JP-7856421-B2 - Heat transfer suppression sheet, method for manufacturing the same, and battery pack

JP7856421B2JP 7856421 B2JP7856421 B2JP 7856421B2JP-7856421-B2

Inventors

女屋尚紀
神保直幸

Assignees

イビデン株式会社

Dates

Publication Date: 20260511
Application Date: 20211217
Priority Date: 20210820

Claims (18)

It comprises first inorganic particles, a resin binder, and organic fibers. The glass transition temperature of the organic fiber is higher than that of the resin binder. Furthermore, the material comprises a first inorganic fiber and a second inorganic fiber having at least one property selected from average fiber diameter, shape, and glass transition temperature that differs from each other. The average fiber diameter of the first inorganic fiber is greater than the average fiber diameter of the second inorganic fiber. A heat transfer suppression sheet characterized in that the first inorganic fiber is linear or needle-shaped, and the second inorganic fiber is dendritic or curly.
It comprises first inorganic particles, a resin binder, and organic fibers. The glass transition temperature of the organic fiber is higher than that of the resin binder. Furthermore, the material comprises a first inorganic fiber and a second inorganic fiber having at least one property selected from average fiber diameter, shape, and glass transition temperature that differs from each other. The first inorganic fiber is an amorphous fiber, The second inorganic fiber is at least one fiber selected from amorphous fibers and crystalline fibers, each having a higher glass transition temperature than the first inorganic fiber. A heat transfer suppression sheet characterized in that the average fiber diameter of the first inorganic fiber is greater than the average fiber diameter of the second inorganic fiber.
It comprises first inorganic particles, a resin binder, and organic fibers. The glass transition temperature of the organic fiber is higher than that of the resin binder. Furthermore, the material comprises a first inorganic fiber and a second inorganic fiber having at least one property selected from average fiber diameter, shape, and glass transition temperature that differs from each other. The first inorganic particle comprises at least one selected from nanoparticles, hollow particles, and porous particles. The first inorganic fiber is an amorphous fiber, A heat transfer suppression sheet characterized in that the second inorganic fiber is at least one inorganic fiber selected from amorphous fibers and crystalline fibers, each having a higher glass transition temperature than the first inorganic fiber.
At least a portion of the aforementioned organic fibers are fused together to form a three-dimensional skeleton. The heat transfer suppression sheet according to any one of claims 1 to 3, characterized in that the resin binder is fused to a part of the skeleton and at least a part of the first inorganic particles, and at least a part of the first inorganic particles is adhered to the skeleton.
The heat transfer suppression sheet according to any one of claims 1 to 4 , characterized in that the glass transition temperature of the organic fiber is 250°C or lower.
The heat transfer suppression sheet according to any one of claims 1 to 5 , characterized in that the glass transition temperature of the resin binder is -10°C or higher.
The heat transfer suppression sheet according to any one of claims 1 to 6 , characterized in that the difference between the glass transition temperature of the resin binder and the glass transition temperature of the organic fiber is 10°C or more and 130°C or less.
The heat transfer suppression sheet according to any one of claims 1 to 7 , characterized in that the dissolution temperature of the organic fiber in water is 60°C or higher.
The heat transfer suppression sheet according to any one of claims 1 to 8 , characterized in that the average fiber length of the organic fibers is 0.5 mm or more and 10 mm or less.
With respect to the total mass of the heat transfer suppression sheet, A heat transfer suppression sheet according to any one of claims 1 to 9 , characterized in that the content of the organic fibers is 0.5% by mass or more and 12% by mass or less, and the content of the resin binder is 0.5% by mass or more and 20% by mass or less.
The heat transfer suppression sheet according to any one of claims 1 to 10 , characterized in that the resin binder comprises at least one selected from styrene-butadiene resin, acrylic resin, silicone-acrylic resin, and styrene resin.
The heat transfer suppression sheet according to any one of claims 1 to 11 , characterized in that the organic fiber comprises at least one selected from polyvinyl alcohol fiber, polyethylene fiber, nylon fiber, polyurethane fiber, and ethylene-vinyl alcohol copolymer fiber.
The heat transfer suppression sheet according to any one of claims 1 to 12 , characterized in that the first inorganic particles consist of at least one selected from oxide particles, carbide particles, nitride particles, and inorganic hydrate particles.
The heat transfer suppression sheet according to any one of claims 1 to 13, characterized in that the first inorganic fiber is a fiber containing SiO2 , and the second inorganic fiber is a fiber consisting of at least one selected from glass fiber, silica fiber, alumina fiber, alumina silicate fiber, zirconia fiber, glass wool, carbon fiber, soluble fiber, refractory ceramic fiber, aerogel composite material, magnesium silicate fiber, alkali earth silicate fiber, zirconia fiber, potassium titanate fiber, and mineral fiber.
Furthermore, the heat transfer suppression sheet according to any one of claims 1 to 14 is characterized by containing a second inorganic particle made of a metal oxide.
A method for manufacturing a heat transfer suppression sheet according to any one of claims 1 to 15 , A step of obtaining a dispersion containing the first inorganic particles, the resin binder, and the organic fibers, The process involves removing the dispersion to obtain a wet sheet, The process includes heating the wet sheet and then cooling it, A method for manufacturing a heat transfer suppression sheet, characterized in that the heating temperature for heating the wet sheet is set to be 10°C or more and 50°C or less higher than the glass transition temperature of the organic fiber.
The method for producing a heat transfer suppression sheet according to claim 16 , characterized in that the dispersion is an emulsion obtained by dispersing the resin binder in water.
A battery pack comprising a plurality of battery cells and a heat transfer suppression sheet according to any one of claims 1 to 15 , wherein the plurality of battery cells are connected in series or in parallel.

Description

This invention relates to a heat transfer suppression sheet, a method for manufacturing the same, and a battery pack having the heat transfer suppression sheet. In recent years, the development of electric vehicles (EVs) and hybrid vehicles (HEVs) powered by electric motors has been actively pursued from an environmental protection perspective. These EVs are equipped with battery packs consisting of multiple battery cells connected in series or parallel to power the electric motors used for propulsion. Furthermore, these battery cells primarily utilize lithium-ion secondary batteries, which offer higher capacity and output compared to lead-acid batteries and nickel-metal hydride batteries. However, if a battery cell experiences a rapid temperature increase and subsequent thermal runaway due to an internal short circuit or overcharging, the heat from the overheated cell can propagate to adjacent cells, potentially causing thermal runaway in those cells as well. A common method to suppress heat transfer from battery cells experiencing thermal runaway, as described above, is to interpose an insulating sheet between the battery cells. For example, Patent Document 1 discloses a heat insulating sheet for a battery pack that includes first particles composed of silica nanoparticles and second particles made of a metal oxide, with a limited content of the first particles. Patent Document 1 also states that the heat insulating sheet may include a binder consisting of at least one selected from fibers, a binder, and a heat-resistant resin. Japanese Patent Publication No. 2021-34278 Figures 1(a) to 1(c) are schematic diagrams showing the manufacturing method of a heat transfer suppression sheet according to the first embodiment of the present invention in order of steps.Figure 2 is a schematic diagram showing a heat transfer suppression sheet according to a second embodiment of the present invention.Figure 3 is a schematic diagram showing a battery pack according to an embodiment of the present invention.Figures 4(a) to 4(c) are schematic diagrams showing the manufacturing method of the test material of Comparative Example No. 1 in order of steps.Figure 5 is a schematic diagram illustrating the compression characteristics test method.Figure 6 is a schematic diagram illustrating the heat transfer test method.Figure 7 is a graph showing the relationship between compressive stress and compressive ratio for each test material, with the horizontal axis representing compressive ratio and the vertical axis representing compressive stress.Figure 8 is a graph showing the relationship between elapsed time and bottom surface temperature for each test material, with the horizontal axis representing elapsed time and the vertical axis representing bottom surface temperature.Figure 9 is a graph showing the relationship between compressive stress and thermal resistivity for each test material, with the horizontal axis representing compressive stress and the vertical axis representing thermal resistivity. The inventors of this invention have diligently studied a heat transfer suppression sheet that can solve the above problems. As a result, we found that the heat transfer suppression sheet, by having a first inorganic particle, a resin binder, and organic fibers having a higher glass transition temperature than the resin binder, can increase its resistance to pressure, and as a result, maintain excellent thermal insulation performance. Specifically, during the manufacturing of the heat transfer suppression sheet, when the wet sheet containing the above-mentioned material is heated, if the heating temperature is appropriately controlled, the organic fibers will enter a semi-molten state. Then, upon subsequent cooling, the organic fibers with high glass transition points solidify first, causing the contact points to bond and form a framework. Further cooling then causes the resin binder to solidify on the surface of the framework formed by the organic fibers, reinforcing the framework. In this way, the heat transfer suppression sheet of the present invention has a strong framework, and even when the heat transfer suppression sheet is pressed by the expansion of the battery cell, it can maintain its shape and suppress the deterioration of its thermal insulation performance. First, a method for manufacturing a heat transfer suppression sheet according to an embodiment of the present invention will be described in detail with reference to the drawings. Then, the heat transfer suppression sheet according to this embodiment and the materials constituting it will be described in detail. Furthermore, a battery pack according to this embodiment will be described. It should be noted that the present invention is not limited to the embodiments described below, and can be modified and implemented as desired without departing from the spirit of the invention. [1. Method for manufacturing a heat transfer suppression sheet] Figures 1(a) to 1(c) are s