Non-aqueous electrolyte secondary battery and battery module

Abstract

The present technology provides a nonaqueous electrolyte secondary battery and a battery module. The nonaqueous electrolyte secondary battery includes an electrode body and an electrolyte solution. The electrode body includes a laminate. The laminate includes a positive electrode plate, a negative electrode plate, and a separator. The separator separates the positive electrode plate from the negative electrode plate. The separator includes a porous resin layer. The porous resin layer includes a polyolefin-based material. The negative electrode plate includes a negative electrode active material layer. The negative electrode active material layer includes negative electrode active material particles. The negative electrode active material layer is in direct contact with the porous resin layer. The negative electrode active material layer has a puncture resistance of 0.60 N / mm or more.

Description

TECHNICAL FIELD

[0001] The present technology relates to a nonaqueous electrolyte secondary battery and a battery module. BACKGROUND

[0002] A protective layer configured on the surface of a negative electrode active material layer is disclosed in International Publication No. 2016 / 163115. SUMMARY

[0003] In the manufacturing process of a nonaqueous electrolyte secondary battery (in the present specification, can be simply referred to as "battery"), it is conceivable that a metal piece (foreign matter) is mixed in the battery. The metal piece is, for example, likely to be a cutting chip of an electrode plate, a welding spatter of various members, or the like.

[0004] For example, it is conceivable that a metal piece is attached to a positive electrode plate. The metal piece attached to the positive electrode plate is placed in a high potential environment. In the high potential environment, the metal piece is more likely to be oxidized, and is likely to be dissolved in an electrolyte. The metal dissolved in the electrolyte is likely to be deposited on the surface of a negative electrode plate. The metal is likely to be deposited in a needle shape. The deposition of the needle-shaped metal is, for example, likely to be reflected in a decrease in voltage. In the past, in order to detect the needle-shaped metal, for example, a voltage decrease test is performed at the time of manufacturing of the battery.

[0005] For example, it is also conceivable that a metal piece is attached to a negative electrode plate. The metal piece attached to the negative electrode plate is placed in a low potential environment. In the low potential environment, the dissolution rate of the metal piece is likely to become very low. At the time point of the voltage decrease test, in the case where the amount of dissolution of the metal piece is small (that is, in the case where the amount of deposition of the needle-shaped metal is small), it is considered that it is difficult to detect the decrease in voltage due to the deposition of the needle-shaped metal. Furthermore, in the case where the metal piece before dissolution is not in a needle shape but, for example, in a shape with a small aspect ratio, it is considered that it is also difficult to detect the decrease in voltage due to the metal piece before dissolution. That is, it is considered that it is difficult to detect the metal piece attached to the negative electrode plate by the voltage decrease test at the time of manufacturing.

[0006] As a method of detecting the metal piece, a withstand voltage test (dielectric breakdown test) can also be considered. However, in the past, in the withstand voltage test, there has been a tendency that it is difficult to detect the metal piece attached to the negative electrode plate.

[0007] When the metal piece attached to the negative electrode plate is not detected at the time of manufacturing of the battery, after the start of use of the battery, it is likely that a voltage failure will occur due to the metal piece. As a countermeasure against the metal piece attached to the negative electrode plate, for example, a protective layer (ceramic layer) is introduced between the negative electrode plate and a spacer. However, since the protective layer is interposed between the negative electrode plate and the spacer, there is a possibility that the output of the battery will decrease.

[0008] An object of the present technology is to improve the detection sensitivity of the metal piece attached to the negative electrode plate.

[0009] Hereinafter, the structure and the effect of the present technology will be described. However, the mechanism of action of the present specification contains a presumption. The mechanism of action does not limit the scope of the present technology.

[0010] 1. The nonaqueous electrolyte secondary battery includes an electrode body and an electrolyte solution. The electrode body includes a laminate. The laminate includes a positive electrode plate, a negative electrode plate, and a separator. The separator separates the positive electrode plate from the negative electrode plate. The separator includes a porous resin layer. The porous resin layer includes a polyolefin-based material. The negative electrode plate includes a negative electrode active material layer. The negative electrode active material layer includes negative electrode active material particles. The negative electrode active material layer is in direct contact with the porous resin layer. The negative electrode active material layer has a puncture resistance of 0.60 N / mm or more.

[0011] The puncture resistance is obtained by the following formula (a):

[0012] Z = Y / X... (a).

[0013] In the above formula (a), "Z" represents the puncture resistance. "Y" represents the maximum stress in the puncture test. "X" represents the displacement at the time point at which the maximum stress is obtained. In the puncture test, a needle having a tip radius of 10 μm is vertically pierced at a speed of 10 μm / s with respect to the surface of the negative electrode active material layer.

[0014] In the manufacturing process of the battery, a metal piece attached to the surface of the negative electrode active material layer can possibly penetrate the surface of the negative electrode active material layer. It is considered that this is because the surface of the negative electrode active material layer is soft. It is considered that, since the metal piece is buried in the negative electrode active material layer, it is difficult to detect the insulation breakdown caused by the metal piece in the voltage resistance test.

[0015] It is considered that the puncture resistance of the present technology represents the difficulty of penetration of the metal piece. That is, it is considered that the greater the puncture resistance of the negative electrode active material layer, the more difficult it is for the metal piece to penetrate the surface of the negative electrode active material layer. When the puncture resistance is 0.60 N / mm or more, it is expected that a desired detection sensitivity can be obtained in the voltage resistance test. It is considered that this is because the metal piece is easily projected from the surface of the negative electrode plate since it is difficult to bury the metal piece in the negative electrode active material layer.

[0016] 2. Also, the porous resin layer can have, for example, a thickness retention rate of 91.8% to 93.0%. The thickness retention rate is obtained by the following formula (β):

[0017] Tr = (T1 / T0) x 100... (β).

[0018] In the above formula (β), "Tr" represents a thickness retention rate. "T0" represents the thickness of the porous resin layer. "T1" represents the thickness of the porous resin layer in a state where the pressure is removed after the porous resin layer is compressed in the thickness direction with a pressure of 13.9 MPa.

[0019] The thickness retention rate of the present technology can be an index of the creep resistance, for example. That is, it can be considered that the higher the thickness retention rate, the more difficult it is for the porous resin layer to generate creep.

[0020] For example, in a battery module, a compression force is applied to a battery by restraining the periphery of the battery. Therefore, a spacer (porous resin layer) in the battery is continuously subjected to a pressure. Since the porous resin layer is continuously subjected to a pressure, the porous resin layer can generate creep. The pressure of 13.9 MPa in the above formula (β) can be assumed to be a pressure to which the porous resin layer is subjected at the time of restraint of the battery.

[0021] As described above, the detection sensitivity of the metal sheet attached to the negative electrode plate of the battery of the present technology is high. Therefore, it can be expected that a metal sheet of a somewhat large size is detected in the voltage resistance test. However, it can also be possible that a metal sheet of a very small size cannot be detected in the voltage resistance test.

[0022] Even if a metal sheet of a small size passes the voltage resistance test, it can be possible that voltage failure does not occur at the time of initial start of use of the battery. This is because the metal sheet is sufficiently small with respect to the thickness of the spacer (porous resin layer). However, a pressure can be concentrated at the joint of the metal sheet and the porous resin layer. If the use of the battery is continued for a long period of time, the porous resin layer can locally generate creep at the joint of the metal sheet and the porous resin layer. Since the porous resin layer is locally thinned due to the creep, it can be possible that voltage failure occurs. In the present specification, this phenomenon is also described as "creep short circuit".

[0023] By making the thickness retention rate 91.8% or more, even if a metal sheet passes the voltage resistance test, it is possible to reduce the generation rate of the creep short circuit. By making the thickness retention rate 93.0% or less, it can be expected that the output is improved.

[0024] 3. It can also be that the negative active material particles have a median value of circularity of 0.60 or more, for example.

[0025] According to the new finding of the present technology, there is a tendency that the higher the circularity of the negative electrode active material particles, the greater the puncture resistance of the negative electrode active material layer becomes. It can be considered that the higher the circularity of the negative electrode active material particles, the more difficult the negative electrode active material particles are to be oriented in one direction at the time of compression of the negative electrode active material layer. It can be considered that, since the negative electrode active material particles are difficult to be oriented in one direction at the time of compression of the negative electrode active material layer, the negative electrode active material particles are difficult to be crushed in the thickness direction of the negative electrode active material layer. It can be considered that, since the negative electrode active material particles are difficult to be crushed in the thickness direction, the metal sheet (foreign matter) is difficult to penetrate into the surface of the negative electrode active material layer. By making the median value of the circularity 0.60 or greater, there is a tendency that the puncture resistance of 0.60 N / mm or greater is easily obtained.

[0026] 4. Also, the porous resin layer can include a first layer, a second layer, and a third layer. The first layer, the second layer, and the third layer are stacked in the thickness direction of the porous resin layer. The second layer is interposed between the first layer and the third layer. The first layer and the third layer each include polypropylene. The second layer includes polyethylene. The porous resin layer satisfies the following relation of formula (γ):

[0027] t2 / {(t1+t3) x 0.5} ≤ 1.5 … (γ).

[0028] In the above formula (γ), "t1" represents the thickness of the first layer. "t2" represents the thickness of the second layer. "t3" represents the thickness of the third layer.

[0029] Also, the porous resin layer can have, for example, a three-layer structure. In the porous resin layer of the three-layer structure, when the above formula (γ) is satisfied, there is a tendency that the thickness retention rate becomes high.

[0030] 5. Also, the ratio of the thickness of the negative electrode active material layer to the thickness of the laminate can be, for example, 0.35 to 0.45.

[0031] There is a tendency that the greater the ratio of the thickness of the negative electrode active material layer to the thickness of the laminate, the more the pressure is easily dispersed around the metal sheet (foreign matter) mixed into the laminate. By making the ratio of the thickness of the negative electrode active material layer to the thickness of the laminate 0.35 or greater, it is possible to expect, for example, a reduction in the generation rate of creep short circuit. By making the ratio of the thickness of the negative electrode active material layer to the thickness of the laminate 0.45 or less, it is possible to expect, for example, an improvement in the detection sensitivity of the metal sheet in the withstand voltage test.

[0032] 6. Also, in the electrode body, the positive electrode plate can have, for example, a stacking number of 60 to 80.

[0033] There is a tendency that the more the number of laminated positive electrode plates is, the more the pressure is easily dispersed around the metal sheet (foreign matter) mixed into the electrode body. By making the number of laminated positive electrode plates 60 or more, for example, it is possible to expect a reduction in the generation rate of creep short circuit. By making the number of laminated positive electrode plates 80 or less, for example, it is possible to expect an improvement in the detection sensitivity of the metal sheet in the withstand voltage test.

[0034] 7. Also, the porous resin layer may, for example, have a thickness of 14 μm to 20 μm.

[0035] 8. Also, the porous resin layer may, for example, have a puncture strength of 3.92 N or less.

[0036] By making the puncture strength of the porous resin layer 3.92 N or less, for example, it is possible to expect an improvement in the detection sensitivity of the metal sheet in the withstand voltage test.

[0037] 9. Also, the negative electrode active material layer may, for example, have a puncture resistance of 0.85 N / mm or less.

[0038] 10. Also, the negative electrode active material particles may, for example, have a median value of the circularity of 0.85 or less.

[0039] 11. A battery module includes a plurality of unit cells. The plurality of unit cells are arranged along an arrangement direction. The arrangement direction is along a laminating direction of positive electrode plates, negative electrode plates, and separators in an electrode body. The plurality of unit cells are respectively subjected to a compression force along the arrangement direction. The plurality of unit cells are respectively the nonaqueous electrolyte secondary batteries described in 1 to 10 above.

[0040] The above and other objects, features, aspects and advantages of the present technology will become more apparent from the following detailed description of the technology taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the technology. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a schematic diagram showing an example of the structure of the nonaqueous electrolyte secondary battery of the present embodiment.

[0042] Figure 2 is a schematic diagram showing an example of the structure of the electrode body of the present embodiment.

[0043] Figure 3 is a schematic cross-sectional view showing an example of the structure of the electrode body of the present embodiment.

[0044] Figure 4 is a first explanatory diagram of the puncture test.

[0045] Figure 5 is a second explanatory diagram of the puncture test.

[0046] Figure 6is a graph showing a relationship between a median of a circularity of the negative electrode active material particles and a puncture resistance of the negative electrode active material layer.

[0047] Figure 7 is a schematic cross-sectional view showing an example of a multilayer structure.

[0048] Figure 8 is a graph showing a relationship between a thickness retention rate and a thickness ratio of the second layer.

[0049] Figure 9 is a schematic view showing an example of the battery module of the present embodiment. DETAILED DESCRIPTION

[0050] Hereinafter, an embodiment of the present technology (in the present specification, also described as "the present embodiment") will be described. However, the following description does not limit the scope of the present technology. For example, for the description related to the effects in the present specification, the scope of the present technology is not limited in the entire range in which the effects can be exerted.

[0051] <Definitions of Terms and the Like>

[0052] In the present specification, the description such as "comprise, include, have" and their variations (for example, "be composed of, encompass, involve, contain, carry, support, hold, and the like") is in an open form. For the open form, an additional element can be included in addition to the essential element, or the additional element can not be included. The description such as "consist of" is in a closed form. The description such as "consist essentially of" is in a semi-closed form. For the semi-closed form, in a range that does not hinder the purpose of the present technology, an additional element can be further included in addition to the essential element. For example, an element that is generally assumed in the field to which the present technology pertains (for example, unavoidable impurities, and the like) can be included as the additional element.

[0053] In the present specification, the expressions such as "may" and "can" are not used in the meaning of obligation, that is, the meaning of "must", but are used in the meaning of permission, that is, the meaning of "possibility of having".

[0054] In the present specification, with respect to an element expressed by a singular form (a, an, the), the plural is also included unless it is specifically stated otherwise. For example, "a particle" means "a collection of particles (powder, powder, particle group)" in addition to "one particle".

[0055] In the present specification, with respect to a numerical range such as "91.8 to 93.0%" and "91.8 to 93.0%", unless otherwise specified, the upper limit value and the lower limit value are included. That is, "91.8 to 93.0%" and "91.8 to 93.0%" both mean a numerical range of "91.8% or more and 93.0% or less". In addition, a value arbitrarily selected from a numerical range can be set as a new upper limit value and a lower limit value. For example, a new numerical range can be set by arbitrarily combining a value within a numerical range with a value described in other parts of the present specification, in a table, in a figure, and the like.

[0056] In the present specification, all numerical values are modified by the term "about". The term "about" can mean ±5%, ±3%, ±1%, and the like, for example. All numerical values are approximate values that can be changed depending on the utilization form of the present technology. All numerical values are shown with significant digits. All measured values and the like can be processed by rounding off based on the number of significant digits. All numerical values can include errors associated with the detection limit of a measuring device and the like, for example.

[0057] In the present specification, for example, in the case of expressing a compound by a stoichiometric composition formula such as "LiCoO2", the stoichiometric composition formula is only a representative example. The composition ratio can also be non-stoichiometric. For example, in the case of expressing lithium cobaltate as "LiCoO2", unless otherwise specified, lithium cobaltate is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2", and can include Li, Co, and O in an arbitrary composition ratio. Furthermore, doping and substitution based on trace elements can also be allowed.

[0058] The geometric terms in the present specification (for example, "parallel", "perpendicular", "orthogonal", and the like) should not be understood in a strict sense. For example, "parallel" can also be slightly deviated from the strict sense of "parallel". The geometric terms in the present specification can include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationship in each figure is sometimes different from the actual dimensional relationship. In order to facilitate understanding of the present technology, there are cases where the dimensional relationship (length, width, thickness, and the like) in each figure is changed. Furthermore, there are cases where a part of the structure is omitted.

[0059] <Non-aqueous electrolyte secondary battery>

[0060] Figure 1is a schematic diagram showing an example of the structure of the nonaqueous electrolyte secondary battery of the present embodiment.

[0061] The battery 100 can be used for any purpose. The battery 100 can also be used as a main power source or a power-assist power source in an electric vehicle or the like, for example. A battery module or a battery pack can also be formed by connecting a plurality of batteries 100. The battery 100 can also have a rated capacity of 1 to 200 Ah, for example.

[0062] The battery 100 includes an exterior body 90. The exterior body 90 is square (flat rectangular parallelepiped). The exterior body 90 can also be made of an aluminum (Al) alloy, for example. The exterior body 90 houses the electrode body 50 and an electrolyte (not shown). That is, the battery 100 includes the electrode body 50 and the electrolyte.

[0063] The exterior body 90 can also include a sealing plate 91 and an exterior can 92, for example. The sealing plate 91 plugs an opening of the exterior can 92. The sealing plate 91 can be joined to the exterior can 92 by laser processing or the like, for example. The exterior body 90 can have any form. The exterior body 90 can also be a bag or the like made of an Al laminate film, for example. That is, the exterior body 90 can be a bag or the like made of an Al laminate film.

[0064] The positive electrode terminal 81 and the negative electrode terminal 82 are provided to the sealing plate 91. An injection port (not shown), a gas discharge valve (not shown), or the like can also be provided to the sealing plate 91. The electrolyte can be injected into the interior of the exterior body 90 from the injection port. The injection port can be closed by a sealing plug or the like, for example. The positive electrode current collecting member 71 connects the positive electrode terminal 81 to the electrode body 50. The positive electrode current collecting member 71 can also be an Al plate or the like, for example. The negative electrode current collecting member 72 connects the negative electrode terminal 82 to the electrode body 50. The negative electrode current collecting member 72 can also be a copper (Cu) plate or the like, for example.

[0065] Figure 2 is a schematic diagram showing an example of the structure of the electrode body of the present embodiment.

[0066] The electrode body 50 includes the laminate 40. The electrode body 50 can also be substantially composed of the laminate 40. The laminate 40 includes the positive electrode plate 10, the negative electrode plate 20, and the spacer 30. At least a portion of the spacer 30 is interposed between the positive electrode plate 10 and the negative electrode plate 20. The spacer 30 separates the positive electrode plate 10 and the negative electrode plate 20. The laminate 40 can also include a single spacer 30. The laminate 40 can also include two spacers 30. The positive electrode plate 10 can be sandwiched by two spacers 30, for example. The negative electrode plate 20 can be sandwiched by two spacers 30, for example. The laminate 40 can be formed by sequentially stacking the spacer 30 (first spacer), the negative electrode plate 20, the spacer 30 (second spacer), and the positive electrode plate 10, for example.

[0067] The electrode body 50 can be either a wound type or a stacked type, for example. When the electrode body 50 is of the wound type, each of the positive electrode plate 10, the negative electrode plate 20, and the spacer 30 can have a planar shape of a band shape, for example. That is, the stack 40 can have a planar shape of a band shape. By winding the band-shaped stack 40 into a spiral shape, a wound body can be formed. The wound body can also be a cylindrical shape, for example. By compressing the cylindrical wound body in the radial direction, the electrode body 50 in a flat shape can be formed.

[0068] When the electrode body 50 is of the stacked type, each of the positive electrode plate 10, the negative electrode plate 20, and the spacer 30 can have a planar shape of a rectangular shape, for example. That is, the stack 40 can have a planar shape of a rectangular shape. By stacking a plurality of stacks 40 in a prescribed direction, the electrode body 50 can be formed.

[0069] Figure 3 is a schematic cross-sectional view showing an example of the structure of the electrode body of the present embodiment.

[0070] Figure 3 The electrode body 50 of is of the wound type. In Figure 3 A cross section orthogonal to the winding axis is shown in. The electrode body 50 includes a curved portion 51 and a flat portion 52. In the curved portion 51, the stack 40 is curved. In the curved portion 51, the stack 40 can also describe an arc shape. In the flat portion 52, the stack 40 is flat. The flat portion 52 is sandwiched by two curved portions 51. The flat portion 52 connects the two curved portions 51. Further, the electrode body 50 of the stacked type is substantially constituted by the flat portion 52.

[0071] In the electrode body 50, the positive electrode plate 10 can have an arbitrary number of layers. The number of layers of the positive electrode plate 10 indicates the number of times a straight line that crosses the electrode body 50 in the stacking direction intersects the positive electrode plate 10. The stacking direction indicates the direction in which the positive electrode plate 10, the negative electrode plate 20, and the spacer 30 are stacked in the electrode body 50. The stacking direction in the electrode body 50 of the wound type is parallel to the thickness direction of the positive electrode plate 10, the negative electrode plate 20, and the spacer 30 in the flat portion 52 (D-axis direction of). Figure 3 The stacking direction in the electrode body 50 of the stacked type is parallel to the thickness direction of the positive electrode plate 10, the negative electrode plate 20, and the spacer 30.

[0072] There is a tendency that the more layers the positive electrode plate 10 has, the easier it is for pressure to disperse around the metal sheet (foreign matter) mixed into the electrode body 50. The positive electrode plate 10 may, for example, have a layer count of 60 to 80. By having a layer count of 60 or more for the positive electrode plate 10, it is expected, for example, to reduce the occurrence rate of creep short circuits. By having a layer count of 80 or less for the positive electrode plate 10, it is expected, for example, to improve the detection sensitivity of the metal sheet in the withstand voltage test. The positive electrode plate 10 may, for example, have a layer count of 60 to 70. Furthermore, when the electrode body 50 is a stacked type, the layer count of the positive electrode plate 10 indicates the number of positive electrode plate blocks.

[0073] The negative electrode plate 20 may have, for example, 60 to 80 layers. The spacer 30 may have, for example, 120 to 160 layers. The number of layers of the negative electrode plate 20 and the spacer 30 may be counted in the same way as the number of layers of the positive electrode plate 10.

[0074] Negative electrode plate

[0075] The negative electrode plate 20 includes a negative electrode active material layer 22 (see reference). Figure 2 The negative electrode plate 20 may also be substantially composed of a negative electrode active material layer 22. Alternatively, the negative electrode plate 20 may also include a negative electrode substrate 21. For example, the negative electrode active material layer 22 may be disposed on the surface of the negative electrode substrate 21. The negative electrode active material layer 22 may be disposed only on one side of the negative electrode substrate 21. The negative electrode active material layer 22 may be disposed on both the outer and inner sides of the negative electrode substrate 21. The negative electrode substrate 21 is a conductive sheet. The negative electrode substrate 21 may, for example, comprise pure Cu foil, Cu alloy foil, etc. The negative electrode substrate 21 may, for example, have a thickness of 5–30 μm. Alternatively, in the width direction of the negative electrode plate 20 (… Figure 2 Along the W-axis direction, the negative electrode substrate 21 is exposed at one end. The negative electrode current collector 72 (see reference 5) can be joined to the exposed portion of the negative electrode substrate 21. Figure 1 ).

[0076] (Piercing resistance)

[0077] Figure 4 This is the first illustrative diagram of the puncture test.

[0078] The negative electrode active material layer 22 has a puncture resistance of 0.60 N / mm or higher. The puncture resistance can be determined by a puncture test. A needle 5 is prepared. The tip of the needle 5 is spherical. The needle 5 has a tip radius (r) of 10 μm. The needle 5 is made of metal. For example, the needle 5 can also be made of stainless steel. The needle 5 is mounted on the movable part of the puncture testing machine. The negative electrode plate 20 is fixed to the worktable of the puncture testing machine. The needle 5 is inserted perpendicularly to the surface of the negative electrode active material layer 22. The test speed (puncture speed) is 10 μm / s. The test temperature is 25℃ ± 5℃.

[0079] Figure 5 is a second explanatory view of the piercing test.

[0080] The piercing test is performed until the needle 5 penetrates through the negative active material layer 22. In the penetration of the needle 5, the displacement (depth) and stress of the needle 5 are measured. As the displacement increases, the stress also increases. At the time point at which the needle 5 penetrates through the negative active material layer 22, the maximum stress (Y) is shown. After the penetration of the needle 5, the stress turns to decrease. The displacement (X) at the time point at which the maximum stress is obtained is recorded. By dividing the maximum stress (Y) by the displacement (X), the piercing resistance (Z) is calculated (refer to the above-described formula (a)). The piercing resistance (Z) has the dimension of "MT -2 (= M x L x T -2 x L -1 )". The piercing resistance is measured three or more times for one measurement object. The arithmetic mean of the results of three or more times is adopted.

[0081] The greater the piercing resistance of the negative active material layer can be expected, the more the detection sensitivity of the metal sheet in the withstand voltage test can be improved. The piercing resistance may, for example, be 0.67 N / mm or more, 0.74 N / mm or more, or 0.78 N / mm or more. The piercing resistance can have an arbitrary upper limit value. The piercing resistance may, for example, be 0.85 N / mm or less.

[0082] (thickness of the negative active material layer)

[0083] The ratio of the thickness of the negative active material layer 22 to the thickness of the laminate 40 may, for example, be 0.35 to 0.45. There is a tendency that the greater the ratio of the thickness of the negative active material layer 22 to the thickness of the laminate 40, the more the pressure is easily dispersed around the metal sheet (foreign matter) mixed into the laminate 40. By making the ratio of the thickness of the negative active material layer 22 to the thickness of the laminate 40 0.35 or more, it can be expected, for example, that the generation rate of the creep short circuit is reduced. By making the ratio of the thickness of the negative active material layer 22 to the thickness of the laminate 40 0.45 or less, it can be expected that the detection sensitivity of the metal sheet in the withstand voltage test is improved.

[0084] The thickness of the laminate 40 indicates the total of the thicknesses of the positive plate 10, the negative plate 20, and the spacer 30 included in the laminate 40. The laminate 40 may, for example, have a thickness of 100 to 200 μm or a thickness of 120 to 180 μm.

[0085] The thickness of the negative electrode active material layer 22 represents the total of the thicknesses of the negative electrode active material layers 22 included in the laminate 40. For example, in the case where the negative electrode active material layer 22 is formed on both surfaces of the negative electrode plate 20, the thickness of the negative electrode active material layer 22 represents the total of the thicknesses of the negative electrode active material layers 22 on both surfaces. The negative electrode active material layer 22 can have a thickness of 40 to 80 μm, for example, or a thickness of 50 to 70 μm. Further, the thickness of the negative electrode active material layer 22 on one surface can be 20 to 40 μm, for example, or 25 to 35 μm.

[0086] The negative electrode active material layer 22 can have a density of 0.5 to 2.0 g / cm 3 , for example, or a density of 1.0 to 1.5 g / cm 3 . The density of the negative electrode active material layer 22 is obtained by dividing the mass of the negative electrode active material layer 22 by the apparent volume of the negative electrode active material layer 22. The apparent volume includes the volume of the voids in the negative electrode active material layer 22.

[0087] (Negative electrode active material particle)

[0088] The negative electrode active material layer 22 includes negative electrode active material particles. The negative electrode active material layer 22 can also be substantially composed of negative electrode active material particles. The negative electrode active material particles can include at least one selected from the group consisting of natural graphite, artificial graphite, silicon, silicon oxide, tin, tin oxide, and Li4Ti5O 12 , for example. The negative electrode active material particles can be composite particles, for example. The negative electrode active material particles can include substrate particles and a coating film, for example. The coating film can coat the surface of the substrate particles. The substrate particles can include natural graphite or the like, for example. The coating film can include amorphous carbon or the like, for example.

[0089] The negative electrode active material particles can have any shape. The negative electrode active material particles can be spherical, massive, flaky, or the like, for example. The negative electrode active material particles can be spheroidized graphite or the like, for example. In the compressed negative electrode active material layer 22, since the negative electrode active material particles have a shape close to a sphere, there is a tendency for the puncture resistance of the negative electrode active material layer 22 to increase. The shape of the negative electrode active material particles in the compressed negative electrode active material layer 22 can be evaluated by the circularity, for example.

[0090] (Circularity)

[0091] Figure 6is a graph showing the relationship between the median of the roundness of the negative electrode active material particles and the puncture resistance of the negative electrode active material layer. It can be seen that the higher the median of the roundness, the greater the puncture resistance of the negative electrode active material layer 22 becomes. The median of the roundness may, for example, be 0.60 or more, 0.69 or more, or 0.78 or more.

[0092] The median of the roundness may, for example, also be 0.85 or less. The roundness may, for example, vary depending on the compression rate of the negative electrode active material layer 22 or the like. By making the median of the roundness 0.85 or less, there is a tendency to easily form a high-density negative electrode active material layer 22.

[0093] The roundness can be measured by the following steps.

[0094] A test piece of a prescribed size is cut out from the compressed negative electrode plate 20. The test piece is embedded in a resin material. By cutting the embedded test piece, a cross-section test sample of the negative electrode active material layer 22 is produced. The cross-section test sample contains a cross-section perpendicular to the surface of the negative electrode active material layer 22. The cross-section test sample is subjected to a cleaning treatment (ion milling treatment). After the cleaning, the cross-section test sample is observed using an SEM (scanning electron microscope), and a cross-section SEM image is obtained. In the cross-section SEM image, 30 negative electrode active material particles are randomly extracted. The roundness of the 30 negative electrode active material particles is measured. The median is found from the 30 roundnesses.

[0095] The roundness of each particle is found by the following formula (δ):

[0096] R = 4πS / L 2 … (δ).

[0097] In the above formula (δ), “R” represents the roundness. “S” represents the area of the cross-section image of the particle. “L” represents the circumference (the length of the outline) of the cross-section image of the particle. The roundness of a perfect circle is 1. That is, the median of the roundness may also be 1 or less.

[0098] (Particle size)

[0099] The negative electrode active material particles may, for example, have a D50 of 5 to 20 μm, a D50 of 9.5 to 15 μm, or a D50 of 10 to 12 μm. The “D50” in this specification is defined as the particle diameter at which the cumulative frequency from the smaller particle diameter side becomes 50% in a particle size distribution on a volume basis. The particle size distribution on a volume basis can be measured by a laser diffraction type particle size distribution measuring device. For example, a laser diffraction type particle size distribution measuring device such as “product name SALD-2200” manufactured by Shimadzu Corporation, or a product equivalent thereto can be used.

[0100] The negative active material particles can have an arithmetic mean diameter of 5 to 20 μm, 9.5 to 15 μm, or 10 to 12 μm. The "arithmetic mean diameter" in the present specification can be measured in the compressed negative active material layer 22. In the above cross-sectional SEM image, the diameters of 30 negative active material particles are measured. The diameter of each negative active material particle represents the distance between the two most distant points on the outline of the negative active material particle. The arithmetic mean of the 30 diameters is taken as the arithmetic mean diameter. Depending on the manufacturing method of the negative plate 20, there can be cases where a difference is produced between the D50 and the arithmetic mean diameter, and cases where the D50 and the arithmetic mean diameter are substantially the same.

[0101] (Any Component)

[0102] The negative active material layer 22 can also contain a conductive material, a binder, or the like in addition to the negative active material particles. For example, the negative active material layer 22 can be substantially composed of 0 to 10% by mass of a conductive material, 0.1 to 10% by mass of a binder, and the remainder negative active material particles. The conductive material can contain any component. The conductive material can contain, for example, carbon black, carbon nanotubes, or the like. The binder can contain any component. The binder can contain, for example, at least one selected from the group consisting of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR).

[0103] <Spacer>

[0104] The spacer 30 contains a porous resin layer. The spacer 30 can be substantially composed of the porous resin layer. The porous resin layer is in direct contact with the negative active material layer 22. Since there is no interposed material between the porous resin layer and the negative active material layer 22, for example, an improvement in output or the like can be expected. Further, the spacer 30 can contain a protective layer or can not contain a protective layer on the surface in contact with the positive active material layer 12.

[0105] The porous resin layer can have, for example, an air permeability of 100 to 400 s / 100 mL. The "air permeability" in the present specification represents the "air resistance" defined by "JIS P 8117:2009". The air permeability is measured by the Gurley test method.

[0106] The porous resin layer can have, for example, a thickness of 10 to 50 μm, 10 to 30 μm, or 14 to 20 μm.

[0107] The porous resin layer has electrical insulation. The porous resin layer contains a polyolefin-based material. The porous resin layer may, for example, also consist essentially of a polyolefin-based material. The polyolefin-based material may, for example, also contain at least one selected from the group consisting of polyethylene (PE) and polypropylene (PP).

[0108] (thickness retention rate)

[0109] The porous resin layer may, for example, also have a thickness retention rate of 91.8 to 93.0%. By making the thickness retention rate 91.8% or greater, even if the metal sheet passes the voltage resistance test, the generation rate of the creep short circuit can be reduced. By making the thickness retention rate 93.0% or less, an increase in output or the like can be expected, for example. The porous resin layer may, for example, have a thickness retention rate of 91.8 to 92.1% or a thickness retention rate of 92.1 to 93.0%.

[0110] The thickness retention rate can be measured by the following steps.

[0111] A test piece of the porous resin layer is cut out from the spacer 30. The test piece may, for example, have a planar size of 2 cm x 2 cm. 140 test pieces are prepared. The test pieces can be collected from a portion having as little permanent deformation as possible. For example, in the case of the electrode body 50 of the winding type, the test pieces can be collected from the curved portion 51 (refer to FIG. 2). In the flat portion 52, it is possible that permanent deformation will occur in the thickness direction of the spacer 30. Figure 3 ) In the flat portion 52, it is possible that permanent deformation will occur in the thickness direction of the spacer 30.

[0112] A planar indenter is prepared. The planar indenter has a square planar shape. The planar indenter is fitted to the movable portion of a compression testing machine. The planar indenter may, for example, have a planar size of 2 cm x 2 cm. The pre-compression thickness (TO) of the test piece is measured. The pre-compression thickness (TO) can be measured by a micrometer (constant pressure type) or the like manufactured by Mitutoyo Corporation.

[0113] A test piece was prepared by stacking 140 test pieces. The test piece was placed on the stage of a compression tester. The test temperature was 25°C ± 5°C. A flat head was used to apply pressure to the test piece. The direction of application of pressure was along the stacking direction of the test pieces included in the test piece. The test speed (rate of increase in pressure) was 6.95 MPa / s. The pressure was brought to the target value (13.9 MPa) within two seconds. At the time point at which the pressure reached the target value, the pressure was released. After the pressure was released, the test piece was left to stand for 30 minutes. After the standing, one test piece was collected from the test piece. The thickness (T1) of the portion of the test piece that had been in contact with the flat head was measured. That is, after the porous resin layer was compressed in the thickness direction by the pressure of 13.9 MPa, the thickness (T1) of the porous resin layer was measured in the state after the pressure was released. The thickness after compression (T1) can also be measured by a micrometer. The thickness retention ratio (Tr) was calculated by dividing the thickness after compression (T1) by the thickness before compression (T0) (see the above formula (β)). The thickness retention ratio (Tr) was expressed in percentage.

[0114] (Multilayered structure)

[0115] The porous resin layer may, for example, also have a single-layered structure. The porous resin layer may, for example, also consist essentially of a PE layer.

[0116] Figure 7 is a schematic cross-sectional view showing an example of a multilayered structure.

[0117] The porous resin layer 31 may, for example, also have a multilayered structure. The porous resin layer 31 may, for example, also have a three-layered structure. The porous resin layer 31 may, for example, include a first layer 31a, a second layer 31b, and a third layer 31c. The first layer 31a, the second layer 31b, and the third layer 31c are stacked in the thickness direction of the porous resin layer 31 (H-axis direction of the porous resin layer 31). Figure 7 The second layer 31b is interposed between the first layer 31a and the third layer 31c.

[0118] Each of the first layer 31a and the third layer 31c may, for example, include PP. Each of the first layer 31a and the third layer 31c may consist essentially of PP. That is, each of the first layer 31a and the third layer 31c may be a PP layer. The second layer 31b may, for example, include PE. The second layer 31b may consist essentially of PE. That is, the second layer 31b may be a PE layer.

[0119] (Thickness ratio of second layer)

[0120] The thickness ratio of the second layer 31b is, for example, 1.5 or less (see the above formula (γ)).

[0121] Figure 8 is a graph showing the relationship between the thickness retention rate and the thickness ratio of the second layer.

[0122] By making the thickness ratio of the second layer 31b 1.5 or less, it can be seen that the thickness retention rate tends to be high. The thickness ratio of the second layer 31b may, for example, be 1.31 or less, or 1.30 or less. The thickness ratio of the second layer 31b may, for example, be 1.0 or more, 1.1 or more, or 1.2 or more.

[0123] Each of the first layer 31a and the third layer 31c may, for example, have a thickness of 1 to 10 μm, or a thickness of 3 to 6 μm. The second layer 31b may, for example, have a thickness of 1 to 15 μm, or a thickness of 5 to 10 μm. Further, the thickness of each layer can be measured by a micrometer after the first layer 31a and the third layer 31c are each peeled from the second layer 31b.

[0124] (Piercing strength)

[0125] The porous resin layer may, for example, have a piercing strength of 3.92 N or less. By making the piercing strength of the porous resin layer 3.92 N or less, it can be expected, for example, that the detection sensitivity of the metal sheet in the withstand voltage test be improved. The porous resin layer may, for example, have a piercing strength of 0.98 to 3.92 N, a piercing strength of 1.96 to 3.92 N, or a piercing strength of 2.94 to 3.92 N.

[0126] The piercing strength can be measured by the following steps.

[0127] A needle is prepared. The needle has a main body diameter of 1 mm. The tip shape of the needle is spherical. The needle has a tip radius of 0.5 mm. The needle is made of metal. The needle may, for example, be made of stainless steel. The needle is fitted to the movable portion of a piercing tester. A test piece is cut out from the porous resin layer. The test piece may, for example, have a planar size of 2 cm x 2 cm. The porous resin layer is fixed to the stage of the piercing tester. The needle is pierced perpendicularly with respect to the surface of the porous resin layer. The test speed (piercing speed) is 2 mm / s. The test temperature is 25°C ± 5°C. The maximum force until the needle penetrates through the porous resin layer is the piercing strength. The piercing strength is measured three or more times for one measurement object. The arithmetic mean of the results of three or more times is adopted.

[0128] Positive electrode sheet

[0129] The positive electrode plate 10 may also include, for example, a positive electrode substrate 11 and a positive electrode active material layer 12 (see reference). Figure 2 The positive electrode substrate 11 is a conductive sheet. The positive electrode substrate 11 may, for example, comprise pure Al foil, Al alloy foil, etc. The positive electrode substrate 11 may, for example, have a thickness of 10–30 μm. Alternatively, the thickness may be such that, in the width direction of the positive electrode plate 10 (… Figure 2 Along the W-axis direction, the positive electrode substrate 11 is exposed at one end. The positive electrode current collector 71 (see reference 1) can be joined to the exposed portion of the positive electrode substrate 11. Figure 1 ).

[0130] The positive electrode active material layer 12 may be disposed on only one side of the positive electrode substrate 11. Alternatively, the positive electrode active material layer 12 may be disposed on both the inner and outer sides of the positive electrode substrate 11. Similar to the thickness of the negative electrode active material layer 22 described above, the thickness of the positive electrode active material layer 12 represents the total thickness of the positive electrode active material layers 12 included in the laminate 40. For example, when the positive electrode active material layer 12 is formed on both sides of the positive electrode plate 10, the thickness of the positive electrode active material layer 12 represents the total thickness of the two positive electrode active material layers 12 on both sides. The positive electrode active material layer 12 may have a thickness of, for example, 20–60 μm or 30–50 μm. Furthermore, the thickness of a single positive electrode active material layer 12 on one side may be, for example, 10–30 μm or 15–25 μm.

[0131] The positive electrode active material layer 12 comprises positive electrode active material particles. These particles may contain any composition. For example, they may also contain at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, in the compositional formula "Li(NiCoMn)O2", the sum of the proportions within parentheses is 1. That is, satisfying "C..." Ni +C Co +C Mn The relationship is "=1". For example, "C" Ni "" indicates the composition ratio of Ni. The sum of the composition ratios only needs to be 1, and the composition ratio of each component is arbitrary.

[0132] The positive electrode active material layer 12 can also contain, for example, a conductive material, a binder, and the like in addition to the positive electrode active material particles. For example, the positive electrode active material layer 12 can also substantially consist of 0.1 to 10% by mass of a conductive material, 0.1 to 10% by mass of a binder, and the remainder of positive electrode active material particles. The conductive material can contain, for example, acetylene black and the like. The binder can contain any component. The binder can contain, for example, polyvinylidene fluoride (PVdF) and the like.

[0133]

[0134] The electrolyte is a liquid electrolyte. The electrolyte contains a solvent and a supporting electrolyte. The solvent is aprotic. The solvent can contain any component. The solvent can contain, for example, at least one selected from the group consisting of vinylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME), methyl formate (MF), methyl acetate (MA), methyl propionate (MP), and γ-butyrolactone (GBL).

[0135] The supporting electrolyte is dissolved in the solvent. The supporting electrolyte can contain, for example, at least one selected from the group consisting of LiPF6, LiBF4, and LiN(FSO2)2. The supporting electrolyte can have, for example, a molar concentration of 0.5 to 2.0 mol / L or a molar concentration of 0.8 to 1.2 mol / L.

[0136] The electrolyte can contain any additive in addition to the solvent and the supporting electrolyte. For example, the electrolyte can contain 0.01 to 5% by mass of an additive. The additive can contain, for example, at least one selected from the group consisting of vinylene carbonate (VC), lithium difluorophosphate (LiPO2F2), lithium fluorosulfonate (FSO3Li), and lithium bis(oxalato)borate (LiBOB).

[0137]

[0138] Figure 9 is a schematic view showing an example of a battery module according to the present embodiment.

[0139] In the present technology, a battery module 200 can also be provided. The battery module 200 contains a plurality of single cells, an end plate 110, and a constraint member 120. The plurality of single cells are each the battery 100 according to the present embodiment. The battery module 200 can contain, for example, 2 to 50 single cells or 4 to 20 single cells.

[0140] ​​The plurality of unit cells are arranged in an arrangement direction (D-axis direction). The arrangement direction is along the stacking direction of the positive electrode plate 10, the negative electrode plate 20, and the spacer 30 in the electrode body 50. The arrangement direction can also be parallel to the stacking direction. The unit cells can be electrically connected to each other, for example, by a bus bar (not shown). The plurality of unit cells can form a series circuit or a parallel circuit, for example.

[0141] Also, an intermediate plate (not shown) can be interposed between the unit cells. The end plate 110 is disposed at both ends in the arrangement direction. The restraint member 120 connects the two end plates 110. The restraint member 120 applies a tensile force to the two end plates 110 in a direction in which the two end plates are brought closer to each other. Thus, the unit cells are each subjected to a compressive force in the arrangement direction. The spacer in the unit cell can also be subjected to a pressure of 13 to 14 MPa, for example. In the battery module 200, for example, the generation rate of a creep short circuit can be expected to be low.

[0142] Embodiment

[0143] Hereinafter, an embodiment of the present technology (also described as "the present embodiment" in the present specification) will be described. However, the following description does not limit the scope of the present technology.

[0144] Manufacture of a battery

[0145] The test batteries (non-aqueous electrolyte secondary batteries) of Nos. 1 to 9 were manufactured as follows.

[0146] No. 1

[0147] Manufacture of a positive electrode plate

[0148] The following materials were prepared.

[0149] Positive electrode active material particles: Li(NiCoMn)O2

[0150] Conductive material: acetylene black

[0151] Binder: PVdF

[0152] Dispersion medium: N-methyl-2-pyrrolidone

[0153] Positive electrode base material: Al alloy foil

[0154] A positive electrode slurry was prepared by mixing the positive electrode active material particles, the conductive material, the binder, and the dispersion medium. A positive electrode active material layer was formed by coating the positive electrode slurry on both surfaces of the positive electrode base material and drying. Thus, a positive electrode raw sheet was manufactured. The positive electrode raw sheet was compressed. The positive electrode plate was manufactured by cutting the positive electrode raw sheet into a strip shape after the compression.

[0155] Width of the positive electrode plateFigure 2 The dimension in the W-axis direction of the positive electrode active material layer was 105 mm. The width of the positive electrode active material layer was 90 mm. The positive electrode substrate was exposed by 15 mm at one end in the width direction of the positive electrode plate.

[0156] (Manufacture of negative electrode plate)

[0157] The following materials were prepared.

[0158] Negative electrode active material particles: spheroidized natural graphite

[0159] Binder: CMC, SBR

[0160] Dispersing medium: water

[0161] Negative electrode substrate: Cu alloy foil

[0162] D50 of the negative electrode active material particles was measured. D50 is shown in Table 1 below.

[0163] A negative electrode slurry was prepared by mixing the negative electrode active material particles, the binder, and the dispersing medium. A negative electrode active material layer was formed by coating the negative electrode slurry on both surfaces of the negative electrode substrate and drying. Thus, a negative electrode blank was manufactured. The negative electrode blank was compressed. A negative electrode plate was manufactured by cutting the negative electrode blank into a strip shape after compression.

[0164] Width of negative electrode plate Figure 2 The dimension in the W-axis direction of the negative electrode active material layer was 107 mm. The width of the negative electrode active material layer was 95 mm. The negative electrode substrate was exposed by 12 mm at one end in the width direction of the negative electrode plate.

[0165] In the negative electrode plate, the median value of the circularity of the negative electrode active material particles was measured by the aforementioned steps. The median value of the circularity is shown in Table 1 below.

[0166] (Preparation of spacer)

[0167] A spacer was prepared. The spacer was composed of a porous resin layer. The porous resin layer included a first layer (PP layer), a second layer (PE layer), and a third layer (PP layer). The second layer was interposed between the first layer and the third layer.

[0168] (Formation of electrode body)

[0169] A laminate was formed by sequentially stacking the spacer, the positive electrode plate, the spacer, and the negative electrode plate. A coiled body in a cylindrical shape was formed by winding the laminate around a winding core. The coiled body was shaped into a flat shape by flattening the coiled body in a direction orthogonal to the winding axis. Thus, an electrode body was formed.

[0170] Thickness of electrode body Figure 3The dimension of the D-axis direction (the dimension of the thickness of the negative electrode plate) was 10.56 mm. The positive electrode plate had a stack number of 66. The negative electrode plate had a stack number of 68. The separator had a stack number of 140.

[0171] The electrode body was composed of a flat portion and a curved portion. A part of the stack was cut out from the curved portion in the outermost layer of the electrode body. The thickness of the positive electrode plate, the negative electrode plate, and the separator was measured in the cut-out part of the stack, respectively. The thickness of each member was measured by a micrometer of a constant pressure type (manufactured by Mitutoyo Corporation).

[0172] The thickness of the negative electrode active material layer was calculated by subtracting the thickness of the negative electrode substrate from the thickness of the negative electrode plate. The thickness of the negative electrode active material layer is shown in Table 1 below. The ratio of the thickness of the negative electrode active material layer to the thickness of the stack was 0.43.

[0173] In the negative electrode plate, the puncture resistance was measured by the aforementioned procedure. The puncture resistance is shown in Table 1 below.

[0174] In the separator, the thickness retention rate and the puncture strength of the porous resin layer were measured by the aforementioned procedure. The thickness retention rate and the puncture strength are shown in Table 1 below.

[0175] The porous resin layer was separated into three layers. The thickness of each layer was measured by a micrometer. The thickness ratio of the second layer (PE layer) was calculated. The thickness ratio of the second layer is shown in Table 1 below.

[0176] Nos. 2 to 9

[0177] An electrode body including the negative electrode plate and the separator shown in Table 1 below was formed, respectively.

[0178] < Evaluation >

[0179] < Detection Sensitivity in the Withstand Voltage Test >

[0180] In the outermost layer of the electrode body, a simulated foreign matter was disposed on the surface of the negative electrode plate. The simulated foreign matter was a metal ball (diameter: 200 μm, SUS304). After the simulated foreign matter was disposed, a withstand voltage test of 200 V was performed. In a case where a leakage current of 50 mA or more flowed, it was judged that the detection sensitivity was good. The electrode body in which a leakage current of 50 mA or more flowed was disintegrated. In the electrode body in which a leakage current of 50 mA or more flowed, a short-circuit trace was confirmed at a position corresponding to the simulated foreign matter. In Table 1 below, when the evaluation result was “P”, it was considered that the detection sensitivity of the metal sheet was improved.

[0181] < Discharge Resistance >

[0182] An outer container made of an Al alloy was prepared. The outer container was square. The outer container had an outer dimension of "120 mm x 65 mm x 12.55 mm (width W x height H x depth D)". An electrode body was housed in the outer container. An electrolyte was injected into the outer container. After the injection of the electrolyte, the electrolyte was sufficiently impregnated in the electrode body. After the impregnation, a prescribed amount of charging was performed. Gas generated from the electrode body at the time of charging was discharged from the outer container. After the gas discharge, the outer container was sealed. Through the above steps, a battery was manufactured. Furthermore, the electrolyte was composed of the following components.

[0183] Solvent: "EC / EMC / DMC = 3 / 3 / 4 (volume ratio)"

[0184] Supporting electrolyte: LiPF6 (1 mol / L)

[0185] Additive: VC (0.3% by mass fraction)

[0186] The voltage of the battery was adjusted to 3.51 V by constant current-constant voltage (CC-CV) charging. The current at the time of constant current (CC) charging was 1 It. The total charging time was 1.5 hours. Furthermore, "1 It" was defined as a current that makes the rated capacity of the battery flow out in one hour.

[0187] The battery was discharged at a current of 75 It for 10 seconds. From the inclination of the current-voltage chart at the time of discharging, the discharge resistance was found. The discharge resistance is shown in Table 1 below. The discharge resistance in Table 1 below is a relative value when the discharge resistance of No. 1 is defined as 100. It can be considered that the lower the discharge resistance, the better the output.

[0188] Creep short-circuit resistance

[0189] An electrode body was prepared. In the flat portion of the outermost layer of the electrode body, a simulated foreign matter was arranged on the surface of the negative electrode plate. After the arrangement of the simulated foreign matter, a battery was manufactured without performing an electric pressure resistance test.

[0190] The voltage of the battery was adjusted to 2.5 V by CC-CV discharging. The current at the time of CC discharging was 9 It. The termination current was 0.25 It. After the end of discharging, the voltage of the battery was adjusted to 3.176 V by CC-CV charging. The current at the time of CC charging was 5 It. The termination current was 0.0625 It.

[0191] After charging, two plates and a restraining member were assembled to the battery. The battery was sandwiched between the two plates. The restraining member connected the two plates. By pressing the battery with the two plates, the depth (D) of the outer container was reduced to 12.55 mm. Figure 9The dimension in the D-axis direction (the dimension of the depth) was reduced to 12.30 mm. That is, the depth was reduced by 0.25 mm. After the assembly constraint member was assembled, the battery was left for four days. After the leaving, it was confirmed whether or not the voltage was significantly decreased. Further, the battery in which the voltage was not decreased was disassembled, and it was confirmed whether or not there was a short-circuit trace in the position corresponding to the simulated foreign matter.

[0192]

[0193] <Results>

[0194] In the above Table 1, by making the puncture resistance of the negative electrode active material layer 0.60 N / mm or more, it can be seen that there is a tendency that the detection sensitivity in the voltage resistance test is improved (see, for example, Nos. 4, 9).

[0195] In the above Table 1, by making the thickness retention rate of the porous resin layer 91.8% or more, it can be seen that there is a tendency that the creep short-circuit resistance is improved (see, for example, Nos. 5, 7).

[0196] In the above Table 1, by making the thickness retention rate of the porous resin layer 93.0% or less, it can be seen that there is a tendency that the output is improved (see, for example, Nos. 6, 8).

[0197] The present embodiment and the present example are illustrative in all respects. The present embodiment and the present example are not restrictive. The scope of the present technology includes all modifications within the meaning and range equivalent to the recitations of the claims. For example, it is also intended to include the following aspects from the beginning: extracting any structures from the present embodiment and the present example, and arbitrarily combining them.

Claims

1. A nonaqueous electrolyte secondary battery characterized by comprising: the nonaqueous electrolyte secondary battery comprises an electrode body and an electrolyte solution, the electrode body comprises a laminate, the laminate comprises a positive electrode sheet, a negative electrode sheet, and a separator, the separator separates the positive electrode sheet from the negative electrode sheet, the separator comprises a porous resin layer, the porous resin layer comprises a polyolefin-based material, the negative electrode sheet comprises a negative electrode active material layer, the negative electrode active material layer comprises negative electrode active material particles, the negative electrode active material layer is in direct contact with the porous resin layer, the negative electrode active material layer has a puncture resistance of 0.60 N / mm or more, the puncture resistance is obtained by formula (α): Z = Y / X... (α), in the formula (α), Z represents the puncture resistance, Y represents a maximum stress in a puncture test, X represents a displacement at a point of time at which the maximum stress is obtained, the displacement corresponds to a moving distance of a needle used in the puncture test from being in contact with a surface of the negative electrode active material layer to being vertically through the negative electrode active material layer with respect to the surface of the negative electrode active material layer, in the puncture test, the needle having a tip radius of 10 μm is vertically punctured at a speed of 10 μm / s with respect to the surface of the negative electrode active material layer, the porous resin layer has a thickness retention rate of 91.8% to 93.0%, the thickness retention rate is obtained by formula (β): Tr = (T1 / T0) x 100... (β), in the formula (β), Tr represents the thickness retention rate, T0 represents a thickness of the porous resin layer, T1 represents a thickness of the porous resin layer in a state after the porous resin layer is compressed in a thickness direction with a pressure of 13.9 MPa and the pressure is removed.

2. The nonaqueous electrolyte secondary battery according to claim 1, characterized in that, the negative electrode active material particles have a median value of circularity of 0.60 or more.

3. The nonaqueous electrolyte secondary battery according to claim 1 or 2, characterized in that, the porous resin layer comprises a first layer, a second layer, and a third layer, the first layer, the second layer, and the third layer are laminated in a thickness direction of the porous resin layer, the second layer is interposed between the first layer and the third layer, the first layer and the third layer each comprise polypropylene, the second layer comprises polyethylene, the porous resin layer satisfies a relationship of formula (γ): t2 / {(t1+t3) x 0.5} ≤ 1.5... (γ), in the formula (γ), t1 represents a thickness of the first layer, t2 represents a thickness of the second layer, t3 represents a thickness of the third layer.

4. The nonaqueous electrolyte secondary battery according to claim 1 or 2, characterized in that, a ratio of a thickness of the negative electrode active material layer with respect to a thickness of the laminate is 0.35 to 0.

45.

5. The nonaqueous electrolyte secondary battery according to claim 1 or 2, characterized in that, in the electrode body, the positive electrode sheet has a lamination number of 60 to 80.

6. The nonaqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the porous resin layer has a thickness of 14 μm to 20 μm.

7. The nonaqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the porous resin layer has a puncture strength of 3.92 N or less.

8. The nonaqueous electrolyte secondary battery according to claim 1, characterized in that the negative electrode active material layer has the puncture resistance of 0.85 N / mm or less.

9. The nonaqueous electrolyte secondary battery according to claim 2, characterized in that the negative electrode active material particle has the median of the circularity of 0.85 or less.

10. A battery module, characterized in that the battery module includes a plurality of unit cells, the plurality of unit cells are arranged in an arrangement direction, the arrangement direction is along a stacking direction of the positive electrode plate, the negative electrode plate, and the separator in the electrode body, the plurality of unit cells are respectively subjected to a compression force along the arrangement direction, the plurality of unit cells are each the nonaqueous electrolyte secondary battery according to any one of claims 1 to 9.

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