JP2018174032A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

An object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of suppressing the surface temperature. SOLUTION: This non-aqueous electrolyte secondary battery comprises a positive electrode having a positive electrode current collector connected to a positive electrode terminal, a negative electrode having a negative electrode current collector connected to a negative electrode terminal, and the positive electrode and the negative electrode. A separator disposed between the separators, and a laminate having one or more layers each, the area of a minute region that divides the laminate in plan view is dS, and the center of gravity of the minute region indicates the positive electrode terminal or the negative electrode terminal. When the distance to the connection center of the nearer terminal is r, the aspect ratio of the laminate is within a predetermined range with respect to the aspect ratio Amin which is the minimum value Emin of the integrated value of r×dS. [Selection diagram] Fig. 3

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  A lithium ion secondary battery is known as an example of a non-aqueous electrolyte secondary battery. Lithium ion secondary batteries are lighter and have a higher capacity than nickel cadmium batteries and nickel metal hydride batteries, and are widely used as power sources for portable electronic devices.

  On the other hand, since lithium is highly reactive, attempts have been made to increase the safety of lithium ion secondary batteries. If overcharge or the like occurs during operation of the lithium ion secondary battery, the battery generates heat. The heat generation of the battery causes a decrease in the life and deterioration of the nonaqueous electrolyte secondary battery.

  Patent Document 1 describes that a heat radiating plate is provided to efficiently release heat. Patent Document 2 describes increasing the thermal conductivity in the thickness direction of the separator. In Patent Document 3, a metal shaft center that is continuous from the inside of the battery to the outside is provided, and the shaft core and the connecting member of the positive electrode or the negative electrode are joined, so that heat generated due to an abnormal battery reaction such as overcharging can be prevented. It is described that heat can be dissipated through the connecting member.

JP 2011-113895 A JP 2006-269358 A JP 2006-40772 A

  However, when a heat sink that does not contribute to the reaction of the battery as in Patent Document 1 is provided, the nonaqueous electrolyte secondary battery becomes bulky and the integration property is lowered. In addition, the lithium secondary batteries described in Patent Documents 2 and 3 cannot efficiently release heat in the in-plane direction of the nonaqueous electrolyte secondary battery.

  This invention is made | formed in view of the said problem, and it aims at providing the nonaqueous electrolyte secondary battery which can suppress the surface temperature at the time of overcharge.

The present inventors determine the relationship between the positions of the positive electrode terminal and the negative electrode terminal and the shape of the laminate using the common technical idea of the newly found integral value (the following general formula (1)). Thus, it was found that the non-aqueous electrolyte secondary battery can be prevented from becoming high temperature.
That is, in order to solve the above problems, the following means are provided.

(1) A nonaqueous electrolyte secondary battery according to a first aspect includes a positive electrode having a positive electrode current collector to which a positive electrode terminal is connected, a negative electrode having a negative electrode current collector to which a negative electrode terminal is connected, and the positive electrode And a separator disposed between the negative electrodes, and each of the positive electrode terminal and the negative electrode terminal is provided on one side surface when the laminate is viewed in plan from the stacking direction. When the area of the micro region that is connected and classifies the stacked body in plan view is dS, and the distance from the center of gravity of the micro region to the connection center of the positive terminal or the terminal closer to the negative terminal is r, The aspect ratio of the laminate is in the range of 0.6 to 2.8 times the aspect ratio A _{min in} which the following general formula (1) takes the minimum value E _min .

(2) A nonaqueous electrolyte secondary battery according to a second aspect includes a positive electrode having a positive electrode current collector to which a positive electrode terminal is connected, a negative electrode having a negative electrode current collector to which a negative electrode terminal is connected, and the positive electrode And a separator disposed between the negative electrodes, and the positive electrode terminal and the negative electrode terminal differ from each other when the laminate is viewed in plan from the stacking direction. The area of the minute region that is connected to each side surface and divides the laminate in plan view is dS, and the distance from the center of gravity of the minute region to the connection center of the positive terminal or the terminal closer to the negative terminal is r. In this case, the aspect ratio of the laminate is in the range of 0.6 to 2.1 times the aspect ratio A _{min in} which the following general formula (1) takes the minimum value E _min .

(3) A nonaqueous electrolyte secondary battery according to a third aspect includes a positive electrode having a positive electrode current collector to which a positive electrode terminal is connected, a negative electrode having a negative electrode current collector to which a negative electrode terminal is connected, and the positive electrode And a separator disposed between the negative electrodes, and each of the positive electrode terminal and the negative electrode terminal is a surface of the stacked body when the stacked body is viewed in plan from the stacking direction. DS is the area of the micro area that is connected to each other in the plan view, and r is the distance from the center of gravity of the micro area to the connection center of the positive terminal or the terminal closer to the negative terminal. In this case, the aspect ratio of the laminate is in the range of 0.4 to 1.6 times the aspect ratio A _{min in} which the following general formula (1) takes the minimum value E _min .

(4) In the non-aqueous electrolyte secondary battery according to the above aspect, the aspect ratio of the laminate may be an aspect ratio A _min where the general formula (1) takes a minimum value E _min .

  According to the nonaqueous electrolyte secondary battery according to the above aspect, it is possible to suppress the surface temperature from becoming high during overcharge.

It is a cross-sectional schematic diagram of the non-aqueous electrolyte secondary battery according to the first embodiment. It is a perspective schematic diagram of the laminated body of the nonaqueous electrolyte secondary battery concerning 1st Embodiment. It is a plane schematic diagram of the laminated body of the nonaqueous electrolyte secondary battery concerning 1st Embodiment. It is a plane schematic diagram of the laminated body of the nonaqueous electrolyte secondary battery concerning 2nd Embodiment. It is a plane schematic diagram of the laminated body of the nonaqueous electrolyte secondary battery concerning 3rd Embodiment. It is a cross-sectional schematic diagram of the non-aqueous electrolyte secondary battery according to the third embodiment. It is a plane schematic diagram of the laminated body of the nonaqueous electrolyte secondary battery concerning 4th Embodiment. In Example 1, the maximum shape of the surface temperature at the time of overcharge when the planar shape of the laminate is rectangular and the positive electrode terminal and the negative electrode terminal are connected to one side surface of the laminate, respectively. In Example 2, the maximum shape of the surface temperature at the time of overcharge when the planar shape of the laminated body is rectangular and the positive electrode terminal and the negative electrode terminal are respectively connected to two opposite side surfaces of the laminated body is shown. In Example 3, the maximum shape of the surface temperature at the time of overcharge in the case where the planar shape of the laminate is rectangular and the positive electrode terminal and the negative electrode terminal are respectively connected in the plane of the laminate is shown. In Example 4, the maximum shape of the surface temperature at the time of overcharge when the planar shape of the laminate is an ellipse and the positive electrode terminal and the negative electrode terminal are respectively connected in the plane of the laminate is shown.

  Hereinafter, the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, there are cases where the characteristic parts are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. is there. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately modified and implemented without departing from the scope of the invention.

“First Embodiment”
[Nonaqueous electrolyte secondary battery]
FIG. 1 is a schematic cross-sectional view of the nonaqueous electrolyte secondary battery according to the first embodiment. As shown in FIG. 1, the nonaqueous electrolyte secondary battery 100 according to the first embodiment includes a laminated body 40 and an exterior body 50. The laminated body 40 and the non-aqueous electrolyte (not shown) are accommodated in an accommodation space provided in the exterior body 50.

(Laminate)
As illustrated in FIG. 1, the stacked body 40 includes one or more layers of the positive electrode 20, the negative electrode 30, and the separator 10. The separator 10 is disposed between the positive electrode 20 and the negative electrode 30. The positive electrode 20, the negative electrode 30, and the separator 10 are each provided with one or more layers.

  The positive electrode 20 includes a positive electrode current collector 22, a positive electrode active material layer 24, and a positive electrode terminal 26. The positive terminal 26 has a first end connected to the positive electrode current collector 22 and a second end extending to the outside of the exterior body 50. Hereinafter, the stacking direction of the stacked body 40 is defined as the z direction, one direction perpendicular to the z direction is defined as the x direction, and the direction perpendicular to the x direction within the surface is defined as the y direction.

"Positive electrode"
The positive electrode 20 includes a positive electrode current collector 22 and a positive electrode active material layer 24. The positive electrode active material layer 24 is disposed on both surfaces of the positive electrode current collector 22.

  The positive electrode current collector 22 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used. The positive electrode terminal 26 only needs to have conductivity, and the same thing as the positive electrode current collector 22 can be used. In order to lower the contact resistance, it is preferable to use the same material in any case.

  The positive electrode active material layer 24 includes a positive electrode active material and a binder, and includes a conductive additive as necessary.

The positive electrode active material reversibly advances ion insertion and extraction, ion desorption and insertion (intercalation), or ion and ion counter anion (for example, PF ₆ ⁻ ). The electrode active material which can be used can be used. As ions, lithium, magnesium, or the like can be used.

For example, lithium cobalt oxide (LiCoO _2), lithium nickelate (LiNiO _2), lithium manganate (LiMnO _2), lithium manganese spinel (LiMn ₂ O _4), and the general _{formula: LiNi x Co y Mn z M} a O ₂ (x + y + z + a = 1, 0 ≦ x <1, 0 ≦ y <1, 0 ≦ z <1, 0 ≦ a <1, M is one type selected from Al, Mg, Nb, Ti, Cu, Zn, Cr Complex metal oxides represented by the above elements), lithium vanadium compounds (LiV ₂ O ₅ ), olivine-type LiMPO ₄ (where M is Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr) One or more elements or VO selected from the above, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), LiNi _x Co _y Al _z O ₂ (0.9 <x + y + z < 1.1) and the like, and polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene and the like.

  Examples of the conductive assistant include carbon powders such as carbon blacks, carbon nanotubes, carbon materials, metal fine powders such as copper, nickel, stainless steel, and iron, a mixture of carbon materials and metal fine powders, and conductive oxides such as ITO. It is done. In the case where sufficient conductivity can be ensured with only the positive electrode active material, the non-aqueous electrolyte secondary battery 100 may not include a conductive additive.

  The positive electrode active material layer includes a binder. A well-known thing can be used for a binder. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoro Fluorine resins such as ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and polyvinyl fluoride (PVF).

"Negative electrode"
The negative electrode 30 includes a negative electrode current collector 32, a negative electrode active material layer 34, and a negative electrode terminal 36. The negative terminal 36 has a first end connected to the negative electrode current collector 32 and a second end extending to the outside of the outer package 50.

  The negative electrode current collector 32 and the negative electrode terminal 36 can be the same as the positive electrode. Similarly to the positive electrode current collector 22, the negative electrode active material layer 34 is disposed on both surfaces of the negative electrode current collector 32.

  The negative electrode current collector 32 and the negative electrode terminal 36 may be the same as the positive electrode current collector 22 and the positive electrode terminal 26 of the positive electrode 20. Since lithium may precipitate in the negative electrode 30, it is particularly preferable to use copper having low reactivity with lithium for the negative electrode current collector 32 and the negative electrode terminal 36.

  The negative electrode active material layer 34 includes a negative electrode active material and a binder, and includes a conductive additive as necessary.

The negative electrode active material may be any compound that can occlude and release lithium ions, and a known negative electrode active material can be used. Examples of the negative electrode active material include carbon materials such as metallic lithium, graphite capable of occluding and releasing lithium ions (natural graphite, artificial graphite), carbon nanotubes, non-graphitizable carbon, graphitizable carbon, and low-temperature calcined carbon. Metals that can be combined with lithium such as aluminum, silicon and tin, amorphous compounds mainly composed of oxides such as SiO _x (0 <x <2) and tin dioxide, lithium titanate (Li ₄ Ti ₅ And particles containing O ₁₂ ) and the like.

  As the conductive auxiliary agent and the binder, the same materials as those for the positive electrode can be used. The binder used for the negative electrode 30 may be, for example, cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, acrylic resin, or the like, in addition to those listed for the positive electrode 20.

"Separator"
The separator 10 only needs to be formed of an electrically insulating porous structure, for example, a single layer of a film made of polyethylene, polypropylene, or polyolefin, a stretched film of a laminate or a mixture of the above resins, or cellulose, polyester, and Examples thereof include a fiber nonwoven fabric made of at least one constituent material selected from the group consisting of polypropylene.

"Electrolyte"
The electrolytic solution is impregnated in the positive electrode active material layer 24 and the negative electrode active material layer 34. As the electrolytic solution, an electrolyte solution containing lithium salt or the like (electrolyte aqueous solution, electrolyte solution using an organic solvent) can be used. However, since the electrolytic aqueous solution has a low decomposition voltage electrochemically, the withstand voltage during charging is limited to be low. Therefore, an electrolyte solution (nonaqueous electrolyte solution) using an organic solvent is preferable.

  In the non-aqueous electrolyte solution, an electrolyte is dissolved in a non-aqueous solvent, and a cyclic carbonate and a chain carbonate may be contained as a non-aqueous solvent.

  As cyclic carbonate, what can solvate electrolyte can be used. For example, ethylene carbonate, propylene carbonate, butylene carbonate, and the like can be used.

  The chain carbonate can reduce the viscosity of the cyclic carbonate. Examples thereof include diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. In addition, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, and the like may be mixed and used.

  The ratio of the cyclic carbonate and the chain carbonate in the non-aqueous solvent is preferably 1: 9 to 1: 1 by volume.

(Exterior body)
The exterior body 50 seals the laminated body 40 and the electrolytic solution therein. The outer package 50 suppresses leakage of the electrolytic solution to the outside, penetration of moisture and the like into the nonaqueous electrolyte secondary battery 100 from the outside, and the like.

  For example, a metal laminate film in which a metal foil is coated with a polymer film from both sides can be used as the exterior body 50. For example, an aluminum foil can be used as the metal foil, and a film such as polypropylene can be used as the polymer film. For example, the material of the outer polymer film is preferably a polymer having a high melting point, such as polyethylene terephthalate (PET) or polyamide, and the material of the inner polymer film is polyethylene (PE) or polypropylene (PP). preferable.

[Functions of non-aqueous electrolyte secondary battery and plan shape of laminated body]
The non-aqueous electrolyte secondary battery 100 operates as lithium ions move between the positive electrode active material layer 24 and the negative electrode active material layer 34.

  For example, when lithium ions move from the positive electrode active material layer 24 to the negative electrode active material layer 34 via the separator 10, a potential difference is generated between the positive electrode 20 and the negative electrode 30. Electrons captured by lithium ions in the negative electrode active material layer 34 move so as to reduce this potential difference. Since the separator 10 has insulating properties, it cannot move directly from the negative electrode active material layer 34 to the positive electrode active material layer 24 via the separator 10. Therefore, electrons flow to the outside through the positive electrode current collector 22 and the positive electrode terminal 26. When this reverse reaction occurs, electrons flow to the outside through the negative electrode current collector 32 and the negative electrode terminal 36.

  FIG. 2 is a schematic perspective view of a laminate of the nonaqueous electrolyte secondary battery according to this embodiment. As shown in FIG. 2, the first end portion 26 </ b> A of the positive electrode terminal 26 and the first end portion 36 </ b> A of the negative electrode terminal 36 are connected to the positive electrode current collector 22 and the negative electrode current collector 32, respectively. On the other hand, in the second end portion 26B of the positive electrode terminal 26 and the second end portion 36B of the negative electrode terminal 36, the positive electrode terminal 26 and the negative electrode terminal 36 extending from the positive electrode current collector 22 and the negative electrode current collector 32 are integrated. The exterior body 50 is extended to the outside.

  Therefore, when electrons generated at the positive electrode are discharged to the outside, the second end portion 26B of the positive electrode terminal 26 passes, and when electrons generated at the negative electrode are discharged to the outside, the second end portion of the negative electrode terminal 36 is discharged. Pass 36B.

  When electrons are exchanged in the stacked body 40, the stacked body 40 generates heat. The heat exhaust path when the heat generated in the stacked body 40 is exhausted is the same as the electron exhaust path. The periphery of the laminate 40 is covered with an exterior body 50. Therefore, heat is not easily discharged through the exterior body 50, and most of the generated heat is discharged from the second end portions 26 </ b> B and 36 </ b> B through the positive terminal 26 and the negative terminal 36.

  That is, the heat removal efficiency of the heat generated in the stacked body 40 depends on how the positive electrode terminal 26 and the negative electrode terminal 36 are arranged with respect to the stacked body, in other words, at the connection position of the positive electrode terminal 26 and the negative electrode terminal 36. On the other hand, the exhaust heat efficiency of the nonaqueous electrolyte secondary battery 100 varies depending on how the shape of the stacked body 40 is set.

  FIG. 3 is a schematic plan view of a laminate of the nonaqueous electrolyte secondary battery according to the first embodiment. In FIG. 3, the positive electrode terminal 26 and the negative electrode terminal 36 are respectively connected to one side surface when the stacked body 40 is viewed from the z direction. The connection center 26a at the center in the width direction of the positive electrode terminal 26 and the connection center 36a at the center in the width direction of the negative electrode terminal 36 are perpendicular to the direction in which the positive electrode terminal 26 and the negative electrode terminal 36 of the laminate 40 extend (y direction). It is provided at the center in the y direction of each region divided by the center line C.

  In the case shown in FIG. 3, the heat generated at a position away from the positive terminal 26 and the negative terminal 36 is difficult to exhaust. That is, the aspect ratio of the laminated body 40 affects the exhaust heat efficiency of the nonaqueous electrolyte secondary battery 100.

  In the first embodiment, the aspect ratio refers to the length L1 of the stacked body 40 in the x direction in which the positive electrode terminal 26 and the negative electrode terminal 36 extend, and y orthogonal to the x direction in which the positive electrode terminal 26 and the negative electrode terminal 36 extend. It is the ratio of the length of the laminate 40 in the direction, and is represented by L1 / L2. In FIG. 3, the positive electrode terminal 26 and the negative electrode terminal 36 are connected to the side surface along the minor axis direction of the stacked body 40, but may be connected to the side surface along the major axis direction.

  When the aspect ratio L1 / L2 of the laminate 40 is designed as follows, the exhaust heat efficiency of the nonaqueous electrolyte secondary battery 100 is increased.

  First, a minute region that divides the stacked body 40 in plan view is set. The minute region is a region that is sufficiently small with respect to the area of the stacked body 40 in plan view. The sufficiently small region refers to a region in which the stacked body 40 is divided into 1000 or more divisions with the same area.

  Next, let r be the distance from the center of gravity of this minute region to the connection centers 26a, 36a of the terminal closer to the positive electrode terminal 26 or the negative electrode terminal 36. Then, the area dS of the micro area is multiplied by the distance r between the micro area and the terminal (r × dS). Heat generated in the minute region is mainly discharged from the nearest positive electrode terminal 26 or negative electrode terminal 36. Therefore, r × dS is obtained by multiplying the heat generated in the minute region by the distance until the heat is exhausted, and the larger this value is, the more difficult it is to exhaust the heat.

  This r × dS is obtained for each of the minute regions, and the values are added together. The aggregate of the minute regions is the planar shape of the stacked body 40. That is, the sum of r × dS in each minute region is a set of products obtained by multiplying the total amount of exhaust heat in the in-plane direction of the laminate 40 by the exhaust heat distance, and can be expressed by the following general formula (1). .

This general formula (1) takes a minimum value E _min when the aspect ratio L1 / L2 is a predetermined aspect ratio A _min . The aspect ratio L1 / L2 that takes the minimum value E _min is 4.0. When designing the planar shape of the laminated body 40 to the aspect ratio A _min taking this minimum value E _min, heat efficiency of the non-aqueous electrolyte secondary cell 100 is the highest, the highest temperature of the surface of the non-aqueous electrolyte secondary battery 100 The lowest. That is, when the positive electrode terminal 26 and the negative electrode terminal 36 are provided on the same side surface of the stacked body 40, it is preferable that the planar shape of the stacked body 40 is elongated in the direction in which the positive electrode terminal 26 and the negative electrode terminal 36 extend.

On the other hand, the aspect ratio of the stacked body 40 is not limited to one point that satisfies the above conditions, and a certain amount of deviation from the position that satisfies the above conditions is allowed. The aspect ratio of the laminate 40 is preferably in the range of 0.6 to 2.8 times the aspect ratio A _min taking the minimum value E _min , and is 0.8 to 1.7 times. It is more preferable to be within the range. Specifically, the aspect ratio L1 / L2 is preferably 2.5 or more and 11.0 or less, and more preferably 3.0 or more and 7.0 or less.

  As described above, according to the nonaqueous electrolyte secondary battery according to the first embodiment, the exhaust heat efficiency in the in-plane direction of the nonaqueous electrolyte secondary battery can be increased. As a result, the maximum temperature on the surface of the nonaqueous electrolyte secondary battery 100 can be lowered.

“Second Embodiment”
FIG. 4 is a schematic plan view of a laminate of the nonaqueous electrolyte secondary battery according to the second embodiment. The non-aqueous electrolyte secondary battery laminate 41 according to the second embodiment is different from the first embodiment in that the positive electrode terminal 26 and the negative electrode terminal 36 are respectively connected to different side surfaces of the laminate 41. Different from water electrolyte secondary battery. Other configurations are the same as those of the non-aqueous electrolyte secondary battery according to the first embodiment.

  In FIG. 4, the positive electrode terminal 26 and the negative electrode terminal 36 are provided at positions facing each other. The connection center 26a at the center in the width direction of the positive electrode terminal 26 and the connection center 36a at the center in the width direction of the negative electrode terminal 36 are in the direction (y direction) orthogonal to the direction in which the positive electrode terminal 26 and the negative electrode terminal 36 of the laminate 40 extend. It is provided on the center line C.

  Also in the laminated body 41 according to the second embodiment, when the aspect ratio L1 / L2 of the laminated body 41 is designed within a predetermined range, the exhaust heat efficiency of the nonaqueous electrolyte secondary battery is increased. In the second embodiment, the aspect ratio is a ratio between the length L1 of the stacked body 41 in the x direction in which the positive electrode terminal 26 and the negative electrode terminal 36 extend and the length L2 of the stacked body 41 in the y direction orthogonal to the x direction. And is represented by L1 / L2.

  The relationship between the area dS of the micro region and the distance r between the micro region and the positive electrode terminal 26 or the negative electrode terminal 36 in the multilayer body 41 according to the second embodiment is the same as that of the multilayer body 40 according to the first embodiment.

That is, when the above-described general formula (1) designs the planar shape of the stacked body 41 to the aspect ratio A _min where the minimum value E _min is taken, the heat exhaust efficiency of the non-aqueous electrolyte secondary battery 100 becomes the highest, and the non-aqueous electrolyte 2 The maximum temperature on the surface of the secondary battery 100 is the lowest. The aspect ratio L1 / L2 that takes the minimum value E _min is 1.0.

The aspect ratio of the laminate 41 is not limited to this case, and is preferably in the range of 0.6 to 2.1 times the aspect ratio A _min that takes the minimum value E _min. More preferably, it is in the range of not less than twice and not more than 1.75 times. Specifically, the aspect ratio L1 / L2 is preferably 0.6 or more and 2.1 or less, and more preferably 0.8 or more and 1.8 or less.

  As described above, according to the nonaqueous electrolyte secondary battery according to the second embodiment, the exhaust heat efficiency in the in-plane direction of the nonaqueous electrolyte secondary battery can be increased. As a result, the maximum temperature on the surface of the nonaqueous electrolyte secondary battery 100 can be lowered.

“Third Embodiment”
FIG. 5 is a schematic plan view of a laminate of the nonaqueous electrolyte secondary battery according to the third embodiment. The non-aqueous electrolyte secondary battery laminate 42 according to the third embodiment is different from the first embodiment in that the positive electrode terminal 26 and the negative electrode terminal 36 are respectively connected in the plane of the laminate 42. Different from water electrolyte secondary battery. Other configurations are the same as those of the non-aqueous electrolyte secondary battery according to the first embodiment.

  As shown in FIG. 5, the positive electrode terminal 26 and the negative electrode terminal 36 in the nonaqueous electrolyte secondary battery according to the third embodiment are provided at the center of each region where the laminate 42 is divided by the center line C in the x direction. It has been. In this case, the connection centers 26 a and 36 a of the positive terminal 26 and the negative terminal 36 are the center of the positive terminal 26 and the negative terminal 36 in plan view.

  FIG. 6 is a schematic cross-sectional view of the nonaqueous electrolyte secondary battery 102 according to the third embodiment. As shown in FIG. 6, the positive terminal 26 and the negative terminal 36 are provided so as to penetrate in the stacking direction of the stacked body 42. In order to prevent a short circuit with the negative electrode 30, the positive electrode terminal 26 is covered with an insulator 26 </ b> I except for a contact portion with the positive electrode 20. Similarly, the negative electrode terminal 36 is also covered with an insulator 36I except for the contact portion with the negative electrode 30 in order to prevent a short circuit with the positive electrode 20.

  Also in the laminated body 42 according to the third embodiment, when the aspect ratio L1 / L2 of the laminated body 42 is designed within a predetermined range, the exhaust heat efficiency of the nonaqueous electrolyte secondary battery 102 is increased. In the third embodiment, the aspect ratio is a ratio between the major axis length L1 of the multilayer body 42 and the length L2 of the multilayer body in the minor axis direction, and is represented by L1 / L2.

  The relationship between the area dS of the micro region and the distance r between the micro region and the positive electrode terminal 26 or the negative electrode terminal 36 in the multilayer body 42 according to the third embodiment is the same as that of the multilayer body 40 according to the first embodiment.

That the above general formula (1) is, when designing the planar shape of the laminated body 42 to the aspect ratio A _min which takes a minimum value E _min, the non-aqueous heat efficiency of electrolyte secondary cell 100 is the highest, non-aqueous electrolyte secondary The maximum temperature on the surface of the secondary battery 100 is the lowest. The aspect ratio L1 / L2 that takes the minimum value E _min is 2.0.

The aspect ratio of the laminate 42 is not limited to this case, and is preferably in the range of 0.4 to 1.6 times the aspect ratio A _min that takes the minimum value E _min. It is more preferable that it is in the range of not less than twice and not more than 1.3 times. Specifically, the aspect ratio L1 / L2 is preferably 1.0 or more and 3.0 or less, and more preferably 1.4 or more and 2.6 or less.

  As described above, according to the nonaqueous electrolyte secondary battery according to the third embodiment, the exhaust heat efficiency in the in-plane direction of the nonaqueous electrolyte secondary battery can be increased. As a result, the maximum temperature of the surface of the nonaqueous electrolyte secondary battery can be lowered.

“Fourth Embodiment”
FIG. 7 is a schematic plan view of a laminated body of the nonaqueous electrolyte secondary battery according to the fourth embodiment. The laminated body 43 of the nonaqueous electrolyte secondary battery according to the fourth embodiment is such that the positive electrode terminal 26 and the negative electrode terminal 36 are respectively connected in the plane of the laminated body 43, and the planar shape of the laminated body 43 is not rectangular. However, it is different from the nonaqueous electrolyte secondary battery according to the first embodiment. Other configurations are the same as those of the non-aqueous electrolyte secondary battery according to the first embodiment.

  The laminate 43 shown in FIG. 7 has an elliptical shape in plan view. In the nonaqueous electrolyte secondary battery according to the fourth embodiment, the positive electrode terminal 26 and the negative electrode terminal 36 are provided at equal distances with the center line C in the major axis direction of the laminate 43 interposed therebetween. The connection centers 26 a and 36 a of the positive electrode terminal 26 and the negative electrode terminal 36 are the center in plan view of the positive electrode terminal 26 and the negative electrode terminal 36. The cross-sectional shape of the laminated body 43 is equivalent to that of the nonaqueous electrolyte secondary battery 102 according to the third embodiment shown in FIG.

  Also in the laminate 43 according to the fourth embodiment, when the aspect ratio L1 / L2 between the length L1 in the major axis direction and the length L2 in the minor axis direction of the laminate 43 is designed within a predetermined range, the non-aqueous electrolyte 2 The exhaust heat efficiency of the secondary battery is increased. In the fourth embodiment, the aspect ratio is a ratio of the length L1 in the major axis direction of the laminate 43 to the length L2 in the minor axis direction of the laminate, and is represented by L1 / L2.

  The relationship between the area dS of the micro region and the distance r between the micro region and the positive electrode terminal 26 or the negative electrode terminal 36 in the multilayer body 43 according to the fourth embodiment is the same as that of the multilayer body 40 according to the first embodiment.

That the above general formula (1) is, when designing the planar shape of the laminated body 43 to the aspect ratio A _min which takes a minimum value E _min, nonaqueous becomes the highest heat efficiency of electrolyte secondary battery, a nonaqueous electrolyte secondary The maximum temperature on the surface of the battery is the lowest. The aspect ratio L1 / L2 that takes the minimum value E _min is 1.9. The positive electrode terminal 26 and the negative electrode terminal 36 are disposed at the focal position of the stacked body 43 when the aspect ratio A _min takes the minimum value E _min .

The aspect ratio of the laminate 43 is not limited to this case, and is preferably in the range of 0.4 to 1.6 times the aspect ratio A _min that takes the minimum value E _min. More preferably, it is in the range of not less than twice and not more than 1.2 times. Specifically, the aspect ratio L1 / L2 is preferably 0.8 or more and 3.0 or less, and more preferably 1.2 or more and 2.2 or less.

  As described above, according to the nonaqueous electrolyte secondary battery according to the fourth embodiment, the exhaust heat efficiency in the in-plane direction of the nonaqueous electrolyte secondary battery can be increased. As a result, the maximum temperature of the surface of the nonaqueous electrolyte secondary battery can be lowered.

[Method for producing non-aqueous electrolyte secondary battery]
The manufacturing method of the nonaqueous electrolyte secondary battery 100 can be manufactured by a known method except that the attachment positions of the positive electrode terminal 26 and the negative electrode terminal 36 are set.

  First, the positive electrode 20 and the negative electrode 30 are produced. The positive electrode 20 and the negative electrode 30 differ only in the substance used as an active material, and can be produced by the same manufacturing method.

  A positive electrode active material, a binder, and a solvent are mixed to prepare a paint. You may add a conductive support agent further as needed. As the solvent, for example, water, N-methyl-2-pyrrolidone, N, N-dimethylformamide or the like can be used. The constituent ratio of the positive electrode active material, the conductive additive, and the binder is preferably 80 wt% to 98 wt%: 0.1 wt% to 10 wt%: 0.1 wt% to 10 wt% in terms of mass ratio. These mass ratios are adjusted so as to be 100 wt% as a whole.

  The mixing method of these components constituting the paint is not particularly limited, and the mixing order is not particularly limited. The paint is applied to the positive electrode current collector. There is no restriction | limiting in particular as an application | coating method, The method employ | adopted when producing an electrode normally can be used. Examples thereof include a slit die coating method and a doctor blade method. Similarly, for the negative electrode, a paint is applied on the negative electrode current collector.

  Subsequently, the solvent in the paint applied on the positive electrode current collector and the negative electrode current collector is removed. The removal method is not particularly limited. For example, the positive electrode current collector and the negative electrode current collector to which the paint is applied may be dried in an atmosphere of 80 ° C. to 150 ° C. Then, the positive electrode 20 and the negative electrode 30 are completed.

  Then, the positive electrode 20, the negative electrode 30, and the separator 10 are stacked so that the separator 10 is between the positive electrode 20 and the negative electrode 30 to form a stacked body 40.

  The positive electrode terminal 26 and the negative electrode terminal 36 may be connected after the stacked body 40 is laminated, or the positive electrode terminal 26 and the negative electrode terminal 36 may be provided in advance on the positive electrode current collector and the negative electrode current collector.

  As shown in FIG. 3 and FIG. 4, when the positive electrode terminal 26 and the negative electrode terminal 36 are connected to any one side of the surface, the positive electrode current collector and the negative electrode current collector in which the positive electrode terminal 26 and the negative electrode terminal 36 are integrated. It is preferable to use a body.

  On the other hand, as shown in FIGS. 5 and 7, when the positive electrode terminal 26 and the negative electrode terminal 36 penetrate in the stacking direction, a through hole is provided in the manufactured laminate 40, and the positive electrode terminal 26 and the negative electrode 26 are provided in the through hole. The terminal 36 is inserted.

  Finally, the laminated body 40 is sealed in the exterior body 50. The nonaqueous electrolytic solution may be injected into the outer package 50, or the laminate 40 may be impregnated with the nonaqueous electrolytic solution. And heat etc. are added to the exterior body 50, it seals by laminating and the nonaqueous electrolyte secondary battery 100 is produced.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the configurations and combinations of the embodiments in the embodiments are examples, and the addition and the omission of the configurations are within the scope not departing from the gist of the present invention. , Substitutions, and other changes are possible.

"Example 1"
In Example 1, as shown in FIG. 3, when the planar shape of the laminate is rectangular and the positive electrode terminal and the negative electrode terminal are connected to one side surface of the laminate, respectively, the aspect ratio is changed and overcharging is performed. The difference in the maximum temperature on the surface of the nonaqueous electrolyte secondary battery was measured.

(Example 1-1)
First, a positive electrode was produced. As the positive electrode, a positive electrode active material was coated on an aluminum foil (thickness 12 μm, thermal conductivity 237.5 W / mK) to prepare a positive electrode active material layer. The positive electrode active material layer is composed of 90 parts by mass of LiNi _0.8 Co _0.15 Al _0.05 O ₂ (active material), 6 parts by mass of carbon powder (conductive aid), and 4 parts by mass of polyvinylidene fluoride. (PVDF, binder).

  Similarly, a negative electrode was produced. As the negative electrode, a negative electrode active material was coated on a copper foil (thickness 11 μm, thermal conductivity 400 W / mK) to prepare a negative electrode active material layer. The negative electrode active material layer has 87 parts by mass of mesophase carbon microbeads (MCMB, active material), 3 parts by mass of carbon powder (conductive aid), and 10 parts by mass of PVDF.

  Further, a porous polyethylene having a thickness of 12 μm was prepared as a separator. And 10 positive electrodes, 11 negative electrodes, and 20 separators were laminated | stacked so that a separator might be between a positive electrode and a negative electrode, and the laminated body was produced.

  The laminate has a rectangular shape, the length L1 in the direction in which the positive electrode terminal and the negative electrode terminal extend is 70.99 mm, and the length L2 in the direction orthogonal to the direction in which the positive electrode terminal and the negative electrode terminal extend is 17.75 mm. It was. The aspect ratio L1 / L2 at this time was 4.0. The positive electrode terminal and the negative electrode terminal were provided at the midpoint between the center line C and the end in the y direction.

And it enclosed with the non-aqueous electrolyte in the exterior body which consists of an aluminum laminate film, and produced the non-aqueous electrolyte secondary battery. The non-aqueous electrolyte is 1.0 M (mol / L) as a lithium salt in a solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are in a volume ratio of 3: 4: 3. ) To which LiPF ₆ was added.

  Next, with respect to the produced nonaqueous electrolyte secondary battery, using a secondary battery charge / discharge test apparatus, constant current / constant voltage charge was performed up to 4.2V, constant current discharge was performed up to 2.5V, and the battery capacity was calculated. . The calculated battery capacity was charged at a constant current and a constant voltage up to 10 V at a current equivalent to 3 C for 1 hour, and this was used as an overcharge test. The temperature of the battery surface at this time was measured and the maximum temperature was recorded. The in-plane temperature was measured at a total of 16 locations, 4 locations in the x direction and 4 locations in the y direction.

  Moreover, about the non-aqueous-electrolyte secondary battery designed on the same conditions, the surface temperature distribution when an overcharge test was assumed was calculated | required by the simulation which assumed the overcharge state. The results are shown in Table 1 and FIG. From the simulation results and the actual measurement values, it was confirmed that the position showing the maximum temperature on the surface of the non-aqueous electrolyte secondary battery had a correlation with each other, and the simulation was likely.

(Examples 1-2 to 1-6, Comparative Examples 1-1 to 1-3)
Examples 1-2 to 1-6 and Comparative Examples 1-1 to 1-3 differ from Example 1-1 in that the shape of the laminate is changed and the aspect ratio of the laminate is changed. The other conditions were the same as in Example 1-1, and the maximum temperature of the surface of the nonaqueous electrolyte secondary battery was measured by simulation. The results are shown in Table 1 and FIG. In Table 1, A / A _min means a value obtained by dividing the aspect ratio A of the laminate by the aspect ratio A _min when the integrated value takes the minimum value.

As shown in Table 1 and FIG. 8, when the aspect ratio L1 / L2 is 4.0 (Example 1-1), the value E represented by the general formula (1) is a minimum value. The surface temperature during overcharge if A / A _min is in the range of 0.6 to 2.8, the temperature difference between the surface temperatures of Examples 1-1 that the integrated value takes a minimum value within 2 ℃ there were. The surface temperature during overcharge if A / A _min is in the range of 0.8 to 1.7, the temperature difference between the surface temperatures of Examples 1-1 that the integrated value takes a minimum value is within 1 ℃ there were. That is, the maximum temperature of the surface of the nonaqueous electrolyte secondary battery was sufficiently low even when the aspect ratio changed to some extent from the minimum aspect ratio.

"Example 2"
In Example 2, as shown in FIG. 4, when the planar shape of the laminate is rectangular and the positive electrode terminal and the negative electrode terminal are respectively connected to the opposite side surfaces of the laminate, the aspect ratio is changed and the nonaqueous electrolyte 2 is changed. The difference in the maximum temperature on the surface of the secondary battery was measured. The positive electrode terminal and the negative electrode terminal were provided at midpoints in the direction intersecting with the direction in which the positive electrode terminal and the negative electrode terminal extend when the laminate was viewed in plan.

(Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-4)
In Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4, the shape of the laminate was changed, and the aspect ratio of the laminate was changed. The results are shown in Table 2 and FIG. In Table 2, L1 is the length in the direction in which the positive electrode terminal and negative electrode terminal of the laminate extend, L2 is the length in the direction orthogonal to the direction in which the positive electrode terminal and negative electrode terminal extend, and L1 / L2 is the aspect. Is the ratio.

As shown in Table 2 and FIG. 9, when the aspect ratio L1 / L2 is 1.0 (Example 2-3), the value E represented by the general formula (1) is a minimum value. The surface temperature during overcharge when A / A _min is in the range of 0.6 to 2.1 has a temperature difference within 2 ° C. from the surface temperature of Example 2-3 in which the integral value is a minimum value. there were. The surface temperature during overcharge if _{A / A min} is in the range of 0.75 to 1.75, the temperature difference between the surface temperature of the Example 2-3 in which the integral value becomes the minima is within 1 ℃ there were. That is, the maximum temperature of the surface of the nonaqueous electrolyte secondary battery was sufficiently low even when the aspect ratio changed to some extent from the minimum aspect ratio.

"Example 3"
In Example 3, as shown in FIG. 5, when the planar shape of the laminate is rectangular and the positive electrode terminal and the negative electrode terminal are respectively connected in the plane of the laminate, the non-aqueous electrolyte secondary is changed by changing the aspect ratio. The difference in the maximum temperature of the battery surface was measured. The positive electrode terminal and the negative electrode terminal were provided at the center of two regions separated by a center line in the major axis direction when the laminate was viewed in plan.

(Examples 3-1 to 3-10, Comparative example 3-1)
In Examples 3-1 to 3-10 and Comparative Example 3-1, the shape of the laminate was changed, and the aspect ratio of the laminate was changed. The results are shown in Table 3 and FIG. In Table 3, L1 is the length in the major axis direction of the laminate, L2 is the length in the minor axis direction, and L1 / L2 is the aspect ratio.

As shown in Table 3 and FIG. 10, when the aspect ratio L1 / L2 is 2.0 (Example 3-6), the value E represented by the general formula (1) is a minimum value. Further, the surface temperature during overcharge when A / A _min is in the range of 0.5 to 1.5 is within 2 ° C. of the temperature difference from the surface temperature of Example 3-6 in which the integral value takes the minimum value. there were. Further, the surface temperature during overcharge when A / A _min is in the range of 0.7 to 1.3 has a temperature difference within 1 ° C. from the surface temperature of Example 3-6 in which the integral value is a minimum value. there were. That is, the maximum temperature of the surface of the nonaqueous electrolyte secondary battery was sufficiently low even when the aspect ratio changed to some extent from the minimum aspect ratio.

Example 4
In Example 4, as shown in FIG. 7, when the planar shape of the laminate is an ellipse and the positive electrode terminal and the negative electrode terminal are respectively connected in the plane of the laminate, the aspect ratio is changed and the nonaqueous electrolyte secondary is changed. The difference in the maximum temperature of the battery surface was measured. The positive electrode terminal and the negative electrode terminal passed through the center line in the short axis direction when the laminate was viewed in plan, and were provided at equal intervals across the center line in the long axis direction.

(Examples 4-1 to 4-11, Comparative examples 4-1 to 4-2)
In Examples 4-1 to 4-11 and Comparative Examples 4-1 to 4-2, the shape of the laminate was changed, and the aspect ratio of the laminate was changed. The results are shown in Table 4 and FIG. In Table 4, L1 is the length in the major axis direction of the laminate, L2 is the length in the minor axis direction, and L1 / L2 is the aspect ratio.

As shown in Table 4 and FIG. 11, when the aspect ratio L1 / L2 is 1.9 (Example 4-5), the value E represented by the general formula (1) is a minimum value. The surface temperature during overcharge when A / A _min is in the range of 0.4 to 1.6 has a temperature difference within 2 ° C. from the surface temperature of Example 4-5 in which the integral value is minimal. there were. Further, the surface temperature during overcharging when A / A _min is in the range of 0.6 to 1.2 has a temperature difference within 1 ° C. from the surface temperature of Example 4-5 in which the integral value is a minimum value. there were. That is, the maximum temperature of the surface of the nonaqueous electrolyte secondary battery was sufficiently low even when the aspect ratio changed to some extent from the minimum aspect ratio.

DESCRIPTION OF SYMBOLS 10 ... Separator, 20 ... Positive electrode, 22 ... Positive electrode collector, 24 ... Positive electrode active material layer, 26 ... Positive electrode terminal, 26A ... 1st end part, 26B ... 2nd end part, 30 ... Negative electrode, 32 ... Negative electrode current collector Body, 34 ... negative electrode active material layer, 36 ... negative electrode terminal, 36A ... first end, 36B ... second end, 40, 41, 42, 43 ... laminate, 50 ... outer package, 100, 102 ... non-water Electrolyte secondary battery, C ... center line

Claims (4)

One or more layers each of a positive electrode having a positive electrode current collector connected to a positive electrode terminal, a negative electrode having a negative electrode current collector connected to a negative electrode terminal, and a separator disposed between the positive electrode and the negative electrode Comprising a laminate having
The positive electrode terminal and the negative electrode terminal are respectively connected to one side surface when the laminate is viewed in plan from the lamination direction,
When the area of the micro region that divides the laminate in plan view is dS, and the distance from the center of gravity of the micro region to the connection center of the positive terminal or the terminal closer to the negative terminal is r,
The aspect ratio of the laminate is in the range of 0.6 to 2.8 times the aspect ratio A _{min in} which the following general formula (1) takes the minimum value E _min. Next battery.

One or more layers each of a positive electrode having a positive electrode current collector connected to a positive electrode terminal, a negative electrode having a negative electrode current collector connected to a negative electrode terminal, and a separator disposed between the positive electrode and the negative electrode Comprising a laminate having
The positive electrode terminal and the negative electrode terminal are respectively connected to different side surfaces of the laminate when the laminate is viewed in plan from the lamination direction,
When the area of the micro region that divides the laminate in plan view is dS, and the distance from the center of gravity of the micro region to the connection center of the positive terminal or the terminal closer to the negative terminal is r,
The aspect ratio of the laminate is in the range of 0.6 to 2.1 times the aspect ratio A _{min in} which the following general formula (1) takes the minimum value E _min. Next battery.

One or more layers each of a positive electrode having a positive electrode current collector connected to a positive electrode terminal, a negative electrode having a negative electrode current collector connected to a negative electrode terminal, and a separator disposed between the positive electrode and the negative electrode Comprising a laminate having
The positive electrode terminal and the negative electrode terminal are respectively connected in the plane of the laminate when the laminate is viewed in plan from the lamination direction,
When the area of the micro region that divides the laminate in plan view is dS, and the distance from the center of gravity of the micro region to the connection center of the positive terminal or the terminal closer to the negative terminal is r,
The aspect ratio of the laminate is in the range of 0.4 to 1.6 times the aspect ratio A _{min in} which the following general formula (1) takes the minimum value E _min. Next battery.

The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the aspect ratio of the laminate is an aspect ratio A _min in which the general formula (1) takes a minimum value E _min .

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