JP6531919B2 - Lithium ion battery - Google Patents

Description

  The present invention relates to the structure of a lithium ion battery, and more particularly to a structure for preventing ignition of a lithium ion battery.

  Conventionally, lithium ion batteries having high energy density have been used for consumer mobile devices and the like. Lithium ion batteries have excellent charge and discharge characteristics and can form a large capacity light weight, so in recent years, they are mounted on vehicles and are also used as power sources of electric motors for running the vehicles.

  In lithium ion batteries, when the temperature rises abnormally due to an overcharge, or when a part of the electrodes shorts due to an impact etc., there is a risk that the electrolyte containing the organic compound may be vaporized. . When the vaporized electrolyte is oxidized, the temperature further rises, and there is a risk that the lithium ion battery may ignite. In particular, it is necessary to mount an ignition prevention function on an on-vehicle lithium ion battery which may be subjected to an impact due to a collision of a vehicle or the like.

  Therefore, for example, as disclosed in Patent Document 1, there is known a technique for reducing the temperature of the vaporized electrolytic solution to prevent ignition when eliminating the increase in internal pressure of the battery case due to the vaporization of the electrolytic solution by opening the safety valve. Further, as in Patent Documents 2 and 3, there is a technology in which a flame retardant is blended in a negative electrode active material mixture layer constituting an electrolytic solution of a lithium ion battery or a negative electrode to prevent oxidation of the vaporized electrolytic solution to prevent ignition. Are known.

JP, 2013-187089, A JP, 2014-160608, A JP, 2016-62855, A

  However, the technique of Patent Document 1 requires time to open the safety valve. Moreover, it does not stop the vaporization of the electrolyte solution due to abnormal heat generation. Therefore, even if the technology of Patent Document 1 is applied to a lithium ion battery for vehicle use, there is a possibility that a large amount of vaporized electrolytic solution may be ejected, which is not sufficient for securing safety. In addition, when a flame retardant is blended in the electrolyte solution or the negative electrode active material mixture layer as in Patent Documents 2 and 3, a side reaction usually occurs during use to inhibit the movement of lithium ions, so the charge / discharge performance of the lithium ion battery There is a problem that the capacity of the lithium ion battery decreases rapidly due to the problem of the decrease and repetition of charge and discharge. It is necessary to suppress such performance deterioration because the lithium ion battery for vehicle use has a large input / output compared with a consumer mobile device etc., and has a long service life and many repetitions of charge and discharge.

  An object of the present invention is to provide a lithium ion battery capable of suppressing the performance deterioration and preventing the ignition.

  A first invention comprises a wound body in which a positive electrode and a negative electrode are wound via a separator, and an insulating film covering the outer periphery of the wound body along a winding direction, and the wound body and the insulating film In the lithium ion battery in which the battery is immersed in the electrolytic solution and housed in a rectangular case, the insulating film is formed of a synthetic resin material that melts at a predetermined temperature or higher, and the electrolytic solution solidifying agent and the flame retardant are sealed. It is characterized by having a pair of accommodation parts accommodated in.

  According to the above configuration, the electrolytic solution solidifying agent and the flame retardant are accommodated in the accommodation portion during normal use and no side reaction occurs, so that the performance deterioration of the lithium ion battery can be suppressed. In addition, when abnormal heat is generated due to overcharge or impact, the synthetic resin material constituting the containing portion melts when reaching a predetermined temperature, and the electrolytic solution solidifying material and the flame retardant in the containing portion are released to the electrolytic solution. Therefore, the progress of the vaporization of the electrolytic solution and the ignition of the vaporized electrolytic solution can be prevented.

  In a second invention according to the first invention, the insulating film is wound so as to maintain the winding shape of the wound body and tension is applied along the winding direction, When the pressing force is applied to the containing portion from the case, a plurality of fracture promoting particles having projections for promoting the breakage of the wound body side film member of the containing portion are contained in the containing portion. And

  According to the above configuration, when the case is deformed by impact and a pressing force is applied to the housing portion, the wound body side film member constituting the housing portion is broken due to the collision with the fracture promoting particles, and the electrolyte solidifying material and the flame retardant in the housing portion Is released into the electrolyte. Therefore, the progress of the vaporization of the electrolytic solution and the ignition of the vaporized electrolytic solution can be prevented. In addition, since tension is applied to the insulating film, tension acts so as to push out the electrolytic solution solidifying material and the flame retardant when the wound body side film member is broken, thereby releasing the electrolytic solution solidifying material and the flame retardant. It is advantageous.

  In a third invention according to the first or second invention, the wound body includes a pair of flat portions substantially parallel to the largest surface of the case, and the pair of accommodating portions includes the pair It is characterized in that it is disposed in intimate contact with the flat portion of

  According to the above configuration, the storage portion is disposed near the abnormal heat generation portion of the wound body regardless of the position of the abnormal heat generation portion. Therefore, the storage portion can be dissolved immediately after the generation of the abnormal heat generation. Further, since the largest surface of the case is most likely to be deformed when it receives an impact, a pressing force acts from this surface toward the flat portion, which is advantageous for the destruction of the housing portion by the pressing force.

  A fourth invention is characterized in that in the second invention, the fracture promoting particles are made of fine needle-like metal oxide or nonmetal oxide.

  According to the above configuration, when the pressing force is applied, the housing portion can be broken starting from the collision of the destruction promoting particles to the wound body side film portion.

  According to a fifth invention, in the second invention, the fracture promoting particles are made of fine particulate metal oxide or nonmetal oxide.

  According to the above configuration, when the pressing force is applied, the housing portion can be broken starting from the collision of the destruction promoting particles to the wound body side film portion.

  According to the present invention, it is possible to provide a lithium ion battery capable of suppressing the performance deterioration and preventing the ignition.

It is a principal part disassembled figure of the lithium ion battery which concerns on the Example of this invention. It is a principal part disassembled view of the winding body and insulating film of FIG. It is the III-III line cross-section schematic diagram of the winding body of FIG. 1, and an insulating film part. It is an enlarged view which shows one example of the destruction promotion part of FIG. It is a figure which shows the state to which pushing pressure force was added to the destruction promotion part of FIG.

  Hereinafter, the form for carrying out the present invention is explained based on an example.

First, the entire configuration of the lithium ion battery 1 of the present invention will be described.
As shown in FIG. 1, the lithium ion battery 1 has a positive and negative electrode inside a rectangular parallelepiped case formed of a box-like case main body 2 with an open top and a lid member 3 for closing the opening. The wound body 10 is housed and formed. The wound body 10 has an insulating film 15 covering the outer periphery thereof along the winding direction. An electrolytic solution (not shown) for immersing the wound body 10 covered with the insulating film 15 is filled in the case.

  The case body 2 and the lid member 3 are formed of, for example, an aluminum material, and an insulating film (not shown) is formed on the inner wall surface of the case body 2 and the cover member 3. The positive electrode terminal 4 and the negative electrode terminal 5 for connecting to the external apparatus respectively connected to the positive / negative electrode of the accommodated winding body 10 at the cover member 3 are arrange | positioned in the shape of protrusion upwards. The lid member 3 and the case body 2 are joined, for example, by welding or the like, and sealed so that the electrolyte does not leak. The size of the case is, for example, 16 cm in length, 3 cm in width, and 12 cm in height, but is not limited to this, and is appropriately set according to the specification of the lithium ion battery 1 and the like.

Next, the wound body 10 will be described.
As shown in FIG. 2, the wound body 10 is wound via a strip-like separator having substantially the same width as the positive electrode 11 and the negative electrode 12 so that the strip-like positive electrode 11 and the negative electrode 12 having substantially the same width do not contact each other. It is done. The separator is composed of a first separator 13 and a second separator 14.

  The wound body 10 has, for example, a strip-shaped first separator 13 having a width of 14 cm and a length of 18 m, a positive electrode 11, a second separator 14 and a negative electrode 12 stacked in this order, with the width direction being the winding axis direction. The winding body 10 is formed by winding 90 times flatly so that the negative electrode 12 is the outermost layer. The sizes of the positive electrode 11 and the negative electrode 12, the sizes of the first and second separators 13 and 14, the number of turns, and the like are not limited to the above, and are appropriately set according to the specifications of the lithium ion battery 1.

  The flat wound body 10 has a pair of flat portions 10a and 10b, and the pair of flat portions 10a and 10b is substantially parallel to the largest pair of faces of the case body 2, for example, The winding axis direction is made parallel to the longitudinal direction of the case body 2 and accommodated in the case.

Next, the positive electrode 11 will be described.
As shown in FIG. 2, the strip-shaped positive electrode 11 has porous positive electrode active material mixture layers 11b and 11c on both sides of the current collector 11a made of metal foil, excluding the outer peripheral portion thereof, to which the electrolytic solution can infiltrate. Have. The current collector 11a is made of, for example, an aluminum foil having a thickness of 10 to 20 μm, and includes the positive electrode tab portion 11d. Although not shown, the positive electrode tab portion 11 d is connected to the positive electrode terminal 4 of the lid member 3. A plurality of positive electrode tab portions 11d may be provided at intervals on one side in the longitudinal direction of the current collector 11a.

  In the positive electrode active material mixture layers 11b and 11c, a mixture slurry in which a positive electrode active material and a conductive additive are uniformly dispersed in a solvent in which a binder is dissolved is applied in a thin film to the current collector 11a and then dried. For example, it is formed to a thickness of 40 to 100 μm. A planarization process may be performed by a roller or the like. The formed positive electrode active material mixture layers 11 b and 11 c have a positive electrode active material, a conductive additive, and a binder. The positive electrode active material, the conductive additive, and the current collector 11a are connected to each other by the binder in a state of being in contact with each other, and the positive electrode active material mixture layer 11b and the current collector 11a are electrically connected.

  The positive electrode active material is, for example, a particulate lithium oxide such as lithium manganate or lithium nickelate having a particle size of 20 to 40 μm. The conductive aid is, for example, a particulate carbon material having a size of 1 to 10 μm in which a plurality of fine particles such as graphite and acetylene black are connected. The binder is, for example, elongated particulate polyvinylidene fluoride having a length of 30 to 50 μm, and connects the positive electrode active material, the conductive support agent, and the current collector 11a.

  The positive electrode active material mixture layers 11 b and 11 c contain, for example, 90 wt% of the positive electrode active material, 5 wt% of the conductive additive, and 5 wt% of the binder. The materials contained in the positive electrode active material mixture layers 11b and 11c, the particle sizes thereof, the content ratios thereof, and the like are only an example, and the present invention is not limited thereto. It will be changed as appropriate.

Next, the negative electrode 12 will be described.
As shown in FIG. 2, the strip-like negative electrode 12 has porous negative electrode active material mixture layers 12b and 12c on which both sides of the outer periphery of the current collector 12a made of metal foil can be infiltrated except for the outer peripheral portion. It is provided over substantially the entire length of the current collector 12a. The current collector 12a is made of, for example, a copper foil having a thickness of 10 to 20 μm, and includes a negative electrode tab portion 12d disposed so as to protrude in the opposite direction to the positive electrode tab portion 11d. Although not shown, the negative electrode tab portion 12 d is connected to the negative electrode terminal 5 of the lid member 3. A plurality of negative electrode tab portions 12d may be provided at intervals along one side in the longitudinal direction of the current collector 12a. The formation of the negative electrode active material mixture layer 12c may be omitted in a portion corresponding to the outer peripheral surface of the wound body 10 of the current collector 12a.

  In the negative electrode active material mixture layers 12b and 12c, a mixture slurry in which a negative electrode active material and a conductive additive are uniformly dispersed in a solvent in which a binder is dissolved is applied in a thin film to the current collector 12a and then dried. For example, it is formed to a thickness of 40 to 100 μm. The formed negative electrode active material mixture layers 12 b and 12 c have a negative electrode active material, a conductive additive, and a binder. A planarization process may be performed by a roller or the like. The negative electrode active material, the conductive additive, and the current collector 12a are connected to each other by a binder in contact with each other, and the negative electrode active material mixture layer 12b and the current collector 12a are electrically connected.

  The negative electrode active material is, for example, a carbon material such as particulate graphite having a particle diameter of 20 to 40 μm. The conductive support agent and the binder are equivalent to the conductive support agent and the binder of the positive electrode active material mixture layers 11b and 11c, and thus the description thereof is omitted. The negative electrode active material mixture layers 12b and 12c contain, for example, 90 wt% of the negative electrode active material, 5 wt% of the conductive additive, and 5 wt% of the binder. The materials contained in the negative electrode active material mixture layers 12b and 12c, the particle sizes thereof, the content ratio thereof, and the like are only an example, and the present invention is not limited to the above. It is set appropriately.

Next, the separator will be described.
The first and second separators 13 and 14 are insulators for preventing contact between the positive electrode 11 and the negative electrode 12. The first and second separators 13 and 14 are formed in a porous shape having a large number of pores with a diameter of about 0.1 to 1 μm to allow the electrolyte to infiltrate and lithium ions are allowed to pass through the pores. Can pass through the first and second separators 13 and 14. The first and second separators 13 and 14 are formed, for example, in the shape of a strip having a thickness of 20 to 30 μm by a synthetic resin material such as polyethylene or polypropylene.

Next, the insulating film 15 will be described.
As shown in FIGS. 1 to 3, the wound body 10 is provided with an insulating film 15 which covers the outer periphery of the wound body along the winding direction. The insulating film 15 is wound so as to maintain the winding shape of the wound body 10, and in a state in which tension is applied along the winding direction, both ends in the winding direction are overlapped and fixed. In addition, FIG. 3 has expanded and shown the thickness of insulating film 15 grade | etc.,.

  The insulating film 15 has a pair of wound film side film members 16 and 17 attached to the side of the wound body 10, and is formed in a sealed state between the insulating film 15 and the wound film side film members 16 and 17. The housings 18 and 19 are provided. The insulating film 15 covers the outer periphery of the wound body 10 by bringing the wound body side film members 16 and 17 into close contact with the pair of flat portions 10 a and 10 b of the wound body 10 respectively.

  The same solvent as an electrolytic solution described later including the electrolytic solution solidifying agent for solidifying the electrolytic solution and the flame retardant for suppressing ignition of the vaporized electrolytic solution is housed in the housing portions 18 and 19. The electrolytic solution solidifying agent is, for example, a tetraethoxysilane aqueous solution, and reacts with the electrolytic solution to solidify to suppress evaporation of the electrolytic solution. The flame retardant is, for example, a phosphazene compound, which scavenges ambient oxygen to suppress oxidation.

  The wound body side film members 16 and 17 are formed of a synthetic resin material that melts at a predetermined temperature or more. For example, the wound film side film members 16 and 17 are formed of a polyethylene film material melting at 100 to 110 ° C., a polypropylene film material melting at 130 to 140 ° C., or the like. The insulating film 15 may be formed of the same synthetic resin material as the wound body side film members 16 and 17 or may be formed of a synthetic resin material having a higher melting temperature than the wound body side film members 16 and 17. When the temperature at which the insulating film 15 melts is higher than that of the wound film side film members 16 and 17, when the wound film side film members 16 and 17 melt, the tension applied to the insulating film 15 is stored in the housing portion 18, It can be made to act so that the solvent containing an electrolyte solution solidifying agent and a flame retardant may be extruded from 19.

  As shown in FIG. 4, in the insulating film 15 constituting the housing portions 18 and 19, a plurality of destruction promoting portions 20 and the like projecting toward the wound body side film members 16 and 17 are disposed. As shown in FIG. 5, when a pressing force is applied from the case main body 2 side, the destruction promoting portion 20 and the like are caused to collide with the wound body side film members 16 and 17, and from this as a starting point, the wound body side film The members 16 and 17 break.

  The fracture promoting portion 20 is, for example, a fine needle-like or particulate metal oxide (for example, alumina) or a nonmetal oxide (for example, glass fiber, silica) having a size of about 20 to 100 μm in the housing portions 18 and 19. It is formed to be fixed to the insulating film 15. Since these oxides are insulators, the positive electrode 11 and the negative electrode 12 are not short-circuited even if they are separated from the insulating film 15 and enter the wound body 10 together with the electrolytic solution solidifying material, the flame retardant and the like. Moreover, although illustration is abbreviate | omitted, the destruction promotion part 20 sticks the sheet-like projection member made of hard synthetic resin, for example in which several protrusion which has a sharp front-end | tip part was formed in the accommodating parts 18 and 19 of the insulating film 15. You may attach and form.

Next, the electrolytic solution will be described.
The electrolytic solution is, for example, an electrolytic solution in which a lithium salt such as lithium hexafluorophosphate or lithium borofluoride is dissolved in a solvent obtained by mixing a high viscosity cyclic ester and a low viscosity chain ester, but is not limited thereto. A known electrolytic solution can be used. The electrolytic solution is filled in the case, and infiltrates into the first and second separators 13 and 14, the positive electrode active material mixture layers 11b and 11c, and the negative electrode active material mixture layers 12b and 12c.

Next, the operation and effects of the lithium ion battery 1 of the present embodiment will be described.
Since the electrolytic solution solidifying agent and the flame retardant are contained in the housing portions 18 and 19 of the insulating film 15, the electrolytic solution and the positive electrode active material mixture layers 11b and 11c and the negative electrode active material mixture layers 12b and 12c are normally electrolyzed It can be set as a structure which does not contain a liquid solidification agent and a flame retardant. Therefore, side reactions and the like between the electrolytic solution solidifying agent and the flame retardant do not occur, and the movement of lithium ions is not inhibited, so that the performance deterioration of the lithium ion battery 1 can be suppressed.

  In addition, when the winding body 10 is heated to a predetermined temperature or more due to the occurrence of abnormal heat generation due to a short circuit due to overcharge or impact, the winding body side film members 16 and 17 constituting the housing portions 18 and 19 melt or pressure force of impact As a result, the wound body side film members 16 and 17 are broken, and the solvent containing the electrolytic solution solidifying agent and the flame retardant is released to the electrolytic solution. Therefore, vaporization of the electrolyte can be suppressed immediately after abnormal heat generation or after receiving an impact, and even if the electrolyte is vaporized, oxidation thereof can be suppressed, so that ignition of the lithium ion battery 1 can be prevented. . At this time, the tension in the winding direction applied to the insulating film 15 acts to push out the solvent containing the electrolytic solution solidifying material and the flame retardant, which is advantageous for the release of the electrolytic solution solidifying material and the flame retardant.

  The housing portions 18 and 19 are disposed in close contact with the pair of flat portions 10 a and 10 b of the wound body 10, respectively. Therefore, even if abnormal heating occurs at any position of the wound body 10, the housings 18 and 19 are at a close position, so that the housings 18 and 19 can be dissolved immediately after the abnormal heating. In addition, since the largest surface of the case is most likely to be deformed when it receives an impact, a pressing force acts on the housing portion 18 or the housing portion 19 from this surface. Therefore, it is advantageous to the destruction by the pressing force of the accommodating parts 18 and 19 closely disposed on the flat parts 10a and 10b of the wound body 10 parallel to this surface. In addition, since the fracture promoting portion 20 and the like projecting toward the wound body side film members 16 and 17 are disposed in the housing portions 18 and 19 of the insulating film 15, when a partial pressure is applied, Starting from the collision of the breakage promotion part 20 with the wound body side film member 16, 17, the housing parts 18, 19 can be easily broken.

Next, an example in which the embodiment is partially changed will be described.
[1] A pair of housings formed on an insulating film 15 having a laminate in which thin film positive electrodes and negative electrodes are alternately laminated via a separator instead of the wound body 10 and the laminate is wound. The portions 18 and 19 may be disposed in close contact with each other on the pair of outermost layer surface portions of the laminate. Even in the lithium ion battery having such a configuration, it is possible to exhibit the functions of performance reduction suppression and ignition prevention in the same manner as the above embodiment.
[2] The wound body 10 may be stacked in the order of the positive electrode 11, the first separator 13, the negative electrode 12, and the second separator 14, and may be wound such that the second separator is the outermost layer.
[3] In addition, those skilled in the art can implement the embodiment in various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. It is.

DESCRIPTION OF SYMBOLS 1 lithium ion battery 2 case main body 3 lid member 10 winding body 10a, 10b flat part 11 positive electrode 11a current collector 11b, 11c positive electrode active material mixture layer 12 negative electrode 12a current collector 12b, 12c negative electrode active material mixture layer 13 First separator 14 Second separator 15 Insulating film 16, 17 Winding body side film member 18, 19 Housing part 20 Fracture promoting part

Claims (5)

A wound body in which a positive electrode and a negative electrode are wound via a separator, and an insulating film covering the outer periphery of the wound body along the winding direction, and the wound body and the insulating film are immersed in the electrolytic solution Lithium ion battery housed in a rectangular parallelepiped case,
The insulating film is formed of a synthetic resin material that melts at a predetermined temperature or higher, and further includes a pair of accommodating portions that accommodate the electrolytic solution solidifying agent and the flame retardant in a sealed manner. The insulating film is wound so as to maintain the winding shape of the wound body, and tension is applied along the winding direction,
When the pressing force is applied to the housing portion from the case, a destruction promoting portion having a plurality of projections for promoting destruction of the wound body side membrane member of the housing portion is housed in the housing portion. The lithium ion battery according to claim 1. The wound body includes a pair of flat portions substantially parallel to the largest surface of the case;
The lithium ion battery according to claim 1, wherein the pair of accommodating portions are disposed in close contact with the pair of flat portions.   The lithium ion battery according to claim 2, wherein the destruction promoting portion is made of a fine needle-like metal oxide or a nonmetal oxide.   The lithium ion battery according to claim 2, wherein the destruction promoting portion is made of a fine particulate metal oxide or a nonmetal oxide.