JP2013218913A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrode secondary battery which, by more suitably disposing a heat resistant layer fitted separator according to a battery structure, exhibits increased thermal stability, safety and reliability of its electrode body when overcharged or in similar cases.SOLUTION: A nonaqueous electrode secondary battery 10 comprises: a cathode 30 including a cathode active material layer 34 on both sides of a cathode collector 32; an anode 50 including an anode active material layer 54 on both sides of an anode collector 52; a single-sided HRL separator 70A provided with an inorganic filler containing heat resistant layer 74 on one side of a base material 72; a double-sided HRL separator 70B provided with a heat resistant layer 74 on both sides of the base material 72; and an electrolyte. The nonaqueous electrode secondary battery 10 includes an electrode body 20 consisting of the cathode 30 and the anode 50 which are laminated one on top of another via the single-sided HRL separator 70A or the double-sided HRL separator 70B in such a way that the surface of the cathode active material layer 34 has the heat resistant layer 74 abutting on both sides thereof and that the surface of the anode active material layer 54 has the heat resistant layer 74 abutting on only one side thereof.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery including an electrode body in which a positive electrode, a negative electrode, and a separator having a heat-resistant layer are laminated.

In recent years, chargeable / dischargeable non-aqueous electrolyte secondary batteries such as nickel metal hydride batteries and lithium secondary batteries have become increasingly important as power sources for vehicles or personal computers and portable terminals. In particular, a lithium secondary battery that is lightweight and obtains a high energy density is preferably used as a high-output power source mounted on a vehicle.
This type of secondary battery is typically constructed by housing an electrode body in which a positive electrode and a negative electrode are stacked via a separator together with an electrolyte in a case. As an electrode structure of such an electrode body, a laminated electrode body in which a plurality of planar electrode bodies are laminated, or a wound electrode body in which a long sheet-like electrode body is wound in a spiral shape It is possible to increase the reaction area between the positive and negative electrodes and increase the energy density and output.

  Here, the separator is typically a microporous membrane made of resin, and has a role of electrically insulating the positive electrode and the negative electrode and a role of holding the non-aqueous electrolyte. In addition to these roles, for the purpose of ensuring the safety of the battery and the device in which the battery is mounted, the separator is heated to a certain temperature range (typically the softening point of the resin or the resin). It also has the function of softening when it reaches the melting point and shutting down the conduction path of the charge carrier.

  In view of this, it has been proposed to provide such a separator with a heat-resistant layer containing a heat-resistant inorganic filler and a binder on one surface or both surfaces of a conventional resin substrate (for example, Patent Document 1). And 2). The heat-resistant layer containing the inorganic filler also has resistance to an oxidation or reduction atmosphere, and the separator can be prevented from being deteriorated due to the oxidation atmosphere of the positive electrode by providing the heat-resistant layer of the separator on the surface facing the positive electrode. .

  In recent years, large secondary batteries (such as lithium secondary batteries for hybrid vehicles) used as power sources for vehicles have been increasing in output, for example due to unavoidable contamination of metallic foreign matters. When a short circuit occurs inside the battery, it is assumed that the battery temperature rapidly increases. In this case, the temperature in the vicinity of the short-circuit point on the negative electrode surface is even higher, and can reach, for example, several hundred degrees C. (for example, 300 degrees C. or more). Therefore, in such a large-sized secondary battery, it has been studied to prevent melting of the separator due to an internal short circuit by providing a heat-resistant layer of the separator on the surface facing the negative electrode.

JP2011-253684A JP 2008-300362 A

By the way, the separator provided with the heat-resistant layer on both sides increases the thickness of the separator itself, so that the volume ratio of the positive and negative electrodes and the reaction area occupying a predetermined volume are reduced, which directly affects the battery capacity reduction. obtain. From the viewpoint of avoiding such influence, for example, as shown in FIG. 8, it is considered preferable to use a separator 70 having a heat-resistant layer 74 only on one surface of the base material 72 according to a desired purpose. . FIG. 8 shows an example in which the heat-resistant layer 74 is disposed to face the negative electrode 50. However, the separator is usually formed with a size larger than that of the electrode active material layer for reliable insulation. Therefore, when the separator 70 provided with the heat-resistant layer 74 only on one side is used, the surface of the separator 70 on the side not provided with the heat-resistant layer 74 (that is, the base material 72) is softened and the opposing base materials 72 adhere to each other. easy.
When such adhesion occurs, when the battery becomes high temperature due to overcharge or the like and the separator 70 contracts, the end portions (typically corners) of the base material 72 of the separator 70 and the active material layers 34 and 54 of the positive electrode 30 or the negative electrode 50 are formed. Part), the separator 70 may be damaged at the ends of the active material layers 34 and 54. Such a breakage of the separator can cause an internal short circuit, and is not preferable because it can increase the leakage current after the battery is shut down.

  The present invention has been created to solve the above-described conventional problems, and the object of the present invention is to overcharge by arranging a separator having a heat-resistant layer more appropriately according to the battery structure. An object of the present invention is to provide a non-aqueous electrolyte secondary battery in which the thermal stability of the electrode body, the safety and the reliability are improved.

  That is, the non-aqueous electrolyte secondary battery disclosed herein (hereinafter sometimes simply referred to as a secondary battery, a battery, etc.) includes a positive electrode having a positive electrode active material layer on both sides of a positive electrode current collector. A negative electrode having a negative electrode active material layer on both sides of a negative electrode current collector, a separator A having a heat resistant layer containing an inorganic filler on one side of the substrate, a separator B having the heat resistant layer on both sides of the substrate, an electrolyte, And an electrode body in which the positive electrode and the negative electrode are laminated with the separator A or B interposed therebetween. The surface of the positive electrode active material layer is laminated so that the heat-resistant layer is in contact with both surfaces, and the surface of the negative electrode active material layer is in contact with the heat-resistant layer only on one of the surfaces. , Separators A and B are provided.

  In the secondary battery disclosed here, in order to achieve the configuration as described above, either one of separators A and B is used in the electrode body, but both are used. In other words, the separators A and B are alternately arranged between the positive electrode and the negative electrode in a typical configuration (see, for example, FIG. 4). Here, about the separator B provided with a heat-resistant layer on both surfaces of a base material, it can be arrange | positioned between a positive electrode and a negative electrode, without having to distinguish the back and front. About separator A provided with a heat-resistant layer only on one side of one substrate, it is arranged so that the surface provided with a heat-resistant layer contacts the positive electrode active material layer, and the substrate surface contacts the negative electrode active material layer. According to such a configuration, since the separator A that can be made relatively thin is used in combination with the configuration using only the separator B that has a greater thickness by providing heat-resistant layers on both sides of the base material, it occupies the electrode body. The volume ratio of the separator can be reduced. Thereby, a non-aqueous electrolyte secondary battery with higher energy density is provided. Moreover, since the separators A and B are disposed with the heat-resistant layer facing the positive electrode active material layer, the deterioration of the separator due to the oxidizing atmosphere of the positive electrode is suitably suppressed. Since both the separators A and B are provided with a heat-resistant layer, insulation can be ensured even when shut down due to overcharge or the like, and the occurrence of leakage current can be suppressed. Furthermore, it is possible to suitably prevent the occurrence of an internal short circuit due to the mixing of metal foreign matter.

  In addition, in the part (end part) where the separators A and B protrude from the electrode active material layer, the base materials of the separator do not face each other. Therefore, even if the battery becomes high temperature, the substrates do not stick to each other. Moreover, the base material of the separator and the heat-resistant layer do not adhere. This prevents the end of the separator protruding from the electrode active material layer from being restrained, and suppresses the generation of local stress between the separator and the electrode active material layer even when the separators A and B are thermally contracted. Thus, problems such as an internal short circuit being induced and a leakage current after shutdown is reduced.

  Conventionally, in each of the positive electrode and the negative electrode in which the electrode active material layer is formed on both surfaces of the current collector, the active material layer formed on one surface of the current collector and the active material formed on the other surface It was considered important to keep (align) the material layer with the same state. For this reason, when the heat-resistant layer of the separator is also opposed to the active material layer on one side of the electrode, it has been common technical knowledge among those skilled in the art to face the active material layer on the other side. On the other hand, the present inventors can make the state of the active material layer formed on both sides of the current collector somewhat different if the state of the whole electrode body, and thus the whole battery, is better. It was found that the effect could be compensated. Based on this knowledge, the invention disclosed herein creates an asymmetric structure for the negative electrode between the state where the heat-resistant layer is opposed to the negative electrode active material layer and the state where it is not opposed to the negative electrode active material layer on both sides of the current collector. It is intended to improve the condition of the whole body. The secondary battery disclosed here has the above-mentioned excellent effects with the idea of breaking the conventional definition concept without requiring new materials or complicated manufacturing processes compared with the conventional battery. It is.

In a preferred aspect of the nonaqueous electrolyte secondary battery disclosed herein, the electrode body is wound to form a wound electrode body. That is, in the electrode body, a positive electrode, a negative electrode, and separators A and B, which are typically formed in a long shape, are laminated and wound as described above. By forming a wound electrode body, a curved portion is formed in the electrode body structure. In such a curved portion, the winding length is longer on the wound outer peripheral side than on the wound inner peripheral side. Therefore, in the curved portion, for example, different stresses are generated in the winding circumferential direction between the active material layer on the winding outer periphery side and the active material layer on the winding inner periphery side of the current collector. That is, a tensile stress is generated in the circumferential direction on the active material layer on the wound outer peripheral side, whereas a compressive stress is generated in the circumferential direction on the active material layer on the wound inner peripheral side. For this reason, especially when the battery becomes high temperature and thermal contraction occurs in the separator, the stress generated between the active material layer on the winding outer periphery side and the separator can further increase. Here, if the base materials of the separator are adhered and fixed, these stresses are concentrated locally, and the possibility of breakage of the separator is increased.
On the other hand, according to the structure disclosed here, since separator B is provided with a heat-resistant layer on both sides, there is no concern about adhesion. Moreover, although the base material is exposed to the single side | surface of the separator A, the separator A is arrange | positioned in the electrode body so that base materials may not oppose. Therefore, both the separators A and B are less likely to break, and problems such as an internal short circuit and an increase in leakage current after shutdown are suppressed. That is, by applying the configuration disclosed herein to a secondary battery including a wound electrode body, the effect can be obtained more clearly.

  In a preferred aspect of the nonaqueous electrolyte secondary battery disclosed herein, the wound electrode body has a flat shape crushed in a direction substantially perpendicular to the winding axis. As described above, when the electrode body is a wound electrode body, a curved portion is formed in the electrode structure. In the case of a flat wound electrode body, the curvature of the curved portion can be substantially maximized at the extreme end in the longitudinal direction of the wound cross section. Therefore, for example, the possibility of problems such as breakage of the separator and increase in leakage current after shutdown can be increased as compared with a cylindrical wound electrode body that is not flat. However, according to the structure disclosed here, the problem of adhesion between the separator base materials is solved. Accordingly, problems such as a breakage of the separator and an increase in leakage current after shutdown are suppressed, so that such an effect can be obtained more clearly.

  In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the separator A is disposed on the outer peripheral side of the negative electrode, and the separator B is disposed on the inner peripheral side, and the outer periphery of the negative electrode current collector is disposed. The base material of the separator A is in contact with the surface of the negative electrode active material layer provided on the side, and the surface of the negative electrode active material layer provided on the inner peripheral side with respect to the negative electrode current collector The heat-resistant layer of the separator B is in contact with the separator B. The electrode body generally has a wider negative electrode width than the positive electrode in order to prevent charge carriers oxidized in the positive electrode (lithium ions in the case of a lithium secondary battery) from depositing on the negative electrode surface. The (capacity) is configured to be high (for example, see FIG. 4).

  According to the detailed study by the inventors of this application, it has been found that the following phenomenon is observed in the curved portion of the wound electrode body. That is, as described above, in such a curved portion, the winding length on the winding outer peripheral side is longer than that on the winding inner peripheral side, so that the charge carriers between the positive electrode active material layer and the negative electrode active material layer facing each other are wound. There was a tendency that the balance of acceptability was lost, and charge carriers were likely to be deposited on the surface of the negative electrode active material layer located on the outer periphery of the negative electrode current collector. In such a state, when the heat-resistant layer of the separator is disposed so as to face the negative electrode active material layer located on the wound outer peripheral side (that is, the heat-resistant layer is disposed on the wound inner peripheral side of the separator), Precipitation of charge carriers has progressed into the heat-resistant layer, and a situation has occurred in which the negative electrode active material layer and the heat-resistant layer are firmly fixed. Therefore, when heat shrinkage occurs in the separator, there is a problem that the separator is more easily broken.

  On the other hand, according to the structure disclosed here, since the base material of the separator A is brought into contact with the surface of the negative electrode active material layer provided on the outer peripheral side with respect to the negative electrode current collector, the negative electrode active material layer And the separator A are not fixed. Therefore, since the breakage of the separator is suppressed, it is possible to further reduce the cause of the short circuit and further reduce the leakage current after the battery is shut down.

  In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the base material of the separator A includes at least a polyethylene layer made of polyethylene and a heat resistant resin layer made of a resin having higher heat resistance than the polyethylene. The heat-resistant resin layer has a laminated structure, and the heat-resistant resin layer forms a surface on the opposite side of the surface of the base material from the surface provided with the heat-resistant layer. Since the separator A has a heat-resistant layer only on one side, the base material is exposed on the side where the heat-resistant layer is not provided. Therefore, such a base material has two functions which are contradictory to heat resistance, which is softened and melted at an appropriate temperature and has a shutdown function to cut off the current, and is soft and difficult to melt even when the opposing negative electrode active material layer becomes high temperature. It is desirable to have characteristics. According to the configuration disclosed herein, the base material has at least two layers of a polyethylene layer and a heat resistant resin layer, and the heat resistant resin layer is exposed on the surface. And the polyethylene layer which is an intermediate | middle layer of a heat resistant layer and a heat resistant resin layer can be equipped with a shutdown function. These resin layers can be formed relatively thin as compared to a heat-resistant layer containing an inorganic filler. Therefore, a separator provided with such a substrate can be provided with heat resistance and durability that is difficult to melt even when the negative electrode generates heat, and with a shutdown function at a predetermined temperature, while keeping its thickness thinner. .

  In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the heat resistant resin layer is any one selected from the group consisting of wholly aromatic polyamide, polyimide, polyamideimide, polysulfone, and polyethersulfone, Or it is a preferable form that it is 2 or more types. Since these polymers have a high melting point or thermal decomposition temperature and are excellent in moldability, they are suitable for use as a heat resistant resin layer of a separator. Thereby, a nonaqueous electrolyte secondary battery having more excellent heat resistance and durability is provided.

In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, initial charging of the positive electrode active material layer in one positive electrode active material layer and one negative electrode active material layer opposed via the separator A or B is performed. counter capacity ratio defined by the ratio of the initial charge capacity of the negative electrode active material layer to the capacitance _{(C P) (C N)} (C N / C P) is, as a feature that it is 1.5 to 1.9 Yes. As described above, the ratio of the capacity of the positive electrode active material layer and the negative electrode active material layer facing each other via the separator directly affects the battery capacity (or irreversible capacity) and the energy density of the battery. Depending on the use conditions of the battery such as charging, the charge carriers are likely to be deposited. This can also increase battery resistance. Therefore, in the invention disclosed herein, by setting the facing capacity ratio in the range of 1.5 to 1.9, various battery uses can be performed while maintaining battery characteristics such as battery capacity and energy density. In this situation, the deposition of charge carriers is suppressed.

  As described above, the non-aqueous electrolyte secondary battery disclosed herein includes a separator A having a heat-resistant layer only on one side and a separator B having a heat-resistant layer on both sides as a separator having a heat-resistant layer. It is arranged so that the battery characteristics of the body can be improved. Therefore, for example, even when the battery becomes high temperature, the problem due to the adhesion of the separator base material is solved, and the battery is excellent in thermal stability, and can be a battery with higher safety and reliability. Such an effect can be exhibited particularly when applied to a large battery requiring high capacity and high output characteristics. For example, specifically, (1) energy density is 500 wh / L or more, (2) capacity is 2.4 Ah or more, or (3) output density is any one or more characteristics of 1.5 kwh / L or more. Can be preferably applied to a battery provided with the above, preferably a battery provided with all the characteristics of (1) to (3). Therefore, the nonaqueous electrolyte secondary battery disclosed herein can be suitably used as a driving power source mounted on a vehicle such as an automobile that requires particularly high safety and reliability. In the present invention, for example, as shown in FIG. 6, a vehicle 1 such as an automobile provided with such a nonaqueous electrolyte secondary battery 10 (which may be in the form of an assembled battery 100) as a power source of a vehicle driving motor (electric motor). Can also be provided. Although the kind of vehicle 1 is not specifically limited, Typically, it can be set as a hybrid vehicle, an electric vehicle, a fuel cell vehicle, etc.

It is the perspective view which showed typically the external appearance of the nonaqueous electrolyte secondary battery which concerns on one Embodiment. It is a longitudinal cross-sectional view which follows the II-II line in FIG. It is a figure explaining the structure of a wound electrode body. It is sectional drawing which illustrates typically the laminated structure in the edge part of an electrode body. It is sectional drawing which illustrates typically the laminated structure in the curved part of a wound electrode body. It is the side view which illustrated the vehicle provided with the secondary battery concerning one embodiment. It is a conceptual diagram explaining the battery behavior at the time of shutdown. It is sectional drawing which illustrates typically the laminated structure in the edge part of the conventional electrode body.

  In the present specification, the “secondary battery” generally refers to a battery that can be repeatedly charged and discharged by movement of charge carriers, and typically includes a nickel metal hydride battery, a lithium secondary battery, a lithium polymer battery, and the like. In the present specification, the “active material” refers to reversibly occlusion and release (typically insertion and desorption) of a chemical species (for example, lithium ion in a lithium secondary battery) that serves as a charge carrier in the secondary battery. A possible substance.

Hereinafter, the nonaqueous electrolyte secondary battery disclosed herein will be described with reference to the drawings as appropriate. Note that matters other than matters specifically mentioned in the present specification and necessary for implementation can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
In the following description, for the sake of clarity in description, the separator A is described as a single-sided HRL separator, and the separator B is described as a double-sided HRL separator. In particular, when it is not necessary to distinguish between the separator A and the separator B, simply “ Sometimes referred to as a “separator”. In addition, this HRL is an abbreviation for Heat Resistant Layer (heat-resistant layer).

The nonaqueous electrolyte secondary battery disclosed herein essentially includes a positive electrode, a negative electrode, at least two separators, and an electrolyte. 2 to 4, for example, the secondary battery includes an electrode body 20 in which a positive electrode 30 and a negative electrode 50 are stacked on each other via a single-sided HRL separator 70A or a double-sided HRL separator 70B.
The positive electrode 30 includes a positive electrode active material layer 34 on both surfaces of a positive electrode current collector 32. The negative electrode 50 includes negative electrode active material layers 54 on both sides of a negative electrode current collector 52. The single-sided HRL separator 70 </ b> A includes a heat-resistant layer 74 containing an inorganic filler on one side (one side) of the surface of the base material 72. The double-sided HRL separator 70 </ b> B includes a heat-resistant layer 74 containing an inorganic filler on both sides of the base material 72. These single-sided HRL separators 70 </ b> A and double-sided HRL separators 70 </ b> B can typically be alternately arranged between the positive electrode 30 and the negative electrode 50.

  For example, as shown in FIGS. 3 and 4, the positive electrode 30 is typically a portion where the positive electrode current collector 32 is exposed without forming the positive electrode active material layer 34 at one end in the width direction. (Uncoated part 33) is provided. Also in the negative electrode 50, a portion where the negative electrode current collector 52 is exposed without being formed with the negative electrode active material layer 54 (uncoated portion 53) is provided at one end in the width direction. In consideration of the facing capacity ratio described later, the negative electrode active material layer 54 is often formed wider than the positive electrode active material layer 34. In such a case, the negative electrode active material layer 54 is disposed so as to cover the positive electrode active material layer 34 in the width direction. At the same time, the positive electrode 30 and the negative electrode 50 are arranged so that the uncoated portion 33 of the positive electrode 30 and the uncoated portion 53 of the negative electrode 50 are separately projected at one end and the other end in the width direction. Slightly staggered. Further, both separators 70A and 70B are formed wider than these widths in order to reliably insulate the positive electrode active material layer 34 and the negative electrode active material layer 54. Therefore, both separators 70A and 70B are disposed so as to cover the positive electrode active material layer 34 and the negative electrode active material layer 54 in the width direction.

Here, the arrangement of the separators 70A and 70B will be described in more detail. Since the double-sided HRL separator 70B is provided with the heat-resistant layers 74 on both sides, for example, it can be disposed between the positive electrode 30 and the negative electrode 50 without distinguishing the “front” and “back” of the surface. One single-sided HRL separator 70A includes a heat-resistant layer 74 only on one side. The heat-resistant layer 74 is in contact with the positive electrode active material layer 34, and the base material 72 is disposed in contact with the negative electrode active material layer 54.
In other words, the positive electrode 30 is sandwiched between the heat resistant layers 74, and the surfaces of the positive electrode active material layers 34 provided on both surfaces of the positive electrode current collector 32 are in contact with both surfaces. The negative electrode 50 is sandwiched between the heat-resistant layer 74 and the base material 72, and the heat-resistant layer 74 is in contact with one surface of the negative electrode active material layers 54 provided on both surfaces of the negative electrode current collector 52. A substrate 72 is in contact with one surface.

In such a configuration, since the single-sided HRL separator 70A includes the heat-resistant layer 74 only on one side, the thickness can be made relatively thin. Therefore, the ratio of the separators 70A and 70B occupying the electrode body 20 can be kept low, and the energy density of the entire battery can be maintained high.
Moreover, since the heat resistant layer 74 contains an inorganic filler, it is excellent in heat resistance and oxidation resistance. In such a configuration, the separators 70A and 70B are provided with the heat-resistant layer 74 facing the positive electrode 30, so that deterioration of the separators 70A and 70B due to the oxidizing atmosphere of the positive electrode 30 is suitably suppressed, and durability is improved.
Each of the single-sided HRL separator 70A and the double-sided HRL separator 70B includes at least one heat-resistant layer 74. For this reason, for example, even if charge carriers are deposited on the surface of the negative electrode active material layer due to the mixing of metal foreign matter, the growth can be stopped by the heat-resistant layer 74 and an internal short circuit can be prevented. Further, even when the battery becomes hot due to overcharging or the like and the base material 72 of the separators 70A and 70B is melted, the insulation between the positive electrode 30 and the negative electrode 50 can be secured by the heat-resistant layer 74, and leakage current is generated. Etc. can be suppressed.

  Further, the surface of the base material 72 of the single-sided HRL separator 70A is opposed to the heat-resistant layer 74 of the double-sided HRL separator 70B at a portion protruding from the negative electrode active material layer 54. That is, the base materials 72 do not face each other. Further, the base material 72 and the heat-resistant layer 74 do not adhere to each other even at a high temperature. Therefore, even when the temperature of the battery is increased due to overcharging or the like and the base material 72 of the separators 70A and 70B is softened, the separators 70A and 70B are prevented from sticking to each other. Moreover, when separator 70A, 70B adheres, the situation where a local stress generate | occur | produces between the electrode active material layers 34 and 54 and separator 70A, 70B is damaged can be avoided. Therefore, the secondary battery with high thermal stability in which the cause of the internal short circuit is reduced and the occurrence of leakage current after the battery shutdown is suppressed is provided.

The electrode body 20 can take various aspects into consideration. For example, the electrode body 20 may be the electrode body 20 in which only one stacked unit of the positive electrode 30—the single-sided HRL separator 70A—the negative electrode 50—the double-sided HRL separator 70B as illustrated in FIG. The electrode body 20 may have a multilayer structure in which the laminated unit is repeated twice or more.
In addition, the electrode body 20 having this multilayer structure may be, for example, a stacked electrode body 20 in a form in which a plurality of electrode bodies 20 composed of the above-described planar stack units are stacked. In such a case, the case where the single-sided HRL separator 70A and the double-sided HRL separator 70B are alternately arranged between the positive electrode 30 and the negative electrode 50 can be considered. For example, the double-sided HRL separator 70B, the single-sided HRL separator 70A, the single-sided HRL separator 70A, and the double-sided HRL separator 70B can be arranged between the positive electrode 30 and the negative electrode 50. Alternatively, for example, as shown in FIG. 3, a wound electrode body 20 in a form in which the long sheet-like electrode body 20 composed of the one laminated unit is wound in a spiral shape may be used. In addition, when the wound electrode body 20 is constructed, there is an effect specific to such a form that is not seen in the stacked electrode body 20 with respect to battery characteristics.

For example, as shown in FIG. 5, one of the effects is that the wound electrode body 20 has a curved portion on the electrode surface, so that the wound outer peripheral side is more wound than the wound inner peripheral side. This means that the turn length becomes longer. That is, the winding length (volume) is longer (larger) on the winding outer peripheral side than on the winding inner peripheral side. For this reason, in the curved portion, the electrode active material layers 34 and 54 positioned on the outer circumferential side of the winding can have higher (larger) charge carrier receiving characteristics (capacity) than in the flat portion. Therefore, as shown in FIGS. 3 and 5, the wound electrode body 20 has the negative electrode 50 that needs to have higher charge carrier acceptability disposed below (so as to be positioned on the outer peripheral side), In general, the positive electrode 30 disposed on the upper side (so as to be located on the inner peripheral side) is wound with the positive electrode 30 inside.
In the curved portion of the wound electrode body 20, when the battery becomes hot and thermal contraction occurs in the base material 72 of the separators 70A and 70B, the separators 70A and 70B contract toward the inner circumferential side of the winding surface. Therefore, stress toward the inside of the winding in the winding radius direction can act between the separators 70A and 70B and the end portions of the active material layers 34 and 54 located on the winding inner peripheral side. Therefore, for example, when the separators 70A and 70B are adhered and restrained, a portion where stress applied to the separators 70A and 70B is further concentrated is generated, and the possibility of the breakage of the separators 70A and 70B is further increased.
On the other hand, according to the structure disclosed here, the problem of adhesion between the base materials 72 of the separators 70A and 70B is solved. Therefore, the possibility of increase in leakage current after breakage of separators 70A and 70B and shutdown is suppressed.

  In addition, as shown in FIG. 3, the wound electrode body 20 may have a flat shape crushed in a direction substantially perpendicular to the winding axis, depending on the shape of the battery case. In such a configuration, the curvature of the curved portion of the electrode body 20 is not substantially constant, and the central portion in the short direction in the wound cross section of the wound electrode body 20 (that is, the portion corresponding to the major axis in the wound cross section). ) Can have a maximum curvature. Therefore, if the separators 70A and 70B are adhered and restrained at the center portion in the short direction, for example, the separators 70A and 70B may be broken more than the cylindrical wound electrode body 20 which is not flat. Can be further increased. However, according to the configuration disclosed herein, the problem of adhesion between the base materials 72 of the separators 70A and 70B is solved. Therefore, even when the flat wound electrode body is provided, the separators 70A and 70B are not easily broken, and problems such as an internal short circuit and an increase in leakage current after shutdown are suppressed, and this effect can be obtained more suitably. Can do.

  Further, it has been clarified that the following phenomenon is observed in the curved portion of the wound electrode body 20. That is, as described above, in such a curved portion, the wound length (volume) is longer (larger) on the wound outer peripheral side than on the wound inner peripheral side. Therefore, in the curved portion, the area of the positive electrode active material layer 34 on the inner circumferential side facing the negative electrode active material layer 54 located on the outer circumference side of the negative electrode current collector 52 of the negative electrode 50 is larger than that of the negative electrode active material layer 54. In the surface of the negative electrode active material layer 54 located on the outer periphery side of the winding, the amount of charge carriers deposited (in the case of a lithium secondary battery) tended to increase. In some cases (particularly, in the flat wound electrode body 20), the positive electrode 30, the single-sided HRL separator 70A, the negative electrode 50, and the double-sided HRL separator 70B in a portion corresponding to the long diameter in the flat cross section of the wound electrode body 20. There may be a gap between them. Since such a gap leads to an increase in internal resistance and locally creates an overvoltage state, charge carriers are more likely to be deposited in such a region.

  Further, as shown in FIG. 5, the active material layers 34 and 54 on the outer side of the current collectors 32 and 52 and the active material layers 34 and 54 on the inner side of the current collector originally have a direction of stress received in the circumferential direction. Different. Specifically, the active material layers 34 and 54 outside the winding are subjected to tensile stress in the winding circumferential direction, whereas the active material layers 34 and 54 inside the winding are subjected to compressive stress in the winding circumferential direction. In such a situation of the wound electrode body 20, when the heat resistant layer 74 is disposed opposite to the negative electrode active material layer 54 provided on the wound outer peripheral side with respect to the negative electrode current collector 52, In addition, the deposition of charge carriers grows, and the negative electrode active material layer 54 and the heat-resistant layer 74 are firmly fixed. As a result, for example, when the temperature of the battery increases due to overcharge or the like, the base material 72 of the separators 70A and 70B tends to shrink, whereas the negative electrode active material layer 54 and the heat-resistant layer 74 located on the winding outer periphery side A tensile stress is generated in the circumferential direction, and the separators 70A and 70B are more likely to break. As a result, the possibility of problems such as an increase in leakage current after shutdown is further increased.

  On the other hand, according to the configuration disclosed herein, the single-sided HRL separator 70A is arranged on the outer peripheral side of the negative electrode 50, and the double-sided HRL separator 70B is arranged on the inner peripheral side of the negative electrode 50. The base 72 of the single-sided HRL separator 70A is in contact with the surface of the negative electrode active material layer 54 provided on the outer peripheral side with respect to the negative electrode current collector 52, and on the inner peripheral side with respect to the negative electrode current collector 52. A preferred embodiment is a structure in which the heat-resistant layer 74 of the double-sided HRL separator 70B is in contact with the surface of the negative electrode active material layer 54 provided. That is, the heat-resistant layer 74 is not disposed on or in contact with the outer peripheral surface of the negative electrode active material layer 54. Therefore, even if charge carriers (lithium) are deposited on the surface of the negative electrode active material layer 54 positioned on the outer periphery side of the winding, both are not fixed. As a result, the possibility of breakage of the separators 70A and 70B due to the adhesion of the negative electrode active material layer 54 and the heat-resistant layer 74 located on the outer periphery of the winding is reduced, and the cause of the short circuit is further reduced and the battery is shut down. Later leakage current can be reduced.

  Hereinafter, with reference to FIGS. 1 to 4 as appropriate, the overall configuration of the non-aqueous electrolyte secondary battery disclosed herein will be described in more detail using a lithium secondary battery 10 as a preferred embodiment as an example. explain. In this lithium ion battery 10, a single-sided HRL separator 70 </ b> A provided with a heat-resistant layer 74 containing an inorganic filler on one side and a double-sided HRL separator 70 </ b> B provided on both sides are used as separators. Then, the surface of the base 72 of the single-sided HRL separator 70A is in contact with only one of the surfaces of the negative electrode active material layer 54.

As described above, the positive electrode 30 includes the positive electrode active material layer 34 on the positive electrode current collector 32.
As the positive electrode current collector 32, a metal or an alloy suitable for the positive electrode 30 of the lithium secondary battery can be suitably used. For example, a rod-like body, a plate-like body, a foil-like body, a net-like body or the like mainly composed of aluminum, nickel, titanium, stainless steel, or the like can be used. In this embodiment, a strip-shaped aluminum foil having a predetermined width and a thickness of approximately 1 μm is used for the positive electrode current collector 32. The positive electrode current collector 32 is provided with an uncoated portion 33 along an edge on one side in the width direction. The positive electrode active material layer 34 is formed on both surfaces of the positive electrode current collector 32 except for an uncoated portion 33 set on the positive electrode current collector 32.

  The positive electrode active material layer 34 includes at least a positive electrode active material. In this embodiment, the positive electrode active material layer 34 is mainly composed of a granular positive electrode active material, and includes a conductive material for enhancing conductivity, and these are fixed onto the positive electrode current collector 32 by a binder. Yes. The positive electrode active material layer 34 is typically formed by supplying a composition for forming a positive electrode active material layer including the positive electrode active material, the conductive material, and the binder onto the positive electrode current collector 32. In the positive electrode active material layer 34 thus formed, voids are formed between the positive electrode active material particles so that the electrolyte solution can penetrate.

As the positive electrode active material, various materials that can be used as the positive electrode active material of the lithium secondary battery 10 can be used. Specifically, as the positive electrode active material, a material capable of occluding and releasing lithium can be used, and one or more of various materials conventionally used in lithium secondary batteries should be specifically limited. It can be used without. As such a positive electrode active material, a lithium transition metal oxide (typically in particulate form) is preferably used, and an oxide having a layered structure or an oxide having a spinel structure can be appropriately selected and used. For example, selected from a lithium nickel oxide (typically LiNiO ₂ ), a lithium cobalt oxide (typically LiCoO ₂ ), and a lithium manganese oxide (typically LiMn ₂ O ₄ ). The use of one or more lithium transition metal oxides is preferred.

  Here, for example, “lithium nickel-based oxide” refers to an oxide having Li and Ni as constituent metal elements, and one or more metal elements other than Li and Ni (that is, Li and Ni). The ratio of transition metal elements other than Ni and / or typical metal elements) is less than Ni (in terms of the number of atoms. When two or more metal elements other than Li and Ni are included, the ratio of each of them is less than Ni) It is also meant to include complex oxides contained in The metal element is selected from the group consisting of, for example, Co, Al, Mn, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. Or one or more elements. The same applies to lithium cobalt oxides and lithium manganese oxides.

Also, the composition is of the general formula:
_{Li (Li a Mn x Co y} Ni z) O 2
(A, x, y, and z in the previous equation satisfy a + x + y + z≈1 and xyz ≠ 0.)
A so-called ternary lithium transition metal oxide containing three kinds of transition metal elements, and a general formula:
xLi [Li _1/3 Mn _2/3 ] O _2. (1-x) LiMeO ₂
(In the above formula, Me is one or more transition metals, and x satisfies 0 <x ≦ 1.)
It may be a so-called solid solution type lithium-excess transition metal oxide or the like. These lithium transition metal oxides are shown in the above general formula for clarifying the structure, but a part of transition metal elements (less than 50 atomic%) in the above formula are exemplified by Co, Needless to say, it may be substituted with one or more elements selected from the group of metal elements consisting of Al, Mn, Cr, Fe,. Such a lithium transition metal oxide is, for example, specifically a lithium excess transition having a D ₅₀ of about 3 to 8 μm and a specific surface area (according to the BET method) of about 0.5 to 1.9 m ² / g. A preferred example is the use of metal oxides. By using, for example, a lithium-excess transition metal oxide, a solid solution type lithium-excess transition metal oxide, or the like as the positive electrode active material, a lithium ion battery having both high output characteristics and high rate characteristics can be constructed.
In the present specification, D ₅₀ represents an average particle size represented by a cumulative 50% particle size (volume basis) in a particle size distribution measured by a laser diffraction scattering method. _Hereinafter, the average particle size and _{D 50} is used with consent.

Further, the positive electrode active material has a general formula of LiMAO ₄ (where M is at least one metal element selected from the group consisting of Fe, Co, Ni and Mn, and A is P, Si, S and And a polyanionic compound selected from the group consisting of V.).

  The compound which comprises such a positive electrode active material can be prepared and prepared by a well-known method, for example. For example, some raw material compounds appropriately selected according to the composition of the target positive electrode active material are mixed at a predetermined ratio, and the mixture is fired by an appropriate means. Thereby, for example, an oxide as a compound constituting the positive electrode active material can be prepared. In addition, the preparation method of a positive electrode active material (typically lithium transition metal oxide) itself does not characterize this invention at all.

  Moreover, although there is no strict restriction | limiting about the shape of a positive electrode active material, the positive electrode active material prepared as mentioned above can be grind | pulverized, granulated, and classified by an appropriate means. For example, a lithium transition metal oxide powder substantially composed of secondary particles having an average particle size in the range of about 1 μm to 25 μm (typically about 2 μm to 15 μm) is used as the positive electrode in the technology disclosed herein. It can preferably be employed as an active material. Thereby, the granular positive electrode active material powder substantially comprised by the secondary particle which has a desired average particle diameter and / or particle size distribution can be obtained.

  The conductive material has a role of securing a conductive path between the positive electrode active material and the positive electrode current collector 32 that are not highly conductive. As this conductive material, various conductive materials having good conductivity can be used. As the conductive material, various conductive materials having good conductivity can be used. For example, carbon materials such as carbon powder and fibrous carbon are preferably used. More specifically, various carbon blacks (for example, acetylene black, furnace black, graphitized carbon black, ketjen black), carbon powder such as graphite powder, acicular graphite, vapor grown carbon fiber (VGCF), etc. It may be fibrous carbon or the like. These may use together 1 type, or 2 or more types. Alternatively, conductive metal powder such as nickel powder may be used.

  As the binder, a polymer that can be dissolved or dispersed in a solvent used in forming the positive electrode active material layer 34 can be used. For example, when forming the positive electrode active material layer 34 using an aqueous solvent, cellulosic polymers such as carboxymethyl cellulose (CMC) and hydroxypropyl methyl cellulose (HPMC), for example, polyvinyl alcohol (PVA), polytetrafluoro Fluorine resins such as ethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), vinyl acetate copolymer, styrene butadiene copolymer (SBR), acrylic acid modified SBR resin (SBR latex), etc. Water-soluble or water-dispersible polymers such as rubbers can be preferably used. Moreover, when forming the positive electrode active material layer 34 using a nonaqueous solvent, polymers such as polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVdC), and polyacrylonitrile (PAN) can be preferably used.

  The positive electrode active material layer 34 is prepared, for example, by preparing a positive electrode active material layer forming composition in a paste form (or a slurry form or the like) obtained by mixing the above-described positive electrode active material, conductive material, and binder with a solvent. Then, it can be formed by applying this to the positive electrode current collector 32, drying and rolling. At this time, as the solvent for the composition for forming a positive electrode active material layer, any of an aqueous solvent and a non-aqueous solvent can be used. A suitable example of a non-aqueous solvent is typically N-methyl-2-pyrrolidone (NMP). The polymer material exemplified as the binder may be used for the purpose of exhibiting a function as a thickener or other additive of the composition for forming a positive electrode active material layer in addition to the function as a binder. Note that a vehicle may be used instead of the solvent.

  Moreover, although it does not necessarily restrict | limit, For example, it is illustrated that the usage-amount of a electrically conductive material shall be 1-20 mass parts (preferably 5-15 mass parts) with respect to 100 mass parts of positive electrode active materials. The binder is exemplified by 0.5 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material.

The negative electrode 50 includes a negative electrode active material layer 54 containing a negative electrode active material on a negative electrode current collector 52.
As the negative electrode current collector 52, a metal suitable for the negative electrode can be preferably used. For example, a rod-like body, a plate-like body, a foil-like body, a net-like body or the like mainly composed of copper, nickel, titanium, stainless steel, or the like can be used. In this example, specifically, the negative electrode current collector 52 is a strip-shaped copper foil having a predetermined width and a thickness of approximately 10 μm. In such a negative electrode current collector 52, an uncoated portion 53 is set along one edge portion in the width direction. The negative electrode active material layers 54 are formed on both surfaces of the negative electrode current collector 52 except for the uncoated portion 53 set on the negative electrode current collector 52.

  In this embodiment, the negative electrode active material layer 54 mainly includes a granular negative electrode active material, and the negative electrode active material is fixed onto the negative electrode current collector 52 with a binder. The negative electrode active material layer 54 is typically formed by applying a negative electrode active material layer-forming composition containing these negative electrode active material and binder onto the negative electrode current collector 52. In the negative electrode active material layer 54 formed in this manner, voids are formed between the negative electrode active material particles so that the electrolyte solution can penetrate.

As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. For example, a particulate carbon material (carbon particles) including a graphite structure (layered structure) at least in part. More specifically, examples of the negative electrode active material include natural graphite, graphite (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), and amorphous materials of these carbon materials. It may be a carbon material coated with carbonaceous material or a carbon material combining two or more of these. For example, specifically, graphite coated with amorphous carbon having a D ₅₀ of about 8 to 11 μm and a specific surface area (by the BET method) of about 3.5 to 5.5 m ² / g is used. Is shown as a preferred example.

  As the negative electrode active material, for example, a metal compound (preferably silicide or metal oxide) containing Si, Ge, Sn, Pb, Al, Ga, In, As, Sb, Bi, or the like as a constituent metal element is used. You may do it. For example, LTO (lithium titanate) can also be used as the negative electrode active material particles. About the negative electrode active material which consists of a metal compound, the surface of a metal compound may be fully coat | covered with a carbon film, for example, and you may use as a granular material excellent in electroconductivity. In this case, the negative electrode active material layer may not contain a conductive material, and the blending amount of the following conductive material may be reduced as compared with the case where the carbon coating is not performed. The additional aspect of these negative electrode active materials and forms, such as a particle size, can be suitably selected according to a desired characteristic.

  Although not particularly limited, the negative electrode active material layer 54 may contain a conductive material. The conductive material can be used for the purpose of securing a conductive path between the negative electrode active material that is not highly conductive and the negative electrode current collector 52. As such a conductive material, the conductive material in the positive electrode active material layer can be similarly used.

As the binder, solvent, and thickener of the negative electrode active material layer 54, the materials exemplified as the binder, solvent, and thickener of the positive electrode active material layer 34 can be similarly used.
As the solvent, any of an aqueous solvent and a non-aqueous solvent used in the positive electrode active material layer 34 can be used. A suitable example of the non-aqueous solvent is N-methyl-2-pyrrolidone (NMP).
The polymer material exemplified as the binder of the positive electrode active material layer 34 is used for the purpose of exhibiting the function as a thickener and other additives of the composition for forming the negative electrode active material layer in addition to the function as a binder. It can be done.

  In addition, when using a electrically conductive material, the usage-amount shall be about 1-30 mass parts (preferably about 2-20 mass parts, for example, about 5-10 mass parts) with respect to 100 mass parts of negative electrode active materials. Is exemplified. Moreover, the usage-amount of a binder with respect to 100 mass parts of negative electrode active materials can be 0.5-10 mass parts, for example.

The separators 70A and 70B are constituent members that insulate the positive electrode 30 and the negative electrode 50, hold the electrolyte, and allow the movement thereof. As described above, of the separators 70 </ b> A and 70 </ b> B, the single-sided HRL separator 70 </ b> A includes the heat-resistant layer 74 containing an inorganic filler on one side of the base material 72, and the double-sided HRL separator 70 </ b> B Provided on both sides.
The base material 72 is not particularly limited as long as it is insulative and has a porous body, a nonwoven fabric body, a cloth body or the like having fine pores that can move lithium ions as a charge carrier. For example, a porous sheet made of resin (a microporous resin sheet) can be preferably used. The resin material is not essentially limited, and a resin material similar to the conventional one can be used. Typically, polyethylene (PE), polypropylene (PP), polystyrene, polytetrafluoroethylene, polyamide (particularly preferably aramid), polyimide, polyvinylidene fluoride, polyacrylonitrile, polyamideimide, and the like can be given.

  In particular, for the single-sided HRL separator 70A, it is desirable that the base material 72 has a shutdown function and that the surface has heat resistance. Therefore, the base material 72 of the separators 70A and 70B has a laminated structure including at least a polyethylene layer made of polyethylene and a heat resistant resin layer made of a resin having higher heat resistance than the polyethylene, and this heat resistant resin. In a preferred embodiment, the layer constitutes a surface of the substrate 72 opposite to the surface provided with the heat-resistant layer 74. When the single-sided HRL separator 70A has such a configuration, the heat-resistant layer 74 is provided on one surface and the heat-resistant resin layer is provided on the other surface. As the intermediate layer, at least a polyethylene (PE) layer can be provided. When the double-sided HRL separator 70B has such a configuration, the heat-resistant layer 74 is provided on both sides, and at least a polyethylene (PE) layer and a heat-resistant resin layer are provided as intermediate layers.

Polyethylene can be a material suitable for forming a layer that exhibits a shutdown function because it is easily available and the setting of the softening point and melting point is simple. Although there is no restriction | limiting in particular in the shutdown temperature by this PE layer, For example, suitable temperature can be selected and set in the temperature range of about 80 to 130 degreeC. The resin having higher oxidation resistance than polyethylene is not particularly limited. For example, various polymers having a heat-resistant temperature of 110 ° C. or higher (eg, 130 ° C. or higher) can be used. Specifically, for example, polycarbonate such as polypropylene, polyimide, polyamideimide, polyamide, wholly aromatic polyamide, polyetherimide, polysulfone, polyethersulfone, or a polymer composed of a combination thereof is exemplified. Among these, it is also possible to consider using functional polymers called engineering plastics such as wholly aromatic polyamide, polyimide, polyamideimide, polysulfone, and polyethersulfone. In general, these functional polymers can be materials excellent in properties such as mechanical properties and solvent resistance in addition to heat resistance. Such a substrate 72 may have a two-layer structure or a structure of three or more layers. In addition, it is more preferable that the base material 72 has, for example, a two-layer structure or a three-layer structure from the viewpoint of keeping the volume of the separators 70A and 70B smaller. Thereby, separator 70A, 70B can be equipped with the shutdown function in predetermined | prescribed temperature while being provided with heat resistance and durability, keeping the thickness thinner. For example, even when a short circuit occurs inside the battery due to the inevitable mixing of metallic foreign matter or the like, it can have durability against local heat generation on the surface of the negative electrode 50.
Although there is no strict restriction | limiting in the thickness of the base material 72, For example, it is desirable to set it as the thickness of about 10 micrometers-30 micrometers, More preferably, about 15 micrometers-25 micrometers.

The heat-resistant layer 74 can be composed of an inorganic filler and a binder for binding the inorganic fillers to each other and fixing them to the base material 72.
As the inorganic filler, various insulating inorganic materials can be used. For example, one or more kinds selected from fillers such as insulating metal oxides and metal hydroxides, glass, various inorganic minerals and inorganic pigments can be used. For example, specifically, alumina (Al ₂ O ₃ ), boehmite (Al ₂ O ₃ .H ₂ O), magnesia (MgO), mica, talc, titania, glass beads, glass fiber, and the like can be used. As such an inorganic filler, it is more preferable to use alumina (Al ₂ O ₃ ), boehmite (Al ₂ O ₃ .H ₂ O), etc. which are stable in quality and inexpensive and easily available. The average particle diameter (D ₅₀ ) of the inorganic filler can be, for example, about 0.1 μm to 5.0 μm, and more preferably about 0.2 μm to 2.0 μm. The specific surface area of such inorganic filler, the specific surface area based on BET ^method, can be used about 2.8m ² / g~100m 2 / g as a rough guide.
As the binder, those similar to the binder in the positive electrode and negative electrode active material layers 34 and 54 can be appropriately selected and used.

  The heat-resistant layer 74 is prepared, for example, by preparing a paste-like (slurry) composition obtained by mixing the above-described inorganic filler and binder with a solvent or a vehicle, and applying this to one or both sides of the base material 72 and drying. Can be formed. Regarding the single-sided HRL separator 70A, when the substrate 72 has a multilayer structure, the heat-resistant layer 74 is formed on the surface opposite to the heat-resistant resin layer. At this time, any of an aqueous solvent and a non-aqueous solvent can be used as the solvent of the composition. A suitable example of a non-aqueous solvent is typically N-methyl-2-pyrrolidone (NMP). In addition, the polymer material exemplified above as a binder may be used for the purpose of exhibiting a function as a thickener or other additive of the composition in addition to the function as a binder. In addition, although it does not specifically limit, the mass ratio of the binder which occupies for the heat-resistant layer 74 can be set to a desired value within the range of 1 mass%-60 mass%, for example. Moreover, the solid content rate of the composition for heat-resistant layer formation can be about 30 mass%-50 mass%, for example. The solid content of the paste-like composition to be adjusted when forming the heat-resistant layer 74 is typically adjusted to about 40% by mass for solvent-based compositions and 50% to 52% by mass for aqueous-based compositions. can do. However, it goes without saying that the binder amount and solid content are not limited to the above values.

Although there is no strict limitation on the thickness of the heat-resistant layer 74 to be formed, the thickness is about 3 μm to 12 μm when formed on only one side of the substrate 72 and the total thickness when formed on both sides. Is preferred. For example, it is desirable that the thickness be about 3 μm to 10 μm, and more specifically about 4 μm to 7 μm.
The thickness of the separators 70A and 70B as a whole is preferably about 40 μm or less, for example, about 15 μm to 35 μm, and more specifically about 20 μm to 30 μm. About the single-sided HRL separator 70A, for example, it is desirable to set it to 35 μm or less, for example, about 10 μm to 30 μm, and more specifically about 15 μm to 25 μm.
In the example shown in FIGS. 2 to 4, as the separators 70 </ b> A and 70 </ b> B, a strip-shaped sheet material having a predetermined width and having a plurality of minute holes is used. Here, the width b1 of the negative electrode active material layer 54 is slightly wider than the width a1 of the positive electrode active material layer 34. The widths c1 and c2 of the separators 70A and 70B are slightly larger than the width b1 of the negative electrode active material layer 54 (c1, c2>b1> a1).

In the above secondary battery, appropriately controlling the capacity ratio between the positive electrode active material layer 34 and the negative electrode active material layer 54 facing each other through the separators 70A and 70B not only improves the battery characteristics, This is important in considering suppression of charge carrier deposition. Such a capacity ratio is also affected by the application and use conditions of the battery, and thus it is difficult to strictly limit the capacity ratio. However, in the invention disclosed herein, one capacity that is opposed via the separators 70A and 70B. In the positive electrode active material layer 34 and one negative electrode active material layer 54, the counter capacity defined by the ratio of the initial charge capacity (C _N ) of the negative electrode active material layer 54 to the initial charge capacity (C _P ) of the positive electrode active material layer 34. By setting the ratio (C _N / C _P ) as a rough standard in the range of 1.4 to 2.0, for example, in the range of 1.5 to 1.9, these balances are controlled in a more suitable range. Like to do. The facing capacity ratio (C _N / C _P ) may be, for example, 1.2 or more, but by limiting it to 1.4 or more, the lithium acceptability of the negative electrode is further increased, and in the case of quick charging or the like. Lithium precipitation on the surface of the negative electrode active material layer 54 can be effectively suppressed. It is more effective to set the facing capacity ratio (C _N / C _P ) to, for example, 1.5 or more, and more specifically 1.6 or more. On the other hand, if the facing capacity ratio (C _N / C _P ) exceeds 2.0 and is too large, the value of the irreversible capacity with respect to the initial capacity of the battery becomes large, and the battery capacity (energy density) per fixed volume becomes small. This is not preferable. The facing capacity ratio (C _N / C _P ) is preferably 1.9 or less, for example, 1.8 or less.

Note that the initial charge capacity (C _P ) of the positive electrode active material layer can be measured, for example, by the following method. That is, a measurement cell (half battery) is constructed by using a positive electrode having a positive electrode active material layer on a positive electrode current collector punched into a predetermined size as a measurement electrode and using a metal lithium electrode as a counter electrode. For the measurement cell, the positive electrode active material was changed to lithium until the potential of the measurement electrode was 4.2 V (metal lithium reference; hereinafter, the metal lithium reference voltage was expressed as “V (vs. Li / Li ⁺ )”). First, ions are desorbed, and then lithium ions are inserted into the positive electrode active material (typically, lithium ions are inserted until the potential of the measurement electrode reaches 3.0 V (vs. Li / Li ⁺ )). In this way, the initial charge capacity [mAh / cm ² ] per unit area of the positive electrode is determined. By multiplying this by the formation area [cm ² ] of the positive electrode active material layer of the positive electrode included in the secondary battery, the initial charge capacity (C _P ) of the positive electrode active material layer is calculated. In addition, the initial charge capacity (C _N ) of the negative electrode active material layer was determined by constructing a measurement cell with the negative electrode as in the case of the positive electrode, and until the potential of the measurement electrode reached 0.02 V in the first charge / discharge cycle. First charge / discharge in which lithium ions are inserted into the active material and then released (typically, lithium ions are released until the potential of the measurement electrode reaches 1.5 V (vs. Li / Li ⁺ )). By performing the cycle, it can be calculated in the same manner as in the case of the positive electrode. Thus from C _P and C _N is grasped, it is possible to determine counter capacity ratio of the positive electrode active material layer and the anode active material layer _(C N _/ C _P).

  In this example, as shown in FIG. 1, the battery case 80 uses a so-called rectangular battery case, and includes a container body 84 and a lid 82. The container body 84 is a flat box-shaped container having a bottomed rectangular tube shape and having one side surface (upper surface in the figure) opened. The lid 82 is a member that is attached to the opening (opening on the upper surface) of the container body 84 and closes the opening.

  In an in-vehicle secondary battery, it is desired to improve the weight energy efficiency (battery capacity per unit weight) in order to improve the fuel efficiency of the vehicle. For this reason, in this embodiment, lightweight metals, such as aluminum and aluminum alloy, are employ | adopted for the container main body 84 and the cover body 82 which comprise the battery case 80. FIG. Thereby, the weight energy efficiency can be improved.

  The battery case 80 has a flat rectangular internal space as a space for accommodating the wound electrode body 20. Further, as shown in FIG. 2, the flat internal space of the battery case 80 is slightly wider than the wound electrode body 20. A positive terminal 40 and a negative terminal 60 are attached to the lid 82 of the battery case 80. The positive and negative terminals 40 and 60 penetrate the battery case 80 (lid 82) and protrude outside the battery case 80. The lid 82 is provided with a liquid injection hole 86 and a safety valve 88.

  As already described, the wound electrode body 20 has a long positive electrode (positive electrode sheet) 30, a long negative electrode (negative electrode sheet) 50, and two long separators 70A and 70B. . In producing the wound electrode body 20, in the example shown in FIG. 3, the single-sided HRL separator 70A, the negative electrode sheet 50, the double-sided HRL separator 70B, and the positive electrode sheet 30 are laminated in this order from the bottom. At this time, the single-sided HRL separator 70A is arranged so that the heat-resistant layer 74 of the single-sided HRL separator 70A is on the lower surface (outer peripheral side). Further, the uncoated portion 33 of the positive electrode active material layer 34 of the positive electrode sheet 30 and the uncoated portion 53 of the negative electrode active material layer 54 of the negative electrode sheet 50 protrude from both sides in the width direction of the separators 70A and 70B, respectively. The positive electrode sheet 30 and the negative electrode sheet 50 are overlapped with a slight shift in the width direction. The electrode body thus superposed is wound so that the single-sided HRL separator 70A is on the outer peripheral side. That is, the heat-resistant layer 74 is positioned on the outer peripheral side with respect to the base material 72 of the single-sided HRL separator 70A. Subsequently, the flat wound electrode body 20 can be produced by crushing and ablating the obtained wound body from a direction perpendicular to the winding axis WL. Thereby, the wound electrode body 20 in which the heat resistant layer 74 does not face the negative electrode active material layer 54 on the wound outer peripheral side can be constructed.

  In the central portion of the wound electrode body 20 in the winding axis (WL) direction, a wound core portion (that is, the positive electrode active material layer 34 of the positive electrode sheet 30, the negative electrode active material layer 54 of the negative electrode sheet 50, the separator 70A, 70B) is formed. In addition, uncoated portions 33 and 53 of the positive electrode sheet 30 and the negative electrode sheet 50 protrude outward from the wound core portion at both ends of the wound electrode body 20 in the winding axis direction. The positive electrode lead terminal 41 and the negative electrode lead terminal 61 are provided on the positive electrode side protruding portion (that is, the uncoated portion 33 of the positive electrode current collector 32) and the negative electrode side protruding portion (that is, the uncoated portion 53 of the negative electrode current collector 52). Are respectively attached and electrically connected to the positive electrode terminal 40 and the negative electrode terminal 60 described above. At this time, for example, ultrasonic welding is used to connect the positive electrode lead terminal 41 and the positive electrode current collector 32 due to the difference in the materials. Further, for example, resistance welding is used for welding the negative electrode lead terminal 61 and the negative electrode current collector 52. The wound electrode body 20 is accommodated in a flat internal space of the container body 84 as shown in FIG. The container body 84 can be sealed by the lid 82 after the wound electrode body 20 is accommodated. The joint of the lid body 82 and the container main body 84 is sealed by welding, for example, by laser welding. Thus, in this example, the wound electrode body 20 is positioned in the battery case 80 by the positive terminal 40 and the negative terminal 60 fixed to the lid 82 (battery case 80).

Thereafter, an electrolyte is injected into the battery case 80 from a liquid injection hole 86 provided in the lid 82. As the electrolyte used here, one kind or two or more kinds similar to the non-aqueous electrolyte used in the conventional lithium secondary battery can be used without any particular limitation. Such a non-aqueous electrolyte typically includes a lithium salt as a supporting salt in a non-aqueous solvent (typically an organic solvent). A nonaqueous electrolyte that is liquid at room temperature (that is, an electrolytic solution) can be preferably used. As the lithium salt, for example, a known lithium salt conventionally used as a supporting salt for a non-aqueous electrolyte of a lithium secondary battery can be appropriately selected and used. For example, as such lithium salt, for example, LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiClO _{4 and the} like are exemplified. These supporting salts can be used alone or in combination of two or more. A particularly preferred example is LiPF ₆ . The non-aqueous electrolyte contains, for example, a non-aqueous electrolyte containing the supporting salt at a concentration of about 0.1 mol / L to 5 mol / L, for example, about 0.8 mol / L to 1.5 mol / L. Can be preferably used. Further, it may be a solid (gel) electrolytic solution in which a polymer is added to the liquid electrolytic solution.

  As the non-aqueous solvent, aprotic solvents such as carbonates, esters, ethers, nitriles, sulfones and lactones can be used. For example, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, Examples include 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, and γ-butyrolactone.

  Various additives can be contained in the electrolytic solution. For example, as an overcharge preventive agent, the oxidation potential is higher than the operating voltage of the lithium secondary battery (for example, 4.2 V or higher in the case of a lithium secondary battery that is fully charged at 4.2 V) and is oxidized. A compound that generates a large amount of gas can be used without particular limitation. For example, a lithium secondary battery that is fully charged at 4.2 V preferably has an oxidation reaction potential in the range of 4.6 V to 4.9 V. For example, a biphenyl compound, a cycloalkylbenzene compound, an alkylbenzene compound, an organic phosphorus compound, a fluorine atom-substituted aromatic compound, a carbonate compound, a cyclic carbamate compound, an alicyclic hydrocarbon, and the like can be given. More specifically, biphenyl (BP), alkylbiphenyl, terphenyl, 2-fluorobiphenyl, 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4′-difluorobiphenyl, cyclohexylbenzene (CHB), trans-butylcyclohexyl Benzene, cyclopentylbenzene, t-butylbenzene, t-aminobenzene, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, tris- (t-butylphenyl) phosphate, phenyl fluoride, 4-fluorophenyl acetate, diphenyl carbonate, Examples thereof include methyl phenyl carbonate, bicterary butyl phenyl carbonate, diphenyl ether, dibenzofuran, and the like. In particular, cyclohexylbenzene (CHB) and a cyclohexylbenzene derivative are preferably used. The amount of the overcharge inhibitor used relative to 100% by mass of the electrolytic solution used is, for example, about 0.01 to 10% by mass, preferably about 0.1 to 5% by mass.

In this example, an electrolytic solution in which LiPF ₆ is contained at a concentration of about 1 mol / liter in a mixed solvent of ethylene carbonate and diethyl carbonate (for example, a mixed solvent having a volume ratio of about 1: 1) is used. Yes. Thereafter, a metal sealing cap 87 is attached (for example, welded) to the liquid injection hole to seal the battery case 80.

  In the lithium secondary battery 10, the positive electrode current collector 32 and the negative electrode current collector 52 are electrically connected to an external device through electrode terminals 40 and 60 that penetrate the battery case 80. Thereby, the lithium secondary battery 10 as a nonaqueous electrolyte secondary battery is provided.

  In this lithium secondary battery 10, the base materials 72 of the separators 70A and 70B are not arranged to face each other. For this reason, the base materials 72 do not adhere to each other even when the temperature of the battery increases due to, for example, overcurrent. Therefore, for example, the possibility that the separators 70 </ b> A and 70 </ b> B are broken is suppressed to be lower than the configuration in which the base materials 72 face each other. Therefore, the problem of a short circuit due to the adhesion between the opposing base materials 72 is solved, and the leakage current after the battery is shut down can be reduced. That is, the lithium secondary battery 10 having high thermal stability of the electrode body 20 and more excellent in safety and reliability is provided.

  The nonaqueous electrolyte battery disclosed herein has been described above. However, the detailed configuration, form, capacity, application, and the like of the secondary battery are not limited to the above examples. For example, in the above description, a secondary battery including a wound electrode body has been described in detail with reference to the drawings. However, the invention disclosed herein can also be suitably applied to a stacked electrode body. In addition, the explanation has been given for the square type secondary battery, but the shape (for example, metal casing, cylindrical type, button type, laminated film structure) and size of the battery case constituting the battery, or the positive and negative active There are no particular restrictions on the components of the substance.

  Next, an embodiment of the present invention will be described. However, the following description is not intended to limit the present invention to such specific examples.

[Preparation of evaluation cell]
As an evaluation cell, a lithium secondary battery including a wound electrode body was constructed according to the following procedure.
≪Separator≫
In forming a heat-resistant layer in the separator, a paste for forming a heat-resistant layer was prepared. The paste comprises alumina (D ₅₀ : 0.9 μm, BET specific surface area: 18 m ² / g) as an inorganic filler, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose CMC as a thickener. It was prepared by mixing with ion-exchanged water so that the mass ratio of these materials was 97: 2: 1 as alumina: binder: thickener. For the preparation of the paste, an ultrasonic disperser (manufactured by M Technique, CLEARMIX) was used, and mixing and kneading were performed under conditions of 15,000 rpm for 5 minutes as preliminary dispersion and 15 minutes at 20000 rpm as main dispersion.

Next, a PP / PE / PP microporous membrane composed of polypropylene (PP) and polyethylene (PE) is used as the base material, and (A) only one side of this base material or (B) The heat-resistant layer forming paste prepared as described above was applied to both surfaces. A substrate having a thickness of 20 μm and a shutdown temperature (PE layer softening point) of 128 ° C. was prepared. The heat-resistant layer forming paste was applied by a gravure coating method. As coating conditions, a gravure roll having a line number: # 100 lines / inch and an ink holding amount: 19.5 ml / cm ² was used, the coating speed was 3 m / min, the gravure roll speed was 3.8 m / min, and the gravure The coating was performed under the condition of a speed / coating speed ratio of 1.27. The separator after the coating was dried to form a heat resistant layer. The total thickness of the separator was (A) a single-sided HRL separator having a heat-resistant layer formed on only one side, and (B) a double-sided HRL separator having a heat-resistant layer formed on both sides was 30 μm.

≪Negative electrode≫
First, with respect to 96% by mass of natural graphite powder, these were mixed and impregnated so that the pitch was 4% by mass, and the surface was non-coated by firing at 1000 ° C. to 1300 ° C. for 10 hours in an inert atmosphere. Graphite coated with crystalline carbon was prepared. The resulting amorphous carbon-coated graphite _{is, D 50} is 10.5 [mu] m, BET specific surface area of 3.8 m ² / g.
The amorphous carbon-coated graphite is used as a negative electrode active material, and a styrene butadiene block copolymer (SBR) as a binder and carboxymethyl cellulose (CMC) as a thickener are used in a mass ratio of these materials. Was mixed with ion-exchanged water so as to be 98.6: 0.7: 0.7, thereby preparing a negative electrode active material layer forming paste. With this paste, a coating amount (weight per unit area) of the negative electrode active material per unit area is 7 on both sides of a copper foil (thickness 10 μm) as a negative electrode current collector while leaving an uncoated part along one end. The coating was applied to ³ mg / cm ² and dried. After drying, rolling was performed with a rolling press so that the density of the negative electrode active material layer was approximately 1.0 to 1.2 g / cm ³ . This was slit so as to have a predetermined width, and a negative electrode having a negative electrode active material layer width of 102 mm and a length of 3200 mm was produced.

≪Positive electrode≫
Ni _0.34 Co _0.33 Mn _0.33 (OH) ₂ is a basic component by mixing aqueous solutions of nickel sulfate, cobalt sulfate and manganese sulfate at a predetermined ratio and neutralizing with sodium hydroxide. A precursor was prepared. This precursor is mixed with lithium carbonate at a predetermined ratio, and calcined in the air at a temperature range of 800 ° C. to 950 ° C. for 24 hours, so that the general formula Li _1.14 Ni _0.34 Co _0.33 Mn ₀ A lithium transition metal composite oxide having a composition represented by _.33 O ₂ was prepared. This lithium transition metal composite oxide had a D ₅₀ of 6.0 μm and a BET specific surface area of 1.1 m ² / g.
Using such a ternary lithium-excess transition metal composite oxide as a positive electrode active material, using acetylene black (AB) as a conductive material and polyvinylidene fluoride (PVDF) as a binder, these materials can be used in a mass ratio. A positive electrode active material layer forming paste was prepared by mixing with NMP so as to be 90: 8: 2. Next, the coating amount (weight per unit area) of the positive electrode active material per unit area is approximately 11.3 on both sides while leaving an uncoated part along one end of the aluminum foil (thickness 15 μm) as the positive electrode current collector. The positive electrode active material layer forming paste was applied and dried at ² mg / cm ² to form a positive electrode active material layer. After drying, rolling was performed with a rolling press so that the density of the positive electrode active material layer was approximately 1.9 to 2.3 g / cm ³ . This was slit to have a predetermined width, and a positive electrode having a positive electrode active material layer width of 90 mm and a length of 3000 mm was produced.

≪Assembly of evaluation cell≫
A lithium secondary battery for evaluation was constructed using the two separators prepared above, and the positive electrode and the negative electrode one by one. That is, the positive electrode and the negative electrode are laminated with the separator interposed therebetween so that the uncoated portions of the positive electrode and the negative electrode are located on the opposite side, and the negative electrode active material layer covers the positive electrode active material layer in the width direction. The wound electrode body was produced by winding it in a spiral shape and then letting it into a flat shape. The separators used and how to arrange them are as follows. The number of windings in the wound electrode body was 30 turns.

<Sample 1>
Sample 1 was a wound electrode body in which two single-sided HRL separators (A) each having a heat-resistant layer only on one side were used so that the two heat-resistant layers were opposed to the negative electrode active material layer.
<Sample 2>
A wound electrode body using two double-sided HRL separators (B) each having a heat-resistant layer on both sides, that is, a heat-resistant layer disposed so as to face both the negative electrode active material layer and the positive electrode active material layer, did.
<Sample 3>
Sample 3 was a wound electrode body in which two single-sided HRL separators (A) each having a heat-resistant layer only on one side were used so that the two heat-resistant layers were opposed to the positive electrode active material layer.
<Sample 4>
A single-sided HRL separator (A) provided with a heat-resistant layer only on one side and a double-sided HRL separator (B) provided with a heat-resistant layer on both sides one by one, and the substrate surface of the single-sided HRL separator (A) in the wound electrode body A wound electrode body disposed so as to face the wound outer peripheral side of the negative electrode was designated as sample 4.

These wound electrode bodies were accommodated in a rectangular battery case made of aluminum together with a nonaqueous electrolyte, and sealed to construct lithium secondary batteries 1 to 4 for evaluation. As the non-aqueous electrolyte, 1.1 mol as a lithium salt was added to a mixed solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed at 3: 3: 4 (volume ratio). / L LiPF ₆ (LPFO), difluorophosphate (LiPO ₂ F ₂ ) and lithium bisoxalate borate (Li [B (C ₂ O ₄ )] ₂ ) as additives, each 0.025 mol / L What was dissolved one by one was used.
The battery capacities of the evaluation lithium secondary batteries 1 to 4 are 3.8 Ah. Moreover, when the facing capacity ratio was determined from the measured values of the initial charge capacity of the positive electrode active material layer and the negative electrode active material layer, the value was 1.8.

[Evaluation of thermal stability]
Thermal stability was evaluated under the following conditions for the evaluation lithium secondary batteries 1 to 4 constructed as described above. That is, after performing an appropriate initial conditioning process, the battery was forcibly shut down by performing a continuous main charge test, and the magnitude of the leakage current thereafter was evaluated.
Specifically, as an initial conditioning process, a constant current charge is performed at room temperature (25 ° C.) at a charge rate of 1/10 C for 3 hours, and then a constant current constant voltage up to 4.1 V at a charge rate of 1/3 C. The operation of charging at 3 and the operation of discharging at a constant current up to 3.0 V at a discharge rate of 1/3 C were repeated 2-3 times.

As a continuous main charge test, low current discharge was performed at 0 ° C. until the state of SOC was 30%, and then constant current charge was performed from the state of SOC of 30% until the maximum voltage reached 40 V at a current of 60A. In the continuous main charging test, the current value (leakage current value) for 10 minutes after the battery was shut down was measured, and the maximum current value in 10 minutes was shown as “leakage current value” in Table 1.
Moreover, the battery after the continuous main charging test was disassembled, and the state of the electrode body was observed.

  As can be seen from the results in Table 1, Sample 1 and Sample 2 had significantly larger leakage current values than Sample 3 and Sample 4. When Sample 1 and Sample 2 were disassembled, it was confirmed that the separators were fused in these batteries so as to sandwich the positive electrode. Sample 1 and sample 2 both include a structure in which the negative electrode active material layer on the wound outer peripheral side and the heat-resistant layer of the separator face each other, and in particular, a relatively large amount in the negative electrode active material layer on the wound outer peripheral side of the wound curved portion. It was observed that the separator and the negative electrode active material layer were adhered to each other depending on the location. From these facts, sample 1 and sample 2 are fixed in a relatively large number of locations because the negative electrode active material layer on the outer periphery of the winding and the heat-resistant layer of the separator adhere to each other and the separator shrinks during shutdown. This is considered to have led to an increase in leakage current after shutdown.

On the other hand, although sample 3 and sample 4 have relatively low leakage current, sample 4 has a lower leakage current value than sample 3. When sample 3 and sample 4 were disassembled, in sample 3, two separators were fused so as to sandwich the negative electrode, whereas in sample 4, the adhesion and fusion of the separators were not confirmed. From this, it is considered that in Sample 3, the opposing separator was fused, and this further contracted during shutdown, resulting in damage to the separator and increased leakage current after shutdown.
On the other hand, in the lithium secondary battery of Sample 4 of the invention disclosed herein, in the wound electrode body, the base material is arranged without arranging the heat-resistant layer on the outer peripheral side of the negative electrode active material layer, and other active batteries are arranged. A heat-resistant layer is arranged on the surface of the material layer. Therefore, adhesion between the separator and the negative electrode active material layer and adhesion between the separators do not occur. Therefore, it is considered that the number of breakage points of the separator can be suppressed to a very low level, so that the amount of leakage current after shutdown is small and the thermal stability is improved.

  FIG. 7 conceptually shows the current and temperature behavior of the batteries of Samples 3 and 4 after shutdown in the continuous main charge test. In both the temperature curve and the current curve, the upper line represents sample 3 and the lower line represents sample 4. Compared to sample 3, sample 4 has a very small leakage current after shutdown, so that heat generation of the battery after shutdown is suppressed, and the battery temperature is stabilized low overall. That is, according to the invention disclosed herein, it was confirmed that the thermal stability after the battery shuts down due to overcharge or the like is kept good.

[Evaluation during meltdown]
The same evaluation lithium secondary battery as sample 4 was prepared, and the battery state during meltdown was confirmed. That is, the battery after the initial conditioning was charged at a constant current and a constant voltage at room temperature (25 ° C.) at a charge rate of 0.2 C to 4.2 V. A 5 kg weight was placed on the battery and placed in an oven, and the battery voltage state when the oven was heated to 200 ° C. was examined. As a result, a rapid drop in voltage was not observed during heating up to 200 ° C., and it was confirmed that an internal short circuit due to meltdown in which the separator melted was prevented.
As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

1 Vehicle 10 Non-aqueous electrolyte secondary battery (lithium ion battery)
20 Winding type electrode body 30 Positive electrode 32 Positive electrode current collector 33 Uncoated part 34 Positive electrode active material layer 40 Positive electrode terminal 50 Negative electrode 52 Negative electrode current collector 53 Uncoated part 54 Negative electrode active material layer 60 Negative electrode terminal 70 Separator 70A Single side HRL separator (separator)
70B Double-sided HRL separator (separator)
72 Base material 74 Heat-resistant layer 80 Battery case 82 Lid body 84 Container body 86 Injection port 88 Safety valve 100 Battery pack WL Winding shaft

Claims (8)

A positive electrode having a positive electrode active material layer on both sides of the positive electrode current collector, a negative electrode having a negative electrode active material layer on both sides of the negative electrode current collector, a separator A having a heat-resistant layer containing an inorganic filler on one side of the substrate, and A non-aqueous electrolyte secondary battery comprising a separator B having a heat-resistant layer on both surfaces of a base material and an electrolyte,
An electrode body in which the positive electrode and the negative electrode are laminated with each other via the separator A or B;
The surface of the positive electrode active material layer is laminated so that the heat-resistant layer contacts both surfaces,
The nonaqueous electrolyte secondary battery, wherein the surface of the negative electrode active material layer is disposed so that the heat-resistant layer is in contact with only one of the surfaces.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode body is wound to form a wound electrode body.   The nonaqueous electrolyte secondary battery according to claim 2, wherein the wound electrode body has a flat shape crushed in a direction substantially perpendicular to the winding axis. The separator A is disposed on the outer peripheral side of the negative electrode, and the separator B is disposed on the inner peripheral side,
The base material of the separator A is brought into contact with the surface of the negative electrode active material layer provided on the outer peripheral side with respect to the negative electrode current collector,
4. The non-aqueous electrolyte 2 according to claim 2, wherein the heat-resistant layer of the separator B is in contact with the surface of the negative electrode active material layer provided on the inner peripheral side with respect to the negative electrode current collector. Next battery. The base material of the separator A has a laminated structure including at least a polyethylene layer made of polyethylene and a heat resistant resin layer made of a resin having higher heat resistance than the polyethylene,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the heat-resistant resin layer constitutes a surface of the substrate opposite to a surface including the heat-resistant layer.   6. The non-aqueous electrolyte 2 according to claim 5, wherein the heat-resistant resin layer is any one selected from the group consisting of wholly aromatic polyamide, polyimide, polyamideimide, polysulfone, and polyethersulfone, or two or more. Next battery. In one positive electrode active material layer and one negative electrode active material layer opposed via the separator A or B, the initial charge capacity (C _P ) of the negative electrode active material layer with respect to the initial charge capacity (C _P ) of the positive electrode active material layer counter capacity ratio defined by the ratio of _{N) (C N / C P} ) is a 1.5 to 1.9, a non-aqueous electrolyte secondary battery according to any one of claims 1-6.   A vehicle comprising the nonaqueous electrolyte secondary battery according to any one of claims 1 to 7 as a driving power source.

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