기미지마 다케시

Assignees

• 도요타 지도샤（주）

Dates

Publication Date

20260507

Application Date

20251024

Priority Date

20241031

Claims (11)

1. As a positive electrode active material, The above positive electrode active material comprises a plurality of secondary particles, and Each of the plurality of the above secondary particles comprises a plurality of primary particles, and Each of the plurality of primary particles comprises an olivine-type phosphate compound, and Carbon and lithium phosphate are attached to at least a portion of the surface of the above secondary particle, and In the cross-section of the secondary particle above, the secondary particle is composed of a center, an intermediate part, and an outer periphery, and The relationship 1.05≤C LPO /X LPO is satisfied, and The above C LPO represents the substance amount concentration of lithium phosphate in the outer periphery, and The above X LPO is a positive electrode active material representing the average value of the amount of lithium phosphate concentration in the center, the middle part, and the outer periphery.
2. In Article 1, Positive electrode active material satisfying the relationship 1.5≤C LPO /X LPO .
3. In Article 1, Positive electrode active material satisfying the relationship C LPO /X LPO ≤ 7.0.
4. In Article 1, Positive electrode active material satisfying the relationship C LPO /X LPO ≤ 4.5.
5. In Article 1, Positive electrode active material satisfying the relationship C LPO /X LPO ≤3.0.
6. In Article 1, The surface of the above secondary particle includes a first attachment portion and a second attachment portion, and Carbon is attached to the first attachment part above, and A positive electrode active material having carbon and lithium phosphate attached to the second attachment portion above.
7. In Article 1, The above olivine-type phosphate compound is a positive electrode active material, which is manganese iron lithium phosphate.
8. A battery comprising a positive electrode active material described in any one of claims 1 to 7.
9. In Article 8, A battery having a bipolar structure.
10. (a) forming a first slurry by mixing a manganese compound, a first lithium compound, a first phosphate compound, a carbon material, and a first solvent, (b) forming precursor particles by drying the first slurry, (c) Forming a first particle by performing heat treatment on the above precursor particle, (d) forming a second slurry by mixing the first particle, the second lithium compound, the second phosphate compound, and the second solvent, (e) A method for manufacturing a positive electrode active material, comprising manufacturing a second particle by drying the second slurry.
11. In Article 10, The concentration of the second lithium compound in the second slurry is greater than 0.1% and less than or equal to 0.5% in mass fraction, and A method for manufacturing a positive electrode active material, wherein the concentration of the disodium phosphate compound in the second slurry is greater than 0.3% and less than or equal to 1.5% by mass fraction.

Description

Positive electrode active material, battery, and method of producing positive electrode active material The present disclosure relates to a positive electrode active material, a battery, and a method for manufacturing a positive electrode active material. Japanese Patent Publication No. 2019-175764 discloses a positive electrode material for a lithium-ion secondary battery in which the surface of an olivine-type phosphate compound is coated with carbon. Olivine-type phosphate compounds are being developed as positive electrode active materials. Conventionally, it has been proposed to enhance electronic conductivity by coating olivine-type phosphate compounds with carbon. However, there is room for improvement in durability. The purpose of the present disclosure is to improve durability. The technical configuration and effects of the present disclosure are described below. However, the mechanism of action of the present disclosure includes presumptions. The mechanism of action does not limit the technical scope of the present disclosure. [1] As a positive electrode active material, The above positive electrode active material comprises a plurality of secondary particles, and Each of the plurality of the above secondary particles comprises a plurality of primary particles, and Each of the plurality of primary particles comprises an olivine-type phosphate compound, and Carbon and lithium phosphate are attached to at least a portion of the surface of the above secondary particle, and In the cross-section of the secondary particle above, the secondary particle is composed of a center, an intermediate part, and an outer periphery, and The relationship 1.05≤C LPO /X LPO is satisfied, and The above C LPO represents the substance amount concentration of lithium phosphate in the outer periphery, and The above X LPO is a positive electrode active material representing the average value of the amount of lithium phosphate concentration in the center, the middle part, and the outer periphery. When only carbon is attached to the surface of the secondary particles, it is thought that capacity degradation is accelerated as the olivine-type phosphate compounds contained in the secondary particles deteriorate with each charge-discharge cycle. In other words, there is a possibility that sufficient durability may not be obtained. On the surface of the secondary particle of the present disclosure, lithium phosphate ( Li₃PO₄ , which may be abbreviated as "LPO") is attached in addition to carbon. Furthermore, carbon and LPO are attached to the interior of the secondary particle of the present disclosure as well as on the surface. It is believed that when the substance amount concentration of LPO on the surface of the secondary particle is greater than the substance amount concentration of LPO inside the secondary particle, particularly when the relationship 1.05 ≤ C LPO₄ / X LPO₄ is satisfied, the deterioration of the olivine-type phosphate compound contained in the secondary particle can be suppressed. In other words, an improvement in durability is expected. [2] Positive electrode active material described in [1], in which the relationship 1.5≤C LPO /X LPO is satisfied. With the relationship 1.5≤C LPO /X LPO satisfied, further improvement in durability is expected. [3] Positive electrode active material described in [1] or [2], satisfying the relationship C LPO /X LPO ≤7.0. As C LPO /X LPO increases, improved durability is expected. On the other hand, when C LPO /X LPO is large, the capacity tends to decrease. By satisfying the relationship C LPO /X LPO ≤ 7.0, compatibility between durability and capacity is expected. [4] Positive electrode active material described in any one of [1] to [3], wherein the relationship C LPO /X LPO ≤4.5 is satisfied. With the relationship C LPO /X LPO ≤4.5 satisfied, compatibility between durability and capacity is more expected. [5] Positive electrode active material described in any one of [1] to [4], wherein the relationship C LPO /X LPO ≤3.0 is satisfied. [6] The surface of the secondary particle above includes a first attachment portion and a second attachment portion, and Carbon is attached to the first attachment part above, and A positive electrode active material described in any one of [1] to [5], wherein carbon and lithium phosphate are attached to the second attachment portion above. [7] The above olivine-type phosphate compound is a positive electrode active material described in any one of [1] to [6], which is manganese iron lithium phosphate. [8] A battery comprising a positive electrode active material as described in any one of [1] to [7]. [9] A battery having a bipolar structure, as described in [8]. [10] (a) forming a first slurry by mixing a manganese compound, a first lithium compound, a first phosphate compound, a carbon material, and a first solvent, (b) forming precursor particles by drying the first slurry, (c) Forming a first particle by performing heat treatment on the ab