JP2013004305A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery capable of properly actuate a current interruption mechanism.SOLUTION: A secondary battery includes: an electrode body equipped with a positive electrode 10 and a negative electrode; a battery case in which the electrode body is housed; micro capsules 62 disposed inside the battery case; gas generations materials 64, each of which is internally encapsulated, and which generate gas when temperature in the battery case is risen; and a current interruption mechanism which is actuated when internal pressure of the battery case is increased by gas generation from the gas generation materials 64.

Description

  The present invention relates to a secondary battery, and more particularly to a secondary battery provided with a current interruption mechanism.

  In recent years, lithium secondary batteries, nickel metal hydride batteries and other secondary batteries (storage batteries) have become increasingly important as power sources for mounting on vehicles or as power sources for personal computers and portable terminals. In particular, a lithium secondary battery that is lightweight and has a high energy density is preferably used as a high-output power source for mounting on a vehicle. As a typical structure of such a lithium secondary battery, there is a sealed lithium secondary battery (sealed battery) in which a battery case containing an electrode body and an electrolyte is sealed. Patent Documents 1 and 2 are disclosed as conventional techniques related to secondary batteries of this type.

  By the way, when this type of lithium secondary battery is charged, an overcurrent may be supplied to the battery, resulting in overcharging. In order to stop the progress of such overcharge, a battery having a current cutoff mechanism that cuts off a charging current when a gas pressure inside the battery (internal pressure of the battery case) exceeds a predetermined value has been proposed. In general, when a battery is overcharged, a nonaqueous solvent or the like of the electrolytic solution is electrolyzed to generate gas and heat. The current interruption mechanism can prevent further overcharge by detecting this gas and cutting the charging path of the battery.

JP 2003-257479 A JP 2004-119132 A

  Patent Document 1 proposes that a compound (for example, cyclohexylbenzene) having an oxidation potential lower than that of the nonaqueous solvent of the electrolytic solution is added as an additive to the electrolytic solution. Such an additive is quickly oxidized and decomposed at the positive electrode to generate gas when the battery is overcharged. By generating an increase in the internal pressure of the battery with the generated gas, the current interruption mechanism can be operated more quickly. However, even if an additive such as cyclohexylbenzene (CHB) produces an effective increase in internal pressure during overcharge and quickly activates the current interruption mechanism, it functions as a resistance component of the battery under normal conditions. It was a factor of lowering (typically increasing electrical resistance). The present invention aims to solve the above problems.

  A secondary battery according to the present invention (hereinafter also simply referred to as “battery”) includes an electrode body including a positive electrode and a negative electrode, and a battery case that houses the electrode body. The secondary battery includes a microcapsule disposed inside the battery case, a gas generating material that is included in the microcapsule and generates gas when the temperature in the battery case rises, and the battery case. A current interrupt mechanism that operates when the internal pressure rises due to gas generation from the gas generating material.

  Here, in the present specification, the term “microcapsule” means that the diameter of the inclusion covered with a film is on the order of micrometers (that is, the diameter is 1 μm to 1000 μm) or smaller (that is, the order of nanometers where the diameter is 1 μm or less). The microcapsules can contain various substances (liquid, solid).

  According to the present invention, in a secondary battery equipped with a current interruption mechanism that operates due to an increase in the internal pressure of the battery, the microcapsule is disposed in the battery case, and gas is generated when the temperature rises in the microcapsule. By encapsulating the generating material, when the battery temperature rises during overcharging, gas is generated from the gas generating material in the microcapsule, and the microcapsule bursts, thereby increasing the internal pressure of the battery case at once. Thereby, a current interruption mechanism can be operated appropriately. Further, since the gas generating material is enclosed in the microcapsule during normal operation (that is, while the battery is used in the normal charge / discharge range), the gas generating material and other battery constituent materials (for example, an electrolyte) Contact with is avoided. Therefore, the influence (for example, a fall of output characteristics, cycle deterioration, etc.) by a gas generating material coming into contact with other battery constituent materials can be avoided. That is, according to the present invention, it is possible to provide a secondary battery that can accurately operate the current interrupting mechanism during overcharging while maintaining good battery performance under normal conditions.

  The gas generating material included in the microcapsules can be used without particular limitation as long as it can generate gas when the temperature in the battery case rises. For example, a liquid having a boiling point of 70 ° C. or higher can be preferably used. In this case, when the battery temperature reaches 70 ° C. or more, the microcapsule bursts due to the vaporization of the liquid, and the internal pressure of the battery case rises at once. Thereby, a current interruption mechanism can be operated appropriately. Further, since the heat is taken away from the surroundings when the liquid is vaporized, there is an effect of cooling the high temperature portion of the battery. Such a liquid is preferably a flame-retardant or non-flammable liquid. Examples of the liquid include a fluorinated liquid. Here, the fluorinated liquid refers to a solvent (typically an organic solvent) containing fluorine (F) as a constituent element. Examples of the fluorinated liquid include 1,1,2,2,3,4,4-heptafluorocyclopentane (boiling point 82.5 ° C.), 1,1,2,2,3,4,4-octafluoro. Examples thereof include cyclopentane (boiling point 79 ° C.) and the like. Such liquid may be used individually by 1 type, and may be used in combination of 2 or more type. As a commercial product of a fluorinated liquid that can be preferably used in the technology disclosed herein, “Zeorolla H (registered trademark)” series manufactured by Nippon Zeon Co., Ltd. is exemplified.

  The gas generating material contained in the microcapsule is not limited to the liquid and may be a solid material. For example, an adsorbent that adsorbs gas molecules can be preferably used. Examples of the adsorbent include zeolite. An adsorbent that adsorbs gas molecules may be covered with a microcapsule material, and gas may be generated by desorbing gas molecules from the adsorbent when the temperature in the battery case rises. In this case, there is an advantage that the microcapsules are not easily broken during the operation (process) of arranging the microcapsules at a predetermined position in the battery case.

  In a preferable aspect of the secondary battery disclosed herein, the microcapsule includes an overcharge inhibitor (a substance that acts as a resistor of an overcharge current during overcharge) together with the gas generating material. Yes. By including the overcharge inhibitor in the microcapsule together with the gas generating material in this way, it is possible to suppress the overcharge current from flowing by the overcharge inhibitor when the microcapsule is ruptured during overcharge. Further, since the overcharge inhibitor is encapsulated in the microcapsules during normal operation, contact between the overcharge inhibitor and another battery constituent material (for example, an electrolytic solution) can be avoided. Therefore, it is possible to avoid an adverse effect (for example, a decrease in output characteristics or cycle deterioration) caused by the overcharge inhibitor coming into contact with other battery constituent materials.

  The overcharge inhibitor contained in the microcapsule can be used without particular limitation as long as it acts as a charge current resistor during overcharge. For example, a compound having an oxidation potential lower than the decomposition potential of the electrolytic solution can be preferably used. Preferable examples of the above compound include alkylbenzene derivatives and cycloalkylbenzene derivatives. Examples of the alkylbenzene derivatives include cumene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene, 1-methylpropylbenzene, 1,3-bis (1-methylpropyl) benzene, 1,4-bis (1-methylpropyl). ) Benzene and the like. Examples of the cycloalkylbenzene derivative include cyclohexylbenzene (CHB) and cyclopentylbenzene. Such compounds may be used singly or in combination of two or more. When the battery is overcharged, the compound is rapidly oxidized and decomposed at the positive electrode (typically, the surface of the positive electrode active material) to form a high-resistance film (polymer) on the active material surface. This film acts as a resistor for charging current. In addition, the said compound generate | occur | produces gas by said oxidative decomposition reaction. That is, the above compound also functions as a gas generating material that generates gas by oxidative decomposition. For this reason, in combination with the generation of gas from the gas generating material described above, it is possible to efficiently generate more gas in the battery case and operate the current interrupting mechanism accurately.

  In a preferable aspect of the secondary battery disclosed herein, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, and at least a part of the microcapsules is held in the positive electrode active material layer. ing. Since the oxidative decomposition reaction of the overcharge inhibitor such as CHB described above mainly occurs on the surface of the positive electrode active material, when the microcapsule contains the overcharge inhibitor compound described above, the microcapsule is held in the positive electrode active material layer. The embodiment described above can be preferably adopted.

  In a preferable aspect of the secondary battery disclosed herein, the electrode body includes a separator that separates the positive electrode and the negative electrode, and the microcapsule is held by the separator. By adopting a configuration in which the microcapsules are held in a separator, there is an advantage that rupture during coating and drying can be prevented. That is, when holding the microcapsule in the positive electrode active material layer, it is necessary to add the microcapsule to the positive electrode active material layer forming paste, apply the positive electrode active material layer forming paste to the positive electrode current collector, and dry it. However, there is a possibility that the microcapsule may burst. On the other hand, in the case where the microcapsules are held in the separator, it is only necessary to spread the microcapsules on the separator and put them in the separator holes, and it is possible to prevent rupture during coating and drying as described above.

  In a preferred aspect of the secondary battery disclosed herein, the electrode body is a wound electrode body in which the sheet-like positive electrode and the sheet-like negative electrode are laminated and wound, The microcapsule is disposed at the center of winding of the wound electrode body. Since the winding center part of the wound electrode body is more susceptible to heat than the surrounding part (for example, the outer peripheral part of the wound electrode body), the temperature is likely to rise. Therefore, the high temperature portion of the battery can be more effectively cooled by arranging the microcapsule at the winding center portion of the wound electrode body.

  In a preferable aspect of the secondary battery disclosed herein, a positive electrode terminal and a negative electrode terminal are electrically connected to the positive electrode and the negative electrode of the electrode body, respectively. The current interruption mechanism includes a conductive member that forms a conductive path from at least one of the positive electrode and negative electrode terminals to the electrode body, and the internal pressure of the battery case increases due to gas generation from the gas generating material. Further, the conductive member is deformed to cut the conductive path. By cutting the conductive path accompanied by such deformation of the conductive member, the charging current can be appropriately cut off.

  Any of the secondary batteries disclosed herein has a performance suitable as a secondary battery mounted on a vehicle because the current interruption mechanism can be reliably operated during overcharge without adversely affecting battery characteristics. Therefore, according to this invention, a vehicle provided with the secondary battery disclosed here is provided. In particular, a vehicle (for example, an automobile) including the secondary battery as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is provided.

It is a schematic diagram which shows an example of the structure of the lithium secondary battery which concerns on one Embodiment of this invention. It is a schematic diagram which shows the winding electrode body of the lithium secondary battery which concerns on one Embodiment of this invention. It is a schematic diagram which shows the III-III cross section in FIG. It is a schematic diagram which shows the principal part cross section of the wound electrode body which concerns on one Embodiment of this invention. (A)-(c) is a schematic diagram which shows the principal part cross section of the wound electrode body which concerns on one Embodiment of this invention. It is a schematic diagram which shows the principal part cross section of the wound electrode body which concerns on one Embodiment of this invention. It is a figure which shows the structure of the winding electrode body which concerns on one Embodiment of this invention, (a) Side view and (b) Front view. It is a side view which shows the vehicle carrying the battery which concerns on one Embodiment of this invention.

  Embodiments according to the present invention will be described below with reference to the drawings. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, the configuration and manufacturing method of the positive electrode active material and the negative electrode active material, the configuration and manufacturing method of the separator and the electrolyte, the battery Other general technologies related to battery construction, etc.) can be grasped as design matters of those skilled in the art based on the prior art in this field.

  Although it is not intended to be particularly limited, in the following, a flatly wound electrode body (wound electrode body) and a nonaqueous electrolyte solution are accommodated in a flat box-shaped (cuboid shape) container. The present invention will be described in detail by taking a lithium secondary battery as an example. Moreover, in the following drawings, the same code | symbol is attached | subjected to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted or simplified.

<First Embodiment>
A schematic configuration of a lithium secondary battery according to an embodiment of the present invention is shown in FIGS. FIG. 1 shows a lithium secondary battery 100. As shown in FIG. 1, the lithium secondary battery 100 includes a wound electrode body 80 and a battery case 50. FIG. 2 is a view showing a wound electrode body 80. FIG. 3 shows a III-III cross section in FIG.

  This lithium secondary battery 100 includes a long positive electrode sheet 10 and a long negative electrode sheet 20 that are wound flatly via long separator sheets 40A and 40B (winding). The electrode body 80 is configured to be housed in a battery case 50 having a shape (flat box shape) capable of housing the wound electrode body 80 together with a non-aqueous electrolyte (not shown).

  The battery case 50 includes a flat cuboid case main body 52 having an open upper end, and a lid 54 that closes the opening. As a material constituting the battery case 50, a metal material such as aluminum or steel is preferably used (in this embodiment, aluminum). Or the battery case 50 formed by shape | molding resin materials, such as a polyphenylene sulfide (PPS) and a polyimide resin, may be sufficient. On the upper surface (that is, the lid 54) of the battery case 50, a positive electrode terminal 70 that is electrically connected to the positive electrode of the wound electrode body 80 and a negative electrode terminal 72 that is electrically connected to the negative electrode 20 of the electrode body 80. Is provided.

  Inside the battery case 50, a current interrupting mechanism 30 that is activated by an increase in the internal pressure of the battery case is provided. When the internal pressure of the battery case 50 rises due to gas generation from a gas generating material, which will be described later, the current interrupting mechanism 30 interrupts the charging current by cutting a conductive path from at least one electrode terminal to the electrode body 80. Configured to get. In this embodiment, the current interruption mechanism 30 is provided between the positive electrode terminal 70 fixed to the lid body 54 and the electrode body 80, and reaches from the positive electrode terminal 70 to the electrode body 80 when the internal pressure of the battery case 50 rises. The conductive path is configured to be cut.

  The current interruption mechanism 30 may include conduction members 32 and 34, for example. In this embodiment, the conduction members 32 and 34 include a first member 32 and a second member 34. When the internal pressure of the battery case 50 rises, at least one of the first member 32 and the second member 34 (here, the first member 32) is deformed and separated from the other so as to cut the conductive path. It is configured. In this embodiment, the first member 32 is a deformed metal plate 32, and the second member 34 is a connection metal plate 34 joined to the deformed metal plate 32. The deformed metal plate (first member) 32 has an arch shape in which a central portion is curved downward, and a peripheral portion thereof is connected to the lower surface of the positive electrode terminal 70 via a current collecting lead terminal 35. Further, the tip of the curved portion 33 of the deformed metal plate 32 is joined to the upper surface of the connection metal plate 34. A positive current collector plate 74 is bonded to the lower surface (back surface) of the connection metal plate 34, and the positive current collector plate 74 is connected to the positive electrode sheet 10 of the electrode body 80. In this way, a conductive path from the positive electrode terminal 70 to the electrode body 80 is formed.

  The current interrupt mechanism 30 includes an insulating case 38 made of plastic or the like. The insulating case 38 is provided so as to surround the deformed metal plate 32, and hermetically seals the upper surface of the deformed metal plate 32. The internal pressure of the battery case 50 does not act on the upper surface of the hermetically sealed curved portion 33. The insulating case 38 has an opening into which the curved portion 33 of the deformed metal plate 32 is fitted, and the lower surface of the curved portion 33 is exposed from the opening to the inside of the battery case 50. The internal pressure of the battery case 50 acts on the lower surface of the curved portion 33 exposed inside the battery case 50.

  In the current interrupt mechanism 30 having such a configuration, when the internal pressure of the battery case 50 increases, the internal pressure acts on the lower surface of the curved portion 33 of the deformed metal plate 32, and the curved portion 33 curved downward is pushed upward. The upward pushing force of the curved portion 33 increases as the internal pressure of the battery case 50 increases. When the internal pressure of the battery case 50 exceeds the set pressure, the curved portion 33 is turned upside down and deformed so as to bend upward. Due to the deformation of the curved portion 33, the joint point 36 between the deformed metal plate 32 and the connection metal plate 34 is cut. As a result, the conductive path from the positive electrode terminal 70 to the electrode body 80 is cut, and the charging current is cut off. In this embodiment, the conductive members 32 and 34 that are deformed when the internal pressure is increased are illustrated as being divided into the first member 32 and the second member 34, but the present invention is not limited to this. For example, the conducting member may be a single member. The current interrupt mechanism 30 is not limited to the positive terminal 70 side, and may be provided on the negative terminal 72 side. Moreover, the electric current interruption mechanism 30 is not limited to the mechanical cutting | disconnection accompanied with a deformation | transformation of the deformation | transformation metal plate 32 mentioned above. For example, an external circuit that detects the internal pressure of the battery case 50 with a sensor and cuts off the charging current when the internal pressure detected by the sensor exceeds a set pressure may be provided as the current cutoff mechanism.

  Inside the battery case 50, a flat wound electrode body 80 is accommodated together with a non-aqueous electrolyte (not shown). The wound electrode body 80 according to the present embodiment is the same as the wound electrode body of a normal lithium secondary battery except that the wound electrode body 80 is constructed using a positive electrode sheet holding microcapsules as described later. In addition, as shown in FIG. 2, a long (strip-shaped) sheet structure (sheet-shaped electrode body) 82 is provided in a stage before assembling the wound electrode body 80.

  The positive electrode sheet 10 has a structure in which a positive electrode active material layer 14 containing a positive electrode active material is held on both surfaces of a positive electrode current collector (hereinafter referred to as “positive electrode current collector foil”) 12 made of a long metal foil. is doing. However, the positive electrode active material layer 14 is not attached to one side edge (the left side edge portion in the drawing) along the widthwise end of the positive electrode sheet 10, and the positive electrode current collector 12 is exposed with a certain width. The positive electrode active material layer non-formed part 16 is formed.

  Similarly to the positive electrode sheet 10, the negative electrode sheet 20 holds a negative electrode active material layer 24 containing a negative electrode active material on both sides of a long sheet-like foil-shaped negative electrode current collector (hereinafter referred to as “negative electrode current collector foil”) 22. Has a structured. However, the negative electrode active material layer 24 is not attached to one side edge (the right side edge portion in the drawing) along the widthwise edge of the negative electrode sheet 20, and the negative electrode current collector 22 is exposed with a certain width. The negative electrode active material layer non-forming part 26 is formed.

  When producing the wound electrode body 80, the positive electrode sheet 10 and the negative electrode sheet 20 are laminated via the separator sheets 40A and 40B. At this time, the positive electrode sheet 10 and the negative electrode active material layer non-formed portion 16 of the positive electrode sheet 10 and the negative electrode active material layer non-formed portion 26 of the negative electrode sheet 20 protrude from both sides in the width direction of the separator sheets 4040A and 40B. The negative electrode sheet 20 is overlaid 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, whereby a flat wound electrode body 80 can be produced. Instead of rolling the sheet laminate (sheet-like electrode body) in this way and then flattening it, for example, the laminate is initially rolled into a flat shape (substantially oval, elliptical, etc.). Also good.

  In the central portion of the wound electrode body 80 in the winding axis direction, a wound core portion 82 (that is, the positive electrode active material layer 14 of the positive electrode sheet 10, the negative electrode active material layer 24 of the negative electrode sheet 20, and the separator sheets 40A and 40B). A densely stacked portion) is formed. In addition, at both ends of the wound electrode body 80 in the winding axis direction, part of the electrode active material layer non-formed portions 16 and 26 of the positive electrode sheet 10 and the negative electrode sheet 20 protrude from the wound core portion 82 to the outside. ing. A positive electrode lead terminal 74 and a negative electrode lead terminal 76 are attached to the positive electrode side protruding portion 84 and the negative electrode side protruding portion 86, respectively, and are electrically connected to the positive electrode terminal 70 and the negative electrode terminal 72, respectively.

  The constituent elements of the wound electrode body 80 may be the same as those of the wound electrode body of the conventional lithium secondary battery except for the positive electrode sheet 10, and are not particularly limited. For example, the negative electrode sheet 20 can be formed by applying a negative electrode active material layer 24 mainly composed of a negative electrode active material for a lithium secondary battery on a long negative electrode current collector 22. For the negative electrode current collector 22, a copper foil or other metal foil suitable for the negative electrode is preferably used. As the negative electrode active material, one or more of materials conventionally used in lithium secondary batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium-containing transition metal oxides and transition metal nitrides.

  The positive electrode sheet 10 can be formed by applying a positive electrode active material layer 14 mainly composed of a positive electrode active material for a lithium secondary battery on a long positive electrode current collector 12. For the positive electrode current collector 12, an aluminum foil or other metal foil suitable for the positive electrode is preferably used.

As the positive electrode active material, one type or two or more types of materials conventionally used in lithium secondary batteries can be used without any particular limitation. Preferred applications of the technology disclosed herein include lithium and transition metals such as lithium nickel oxide (eg, LiNiO ₂ ), lithium cobalt oxide (eg, LiCoO ₂ ), and lithium manganese oxide (eg, LiMn ₂ O ₄ ). And a positive electrode active material mainly containing an oxide (lithium transition metal oxide) containing the element as a constituent metal element. Among them, a positive electrode active material (typically, substantially a lithium nickel cobalt manganese composite oxide substantially composed of lithium nickel cobalt manganese composite oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ). Application to a positive electrode active material comprising:

  Here, the lithium nickel cobalt manganese composite oxide is an oxide having only Li, Ni, Co and Mn as constituent metal elements, and at least one other metal element in addition to Li, Ni, Co and Mn (that is, , Li, Ni, Co, and transition metal elements other than Mn and / or oxides containing typical metal elements). The metal element is, for example, one or two selected from the group consisting of Al, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. It can be more than a seed element. The same applies to lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide.

  As such a lithium transition metal oxide (typically in particulate form), for example, a lithium transition metal oxide powder prepared by a conventionally known method can be used as it is. For example, lithium transition metal oxide powder substantially composed of secondary particles having an average particle diameter in the range of about 1 μm to 25 μm can be preferably used as the positive electrode active material.

  In addition to the positive electrode active material, the positive electrode active material layer 14 can contain one or two or more materials that can be used as a constituent component of the positive electrode active material layer in a general lithium secondary battery, if necessary. An example of such a material is a conductive material. As the conductive material, a carbon material such as carbon powder or carbon fiber is preferably used. Alternatively, conductive metal powder such as nickel powder may be used. In addition, examples of materials that can be used as components of the positive electrode active material layer include various polymer materials that can function as binders for the positive electrode active material.

  Although not particularly limited, the ratio of the positive electrode active material to the entire positive electrode active material layer is preferably about 50% by mass or more (typically 50 to 95% by mass), preferably about 75 to 90% by mass. Preferably there is. In the positive electrode active material layer having a composition containing a conductive material, the proportion of the conductive material in the positive electrode active material layer can be, for example, 3 to 25% by mass, and preferably about 3 to 15% by mass. In addition, when a positive electrode active material layer forming component (for example, a polymer material) other than the positive electrode active material and the conductive material is contained, the total content of these optional components is preferably about 7% by mass or less, and about 5% by mass. The following (for example, about 1 to 5% by mass) is preferable.

  As a method for forming the positive electrode active material layer 14, a positive electrode active material (typically granular) and other positive electrode active material layer forming components are used in an appropriate solvent (for example, a nonaqueous solvent such as N-methylpyrrolidone (NMP)). A method in which the positive electrode active material layer forming paste dispersed in is applied in a strip shape on one or both surfaces (here, both surfaces) of the positive electrode current collector 12 and dried can be preferably employed. After drying the positive electrode active material layer forming paste, an appropriate press treatment (for example, various conventionally known press methods such as a roll press method, a flat plate press method, etc. can be employed) is carried out, whereby the positive electrode active material layer The thickness and density of 14 can be adjusted.

  As the separator sheets 40A and 40B disposed between the positive and negative electrode sheets 10 and 20, various porous sheets similar to the separator of a general lithium secondary battery including a wound electrode body can be used. Preferable examples include porous resin sheets (films, nonwoven fabrics, etc.) made of polyolefin resins such as polyethylene (PE) and polypropylene (PP). Such a porous resin sheet may have a single layer structure, or may have a two or more layers structure (for example, a three-layer structure in which PE layers are laminated on both sides of a PP layer). Although it is not particularly limited, preferred porous sheets (typically porous resin sheets) used as the separator base material have an average pore diameter of about 0.001 μm to 30 μm and a thickness of 5 μm to 100 μm. Examples of the porous resin sheet are (more preferably 10 μm to 30 μm). The air efficiency (porosity) of the porous sheet can be, for example, about 20 to 90% by volume (preferably 30 to 80% by volume).

  Subsequently, the positive electrode sheet 10 according to the present embodiment will be described in detail with reference to FIG. FIG. 4 is a schematic cross-sectional view showing an enlarged part of a cross section along the winding axis of the wound electrode body 80 according to the present embodiment, which is formed on the positive electrode current collector 12 and one side thereof. The positive electrode active material layer 14 and the separator sheet 40A facing the positive electrode active material layer 14 are shown.

  In the lithium secondary battery according to this embodiment, as the positive electrode sheet 10 constituting the electrode body 80 accommodated in the battery case, a microcapsule including a gas generating material 64 that generates gas when the temperature in the case rises. A material 62 is held by the positive electrode active material layer 14 is used.

  The microcapsule 62 held in the positive electrode active material layer 14 has a diameter in which an inclusion is covered with an outer shell, and has a diameter of the order of micrometers (that is, a diameter of 1 μm to 1000 μm) or smaller (that is, a nanometer whose diameter is 1 μm or less). Order) fine particles. Examples of the material that can constitute the outer shell include polymers having a structure including an acrylic chain, an olefin chain, a methylene chain, a paraffin chain, and the like. Conventionally known microcapsules having such an outer shell and a method for producing the same can be applied. For example, after the inclusion of the microcapsule is added to a solvent (for example, water) and stirred and emulsified with a mixer, the outer material is added, then cooled with stirring, filtered through a suction filtration and drying process, can do.

  The microcapsule includes a gas generating material that generates gas when the temperature inside the battery case rises. Any gas generating material can be used without particular limitation as long as it can generate gas when the temperature in the battery case rises. For example, a liquid having a boiling point of 70 ° C. or higher can be preferably used. Examples of the liquid include a fluorinated liquid. Here, the fluorinated liquid refers to a solvent (typically an organic solvent) containing fluorine (F) as a constituent element. Examples of the fluorinated liquid include 1,1,2,2,3,4,4-heptafluorocyclopentane (boiling point 82.5 ° C.), 1,1,2,2,3,4,4-octafluoro. Examples thereof include cyclopentane (boiling point 79 ° C.) and the like. Such liquid may be used individually by 1 type, and may be used in combination of 2 or more type. As a commercial product of a fluorinated liquid that can be preferably used in the technology disclosed herein, “Zeorolla H (registered trademark)” series manufactured by Nippon Zeon Co., Ltd. is exemplified.

  The gas generating material contained in the microcapsule is not limited to the liquid and may be a solid material. For example, an adsorbent that adsorbs gas can be preferably used. Examples of the adsorbent include zeolite. The adsorbent adsorbing the gas may be covered with a microcapsule material, and the gas may be generated by desorbing the gas from the adsorbent when the temperature in the battery case rises. In this case, there is an advantage that the microcapsules are not easily broken during the operation (process) of arranging the microcapsules at a predetermined position in the battery case.

  The shape (outer shape) of the microcapsule is not particularly limited. From the viewpoints of volume efficiency, strength, manufacturability, and the like that enclose a gas generating material (for example, a fluorinated liquid), generally spherical microcapsules can be preferably used. In addition, the size (particle size) of the microcapsules is preferably about the same as or smaller than the thickness of the positive electrode active material layer 14. For example, it is preferable to use microcapsules having an average particle size of about 10 μm or less, more preferably about 5 μm or less, and may be about 1 μm or less. If the particle size of the microcapsule is too large, the capsule may become an obstacle and local stress may be easily applied to the constituent elements of the electrode body. On the other hand, if the particle size of the microcapsules is too small, the amount of the gas generating material included in the amount used is small and inefficient, and thus the average particle size is usually about 0.05 μm or more (for example, 0 .1 μm or more) microcapsules are preferably used. The average particle size of the microcapsules can be determined by a method known in the art, for example, measurement based on a laser diffraction scattering method, or observation with an electron microscope.

  The lithium secondary battery according to this embodiment includes the positive electrode sheet 10 in which such microcapsules 62 are held by the positive electrode active material layer 14. For example, as shown in FIG. 4, a preferred configuration example of the positive electrode sheet 10 includes a configuration in which the microcapsules 62 are embedded in the positive electrode active material layer 14 so that the capsules are held on the positive electrode sheet. In this case, since the microcapsule 62 is embedded in the positive electrode active material layer, it is possible to suppress an event that the capsule 62 falls off the positive electrode sheet 10 or is displaced in the surface direction of the positive electrode sheet due to gravity or acceleration. it can. The microcapsule 62 embedded in such a positive electrode active material layer can be produced, for example, by adding the microcapsule 62 to the positive electrode active material layer forming paste described above. The positive electrode active material layer 14 including the microcapsules 62 is formed by applying the positive electrode active material layer forming paste to the positive electrode current collector 12 and drying the paste. In this case, the drying temperature is preferably 40 ° C. or lower (preferably room temperature).

  Another preferred configuration example of the positive electrode sheet 10 is a configuration in which the capsule is held by the positive electrode sheet by entering the microcapsule into the pores of the positive electrode active material layer. The positive electrode sheet 10 includes, for example, positive electrode active material particles 18 substantially composed of secondary particles, and the positive electrode active material particles 18 are fixed to each other with a binder (not shown). Further, the positive electrode active material layer 14 has spaces (pores) 15 through which the nonaqueous electrolyte solution penetrates into the positive electrode active material layer, and the spaces (pores) 15 are fixed to each other, for example. The positive electrode active material particles 18 may be formed by voids or the like. When the microcapsules 62 enter the spaces (pores) 15, a configuration in which the capsules are held by the positive electrode sheet can be realized. According to such a configuration, the electrolytic solution and the microcapsule 62 can be brought into sufficiently good contact. In this case, it is preferable that the microcapsule has the same particle diameter as that of the positive electrode active material layer but smaller than the pore diameter.

The wound electrode body 80 including the positive electrode sheet 10 having such a configuration is accommodated in the case main body 52, and an appropriate nonaqueous electrolytic solution is disposed (injected) into the case main body 52. As the non-aqueous electrolyte accommodated in the case main body 52 together with the wound electrode body 80, the same non-aqueous electrolyte used in conventional lithium secondary batteries can be used without any particular limitation. Such a nonaqueous electrolytic solution typically has a composition in which a supporting salt is contained in a suitable nonaqueous solvent. As said non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC) etc. can be used, for example. Further, as the supporting salt, for _{example, LiPF 6, LiBF 4, LiAsF} 6, LiCF 3 can be preferably used a lithium salt of SO ₃ and the like. For example, a nonaqueous electrolytic solution in which LiPF ₆ as a supporting salt is contained at a concentration of about 1 mol / liter in a mixed solvent containing EC, EMC, and DMC at a volume ratio of 3: 4: 3 can be preferably used.

  The non-aqueous electrolyte is accommodated in the case main body 52 together with the wound electrode body 80, and the opening of the case main body 52 is sealed by welding with the lid 54 or the like, whereby the lithium secondary battery 100 according to the present embodiment. Construction (assembly) of is completed. In addition, the sealing process of the case main body 52 and the arrangement | positioning (injection) process of electrolyte solution can be performed similarly to the method currently performed by manufacture of the conventional lithium secondary battery. Thereafter, the battery is conditioned (initial charge / discharge). You may perform processes, such as degassing and a quality inspection, as needed.

  The function of the lithium secondary battery 100 according to the present embodiment will be described with reference to FIGS. As shown in FIG. 5A, a positive electrode sheet 10 having a positive electrode active material layer 14 is provided on a positive electrode current collector 12, and microcapsules 62 are held in the positive electrode active material layer 14 of the positive electrode sheet 10. . The microcapsule 62 contains a gas generating material (here, a liquid having a boiling point of 70 ° C. or higher) 64 that generates gas when the temperature in the battery case rises.

  In a battery having such a configuration, when it is normal (that is, while the battery is used in a normal charge / discharge range), a gas generating material 64 is enclosed in a microcapsule 62 as shown in FIG. Therefore, the contact between the gas generating material 64 and another battery constituent material (for example, electrolytic solution) is avoided. Therefore, it is possible to avoid an adverse effect (for example, a decrease in output characteristics or cycle deterioration) due to the gas generating material coming into contact with other battery constituent materials. Further, when the battery is overcharged in the battery having such a configuration, as shown in FIG. 5B, the temperature in the battery case rises and the gas generating material 64 contained in the microcapsule 62 is vaporized. When the gas generating material 64 is vaporized, heat is taken from the surroundings, so that the high temperature portion of the battery can be cooled. Then, as shown in FIG. 5C, when the outer shell of the microcapsule 62 bursts without being able to withstand the increase in internal pressure, the gas generated from the gas generating material 64 (gas vaporized in this example) enters the battery case. Released, the internal pressure of the battery case rises at once. Thereby, the electric current interruption mechanism 30 (FIG. 1) can be operated appropriately. Therefore, according to the configuration of the present embodiment, it is possible to realize a lithium secondary battery that can effectively generate gas during overcharge and accurately operate the current interrupting mechanism while maintaining good battery performance under normal conditions.

  In addition to the gas generating material 64, the microcapsule 62 can contain a substance (overcharge inhibitor) that acts as a resistor for overcharge current during overcharge as necessary. Any overcharge inhibitor can be used without particular limitation as long as it acts as a resistor for overcharge current during overcharge. For example, a compound having an oxidation potential lower than the decomposition potential of the electrolytic solution can be preferably used. Preferable examples of the compound include aromatic compounds such as alkylbenzene derivatives and cycloalkylbenzene derivatives. Examples of the alkylbenzene derivatives include cumene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene, 1-methylpropylbenzene, 1,3-bis (1-methylpropyl) benzene, 1,4-bis (1-methylpropyl). ) Benzene and the like. Examples of the cycloalkylbenzene derivative include cyclohexylbenzene (CHB) and cyclopentylbenzene. Such compounds may be used singly or in combination of two or more. When the battery is overcharged, the compound is rapidly oxidized and decomposed at the positive electrode (typically, the surface of the positive electrode active material) to form a high-resistance film (polymer) on the active material surface. This film acts as an overcharge current resistor. In addition, the said compound generate | occur | produces gas by said oxidative decomposition reaction. That is, the above compound also functions as a second gas generating material that generates gas by oxidative decomposition. Therefore, in addition to the generation of gas from the gas generating material (the first gas generating material that generates gas by vaporization, for example, a fluorine-based liquid), more gas can be efficiently generated in the battery case. it can.

  The above-mentioned compound (overcharge inhibitor) can be added and mixed directly in the electrolytic solution as well as in the form of being encapsulated in the microcapsule 62. However, when the above compound is directly added to and mixed with the electrolytic solution, the compound functions as a resistance component, which may cause a decrease in battery performance. According to this configuration, by encapsulating a part of the compound in the microcapsule 62, the battery performance is maintained while maintaining the same overcharge inhibitor effect as compared with the case where the entire compound is added to and mixed with the electrolytic solution. The decrease can be suppressed.

  In the above embodiment, the lithium secondary battery 100 having the configuration in which the capsule is arranged in the battery case by using the positive electrode sheet holding the gas generating material-encapsulating microcapsule 62 has been described. However, the microcapsule is arranged in the battery case. The mode to perform is not limited to this. For example, a negative electrode sheet holding microcapsules can be produced in the same manner as the positive electrode sheet described above. Or it is good also as an electrode body of the structure by which the microcapsule was pinched | interposed between the positive electrode sheet and / or the negative electrode sheet, and the separator sheet. In the electrode body having such a configuration, for example, the microcapsules can be disposed between the positive electrode sheet and the separator sheet by spreading the microcapsules on the positive electrode sheet and laminating the separator sheet thereon. Among these modes, the oxidative decomposition reaction by the overcharge inhibitor described above mainly occurs on the surface of the positive electrode active material, and therefore, a mode in which the microcapsules are held on the positive electrode sheet as in the above embodiment can be preferably employed.

  Subsequently, another embodiment according to the present invention will be described below. As described above, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description of the configuration is omitted.

<Second Embodiment>
First, a second embodiment according to the present invention will be described with reference to FIG. This embodiment is different from the first embodiment described above in that the microcapsule 62 is held by the separator 40 as shown in FIG. That is, in the lithium secondary battery according to the present embodiment, the microcapsule 62 that encloses the gas generating material 64 is held by the separator base material as the separator sheet 40 that constitutes the electrode body 80 by overlapping the positive electrode sheet and the negative electrode sheet. Use the same thing. According to this structure, there exists a merit that the burst at the time of coating and drying can be prevented. That is, when the microcapsules are held in the positive electrode active material layer as in the first embodiment, the microcapsules are added to the positive electrode active material layer forming paste, and the positive electrode active material layer forming paste is added to the positive electrode current collector. It needs to be applied to the body and allowed to dry, but at that time, the microcapsules may burst. On the other hand, in the case where the microcapsules are held in the separator, it is only necessary to spread the microcapsules on the separator and put them in the separator holes, and it is possible to prevent rupture during coating and drying as described above. The microcapsule may be held by only one of the two separator sheets constituting the electrode body, or both of them may be held.

  As the separator substrate, as described above, various porous sheets similar to the separator of a lithium secondary battery including a wound electrode body can be used. Preferable examples include porous resin sheets (films, nonwoven fabrics, etc.) made of polyolefin resins such as polyethylene (PP) and polypropylene (PP). Such a porous resin sheet may have a single layer structure, or may have a two or more layers structure (for example, a three-layer structure in which PE layers are laminated on both sides of a PP layer). Although it is not particularly limited, preferred porous sheets (typically porous resin sheets) used as the separator base material have an average pore diameter of about 0.001 μm to 30 μm and a thickness of 5 μm to 100 μm. Examples of the porous resin sheet are (more preferably 10 μm to 30 μm). The air efficiency (porosity) of the porous sheet can be, for example, about 20 to 90% by volume (preferably 30 to 80% by volume).

  The lithium secondary battery according to the present embodiment includes a separator sheet 40 in which microcapsules 62 are held on such a separator base material. For example, as a preferable configuration example of the separator sheet 40, a porous sheet (either a single layer or a multilayer) may be used as a separator base material, and the microcapsule 62 is caught in the pores of the porous sheet, whereby the capsule is separated from the separator sheet 40. A configuration held on a sheet is mentioned. For example, in a state where the porous sheet is elastically stretched (in a state where the pores are widened), microcapsules are supplied to the sheet (for example, the microcapsules are sprayed on the sheet), and then the stretching is released to make the porous By contracting the sheet to the original shape, a configuration in which the microcapsules 62 are held in the pores of the sheet can be easily realized. In this case, it is preferable that the particle size of the microcapsule is approximately the same as or larger than the pore size of the porous sheet constituting the separator sheet. Accordingly, it is possible to appropriately prevent the phenomenon that the microcapsules fall off from the separator sheet without using any means such as adhesion or fusion.

  As another preferred configuration example of the positive electrode sheet 10, a separator base material composed of a porous resin sheet having a three-layer structure in which a first PE layer and a second PE layer are laminated on both sides of a PP layer, and a micro layer between the resin sheets is provided. The separator sheet 40 in which the capsules 62 are sandwiched can be preferably used. According to such a configuration, since the microcapsule 62 is disposed (incorporated) inside the separator, the phenomenon that the capsule 62 falls off the positive electrode sheet or is displaced in the surface direction of the positive electrode sheet due to gravity or acceleration is suppressed. can do.

<Third Embodiment>
A third embodiment according to the present invention will be described with reference to FIGS. 7 (a) and 7 (b). In this embodiment, as shown in FIGS. 7A and 7B, the first and second microcapsules 62 are arranged at the winding center portion 85 of the wound electrode body 80. This is different from the embodiment. That is, in the lithium secondary battery according to this embodiment, the positive electrode sheet 10 and the negative electrode sheet 20 are stacked with the separator sheets 40A and 40B interposed therebetween, and the sheet-like electrode body (laminated body) is wound up. A rotating electrode body 80 is formed. A microcapsule 62 is disposed at the winding center portion 85 of the wound electrode body 80. According to such a configuration, since the microcapsule is disposed near the central portion in the radial direction of the wound electrode body 80 where heat is easily generated when the temperature rises, the high temperature portion of the battery can be cooled more effectively.

  The microcapsule 62 is disposed at the winding center portion 85 of the wound electrode body 80, for example, after the microcapsule 62 is held by a porous sheet-like object (hereinafter referred to as a porous sheet) 66, the porous This is done by placing the sheet 66 at the winding center portion 85 of the wound electrode body 80. As a preferable configuration example, a configuration in which the capsules are held by the microcapsules 62 being caught in the pores of the porous sheet 66 can be cited. For example, the microcapsules 62 are supplied to the porous sheet 66 in a state where the porous sheet 66 is elastically stretched (in a state where the pores are widened) (for example, the microcapsules 62 are sprayed on the porous sheet 66). Next, by releasing the stretching and contracting the porous sheet 66 to the original shape, a configuration in which the microcapsules 62 are held in the pores of the porous sheet 66 can be easily realized. By inserting the porous sheet 66 holding the microcapsule 62 into the winding center portion 85 of the winding electrode body 80, the microcapsule 62 can be disposed at the winding center portion 85 of the winding electrode body 80. it can. In this case, it is preferable that the particle size of the microcapsule is approximately the same as or larger than the pore size of the porous sheet. Accordingly, it is possible to appropriately prevent the phenomenon that the microcapsules fall off from the porous sheet without using any means such as adhesion or fusion.

  Hereinafter, the present invention will be described in more detail based on examples.

Example 1
<Microcapsule>
As a gas generating material (additive) included in the microcapsule, a fluorine-based inert liquid (Zeorolla H (boiling point 83 ° C.) manufactured by Nippon Zeon Co., Ltd.) was used. This fluorinated liquid was put into water, stirred and emulsified with a mixer, and then paraffin wax as an outer shell material was put in a molten state. Thereafter, the mixture was cooled with stirring and subjected to suction filtration and drying steps to obtain gas generating material-encapsulated microcapsules (average particle diameter of 10 μm based on laser diffraction scattering method) in which the fluorinated liquid was coated with an outer shell. This gas generating material-encapsulating microcapsule was placed in a battery case to produce a test lithium secondary battery. The lithium secondary battery for test was produced as follows.

<Positive electrode sheet>
In this example, the lithium secondary battery 100 having a configuration in which the gas generating material-encapsulating microcapsules 62 are held by the positive electrode sheet 10 was produced. Specifically, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ powder as a positive electrode active material, acetylene black (conductive material), and polyvinylidene fluoride (PVdF) are mass ratios of these materials. Was mixed with N-methylpyrrolidone (NMP) so that the solid content concentration was about 50% by mass, and a positive electrode active material layer forming paste was prepared. The gas generating material-encapsulating microcapsules 62 are added to this positive electrode active material layer forming paste, and then applied to a long aluminum foil (positive electrode current collector 12) and naturally dried, whereby both surfaces of the positive electrode current collector 12 are coated. Then, the positive electrode sheet 10 provided with the positive electrode active material layer 14 including the gas generating material-containing microcapsules 62 was prepared. The coating amount of the positive electrode active material layer paste was adjusted so as to be about 10 mg / cm ² (solid content basis) for both surfaces.

<Negative electrode sheet>
A negative electrode active material layer obtained by dispersing graphite powder as a negative electrode active material, styrene butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in water so that the mass ratio of these materials is 98: 1: 1. A forming paste was prepared. The negative electrode active material layer 24 was provided on both surfaces of the negative electrode current collector 22 by applying this negative electrode active material layer forming paste on both surfaces of the long copper foil (negative electrode current collector 22) and drying. A negative electrode sheet 20 was produced.

<Lithium secondary battery>
The positive electrode sheet 10 and the negative electrode sheet 20 are wound through two separator sheets (single-layer structure made of porous polyethylene is used) 40, and the rolled body is crushed from the lateral direction to form a flat shape. A wound electrode body 80 was produced. The wound electrode body 80 obtained in this way was housed in a box-type battery case 50 together with a non-aqueous electrolyte, and the opening of the battery case 50 was hermetically sealed. As the non-aqueous electrolyte, a non-aqueous electrolyte was used in which LiPF ₆ as a supporting salt was contained at a concentration of about 1 mol / liter in a mixed solvent containing EC, EMC, and DMC in a volume ratio of 3: 4: 3. . A current interruption mechanism 30 shown in FIG. 1 is installed between the positive electrode terminal 70 and the wound electrode body 80. In this way, the lithium secondary battery 100 was assembled. Thereafter, an initial charge / discharge treatment (conditioning) was performed by a conventional method to obtain a lithium secondary battery for testing.

(Example 2)
Example 1 except that CHB was used in addition to the fluorinated liquid as the gas generating material (additive) contained in the microcapsule 62, and that the microcapsules were held in the separator sheets 40A and 40B. Similarly, a test lithium secondary battery was produced.

(Example 3)
A test lithium secondary battery was produced in the same manner as in Example 1 except that the gas generating material-encapsulating microcapsules were arranged in the wound central portion 85 of the wound electrode body 80.

(Comparative Example 1)
The same amount of fluorine-based inert liquid as in Example 1 was added to the electrolytic solution without being encapsulated in the microcapsule 62 to produce a lithium secondary battery 100.

(Comparative Example 2)
The lithium secondary battery 100 was manufactured by adding the same amount of fluorine-based liquid and CHB as in Example 2 to the electrolyte without encapsulating the microcapsules 62.

(Comparative Example 3)
A lithium secondary battery 100 was manufactured by adding the same amount of fluorine-based liquid as in Example 3 to the electrolyte without encapsulating the microcapsules 62.

<IV resistance test>
For each of the lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 to 3, each battery was subjected to SOC (State) by constant current and constant voltage (CC-CV) charging in a room temperature (about 25 ° C.) environment atmosphere. of Charge) was adjusted to 60% charge. Thereafter, discharging was performed at 25 ° C. with a current value of 10 C for 10 seconds, and IV resistance was calculated from a voltage drop amount 10 seconds after the start of discharging. The results are shown in Table 1.

<Overcharge test>
Furthermore, the lithium secondary battery which concerns on Examples 1-3 and Comparative Examples 1-3 was prepared separately, and the overcharge test was done with respect to each battery. In the overcharge test, the battery was charged until it reached 10 V at a current value of 3 C in a room temperature (about 25 ° C.) environment atmosphere. And the action | operation of the electric current interruption mechanism 30 was investigated. The results are shown in Table 1.

As is clear from Table 1, in the batteries according to Examples 1 to 3 in which the gas generating material is encapsulated in the microcapsule, in the above overcharge test, the current interruption mechanism is activated before reaching 10 V and the charging current is increased. Since it was interrupted, the overcharge test was terminated here. That is, in these batteries, as the overcharge progressed, the gas released from the gas generating material increased the internal pressure of the battery case, and the current interruption mechanism was activated. In addition, the IV resistance values of the batteries according to Examples 1 to 3 were able to achieve a low value of 1200 mΩ or less.
On the other hand, in the batteries according to Comparative Examples 1 and 3 in which the gas generating material (fluorine-based liquid) was added to the electrolyte, the voltage reached 10 V without operating the current interruption mechanism in the overcharge test. The overcharge test was terminated here. The temperature of the batteries according to Comparative Examples 1 and 3 immediately after the overcharge test was finished was higher than that immediately after the operation of the current interrupt mechanism of the batteries according to Examples 1 to 3. Also,
In the battery according to Comparative Example 2 in which CHB was added to the electrolytic solution in addition to the fluorine-based liquid, gas was also generated from CHB by oxidative decomposition, so that the current interruption mechanism was activated before reaching 10 V in the overcharge test. However, the IV resistance value was greatly reduced as compared with the batteries according to Examples 1 to 3. From the above results, by encapsulating the gas generating material in the microcapsule, while maintaining good battery performance during normal time (that is, while the battery is used in the normal charge / discharge range), the gas can be discharged during overcharge. It was confirmed that a lithium secondary battery that can be generated effectively can be realized.

As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.
For example, in the above-described embodiment, a lithium secondary battery has been described as a typical example of the secondary battery, but the present invention is not limited to the secondary battery of this form. For example, a secondary battery using a metal ion other than lithium ion (for example, sodium ion) as a charge carrier, or an electric double layer capacitor (physical battery) such as a lithium ion capacitor may be used.
Since the battery 100 according to the present invention exhibits good battery performance as described above, it can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, the present invention, as schematically shown in FIG. 8, is a vehicle (typically an automobile, particularly a hybrid automobile) provided with such a lithium secondary battery 100 (typically, a battery pack formed by connecting a plurality of series batteries) as a power source. , An automobile equipped with an electric motor such as an electric vehicle and a fuel cell vehicle.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Positive electrode sheet 12 Positive electrode collector 14 Positive electrode active material layer 16 Positive electrode active material layer non-formation part 18 Positive electrode active material particle 20 Negative electrode sheet 22 Negative electrode current collector 24 Negative electrode active material layer 26 Negative electrode active material layer non-formation part 30 Current interrupt mechanism 32 Deformed metal plate (conducting member; first member)
34 Connection metal plate (conducting member; second member)
40A, 40B Separator sheet 50 Battery case 52 Case body 54 Lid 62 Microcapsule 64 Gas generating material 70 Positive electrode terminal 72 Negative electrode terminal 74 Positive electrode lead terminal 76 Negative electrode lead terminal 80 Winding electrode body 82 Winding core portion 85 Winding center portion 100 batteries

Claims (9)

An electrode body comprising a positive electrode and a negative electrode;
A secondary battery comprising a battery case that houses the electrode body,
Microcapsules arranged inside the battery case;
A gas generating material that is encapsulated in the microcapsule and generates gas when the temperature in the battery case rises;
A secondary battery comprising: a current interruption mechanism that operates when an internal pressure of the battery case rises due to gas generation from the gas generating material.   The secondary battery according to claim 1, wherein the gas generating material is a fluorine-based liquid.   The secondary battery according to claim 1, wherein the gas generating material is a liquid having a boiling point of 70 ° C. or higher.   The secondary battery according to claim 1, wherein the microcapsule contains an overcharge inhibitor.   The secondary battery according to claim 4, wherein the overcharge inhibitor is an alkylbenzene derivative and / or a cycloalkylbenzene derivative. The positive electrode includes a positive electrode current collector and a positive electrode active material layer,
The secondary battery according to claim 1, wherein at least a part of the microcapsules is held in the positive electrode active material layer. The electrode body includes a separator that separates the positive electrode and the negative electrode,
The secondary battery according to claim 1, wherein at least a part of the microcapsule is held by the separator. The electrode body is a wound electrode body in which the sheet-like positive electrode and the sheet-like negative electrode are laminated and wound,
The secondary battery according to claim 1, wherein at least a part of the microcapsule is disposed at a winding center portion of the wound electrode body. A positive electrode terminal and a negative electrode terminal are electrically connected to the positive electrode and the negative electrode of the electrode body, respectively.
The current interrupt mechanism includes a conductive member that forms a conductive path from at least one of the positive electrode and the negative electrode terminal to the electrode body, and when the internal pressure of the battery case increases due to gas generation from the gas generating material The secondary battery according to claim 1, wherein the conductive member is deformed to cut the conductive path.

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