US-12626928-B2 - Binder storage container for secondary battery and binder product for secondary battery

US12626928B2US 12626928 B2US12626928 B2US 12626928B2US-12626928-B2

Abstract

Provided are a binder storage container for a secondary battery and a binder product for a secondary battery that enable long-term storage of even a binder composition that can inhibit aggregate formation while also improving adhesiveness of a functional layer. The binder storage container for a secondary battery includes an accommodating part where a binder composition for a secondary battery is to be accommodated. The accommodating part is obtained through shaping of a resin composition that contains a polyolefin resin having a weight-average molecular weight of 400,000 or more as a main component. The accommodating part has a wall thickness of 2.5 mm or more and has a durability of 72 hours or more in an environmental stress cracking test in accordance with JIS K-6761 using dialkyl sodium sulfosuccinate aqueous solution of 1.5 mass % in concentration.

Inventors

Yutaka MARUHASHI

Assignees

ZEON CORPORATION

Dates

Publication Date: 20260512
Application Date: 20230901
Priority Date: 20220930

Claims (8)

1 . A binder storage container for a secondary battery comprising an accommodating part where a binder composition for a secondary battery is to be accommodated, wherein the accommodating part is obtained through shaping of a resin composition that contains a polyolefin resin having a weight-average molecular weight of 400,000 or more as a main component, the accommodating part has a wall thickness of 2.5 mm or more, and the accommodating part has a durability of 72 hours or more in an environmental stress cracking test in accordance with JIS K-6761 using dialkyl sodium sulfosuccinate aqueous solution of 1.5 mass % in concentration.
2 . The binder storage container for a secondary battery according to claim 1 , wherein the polyolefin resin contained in the resin composition has a molecular weight distribution, expressed by weight-average molecular weight/number-average molecular weight, of not less than 9 and not more than 13.
3 . The binder storage container for a secondary battery according to claim 1 , wherein the weight-average molecular weight of the polyolefin resin is less than 500,000.
4 . The binder storage container for a secondary battery according to claim 1 , wherein the polyolefin resin is high-density polyethylene.
5 . The binder storage container for a secondary battery according to claim 1 , wherein the resin composition is an additive-free polyolefin resin.
6 . The binder storage container for a secondary battery according to claim 1 , wherein an inner wall surface of the accommodating part has undergone hydrophobization treatment.
7 . A binder product for a secondary battery comprising: the binder storage container for a secondary battery according to claim 1 ; and a binder composition accommodated in the accommodating part of the binder storage container for a secondary battery, wherein the binder composition has a surface tension of not less than 20 mN/m and not more than 60 mN/m.
8 . The binder product for a secondary battery according to claim 7 , wherein the binder composition contains a dialkyl sulfosuccinic acid ester salt.

Description

TECHNICAL FIELD The present disclosure relates to a binder storage container for a secondary battery and a binder product for a secondary battery. BACKGROUND Secondary batteries such as lithium ion secondary batteries have characteristics such as compact size, light weight, high energy-density, and the ability to be repeatedly charged and discharged, and are used in a wide range of applications. A secondary battery generally includes battery members such as electrodes (positive electrode and negative electrode) and a separator that isolates the positive electrode and the negative electrode from each other. A battery member of a secondary battery may be a member that includes a functional layer containing a binder (binding material) and optionally containing particles compounded so as to cause the battery member to display a desired function (hereinafter, referred to as “functional particles”). Specifically, a separator that includes an adhesive layer containing a binder or a heat-resistant layer containing a binder and non-conductive particles as functional particles on a separator substrate, for example, may be used as a separator of a secondary battery. Moreover, an electrode that includes an electrode mixed material layer containing a binder and electrode active material particles as functional particles on a current collector or an electrode that further includes an adhesive layer or heat-resistant layer such as described above on an electrode substrate including an electrode mixed material layer on a current collector may be used as an electrode of a secondary battery. A binder used to form a battery member is conventionally stored in a container in the form of a binder composition having the binder dissolved or dispersed in a solvent such as water (for example, refer to Patent Literature (PTL) 1). It is desirable for a functional layer to display excellent adhesiveness in order to provide good close adherence with a substrate that supports the functional layer. Accordingly, in recent years, the surface tension of a binder composition has been lowered so as to inhibit aggregate formation in the binder composition after long-term storage while also improving adhesiveness of a functional layer with the aim of causing good close adherence of the functional layer to a substrate. For example, PTL 2 discloses the reduction of surface tension of a binder composition such that the surface tension thereof is controlled to within a specific range and also discloses hydrophobization coating of the inside of a container. CITATION LIST Patent Literature PTL 1: WO2015/029835A1PTL 2: WO2022/071523A1 SUMMARY Technical Problem The inventor studied the use of various emulsifiers with the aim of achieving even better control of the surface tension of a binder composition. However, the inventor's studies revealed that in a situation in which a binder composition that contains an emulsifier is loaded into a container made of a resin and is then stored for a long time (for example, 1.5 years to 2 years) as a binder product, the emulsifier in the binder product permeates the container and thereby causes degradation of the container (i.e., reduces environmental stress cracking resistance of the container), which can result in damage of the container and leakage of contents (i.e., the binder composition) from the container. Accordingly, an object of the present disclosure is to provide a binder storage container for a secondary battery and a binder product for a secondary battery that enable long-term storage of even a binder composition that can inhibit aggregate formation while also improving adhesiveness of a functional layer. Solution to Problem The inventor conducted diligent investigation with the aim of solving the problem set forth above. The inventor discovered that by producing an accommodating part of a binder storage container for a secondary battery using a resin composition that contains a polyolefin resin having a weight-average molecular weight of not less than a specific value as a main component, and by setting the wall thickness of the accommodating part as not less than a specific value, the accommodating part can display a specific durability in a specific environmental stress cracking test, and environmental stress cracking properties of the container can be improved. In this manner, the inventor completed the present disclosure. Specifically, with the aim of advantageously solving the problem set forth above, [1] a presently disclosed binder storage container for a secondary battery comprises an accommodating part where a binder composition for a secondary battery is to be accommodated, wherein the accommodating part is obtained through shaping of a resin composition that contains a polyolefin resin having a weight-average molecular weight of 400,000 or more as a main component, the accommodating part has a wall thickness of 2.5 mm or more, and the accommodating part has a durability of 72 hours or more