EP-4742351-A2 - NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY

Abstract

Provided is a non-aqueous electrolyte secondary battery in which micro-short circuits are suppressed while charge and discharge cycle characteristics are improved. A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure comprises a positive electrode, a negative electrode, a separator separating the positive electrode and the negative electrode from each other, and a non-aqueous electrolyte. The positive electrode comprises a positive electrode current collector and a positive electrode mixture layer formed on a surface of the positive electrode current collector. The positive electrode mixture layer includes a first positive electrode mixture layer opposing the positive electrode current collector, and a second positive electrode mixture layer laminated on the surface of the first positive electrode mixture layer, and at least, the first positive electrode mixture layer contains fibrous carbon, and the second positive electrode mixture layer does not contain fibrous carbon having an average fiber length equal to or greater than the thickness of the second positive electrode mixture layer.

Inventors

• SAWA, SHOUICHIRO

Assignees

• Panasonic Energy Co., Ltd.

Dates

Publication Date

20260513

Application Date

20220624

Claims (4)

1. A non-aqueous electrolyte secondary battery (10), comprising: a positive electrode (11); a negative electrode (12); a separator (13) separating the positive electrode (11) and the negative electrode (12) from each other; and a non-aqueous electrolyte, wherein the positive electrode (11) has a positive electrode current collector (30) and a positive electrode mixture layer (32, 34) formed on a surface of the positive electrode current collector (30), the positive electrode mixture layer (32, 34) includes a first positive electrode mixture layer (32) facing the positive electrode current collector (30) and a second positive electrode mixture layer (34) stacked on a surface of the first positive electrode mixture layer (32), at least the first positive electrode mixture layer (32) contains a fibrous carbon, and the second positive electrode mixture layer (34) does not contain the fibrous carbon having an average fiber length of greater than or equal to a thickness of the second positive electrode mixture layer (34).
2. The non-aqueous electrolyte secondary battery (10) according to claim 1, wherein an average fiber length of the fibrous carbon contained in the first positive electrode mixture layer (32) is greater than or equal to a thickness of the first positive electrode mixture layer (32).
3. The non-aqueous electrolyte secondary battery (10) according to claim 1 or 2, wherein the second positive electrode mixture layer (34) does not contain the fibrous carbon.
4. The non-aqueous electrolyte secondary battery (10) according to any of claims 1 to 3, wherein the thickness of the second positive electrode mixture layer (34) is greater than or equal to 5% and less than or equal to 10% relative to a total thickness of the positive electrode mixture layer (34).

Description

TECHNICAL FIELD The present disclosure relates to a non-aqueous electrolyte secondary battery. BACKGROUND ART An electrode of a non-aqueous electrolyte secondary battery is commonly composed of a metallic current collector and a mixture layer formed on a surface of the current collector. From the viewpoints of improvement of charge-discharge cycle characteristics and the like, it has been investigated to use fibrous carbon such as carbon nanotube (CNT) as a conductive agent in a positive electrode mixture layer in recent years. Patent Literature 1 discloses art of using CNT having a diameter of greater than or equal to 0.5 nm and less than or equal to 10 nm and a length of greater than or equal to 10 µm as a conductive agent in a positive electrode for a purpose of increasing a capacity of a battery and inhibiting decrease in the capacity with high output. CITATION LIST PATENT LITERATURE PATENT LITERATURE 1: Japanese Unexamined Patent Application Publication No. 2012-221672 SUMMARY TECHNICAL PROBLEM However, the present inventors have made intensive investigation, and consequently found that containing long fibrous carbon in the positive electrode mixture layer causes the fibrous carbon to directly connect a positive electrode current collector and a surface of the positive electrode mixture layer, which may cause a minute short-circuit. The art disclosed in Patent Literature 1 does not consider the minute short-circuit, and still has a room for improvement. It is an object of the present disclosure to provide a non-aqueous electrolyte secondary battery with inhibited minute short-circuit while improving charge-discharge cycle characteristics. SOLUTION TO PROBLEM A non-aqueous electrolyte secondary battery of an aspect of the present disclosure comprises: a positive electrode; a negative electrode; a separator separating the positive electrode and the negative electrode from each other; and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer formed on a surface of the positive electrode current collector, and the positive electrode mixture layer contains a fibrous carbon having a length of greater than or equal to 50% of a thickness of the positive electrode mixture layer, and the fibrous carbon is not exposed to a surface of the positive electrode mixture layer. A non-aqueous electrolyte secondary battery of another aspect of the present disclosure comprises: a positive electrode; a negative electrode; a separator separating the positive electrode and the negative electrode from each other; and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer formed on a surface of the positive electrode current collector, the positive electrode mixture layer includes a first positive electrode mixture layer facing the positive electrode current collector and a second positive electrode mixture layer stacked on a surface of the first positive electrode mixture layer, at least the first positive electrode mixture layer contains a fibrous carbon, and the second positive electrode mixture layer does not contain the fibrous carbon having an average fiber length of greater than or equal to a thickness of the second positive electrode mixture layer. ADVANTAGEOUS EFFECT OF INVENTION According to the non-aqueous electrolyte secondary battery of the present disclosure, the minute short-circuit may be inhibited while improving the charge-discharge cycle characteristics. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an axial sectional view of a non-aqueous electrolyte secondary battery of an example of an embodiment.FIG. 2 is a sectional view of a positive electrode of an example of the embodiment. DESCRIPTION OF EMBODIMENTS Hereinafter, an example of the embodiment of a non-aqueous electrolyte secondary battery according to the present disclosure will be described in detail with reference to the drawings. Hereinafter, a cylindrical battery housing a wound electrode assembly in a cylindrical exterior will be exemplified, but the shape of the exterior is not limited to the cylindrical shape, and may be, for example, a rectangular shape, a coin shape, or the like. The exterior may be a pouch composed of a laminated sheet including a metal layer and a resin layer. The electrode assembly may be a stacked electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator interposed therebetween. FIG. 1 is an axial sectional view of a cylindrical secondary battery 10 of an example of the embodiment. In the secondary battery 10 illustrated in FIG. 1, an electrode assembly 14 and a non-aqueous electrolyte (not illustrated) are housed in an exterior 15. The electrode assembly 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interpos