Nonaqueous electrolyte secondary battery and secondary battery module

Abstract

The invention provides a nonaqueous electrolyte secondary battery and a secondary battery module. This secondary battery module is provided with: at least one non-aqueous electrolyte secondary battery; and an elastic body that is arranged together with the non-aqueous electrolyte secondary battery and that receives a load from the non-aqueous electrolyte secondary battery in the arrangement direction. The nonaqueous electrolyte secondary battery is provided with: an electrode body in which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are laminated; and a case for housing the electrode body, the elastic body having a compressive modulus of elasticity of 5-120 MPa, the positive electrode being provided with a positive electrode current collector containing Al and an element other than Al, and the thermal conductivity of the positive electrode current collector being 65-150 W / (m * K).

Description

[0001] This application is a divisional application of an application with an application date of January 18, 2021, an application number of 202180010923.3, and an invention title of "Non-aqueous electrolyte secondary battery and secondary battery module". Technical Field

[0002] The present disclosure relates to technologies of non-aqueous electrolyte secondary batteries and secondary battery modules. Background Art

[0003] Typically, a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery includes an electrode body and an electrolytic solution. The electrode body is formed by laminating a positive electrode having a positive electrode active material layer and a negative electrode having a negative electrode active material layer with a separator interposed therebetween. Such a non-aqueous electrolyte secondary battery is, for example, a battery that charges and discharges by charge carriers (such as lithium ions) in the electrolytic solution traveling back and forth between the two electrodes. When charging the non-aqueous electrolyte secondary battery, charge carriers are released from the positive electrode active material constituting the positive electrode active material layer and stored in the negative electrode active material constituting the negative electrode active material layer. When discharging, conversely, charge carriers are released from the negative electrode active material and stored in the positive electrode active material. Thus, when the charge carriers in the active material are stored and released accompanying the charge and discharge of the non-aqueous electrolyte secondary battery, the electrode body expands and contracts.

[0004] Incidentally, as a safety evaluation test for confirming the tolerance to internal short circuit of a battery, there is a nail penetration test. The nail penetration test is a test in which, for example, a nail is driven into the battery to simulate the generation of an internal short circuit, and the degree of heat generation is investigated to confirm the safety of the battery.

[0005] For example, Patent Document 1 discloses a non-aqueous electrolyte secondary battery having a positive electrode that reversibly stores lithium ions. The positive electrode includes an active material layer and a sheet-like current collector that supports the active material layer. The current collector contains aluminum and at least one element other than aluminum, and the average composition obtained by averaging the proportions of the elements constituting the current collector in the thickness direction of the current collector is equal to the composition of an alloy having a liquidus temperature of 630°C or lower. And according to Patent Document 1, the melting point of the positive electrode current collector is suppressed to be low, and the time until the positive electrode current collector melts during the nail penetration test is accelerated, so the heat generation of the battery in the nail penetration test is suppressed.

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2005 / 076392 Summary of the Invention

[0009] To ensure further safety of non-aqueous electrolyte secondary batteries, it is important to further suppress the heat generation amount of the battery in the nail penetration test.

[0010] A secondary battery module according to an aspect of the present disclosure includes: at least one non-aqueous electrolyte secondary battery; and an elastomer that is arranged together with the non-aqueous electrolyte secondary battery and bears a load from the non-aqueous electrolyte secondary battery in the arrangement direction. The non-aqueous electrolyte secondary battery includes: an electrode body formed by laminating a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and a case that houses the electrode body. The compressive elastic modulus of the elastomer is 5 MPa to 120 MPa. The positive electrode includes a positive electrode current collector containing Al and an element other than Al, and the thermal conductivity of the positive electrode current collector is 65 W / (m·K) to 150 W / (m·K).

[0011] In addition, a non-aqueous electrolyte secondary battery according to an aspect of the present disclosure includes: an electrode body formed by laminating a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; an elastomer that bears a load from the electrode body in the lamination direction of the electrode body; and a case that houses the electrode body and the elastomer. The compressive elastic modulus of the elastomer is 5 MPa to 120 MPa. The positive electrode includes a positive electrode current collector containing Al and an element other than Al, and the thermal conductivity of the positive electrode current collector is 65 W / (m·K) to 150 W / (m·K).

[0012] According to an aspect of the present disclosure, it is possible to suppress the heat generation amount of the battery in the nail penetration test. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a perspective view of the secondary battery module of the embodiment.

[0014] Figure 2 is an exploded perspective view of the secondary battery module of the embodiment.

[0015] Figure 3 is a cross-sectional view schematically showing a state where the non-aqueous electrolyte secondary battery expands.

[0016] Figure 4 is a schematic cross-sectional view showing the state of the electrode body during the nail penetration test.

[0017] Figure 5 is a schematic cross-sectional view showing a state where the elastomer is disposed in the case.

[0018] Figure 6 is a schematic perspective view of a cylindrical wound electrode body.

[0019] Figure 7It is a schematic perspective view showing an example of an elastomer.

[0020] Figure 8 It is a partial schematic cross-sectional view of the elastomer in a state of being sandwiched between an electrode body and a housing.

[0021] Explanation of reference numerals

[0022] 1. Secondary battery module; 2. Stacked body; 4. End plate; 6. Constraint member; 8. Cooling plate; 10. Non-aqueous electrolyte secondary battery; 12. Insulating spacer; 13. Housing; 14. Outer can; 16. Sealing plate; 18. Output terminal; 38. Electrode body; 38a. Positive electrode; 38b. Negative electrode; 38d. Separator; 39. Winding core; 40. Elastomer; 42. Rigid part; 42a. Base material; 44. Soft part; 44a. Through hole; 46. Concave part; 46a. Core part; 46b. Wire part; 50. Positive electrode current collector; 52. Positive electrode active material layer; 54. Negative electrode current collector; 56. Negative electrode active material layer; 58. Stud. Detailed implementation mode

[0023] Hereinafter, an example of the implementation mode will be described in detail. The drawings referred to in the description of the implementation mode are schematically drawn, and the dimensional ratios and the like of the constituent elements depicted in the drawings are sometimes different from the actual ones.

[0024] Figure 1 It is a perspective view of the secondary battery module of the implementation mode. Figure 2 It is an exploded perspective view of the secondary battery module of the implementation mode. As an example, the secondary battery module 1 includes a stacked body 2, a pair of constraint members 6, and a cooling plate 8. The stacked body 2 has a plurality of non-aqueous electrolyte secondary batteries 10, a plurality of insulating spacers 12, a plurality of elastomers 40, and a pair of end plates 4.

[0025] Each non-aqueous electrolyte secondary battery 10 is a rechargeable secondary battery such as a lithium-ion secondary battery. The non-aqueous electrolyte secondary battery 10 of the present implementation mode is a so-called square battery, and includes an electrode body 38 (refer to Figure 3 ), an electrolytic solution, and a flat rectangular parallelepiped-shaped housing 13. The housing 13 is composed of an outer can 14 and a sealing plate 16. The outer can 14 has a substantially rectangular opening on one side, and the electrode body 38, the electrolytic solution, etc. are accommodated in the outer can 14 through the opening. It should be noted that the outer can 14 is preferably coated with an insulating film such as a shrink tube. A sealing plate 16 for blocking the opening and sealing the outer can 14 is provided at the opening of the outer can 14. The sealing plate 16 constitutes the first surface 13a of the housing 13. The sealing plate 16 and the outer can 14 are joined by, for example, laser, friction stir welding, brazing, etc.

[0026] The housing 13 can be, for example, a cylindrical housing or an exterior body composed of a laminated sheet including a metal layer and a resin layer.

[0027] The electrode body 38 has a structure in which a plurality of sheet-like positive electrodes 38a and a plurality of sheet-like negative electrodes 38b are alternately laminated with a separator 38d therebetween (see Figure 3 ). The positive electrode 38a, the negative electrode 38b, and the separator 38d are laminated along the first direction X. That is, the first direction X becomes the lamination direction of the electrode body 38. Further, the electrodes located at both ends in this lamination direction face the long side surfaces of the housing 13 described later. It should be noted that the illustrated first direction X, second direction Y, and third direction Z are orthogonal to each other.

[0028] The electrode body 38 may also be a cylindrical wound type electrode body formed by winding a structure in which a strip-shaped positive electrode and a strip-shaped negative electrode are laminated with a separator therebetween, or a flat wound type electrode body obtained by forming the cylindrical wound type electrode body into a flat shape. It should be noted that in the case of the flat wound type electrode body, a rectangular parallelepiped-shaped exterior can is applicable, but in the case of the cylindrical wound type electrode body, a cylindrical exterior can is applicable.

[0029] On the sealing plate 16, that is, the first surface 13a of the housing 13, an output terminal 18 electrically connected to the positive electrode 38a of the electrode body 38 is provided at a position at one end in the long side direction, and an output terminal 18 electrically connected to the negative electrode 38b of the electrode body 38 is provided at a position at the other end. Hereinafter, the output terminal 18 connected to the positive electrode 38a is referred to as the positive terminal 18a, and the output terminal 18 connected to the negative electrode 38b is referred to as the negative terminal 18b. In addition, when it is not necessary to distinguish the polarities of the pair of output terminals 18, the positive terminal 18a and the negative terminal 18b are collectively referred to as the output terminal 18.

[0030] The exterior can 14 has a bottom surface opposite to the sealing plate 16. In addition, the exterior can 14 has four side surfaces connecting the opening and the bottom surface. Two of the four side surfaces are a pair of long side surfaces connecting the two long sides opposite to the opening. Each long side surface is the surface with the largest area among the surfaces of the exterior can 14, that is, the main surface. In addition, each long side surface is a side surface extending in a direction intersecting (for example, orthogonal to) the first direction X. The remaining two side surfaces other than the two long side surfaces are a pair of short side surfaces connecting the short sides of the opening and the bottom surface of the exterior can 14. The bottom surface, the long side surfaces, and the short side surfaces of the exterior can 14 respectively correspond to the bottom surface, the long side surfaces, and the short side surfaces of the housing 13.

[0031] In the description of the present embodiment, for convenience, the first surface 13a of the housing 13 is defined as the upper surface of the non-aqueous electrolyte secondary battery 10. In addition, the bottom surface of the housing 13 is defined as the bottom surface of the non-aqueous electrolyte secondary battery 10, the long side surface of the housing 13 is defined as the long side surface of the non-aqueous electrolyte secondary battery 10, and the short side surface of the housing 13 is defined as the short side surface of the non-aqueous electrolyte secondary battery 10. In addition, in the secondary battery module 1, the surface on the upper surface side of the non-aqueous electrolyte secondary battery 10 is defined as the upper surface of the secondary battery module 1, the surface on the bottom surface side of the non-aqueous electrolyte secondary battery 10 is defined as the bottom surface of the secondary battery module 1, and the surface on the short side surface side of the non-aqueous electrolyte secondary battery 10 is defined as the side surface of the secondary battery module 1. In addition, the upper surface side of the secondary battery module 1 is set to be above the vertical direction, and the bottom surface side of the secondary battery module 1 is set to be below the vertical direction.

[0032] A plurality of non-aqueous electrolyte secondary batteries 10 are arranged in parallel at a predetermined interval such that the long side surfaces of adjacent non-aqueous electrolyte secondary batteries 10 face each other. In addition, in the present embodiment, the output terminals 18 of each non-aqueous electrolyte secondary battery 10 are arranged so as to face the same direction, but they may also be arranged so as to face different directions.

[0033] Two adjacent non-aqueous electrolyte secondary batteries 10 are arranged (stacked) such that the positive terminal 18a of one non-aqueous electrolyte secondary battery 10 is adjacent to the negative terminal 18b of the other non-aqueous electrolyte secondary battery 10. The positive terminal 18a and the negative terminal 18b are connected in series via a bus bar. It should be noted that the output terminals 18 of the same polarity among a plurality of adjacent non-aqueous electrolyte secondary batteries 10 may also be connected in parallel to each other via a bus bar to form a non-aqueous electrolyte secondary battery block, and the non-aqueous electrolyte secondary battery blocks may be connected in series to each other.

[0034] The insulating spacer 12 is disposed between two adjacent non-aqueous electrolyte secondary batteries 10 to electrically insulate between the two non-aqueous electrolyte secondary batteries 10. The insulating spacer 12 is made of, for example, an insulating resin. Examples of the resin constituting the insulating spacer 12 include polypropylene, polybutylene terephthalate, and polycarbonate. A plurality of non-aqueous electrolyte secondary batteries 10 and a plurality of insulating spacers 12 are alternately stacked. In addition, the insulating spacer 12 is also disposed between the non-aqueous electrolyte secondary battery 10 and the end plate 4.

[0035] The insulating spacer 12 has a flat portion 20 and a wall portion 22. The flat portion 20 is interposed between the opposing long side surfaces of two adjacent non-aqueous electrolyte secondary batteries 10. Thereby, insulation between the outer cans 14 of adjacent non-aqueous electrolyte secondary batteries 10 is ensured.

[0036] The wall portion 22 extends from the outer edge portion of the flat portion 20 in the direction in which the non-aqueous electrolyte secondary battery 10 is arranged, covering a part of the upper surface, the side surface, and a part of the bottom surface of the non-aqueous electrolyte secondary battery 10. Thereby, for example, the side distance between adjacent non-aqueous electrolyte secondary batteries 10 or between the non-aqueous electrolyte secondary battery 10 and the end plate 4 can be ensured. The wall portion 22 has a notch 24 that exposes the bottom surface of the non-aqueous electrolyte secondary battery 10. In addition, the insulating spacer 12 has a biasing force receiving portion 26 that faces upward at both ends in the second direction Y.

[0037] The elastomer 40 is arranged along the first direction X together with a plurality of non-aqueous electrolyte secondary batteries 10. That is, as described above, the first direction X is both the stacking direction of the electrode body 38 and the arrangement direction of the non-aqueous electrolyte secondary battery 10 and the elastomer 40. The elastomer 40 is in a sheet shape and is interposed, for example, between the long side surfaces of the respective non-aqueous electrolyte secondary batteries 10 and the flat portions 20 of the respective insulating spacers 12. The elastomer 40 disposed between two adjacent non-aqueous electrolyte secondary batteries 10 may be a single sheet or a laminate formed by laminating a plurality of sheets. The elastomer 40 may also be fixed to the surface of the flat portion 20 by adhesion or the like. Alternatively, a recess may be provided in the flat portion 20, and the elastomer 40 may be inserted into the recess. Alternatively, the elastomer 40 and the insulating spacer 12 may be integrally formed. Alternatively, the elastomer 40 may also serve as the flat portion 20.

[0038] A plurality of non-aqueous electrolyte secondary batteries 10, a plurality of insulating spacers 12, and a plurality of elastomers 40 arranged side by side are clamped by a pair of end plates 4 in the first direction X. The end plate 4 is made of, for example, a metal plate or a resin plate. A threaded hole 4a is provided in the end plate 4, and the threaded hole 4a penetrates the end plate 4 in the first direction X for screw engagement with the screw 28.

[0039] A pair of restraining members 6 are longitudinally elongated members having the first direction X as the long side direction. The pair of restraining members 6 are arranged so as to face each other in the second direction Y. The laminate 2 is interposed between the pair of restraining members 6. Each restraining member 6 includes a main body portion 30, a support portion 32, a plurality of biasing portions 34, and a pair of fixing portions 36.

[0040] The main body portion 30 is a rectangular portion extending along the first direction X. The main body portion 30 extends parallel to the side surfaces of the respective non-aqueous electrolyte secondary batteries 10. The support portion 32 extends along the first direction X and projects downward from the lower end of the main body portion 30 in the second direction Y. The support portion 32 is a continuous plate-like body in the first direction X and supports the laminate 2.

[0041] A plurality of biasing portions 34 are connected to the upper end of the main body portion 30 and protrude in the second direction Y. The support portion 32 and the biasing portions 34 face each other in the third direction Z. The plurality of biasing portions 34 are arranged at a predetermined interval in the first direction X. Each biasing portion 34 is, for example, in the shape of a leaf spring and biases each non-aqueous electrolyte secondary battery 10 toward the support portion 32.

[0042] A pair of fixing portions 36 are plate-like bodies that protrude in the second direction Y from both end portions of the main body portion 30 in the first direction X. The pair of fixing portions 36 face each other in the first direction X. Through holes 36a through which the screws 28 pass are provided in each fixing portion 36. The restraining member 6 is fixed to the laminate 2 by the pair of fixing portions 36.

[0043] The cooling plate 8 is a mechanism for cooling the plurality of non-aqueous electrolyte secondary batteries 10. The laminate 2 is placed on the main surface of the cooling plate 8 in a state of being restrained by the pair of restraining members 6, and is fixed to the cooling plate 8 by passing fastening members such as screws through the through hole 32a of the support portion 32 and the through hole 8a of the cooling plate 8.

[0044] Figure 3 It is a cross-sectional view schematically showing the situation where the non-aqueous electrolyte secondary battery expands. It should be noted that in Figure 3 , the number of non-aqueous electrolyte secondary batteries 10 is schematically illustrated. In addition, the illustration of the internal structure of the non-aqueous electrolyte secondary battery 10 is simplified, and the illustration of the insulating spacer 12 is omitted. As Figure 3 shown, an electrode body 38 (a positive electrode 38a, a negative electrode 38b, and a separator 38d) is housed inside each non-aqueous electrolyte secondary battery 10. The non-aqueous electrolyte secondary battery 10 expands and contracts the outer can 14 by the expansion and contraction of the electrode body 38 accompanying charge and discharge. If the outer can 14 of each non-aqueous electrolyte secondary battery 10 expands, a load G1 toward the outside in the first direction X is generated in the laminate 2. That is, the elastic body 40 arranged together with the non-aqueous electrolyte secondary battery 10 bears the load from the non-aqueous electrolyte secondary battery 10 in the first direction X (which is the arrangement direction of the non-aqueous electrolyte secondary battery 10 and the elastic body 40 and is the lamination direction of the electrode body 38). On the other hand, a load G2 corresponding to the load G1 is applied to the laminate 2 by the restraining member 6.

[0045] Figure 4 It is a schematic cross-sectional view showing the state of the electrode body during the nail penetration test. As Figure 4 shown, the positive electrode 38a includes a positive electrode current collector 50 and a positive electrode active material layer 52 formed on the positive electrode current collector 50, and the negative electrode 38b includes a negative electrode current collector 54 and a negative electrode active material layer 56 formed on the negative electrode current collector 54. And, by driving a nail into the non-aqueous electrolyte secondary battery during the nail penetration test, as Figure 4As shown, the nail 58 passes through the positive electrode 38a and the separator 38d to reach the negative electrode 38b. When the positive current collector 50 and the negative current collector 54 are in direct contact with the nail 58, an internal short circuit occurs, a short-circuit current flows, and the non-aqueous electrolyte secondary battery generates heat.

[0046] Here, the positive current collector 50 of the present embodiment contains Al and an element other than Al, and is a low-thermal-conductivity Al-containing positive current collector with a thermal conductivity of 65 W / (m·K) to 150 W / (m·K). In such a low-thermal-conductivity Al-containing positive current collector, heat is likely to concentrate on the short-circuit portion (the portion of the positive current collector in direct contact with the nail), so the melting of the positive current collector 50 at the short-circuit portion is accelerated. That is, in the nail penetration test, the time from the occurrence of the internal short circuit to the melting of the positive current collector 50 is accelerated.

[0047] In addition, the elastomer 40 of the present embodiment is an elastomer having a compressive elastic modulus of 5 MPa to 120 MPa. And by using an elastomer having a compressive elastic modulus of 5 MPa to 120 MPa, the load G1 toward the outside in the first direction X and the load G2 corresponding to the load G1 are alleviated, so that the excessive approach between the positive electrode 38a and the negative electrode 38b is suppressed. Thus, compared with the case where the aforementioned low-thermal-conductivity Al-containing positive current collector is used but the elastomer having a compressive elastic modulus of 5 MPa to 120 MPa is not disposed or an elastomer having a compressive elastic modulus exceeding 120 MPa is disposed, the increase in the area of the short-circuit portion of the positive current collector 50 in the nail penetration test can be suppressed. Therefore, in the nail penetration test, the time from the occurrence of the internal short circuit to the melting of the positive current collector 50 is advanced more, and the heat generation amount of the battery in the nail penetration test is suppressed.

[0048] Figure 5 It is a schematic cross-sectional view showing the state where the elastomer is disposed inside the housing. The elastomer 40 is not limited to the case of being arranged together with the non-aqueous electrolyte secondary battery 10 as described above, that is, the case of being disposed outside the housing 13, and can also be disposed inside the housing 13. Figure 5 The shown elastomer 40 is disposed at both ends of the electrode body 38 in the stacking direction (the first direction X) of the electrode body 38. In addition, the elastomer 40 is sandwiched between the inner wall of the housing 13 and the electrode body 38.

[0049] When the electrode body 38 expands due to charge and discharge of the non-aqueous electrolyte secondary battery 10 or the like, a load is generated on the electrode body 38 toward the outside in the first direction X. That is, the elastic body 40 disposed within the housing 13 bears the load from the electrode body 38 in the first direction X (the stacking direction of the electrode body 38). And as long as the elastic body 40 has a compressive elastic modulus of 5 MPa to 120 MPa and the positive electrode current collector 50 is a low-thermal-conductivity aluminum-containing positive electrode current collector containing Al and an element other than Al and having a thermal conductivity of 65 W / (m·K) to 150 W / (m·K), the same operational effects as described above can be obtained.

[0050] The elastic body 40 within the housing 13 may be disposed at any position as long as it can bear the load from the electrode body 38 in the stacking direction of the electrode body 38. For example, if the electrode body 38 is Figure 6 the cylindrical wound type electrode body 38 as shown, the elastic body 40 may also be disposed at the winding core portion 39 of the cylindrical wound type electrode body 38. It should be noted that the stacking direction of the cylindrical wound type electrode body 38 is the radial direction (R) of the electrode body 38. And along with the expansion and contraction of the electrode body 38, a load is generated on the electrode body 38 in the stacking direction (the radial direction (R) of the electrode body 38) of the electrode body 38, and the elastic body 40 within the winding core portion 39 bears the load in the stacking direction of the electrode body 38. In addition, although the description in the figure is omitted, when a plurality of electrode bodies 38 are arranged within the housing 13, the elastic body 40 may also be disposed between adjacent electrode bodies 38. Also, in the case of a flat wound type, the elastic body may also be disposed at the center portion of the electrode body in the same manner.

[0051] Hereinafter, the positive electrode 38a, the negative electrode 38b, the separator 38d, the elastic body 40, and the electrolytic solution will be described in detail.

[0052] The positive electrode 38a has a positive electrode current collector 50 and a positive electrode active material layer 52 formed on the positive electrode current collector 50. The positive electrode current collector 50 only needs to contain Al and an element other than Al and have a thermal conductivity in the range of 65 W / (m·K) to 150 W / (m·K). It should be noted that Al and the element other than Al may or may not be alloyed.

[0053] For example, from the aspect of suppressing an increase in the resistance value of the positive electrode current collector 50 or the like, the content of Al in the positive electrode current collector 50 is preferably more than 50% by mass, more preferably 75% by mass or more, and still more preferably 90% by mass or more. The upper limit value of the content of Al in the positive electrode current collector 50 is, for example, 98% by mass or less.

[0054] Elements other than Al contained in the positive current collector 50 are not particularly limited as long as they can adjust the thermal conductivity to the above range, and examples thereof include Mg, Si, Sn, Cu, Zn, Ge, etc. Among them, Mg is preferred in terms of easily adjusting the thermal conductivity of the positive current collector 50. In terms of adjusting the thermal conductivity of the positive current collector 50 to 150 W / (m·K) or less, the content of Mg in the positive current collector 50 is preferably 1.5 mass% or more, and preferably 3 mass% or more. The greater the content of Mg in the positive current collector 50, the harder the positive current collector 50 becomes. Generally speaking, if the positive current collector hardens, for example, in a non-aqueous electrolyte secondary battery using a flat-wound electrode body, due to the expansion and contraction of the electrode body caused by charge and discharge, stress is applied to the corners of the flat-wound electrode body (the parts where the electrode and the separator are bent), and sometimes the positive current collector at the corners of the electrode body may break. However, in the present embodiment, the stress applied to the corners of the flat-wound electrode body is also alleviated by the elastic body 40 of 5 MPa to 120 MPa. Therefore, even if the content of Mg in the positive current collector 50 is increased, the breakage of the positive current collector 50 can be suppressed. The content of Mg in the positive current collector 50 is, for example, less than 50 mass%, and considering the resistance value of the positive current collector 50, it is preferably 10 mass% or less, and more preferably 6 mass% or less.

[0055] The thermal conductivity of the positive current collector 50 may be in the range of 65 W / (m·K) to 150 W / (m·K). However, from the aspect of further suppressing the heat release amount of the battery during the nail penetration test, it is preferably in the range of 85 W / (m·K) to 130 W / (m·K), and more preferably in the range of 95 W / (m·K) to 120 W / (m·K).

[0056] <Method for measuring thermal conductivity>

[0057] After measuring the thermal diffusivity, specific heat, and density of the positive current collector 50 by the following method, substitute them into the following formula (1) to obtain the thermal conductivity (W / m·K) of the positive current collector 50.

[0058] · Thermal diffusivity: Measured at 25°C using a xenon flash analyzer (registered trademark: LFA467HT HyperFlash, manufactured by Netzsch Japan Co., Ltd.).

[0059] · Specific heat: Measured by comparing with a sapphire reference material using a differential scanning calorimeter (DSC).

[0060] · Density: Measured using Archimedes' principle.

[0061] · Thermal conductivity = (Thermal diffusivity) × (Specific heat) × (Density) (1)

[0062] For example, from the aspect of suppressing breakage of the positive current collector 50 at the corners of the flat wound electrode body due to charge and discharge, the positive current collector 50 preferably has a Young's modulus of 45 kN / mm 2 to 73.5 kN / mm 2 . The Young's modulus is measured by a tensile test (for example, Technograph TG-2kN, a tensile and compression testing machine manufactured by Minebea Mitsumi) under a temperature condition of 25°C.

[0063] For example, from the aspects of rapidly melting during the nail penetration test and effectively suppressing the heat release amount of the battery, etc., the positive current collector 50 preferably has a liquidus temperature of 650°C or lower. The lower limit value of the liquidus temperature of the positive current collector 50 is, for example, 450°C or higher. It should be noted that the liquidus temperature refers to the temperature at which a solid phase starts to form from a liquid phase. The liquidus temperature is obtained by differential scanning calorimetry (DSC).

[0064] The positive electrode active material layer 52 contains a positive electrode active material. The positive electrode active material layer 52 preferably contains a conductive material and a binder material in addition to the positive electrode active material. The positive electrode active material layer 52 is preferably provided on both sides of the positive current collector 50.

[0065] As the positive electrode active material, a lithium transition metal composite oxide or the like is used, for example. As the metal elements contained in the lithium transition metal composite oxide, Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. can be cited. Among them, it is preferable to contain at least one of Ni, Co, and Mn. As an example of a suitable composite oxide, a lithium transition metal composite oxide containing Ni, Co, and Mn, and a lithium transition metal composite oxide containing Ni, Co, and Al can be cited.

[0066] Examples of the conductive material include carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. Examples of the binder material include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, polyolefin resin, etc. In addition, these resins can be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, poly(ethylene oxide) (PEO), etc.

[0067] The positive electrode 38a can be manufactured, for example, by coating a positive electrode composite material slurry containing a positive electrode active material, a conductive material, and a binder material, etc. on the positive current collector 50, drying the coating film, and then rolling it to form the positive electrode active material layer 52 on the positive current collector 50.

[0068] The negative electrode 38b has a negative electrode current collector 54 and a negative electrode active material layer 56 formed on the negative electrode current collector 54. The negative electrode current collector 54 uses a foil of a metal that is stable within the potential range of the negative electrode 38b, a film having the metal disposed on the surface layer, etc., and examples thereof include copper.

[0069] The negative electrode active material layer 56 contains a negative electrode active material. The negative electrode active material layer 56 preferably contains a binder material, etc. Examples of the binder material include the same binder materials as those contained in the positive electrode active material layer 52. The negative electrode active material layer 56 is preferably formed on both sides of the negative electrode current collector 54.

[0070] Examples of the negative electrode active material include substances that can reversibly store and release lithium ions, etc. Specifically, examples include carbon materials such as natural graphite, artificial graphite, hard carbon, soft carbon, etc., surface-modified carbon materials in which the surface of the above carbon materials is covered with an amorphous carbon film, metals alloyed with lithium such as silicon (Si), tin (Sn), etc., alloys containing metal elements such as Si, Sn, etc., oxides containing metal elements such as Si, Sn, etc. They can be used alone or in combination of two or more.

[0071] The negative electrode 38b can be produced, for example, by coating a negative electrode composite material slurry containing a negative electrode active material, a binder material, etc. on the negative electrode current collector 54, drying the coating film, and then performing rolling to form the negative electrode active material layer 56 on the negative electrode current collector 54.

[0072] The separator 38d uses, for example, a porous sheet having ion permeability and insulation. Specific examples of the porous sheet include microporous membranes, woven fabrics, non-woven fabrics, etc. As the material of the separator 38d, olefin-based resins such as polyethylene and polypropylene, cellulose, etc. are suitable. The separator 38d can also be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. In addition, it can be a multi-layer separator including a polyethylene layer and a polypropylene layer, or a separator in which a material such as an aromatic polyamide-based resin or ceramic is coated on the surface of the separator 38d.

[0073] Examples of the material constituting the elastomer 40 include thermosetting elastomers such as natural rubber, polyurethane rubber, silicone rubber, fluororubber, etc., thermoplastic elastomers such as polystyrene, olefin, polyurethane, polyester, polyamide, etc. It should be noted that these materials can also be foamed materials. In addition, heat insulating materials loaded with porous materials such as silica xerogel can also be exemplified.

[0074] In the present embodiment, it is preferable to define the compressive elastic moduli of the negative electrode active material layer 56, the separator 38d, and the elastomer 40 as follows. Preferably, the compressive elastic modulus of the separator 38d is smaller than that of the negative electrode active material layer 56, and the compressive elastic modulus of the elastomer 40 is smaller than that of the separator 38d. That is, the compressive elastic moduli are in the order of negative electrode active material layer 56 > separator 38d > elastomer 40. Thus, among the above, the negative electrode active material layer 56 is the most difficult to deform, and the elastomer 40 is the easiest to deform. By defining the compressive elastic moduli of the respective members as described above, for example, the retention of the electrolytic solution in the electrode body 38 is improved, and thus an increase in resistance during high-rate charge and discharge can be suppressed. For example, considering aspects such as effectively suppressing an increase in resistance during high-rate charge and discharge, the compressive elastic modulus of the separator 38d is preferably 0.3 to 0.7 times, more preferably 0.4 to 0.6 times, the compressive elastic modulus of the negative electrode active material layer 56. The compressive elastic modulus of the elastomer 40 may be in the range of 5 MPa to 120 MPa, preferably in the range of 25 MPa to 100 MPa.

[0075] The compressive elastic modulus is calculated by dividing the amount of deformation in the thickness direction of the sample by the compression area and multiplying by the sample thickness when a predetermined load is applied to the sample in the thickness direction. That is, according to the following formula: Compressive elastic modulus (MPa) = Load (N) / Compression area (mm 2 ) × (Amount of deformation of the sample (mm) / Thickness of the sample (mm)). However, in the case of measuring the compressive elastic modulus of the negative electrode active material layer 56, the compressive elastic modulus of the negative electrode current collector 54 is measured, and the compressive elastic modulus of the negative electrode 38b in which the negative electrode active material layer 56 is formed on the negative electrode current collector 54 is measured. Then, based on the compressive elastic moduli of the negative electrode current collector 54 and the negative electrode 38b, the compressive elastic modulus of the negative electrode active material layer 56 is calculated. In addition, in the case of obtaining the compressive elastic modulus of the negative electrode active material layer 56 from the fabricated negative electrode 38b, the compressive elastic modulus of the negative electrode 38b is measured, and the compressive elastic modulus of the negative electrode current collector 54 obtained by shaving off the negative electrode active material layer 56 from the negative electrode 38b is measured, and based on these measured compressive elastic moduli, the compressive elastic modulus of the negative electrode active material layer 56 is calculated.

[0076] Examples of the method for adjusting the compressive elastic modulus of the negative electrode active material layer 56 include a method of adjusting the rolling force applied to the negative electrode composite material slurry formed on the negative electrode current collector 54. In addition, for example, by changing the material and physical properties of the negative electrode active material, the compressive elastic modulus of the negative electrode active material layer 56 can also be adjusted. It should be noted that the adjustment of the pressure elastic modulus of the negative electrode active material layer 56 is not limited to the above. The compressive elastic modulus of the separator 38d is adjusted, for example, by material selection, control of the porosity, pore diameter, etc. The compressive elastic modulus of the elastic body 40 is adjusted, for example, by material selection, shape, etc.

[0077] The elastic body 40 may exhibit a uniform compressive elastic modulus on one surface, but may also have a structure with different in-plane deformation ease as described below.

[0078] Figure 7 It is a schematic perspective view showing an example of the elastic body. Figure 7 The shown elastic body 40 has a soft portion 44 and a hard portion 42. The hard portion 42 is located at a position closer to the outer edge portion of the elastic body 40 than the soft portion 44. Figure 7 In the shown elastic body 40, there is a structure in which the hard portions 42 are arranged on both end sides in the second direction Y, and the soft portion 44 is arranged between the two hard portions 42. The soft portion 44 is preferably arranged to overlap with the center of the long side surface of the housing 13 when viewed from the first direction X, and is arranged to overlap with the center of the electrode body 38. In addition, the hard portion 42 is preferably arranged to overlap with the outer edge of the long side surface of the housing 13 when viewed from the first direction X, and is arranged to overlap with the outer edge of the electrode body 38.

[0079] As described above, the swelling of the non-aqueous electrolyte secondary battery 10 is mainly caused by the swelling of the electrode body 38. And the closer the electrode body 38 is to the center, the greater the swelling. That is, the closer the electrode body 38 is to the center, the greater the displacement in the first direction X, and the smaller the displacement from the center toward the outer edge. In addition, along with the displacement of the electrode body 38, the closer the portion of the non-aqueous electrolyte secondary battery 10 is to the center of the long side surface of the housing 13, the greater the displacement in the first direction X, and the smaller the displacement from the center of the long side surface of the housing 13 toward the outer edge. Therefore, when Figure 7 the shown elastic body 40 is arranged inside the housing 13, the elastic body 40 can have the soft portion 44 bear the larger load generated by the larger displacement of the electrode body 38, and the hard portion 42 bear the smaller load generated by the smaller displacement of the electrode body 38. In addition, when Figure 7 the shown elastic body 40 is arranged outside the housing 13, the elastic body 40 can have the soft portion 44 bear the larger load generated by the larger displacement of the non-aqueous electrolyte secondary battery 10, and the hard portion 42 bear the smaller load generated by the smaller displacement of the non-aqueous electrolyte secondary battery 10.

[0080] Figure 7 The shown elastomer 40 has a recess 46 that is recessed in the first direction X. When a load is applied from the non-aqueous electrolyte secondary battery 10 or the electrode body 38 to the non-recess-forming portion adjacent to the recess 46, a part of it can be displaced toward the recess 46 side. Therefore, by providing the recess 46, it is possible to make the non-recess-forming portion easily deformable. Here, in order to make the soft portion 44 more easily deformable than the hard portion 42, it is preferable that, when viewed from the first direction X, the ratio of the area of the recess 46 to the area of the soft portion 44 is larger than the ratio of the area of the recess 46 to the area of the hard portion 42. It should be noted that in Figure 7 In the shown elastomer 40, the recess 46 is provided only in the soft portion 44, but the recess 46 may also be provided in the hard portion 42.

[0081] The recess 46 includes a core portion 46a and a plurality of wire portions 46b. The core portion 46a is circular and is disposed at the center of the elastomer 40 when viewed from the first direction X. The plurality of wire portions 46b extend radially from the core portion 46a. By the radial extension of the wire portions 46b, the closer to the core portion 46a, the higher the proportion of the wire portions 46b and the fewer the non-recess-forming portions. Therefore, the non-recess-forming portion in the region closer to the core portion 46a is more easily deformable.

[0082] In addition, although not shown in the figure, the elastomer 40 may have a plurality of through-holes that penetrate the elastomer 40 in the first direction X instead of or together with the aforementioned recess 46. By providing the through-holes, it is possible to make the non-through-hole-forming portion easily deformable. Therefore, in order to make the soft portion 44 more easily deformable than the hard portion 42, it is preferable that, when viewed from the first direction X, the ratio of the area of the through-holes to the area of the soft portion 44 is larger than the ratio of the area of the through-holes to the area of the hard portion 42.

[0083] Other examples of the elastomer will be described below.

[0084] Figure 8A partial schematic cross-sectional view of an elastomer in a state of being clamped between an electrode body and a housing. The elastomer 40 bears a load from the electrode body 38 in the stacking direction (first direction X) of the electrode body 38. The elastomer 40 has a base material 42a formed with a hard portion 42 having a predetermined hardness and a soft portion 44 softer than the hard portion 42. The hard portion 42 is a protruding portion protruding from the base material 42a toward the electrode body 38, and breaks or plastically deforms when a load above a predetermined level is applied. The soft portion 44 is in a sheet shape and is disposed at a position closer to the electrode body 38 than the base material 42a formed with the hard portion 42. However, the soft portion 44 is separated from the electrode body 38. The soft portion 44 has a through hole 44a at a position overlapping the hard portion 42 when viewed from the first direction X, the hard portion 42 penetrates through the through hole 44a, and the tip of the hard portion 42 protrudes from the soft portion 44.

[0085] When the shape of the hard portion 42 of the elastomer 40 changes, the elastomer 40 transfers from the first state of bearing the load from the electrode body 38 by the hard portion 42 to the second state of bearing the load by the soft portion 44. That is, the elastomer 40 initially bears the load in the stacking direction of the electrode body 38 (first state) caused by the expansion of the electrode body 38 by the hard portion 42. After that, due to some reason, the expansion amount of the electrode body 38 increases, and when a load that cannot be borne by the hard portion 42 is applied to the hard portion 42, the hard portion 42 breaks or plastically deforms, the electrode body 38 comes into contact with the soft portion 44, and the soft portion 44 bears the load in the stacking direction of the electrode body 38 (second state).

[0086] It should be noted that in the case of an elastomer composed of an uneven shape, the compression elastic modulus is calculated according to the compression elastic modulus (MPa) = load (N) / projected area of the elastomer in the plane direction (mm 2 ) × (deformation amount of the elastomer (mm) / thickness of the elastomer up to the convex portion (mm)).

[0087] The electrolyte is, for example, a non-aqueous electrolyte containing a supporting salt in an organic solvent (non-aqueous solvent), etc. As the non-aqueous solvent, esters, ethers, nitriles, amides, and a mixed solvent of two or more of them are used, for example. As the supporting salt, lithium salts such as LiPF 6 etc. are used.

[0088] <Example>

[0089] Hereinafter, the present disclosure will be further described by way of examples, but the present disclosure is not limited to these examples.

[0090] <Example 1>

[0091] [Fabrication of positive electrode]

[0092] As the positive electrode active material, a material represented by the general formula LiNi 0.82Co 0.15 Al 0.03 O 2 The lithium transition metal composite oxide represented thereby. The positive electrode active material, acetylene black, and polyvinylidene fluoride are mixed at a solid component mass ratio of 97:2:1, and N-methyl-2-pyrrolidone (NMP) is used as a dispersion medium to prepare a positive electrode composite material slurry.

[0093] As the positive electrode current collector, an Al-Mg alloy foil with a thermal conductivity of 150 W / (m·K), a Mg content of 1.5 mass%, a liquidus temperature of 651 °C, and a Young's modulus of 68.6 kN / mm 2 is prepared.

[0094] The above positive electrode composite material slurry is coated on both sides of the above Al-Mg alloy foil. After drying the coating film and performing rolling, it is cut into a predetermined electrode size to obtain a positive electrode having a positive electrode active material layer formed on both sides of the positive electrode current collector.

[0095] [Fabrication of negative electrode]

[0096] Graphite particles as the negative electrode active material, a dispersion of SBR, and CMC-Na are mixed at a solid component mass ratio of 100:1:1.5, and water is used as a dispersion medium to prepare a negative electrode composite material slurry. The negative electrode composite material slurry is coated on both sides of a negative electrode current collector made of a copper foil. After drying the coating film and performing rolling, it is cut into a predetermined electrode size to obtain a negative electrode having a negative electrode active material layer formed on both sides of the negative electrode current collector. When fabricating the negative electrode, the compressive elastic modulus of the negative electrode active material layer is measured, and the result is 660 MPa.

[0097] [Preparation of electrolyte]

[0098] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed at a volume ratio of 3:3:4. LiPF is dissolved in this mixed solvent at a concentration of 1.4 mol / L 6 to prepare an electrolyte.

[0099] [Fabrication of non-aqueous electrolyte secondary battery]

[0100] They are laminated in the order of the negative electrode, a separator with a compressive elastic modulus of 120 MPa, and the positive electrode. After winding them, they are formed into a flat shape to make a flat wound type electrode body. Then, the negative electrode and the positive electrode are connected to the positive electrode terminal and the negative electrode terminal, and they are housed in an outer package made of an aluminum laminate. After injecting the above electrolyte, the opening of the outer package is sealed to fabricate a non-aqueous electrolyte secondary battery.

[0101] A non-aqueous electrolyte secondary battery is fabricated by sandwiching a pair of elastomers (foamed polyurethane having a compressive elastic modulus of 60 MPa), and further, they are sandwiched and fixed by a pair of end plates to fabricate a secondary battery module.

[0102] <Example 2>

[0103] As the positive current collector, an Al-Mg alloy foil having a thermal conductivity of 138 W / (m·K), an Mg content of 2.4 mass%, a liquidus temperature of 653 °C, and a Young's modulus of 70.6 kN / mm 2 is used, and in other respects, a secondary battery module is fabricated in the same manner as in Example 1.

[0104] <Example 3>

[0105] As the positive current collector, an Al-Mg alloy foil having a thermal conductivity of 117 W / (m·K), an Mg content of 4.7 mass%, a liquidus temperature of 640 °C, and a Young's modulus of 70.6 kN / mm 2 is used, and in other respects, a secondary battery module is fabricated in the same manner as in Example 1.

[0106] <Example 4>

[0107] As the positive current collector, an Al-Mg alloy foil having a thermal conductivity of 65 W / (m·K), an Mg content of 93 mass%, a liquidus temperature of 595 °C, and a Young's modulus of 45 kN / mm 2 is used, and in other respects, a secondary battery module is fabricated in the same manner as in Example 1.

[0108] <Example 5>

[0109] As the positive current collector, the Al-Mg alloy foil of Example 3 is used, and as the elastomer, foamed polyurethane having a compressive elastic modulus of 5 MPa is used. In other respects, a secondary battery module is fabricated in the same manner as in Example 1.

[0110] <Example 6>

[0111] As the positive current collector, the Al-Mg alloy foil of Example 3 is used, and as the elastomer, foamed polyurethane having a compressive elastic modulus of 120 MPa is used. In other respects, a secondary battery module is fabricated in the same manner as in Example 1.

[0112] <Comparative Example 1>

[0113] As the positive current collector, an Al foil having a thermal conductivity of 190 W / (m·K), an Mg content of 0 mass%, a liquidus temperature of 650 °C, and a Young's modulus of 68.6 kN / mm 2 is used, and in other respects, a secondary battery module is fabricated in the same manner as in Example 1.

[0114] <Comparative Example 2>

[0115] As the positive current collector, an Al foil with a thermal conductivity of 180 W / (m·K), a Mg content of 0 mass%, a liquidus temperature of 610 °C, and a Young's modulus of 73.5 kN / mm 2 was used, and a secondary battery module was produced in the same manner as in Example 1 except for this.

[0116] <Comparative Example 3>

[0117] As the positive current collector, the Al-Mg alloy foil of Example 3 was used, a separator with a compressive elastic modulus of 230 MPa was used, and as the elastomer, a foamed polyurethane with a compressive elastic modulus of 200 MPa was used. A secondary battery module was produced in the same manner as in Example 1 except for this.

[0118] [Measurement of Internal Resistance of Battery]

[0119] For the secondary battery modules of each example and each comparative example, the internal resistance of the battery was measured under the following conditions. The secondary battery module adjusted to a charged state of SOC 60% was subjected to a constant current discharge at a rate of 5C for 10 seconds at a temperature of 25 °C, and the voltage drop (V) was calculated. Then, the value of the voltage drop (V) was divided by the corresponding current value (I) to calculate the internal resistance of the battery (Ω).

[0120] [Measurement of Heat Release of Battery in Nail Penetration Test]

[0121] For the secondary battery modules of each example and each comparative example, at a temperature of 25 °C, the charged state was adjusted to SOC 100%. Next, a needle with a radius of 0.5 mm and a tip curvature of φ0.9 mm was inserted at a speed of 0.1 mm / sec in the thickness direction of the non-aqueous electrolyte secondary battery to connect the positive electrode and the negative electrode, causing an internal short circuit to occur. Then, a galvanometer was connected between the positive and negative electrodes, and the amount of current flowing through the external load during the short circuit was measured to calculate the heat release.

[0122] Table 1 shows the physical properties of the positive current collector, elastomer, separator, and negative electrode active material layer used in each example and each comparative example, as well as the test results of each example and each comparative example.

[0123] [Table 1]

[0124]

[0125] In Examples 1 to 6 using a positive current collector with an elastomer having a compressive elastic modulus of 5 MPa to 120 MPa, containing Al and elements other than Al, and a thermal conductivity in the range of 65 W / (m·K) to 150 W / (m·K), the heat release amount of the battery in the nail penetration test was suppressed compared to Comparative Examples 1 to 3 that did not satisfy the above requirements.

[0126] For the secondary battery modules of each example and each comparative example, at a temperature of 25°C, constant current charging was performed at a constant current of 0.33C until the voltage reached 4.2V, and then constant current discharging was performed at a constant current of 0.33C until the voltage reached 3.0V. This charge-discharge cycle was repeated 1000 times. Then, the secondary battery module was disassembled, and the flat wound electrode body was taken out to confirm whether the positive current collector at the corner of the electrode body was broken. As a result, only in Comparative Example 3, the positive current collector at the corner was broken.

Claims

1. A secondary battery module comprising: at least one non-aqueous electrolyte secondary battery; and an elastic body arranged together with the non-aqueous electrolyte secondary battery and receiving a load from the non-aqueous electrolyte secondary battery in the arrangement direction, in, The nonaqueous electrolyte secondary battery comprises: an electrode body formed by laminating a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and a case for accommodating the electrode body. The compressive elastic modulus of the elastomer is 60MPa to 120MPa, The positive electrode includes a positive electrode current collector containing Al and an element other than Al, and the thermal conductivity of the positive electrode current collector is 65 W / (m·K) to 150 W / (m·K).

2. The secondary battery module according to claim 1, in, The Young's modulus of the positive current collector is 45 kN / mm 2 to 73.5 kN / mm 2 .

3. The secondary battery module according to claim 1 or 2, in, The element other than Al includes Mg, and a content of Mg in the positive electrode current collector is 1.5 mass % or more.

4. The secondary battery module according to claim 1 or 2, in, The liquidus temperature of the positive electrode current collector is 650° C. or lower.

5. The secondary battery module according to claim 1 or 2, in, The compressive elastic modulus of the separator is smaller than the compressive elastic modulus of the negative electrode active material layer constituting the negative electrode, The elastic body has a compressive elastic modulus smaller than that of the separator.

6. A non-aqueous electrolyte secondary battery comprising: an electrode body formed by stacking a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; an elastic body that receives a load from the electrode body in a stacking direction of the electrode body; and a casing that accommodates the electrode body and the elastic body. in, The compressive elastic modulus of the elastomer is 60MPa to 120MPa, The positive electrode includes a positive electrode current collector containing Al and an element other than Al, and the thermal conductivity of the positive electrode current collector is 65 W / (m·K) to 150 W / (m·K).

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