US-12620598-B2 - Positive electrode for secondary batteries, and secondary battery

US12620598B2US 12620598 B2US12620598 B2US 12620598B2US-12620598-B2

Abstract

This positive electrode for secondary batteries is provided with: a positive electrode collector which has a plurality of recesses and projections in the surface; an intermediate layer which is provided on the surface of the positive electrode collector having the recesses and projections; and a positive electrode mixture layer which is provided on the intermediate layer and contains a positive electrode active material. This positive electrode for secondary batteries is configured such that: the intermediate layer contains conductive material particles and inorganic material particles that have a higher resistance than the positive electrode active material; and both the ratio of the central particle diameter of the conductive material particles to the average depth of the recesses and projections of the positive electrode collector and the ratio of the central particle diameter of the inorganic material particles to the average depth of the recesses and projections of the positive electrode collector are 5:6 or less.

Inventors

Yuji Oura
Tomoki Shiozaki
Hideharu Takezawa

Assignees

PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20220127
Priority Date: 20170727

Claims (9)

1 . A secondary battery positive electrode, comprising: a positive electrode current collector having a plurality of irregularities on a surface thereof; an intermediate layer provided on the irregularities of the positive electrode current collector; and a positive electrode mixture layer provided on the intermediate layer and including a positive electrode active material, wherein the intermediate layer includes inorganic material particles having higher resistance than the positive electrode active material, and an average depth of the irregularities of the positive electrode current collector is 0.6 μm or more, and at least one of projections of the irregularities of the positive electrode current collector penetrates an interface between the intermediate layer and the positive electrode mixture layer and projects into the positive electrode mixture layer.
2 . The secondary battery positive electrode according to claim 1 , wherein the average depth of the irregularities of the positive electrode current collector is 2.0 μm or less.
3 . The secondary battery positive electrode according to claim 1 , wherein a ratio of a median particle diameter of the inorganic material particles to the average depth of the irregularities of the positive electrode current collector is 5:20 or more and 5:6 or less.
4 . The secondary battery positive electrode according to claim 1 , wherein the intermediate layer consists only of the inorganic material particles and a binder.
5 . The secondary battery positive electrode according to claim 1 , wherein in a cross section of the positive electrode current collector, a length of recesses of the positive electrode current collector which are in contact with the intermediate layer is 0.8 or more times and 1.8 or less times a length of projections of the positive electrode current collector which are in contact with the positive electrode mixture layer.
6 . The secondary battery positive electrode according to claim 1 , wherein the median particle diameter of the inorganic material particles is 0.2 μm or more and 1.0 μm or less.
7 . The secondary battery positive electrode according to claim 1 , wherein the inorganic material particles have a resistivity of 10 12 Ωcm or more, and the inorganic material particles are at least one of the group consisting of metal oxide particles, metal nitride particles, metal fluoride particles, and insulating magnetic particles.
8 . A secondary battery, comprising: the positive electrode according to claim 1 ; a negative electrode; and an electrolyte.
9 . The secondary battery positive electrode according to claim 1 , wherein a tip of at least one of the projections of the irregularities is spaced away from the positive electrode mixture layer in a thickness direction of the current collector.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a Division of U.S. patent application Ser. No. 16/744,574, filed Jan. 16, 2020, which is a Continuation of International Application No. PCT/JP2018/018625 filed May 15, 2018, which claims the benefit of Japanese Patent Application No. 2017-145297 filed in the Japan Patent Office on Jul. 27, 2017, each of which is incorporated by reference herein in its entirety. TECHNICAL FIELD The present disclosure relates to a secondary battery positive electrode and a technology of a secondary battery. BACKGROUND ART In recent years, as a secondary battery with high output and high energy density, a non-aqueous electrolyte secondary battery has been widely used, the battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte wherein lithium ions are transferred between the positive electrode and the negative electrode for charge and discharge. For example, Patent Literature 1 discloses a non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the above positive electrode comprises a positive electrode current collector, a positive electrode mixture layer formed on the above current collector, and an intermediate layer formed between the above positive electrode current collector and the above positive electrode mixture layer, and the above intermediate layer includes particles having a Vickers hardness of 5 GPa or more and mainly formed of a material having a thermal conductivity of 100 W/m·K or more and a specific resistance of 103 Ω·m or more. CITATION LIST Patent Literature PATENT LITERATURE 1: Japanese Unexamined Patent Application Publication No. 2016-127000 SUMMARY Providing the intermediate layer between the positive electrode current collector and the positive electrode mixture layer as in Patent Literature 1, the amount of heat generated by the battery can be suppressed, for example, even when internal short circuit occurs inside the secondary battery, as compared with the case where no intermediate layer is provided. However, in a normal state in which no internal short circuit occurs, the intermediate layer between the positive electrode current collector and the positive electrode mixture layer becomes a resistance component, and hence the resistance of the positive electrode increases. An increase in resistance of the positive electrode may cause, for example, deterioration in battery characteristics, and hence suppressing an increase in resistance of the positive electrode is an important issue. An object of the present disclosure is to provide a secondary battery comprising a secondary battery positive electrode capable of suppressing an increase in resistance of the positive electrode, and the secondary battery comprising the positive electrode, even when the intermediate layer is provided between the positive electrode current collector and the positive electrode mixture layer to suppress the amount of heat generated by the battery when internal short circuit occurs. The secondary battery positive electrode according to the first aspect of the present disclosure comprises: a positive electrode current collector having a plurality of irregularities on the surface; an intermediate layer provided on the irregular surface of the above positive electrode current collector; and a positive electrode mixture layer provided on the above intermediate layer and including a positive electrode active material, and the above intermediate layer comprises: conductive agent particles; and inorganic material particles having higher resistance than the above positive electrode active material, and the ratio of the median particle diameter of the above conductive agent particles to the average depth of the irregularities of the above positive electrode current collector and the ratio of the median particle diameter of the above inorganic material particles to the average depth of the irregularities of the above positive electrode current collector are both 5:6 or less. The secondary battery positive electrode according to the second aspect of the present disclosure comprises: a positive electrode current collector having a plurality of irregularities on the surface; an intermediate layer provided on the irregular surface of the above positive electrode current collector; and a positive electrode mixture layer provided on the above intermediate layer and including a positive electrode active material, and the above intermediate layer includes inorganic material particles having higher resistance than the above positive electrode active material, and the average depth of the irregularities of the above positive electrode current collector is 0.6 μm or more, and at least one of the projections of the irregularities of the above positive electrode current collector penetrates the interface between the above intermediate layer and the above positive electrode mi