JP5709008B2 - Nonaqueous electrolyte secondary battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the same. Specifically, the present invention relates to a nonaqueous electrolyte secondary battery having a shutdown function against abnormal battery heat generation and a method for manufacturing the same.

In recent years, non-aqueous electrolyte secondary batteries (typically lithium ion batteries) are light in weight and have high energy density, and thus have become increasingly important as high-power power supplies for vehicles or power storage systems. Yes. Various improvements have been made to further increase the capacity and energy density.
In this non-aqueous electrolyte secondary battery, the separator interposed between the positive electrode and the negative electrode prevents a short circuit due to contact between the positive electrode and the negative electrode for the purpose of ensuring the safety of the battery and the device in which the battery is mounted. It has a role (short-circuit prevention function). Further, when the separator reaches a certain temperature range (typically the softening point or melting point of the separator), the separator increases the resistance by blocking the ion conduction path. And it has the function (shutdown function) which stops charging / discharging by this resistance increase, and prevents the thermal runaway of a battery. In a general separator, the melting point (typically 130 ° C. or higher) of a resin such as a sheet-like polyolefin as a constituent material is a shutdown temperature, and when the separator reaches this temperature, Fine pores are blocked by melting or softening, and the resistance is increased.

  Various modes have been proposed as a shutdown function of such a nonaqueous electrolyte secondary battery. Patent Document 1 discloses, for example, a separator made of a porous film including a resin having a melting point in the range of 80 ° C. to 130 ° C., filler particles, and a porous substrate.

  Patent Document 2 includes a polymer compound having a melting point of 90 ° C. to 130 ° C. and a heat of fusion of 30 J / g or more as a heat absorbing material in a positive electrode of a nonaqueous electrolyte secondary battery together with a binder. Is disclosed. According to such a configuration, it is described that even when Joule heat is generated due to a short circuit, the heat absorbing material substantially contained in the positive electrode active material layer absorbs heat as melting heat, and thus it is possible to suppress the battery temperature from rising. .

JP 2007-157723 A Japanese Patent Laid-Open No. 10-064549 JP 2004-303572 A

However, according to the proposal of Patent Document 1, when the content of the resin is increased in order to enhance the shutdown function, the porosity of the porous film is lowered, resulting in a decrease in battery output. there were. Also in the proposal of Patent Document 2, when the content of the polymer compound is increased, the ratio of the positive electrode active material is decreased, which causes a similar problem of a decrease in battery output.
The present invention has been made in view of the above points, and the main object of the present invention is to achieve both of them without excessively degrading the battery performance even when the shutdown performance is improved. It is to provide a water electrolyte secondary battery.

  The nonaqueous electrolyte secondary battery disclosed herein includes a positive electrode having a positive electrode active material layer on a positive electrode current collector, a negative electrode having a negative electrode active material layer on a negative electrode current collector, the positive electrode and the negative electrode. A separator made of a thermoplastic resin interposed therebetween and a non-aqueous electrolyte are provided. And the said separator is equipped with the heat resistant layer containing the inorganic filler and the granular polymer A which has melting | fusing point in the temperature range of 80 to 100 degreeC on at least one surface. The positive electrode active material layer includes a positive electrode active material and a granular polymer B having a melting point in the temperature range of 120 ° C. or less exceeding the melting point of the granular polymer A.

  According to this configuration, the granular polymers A and B function as a so-called shutdown resin that melts at the melting point to block the ion conduction path and increase the internal resistance of the battery. And granular polymer A and B are mix | blended separately into two members, the heat-resistant layer of a separator, and a positive electrode active material layer. For this reason, the entire battery may contain a larger amount of granular polymers A and B as shutdown resins without excessively degrading battery performance such as battery capacity and internal resistance (hereinafter simply referred to as battery performance). it can.

  Further, the melting points of the granular polymers A and B are set so that the melting point of the granular polymer A is lower than the melting point of the granular polymer B at a temperature lower than that of the polyolefin resin constituting the separator substrate. Therefore, the shutdown function can be developed step by step according to the temperature distribution in the battery and its change over time. For example, when the temperature in the battery increases during abnormal heat generation, the shutdown function by the granular polymer A is first developed, then the shutdown function by the granular polymer B is developed, and then the shutdown by the substrate of the separator is developed. That is, by gradually increasing the resistance in the battery and suppressing the current from the stage where the temperature in the battery is low, it is possible to prevent the battery from generating heat at an accelerated rate. This provides a non-aqueous electrolyte secondary battery that is improved in safety and reliability against abnormal heat generation without significantly impairing the original battery performance.

  In a preferable aspect of the nonaqueous electrolyte secondary battery disclosed herein, the positive electrode active material layer further includes a conductive material and a binder, and the granular polymer B and the conductive material are uniformly dispersed. According to such a configuration, even when the granular polymer B exhibiting insulating properties is contained in the positive electrode active material layer, it is possible to suppress a decrease in internal resistance of the positive electrode because it is uniformly dispersed with the conductive material. Further, at the time of shutdown, the particulate polymer B is melted and covered with a conductive material, so that the conductive path is easily cut off, and the effect of increasing the internal resistance can be enhanced. The positive electrode active material layer having such a structure is obtained by, for example, dispersing a composition prepared by dispersing the positive electrode active material after dispersing the granular polymer B, the conductive material, and the binder in a predetermined solvent. It can be formed by feeding on the body.

  In addition, although it is completely different from the present invention, in Patent Document 3 described above, as a conventional technique, after kneading a conductive agent, a binder, and a solvent, an active material is added and kneaded. A method for preparing a paste containing an active material is disclosed. However, Patent Document 3 points out that according to this method, the kneading state, viscosity, and the like of the paste cannot be stabilized because the kneading is performed without applying a shearing force. In the present invention, such a method can be suitably applied as a means for realizing uniform dispersion of the granular polymer B and the conductive material.

  In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the granular polymer A is contained in a proportion of 10% by mass to 40% by mass with the total amount of the inorganic filler and the granular polymer A being 100% by mass. Can be. The granular polymer B may be included in a proportion of 3% by mass to 10% by mass with the total amount of the positive electrode active material and the granular polymer B being 100% by mass. By blending the granular polymer A and / or the granular polymer B at such a ratio, a shutdown function can be provided without excessively deteriorating battery characteristics.

  In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the porosity of the heat-resistant layer is 30% or more and 70% or less. By setting it as this structure, while a heat resistant layer can fully ensure the ion conductivity between a positive electrode and a negative electrode, it can increase resistance effectively at the time of shutdown.

  By applying the above configuration to a secondary battery having high energy density and high rate characteristics, the effect can be better exhibited. Therefore, as the nonaqueous electrolyte secondary battery disclosed herein, for example, a lithium secondary battery including a lithium transition metal composite oxide as a positive electrode active material is preferable. Further, such a non-aqueous electrolyte secondary battery is suitable as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) that requires input / output characteristics at a high rate, and the present invention is disclosed herein. A vehicle (for example, an automobile) provided with the nonaqueous electrolyte secondary battery.

  Furthermore, the non-aqueous electrolyte secondary battery manufacturing method disclosed herein is a method for manufacturing a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. This manufacturing method prepares a composition for forming a heat-resistant layer containing an inorganic filler, a granular polymer A having a melting point in a temperature range of 80 ° C. or higher and 100 ° C. or lower, and a binder, and at least a separator substrate made of a thermoplastic resin. Preparing a separator having a heat-resistant layer formed by supplying to one surface, a positive electrode active material, a conductive material, and a granular polymer having a melting point in the temperature range of 120 ° C. or less exceeding the melting point of the granular polymer A A positive electrode active material layer forming composition containing B and a binder is formed, and the positive electrode active material layer forming composition is supplied to at least one surface of a positive electrode current collector to form a positive electrode active material layer Preparing a prepared positive electrode, preparing a composition for forming a negative electrode active material layer containing a negative electrode active material and a binder, and supplying the composition to at least one surface of the negative electrode current collector It encompasses but providing a negative electrode formed, and the positive electrode, and the negative electrode, and the separator, to construct a nonaqueous electrolyte secondary battery using a non-aqueous electrolyte, a.

  According to this manufacturing method, it is possible to provide a non-aqueous electrolyte secondary battery including granular polymers A and B functioning as a so-called shutdown resin divided into two members, a heat-resistant layer of a separator and a positive electrode active material layer. That is, it is possible to manufacture a non-aqueous electrolyte secondary battery that can more safely and surely suppress an increase in battery temperature during abnormal heat generation.

  Preferably, the positive electrode active material layer forming composition is prepared by dispersing the conductive material, the granular polymer B, and the binder in a predetermined solvent, and then dispersing the positive electrode active material in the dispersion. To do. According to such a configuration, the conductive material having a smaller particle diameter than the positive electrode active material and the granular polymer B are generally uniformly dispersed, and then the positive electrode active material having a relatively large particle diameter is mixed. Highly uniform positive electrode active material layer forming composition (typically prepared in the form of a slurry or paste). By using such a composition, it is possible to form a positive electrode active material layer in which the granular polymer B is less unevenly distributed and uniformly dispersed. In other words, the positive electrode active material layer formed by such a manufacturing method includes an insulating polymer, but has a low decrease in conductivity.

  In a preferred embodiment of the method for producing a nonaqueous electrolyte secondary battery disclosed herein, the granular polymer A is in a proportion of 10% by mass to 40% by mass with respect to the total amount of the inorganic filler and the granular polymer A. A heat-resistant layer-forming composition is prepared by blending. And the said granular polymer B is mix | blended in the ratio of 3 mass%-10 mass% with respect to the total amount of the said positive electrode active material and the said granular polymer B, and the composition for positive electrode active material layer formation is prepared. Further, the porosity of the heat-resistant layer is set to 30% or more and 70% or less. According to this configuration, the shutdown function can be more effectively exhibited in each of the heat-resistant layer and the positive electrode active material layer without excessively degrading the battery characteristics.

  In a preferred embodiment of the method for producing a nonaqueous electrolyte secondary battery disclosed herein, a lithium secondary battery is constructed using a lithium transition metal composite oxide as the positive electrode active material. With this configuration, lithium secondary batteries that can achieve high input / output density and high energy density are manufactured with shutdown performance that can more reliably and safely prevent abnormal battery heat generation while maintaining the battery performance. can do.

FIG. 1 is a perspective view schematically showing the outer shape of a lithium secondary battery according to an embodiment. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a schematic diagram showing a wound electrode body according to an embodiment. FIG. 4 is a partial cross-sectional view showing a structure of a wound electrode body according to an embodiment. FIG. 5 is a diagram showing a change in internal resistance with temperature of the lithium ion battery. FIG. 6 is a side view showing a vehicle equipped with a lithium ion battery according to an embodiment of the present invention. FIG. 7 is a graph showing changes in voltage and temperature during overcharging of a lithium ion battery according to an embodiment.

In the present specification, the “secondary battery” refers to a battery that can be repeatedly charged, such as a lithium secondary battery or a nickel metal hydride battery. In the present specification, the “lithium secondary battery” refers to a battery that can be repeatedly charged using lithium ions as a charge carrier, and typically includes lithium ion batteries, lithium polymer batteries, and the like.
Further, in this specification, the “active material” can reversibly occlude and release (typically insertion and removal) chemical species (for example, lithium ions in a lithium secondary battery) that become charge carriers in the secondary battery. Refers to a substance.

  The characteristics of the nonaqueous electrolyte secondary battery according to the present invention will be described based on one structural example. Hereinafter, in the drawings, members / parts having the same action are described with the same reference numerals. In addition, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship, except for matters specifically mentioned. Further, matters other than matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, materials and manufacturing methods such as active materials, separators and electrolytes, construction of non-aqueous electrolyte secondary batteries) Can be grasped as a design matter of those skilled in the art based on the prior art in this field.

  The nonaqueous electrolyte secondary battery disclosed herein includes, as an essential component, a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and a thermoplastic resin interposed between the positive electrode and the negative electrode. A separator made of resin and a non-aqueous electrolyte are provided. This separator typically has a base portion made of a porous sheet-like polyolefin resin, and can exhibit a shutdown function that cuts off current by being softened or melted. In addition, the separator includes a heat resistance layer (HRL) on at least one surface. The heat resistant layer is a porous functional layer containing an inorganic filler having heat resistance. This heat-resistant layer imparts heat resistance to the separator for the purpose of preventing internal short-circuiting of the separator due to the mixing of metal foreign substances and the accompanying oxidative decomposition and deterioration of battery characteristics.

  However, the above-mentioned sheet-like polyolefin resin has a relatively high melting point of about 130 ° C. or higher due to its production method (for example, uniaxial stretching). For this reason, a general battery can be melted during abnormal heat generation to rapidly increase the internal resistance of the battery and cut off the current. However, for example, a large battery having a high energy density characteristic has a lower heat dissipation than a general battery because of its structure, and tends to accumulate heat in the center of the battery. For this reason, in the case of abnormal heat generation due to overcharge or the like, there is a possibility that the temperature of the battery will continue to increase at an accelerated rate even if the separator (base body) melts and the current is once interrupted (shut down).

  Therefore, the nonaqueous electrolyte secondary battery disclosed herein includes a granular polymer A having a melting point in the temperature range of 80 ° C. or higher and 100 ° C. or lower in the heat-resistant layer, and exceeds 120 ° C. below the melting point of the granular polymer A. A granular polymer B having a melting point in the temperature range is included in the positive electrode active material layer.

  The granular polymers A and B are insulating polymers and usually have a shape close to a sphere (having a smaller surface area). And it melts | melts at temperature more than each melting | fusing point, increases the surface area, interrupts | blocks an ion conduction path, and increases the internal resistance of a battery. That is, the granular polymers A and B function as a so-called shutdown resin. That is, in such a nonaqueous electrolyte secondary battery, the positive electrode active material layer and the heat-resistant layer of the separator have a shutdown function in addition to the base of the separator.

  The heat-resistant layer is generally thin with a thickness of less than about 10 μm, typically about 1 to 7 μm. Therefore, even if the blending amount of the granular polymer A is relatively small, the granular polymer A can be uniformly dispersed and arranged in the layer at a high blending ratio. Therefore, for example, a shutdown resistor can be formed quickly when abnormal heat is generated, and a denser and less severed resistor can be formed after shutdown. In other words, the granular polymer A can be melted to form a resistor having a more layered form, and the internal resistance of the battery can be efficiently increased.

  Also, in general, abnormal heat generation due to overcharging occurs at the negative electrode or the positive electrode, and the heat generation can propagate to the separator. Therefore, considering the position of the member where the temperature starts to rise in the battery and the timing thereof, it is desirable to provide a shutdown function by combining the separator and the positive electrode among the members constituting the battery.

  Granular polymer A melting | fusing point is prescribed | regulated to the temperature range of 80 to 100 degreeC. The reason why the melting point of the granular polymer A is 80 ° C. or higher is that when the temperature of the heat-resistant layer is 80 ° C. or higher, it can be determined that abnormal heat generation has occurred in the nonaqueous electrolyte secondary battery. The reason why the melting point of the granular polymer A is 100 ° C. or less is that it is desirable to reliably shut down the heat-resistant layer when the temperature of the heat-resistant layer is as low as possible after abnormal heat generation occurs. The suppression of the current at an early stage in the heat-resistant layer is extremely effective for controlling the subsequent heat generation behavior.

  The melting point of the granular polymer B is specified to be higher than the melting point of the granular polymer A and within a temperature range of 120 ° C. or less. The positive electrode active material layer containing the granular polymer B is often at a higher temperature than the separator due to a battery chemical reaction even during normal use, and further rises in temperature because the temperature rises faster than the separator during overcharge. Therefore, it is desirable that the melting point of the granular polymer B is higher than the melting point of the granular polymer A. The reason why the melting point of the granular polymer B is set to 120 ° C. or less is that the shutdown function by the granular polymer B is manifested at an earlier stage than the shutdown by the separator substrate.

  In such a non-aqueous electrolyte secondary battery, these granular polymers A and B are dispersed and included in the positive electrode active material layer and the heat-resistant layer of the separator as described above. Therefore, more granular polymer can be included in the nonaqueous electrolyte secondary battery as a whole without significantly impairing battery characteristics during normal energization. In addition, the granular polymers A and B are arranged on two members in the non-aqueous electrolyte secondary battery, so that they can be shut down in stages at a more appropriate timing according to the temperature distribution in the battery and the temperature change behavior. Function can be expressed.

  In addition, since these granular polymers A and B are insulative, if any one of the above is included in an amount sufficient for shutdown during abnormal heat generation due to overcharge or the like, battery characteristics during normal use ( For example, battery capacity, internal resistance, etc.) will be greatly impaired. On the contrary, if it is included in any one of the above members without greatly impairing the battery characteristics during normal operation, the amount that can be blended is limited to a small amount. This is a particularly prominent problem when the battery is a large battery with poor heat dissipation, but the nonaqueous electrolyte secondary battery disclosed herein solves this problem by the above configuration. .

FIG. 5 is a conceptual diagram illustrating an example of the shutdown behavior of such a nonaqueous electrolyte secondary battery. The horizontal axis indicates the temperature inside the battery, and the vertical axis indicates the internal resistance of the battery. Plot (1) in the figure shows the change in internal resistance with temperature of the non-aqueous electrolyte secondary battery disclosed herein, and plot (2) shows non-aqueous electrolyte 2 not containing granular polymers A and B. It is a mode of the change of the internal resistance regarding the secondary battery.
As described above, the internal resistance of the battery including the granular polymers A and B changes, for example, as shown in the plot (1). That is, when abnormal heat generation starts and the temperature inside the battery reaches the melting point of the granular polymer A (indicated by an arrow near 100 ° C. in FIG. 5), the shutdown function due to the granular polymer A contained in the heat-resistant layer of the separator appears. This increases the internal resistance of the battery. Thereby, an electric current is suppressed at an earlier stage. Furthermore, when the temperature inside the battery rises and reaches the melting point of granular polymer B contained in the positive electrode active material layer (indicated by an arrow near 110 ° C. in FIG. 5), the shutdown function by granular polymer B appears. This further increases the internal resistance of the battery and further suppresses the current. Thereafter, when the temperature of the battery further rises and reaches the melting point of the sheet-like polyolefin constituting the separator substrate (indicated by an arrow near 130 ° C. in FIG. 5), the shutdown function by the sheet-like polyolefin is achieved. And the internal resistance of the battery is significantly increased, and the current is completely cut off. Even if the temperature of the battery reaches, for example, 130 ° C. or more at this time, the battery gradually increases its internal resistance from the early stage and the current is suppressed. Therefore, when the electrochemical reaction stops, the temperature of the battery gradually decreases. To do.

  On the other hand, the battery that does not contain the granular polymer shown in plot (2) does not increase its internal resistance until it reaches the melting point of the sheet-like polyolefin even if abnormal heating starts, and shuts down for the first time at the melting point of this sheet-like polyolefin. The function is developed and the internal resistance of the battery is remarkably increased. Here, in the case of abnormal heat generation of a general consumer battery, when the battery current is cut off, the battery temperature gradually decreases as shown in plot (2) after a while. However, if it has a structure that easily accumulates heat, such as a large battery, heat is accumulated in the battery (particularly in the center) as the battery temperature rises, and the temperature of the battery is a sheet-like polyolefin. At the time when the melting point of the battery is reached, the temperature of the battery can rise at an accelerated speed. In such a state, even after the current is cut off, the rapid temperature rise of the battery continues, and it is considered that the battery temperature rises to, for example, 250 ° C. or higher, and more than 300 ° C. Therefore, it is extremely important to suppress the current by increasing the internal resistance of the battery from an early stage before reaching an accelerating temperature rise in order not to induce an accelerating temperature rise.

  The non-aqueous electrolyte secondary battery disclosed herein is effective in increasing the internal temperature of the battery in stages from an early stage after the occurrence of abnormal heat generation as described above. I try to suppress it. That is, such a non-aqueous electrolyte secondary battery is provided as a system that can control the propagation form of heat generation in the battery more systematically and positively, and can suppress abnormal heat generation during overcharge more safely and reliably. .

Hereinafter, the configuration and manufacturing method of the nonaqueous electrolyte secondary battery of the present invention will be described in more detail with reference to FIGS. 1 to 4 as appropriate, taking a lithium ion battery as an embodiment as an example.
FIG. 1 is a perspective view showing the appearance of the lithium ion battery 10. 2 is a cross-sectional view taken along the line II-II in FIG. As shown in FIG. 2, the lithium ion battery 10 includes a wound electrode body 20 and a battery case 80. FIG. 3 is a diagram showing a configuration of the wound electrode body 20. FIG. 4 is a cross-sectional view showing the structure of the wound electrode body 20.

3 and 4, the wound electrode body 20 includes a strip-shaped positive electrode (hereinafter also referred to as a positive electrode sheet) 30, a strip-shaped negative electrode (hereinafter also referred to as a negative electrode sheet) 50, and a separator 70. It is comprised by winding up.
≪Positive electrode≫
As described above, the positive electrode (positive electrode sheet) 30 includes the positive electrode active material layer 34 on the strip-shaped positive electrode current collector 32. The positive electrode active material layer 34 includes the granular polymer B38 together with the positive electrode active material. Such a positive electrode 30 typically includes a positive electrode active material layer, a conductive material, a particulate polymer B38, and a binder dispersed in an appropriate solvent or vehicle to form a paste-like (slurry) positive electrode active material layer. It can be formed by preparing a composition for use, supplying it to at least one surface of the positive electrode current collector 32, drying it, and rolling it.

  As the positive electrode current collector 32, a metal foil suitable for the positive electrode 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, for example, a strip-shaped aluminum foil having a predetermined width and a thickness of approximately 1 μm is used as 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 and a granular polymer B38. In this embodiment, the positive electrode active material layer 34 is mainly composed of a granular positive electrode active material, and also includes a granular polymer B38 and a conductive material for enhancing conductivity, and these are combined with the positive electrode current collector by a binder. 32 is fixed. In such a positive electrode active material layer 34, voids are formed between the positive electrode active material particles so that the electrolyte solution can permeate therethrough.

As the positive electrode active material, one or more of various materials that can be used as the positive electrode active material of the lithium ion battery 10 can be used. Specifically, as the positive electrode active material, a material capable of inserting and extracting lithium can be used without any particular limitation. As such a positive electrode active material, a lithium transition metal oxide (typically in particulate form) is preferably used. Typically, 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, the “lithium nickel 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, other than Li and Ni). A composite containing transition metal element and / or typical metal element) in a proportion smaller than Ni (in terms of the number of atoms; in the case where two or more metal elements other than Li and Ni are contained, both of them are less proportion than Ni) It is meant to include oxides. 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.

Other general formulas:
_{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)
A so-called ternary system containing three kinds of transition metal elements as represented by the 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. By using, for example, 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.

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 an anion 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. As such a positive electrode active material, those having an average particle diameter of about 1 μm to 50 μm, typically about 1 μm to 25 μm, preferably 2 μm to 20 μm, for example, 3 μm to 8 μm can be preferably used.

The “average particle size” disclosed herein may be indicated by a particle size distribution at a 50% integrated value in a particle size distribution determined on a volume basis (hereinafter simply referred to as an average particle size or D ₅₀ ) by a laser diffraction scattering method. .)

The granular polymer B38 can be used without particular limitation as long as it is a granular polymer having a melting point in the temperature range of 120 ° C. or less exceeding the melting point of granular polymer A78 described later. The granular polymer B38 melts when the temperature of the positive electrode active material layer 34 reaches the melting point, and increases the surface area to cover the conductive material, and closes the conductive path. This increases the internal resistance of the positive electrode active material layer 34, restricts the movement of charge carriers, and restricts the reaction of the battery 10 (shutdown in the positive electrode active material layer 34).
As the granular polymer B38, for example, a resin having a desired melting point and various characteristics can be appropriately selected from polyolefin resins. As such a granular polymer B38, it is preferable to use one or more selected from polyethylene (PE) and an ethylene-vinyl monomer copolymer which are relatively easy to adjust the melting point and are easily available. Specific examples include polyethylene (PE), ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-acrylic acid copolymer, and the like. In general, the density varies depending on the molecular weight and molecular structure, and the melting point can be controlled to a desired temperature by adjusting the density.

In addition, such a granular polymer B38 can increase the internal resistance of the battery 10 during abnormal heat generation by being mixed in the positive electrode active material layer 34 even in a small amount, and the effect increases as the amount increases. However, when the total amount of the positive electrode active material and the granular polymer B38 is 100% by mass, it is difficult to effectively increase the internal resistance at the time of abnormal heat generation when the blending amount is less than 3% by mass. On the other hand, when the blending amount of the granular polymer B38 exceeds 10% by mass, the internal resistance when using a normal battery is increased and the battery capacity is also reduced, leading to unnecessarily impaired battery characteristics. Considering these matters, the blending amount of the granular polymer B38 in the positive electrode active material layer 34 is desirably about 3% by mass to 10% by mass, more preferably about 5% by mass to 8% by mass. Thereby, in the positive electrode active material layer 34, the shutdown function by the granular polymer B38 can be effectively expressed, and abnormal heat generation of the battery 10 can be suppressed from an earlier stage.
The average particle diameter (D ₅₀ ) of the granular polymer B38 is not particularly limited because it does not directly affect the battery characteristics. However, the average particle diameter (D ₅₀ ) of the granular polymer B38 is not limited to the positive electrode active material and the conductive material. From the viewpoint, for example, those in the range of about 0.1 μm to 3.0 μm, more preferably about 0.5 μm to 1.5 μm can be used.

  The conductive material has a role of securing a conductive path between the positive electrode active material having poor conductivity and the positive electrode current collector 32. As this 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. 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. The average particle diameter of the conductive material is not limited, but typically, a material having an average particle diameter of 1 μm or less, for example, 0.001 μm to 1 μm can be used more preferably.

  The binder serves to fix the positive electrode active material, the conductive material, and the particulate polymer B38 to form the positive electrode active material layer 34 and to fix the positive electrode active material layer 34 on the positive electrode current collector 32. As such a 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 employed. The melting points of these polymer materials are essentially set higher than the melting point of the granular polymer B38.

  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. Moreover, as a solvent of the composition for positive electrode active material layer formation, both 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.

In the positive electrode active material layer 34, it is desirable that the granular polymer B38 and the conductive material are uniformly dispersed. Since the granular polymer B38 exhibits insulating properties as described above, inclusion in the positive electrode active material layer 34 leads to an increase in the internal resistance of the battery 10. However, since the granular polymer B38 is uniformly dispersed with the conductive material having excellent conductivity, an increase in internal resistance due to the granular polymer B38 can be suppressed. In addition, when the granular polymer B38 is shut down, the granular polymer B38 and the conductive material are uniformly dispersed, so that when the granular polymer B38 is melted, the conductive path by the conductive material can be more effectively blocked. That is, the shutdown function of the granular polymer B38 can be effectively expressed.
Normally, the particle size of the conductive material is smaller than that of the granular polymer B38. Therefore, the conductive material may surround the granular polymer B38 and the positive electrode active material layer 34 as a whole may be uniformly dispersed. For example, it can be considered that a conductive material surrounds the surface of the granular polymer B38 and is uniformly dispersed in the positive electrode active material layer.

  Such a uniform dispersion state of the granular polymer B38 and the conductive material can be easily realized by, for example, appropriately preparing a positive electrode active material layer forming composition prepared when forming the positive electrode active material layer 34. can do. That is, first, the particulate polymer B38, the conductive material, and the binder are dispersed in a predetermined solvent, and then the positive electrode active material is dispersed in this mixture to prepare the positive electrode active material layer forming composition. Good. In preparing this composition, a dispersant may be used as necessary. Moreover, as a means of dispersion | distribution and mixing, various dispersers, an emulsifier, a kneader, a stirrer etc. can be used, for example. If the composition for positive electrode active material layer formation is prepared as mentioned above, others can manufacture a positive electrode, construction | assembly of a battery, etc. according to a conventional method. Thereby, even if it is a case where the granular polymer B38 which shows insulation is contained in the positive electrode active material layer 34, the fall of the internal resistance of the positive electrode 30 can be suppressed more than necessary. Further, at the time of shutdown, the particulate polymer B38 is melted and covered with a conductive material, so that the conductive path is easily cut off, and the effect of increasing the internal resistance can be enhanced.

  In addition, it is preferable that the mass ratio of the positive electrode active material to the whole positive electrode active material layer 34 is about 50 mass% or more (typically 50 mass% to 95 mass%), and usually about 70 mass% to 95 mass%. It is more preferable that it is mass% (for example, 75 mass%-90 mass%). And the mass ratio of granular polymer B38 to the total amount of positive electrode active material and granular polymer B38 shall be about 3 mass%-10 mass%. The proportion of the conductive material in the entire positive electrode active material layer 34 is, for example, a balance between the positive electrode active material and the granular polymer B38, but can be about 2% by mass to 20% by mass. Is preferably about 2% by mass to 15% by mass. In the composition using the binder, for example, the ratio of the binder in the positive electrode active material layer 34 can be set to, for example, approximately 1% by mass to 10% by mass, and usually approximately 2% by mass to 5% by mass. It is preferable to adjust the blending.

≪Negative electrode≫
The negative electrode (negative electrode sheet) 50 includes a negative electrode active material layer 54 containing a negative electrode active material on a strip-shaped negative electrode current collector 52. Typically, the negative electrode 50 is prepared by dispersing a negative electrode active material and a binder in a suitable solvent or vehicle to prepare a paste-form (slurry) negative electrode active material layer forming composition. It can be formed by supplying to at least one surface of the electric body 52, drying, and rolling.

  As the negative electrode current collector 52, a metal foil used for the negative electrode 50 of the lithium ion battery 10 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 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, the negative electrode active material is, for example, natural graphite, natural graphite coated with an amorphous carbon material, graphite (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon ( Soft carbon) or a carbon material combining these may be used. Further, for example, a metal compound (preferably silicide or metal oxide) having Si, Ge, Sn, Pb, Al, Ga, In, As, Sb, Bi, or the like as a constituent metal element may be used. Moreover, 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 content rate of the following conductive material may be reduced as compared with the conventional case. 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.

  In the case of using an insulating material or a material with low conductivity as the negative electrode active material, for example, a conductive intermediate layer (not shown) is provided between the negative electrode current collector 52 and the negative electrode active material layer 54. Can be arranged. Although not particularly limited, the negative electrode active material layer 54 may contain a conductive material. The conductive material has a role 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 of the positive electrode active material layer 34 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, the usage-amount of a electrically conductive material can 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. 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.

≪Separator≫
As shown in FIGS. 2 to 4, the separator 70 is a member that insulates the positive electrode sheet 30 and the negative electrode sheet 50 and allows the electrolyte to move. As long as this requirement is satisfied, the material constituting the base of the separator 70 is not essentially limited. And as such a separator 70, the various separators which consist of a thermoplastic resin similar to what is used for the conventional lithium ion battery can be used. Typically, a porous body, a nonwoven fabric, a cloth, or the like having fine pores that can move lithium ions can be used. For example, a porous sheet (microporous resin sheet) made of a thermoplastic resin can be preferably used. As a constituent material of such a porous sheet, polyolefin resins such as polyethylene (PE), polypropylene (PP), and polystyrene are preferable. In particular, a porous structure such as a PE sheet, a PP sheet, a two-layer structure sheet in which a PE layer and a PP layer are laminated, and a three-layer structure sheet in which one PE layer is sandwiched between two PP layers. A polyolefin sheet can be suitably used.

In the example shown in FIG. 4, the separator 70 includes a heat resistant layer 72 on one surface. The thickness of the heat-resistant layer 72 is not particularly limited, but can be approximately 10 μm or less, typically 0.5 μm to 7 μm, and more specifically about 2 μm to 6 μm. The heat-resistant layer 72 includes an inorganic filler, a granular polymer A78 having a melting point in a temperature range of 80 ° C. or higher and 100 ° C. or lower, and a binder.
The separator 70 having such a heat-resistant layer 72 is typically prepared by preparing a composition for forming a heat-resistant layer containing an inorganic filler, a granular polymer A, and a binder, and at least one surface of the substrate of the separator. It can be prepared by supplying to.

As the inorganic filler, various insulating 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, alumina (Al ₂ O ₃ ), boehmite (Al ₂ O ₃ .H ₂ O), magnesia (MgO), etc., which are stable in quality and inexpensive and easily available, are used. Is preferred.

  The granular polymer A78 contained in the heat-resistant layer 72 of the separator 70 can be used without particular limitation as long as it is a granular polymer having a melting point in the temperature range of 80 ° C. or higher and 120 ° C. or lower. The granular polymer A78 melts when the temperature of the heat-resistant layer 72 provided on the surface of the separator 70 becomes higher than the melting point of the granular polymer A78, and increases the surface area, thereby forming pores in the heat-resistant layer 72 and the separator 70. Fill to block the conductive path. This increases the internal resistance of the heat-resistant layer 72 and the separator 70, restricts the movement of the charge carriers (electrolyte movement), and restricts the reaction of the battery 10 (shutdown in the heat-resistant layer 72).

  As this granular polymer A78, it can select from the thing similar to granular polymer B38 in said positive electrode active material layer 34 suitably, and can use it. The granular polymer A78 has a melting point different from that of the granular polymer B38 contained in the positive electrode active material layer 34 and has a lower melting point than the granular polymer B38. If this point is satisfied, the granular polymer A78 may have the same composition as the granular polymer B38, or may be a completely different material.

  The granular polymer A78 is preferably contained in the heat-resistant layer 72 at a ratio of 10% by mass to 40% by mass with the total amount of the inorganic filler and the granular polymer A78 being 100% by mass. The particulate polymer A78 exhibits an effect of increasing the internal resistance of the battery 10 when abnormal heat is generated by being contained in the heat-resistant layer 72 even if only a small amount, and the effect increases as the amount increases. However, if the blending amount is less than 10% by mass, it is difficult to effectively increase the internal resistance during abnormal heat generation. On the other hand, when the blending amount of the granular polymer A78 exceeds 40% by mass, the internal resistance when using the normal battery 10 is increased, and the battery characteristics are unnecessarily impaired. Considering these matters, the blending amount of the granular polymer A78 in the heat-resistant layer 72 is desirably about 10% by mass to 40% by mass, more preferably about 20% by mass to 30% by mass. Thereby, the shutdown function by the granular polymer B78 is effectively expressed in the heat-resistant layer 72, and abnormal heat generation of the battery 10 can be stopped at an earlier stage.

  The average particle size of the inorganic filler contained in the heat-resistant layer 72 is preferably 0.5 μm to 5.0 μm, and the average particle size of the granular polymer A78 is preferably 0.1 μm to 3.0 μm. . By setting the average particle size of the inorganic filler to 0.5 μm to 5.0 μm, as the heat resistant layer 72, the effect of preventing the oxidative decomposition of the separator 70 and the deterioration of the battery characteristics can be further enhanced. Moreover, the reactivity with respect to the time of the abnormal heat_generation | fever of the granular polymer A can be improved by making the average particle diameter of the granular polymer A 0.1 micrometer-3.0 micrometers, and quicker fusion | melting is realizable. And the dispersion state of the inorganic filler and the granular polymer A in a heat-resistant layer can be maintained in a more uniform and non-uniform state, and a good heat-resistant layer 72 can be realized.

  Furthermore, in the lithium ion battery 10, the heat-resistant layer 72 preferably has a porosity of 30% or more and 70% or less. Since the heat-resistant layer 72 is provided on the surface of the separator 70, it is necessary to have pores for securing ion conductivity between the positive electrode 30 and the negative electrode 50 together with the separator 70. Therefore, the porosity of the heat-resistant layer 72 is preferably 30% or more in order to secure ion conductivity and reduce the generation of resistance. Moreover, in order to maintain the strength and resistance as the heat-resistant layer 72 and to exhibit the effect of increasing the resistance at the time of shutdown, it is preferably 70% or less. For example, it is more preferably about 40% or more and 60% or less. This porosity can be suitably controlled by adjusting the method for forming the heat-resistant layer 72, the blending of the inorganic filler and the granular polymer A78 included in the heat-resistant layer 72, and the like.

The heat-resistant layer 72 is prepared, for example, by preparing a paste-like (slurry) composition in which the above-described inorganic filler and granular polymer A78 are mixed with a solvent or vehicle together with a binder, and this is applied to the separator 70 and dried. Can be formed. At this time, the same binder as described for the positive electrode active material layer 34 can be used as the binder. As the solvent for the composition for forming the heat-resistant layer, both an aqueous solvent and a non-aqueous solvent can be used as in the case of the composition for forming the positive electrode active material layer 34. The polymer material that can be used 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.
Although not particularly limited, the blending ratio of the total of the inorganic filler and the granular polymer A78 and the binder can be, for example, 90:10 to 99: 1 in terms of mass ratio (NV basis), 93 : 7 to 97: 3 is preferred, and 93: 7 to 95: 5 is more preferred. 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 is typically about 40% by weight for solvent-based materials and 50% to 52% by weight for water-based materials. However, it goes without saying that the solid content is not limited to the above numerical values.

  As described above, the amount of the granular polymer A78 and the granular polymer B38 that can be blended without excessively degrading the battery characteristics of the lithium ion battery 10 is limited. In the lithium ion battery 10, as described above, the granular polymer A 78 is mixed in the heat-resistant layer 72 of the separator, and the granular polymer B 38 is mixed in a proper amount in the positive electrode active material layer 34. According to this, the usage amount of the granular polymer A78 and the granular polymer B38 can be increased to the maximum amount that does not cause deterioration of the battery 10 characteristics, and the shutdown effect by the granular polymer A78 and the granular polymer B38 is maximized. Therefore, thermal runaway during abnormal heat generation can be more reliably prevented.

  On the other hand, for example, if the shutdown is performed only on the base of the separator 70 and the heat-resistant layer 72 or only on the base of the separator 70 and the positive electrode active material layer 34, for example, thermal runaway due to abnormal heat generation of a large battery is completely prevented. It can be difficult to suppress. That is, if sufficient granular polymer A capable of suppressing thermal runaway due to abnormal heat generation of a large battery is to be blended only in the base of separator 70 and heat-resistant layer 72, or in base of separator 70 and positive electrode active material layer 34, battery design Cause trouble. Therefore, in such a lithium ion battery 10, an appropriate amount of the granular polymer A78 and the granular polymer B38 can be blended at an appropriate location (member) in the battery 10 in an appropriate form.

  2 to 4, the width b <b> 1 of the negative electrode active material layer 54 is slightly wider than the width a <b> 1 of the positive electrode active material layer 34. The widths c1 and c2 of the separator 70 are slightly wider than the width b1 of the negative electrode active material layer 54 (c1, c2> b1> a1). The separator 70 includes a heat-resistant layer containing an inorganic filler on at least one surface. The porosity of the entire separator including the heat-resistant layer is, for example, preferably 30% to 70% (more preferably 40% to 60%). In the lithium ion battery 10 disclosed herein, when a solid electrolyte or a gel electrolyte is used as an electrolyte, a separator is unnecessary (that is, in this case, the electrolyte itself can function as a separator). possible.

≪Battery case≫
In this example, as shown in FIG. 1, the battery case 80 is a so-called square battery case, and includes a container body 84 and a lid 82. The container main body 84 has a bottomed rectangular tube shape and is a flat box-shaped container having one side surface (upper surface) 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 pass through the battery case 80 (lid 82) and come out of the battery case 80. The lid 82 is provided with a safety valve 88.

The wound electrode body 20 includes a belt-like positive electrode sheet 30, a negative electrode sheet 50, and a separator 70.
In producing the wound electrode body 20, the positive electrode sheet 30 and the negative electrode sheet 50 are laminated via the separator 70. At this time, 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 of the separator 70 in the width direction. The sheet 30 and the negative electrode sheet 50 are overlapped with a slight shift in the width direction. The laminated body thus stacked is wound, and then the obtained wound body is crushed from the side surface direction and ablated to produce the flat wound electrode body 20.

  In the central portion of the wound electrode body 20 in the winding axis (WL) direction, there are wound core portions (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 70, Are densely stacked). 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. A positive electrode lead terminal 41 and a negative electrode lead terminal 61 are attached to the protruding portion (that is, the portion where the positive electrode active material layer 34 is not formed) and the negative electrode side protruding portion (that is, the portion where the negative electrode active material layer 54 is not formed), respectively. Are electrically connected to the positive electrode terminal 40 and the negative electrode terminal 60, respectively. At this time, for example, ultrasonic welding is used to connect the positive electrode terminal 40 and the positive electrode current collector 32 due to the difference in the materials. For example, resistance welding is used for welding the negative electrode terminal 60 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 is closed 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).

≪Electrolytic solution≫
Thereafter, an electrolytic solution is injected into the battery case 80 from a liquid injection hole 86 provided in the lid 82. As the electrolytic solution used here, one kind or two or more kinds similar to the nonaqueous electrolytic solution used in the conventional lithium secondary battery can be used without any particular limitation. Such a non-aqueous electrolyte typically has a composition in which an electrolyte (that is, a lithium salt) is contained in a suitable non-aqueous solvent. The electrolyte concentration is not particularly limited, but a nonaqueous electrolytic solution containing an electrolyte at a concentration of about 0.1 mol / L to 5 mol / L (preferably about 0.8 mol / L to 1.5 mol / L) is preferably used. be able to. 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) and the like are exemplified.
Examples of the electrolyte include 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.

  As an overcharge inhibitor contained in the electrolyte, the oxidation potential is not less than the operating voltage of the lithium secondary battery (for example, 4.2 V or more in the case of a lithium secondary battery that is fully charged at 4.2 V). Any compound that generates a large amount of gas when oxidized can be used without any particular limitation. However, if the oxidation potential is close to the operating voltage of the battery, a local voltage increase occurs even at a normal operating voltage. There is a risk of gradually decomposing. On the other hand, when the decomposition voltage is 4.9 V or more, there is a possibility that thermal runaway may occur due to the reaction of the main component of the non-aqueous electrolyte and the electrode material before gas generation due to oxidative decomposition of the additive. Accordingly, 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 or more and 4.9 V or less. 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. The amount of the overcharge inhibitor used relative to 100% by mass of the electrolyte used can be, 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.

≪Cavity≫
Here, the positive electrode active material layer 34 and the negative electrode active material layer 54 have minute gaps that should be referred to as cavities, for example, between the particles of the electrode active material and the conductive material. An electrolytic solution (not shown) can penetrate into such a minute gap. Here, such a gap (cavity) is appropriately referred to as a “gap”. Thus, in the lithium ion battery 10, the positive electrode active material layer 34 and the negative electrode active material layer 54 are infiltrated with the electrolytic solution.

≪Gas escape route≫
In this example, the flat internal space of the battery case 80 is slightly wider than the wound electrode body 20 deformed flat. On both sides of the wound electrode body 20, a gap 85 is provided between the wound electrode body 20 and the battery case 80. The gap 85 becomes a gas escape path. For example, in the case where overcharge occurs, when the temperature of the lithium ion battery 10 becomes abnormally high, the electrolyte may be decomposed and gas may be generated abnormally. In this embodiment, the abnormally generated gas is smoothly exhausted out of the battery case 80 through the gap 85 between the wound electrode body 20 and the battery case 80 on both sides of the wound electrode body 20 and the safety valve 88. The

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

  In the nonaqueous electrolyte secondary battery disclosed herein, the granular polymer A78 and the granular polymer B38, which are shutdown resins, are dispersed in the heat-resistant layer 72 and the positive electrode active material layer 34 of the separator 70, respectively. is important. With such a configuration, for example, in a non-aqueous electrolyte secondary battery having a high energy density characteristic that is inferior in heat dissipation than a general battery, even if abnormal heat generation due to overcharge or the like occurs, the granular material included in the heat-resistant layer 72 of the separator 70 The polymer A78 is melted to increase the internal resistance of the battery from an early stage, and then the granular polymer B38 contained in the positive electrode active material layer 34 is melted to prevent heat generation and thermal runaway. . Further, by dispersing and blending the granular polymer A78 and the granular polymer B38 in a plurality of members, the shutdown function is effectively expressed without excessively degrading the battery characteristics. Furthermore, in the positive electrode active material layer 34, since the granular polymer B38 and the conductive material are uniformly dispersed, the shutdown performance is improved while suppressing the deterioration of the battery characteristics.

  The configuration as described above can be preferably applied to the lithium ion battery 10 which has a high energy density and can be used at a high rate, and can effectively exhibit the effect. In particular, the present invention can be suitably applied to a battery pack 100 in which heat dissipation tends to be delayed by connecting a plurality of lithium ion batteries 10. That is, the non-aqueous electrolyte secondary battery disclosed herein has high safety and reliability during abnormal heat generation as described above. For example, as shown in FIG. 6, a hybrid vehicle, a plug-in hybrid vehicle, or the like It can be used as a power source for the vehicle 1. For example, the vehicle 1 provided with the lithium ion battery 10 (which may be in the form of the assembled battery 100) is suitably provided.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not intended to be limited to those shown in the examples.
<Sample 1>

[Positive electrode]
In preparing the composition for forming the positive electrode active material layer, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as the positive electrode active material, AB (acetylene black) as the conductive material, and PVdF as the binder And polyethylene particles (average particle size 0.8 μm, melting point 100 ° C.) as the granular polymer B, when the mass ratio of these materials is represented by positive electrode active material: conductive material: binder: granular polymer B: 100: Prepared to be 5: 5: 6. When the total amount of the positive electrode active material and the granular polymer B is 100% by mass, the ratio of the granular polymer B is about 5.7% by mass.
First, the prepared conductive material, binder and granular polymer B were dispersed in N-methyl-2-pyrrolidone (NMP) as a solvent. For the dispersion of these solid content materials, stirring was performed for 25 minutes at a rotational speed of 20000 rpm using an ultra-precision dispersion emulsifier (manufactured by MTechnic Co., Ltd., CLEARMIX).
Next, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material was dispersed in the dispersion in the same manner as described above to prepare a composition for forming a positive electrode active material layer.

  The prepared composition was applied to both surfaces of a 15 μm thick Al foil as a current collector, dried, and then pressed to a total thickness of 170 μm to produce a positive electrode (positive electrode sheet). The positive electrode is cut to a length of 4500 mm and used for battery assembly.

[Negative electrode]
For the negative electrode, graphite as a negative electrode active material and PVdF as a binder were blended so that the mass ratio represented by graphite: binder was 100: 7, and this was mixed with N-methyl-2-pyrrolidone as a solvent. A composition for forming a negative electrode active material layer was prepared by dispersing in (NMP). This composition was applied to a Cu foil having a thickness of 20 μm as a current collector, dried, and then pressed so that the total thickness was 150 μm to produce a negative electrode. The negative electrode is cut to a length of 4700 mm and used for battery assembly.

[Separator]
Alumina (average particle size: 1.0 μm) as an inorganic filler, PVdF as a binder, and polyethylene particles (average particle size: 0.3 μm, melting point: 90 ° C.) as a granular polymer A have a mass ratio of these materials. Inorganic filler: binder: granular polymer A is blended so as to be 100: 4: 25, and this is dispersed in N-methyl-2-pyrrolidone (NMP) as a solvent to form a heat-resistant layer. A composition was prepared. When the total amount of the inorganic filler and the granular polymer A is 100% by mass, the ratio of the granular polymer A is 20% by mass.
As the separator, a microporous film made of polyethylene (PE) and having a thickness of 20 μm was used.
The heat-resistant layer paste was applied to one side of the separator using a gravure coater so as to have a thickness of 5.0 μm and dried to form a heat-resistant layer on the separator. Two sheets of this separator were prepared.

[Electrolytes]
In a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 3: 4: 3, LiPF ₆ as a supporting salt is contained at a concentration of about 1 mol / liter. Non-aqueous electrolyte was used.

[Construction of lithium-ion battery]
The positive electrode and the negative electrode were overlapped and wound through two separators, and then the wound body was crushed from the side surface to produce a flat wound electrode body. The wound electrode body thus obtained was housed in a metal box-type battery case together with the electrolytic solution, and the opening of the battery case was hermetically sealed to construct a lithium ion battery for evaluation.

<Sample 2>
When preparing the composition for forming a positive electrode active material layer, the positive electrode active material was mixed with other materials. Otherwise, a lithium ion battery was constructed in the same manner as Sample 1.

<Sample 3>
In the battery of Sample 1, a positive electrode was prepared without blending the granular polymer B in the positive electrode active material layer, and thereafter a lithium ion battery was constructed in the same manner.
That is, the positive electrode is prepared by blending the mass ratio of each material in the composition for forming a positive electrode active material layer, positive electrode active material: conductive material: binder: granular polymer B to be 100: 5: 5: 0, It used for construction of a battery.

<Sample 4>
In the battery of Sample 1, a separator was prepared without blending the granular polymer A in the heat-resistant layer, and thereafter a lithium ion battery was constructed in the same manner.
That is, a separator having a heat-resistant layer was prepared with a mass ratio of each material in the composition for forming a heat-resistant layer, inorganic filler: binder: granular polymer A being 100: 4: 0, and was used for battery construction.

<Sample 5>
In the battery of Sample 1, a positive electrode and a separator were prepared without blending the granular polymer B in both the positive electrode active material layer and the heat-resistant layer of the separator, and thereafter a lithium ion battery was constructed in the same manner.
That is, the positive electrode was produced by setting the mass ratio of each material in the positive electrode active material layer forming composition, positive electrode active material: conductive material: binder: granular polymer B to 100: 5: 5: 0.
Moreover, the mass ratio of each material in the paste for heat-resistant layers, the inorganic filler: binder: granular polymer A were blended so as to be 100: 4: 0, and a separator provided with a heat-resistant layer was produced.

[Continuous overcharge test]
Appropriate conditioning treatment for the evaluation lithium-ion batteries (samples 1 to 5) constructed above (up to charging at a constant current and a constant voltage up to 4.1 V at a charging rate of 1 C and up to 3.0 V at a discharging rate of 1 C) The operation of discharging at constant current and constant voltage was repeated three times (initial charge / discharge treatment).
Then, CC-CV charge was performed with respect to each battery adjusted to SOC30% to the charge upper limit voltage 20V at the rate of 48 A (equivalent to 2C) at room temperature (25 ° C.). At this time, a thermocouple was attached to the side surface of the battery case of each battery, the surface temperature of the battery case was measured, and the battery voltage was measured.
As a result, the temperature at which shutdown was started was recorded as the SD start temperature (° C.), and the highest temperature in the measurement results was recorded as the maximum attained temperature (° C.). In addition, the battery behavior was observed for at least 5 minutes after the shutdown due to the separator itself and energization became impossible. The results are shown in Table 1.

Further, FIG. 7 shows the time change of the voltage and the battery surface temperature in the continuous overcharge test of Sample 1.
As can be seen from Table 1, the battery of Sample 1, which is the invention disclosed herein, has the lowest SD start temperature of 88 ° C. as the surface temperature of the battery, and the lowest reached temperature of 120 ° C. as the highest temperature reached on the battery surface. It became. From FIG. 7, the battery gradually increases in temperature from the start of the test, begins to generate heat just before the voltage reaches 5 V, and after a while exceeds 5 V, the temperature increases greatly, and then the voltage rapidly increases and the surface of the battery The temperature reached 100 ° C or higher. The battery temperature then gradually increased to around 120 ° C. and then gradually decreased. Although there is a difference between the temperature at the center of the battery and the surface temperature, the shutdown timing could not be confirmed in detail, but by providing a shutdown function for both the positive electrode and the separator, first the melting point is lower A heat-resistant layer containing granular polymer A (melting point 90 ° C.) increases battery resistance at an early stage to suppress further overcharge and heat accumulation, and then a positive electrode active material layer further containing granular polymer B (melting point 100 ° C.) It is considered that the current was surely stopped by increasing the internal resistance step by step and finally increasing the resistance of the separator (melting point 130 ° C.) substrate rapidly. In the battery of Sample 1, abnormal heat generation was positively controlled from an early stage of heat generation, and the heat generation could be suppressed extremely safely.

  Moreover, the battery of Sample 2 which is the invention disclosed herein includes the same amount of the same granular polymer in the same member as Sample 1. Therefore, both the shutdown start temperature and the maximum temperature reached are lower than those of Samples 3 to 5, and the effect of suppressing the acceleration temperature rise is observed. However, because the dispersion state of the granular polymer B in the positive electrode active material layer can be biased, both the shutdown start temperature and the maximum temperature reached are higher than those of Sample 1. It was confirmed that Sample 1 having a better dispersion state of granular polymer B in the positive electrode active material layer can more effectively express the shutdown function of granular polymer B.

  On the other hand, the battery of Sample 3 has a shutdown function by the granular polymer A only in the heat-resistant layer. The shutdown by the heat-resistant layer started from the battery surface temperature of 98 ° C., which was higher than Samples 1 and 2. In particular, the maximum temperature reached is twice or more that of sample 1, and it can be seen that it is difficult to effectively suppress abnormal heat generation due to overcharging only by providing a shutdown function only in the heat-resistant layer. However, compared with Samples 4 to 5, both the shutdown start temperature and the maximum temperature reached are low, indicating that suppression of heat generation at an early stage has a certain effect on suppression of thermal runaway.

  Further, the battery of Sample 4 has a shutdown function by the granular polymer B only in the positive electrode active material layer. The shutdown due to the positive electrode active material layer was manifested at a battery surface temperature of 100 ° C., which was higher than that of the batteries of Samples 1 and 2. At this point in time, the battery temperature had already started to increase at an accelerated rate, so that the battery temperature continued to increase even after the energization was disabled, and the maximum temperature reached 320 ° C. It cannot be said that heat generation at an early stage cannot be suppressed, and an effect to prevent a rapid temperature increase due to overcharging cannot be obtained.

  The battery of Sample 5 did not have a shutdown function by the granular polymers A and B, and the shutdown by the separator itself began after the battery surface temperature became as high as 105 ° C. Therefore, at the time of the start of shutdown, the battery temperature has already started to rise at an accelerated rate, and the battery temperature has continued to rise even after the battery cannot be energized. The maximum temperature reached 350 ° C. .

<Samples 6 to 11>
Samples 6 to 11 were prepared by changing the materials and blends of the lithium ion battery for evaluation of sample 1 as shown in Table 2, and constructing a lithium ion battery for evaluation in the same manner as sample 1. .
That is, in Samples 6 to 11, the inorganic filler of the heat-resistant layer in Sample 1 was changed to boehmite (D ₅₀ = 1.2 μm), and the granular polymer A was changed to an ethylene-vinyl acetate copolymer (D ₅₀ = 0.5 μm). It changed and the mass ratio of the granular polymer A with respect to these total amount was changed in 5-50 mass%.
Further, the granular polymer B in the positive electrode active material layer was changed to polyethylene (D ₅₀ = 1.2 μm), and the mass ratio of the granular polymer B to the total amount of the positive electrode active material layer and the granular polymer B was 8 mass%.

<Samples 12 to 16>
Samples 12 to 16 were prepared by changing the materials and blends of the evaluation lithium ion battery of sample 1 as shown in Table 2, and constructing the evaluation lithium ion battery in the same manner as in sample 1. .
That is, in Samples 12 to 16, the inorganic filler of the heat-resistant layer in Sample 1 was changed to alumina (D ₅₀ = 0.9 μm), the granular polymer A was left as polyethylene (D ₅₀ = 0.3 μm), and the inorganic filler and The mass ratio of the granular polymer A to the total amount of the granular polymer A was changed to 30% by mass.
Moreover, the granular polymer B in the positive electrode active material layer is changed to an ethylene-acrylic acid copolymer (D ₅₀ = 0.8 μm), and the mass ratio of the granular polymer B to the total amount of the positive electrode active material layer and the granular polymer B is 1 mass. % To 15% by mass.

[Porosity measurement]
The porosity of the heat-resistant layer in the separators used for the above samples 6 to 11 and samples 12 to 16 was examined in advance. That is, first, the apparent volume V ₁ (cm ³ ) and the mass W (g) of the heat-resistant layer were measured. At this time, the thickness of the heat-resistant layer can be determined by measuring the total thickness of the heat-resistant layer and the separator and then measuring and subtracting the thickness of the separator from which the heat-resistant layer has been peeled off. The mass of the heat-resistant layer can also be determined by measuring the total mass of the heat-resistant layer and the separator and then measuring and subtracting the mass of the separator from which the heat-resistant layer has been peeled off.
Here, when the true density of the material constituting the heat-resistant layer is ρ (g / cm ³ ), the actual volume V ₀ of the heat-resistant layer can be expressed by W / ρ, and the porosity ε of the heat-resistant layer is (V ₁ can be calculated by _{-V 0) / V 1 × 100} . Table 2 shows the calculated porosity of the heat-resistant layer.

[Measurement of battery capacity]
The battery capacities of the lithium ion batteries of Samples 6 to 11 and Samples 12 to 16 were measured.
That is, first, under a temperature condition of room temperature (25 ° C.), charging is performed up to an upper limit voltage of 4.1 V at a current density of 24 A (equivalent to 1 C) by a constant current-constant voltage method, and thereafter, the lower limit voltage of 3. The battery capacity was measured by performing constant current discharge to 0V. Table 2 shows the measured values of battery capacity.

[Measurement of internal resistance]
After measuring the battery capacity, the internal resistance (IV resistance value) of each battery was measured. That is, each battery was discharged at a constant current to 3.0 V under a temperature condition of 25 ° C., and then charged at a constant current and a constant voltage to adjust to SOC (state of charge) 50%. Thereafter, a discharge pulse current of 10 seconds was applied at 25 ° C. and 1 C, and the voltage V1 at the 10 seconds was measured. After that, for the battery adjusted to SOC 50% again, the pulse current is increased stepwise in the order of 2C, 5C and 10C to alternately discharge and charge, and measure the voltage 10 seconds after the start of each discharge. An IV characteristic graph of each battery was prepared. The IV resistance value (mΩ) at 25 ° C. was calculated from the slope of this IV characteristic graph. Table 2 shows the internal resistance values of the batteries.

[Continuous overcharge test]
Similarly to Sample 1, the continuous overcharge test was performed on the lithium ion batteries of Samples 6 to 11 and Samples 12 to 16, and the shutdown start temperature and the maximum reached temperature (° C.) were measured. The results are shown in Table 2.

  As shown in Table 2, from the result of the continuous overcharge test, any of the batteries of Samples 6 to 11 and Samples 12 to 16 was shut down by the granular polymer in the heat resistant layer of the separator and the positive electrode active material layer of the positive electrode. It was confirmed that the heat generation could be suppressed while controlling the heat generation behavior of the battery during overcharge because of the function. For example, the maximum reached temperature of the battery was 240 ° C. or lower, which was significantly lower than those of Samples 3 to 5.

  Moreover, the ratio of the granular polymer A mix | blended with a heat-resistant layer shall be 10 mass% or more, and the ratio of the granular polymer B mix | blended with a positive electrode active material layer shall be 3 mass% or more, The increase effect of the internal resistance at the time of abnormal heat generation It was confirmed that abnormal heat generation can be stopped with higher safety. It was also found that the ratio of the granular polymer A blended in the heat-resistant layer was 40% by mass or less, and the ratio of the granular polymer B blended in the positive electrode active material layer was 10% by mass or less. It was found that adding more than this amount is not preferable because the internal resistance of the battery during normal use increases. Thus, it was confirmed that the battery characteristics and the shutdown characteristics can be provided in a well-balanced manner by adjusting the blending amounts of the granular polymer A and the granular polymer B.

  For example, as in Samples 7 to 10 and Samples 13 to 15, by setting the amount of granular polymers A and B blended in the heat-resistant layer of the separator and the positive electrode active material layer in a more appropriate range, the internal resistance can be reduced. It was confirmed that the shutdown start temperature was 99 ° C. or lower and the maximum temperature reached was 135 ° C. or lower and the extremely low range without impairing the battery characteristics of 2.5 mΩ or lower. In this way, the granular polymers A and B are blended in appropriate positions and in appropriate amounts in appropriate amounts, so that the location where the shutdown function is expressed, the timing, and the effect of the shutdown function can be balanced. . As a result, it has been found that abnormal heat generation can be suppressed more safely and reliably than by unnecessarily reducing battery characteristics during normal use.

  According to the present invention, even in a battery that can realize high input / output density and high energy density, abnormal heat generation of the battery can be more reliably and safely suppressed without excessively degrading battery characteristics. A non-aqueous electrolyte secondary battery can be provided.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Lithium ion battery 20 Winding electrode body 30 Positive electrode (positive electrode sheet)
32 Cathode current collector 33 Uncoated part 34 Cathode active material layer 38 Granular polymer B
40 Positive terminal 41 Positive lead terminal 50 Negative electrode sheet (negative electrode)
52 Negative electrode current collector 53 Uncoated part 54 Negative electrode active material layer 60 Negative electrode terminal 61 Negative electrode lead terminal 70 Separator 72 Heat resistant layer 78 Granular polymer A
80 Battery case 82 Lid 84 Container body 85 Crevice 86 Injection hole 87 Sealing cap 88 Safety valve 100 Battery pack WL Winding shaft

Claims (8)

A nonaqueous electrolyte secondary battery comprising a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, a separator made of a thermoplastic resin interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. There,
The separator includes a heat-resistant layer including an inorganic filler and a granular polymer A made of a polyolefin resin having a melting point in a temperature range of 80 ° C. or higher and 100 ° C. or lower on at least one surface,
The positive active material layer, seen containing a cathode active material, the temperature range of beyond 120 ° C. below the melting point of the particulate polymer A and a particulate polymer B comprising a polyolefin resin having a melting point,
The positive electrode active material includes a lithium transition metal composite oxide,
The negative electrode active material includes a carbon material,
The granular polymer A is included in a proportion of 10% by mass to 40% by mass when the total amount of the inorganic filler and the granular polymer A is 100% by mass.
The granular polymer B is a non-aqueous electrolyte secondary battery that is included in a ratio of 3 to 10% by mass when the total amount of the positive electrode active material and the granular polymer B is 100% by mass . The positive electrode active material layer further includes a conductive material,
The nonaqueous electrolyte secondary battery according to claim 1, wherein the granular polymer B and the conductive material are uniformly dispersed. 3. The non-aqueous solution according to claim 1, wherein the inorganic filler has an average particle size of 0.5 μm to 5.0 μm, and the granular polymer A has an average particle size of 0.1 μm to 3.0 μm. Electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the positive electrode and the negative electrode are wound electrode bodies that are overlapped and wound with the separator interposed therebetween.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the heat-resistant layer has a porosity of 30% or more and 70% or less. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, which is used as a power source for a vehicle .   A vehicle comprising the non-aqueous electrolyte secondary battery according to claim 1. A method for producing the nonaqueous electrolyte secondary battery according to any one of claims 1 to 6, comprising:
A composition for forming a heat-resistant layer comprising an inorganic filler, a granular polymer A composed of a polyolefin resin having a melting point in a temperature range of 80 ° C. or higher and 100 ° C. or lower, and a binder is prepared, and at least a separator substrate made of a thermoplastic resin A separator having a heat-resistant layer formed by supplying to one surface is prepared . Here, the granular polymer A is 10% by mass when the total amount of the inorganic filler and the granular polymer A is 100% by mass. Contained in a proportion of ˜40% by weight ;
A positive electrode active material including a lithium transition metal composite oxide , a conductive material, a granular polymer B made of a polyolefin resin having a melting point in the temperature range of 120 ° C. or less exceeding the melting point of the granular polymer A, and a binder. Preparing a composition for forming a positive electrode active material layer, wherein the granular polymer B is in a ratio of 3 to 10% by mass when the total amount of the positive electrode active material and the granular polymer B is 100% by mass. And the composition is prepared by dispersing the conductive material, the granular polymer B, and the binder in a predetermined solvent, and then dispersing the positive electrode active material in the dispersion;
Providing a positive electrode on which a positive electrode active material layer is formed by supplying the prepared composition for forming a positive electrode active material layer to at least one surface of a positive electrode current collector;
A negative electrode in which a negative electrode active material layer is formed by preparing a negative electrode active material layer-forming composition containing a carbon material and a binder and supplying the composition to at least one surface of a negative electrode current collector is prepared. And constructing a non-aqueous electrolyte secondary battery using the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte;
Manufacturing method.

Images