CN118044045A

CN118044045A - Heat insulating material for battery and nonaqueous electrolyte secondary battery

Info

Publication number: CN118044045A
Application number: CN202280066291.7A
Authority: CN
Inventors: 宇井丈裕; 佐佐木集; 福家一浩; 川上真帆
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-09-30
Filing date: 2022-09-27
Publication date: 2024-05-14

Abstract

The heat insulating material for a battery according to the present invention is provided by laminating a compression adjustment layer and a heat insulating layer, wherein the ratio of the thickness of the compression adjustment layer to the thickness of the heat insulating layer exceeds 0.5 and is less than 4.5, and the compressive stress when compressed and strained at any ratio in the range of 25 to 70% in the thickness direction is 0.34 to 3.45MPa with respect to the thickness of the compression adjustment layer before compression.

Description

Heat insulating material for battery and nonaqueous electrolyte secondary battery

Technical Field

The present invention relates to a heat insulating material for a battery and a nonaqueous electrolyte secondary battery.

Background

Nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used as power sources for electric vehicles such as hybrid cars and electric cars, portable electronic devices such as portable terminals, portable telephones and notebook-type personal computers, and wearable devices. In general, a nonaqueous electrolyte secondary battery is provided by stacking a plurality of battery cells each including a positive electrode, a negative electrode, and a nonaqueous electrolyte. In the nonaqueous electrolyte secondary battery, expansion and contraction of the battery cells are generated by repeated charge and discharge, and therefore, the battery cells are intermittently heated while contact between adjacent battery cells is suppressed, and thus, a battery insulating material is provided between the battery cells.

As a battery heat insulating material used for a nonaqueous electrolyte secondary battery, for example, a separator is disclosed that is configured in a corrugated plate-like spring, that functions as a passage for a cooling medium, and that elastically deforms in response to deformation of the battery, and that has an elastic characteristic that maintains the load of the battery at a substantially constant level (for example, see patent literature 1).

Prior art literature

Patent literature

Patent document 1 Japanese patent laid-open No. 2000-48867

Patent document 2 Canadian patent application publication 1190279

Disclosure of Invention

Problems to be solved by the invention

Here, as the capacity of the battery cell increases, the amount of deformation of expansion and contraction accompanying charge and discharge of the battery cell, and the possibility of thermal runaway occurring when the battery cell excessively generates heat, increase. Since the separator of patent document 1 is composed of a spring formed in a corrugated plate shape, if the amount of deformation due to expansion of the battery cells increases, the separator cannot be sufficiently deformed, and there is a problem in that the cushioning property cannot be exhibited. Further, there is a problem in that the thermal runaway of the battery cell cannot be sufficiently performed.

As a reference value for the pressure at which the lithium ion secondary battery operates with high efficiency, for example, patent document 2 describes that "the efficiency of LIB is improved compared with no pressure by pressurizing at 50psi (0.34 MPa) to 500psi (3.45 MPa)".

An object of one embodiment of the present invention is to provide a heat insulating material for a battery that can exhibit excellent cushioning properties for expansion of a battery cell and can have high heat insulating properties.

Means for solving the problems

One embodiment of the heat insulating material for a battery according to the present invention is provided by laminating a compression adjustment layer and a heat insulating layer,

The ratio of the thickness of the compression adjustment layer to the thickness of the heat insulation layer exceeds 0.5 and is less than 4.5,

The compressive stress when compressed and strained at any ratio in the range of 25 to 70% in the thickness direction is 0.34 to 3.45MPa with respect to the thickness of the compression adjustment layer before compression.

ADVANTAGEOUS EFFECTS OF INVENTION

The heat insulating material for a battery according to the present invention can exhibit excellent cushioning properties for expansion of battery cells and can have high heat insulating properties.

Drawings

Fig. 1 is a perspective view of a heat insulating material for a battery according to an embodiment of the present invention.

FIG. 2 is a sectional view of the I-I of FIG. 1.

Fig. 3 is a plan view of fig. 1.

Fig. 4 is a diagram showing an example of a relationship between compression time and residual stress.

Fig. 5 is a cross-sectional view showing an example of another structure of the battery insulating material.

Fig. 6 is a cross-sectional view showing an example of another structure of the battery insulating material.

Fig. 7 is a cross-sectional view showing an example of another structure of the battery insulating material.

Fig. 8 is a perspective view showing an example of a lithium ion secondary battery.

Fig. 9 is a partial sectional view of a lithium ion secondary battery.

Fig. 10 is a graph showing the relationship between the stress relaxation rate (%) and the elapsed time of the battery thermal insulation material of example 28.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. In the drawings, the same reference numerals are given to the same constituent elements, and overlapping description is omitted to facilitate understanding of the description. In addition, the scale of each component in the drawings is sometimes different from real time. In the present specification, "to" indicating a numerical range means that the numerical values described before and after the numerical range are included as a lower limit value and an upper limit value unless otherwise specified.

< Heat insulation Material for Battery >)

A battery thermal insulation material according to an embodiment of the present invention will be described. Fig. 1 is a perspective view of a battery thermal insulation material according to the present embodiment, fig. 2 is a sectional view of fig. 1 taken along line I-I, and fig. 3 is a plan view of fig. 1. As shown in fig. 1 and 2, the heat insulating material 1 for a battery according to the present embodiment is provided by laminating a compression adjustment layer 10 and a heat insulating layer 20 in this order, and may include a coating layer 30 that covers the compression adjustment layer 10 and the heat insulating layer 20. The battery insulating material 1 is formed in a sheet shape. As shown in fig. 3, the battery insulating material 1 is formed in a substantially rectangular shape in a plan view.

In the present specification, the thickness direction (vertical direction) of the battery thermal insulation material 1 is referred to as the Z-axis direction, and the lateral direction (horizontal direction) orthogonal to the thickness direction is referred to as the X-axis direction and the Y-axis direction. The heat insulating layer 20 side in the Z-axis direction is set to +z-axis direction, and the compression adjustment layer 10 side is set to-Z-axis direction. In the following description, for convenience of description, the +z axis direction is referred to as up or above, and the-Z axis direction is referred to as down or below, and does not indicate a general up-down relationship.

The present inventors studied about the relationship between the thickness of the compression adjustment layer 10 and the thickness of the heat insulation layer 20 of the battery heat insulation material 1 and the cushioning property when the compression adjustment layer 10 is compressed, when the battery heat insulation material 1 is applied to a nonaqueous electrolyte secondary battery, and further, when the cushioning of expansion of a battery cell and the heat insulation of heat generated by the battery cell are appropriately performed for the increase in capacity. The inventors of the present application have found that, when the ratio of the thickness of the compression adjustment layer 10 to the thickness of the heat insulating layer 20 is set to be within a range of more than 0.5 and less than 4.5, and the compression adjustment layer 10 is compressed in any of a range of 25% to 70% in the thickness direction with respect to the thickness before compression, the compressive stress when strained is within a range of 0.34MPa to 3.45MPa, the battery heat insulating material 1 can be deformed flexibly against stress from the outside, and heat insulating properties can be improved. Thus, the battery insulating material 1 can have high heat insulating properties while improving the cushioning properties against expansion of the battery cells.

The thickness of the compression adjustment layer 10 and the heat insulation layer 20 is measured at an arbitrary place by measuring the cross sections of the compression adjustment layer 10 and the heat insulation layer 20. When the sections of the compression adjustment layer 10 and the heat insulation layer 20 are measured at a predetermined number of places, an average value of the thicknesses at these measured places may be used.

The compressive stress of the compression adjustment layer 10 may be measured by a precision universal tester, and the compressive stress when the test piece is compressed at a predetermined compression speed (for example, 0.5 mm/min) with respect to the thickness before compression at any ratio in the range of 25% to 70% in the thickness direction may be measured.

The heat insulating property is a property of suppressing heat conduction. The heat insulation can be evaluated by measuring the thermal conductivity. Thermal conductivity was measured according to JIS A1412-1: method for measuring thermal resistance and thermal conductivity of 2016 thermal insulation material-part 2: the thermal conductivity was measured at 80℃and 2MPa by a thermal flow meter method (HFM method). The battery heat insulating material 1 was cut into a predetermined size (for example, 20mm×20 mm) to prepare a sample, and a reference sample was prepared. As a reference sample, for example, a calcium silicate plate ("Hirac", manufactured by A & A MATERIAL, thickness: 5mm, thermal conductivity: 0.22W/(m.K)) or the like can be used. Next, on the lower plate surface of the air pressure press, the members were held in order of the 1 st thermocouple, the aluminum plate, the battery insulating material 1, the aluminum plate, the 2 nd thermocouple, the reference sample, and the 3 rd thermocouple from the top, and were brought into close contact. The pressing may be performed after the upper plate is heated to a predetermined temperature (for example, 80 ℃) and the lower plate is heated to a predetermined temperature (for example, 35 ℃) so that the load of the press becomes a predetermined load (for example, 800N (equivalent to 2 MPa)). The measurement is continued in a state of being heated and pressurized until the detected temperature of each thermocouple becomes stable. The term "stable temperature" may mean that the temperature change before and after 10 minutes falls within a predetermined range (for example, within.+ -. 0.1 ℃). The thermal conductivity k1 of the battery thermal insulation material 1 is obtained by the following formula (I) with reference to the thermal conductivity and thickness of the sample from the detected temperature of each thermocouple after temperature stabilization and the thickness of the battery thermal insulation material 1 at the time of compression.

k1＝k2×(L1×ΔT1)/(L2×ΔT2)···(I)

(Wherein K1 is the thermal conductivity [ W/(m.K) ] of the heat insulating material for battery 1, K2 is the thermal conductivity [ W/(m.K) ] of the reference sample, L1 is the thickness of the heat insulating material for battery at the time of pressurization, L2 is the thickness of the reference sample, deltaT 1 is the temperature difference between the temperature of the 2 nd thermocouple and the temperature of the 3 rd thermocouple, deltaT 2 is the temperature difference between the temperature of the 1 st thermocouple and the temperature of the 2 nd thermocouple.)

If the thickness of the battery insulating material 1 during compression is difficult to measure during compression, the thickness can be calculated from the thickness of the battery insulating material before compression and the compression deformation rate during compression under a predetermined load (for example, 800N (equivalent to 2 MPa)).

The cushioning properties were measured by a precision universal tester, and the deformation distances were measured when the test body was compressed at a predetermined compression rate (for example, 0.5 mm/min) and the compression stress was 0.34MPa and 3.45 MPa. Further, the displacement amount (displacement range of 0.34MPa to 3.45 MPa) in which the compressive stress is in the range of 0.34MPa to 3.45MPa was calculated by the following formula (II). The displacement can be evaluated as a buffer property in a displacement region of 0.34MPa to 3.45 MPa. The buffer property in the displacement range of 0.34 to 3.45MPa is improved, and thus the lithium ion secondary battery having the battery insulating material according to the present embodiment in the displacement range of 0.34 to 3.45MPa can improve the charge/discharge efficiency.

Displacement range [% ] = (deformation distance at 3.45 MPa/thickness of test body) ×100% - (deformation distance at 0.34 MPa/thickness of test body) ×100% · (II) of 0.34 MPa-3.45 MPa displacement range [% ] =

Each member constituting the battery insulating material 1 will be described.

As shown in fig. 1, the compression adjustment layer 10 may be formed in a sheet shape, and may be formed to have an appropriate flexibility according to the hardness of the heat insulation layer 20. That is, the compression adjustment layer 10 may be easily compression-deformed compared to the heat insulation layer 20 or difficult to be compression-deformed compared to the heat insulation layer 20 according to the hardness of the heat insulation layer 20.

When the battery insulating material 1 is fixed in the housing with being sandwiched between the battery cells to constitute the nonaqueous electrolyte secondary battery, one of the battery cells excessively generates heat during operation of the nonaqueous electrolyte secondary battery, and the battery cell expands, and the surface thereof protrudes toward the battery insulating material 1, thereby applying stress to the battery insulating material 1. Therefore, depending on the hardness of the heat insulating layer 20, one of the compression adjustment layer 10 and the heat insulating layer 20 is more likely to be compressively deformed than the other. That is, in the case where the compression adjustment layer 10 is more likely to be compressively deformed than the heat insulating layer 20, the compression adjustment layer 10 is more likely to be deformed than the heat insulating layer 20, and therefore, the compression adjustment layer 10 follows the deformation of the surface of the battery cell and is more likely to be deformed. When the heat insulating layer 20 is more likely to be compressively deformed than the compression adjustment layer 10, the heat insulating layer 20 is more likely to be deformed than the compression adjustment layer 10, and therefore, the heat insulating layer 20 is more likely to be deformed following the deformation of the surface of the battery cell. Therefore, by including the compression adjustment layer 10 and the heat insulating layer 20, the battery pack heat insulating material 1 can suppress the expansion of the battery cells excessively, and can effectively suppress the occurrence of breakage or the like of the battery cells.

For example, in the case where the battery insulating material is disposed in a state of being sandwiched between the battery cells only from the heat insulating layer that is difficult to compress and deform, if excessive heat generation occurs in the battery cells, the battery cells cannot expand toward the battery insulating material, and therefore the battery cells may be broken and broken. In contrast, the compression adjustment layer 10 and the heat insulating layer 20 are disposed between the battery cells, and therefore, the surface of the battery cells can allow one of the compression adjustment layer 10 and the heat insulating layer 20 to deform and expand toward the other of the compression adjustment layer 10 and the heat insulating layer 20, and breakage of the battery cells and the like can be reduced.

The compression stress at the time of compression at any ratio in the range of 25% to 70% in the thickness direction with respect to the thickness of the compression adjustment layer 10 before compression is 0.34MPa to 3.45MPa, preferably 1.00MPa to 3.00MPa, and more preferably 1.50MPa to 2.50MPa. If the compressive stress of the compression adjustment layer 10 is less than 0.34MPa, the cushioning property of the compression adjustment layer 10 is insufficient, and thus a certain load cannot be stably applied to the battery cell. Further, when the compression adjustment layer 10 is deformed, the thickness of the deformed portion may be reduced, and heat insulation may be reduced. On the other hand, if the compressive stress of the compression adjustment layer 10 is higher than 3.45MPa, the expansion of the battery cells may not be sufficiently buffered, and the battery cells may be broken.

After the compression adjustment layer 10 is assembled in the nonaqueous electrolyte secondary battery at a compression stress at a compression ratio in the range of 25% to 70% in the thickness direction with respect to the thickness before compression, the compression adjustment layer changes in compression stress due to a relaxation phenomenon by applying stress to the battery heat insulating material from the start of use to the end of use. Accordingly, the compressive stress may be a residual stress in which the compressive stress is compressed at any ratio within a range of 25% to 70% in the thickness direction with respect to the thickness before compression, so that the state of the compressive stress is maintained in a state of being set for a period of time of more than 0 hours and not more than 87600 hours (assuming that the battery is discarded for 10 years from the start of use). The residual stress was measured by cutting the compression-adjusting layer or the heat-insulating layer to a predetermined thickness of 10mm square, using a precision universal tester (AGS-5 kNX, manufactured by Shimadzu corporation), compressing the test body at a compression rate of 0.5mm/min, stopping compression at a point of time when the test body is compressed at any rate within a range of 25% to 70%, and standing for a time of more than 0 hours and not more than 87600 hours while maintaining the compression rate. Then, the stress in a state of being left for a time period of more than 0 and not more than 87600 hours was measured, and the stress was set as a residual stress.

When the standing time is difficult for a long period of time, for example, the residual stress in a state of being left standing for a time of more than 20 hours and not more than 87600 hours can be estimated by the following method.

((Example of method of estimating residual stress))

A test body was prepared by cutting the compression-adjusting layer or the heat-insulating layer to a predetermined thickness of 10mm square. The test body was compressed at a compression rate of 0.5mm/min by using a precision universal tester (manufactured by automatic plotter AGS-5kNX, manufactured by shimadzu corporation), and the compression was stopped at the time when the load became 100N, and the measurement of the compressive stress was started until the lapse of 20 hours, and the compressive stress was continuously measured at regular intervals, for example, every 1 minute, every 10 minutes, or every 1 hour. The obtained compressive stress value at intervals of time was divided by 100N as in the following formula (III), and was set as a stress relaxation rate (%).

Stress Slow and rate (%) = stress per elapsed time (N)/100 n·· (III)

The relationship between the elapsed time and the stress relaxation rate may be created by Excel of the microsoft corporation table calculation software. The graph can be created by arranging and selecting the elapsed time and stress relaxation rate in a table, and inserting the selected values in the order of the graph and the scatter diagram. Next, the relaxing curve displayed in the drawing is selected, the context menu is opened, and the addition (R) of the approximate curve is selected. An approximate expression suitable for the stress relaxation curve is selected from the options of the approximate curve, and a check (check) is added to "the expression (E) in the figure". By substituting the time of more than 20 hours and not more than 87600 hours into the equation (x) of the expressed approximate curve, the stress relaxation rate (%) can be obtained.

Finally, as in the following formula (IV), by multiplying the obtained stress relaxation rate by the compressive stress at any one of the compression ratios in the range of 25% to 70% in the thickness direction with respect to the thickness before compression, an estimated value (MPa) of the residual stress at a time of more than 20 hours and 87600 hours or less can be obtained.

Estimated value of residual stress (MPa) =stress Slow and rate (%) x compressive stress (MPa) ·· (IV)

The thermal conductivity at 80℃and 2MPa of the compression adjustment layer 10 may be higher than that of the heat insulation layer 20, and for example, the thermal conductivity at 2MPa is preferably 0.04W/(mK) to 0.4W/(mK).

The thermal conductivity at 80℃and 2MPa of the compression adjustment layer 10 is preferably 20% or more of the thermal conductivity at 80℃and 2MPa of the heat insulation layer 20.

The thermal conductivity of the compression adjustment layer 10 at 80℃and 2MPa can be measured by the method described in "JIS A1412-1: method for measuring thermal resistance and thermal conductivity of 2016 thermal insulation material-part 2: the heat flow meter method (HFM method).

The material of the compression adjustment layer 10 is not particularly limited as long as it can easily undergo compression deformation to exert cushioning properties. As the compression adjustment layer 10, for example, a molded body of fiber, rubber, thermoplastic resin, or the like can be used.

The fiber molded body (fiber molded body) is obtained by molding a fiber. Examples of the fibers include felts made of inorganic fibers such as glass wool and rock wool, cellulose fibers, polyester, polypropylene, and the like. In order to set the compressive stress in the range of 0.34MPa to 3.45MPa when the compression adjustment layer 10 is compressed at any ratio of 25% to 70% in the thickness direction with respect to the thickness before compression, the mass of the fiber used for forming the compression adjustment layer 10 is preferably 140kg/m ³～533kg/m³. Further, among the fibers, glass wool is preferably cured by a thermosetting resin because of an increased compressive stress. As the glass wool monomer, a fiber diameter of 3 μm to 13 μm and a fiber length of 5mm to 200mm are preferable.

The rubber molded body (rubber molded body) is obtained by molding rubber. Examples of the rubber include styrene-butadiene rubber, chloroprene rubber, isoprene rubber, butyl rubber, ethylene propylene rubber, nitrile rubber, silicone rubber, fluoro rubber, acrylic rubber, urethane rubber, polysulfide rubber, and epichlorohydrin rubber. The number of these may be 1 alone, and 2 or more may be used in combination. The Asker C hardness of the rubber molded article is preferably 53 or less. If the Asker C hardness is higher than 53, there is a possibility that the heat-insulating layer will be broken upon compression. In addition, asker C hardness is a press head of Asker rubber durometer type C, based on JIS K7312:1996, by a method for measuring hardness.

A molded body of a thermoplastic resin (resin molded body) is obtained by molding a thermoplastic resin or a thermosetting resin.

Examples of the thermoplastic resin include polyurethane, polyethylene, polystyrene, polypropylene, and ethylene-vinyl acetate copolymer. The number of these may be 1 alone, and 2 or more may be used in combination. The resin molded article is preferably a resin foam formed by foam molding in which independent or continuous cells are formed using the thermoplastic resin. Since the resin foam has bubbles in the interior and the surface, the resin foam can be easily deformed by compression to exert cushioning properties. In order to set the compressive stress in the range of 0.34MPa to 3.45MPa when the resin foam is compressed at a rate of 25% to 70% in the thickness direction with respect to the thickness of the resin foam before compression, it is preferable that the unit structure constituting the resin foam is a single-cell structure, the material used for forming the resin foam has a crosslinked structure, and the material has a compressive elastic modulus of 700MPa to 72000MPa as a single body. In order to set the compressive stress in the range of 0.34MPa to 3.45MPa when the resin molded body is compressed at any ratio of 25% to 70% in the thickness direction with respect to the thickness of the resin molded body before compression, a waveform in which stress is dispersed and bending is difficult is preferable to the reinforcing structure of the resin molded body, compared with a rectangular cross-sectional shape in which stress is easily concentrated. In addition, in the case where the lithium ion battery burns, if the buffer layer burns, the heat-insulating property is lowered, and therefore, the heat-insulating layer preferably has flame retardancy (for example, UL 94V-0 of UL flame retardant standards), and more preferably has incombustibility.

Examples of the thermosetting resin include urethane resins, phenol resins, urea resins, melamine resins, unsaturated polyesters, epoxy resins, and silicone resins. The number of these may be 1 alone, and 2 or more may be used in combination.

The thickness of the compression adjustment layer 10 is preferably 1.0mm to 8.8mm, more preferably 1.5mm to 7.5mm, and even more preferably 2.0mm to 5.0mm. If the thickness of the compression adjustment layer 10 is 1.0mm to 8.8mm, the stress applied to the battery cells during expansion of the battery cells can be sufficiently absorbed when the battery pack is configured such that the battery thermal insulation material 1 is fixed in the casing in a state of being sandwiched between the battery cells.

The ratio of the thickness of the compression adjustment layer 10 to the thickness of the heat insulation layer 20 exceeds 0.5 and is less than 4.5. If the ratio of the thickness of the compression adjustment layer 10 to the thickness of the heat insulation layer 20 is 0.5 or less, the strain from the outside cannot be sufficiently absorbed. Therefore, when the battery insulating material 1 is fixed in the casing with being sandwiched between the battery cells to construct the nonaqueous electrolyte secondary battery, there is a possibility that the expansion of the battery cells generated during charging of the battery cells is not absorbed, and the stress applied to the battery cells becomes too high to damage the battery cells. If the ratio of the thickness of the compression adjustment layer 10 to the thickness of the heat insulation layer 20 is 4.5 or more, the compression adjustment layer 10 becomes excessively thick compared to the heat insulation layer 20. Since the compression adjustment layer 10 has a higher thermal conductivity than the heat insulating layer 20, the heat insulating material 1 for a battery has a lower heat insulating property. Therefore, when the battery insulating material 1 is fixed in the casing with being sandwiched between the battery cells to constitute the nonaqueous electrolyte secondary battery, the battery insulating material 1 cannot sufficiently insulate heat generated when the battery cells thermally expand.

In the case where the nonaqueous electrolyte secondary battery is configured by fixing the battery heat insulating material 1 in the casing while being sandwiched between the battery cells, the shape of the compression adjustment layer 10 is not particularly limited as long as it is a shape that is suitable for deformation in accordance with expansion and contraction of the battery cells, and is preferably a plate shape, for example. In this case, the compression adjustment layer 10 may have a rectangular shape (for example, a polygonal shape such as a quadrangle), a circular shape, an elliptical shape, or other shapes in a plan view.

As shown in fig. 2, the heat insulating layer 20 is provided on the upper surface 10a of the compression adjustment layer 10. The heat insulating layer 20 is formed in a sheet shape, and can have a function of suppressing heat conduction in the thickness direction with respect to the heat insulating material 1 for a battery, that is, heat insulating property, flexibility, and cushioning property.

The thermal conductivity of the heat insulating layer 20 is not particularly limited as long as it is lower than that at 80℃and 2MPa of the compression adjustment layer 10, and the thermal conductivity of the heat insulating layer 20 at 23℃is preferably 0.3W/(mK) or less. If the thermal conductivity of the heat insulating layer 20 is equal to or less than the upper limit value, the heat insulating property can be exhibited. The lower limit value of the thermal conductivity of the heat insulating layer 20 is not limited, and may be, for example, 0.010W/k·m or more. The thermal conductivity of the heat insulating layer 20 can be measured in the same manner as the thermal conductivity of the compression adjustment layer 10.

The thermal resistance of the heat insulating layer 20 is not particularly limited, but is preferably 0.025 (K.m ²)/W or more. The upper limit of the thermal resistance of the heat insulating layer 20 is not limited, and may be, for example, 0.1 (k·m ²)/W or less.

The compressive stress of the heat insulating layer 20 can be appropriately set to any magnitude depending on the hardness of the heat insulating layer 20, and is preferably, for example, 0.25MPa to 14.00MPa. If the compressive stress of the heat insulating layer 20 is within the above-described preferable range, a certain load can be applied to the compression adjustment layer 10 and the battery cell, and the expansion of the battery cell can be sufficiently buffered, so that the breakage of the battery cell can be suppressed.

When the heat insulating layer 20 is harder than the compression adjustment layer 10, the compression stress of the heat insulating layer 20 is higher in a low compression region (for example, a displacement region of 0.34MPa to 3.45 MPa) than that of the compression adjustment layer 10. When the heat insulating layer 20 is softer than the compression adjustment layer 10, the compression stress of the heat insulating layer 20 is lower in the low compression domain than that of the compression adjustment layer 10.

The compressive stress of the heat insulating layer 20 was obtained in the same manner as the above-described compression adjustment layer 10.

The compressive stress of the heat insulating layer 20 may be the compressive stress at the time of compression at any ratio in the range of 25% to 70% in the thickness direction of the heat insulating layer 20 with respect to the thickness before compression, similarly to the compression adjustment layer 10.

The thickness of the heat insulating layer 20 can be set appropriately, and is preferably, for example, 0.8mm to 5.0mm. If the thickness of the heat insulating layer 20 is within the above-described preferable range, the heat insulating property can be improved, and the size of the battery heat insulating material 1 can be suppressed from increasing.

The heat insulating layer 20 is not particularly limited as long as it is a molded body having a desired heat insulating property, and is preferably a porous body. The porous body is not particularly limited, and examples thereof include a fibrous body and a foam.

The fiber body contains fibers. The fiber body can be produced by either a dry method or a wet method.

The fibers included in the fibrous body are not particularly limited as long as they can be applied to the heat-insulating layer 20, and at least one of inorganic fibers and organic fibers can be used, and preferably inorganic fibers are included.

The inorganic fiber is not particularly limited, and examples thereof include silica fiber, glass fiber, alumina fiber, silica-alumina-magnesia fiber, biosoluble inorganic fiber, glass fiber, zirconia fiber, alkaline earth silicate fiber, alkali Earth Silicate (AES) wool, glass wool, rock wool, basalt fiber, and the like. The number of these may be 1 alone, and 2 or more may be used in combination.

The organic fiber is not particularly limited, and examples thereof include aramid fiber, polyester fiber, polyethylene fiber, polypropylene fiber, polyvinyl chloride fiber, fluororesin fiber, nylon fiber, rayon fiber, acrylic fiber, and polyolefin fiber. The number of these may be 1 alone, and 2 or more may be used in combination.

The average fiber length of the fibers is not particularly limited as long as the fibers can exhibit heat-insulating properties, and is preferably, for example, 0.05mm to 50mm.

The average fiber diameter of the fibers is not particularly limited as long as the fibers can exhibit heat-insulating properties, and is preferably, for example, 0.1 μm to 50 μm.

The content of the fibers in the fibrous body constituting the heat insulating layer 20 is not particularly limited as long as the heat insulating property can be exhibited, and is preferably 70 to 99.5 mass%, for example. In addition, in the case where the fibers include inorganic fibers and organic fibers, the content of the fibers in the fiber body is set to be the sum of the contents of the inorganic fibers and the organic fibers.

The fiber body may contain inorganic particles capable of suppressing heat radiation. The inorganic particles may be any inorganic particles that can reduce heat transfer by radiation, and for example, inorganic particles having an absorption peak in the infrared region can be used. The absorption peak in the infrared region can be measured by an infrared spectroluminance meter. The inorganic particles may act as a binder to which the fibers are bonded to each other. When the fibrous body contains inorganic particles, the fibrous body may be composed of a compression-molded body containing a mixture of fibers and inorganic particles.

Specific examples of the material of the inorganic particles include silica, titanium oxide, silicon carbide, ilmenite (ilmenite, feTiO), zirconium silicate, iron (III) oxide iron (II) (wustite (FeO), magnetite (Fe ₃O₄), hematite (Fe ₂O₃)), chromium dioxide, zirconium oxide, manganese dioxide, zirconia sol, titania sol, silica sol, alumina sol, bentonite, and kaolin.

Examples of the silica include silica produced by a dry process and silica produced by a wet process. Examples of the silica produced by the dry process include fumed silica. Examples of silica particles produced by the wet process include colloidal silica, precipitated silica, and silica gel. Examples of the colloidal silica include anionic colloidal silica and cationic colloidal silica. The precipitated silica is a silica having a mesoporous structure of powder around ten μm obtained by synthesizing solid silica from a weakly alkaline to neutral aqueous solution, filtering, washing with water, and drying. Further, there are cases where treatments such as pulverization, granulation, firing, classification, and the like are applied. Silica aerogel or silica xerogel having extremely low density is preferably used as the silica gel. Silica aerogel is silica gel having a porous structure of tens of nm, and the ratio of voids to volume is generally as high as 90% or more. The silica aerogel has low heat transfer due to the conduction of the solid portion, and thus, the movement of molecules of the air component inside is hindered, and therefore, the conduction and convection due to the gas are low, and the silica aerogel has low heat conductivity.

The fibrous body may contain 1 kind of inorganic particles, and may contain a plurality of kinds of inorganic particles.

The fibrous body can be formed, for example, from a compression-molded body containing a mixture of fibers and inorganic particles. When inorganic fibers are used as the fibers and silica is used as the inorganic particles, a compressed molded body formed of a mixture containing inorganic fibers and fumed silica can be used as the fibers. When silica fibers or glass fibers are used as the inorganic fibers, a compressed molded body formed of a mixture containing silica fibers or glass fibers and fumed silica can be used as the fiber body.

The fibrous body may comprise a binder. Examples of the binder include thermoplastic resins, thermosetting resins, and saccharides. The number of these may be 1 alone, and 2 or more may be used in combination. The content of the binder in the fiber body is not particularly limited as long as it is within a range capable of exhibiting heat-insulating properties, and may be set to an arbitrary content as appropriate.

The fibrous body may be formed, for example, from a compression-molded body containing a mixture of fibers, inorganic particles, and a binder.

Examples of the foam include urethane foam, phenol foam, polyethylene foam, polystyrene foam, and silicone foam.

The foam may contain inorganic particles, similar to the fibrous body. The inorganic particles may include inorganic particles similar to those included in the fibrous body. Therefore, details of the inorganic particles are omitted. The content of the inorganic particles contained in the fiber body can be appropriately set.

The density of the heat insulating layer 20 is not particularly limited, and may be, for example, 0.20g/cm ³～0.45g/cm³.

The porosity of the foam obtained by the archimedes method is not particularly limited, and can be appropriately set, and is preferably, for example, 30% to 90% in terms of securing heat insulation of the heat insulation layer 20.

In the case where the battery insulating material 1 is fixed in the casing while being sandwiched between the battery cells, the shape of the insulating layer 20 is not particularly limited as long as it is a shape suitable for insulating the surfaces of the battery cells, as in the case of the compression adjustment layer 10. In this case, the shape of the heat insulation layer 20 in a plan view may be rectangular (for example, polygonal such as quadrangle), circular, elliptical, or other shape.

As shown in fig. 1 and 2, the coating layer 30 is sealed in a state where the compression adjustment layer 10 and the heat insulation layer 20 are housed inside, with the surfaces exposed to the outside of the compression adjustment layer 10 and the heat insulation layer 20 being coated. By coating the compression adjustment layer 10 and the heat insulating layer 20 with the coating layer 30, even if the heat insulating layer 20 contains inorganic particles such as silica, the inorganic particles can be prevented from falling off from the cross section of the heat insulating layer 20. In addition, the coating layer 30 may be coated with only the heat insulating layer 20.

As shown in fig. 2, the coating layer 30 can be formed by welding or following the peripheral edges of a pair of sheet-shaped resin films 31A and 31B. Further, the coating layer 30 may be formed by folding back one sheet of the resin film 31A or the resin film 31B to weld or follow the peripheral edge.

The resin films 31A and 31B may have a layer formed of a film of polyethylene terephthalate (PET) or Polyimide (PI), and further may have a layer formed of a heat-seal resin. The layer formed of the heat-seal resin may be provided at least at the peripheral edge portions of the resin films 31A and 31B.

Examples of the heat-sealing resin include Polyethylene (PE) and polypropylene (PP).

The resin films 31A and 31B preferably have only a layer formed of a film of PET, or a laminate of a layer formed of a film of PET and a layer formed of a heat-seal resin.

The thickness of the coating layer 30 is not particularly limited, and may be set to an appropriate arbitrary thickness.

The battery insulating material 1 preferably has a predetermined residual stress ratio and residual stress even when external stress is applied. In the present embodiment, when the initial time for which the battery thermal insulation material 1 satisfies the following formula (1) when the compression time for applying the stress of 100N is 0 to 19 hours is set as the 1 st standing time, the residual stress ratio calculated by the following formula (2) is preferably 90% or more, and the residual stress after the compression time is 20 hours is preferably 0.34MPa or more.

(Residual stress after n hours- (n+1) residual stress after hours)/1 hour.ltoreq.1.cndot.1

Residual stress ratio [% ] = (residual stress after 20 hours of compression time)/(residual stress at 1 st set time) ×100·· (2)

(Wherein, in the formula (1), n is an integer of 1 to 19.)

The residual stress ratio is more preferably 91% or more, and still more preferably 93% or more. The residual stress after the compression time of 20 hours is more preferably 0.35MPa or more, and still more preferably 0.40MPa or more.

The residual stress ratio was determined by cutting the battery thermal insulation material 1 into test pieces of a predetermined size using a precision universal tester, compressing the test pieces at a predetermined compression rate (for example, 0.5 mm/min), and stopping compression at a point when the load became 100N. While this state was maintained, the stress after the 1 st leaving time and 20 hours was measured, and the residual stress ratio was calculated from the above formula (2).

Fig. 4 shows an example of the relationship between the compression time and the residual stress. In fig. 4, when a predetermined stress (for example, 100N) is applied to the battery thermal insulation material 1, that is, when the compression time is 0 hours, the residual stress RS _MAX becomes maximum. As shown in fig. 4, the longer the compression time is, the lower the residual stress is, and the reduction ratio of the residual stress indicates the relaxation ratio of the compression stress. The residual stress ratio obtained from the residual stress RS1 at the 1 st set time T1 and the residual stress RS2 after the compression time of 20 hours is 90% or more, and the reduction ratio of the residual stress after 20 hours from the 1 st set time T1 is suppressed to be low. Therefore, when the battery insulating material 1 is fixed in the housing while being sandwiched between the battery cells to construct the nonaqueous electrolyte secondary battery, the battery insulating material 1 can stably exert pressure on the battery cells for a long period of time.

The battery thermal insulation material 1 may evaluate the residual stress ratio by a method other than the method of calculating the residual stress ratio from the above formula (2). As another evaluation method, for example, a method of evaluating whether or not the rate of change in the thickness of the battery thermal insulation material 1 is equal to or less than a predetermined value (for example, 3%) by placing a weight for a predetermined period (for example, 30 days) so as to apply a compressive load of 0.34MPa in an environment of 23±3 ℃ may be used.

Next, a method for manufacturing the battery thermal insulation material 1 will be described.

First, after the heat insulating layer 20 is laminated on one main surface of the compression adjustment layer 10, a resin film 31A is laminated on the main surface opposite to the heat insulating layer 20 side of the compression adjustment layer 10, and a resin film 31B is laminated on the main surface opposite to the compression adjustment layer 10 side of the heat insulating layer 20, thereby forming a laminate (lamination step).

The resin films 31A and 31B are molded so as to have a size such that edges of the resin films 31A and 31B are positioned outside edges of the compression adjustment layer 10 and the heat insulation layer 20 in a plan view of the compression adjustment layer 10 and the heat insulation layer 20.

Next, the edge of the resin film 31A of the laminate and the edge of the resin film 31B are thermally welded (welding step).

Thus, the battery heat insulating material 1 in which the compression adjustment layer 10 and the heat insulating layer 20 are sealed in a state of being sealed inside the coating layer 30 is obtained.

The heat insulating material 1 for a battery is provided with a compression adjustment layer 10 and a heat insulating layer 20, wherein the ratio of the thickness of the compression adjustment layer 10 to the thickness of the heat insulating layer 20 is more than 0.5 and less than 4.5, and the compressive stress when compressed and strained at any ratio in the range of 25-70% in the thickness direction with respect to the thickness of the compression adjustment layer 10 before compression is 0.34-3.45 MPa. This improves flexibility against external stress and maintains low thermal conductivity of the battery insulating material 1. Thus, when the battery insulating material 1 is fixed in the housing while being sandwiched between the battery cells to constitute the nonaqueous electrolyte secondary battery, the battery insulating material 1 can exhibit excellent cushioning properties against expansion of the battery cells, and can have high heat insulating properties.

In general, in a battery cell included in a nonaqueous electrolyte secondary battery, the internal pressure of the battery cell changes during charge and discharge, and the battery cell expands, contracts, and deforms in the thickness direction of the battery cell. That is, in the battery cell, in general, the internal pressure increases as compared with that in the discharge by the temperature increase, gas generation, crystallization change in the electrode, and the like during the charge. The battery cells expand and contract due to the change in the internal pressure of the battery cells. In particular, in a lithium ion secondary battery in which a large number of battery cells are stacked, it is difficult for the battery cells disposed inside to emit heat, and the degree of deformation of the expansion and contraction of the battery cells increases, so that it is difficult to suppress the deformation. In contrast, in the present embodiment, the battery thermal insulation material 1 has a compressive stress lower than that of the thermal insulation layer 20 while maintaining the predetermined thickness of the compression adjustment layer 10 with respect to the thermal insulation layer 20, and thus can be deformed flexibly against stress from the outside to exert a cushioning effect, and can improve thermal insulation.

The battery insulating material 1 may include a coating layer 30 that covers at least the insulating layer 20. Thus, the battery insulating material 1 can seal the insulating layer 20 at least in the coating layer 30. When the heat insulating layer 20 contains inorganic particles or the like, the inorganic particles or the like are liable to fall off from the cut surface of the heat insulating layer 20, and thus it is necessary to prevent this. In the battery insulating material 1, the insulating layer 20 is sealed at least in the coating layer 30, whereby the cut surface of the insulating layer 20 is surrounded by the coating layer 30, and even when the insulating layer 20 contains inorganic particles or the like, the drop-off of the inorganic particles or the like from the cut surface of the insulating layer 20 can be reduced easily. Further, the battery insulating material 1 can suppress the deterioration of the heat insulating layer 20 by suppressing the falling-off of inorganic particles or the like from the heat insulating layer 20, and thus can more reliably maintain the heat insulating property of the battery cell.

The battery insulating material 1 may contain at least one of fumed silica, colloidal silica, precipitated silica, and silica aerogel in the insulating layer 20. Fumed silica, colloidal silica and silica aerogel can be used as inorganic particles, have a property of suppressing heat radiation, and have higher flexibility than other inorganic particles. Therefore, in the battery insulating material 1, at least one of fumed silica, colloidal silica, precipitated silica, and silica aerogel is contained as inorganic particles in the insulating layer 20, so that the insulating layer 20 can reliably exhibit heat insulating properties, and heat generated by the battery cells can be more reliably insulated. Further, by improving the flexibility of the heat insulating layer 20, the battery heat insulating material 1 can further improve the cushioning properties.

The battery thermal insulation material 1 can set the initial time for which the formula (1) is satisfied when the compression time for applying the stress of 100N is 0 to 19 hours to the 1 st set time, and the residual stress ratio calculated by the formula (2) is 90% or more, so that the residual stress after the compression time of 20 hours can be 0.34MPa or more. In the conventional battery heat insulating material including the compression adjustment layer, if the nonaqueous electrolyte secondary battery includes the battery heat insulating material, there is a possibility that the cushioning performance is lowered due to degradation and the pressure is lowered when the nonaqueous electrolyte secondary battery is used for a long period of time. For example, when the displacement of the heat insulating material for a battery in the thickness direction is 0.94mm and the compressive stress of the heat insulating material for a battery is 1MPa, the heat insulating material for a battery is compressed in the thickness direction at a predetermined ratio (for example, 1.8x ^-7 mm/min). In this case, the compression adjustment layer is compressed and relaxed, and the compression stress of the compression adjustment layer tends to be reduced. Therefore, in order to stably apply a predetermined pressure to the battery cells included in the nonaqueous electrolyte secondary battery for a long period of time, it is desirable that the compression adjustment layer included in the battery insulating material has a higher compressive stress even after the nonaqueous electrolyte secondary battery is used for a long period of time. In the present embodiment, the battery thermal insulation material 1 can set the residual stress ratio calculated by the above formula (2) to 90% or more, and the residual stress after the compression time of 20 hours to 0.34MPa or more. Therefore, by providing the battery thermal insulating material 1 in the nonaqueous electrolyte secondary battery and using the nonaqueous electrolyte secondary battery for a long period of time, even if the residual stress of the compression adjustment layer 10 of the battery thermal insulating material 1 is reduced, the relaxation of the residual stress can be suppressed, and therefore, sufficient cushioning properties can be exhibited while applying pressure to the battery cells. Thus, the battery insulating material 1 can stably exhibit excellent cushioning properties for a long period of time against expansion of the battery cells while fixing the battery cells.

The residual stress after the 1 st standing time or 20 hours of the compression time can be measured, for example, by preparing a test body obtained by cutting the compression adjustment layer 10 into a predetermined size and using a precision universal tester. The prepared test body was compressed at a predetermined compression rate (for example, 0.5 mm/min) using a precision universal tester, and compression was stopped at the point when the load became 100N. By maintaining this state, the residual stress at the time of the 1 st set time or 20 hours was measured, and the residual stress after the 1 st set time or 20 hours was obtained.

In addition, even in the case of the battery thermal insulation material 1 having a single-layer structure formed only of the thermal insulation layer 20 and the case of a multi-layer structure including the compression adjustment layer 10 and the thermal insulation layer 20, when the initial time for satisfying the above formula (1) when the compression time for applying the stress of 100N is 0 to 19 hours is set to 1 st set time, the residual stress ratio calculated by the above formula (2) is 90% or more, and the residual stress after the compression time is 20 hours is 0.34MPa or more. Thus, when applied to a nonaqueous electrolyte secondary battery, the battery heat insulating material 1 suppresses the decrease in residual stress of the compression adjustment layer 10 and suppresses the relaxation of residual stress even when the nonaqueous electrolyte secondary battery is used for a long period of time, and can stably exert excellent cushioning properties for a long period of time while applying pressure to the battery cells. That is, in the conventional heat insulating material for a battery including the compression adjustment layer, if the nonaqueous electrolyte secondary battery includes the heat insulating material for a battery as described above, there is a possibility that the cushioning performance is lowered due to degradation and the pressure is lowered when the nonaqueous electrolyte secondary battery is used for a long period of time. For example, when the displacement of the heat insulating material for a battery in the thickness direction is 0.94mm and the compressive stress of the heat insulating material for a battery is 1MPa, the heat insulating material for a battery is compressed in the thickness direction at a predetermined ratio (for example, 1.8x ^-7 mm/min). In this case, the compression adjustment layer is compressed and relaxed, and the compression stress of the compression adjustment layer tends to be reduced. Therefore, in order to stably apply a predetermined pressure to the battery cells included in the nonaqueous electrolyte secondary battery for a long period of time, it is important that the compression adjustment layer included in the battery insulating material has a higher compressive stress even after the nonaqueous electrolyte secondary battery is used for a long period of time. In the present embodiment, the residual stress ratio calculated by the above formula (2) of the battery insulating material 1 is 90% or more, and the residual stress after the compression time of 20 hours is 0.34MPa or more. Thus, even if the nonaqueous electrolyte secondary battery includes the battery thermal insulation material 1, the reduction ratio of the residual stress of the compression adjustment layer 10 of the battery thermal insulation material 1 can be suppressed and the relaxation of the residual stress can be suppressed even if the nonaqueous electrolyte secondary battery is used for a long period of time, whereby the state of applying pressure to the battery cells can be maintained and sufficient cushioning properties can be provided. Thus, the battery insulating material 1 can exert pressure on the battery cells and stably exert excellent cushioning properties against expansion of the battery cells for a long period of time.

As described above, the battery insulating material 1 has excellent cushioning properties and high heat insulating properties, and thus can be effectively used as a heat insulating member for a lithium ion secondary battery, particularly a nonaqueous electrolyte secondary battery. By using the battery insulating material 1 as a heat insulating member of the nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery can maintain charge/discharge characteristics longer, and thus can have a longer lifetime.

In the present embodiment, the battery thermal insulating material 1 may be formed by laminating and sandwiching one of the compression adjustment layer 10 and the thermal insulating layer 20 with the other of the compression adjustment layer 10 and the thermal insulating layer 20 in the thickness direction (Z-axis direction) of the battery thermal insulating material 1. For example, as shown in fig. 5, the battery thermal insulation material 1 may be provided with a compression adjustment layer 10 on the upper surface of the thermal insulation layer 20. In this case, both the compression adjustment layer 10 and the heat insulation layer 20 may be covered with the cover layer 30.

As shown in fig. 6, the battery heat insulating material 1 may have heat insulating layers 20 on the upper surface 10a and the lower surface 10b of the compression adjustment layer 10, respectively, and may have a structure in which the compression adjustment layer 10 is sandwiched by the heat insulating layers 20. Even in this case, both the compression adjustment layer 10 and the heat insulation layer 20 may be covered with the cover layer 30.

In the present embodiment, the heat insulating material 1 for a battery may be configured by stacking a plurality of compression adjustment layers 10 and heat insulating layers 20 in the thickness direction (Z-axis direction) of the heat insulating material 1 for a battery, and alternately stacking the compression adjustment layers 10 and the heat insulating layers 20. For example, the heat insulating material 1 for a battery may be configured by forming the compression adjustment layer 10 and the heat insulating layer 20 as a group in 2 stages, and stacking 4 layers of the compression adjustment layer 10, the heat insulating layer 20, the compression adjustment layer 10, and the heat insulating layer 20 in the thickness direction (Z axis direction) of the heat insulating material 1 for a battery.

The heat insulating material 1 for a battery may be configured by stacking 5 layers of the compression adjustment layer 10, the heat insulating layer 20, and the compression adjustment layer 10 in the thickness direction (Z-axis direction) of the heat insulating material 1 for a battery, and may be configured by stacking 5 layers of the heat insulating layer 20, the compression adjustment layer 10, and the heat insulating layer 20.

In the present embodiment, as shown in fig. 7, the battery insulating material 1 may be formed by coating only the insulating layer 20 with the coating layer 30. In this case, an adhesive layer 40 is provided between the compression adjustment layer 10 and the coating layer 30. As the adhesive layer 40, a general adhesive, a double-sided tape, or the like used for a battery heat insulating material can be used. The battery insulating material 1 includes compression adjustment layers 10 on both sides above and below the insulating layer 20, and when only the insulating layer 20 is covered with the cover layer 30, an adhesive layer 40 is provided between each compression adjustment layer 10 and the cover layer 30.

< Nonaqueous electrolyte secondary battery >)

The case where the battery thermal insulation material 1 according to the present embodiment is applied to a nonaqueous electrolyte secondary battery will be described. Examples of the nonaqueous electrolyte secondary battery include lithium ion secondary batteries, nickel-hydrogen secondary batteries, nickel-cadmium secondary batteries, and polymer secondary batteries. In this embodiment, a case where the nonaqueous electrolyte secondary battery is a lithium ion secondary battery will be described.

Fig. 8 is a perspective view showing an example of a lithium ion secondary battery, and fig. 9 is a partial cross-sectional view of the lithium ion secondary battery. As shown in fig. 8, the lithium ion secondary battery 50 includes a plurality of (4 in fig. 8) battery cells 51, a plurality of heat insulating members (hereinafter, simply referred to as heat insulating members) 52, and a casing 53, and the plurality of battery cells 51 are arranged in the thickness direction of the battery cells 51 in the casing 53 via the heat insulating members 52.

The battery cell includes a positive electrode, a negative electrode, a nonaqueous electrolyte (for example, a nonaqueous electrolyte or a solid electrolyte), a battery case, and a separator as needed, and the positive electrode, the negative electrode, the nonaqueous electrolyte, and the separator as needed are housed in the battery case. The shape of the plurality of battery cells 51 is not particularly limited, and may each have a substantially rectangular parallelepiped shape as shown in fig. 8. The plurality of battery cells 51 are arranged so as to face each other with a space therebetween in the thickness direction. The plurality of battery cells 51 are arranged at intervals in the thickness direction thereof.

The number of the battery cells 51 is not particularly limited, and may be appropriately set according to the sizes of the battery cells 51 and the housing 53, and may be 1 to 3 or 5 or more.

As shown in fig. 9, the plurality of heat insulating members 52 are arranged so that the plurality of battery cells 51 are in contact with each other in the thickness direction of the battery cells 51 and the opposite surfaces 51a of the battery cells 51 are in contact with each other. The welded portion 52a of the heat insulating material 52 is disposed so as to contact the inner surface of the housing 53. The heat insulating material 52 suppresses heat conduction between the battery cells 51. The heat insulating material 52 is provided by stacking a compression adjustment layer 521 and a heat insulating layer 522 in this order, and may include a coating layer 523 that covers the compression adjustment layer 521 and the heat insulating layer 522. The coating layer 523 may be formed of a pair of resin films 523A and 523B. The compression adjustment layer 521, the heat insulating layer 522, and the coating layer 523 are similar to the compression adjustment layer 10, the heat insulating layer 20, and the coating layer 30 of the battery heat insulating material 1 described above, and therefore, the details thereof are omitted.

In the present embodiment, the compression adjustment layer 521 is disposed so as to face one battery cell 51 (the battery cell 51 on the right side in the thickness direction in fig. 9), and the heat blocking layer 522 is disposed so as to face the other battery cell 51 (the battery cell 51 on the left side in the thickness direction in fig. 9), but may be reversed. As shown in fig. 5, when the compression adjustment layers 521 are disposed on the main surfaces of both the heat insulating layers 522, the heat insulating material 52 is disposed so that the compression adjustment layers 521 face each other in the battery cells 51 of both the heat insulating layers.

The casing 53 accommodates a plurality of battery cells 51 and heat insulating materials 52. The shape of the housing 53 is not particularly limited as long as it can accommodate a plurality of battery cells 51 and the heat insulating material 52, and may have a substantially rectangular parallelepiped shape.

In the lithium ion secondary battery 50, by disposing the heat insulating material 52 between the battery cells 51, when one battery cell 51 is heated and swells as compared with the other battery cells 51, the compression adjustment layer of the heat insulating material 52 is compressed to absorb the swelling of the one battery cell 51, and the heat insulating layer of the heat insulating material 52 is hardly compressed, so that the heat insulating property can be maintained, and therefore, the influence on the other battery cells 51 can be reduced.

A battery cell 51 that becomes high temperature, swells; a deteriorated and expanded battery cell 51; the deteriorated heat insulating material 52 may be replaced with a new battery cell 51 or heat insulating material 52 as appropriate.

Since the lithium ion secondary battery 50 includes the heat insulating material 52 between the plurality of battery cells 51, the lithium ion secondary battery can exhibit excellent cushioning properties against expansion of the battery cells 51 and can have high heat insulating properties. Therefore, the lithium ion secondary battery 50 can be safely used while suppressing breakage of the battery cells 51. Therefore, the lithium ion secondary battery 50 using the battery thermal insulation material 1 has the characteristics described above, and thus can be suitably used for Electric Vehicles (EV), hybrid Vehicles (HV), electric vehicles of plug-in hybrid vehicles (PHV), portable electronic devices such as portable terminals, mobile phones, and notebook-type personal computers, wearable devices, and the like.

Examples

The embodiments are described in further detail below by way of examples, but the embodiments are not limited to these examples.

< Manufacturing of heat insulation Material >)

Example 1

(Production of heat insulating layer 1)

21 Parts by mass of hydrophilic fumed silica particles ("AEROSIL (registered trademark) 380", manufactured by Japanese AEROSIL Co., ltd., average primary particle diameter: about 7 μm, BET specific surface area: 380m ²/g) and 4 parts by mass of glass fibers ("CS 25K-871", manufactured by Nito Seisakusho Co., ltd., average diameter: 13 μm, average fiber length: 25 mm) as inorganic fibers were previously disintegrated by hand, and the fiber-opened products were placed in a plastic bag and mixed so as to be uniformly dispersed. Next, the obtained mixed powder was put into a bag having excellent air permeability made of paper, nonwoven fabric, cloth or fabric, and compression molding was performed by a press machine so that the density of the molded product of the powder in which the content was pressed became 0.25g/cm ³, to prepare a heat insulating material (heat insulating layer) as a molded product obtained by molding a mixture containing hydrophilic fumed silica and glass fibers. The thickness of the resulting heat insulating material (heat insulating layer) was 3.3mm, and the density was 0.25g/cm ³.

The compressive elastic modulus compressive stress of the heat insulating layer 1 was measured by the following method for measuring the compressive elastic modulus compressive stress of the compression adjustment layer, and as a result, the compressive stress in a 25% compression state was 0.23MPa.

(Manufacture of compression adjustment layer)

The polypropylene (PP) foam (PP 3-fold foam sheet (PAULOWNIA (registered trademark), manufactured by mitsubishi chemical Tohcello, thickness 5 mm) was cut into the same size as the produced heat insulation layer 1 to obtain a compression adjustment layer, and the compression stress of the compression adjustment layer was measured by the following method.

((Compressive stress))

The heat-insulating layer 1 was cut to a predetermined thickness of 10mm square, and the compression stress at 25% compression of the test piece was measured at a compression rate of 0.5mm/min using a precision universal tester (AGS-5 kNX, manufactured by Shimadzu corporation).

(Production of heat-insulating Material)

The compression adjustment layer and the heat insulation layer prepared as described above were laminated to obtain a heat insulation material as shown in fig. 2.

(Ratio of the thickness of the compression adjustment layer to the thickness of the heat insulation layer)

The thicknesses of the heat insulating layer 1 and the compression adjustment layer were measured by using a feeler gauge (digital thickness gauge JAN-257, manufactured by measuring heads Φ20, ozaki). The ratio of the thickness of the compression adjustment layer to the thickness of the heat insulation layer 1 (thickness of the compression adjustment layer/thickness of the heat insulation layer 1) was about 1.5 (=5 mm/3.3 mm).

The type, thickness and 25% compression stress of the compression adjustment layer are shown in table 1, the type, composition, type, thickness and number of layers of the heat insulation layer are shown in table 2, and the composition, total thickness and ratio of the thickness of the compression adjustment layer to the thickness of the heat insulation layer are shown in table 3.

Example 2

In example 1, as the compression adjustment layer, a compression adjustment layer was used in which a rigid polyurethane foam (FL 140HM, manufactured by Nitsche Co., ltd., 8-fold foaming, thickness 15 mm) was cut to a thickness of 7.2 mm. As the heat insulating layer, a heat insulating layer 2 in which the following blending amount of blending components and compression molding conditions are changed is used instead of the heat insulating layer 1.

(Production of heat insulating layer 2)

A mixed solvent comprising 21 parts by mass of hydrophilic fumed silica particles ("AEROSIL (registered trademark) 380", manufactured by Aerosil corporation, japan, average primary particle diameter: about 7 μm, BET specific surface area: 380m ²/g), 4 parts by mass of glass fibers ("CS 25K-871", manufactured by Nito, inc., average diameter: 13 μm, average fiber length: 25 mm), 83 parts by mass of acetic acid, and 17 parts by mass of water was mixed so that the consistency became 50 to 90. The obtained mixed solution was evaluated by a method of consistency measurement described later. Next, the obtained mixed solution was applied to a substrate so that the thickness became 3.8mm to form a coating film. Further, the coated film was compression molded by a hot press so that the thickness thereof was 2mm and the density thereof was 0.3 to 0.5g/cm ³, and then dried at 100℃for 10 minutes to prepare a heat insulating material (heat insulating layer) as a molded article obtained by molding a mixture containing hydrophilic fumed silica and glass fibers. The thickness of the resulting heat insulating material (heat insulating layer) was 1.8mm, and the density was 0.31g/cm ³. The compressive stress of the heat insulating layer 2 was measured by using the above-described method for measuring compressive stress of the compression adjustment layer, and as a result, the compressive stress in a 25% compression state was 2.04MPa.

(Consistency measurement)

The mixed solutions of the heat-insulating layers obtained in examples 1 and 2 were prepared according to japanese industrial standard JIS K2220: 2013 "grease-part 7: consistency test method "the consistency is measured as" no mix consistency ". Specifically, a scale of such a size that the weight does not come into contact when the weight of the cone is lowered is prepared, and the scale is filled with a mixed solution and placed in daily chemical nikka-engineering PENETRO METER on which the weight is mounted. Next, the position of the weight is adjusted, the position where the weight contacts the mixed liquid is set, and the position is set as 0 point. Then, the weight was lowered at room temperature (25 ℃) for 5 seconds (+ -0.1 seconds), and the depth (mm) of the weight penetrating into the mixed solution was calculated as the consistency. The weight of the cone was a standard cone defined by japanese industrial standards, and the total weight of the product was 102.5g, and the weight of the holder using the weight was 47.5±0.05 g.

EXAMPLE 3

In example 1, glass wool (uncured wool (600 g/m ², manufactured by Asahi Fiber Glass) was heated for 10 minutes using a hot press at 180 ℃ as a compression adjustment layer, and the resin in the glass wool was thermally cured, and a sheet compression molded to a thickness of 3mm was cut into a thickness of 2 mm. A heat insulating layer 1 having a thickness of 2mm was produced in the same manner as in example 1. Except for this, a battery heat insulating material was produced in the same manner as in example 1.

EXAMPLE 4

A heat insulating material for a battery was produced in the same manner as in example 3 except that the thickness of the heat insulating layer 1 was changed to 1mm, and the heat insulating layer 1 was laminated on both the upper and lower surfaces of the compression adjustment layer in example 3 to produce a 3-layer heat insulating material laminate as shown in fig. 6.

EXAMPLE 5

A battery thermal insulation material was produced in the same manner as in example 3, except that a polypropylene (PP) integrally extruded hollow structure plate (single cone (registered trademark), TSC-5-1204BK, manufactured by the company Exsymo, thickness 5.2 mm) was used as the compression adjustment layer in example 1.

EXAMPLE 6

In example 1, a modified PPE foam (10-fold foam, 7mm in thickness) of modified polyphenylene ether (PPE) foam beads (Sunforce (registered trademark), manufactured by Asahi chemical Co., ltd.) was cut into a thickness of 5mm as a compression adjustment layer. The heat insulating layer 2 produced by the method shown in example 2 was set to a thickness of 2mm as the heat insulating layer. Except for this, a battery heat insulating material was produced in the same manner as in example 1.

EXAMPLE 7

In example 3, a heat insulating material for a battery was produced in the same manner as in example 3 except that a modified PPE foam (7-fold foam, thickness 7 mm) of modified polyphenylene ether (PPE) foam beads (Sunforce (registered trademark), manufactured by the rising chemical company) was cut into a thickness of 2mm as the compression adjustment layer.

EXAMPLE 8

In example 1, a polyester film having a thickness of 12 μm and a polyethylene film having a thickness of 1mm were laminated 2 sheets so that the polyethylene side was positioned inside to cover the heat insulating material for a battery produced in example 1, and both ends of the film were sealed by a heat sealer. Except for this, a battery heat insulating material was produced in the same manner as in example 1.

Example 9

In example 1, glass wool (uncured wool (700 g/m ², manufactured by Asahi Fiber Glass) was heated for 10 minutes using a hot press at 180 ℃ as the compression adjustment layer, and the resin in the glass wool was thermally cured, and a sheet compression-molded to a thickness of 3.6mm was used. A heat insulating layer 1 having a thickness of 2.4mm was produced in the same manner as in example 1. Except for this, a battery heat insulating material was produced in the same manner as in example 1.

EXAMPLE 10

In example 9, a battery heat insulating material was produced in the same manner as in example 9 except that the thickness of the heat insulating layer 1 was changed to 1.2mm, and the heat insulating layer 1 was laminated on both the upper and lower surfaces of the compression adjustment layer to produce a 3-layer heat insulating material laminate as shown in fig. 6.

EXAMPLE 11

A battery insulating material was produced in the same manner as in example 9, except that the insulating layer 2 having a thickness of 2.4mm was used as the insulating layer in example 9.

EXAMPLE 12

A heat insulating material for a battery was produced in the same manner as in example 11 except that the thickness of the heat insulating layer 2 was changed to 1.2mm, and the heat insulating layer 2 was laminated on both the upper and lower surfaces of the compression adjustment layer in example 11 to produce a 3-layer heat insulating material laminate as shown in fig. 6.

Example 13

In example 11, a battery insulating material was produced in the same manner as in example 11, except that 2 sheets of glass wool (uncured wool (600 g/m ², manufactured by Asahi Fiber Glass) were stacked as a compression adjustment layer, and the resin in the glass wool was thermally cured by heating for 10 minutes using a hot press at 180 ℃.

EXAMPLE 14

A heat insulating material for a battery was produced in the same manner as in example 13 except that the thickness of the heat insulating layer 2 was changed to 1.2mm, and the heat insulating layer 2 was laminated on both the upper and lower surfaces of the compression adjustment layer in example 13 to produce a 3-layer heat insulating material laminate as shown in fig. 6.

EXAMPLE 15

A battery insulating material was produced in the same manner as in example 1, except that the compression adjustment layer was not provided in example 1, and only the insulating layer 1 having a thickness of 2mm produced in example 1 was used.

EXAMPLE 16

A battery insulating material was produced in the same manner as in example 2 except that the compression adjustment layer was not provided in example 2, and the thickness of the insulating layer 2 produced in example 2 was set to 2.0mm, thereby forming an insulating layer.

EXAMPLE 17

A battery heat insulating material was produced in the same manner as in example 3, except that an ethylene-propylene-diene rubber (EPDM) foam sealing material (ept_ Sealer (registered trademark) EE-1000, thickness 5mm, manufactured by the eastern electric company) was used as the compression adjustment layer in example 3.

EXAMPLE 18

In example 3, as the compression adjustment layer, a sheet compression molded to a thickness of 3mm was cut to 2.5mm and 2 sheets of the product having a thickness of 2mm were stacked, and cut to a thickness of 4.5 mm. As the heat insulating layer, the heat insulating layer 2 was cut to a thickness of 1.0mm in the same manner as in example 3. Except for this, a battery heat insulating material was produced in the same manner as in example 3.

EXAMPLE 19

A heat insulating material for a battery was produced in the same manner as in example 18 except that the thickness of the heat insulating layer 2 was changed to 0.5mm, and the heat insulating layer 2 was laminated on both the upper and lower surfaces of the compression adjustment layer in example 18 to produce a 3-layer heat insulating material laminate as shown in fig. 6.

EXAMPLE 20

In example 6, as the compression adjustment layer, the 3mm thick compression molded sheet produced in example 3 was cut to a thickness of 1 mm. As the heat insulating layer, a heat insulating layer 2 having a thickness of 2mm produced by the method shown in example 6 was used. Except for this, a battery heat insulating material was produced in the same manner as in example 6.

Example 21

A heat insulating material for a battery was produced in the same manner as in example 20 except that the thickness of the heat insulating layer 2 was changed to 1.0mm, and the heat insulating layer 2 was laminated on both the upper and lower surfaces of the compression adjustment layer in example 20 to produce a 3-layer heat insulating material laminate as shown in fig. 6.

EXAMPLE 22

In example 6, a heat insulating material for a battery was produced in the same manner as in example 6, except that a modified PPE foam (5-fold foam, thickness 7 mm) of modified PPE foam beads (Sunforce (registered trademark), manufactured by the Asahi chemical Co., ltd.) was cut into a thickness of 2.0mm as the compression adjustment layer.

EXAMPLE 23

A battery heat insulating material was produced in the same manner as in example 3, except that an inorganic foam (Talbocell, thickness 15mm, manufactured by the product of baobao polymer company) was compression molded at 23 ℃ to a sheet having a thickness of 3.0mm as the compression adjustment layer in example 3.

EXAMPLE 24

A battery heat insulating material was produced in the same manner as in example 6, except that a PP embossed sheet (core cone (registered trademark) having a thickness of 4.5mm and manufactured by the company of the company Exsymo) was used as the compression adjustment layer in example 6.

EXAMPLE 25

In example 6, a battery heat insulating material was produced in the same manner as in example 6, except that a flame retardant polyethylene terephthalate (PET) foam ((BALTEX (registered trademark) T90.150, manufactured by AIREX corporation), 7-fold foamed, and a thickness of 5 mm) was used as the compression adjustment layer.

EXAMPLE 26

A battery heat insulating material was produced in the same manner as in example 6, except that a flame retardant polyethylene terephthalate (PET) foam ((BALTEX (registered trademark) T90.100, manufactured by AIREX corporation), 9-fold foamed, and 5mm thick) was used as the compression adjustment layer in example 6.

EXAMPLE 27

In example 6, a battery heat insulating material was produced in the same manner as in example 6, except that a polyethylene terephthalate (PET) foam ((BALTEX (registered trademark) T92.60, manufactured by AIREX corporation), 15-fold foam, and a thickness of 5 mm) was used as the compression adjustment layer.

EXAMPLE 28

In example 13, a battery insulating material was produced in the same manner as in example 13 except that a heat press at 180℃was used as the compression adjustment layer, glass wool (uncured wool (1556 g/m ², manufactured by CENTRAL GLASS fiber Co.) was heated for 10 minutes, and the resin in the glass wool was thermally cured, and a sheet compression-molded to a thickness of 3.6mm was used.

Example 29

In example 6, a heat insulating material for a battery was produced in the same manner as in example 6, except that a urethane foam ((Nippalay (registered trademark), manufactured by japan spring company) EH48 (density 0.48g/cm ³, thickness 4.3 mm) was used as the compression adjustment layer.

EXAMPLE 30

In example 6, a battery thermal insulation material was produced in the same manner as in example 6, except that a neoprene foam (registered trademark), C-4600 (density 0.3g/cm ³, thickness 3.3mm, manufactured by INOAC CORPORATION Co.) was used as the compression adjustment layer.

EXAMPLE 31

In example 6, a heat insulating material for a battery was produced in the same manner as in example 6, except that KS-120 (density 0.26g/cm ³, thickness 3.8 mm) of styrene-butadiene rubber foam (manufactured by Green gum, keihan Industrial Co.) was used as the compression-adjusting layer.

((Residual stress))

A test piece was cut into a compression-adjusting layer having a predetermined thickness of 10mm square, and the test piece was compressed at a compression rate of 0.5mm/min by using a precision universal tester (AGS-5 kNX, manufactured by Shimadzu corporation), and was left to stand for 20 hours after being compressed at 25%. The stress after 20 hours was measured, and the residual stress after 20 hours was measured by the following formula (V).

((Method of estimating residual stress))

Illustratively, the residual stress after 87600 hours was estimated using the battery insulating material produced in example 28. In the above steps, a graph of stress relaxation rate (%) and elapsed time was prepared. Fig. 10 shows the relationship between the stress relaxation rate (%) of the battery thermal insulation material of example 28 and the elapsed time. As shown in fig. 10, when logarithmic approximation is selected by the option of approximating a curve, the following expression (V) is obtained by displaying the expression in the figure.

y＝-1.731ln(x)+85.673···(V)

The stress relaxation rate (%) after 87600 hours was 87600 substituted in x, thereby obtaining 66%. The compressive stress in the initial 25% state of the compression-adjusted layer of example 28 was 2.50MPa, whereby the residual stress estimated value after 87600 hours was 1.65MPa by multiplying 2.50MPa by 66%.

< Evaluation >

The thermal conductivity, cushioning property, residual stress ratio and residual stress after 20 hours of each example of the heat insulating material were measured. The measurement results are shown in table 4.

(Thermal conductivity)

Thermal conductivity was measured according to JIS A1412-1: method for measuring thermal resistance and thermal conductivity of 2016 thermal insulation material-part 2: thermal conductivity at 80℃and 2MPa was measured by a thermal flow meter method (HFM method). The battery insulating material was cut into a size of 20mm×20mm to prepare a sample. Samples and reference samples (calcium silicate plate ("Hirac", manufactured by A & A MATERIAL Co., ltd., thickness: 5mm, 0.22W/(m.K)), aluminum plate ("A1060P", thickness: 0.2 mm) were prepared.

Next, on the lower plate surface of the air press (manufactured by welling manufacturing company), the respective members were adhered by holding thermocouple 1 (sheath thermocouple K type (SCHS 1-0), phi=0.15, manufactured by the company JIS1, CHINO), aluminum plate, insulating material for battery, aluminum plate, thermocouple 2 (sheath thermocouple K type (SCHS 1-0), phi=0.15, manufactured by the company JIS1, CHINO), reference sample, thermocouple 3 (sheath thermocouple K type (SCHS 1-0), phi=0.15, manufactured by the company JIS1, CHINO) in this order from the top. The upper plate was heated to 80℃and the lower plate was pressurized after being adjusted so that the load of the press heated to 35℃became 800N (equivalent to 2 MPa). The measurement is continued in a state of being heated and pressurized until the detected temperature of the thermocouple becomes stable. The temperature being stable means that the temperature change after 10 minutes is within.+ -. 0.1 ℃. The thermal conductivity k1 of the battery insulating material was determined from the temperature-stabilized detection temperature of each thermocouple and the thickness of the battery insulating material at the time of compression, as shown in the following formula (I). A thermal conductivity in the range of 0.010W/(mK) or more and 0.080W/(mK) or less was evaluated as favorable.

k1＝k2×(L1×ΔT1)/(L2×ΔT2)···(I)

(Buffering Property)

The deformation distances at compression stresses of 0.34MPa and 3.45MPa when the test bodies were compressed at a compression rate of 0.5mm/min were measured using a precision universal tester (AGS-5 kNX, manufactured by Shimadzu corporation). Further, a displacement amount (displacement range of 0.34MPa to 3.45 MPa) in which the compressive stress is in the range of 0.34MPa to 3.45MPa was calculated from the following formula (II). The displacement was evaluated as a buffer property in a displacement range of 0.34MPa to 3.45 MPa. A displacement range of 0.34MPa to 3.45MPa is evaluated as good when it exceeds 30%, and evaluated as bad when it is 30% or less.

Displacement range [% ] = (deformation distance at 3.45 MPa/test body thickness) ×100% - (deformation distance at 0.34 MPa/test body thickness) ×100% (II)

(Residual stress Rate)

A test piece was prepared by cutting a battery insulating material to a predetermined thickness of 10mm square. The test piece was compressed using a precision universal tester (AGS-5 kNX, manufactured by Shimadzu corporation) at a compression rate of 0.5mm/min, and the compression was stopped when the load became 100N. Then, the initial time for which the stress of 100N was applied and the compression time was 0to 19 hours was set as the 1st set time, and the stress after the 1st set time and 20 hours was measured, and the residual stress ratio was calculated by the following formula (2).

When the residual stress ratio was 90% or more, the evaluation was good, and when it was less than 90%, the evaluation was poor.

(Residual stress after n hours- (residual stress after n+1 hours)/residual stress rate +.1 [% ] = (residual stress after 20 hours compression)/(residual stress after 1 st set time) ×100 ·.2-

(Residual stress after 20 hours)

A test piece was prepared by cutting a battery insulating material to a predetermined thickness of 10mm square. The test body was compressed using a precision universal tester (AGS-5 kNX, manufactured by Shimadzu corporation) at a compression rate of 0.5mm/min, and the compression was stopped at a point when the load became 100N. The residual stress after 20 hours was measured while the test was directly kept. The residual stress after 20 hours was 0.34MPa or more, and the residual stress was evaluated as good, and the residual stress was evaluated as poor when the residual stress was less than 0.34 MPa.

TABLE 1

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TABLE 2

TABLE 3

TABLE 4

Table 4 shows that the thermal conductivity was 0.080W/(mK) or less, the displacement range of 0.34MPa to 3.45MPa was 31% or more, the residual stress ratio was 90% or more, and the residual stress after 20 hours was 0.36MPa or more in examples 1 to 14 and 25 to 29. On the other hand, in examples 15 to 24, 30 and 31, any one or more of the thermal conductivity, the displacement range of 0.34MPa to 3.45MPa, the residual stress ratio and the residual stress after 20 hours did not satisfy the criterion.

From this, it was confirmed that the battery insulating materials of examples 1 to 14 and 25 to 29 were different from the battery insulating materials of examples 15 to 24 in that the ratio of the thickness of the compression adjustment layer to the thickness of the insulating layer was 1.0 to 4.0, and the compressive stress when compressed and strained at any ratio in the range of 25% to 70% in the thickness direction was 0.50MPa to 3.36MPa with respect to the thickness of the compression adjustment layer before compression, and thus the battery insulating material was able to be deformed flexibly with respect to the expansion of the battery cell, and therefore excellent cushioning properties were able to be exhibited, and the battery insulating material was able to have high heat insulating properties. Therefore, it can be said that when the heat insulating materials for batteries of examples 1 to 14 and 25 to 29 are applied to lithium ion secondary batteries, the battery cells are prevented from being broken even if the battery cells are repeatedly expanded and contracted by charge and discharge, and heat generated by thermal expansion or the like of one battery cell can be prevented from being transferred to other adjacent battery cells, whereby safety can be improved. From this, it can be said that the lithium ion secondary batteries using the battery thermal insulation materials of examples 1 to 14 and 25 to 29 can be used safely for a longer period of time.

It can be said that the battery insulating material of each example has the same performance even when used or taken out after being assembled in a nonaqueous electrolyte secondary battery, if the ratio of the thickness of the compression adjustment layer to the thickness of the insulating layer, the compressive stress of the compression adjustment layer, the thermal conductivity, the cushioning property, the residual stress ratio, and the residual stress after 20 hours of the battery insulating material satisfy the respective predetermined values.

As described above, the embodiments are described as examples, and the present invention is not limited to the embodiments. The above-described embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, and the like can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention and are included in the invention described in the claims and their equivalents.

The embodiments of the present invention are, for example, as follows.

< 1 > A heat insulating material for a battery comprising a compression adjustment layer and a heat insulating layer laminated,

The heat insulating material for a battery according to < 2 > to < 1 > comprising a coating layer covering at least the heat insulating layer.

< 3 > The heat insulating material for a battery according to < 1 > or < 2 >, wherein the heat insulating layer contains at least one of fumed silica, colloidal silica, precipitated silica and silica aerogel.

The heat insulating material for a battery according to any one of < 1 > - < 3 >, wherein the thickness of the compression adjustment layer is 1.0mm to 8.8mm.

< 5 > When the initial time for satisfying the following formula (1) is set as the 1 st set time when the compression time for applying the stress of 100N is 0 to 19 hours according to any one of < 1 > - < 4 >,

The residual stress ratio calculated from the following formula (2) is 90% or more,

The residual stress after the compression time of 20 hours is 0.34MPa or more.

Residual stress ratio= (residual stress after 20 hours of compression time)/(residual stress at 1 st set time) ×100·· (2)

(Wherein, in the formula (1), n is an integer of 1 to 19.)

A nonaqueous electrolyte secondary battery comprising the heat insulating material for a battery according to any one of < 1 > - < 5 >.

A nonaqueous electrolyte secondary battery according to < 7 > and < 6 > comprising a plurality of battery cells arranged adjacently,

The battery cells are disposed between each other with the heat insulating material for batteries.

The present application claims that the entire contents of japanese patent application nos. 2021-160489 and 2022-27674 are incorporated into the present application based on the priorities of japanese patent application nos. 2021-160489 and 2022-2-25 applied to the japanese franchise at 30 of 2021.

Description of symbols

1. Heat insulation material for 52 battery

10. 521 Compression adjustment layer

20. 522 Heat insulating layer

30. 523 Coating layer

50. Lithium ion secondary battery

51. Battery cell

53. Basket body

Claims

1. A heat insulating material for a battery, comprising a compression adjustment layer and a heat insulating layer laminated,

2. The heat insulating material for a battery according to claim 1,

The heat insulation layer is provided with a coating layer which at least covers the heat insulation layer.

3. The heat insulating material for a battery according to claim 1,

The thermal insulation layer comprises at least one of fumed silica, colloidal silica, precipitated silica, and silica aerogel.

4. The heat insulating material for a battery according to claim 1,

The thickness of the compression adjustment layer is 1.0 mm-8.8 mm.

5. The heat insulating material for a battery according to claim 1,

When the initial time for which the stress of 100N is applied and the compression time is 0 to 19 hours and the following formula (1) is satisfied is set as the 1 st standing time,

The residual stress after the compression time is 20 hours is more than 0.34MPa,

(Residual stress after n hours- (residual stress after n+1 hours)/1.ltoreq.1.cndot.1 residual stress rate = (residual stress after 20 hours of compression time)/(residual stress at 1 st set time) ×100·· (2)

Wherein n in formula (1) is an integer of 1 to 19.

6. A non-aqueous electrolyte secondary battery having a high heat resistance,

The heat insulating material for a battery according to claim 1.

7. The nonaqueous electrolyte secondary battery according to claim 6,

Which comprises a plurality of adjacent battery units,

The battery cells are arranged with the heat insulating material for batteries therebetween.