JP5113434B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery having a tabless current collecting structure, and specifically to a non-aqueous electrolyte secondary battery capable of stably configuring a tabless current collecting structure.

  A non-aqueous electrolyte secondary battery (specifically, a lithium ion secondary battery) includes an electrode group that is a power generation element, a non-aqueous electrolyte, and a current collecting component, such as a mobile phone or a notebook computer. Used as a power source. In the electrode group, a positive electrode and a negative electrode are wound or laminated via a separator, and the nonaqueous electrolyte is held in the separator of the electrode group and the pores of the electrode plate (for example, the pores in the mixture layer).

  A current collecting structure in such a non-aqueous electrolyte secondary battery will be described with reference to FIG.

  As shown in FIG. 9, the positive electrode and the negative electrode have a portion where the mixture layer 1 is provided on the surface of the current collector, and a portion where the current collector is exposed without the mixture layer (exposed portion). 2. The exposed portion 2 is present at the end or central portion of the positive electrode and the negative electrode in the longitudinal direction. The exposed portion 2 is a current collecting lead 3 (in many cases, an aluminum lead is used for the positive electrode). The lead made of nickel is used for the negative electrode). When an electrode group is formed using such an electrode, current is collected along the longitudinal direction of the electrode (lateral direction in FIG. 9).

  When producing a nonaqueous electrolyte secondary battery using the electrode shown in FIG. 9, the positive electrode and the negative electrode are wound through a separator, for example, with the current collector lead of the positive electrode facing up and the current collector lead of the negative electrode facing down. The electrode group is housed in the case, the negative current collecting lead is joined to the case, and the positive current collecting lead is joined to the sealing plate.

  Here, in a lithium ion secondary battery, since the negative electrode is generally wider than the positive electrode, there is a risk that a short circuit may occur at the end face of the electrode group due to displacement of the electrode plate due to vibration or impact. Therefore, in Patent Document 1, in a lithium ion secondary battery having an electrode group in which a positive electrode and a negative electrode are laminated or wound, a porous layer made of insulating particles and a binder is formed on the surface of the negative electrode, The end face of the group is protected by an insulator. Thereby, the shift | offset | difference of the electrode plate accompanying a vibration or an impact can be suppressed, and a short circuit can be prevented.

  By the way, when the electrode shown in FIG. 9 is used, current collection is performed in the longitudinal direction of the electrode plate starting from the current collection lead, so that the current collection resistance increases and it may be difficult to obtain a large output. A so-called “tabless structure” has been proposed as a method of reducing the current collecting resistance. In the tabless structure, in the positive electrode and the negative electrode, an exposed portion is formed at one end in the width direction of the current collector, and a mixture layer is formed in a portion of the current collector other than the exposed portion. The positive electrode and the negative electrode are arranged so that the exposed portion of the positive electrode and the exposed portion of the negative electrode protrude in opposite directions, and an electrode group is formed by winding the positive electrode and the negative electrode through a separator. The current collector plate is welded. In such a tabless structure, there are more junction points between the electrode group and the current collector plate than in the case of using the electrode shown in FIG. 9, and unlike the case of using the electrode shown in FIG. Current is collected along the width direction. Therefore, in the tabless structure, the current collecting resistance can be greatly reduced as compared with the case where the electrode shown in FIG. 9 is used.

  However, in the tabless structure, when the current collector plate is joined to the electrode group, if the current collector plate is welded without pressing against the end face of the electrode group, the welding strength between the current collector plate and the electrode group is sufficiently increased. Cannot be performed, and there is a risk of poor welding. Therefore, in Patent Document 2, a protruding portion is formed on the current collector plate, the exposed portion is bent by pressing the protruding portion against the end face of the electrode group, and a flat portion is formed on a part of the exposed portion. The protruding portion is welded while being in contact with the flat portion of the exposed portion. Thereby, it can weld in the state which contacted the current collecting plate and the electrode group.

Further, Patent Document 3 describes a method of forming a flat portion on the exposed portion of the electrode group. Specifically, while rotating the electrode group around the winding axis, a predetermined surface is formed on the end surface of the exposed portion. A method of pressing a jig is described.
JP 2005-190912 A JP 2000-294222 A JP 2003-162995 A

  However, in Patent Document 1, as shown in FIG. 1 of the same document, since the end faces of the positive electrode and the negative electrode are covered with an insulator on the end face of the electrode group, it is considered that the current is collected through the current collecting lead. It is done. When current is collected through the current collecting lead as described above, current is collected along the longitudinal direction of the electrode, resulting in an increase in current collection resistance, thereby increasing the output of the nonaqueous electrolyte secondary battery. Is difficult. For this reason, it is considered difficult to use the nonaqueous electrolyte secondary battery disclosed in Patent Document 1 as a power source for electric devices (for example, electric tools or hybrid vehicles) that require high output.

  Further, in Patent Document 1, the insulator is formed by using the dipping method. However, since the electrode group of the document is not provided with means for blocking outflow of the solution of the insulator, If the electrode group is moved before the solution is solidified, the insulator solution may flow out from the end face of the electrode group. Therefore, since the next process cannot be performed until the insulator solution is solidified, the manufacturing time of the nonaqueous electrolyte secondary battery becomes long.

  Furthermore, a thin foil having a thickness of about several tens of μm is used for the current collector of the lithium ion secondary battery. Therefore, in the technique described in Patent Document 2, when the current collector plate is pressed against the exposed portion, the vicinity of the root of the exposed portion may be buckled. If the exposed portion buckles, the separator may be damaged, and as a result, an internal short circuit is likely to occur. In addition, when the exposed part buckles, the welded part with the current collector plate approaches the mixture layer, so that spatter generated during welding easily enters the electrode group, and as a result, internal short circuit is likely to occur. End up. Even when the flat portion is formed using the technique described in Patent Document 3, an internal short circuit is likely to occur.

  The present invention has been made in view of the above points, and the object of the present invention is to be able to increase the output, to suppress the occurrence of an internal short circuit during production, Provides a non-aqueous electrolyte secondary battery capable of preventing the battery production time from being prolonged.

The non-aqueous electrolyte secondary battery of the present invention includes an electrode group in which a positive electrode and a negative electrode are wound or laminated via a separator, a non-aqueous electrolyte held in the separator, and a current collector plate joined to the electrode group. It has. At one end in the width direction of one of the positive electrode and the negative electrode, there is an exposed portion where the current collector is exposed from the mixture layer. In the electrode group, the exposed part protrudes in the width direction of the electrode from the end face of the separator and the end face of the other electrode, and a current collector plate is joined to the end face of the exposed part. A reinforcing member for reinforcing the strength of the exposed portion is provided between the adjacent exposed portions. The reinforcing member contacts and covers the end surface of the mixture layer of the one electrode, the end surface of the separator, and the end surface of the other electrode, respectively.

  In the above configuration, since current is collected along the width direction of the electrode, current collection resistance can be reduced.

  Moreover, in the said structure, since the intensity | strength of an exposed part can be reinforced, it can suppress that an exposed part bends during manufacture.

  Further, in the above configuration, even when the reinforcing member is provided by drying or cooling the reinforcing member after applying the reinforcing member solution to a predetermined location, the reinforcing member solution is placed between adjacent exposed portions. Can be retained.

  Here, “adjacent” means that when the positive electrode and the negative electrode are wound, a part of the n-th turn and a part of the (n + 1) -th turn of the exposed part are mutually wound. When the positive electrode and the negative electrode are laminated, it means that the exposed portion of the nth positive electrode and the exposed portion of the (n + 1) th positive electrode are adjacent to each other. Yes.

It is provided with a reinforcing member such that the thickness of the portion covering the end surface of the other electrode becomes thinner than the thickness of the portion covering the end surface of the mixture layer of one electrode of the reinforcing member of the reinforcement member A reinforcing member may be provided so as to be flush with each other .

  As described above, the place where the reinforcing member is provided is not particularly limited. In addition, if the range in which the reinforcing member is provided on the end face of the electrode group is wide, or if the reinforcing member is thick, it is possible to suppress the intrusion of unnecessary materials into the electrode group during manufacturing, and as a result, the separator Since breakage can be suppressed, the probability of occurrence of an internal short circuit can be suppressed. On the other hand, if the range where the reinforcing member is provided on the end face of the electrode group is narrow, or if the reinforcing member is thin, a nonaqueous electrolyte containing a solute and a nonaqueous solvent is used as the nonaqueous electrolyte. It is possible to improve the immersion property of the nonaqueous electrolytic solution into the electrode group.

  In the present invention, high output can be achieved, the cause of internal short-circuit can be prevented from occurring during manufacture, and further, the battery manufacturing time can be prevented from being prolonged.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, as a non-aqueous electrolyte secondary battery, a lithium ion secondary battery in which a non-aqueous electrolyte solution containing a solute (for example, a lithium salt) and a non-aqueous solvent is held at least in a separator is taken as an example. explain. Moreover, in the following embodiment, the substantially same member is attached | subjected with the same code | symbol and the description may be abbreviate | omitted.

Embodiment 1 of the Invention
1 (a) and 1 (b) show the configuration of the electrode group in Embodiment 1, FIG. 1 (a) is a perspective view thereof, and FIG. 1 (b) is a region IB shown in FIG. 1 (a). It is a longitudinal cross-sectional view. FIG. 2 is a plan view showing the configuration of the positive electrode and the negative electrode. 3 (a) and 3 (b) show the configuration of the current collector plate, FIG. 3 (a) is a plan view thereof, and FIG. 3 (b) is a sectional view thereof. 4 (a) and 4 (b) show another current collector plate, FIG. 4 (a) is a plan view thereof, and FIG. 4 (b) is a sectional view thereof. FIG. 5 is a longitudinal sectional view showing a configuration of a part of the current collecting structure according to the present embodiment.

  The lithium ion secondary battery according to this embodiment is a secondary battery having a tabless current collecting structure including an electrode group 14, a non-aqueous electrolyte (not shown), and a current collecting plate 19. In the electrode group of the secondary battery having a tabless current collecting structure, the exposed portion 7 is provided at one end in the width direction (vertical direction in FIG. 2) of the positive electrode 8 and the exposed portion 11 is provided at one end in the width direction of the negative electrode 12. Therefore, current is collected along the width direction of the electrode. Therefore, in the lithium ion secondary battery according to the present embodiment, the current collection resistance can be reduced as compared with the case shown in FIG. 9, and the output of the lithium ion secondary battery can be increased.

  In the positive electrode 8, an exposed portion 7 is formed by exposing the current collector 5 without providing the mixture layer 6, and the mixture 71 is formed in the portion 71 of the current collector 5 other than the exposed portion 7. Layer 6 is provided. Similarly, in the negative electrode 12, an exposed portion 11 is formed by exposing the current collector 9 without providing the mixture layer 10, and a portion 111 of the current collector 9 other than the exposed portion 11 is combined. An agent layer 10 is provided.

  In the electrode group 14 in this embodiment, the positive electrode 8 and the negative electrode 12 are wound through the separator 13, and the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 protrude from the end face of the separator in opposite directions. ing. A positive collector plate 19 is joined to the end face of the exposed portion 7 of the positive electrode 8, and a negative collector plate 19 is joined to the end face of the exposed portion 11 of the negative electrode 12. Further, the electrode group 14 (particularly the separator 13) holds a non-aqueous electrolyte.

  Briefly describing the current collector plate 19, the current collector plate 19 includes a circular portion 17 and a tab portion 18 as shown in FIGS. 3A and 3B, and the tab portion 18 is a circular portion 17. The end surface of the exposed portion is joined to the circular portion 17. 4 (a) and 4 (b) may be used, and the current collecting plate 29 includes a circular portion 27 and a tab portion 28 as in the current collecting plate 19, but the circular portion The protrusions 27a are radially provided on the protrusions 27, and the end surfaces of the exposed parts are joined to the protrusions 27a.

  When the current collector plates 19 and 29 are joined to the exposed portion 7 of the positive electrode 8, it is preferable to use an aluminum current collector plate, and when the current collector plates 19 and 29 are joined to the exposed portion 11 of the negative electrode 12. It is preferable to use a nickel or copper current collector.

  Hereinafter, the electrode group 14 will be described in detail.

  At one end 14 a (the upper end in FIG. 1B) of the electrode group 14, the exposed portion 7 of the positive electrode 8 protrudes from the end surface 12 a of the negative electrode 12 in the width direction of the electrode. Since the positive electrode 8 is wound around in the electrode group 14, the n-th turn portion and the (n + 1) -th turn portion of the exposed portion 7 of the positive electrode 8 are adjacent to each other in the longitudinal section of the electrode group 14. A reinforcing member 15 is provided between the n-th turn portion and the (n + 1) -th turn portion of the exposed portion 7 of the positive electrode 8.

  At one end 14 a of the electrode group 14, the reinforcing member 15 is provided so as to be flush with the end face of the exposed portion 7 of the positive electrode 8, so that the end face of the exposed portion 7 of the positive electrode 8 is exposed. The end surface 6a of the agent layer 6, the end surface 13a of the separator 13, and the end surface 12a of the negative electrode 12 are covered. Therefore, when the one end 14a of the electrode group 14 is viewed from above, the end surface of the exposed portion 7 of the positive electrode 8 is swirled, and the reinforcing member 15 fills the space in the swirl.

  Similarly, at the other end 14b of the electrode group 14 (lower end in FIG. 1B), the exposed portion 11 of the negative electrode 12 protrudes from the end surface 8a of the positive electrode 8 in the width direction of the electrode. Since the negative electrode 12 is wound around in the electrode group 14, the n-th turn portion and the (n + 1) -th turn portion of the exposed portion 11 of the negative electrode 12 are adjacent to each other in the longitudinal section of the electrode group 14. A reinforcing member 15 is provided between the n-th turn portion and the (n + 1) -th turn portion of the exposed portion 11 of the negative electrode 12.

  In the other end 14b of the electrode group 14, the reinforcing member 15 is provided so as to be flush with the end face of the exposed portion 11 of the negative electrode 12, and the end face of the exposed portion 11 of the negative electrode 12 is exposed. The end surface 10a of the mixture layer 10, the end surface 13a of the separator 13, and the end surface 6a of the positive electrode 6 are covered. For this reason, when one end of the electrode group 14 is viewed from above, the end surface of the exposed portion 11 of the negative electrode 12 is swirled, and the reinforcing member 15 fills the space in the swirl.

  The material of the reinforcing member 15 is not particularly limited, but it is preferable to select a material that is excellent in insulation and immersion. The reason is as follows.

  If a material excellent in conductivity is selected as the material of the reinforcing member, there is a possibility that a short circuit occurs between the positive electrode and the negative electrode. However, if a material excellent in insulation is selected as the material of the reinforcing member 15, the occurrence of the short circuit can be suppressed.

  Further, in the lithium ion secondary battery, the non-aqueous electrolyte is configured to penetrate into the electrode group 14 from the end face 8 a of the positive electrode 8, the end face 13 a of the separator 13, and the end face 12 a of the negative electrode 12. For this reason, if a material having poor immersion properties is selected as the material of the reinforcing member, the reinforcing member may inhibit the penetration of the nonaqueous electrolyte into the electrode group, and as a result, the electrode reaction is suppressed. However, if a material excellent in immersion is selected as the material of the reinforcing member 15, the non-aqueous electrolyte is not affected even if the reinforcing member 15 covers the end surface 8 a of the positive electrode 8, the end surface 13 a of the separator 13, and the end surface 12 a of the negative electrode 12. Since it penetrates into the electrode group 14, the electrode reaction can proceed.

  Specifically, a porous insulating material is preferably used as the reinforcing member 15. This is because when a porous material is used as the reinforcing member 15, the non-aqueous electrolyte is supplied into the electrode group 14 through the holes of the reinforcing member 15. Specifically, the reinforcing member 15 may be a positive electrode binder or a negative electrode binder, or may be a porous film containing insulating particles and a binder.

  Examples of the binder for the positive electrode include a fluorine-based resin such as PTFE (polytetrafluoroethylene) or PVDF (polyvinylidine difluoride). Examples of the binder for the negative electrode include SBR (styrene-butadiene rubber) or styrene-butadiene copolymer. Mention may be made of rubber particles (SBR) made of coalescence.

  As the insulating particles of the porous film, a material having excellent heat resistance and electrochemical stability is preferably selected, and an inorganic oxide such as alumina can be selected. In addition, the binder is provided to fix the insulating particles in the porous membrane, and it is preferable to select a material that is non-crystalline and excellent in heat resistance, such as a rubbery polymer containing a polyacrylonitrile group. Can be used.

  Further, the reinforcing member 15 may include a solidified non-aqueous solvent. This is because when the temperature in the lithium ion secondary battery rises due to use or the like, the nonaqueous solvent flows out of the reinforcing member 15 and is supplied to the inside of the electrode group 14. Therefore, the reinforcing member 15 decreases as the use time of the lithium ion secondary battery becomes longer. Since ethylene carbonate (EC) is often used as the non-aqueous solvent, it is preferable to use a member made of EC as the reinforcing member 15.

  As a method of providing such a reinforcing member 15 on the electrode group 14, first, the reinforcing member 15 is dissolved in an appropriate solvent to prepare a solution of the reinforcing member, and then the solution of the reinforcing member is respectively applied to the end surface of the electrode group 14. It is preferable to use a method of applying and then drying or solidifying the solution of the reinforcing member. Examples of a method for applying the solution of the reinforcing member to the end face of the electrode group 14 include an immersion method and an injection method.

  Hereinafter, the lithium ion secondary battery disclosed in Patent Document 1 and the lithium ion secondary battery disclosed in Patent Document 2 or 3 will be compared, and the lithium ion secondary battery according to the present embodiment will be described. .

  Here, in Patent Document 1, since the end surfaces of the positive electrode and the negative electrode are covered with an insulator as shown in FIG. 1 of the same document, it is considered that current cannot be collected even if a current collector plate is joined to these end surfaces. It is considered that current is collected through the current collecting lead.

  Moreover, although the lithium ion secondary battery disclosed by patent document 2 or 3 is provided with the tabless current collection structure, it is not provided with the reinforcement member.

  First, a lithium ion secondary battery disclosed in Patent Document 1 will be described.

  The lithium ion secondary battery disclosed in Patent Document 1 is presumed not to have a tabless current collecting structure as described above. Therefore, as shown in FIGS. 10A and 10B, one current collecting lead 3 (the other current collecting lead extends from the lower surface of the electrode group 94) extends from the end surface of the electrode group 94. Only. When the end face of the electrode group 94 is immersed in an insulator solution when an insulator is provided on the end face of such an electrode group 94, the tip of the current collecting lead and the end face of the electrode group are shown in FIG. An insulating solution film 4 is formed so as to connect the two points. Therefore, as shown in FIG. 10A, a sufficient amount of the insulator solution can be applied around the current collecting lead 3, but the amount of the insulator solution applied as the distance from the current collecting lead 3 increases. Decrease. In some cases, the insulator solution is not applied to the peripheral portion of the end face of the electrode group 94 (region X shown in FIG. 10A). Further, when the electrode group 94 is moved, the insulator solution may flow out from the end face of the electrode group 94, and the electrode group 94 must be left until the insulator solution is solidified.

  On the other hand, when an insulator solution is injected into the end face of the electrode group 94 when the insulator is provided on the end face of the electrode group 94, the insulator solution can be uniformly provided on the end face of the electrode group 94. However, even when the injection method is used, when the electrode group is moved, the insulator solution flows out from the end face of the electrode group 94 (regions Y1 and Y2 shown in FIG. 10B) and covers the side surface of the electrode group 94. The electrode group 94 must be allowed to stand until the insulator solution is solidified.

  Next, a lithium ion secondary battery disclosed in Patent Document 2 or 3 will be described.

  In the lithium ion secondary battery disclosed in Patent Document 2 or 3, the reinforcing member is not provided. In this case, since the thickness of the exposed portion is the same as the thickness of the current collector (specifically, several tens of μm or less), when an external force is applied to the exposed portion (for example, the current collector plate is joined to the end face of the electrode group). When the current collecting plate is pressed against the electrode group during the process, the exposed portion may be bent, and the production yield of the lithium ion secondary battery is lowered. Furthermore, when the exposed portion is bent and comes into contact with the opposite electrode plate, or when the exposed portion is bent and the separator is damaged, an internal short circuit is likely to occur.

  In the lithium ion secondary battery disclosed in Patent Document 2 or 3, the end surfaces of the positive electrode, the separator, and the negative electrode are exposed during the manufacturing process. Even after the current collector plate is joined to the end face of the exposed portion, a space exists between the current collector plate and the separator. Therefore, during the manufacturing process of the lithium ion secondary battery, unnecessary materials (specifically, spatter generated during welding) may enter the electrode group from the end faces of the positive electrode, the separator, and the negative electrode. The invading unnecessary object may break the separator, and if the separator is broken, an internal short circuit is likely to occur.

  From the above, it is considered that the lithium ion secondary battery disclosed in Patent Document 1 does not have a tabless current collecting structure. Therefore, if an immersion method is used, an insulator solution is uniformly applied to the end face of the electrode group 94. In addition, the electrode group 94 must be allowed to stand until the solution of the insulator is dried or solidified using either the dipping method or the injection method.

  In addition, in the lithium ion secondary battery disclosed in Patent Document 2 or 3, there is a risk that the exposed portion may be bent during manufacture, and there is a risk that unwanted materials may enter the electrode group and damage the separator. There is.

  However, when the reinforcing member solution is provided on the end face of the electrode group 14 in the present embodiment, the reinforcing member solution is between the adjacent exposed portions 7 and 7 of the positive electrode 8 or the adjacent exposed portions 11 and 7 of the negative electrode 12. 11 is held. In other words, the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 prevent the solution of the reinforcing member from flowing out from the end face of the electrode group 14. Therefore, it is not necessary to leave the electrode group 14 until the solution of the reinforcing member is solidified.

  Further, when a solution of a reinforcing member is provided on the end face of the electrode group 14 using the dipping method, the exposed portion 7 of the positive electrode 8 has a tip of the n-th turn portion and a tip of the (n + 1) turn portion. A film of the reinforcing member solution is formed so as to tie, and a film of the reinforcing member solution is formed so as to tie the tip of the n-th turn portion and the tip of the (n + 1) -th turn portion in the exposed portion 11 of the negative electrode 12. It is formed. Therefore, in the configuration of the electrode group 14 in the present embodiment, the solution of the reinforcing member can be uniformly applied to the end surface of the electrode group 14.

  Furthermore, in the lithium ion secondary battery according to the present embodiment, the strength of the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 can be reinforced by providing the reinforcing member 15. 7, bending of the exposed portion 7 of the positive electrode 8 can be suppressed, and bending of the exposed portion 11 of the negative electrode 12 can be suppressed even when an external force is applied to the exposed portion 11 of the negative electrode 12. Therefore, for example, it is possible to prevent the exposed portion 7 of the positive electrode 8 from coming into contact with the negative electrode 12 during manufacturing, and it is possible to prevent the separator 13 from being damaged during manufacturing, so that the probability of occurrence of an internal short circuit can be suppressed.

  In addition, in the lithium ion secondary battery according to the present embodiment, the reinforcing member 15 covers the end face 8a of the positive electrode 8, the end face 13a of the separator 13, and the end face 12a of the negative electrode 12. Intrusion into the electrode group 14 can be prevented. Therefore, the separator 13 can be prevented from being damaged during the manufacturing process, and a lithium ion secondary battery having excellent quality can be manufactured.

Furthermore, if a material having excellent insulation and liquid immersion properties is selected as the material of the reinforcing member 15, it is possible to suppress a decrease in the liquid immersion property of the non-aqueous electrolyte into the electrode group 14. Even when the non-aqueous electrolyte solvent is solidified as the member 15, the strength of the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 can be reinforced. When the electrode group 14 is pressed, the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 can be prevented from being bent, and further, unwanted substances can be prevented from entering the electrode group 14 during manufacturing. Therefore, as described above, as the lithium ion secondary battery is used, the amount of the reinforcing member 15 decreases as a result of the solvent of the nonaqueous electrolytic solution of the reinforcing member 15 penetrating into the electrode group 14, or the reinforcing member Even if 15 disappears completely, the above effect can be obtained.

  In other words, the reinforcing member 15 not only reinforces the strength of the exposed portion 7 of the positive electrode 8 or the exposed portion 11 of the negative electrode 12, but when manufacturing a lithium ion secondary battery, there is no unnecessary material inside the electrode group 14. It also functions as a shielding member that suppresses intrusion. On the other hand, it is preferable that the reinforcing member 15 is configured to allow the nonaqueous electrolytic solution to penetrate into the electrode group 14.

  Next, a method for manufacturing a lithium ion secondary battery according to this embodiment will be specifically described.

  In order to manufacture the lithium ion secondary battery according to the present embodiment, first, the positive electrode 8 and the negative electrode 12 are respectively prepared.

  In order to produce the positive electrode 8, first, an active material, a conductive agent, and a binder are kneaded together with water or an organic solvent using a kneading apparatus to produce a slurry-like positive electrode mixture.

  At this time, as the active material, lithium cobaltate, lithium cobaltate modified (such as those produced by eutectic aluminum or magnesium), lithium nickelate, lithium nickelate modified (part of nickel) Are preferably substituted with cobalt or aluminum), lithium manganate, or a complex oxide such as a modified lithium manganate. As the conductive agent, it is preferable to use one or a combination of two or more of acetylene black, ketjen black and various graphites. As the binder, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) is preferably used. Moreover, you may throw a thickener into a kneading apparatus as needed.

  Next, a slurry-like positive electrode mixture is applied on the current collector 5 (for example, made of aluminum) of the positive electrode 8 by using a die coating apparatus or the like, and dried, and the positive electrode 8 is formed on the current collector 5 of the positive electrode 8. The mixture layer 6 is formed. At this time, the slurry-like positive electrode mixture is not applied to one end of the positive electrode 8 in the width direction of the current collector 5. Thereby, the exposed portion 7 of the positive electrode 8 is formed.

  Thereafter, if necessary, the current collector 5 of the positive electrode 8 on which the mixture layer 6 of the positive electrode 8 is formed is pressed and cut into necessary dimensions. Thereby, the positive electrode 8 can be produced.

  In order to produce the negative electrode 12, first, an active material and a binder are kneaded together with water or an organic solvent using a kneading apparatus to produce a slurry-like negative electrode mixture.

  At this time, it is preferable to use various natural graphites, artificial graphites or alloy composition materials as the active material. As the binder, styrene butadiene rubber (SBR) or PVDF is preferably used. Moreover, you may throw a thickener into a kneading apparatus as needed.

  Next, a slurry-like negative electrode mixture is applied on the current collector 9 (for example, made of copper) of the negative electrode 12 by using a die coating apparatus or the like, and dried, and the negative electrode 12 is coated on the current collector 9 of the negative electrode 12. The mixture layer 10 is formed. At this time, the slurry-like negative electrode mixture is not applied to one end of the negative electrode 12 in the width direction of the current collector 9. Thereby, the exposed portion 11 is formed.

  Thereafter, if necessary, the current collector 9 of the negative electrode 12 on which the mixture layer 10 of the negative electrode 12 is formed is pressed and cut into necessary dimensions. Thereby, the negative electrode 12 can be produced.

  After producing the positive electrode 8 and the negative electrode 12, the electrode group 14 is produced. Specifically, the positive electrode 8 and the negative electrode 12 are arranged so that the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 protrude on opposite sides. Then, the separator 13 is provided between the positive electrode 8 and the negative electrode 12, and it is rolled up so that it may become a cylindrical shape or a square shape.

  At this time, as the separator 13, it is preferable to use a microporous film that has a high nonaqueous electrolyte retention and is stable under any potential of the positive electrode 6 and the negative electrode 8. As such a separator 13, for example, one made of polypropylene, one made of polyethylene, one made of polyimide, or one made of polyamide can be used.

  After the whirling, the reinforcing member 15 is provided using the dipping method. Specifically, a reinforcing member solution is prepared by dissolving or dispersing the reinforcing member in an appropriate solvent, and the reinforcing member solution is placed in a container. Thereafter, the exposed portion 7 of the positive electrode 8 is immersed in the reinforcing member solution, and after a predetermined time has elapsed, the exposed portion 7 of the positive electrode 8 is pulled up from the reinforcing member solution. At this time, the solution of the reinforcing member adhering to the end face of the exposed portion 7 of the positive electrode 8 is wiped off, and the end face of the exposed portion 7 of the positive electrode 8 is exposed while the solution of the reinforcing member is between the adjacent exposed portions 7 and 7. Make sure that is satisfied. Thereafter, an unnecessary solvent is removed from the solution of the reinforcing member by applying heat or the like, or the solution of the reinforcing member is solidified by cooling.

  For example, when EC is selected as the material of the reinforcing member 15, first, EC (melting point: 39 ° C.) is heated and melted, then the exposed portion 7 of the positive electrode 8 is immersed in liquid EC, and then the positive electrode The EC adhering to the end face of the exposed portion 7 is wiped off and then cooled.

  As another example, when a porous binder is selected as the reinforcing member 15, first, a solution is prepared by dispersing or dissolving the binder in water or an organic solvent, and then exposing the positive electrode 8 to the solution. After the part 7 is immersed, unnecessary solvent is removed.

  As yet another example, when a porous membrane containing insulating particles and a binder is selected as the reinforcing member 15, the insulating particles and the binder are first put into a kneading apparatus and kneaded with an appropriate solvent. A slurry is prepared. Next, after the exposed portion 7 of the positive electrode 8 is immersed in this slurry, unnecessary solvent is removed.

  A reinforcing member 15 is provided on the exposed portion 11 of the negative electrode 12 using the same method.

  Thereafter, current collecting plates 19 and 19 are joined to the end surfaces of the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 using a known welding method such as resistance welding or laser welding. Thereby, the current collection structure shown in FIG. 5 is produced.

  And the electrode group shown in FIG. 5 is accommodated in a case, and nonaqueous electrolyte solution is inject | poured into a case. Then, a lithium ion secondary battery can be manufactured by sealing a required part.

<< Embodiment 2 of the Invention >>
FIG. 6 is a longitudinal sectional view showing the configuration of the current collecting structure in the second embodiment.

  The exposed portion 7 of the positive electrode 8 protrudes from the surface of the reinforcing member 15 in the width direction of the electrode at one end 24a of the electrode group 24 in the present embodiment, and the exposed portion 11 of the negative electrode 12 extends from the surface of the reinforcing member 15 to the reinforcing member. It protrudes from the surface of 15 in the width direction of the electrode. Even with such a configuration, substantially the same effect as in the first embodiment can be obtained.

  The method for producing the reinforcing member having the shape shown in FIG. 6 is not particularly limited. However, if the material of the reinforcing member 15 has heat shrinkability, the structure shown in FIG.

<< Embodiment 3 of the Invention >>
FIG. 7 is a longitudinal sectional view showing the configuration of the current collecting structure in the third embodiment.

  In the present embodiment, the reinforcing member 15 covers the end surface 8a of the positive electrode 8, the end surface 13a of the separator 13, and the end surface 12a of the negative electrode 12 as in the first embodiment. However, as shown in FIG. 7, at one end 34 a of the electrode group 34, the thickness of the portion of the reinforcing member 15 that covers the end surface 12 a of the negative electrode 12 is the same as the end surface 6 a of the positive electrode 8 of the reinforcing member 15. It is thinner than the thickness of the covered part. In the other end 34 b of the electrode group 34, the thickness of the portion of the reinforcing member 15 that covers the end surface 8 a of the positive electrode 8 is greater than the thickness of the portion of the reinforcing member 15 that covers the end surface 10 a of the mixture layer 10 of the negative electrode 12. thin.

  Even with such a configuration, substantially the same effect as in the first embodiment can be obtained. Further, in the configuration shown in FIG. 7, since the reinforcing member 15 is thinner than in the case of the first embodiment, the liquid immersion is superior to the case of the first embodiment.

<< Reference Form of Invention >>
FIG. 8 is a longitudinal sectional view showing the configuration of the current collecting structure in the reference embodiment .

In the reference form , as shown in FIG. 8, the reinforcing member 15 covers only the end surface 6 a of the mixture layer 6 of the positive electrode 8 at one end 44 a of the electrode group 44, and the negative electrode 12 at the other end 44 b of the electrode group 44. Only the end surface 10a of the mixture layer 10 is covered.

  In such a configuration, there is a portion where the reinforcing member 15 is not provided at the one end 44a and the other end 44b of the electrode group 44, so that there is a high probability that an unnecessary object enters the electrode group 44 during the manufacturing process. Although it involves danger, the immersion property of the non-aqueous electrolyte can be improved. That is, the smaller the range in which the reinforcing member 15 is provided, or the thinner the reinforcing member 15 is, the higher the immersion property of the nonaqueous electrolyte solution in the electrode group 44 can be. On the other hand, the wider the range in which the reinforcing member 15 is provided, or the thicker the reinforcing member 15, the more the unnecessary material can be prevented from entering, and the strength of the exposed portion 7 of the positive electrode 8 and the exposed portion 11 of the negative electrode 12 is increased. Can be reinforced.

  As a method for producing the reinforcing member having the shape shown in FIG. 8, the dipping method described in the first embodiment or the like may be used, but the reinforcing member 15 is formed before winding the positive electrode 8 and the negative electrode 12. Also good.

  Specifically, after producing the positive electrode 8 according to the method described in the first embodiment, the solution of the reinforcing member is applied to the exposed portion 7 of the positive electrode 8 using a die coating apparatus or a gravure apparatus, and cooled or dried. Let Similarly, after producing the negative electrode 12 according to the method described in the first embodiment, the reinforcing member solution is applied to the exposed portion 11 of the negative electrode 12 using a die coating apparatus, a gravure apparatus, or the like, and cooled or dried.

  Thereafter, a lithium ion secondary battery can be manufactured by performing the method described in the first embodiment.

<< Other Embodiments >>
The present invention may be configured as follows with respect to the above embodiment.

In the first to third embodiments, the positive electrode and the negative electrode are wound via the separator, but the positive electrode and the negative electrode may be stacked via the separator. When the positive electrode and the negative electrode are laminated, the reinforcing member is provided between the exposed portion of the nth positive electrode 8 and the exposed portion of the (n + 1) th positive electrode at one end of the electrode group. The other end of the group is provided between the exposed portion of the nth negative electrode and the exposed portion of the (n + 1) th negative electrode.

  In addition, when the positive electrode and the negative electrode are wound, the electrode group may be formed in a cylindrical shape or a rectangular tube shape.

  Moreover, in the said embodiment, although the non-aqueous electrolyte was hold | maintained at least by the separator, for example, the gel-like non-aqueous electrolyte may be hold | maintained at least by the separator. Even when the gel-like nonaqueous electrolyte is held at least by the separator, by providing a reinforcing member, the strength of the exposed portion can be reinforced and unwanted matter can enter the electrode group. Can be suppressed.

In the example, a lithium ion secondary battery was manufactured, and a short circuit inspection and a DC resistance measurement were performed.
Example 1
First, a positive electrode was produced.

Specifically, a saturated aqueous solution was prepared by adding a predetermined ratio of Co and Al sulfate to a NiSO ₄ aqueous solution. While stirring the saturated aqueous solution, sodium hydroxide solution was slowly added dropwise to the saturated solution. As a result, the saturated solution was neutralized, and as a result, a precipitate of ternary nickel hydroxide Ni _0.7 Co _0.2 Al _0.1 (OH) ₂ could be generated (coprecipitation method). The produced precipitate was filtered, washed with water, and dried at 80 ° C. The average particle diameter of the obtained nickel hydroxide was about 10 μm.

The obtained Ni _0.7 Co _0.2 Al _0.1 (OH) ₂ was heat-treated at 900 ° C. for 10 hours in the atmosphere to obtain nickel oxide Ni _0.7 Co _0.2 Al _0.1 O 2. At this time, the nickel oxide Ni _0.7 Co _0.2 Al _0.1 O obtained using the powder X-ray diffraction method was diffracted to confirm that the nickel oxide Ni _0.7 Co _0.2 Al _0.1 O was a single phase nickel oxide. Then, lithium hydroxide monohydrate is added to nickel oxide Ni _0.7 Co _0.2 Al _0.1 O so that the sum of the number of Ni atoms, the number of Co atoms, and the number of Al atoms is equal to the number of Li atoms. In addition, a lithium nickel composite oxide LiNi _0.7 Co _0.2 Al _0.1 O ₂ was obtained by performing a heat treatment at 800 ° C. for 10 hours in dry air.

When the lithium nickel composite oxide LiNi _0.7 Co _0.2 Al _0.1 O ₂ obtained by the powder X-ray diffraction method is diffracted, the lithium nickel composite oxide LiNi _0.7 Co _0.2 Al _0.1 O ₂ is a single-phase hexagonal layered layer. The structure was confirmed, and it was confirmed that Co and Al were dissolved in the lithium nickel composite oxide. Then, the lithium nickel composite oxide was pulverized and classified into powder. The average particle diameter of this powder was 9.5 μm. When the specific surface area of this powder was determined according to the BET method, the specific surface area was 0.4 m ² / g.

  3 kg of the obtained lithium nickel composite oxide, 90 g of acetylene black, and 1 kg of PVDF solution were kneaded together with an appropriate amount of N-methyl-2-pyrrolidone (NMP) in a planetary mixer to form a slurry-like positive electrode mixture Was made. This positive electrode mixture was applied onto an aluminum foil having a thickness of 20 μm and a width of 150 mm. At this time, an uncoated part having a width of 5 mm was formed at one end in the width direction of the aluminum foil. Thereafter, the positive electrode mixture was dried to form a positive electrode mixture layer on the aluminum foil. And after pressing so that the total thickness of the thickness of the positive electrode mixture layer and the thickness of the aluminum foil is 100 μm, the electrode plate is cut so that the width of the electrode plate is 105 mm and the width of the mixture application portion is 100 mm, A positive electrode having a tabless current collecting structure shown in FIG. 2 was produced.

  Next, a negative electrode was produced.

  Specifically, 3 kg of artificial graphite, 75 g of an aqueous solution (weight of solid content: 40% by weight) of rubber particles (binder) made of styrene-butadiene copolymer, and carboxymethylcellulose (CMC). 30 g was kneaded with an appropriate amount of water in a planetary mixer to prepare a slurry-like negative electrode mixture. This negative electrode mixture was applied onto a copper foil having a thickness of 10 μm and a width of 150 mm. At this time, an uncoated part (exposed part) having a width of 5 mm was formed at one end in the width direction of the copper foil. Thereafter, the negative electrode mixture was dried to form a negative electrode mixture layer on the copper foil. Then, after pressing so that the total thickness of the negative electrode mixture layer and the copper foil becomes 110 μm, the electrode plate is cut so that the width of the electrode plate is 110 mm and the width of the mixture application portion is 105 mm. A negative electrode having a tabless current collecting structure shown in FIG.

  A polyethylene separator was sandwiched between the produced positive electrode and negative electrode, and the exposed portion of the positive electrode and the exposed portion of the negative electrode were protruded in opposite directions from the end face of the separator. Thereafter, the positive electrode, the negative electrode, and the separator were wound into a cylindrical shape.

  Subsequently, a reinforcing member was formed on the exposed portion.

  Specifically, EC, which is a solvent for the nonaqueous electrolytic solution, was heated to 50 ° C. and melted to obtain liquid EC. A 10 mm portion from the end face of the exposed portion of the positive electrode was immersed in liquid EC. Thereafter, the liquid EC was solidified by allowing to stand at room temperature. Similarly, a 10 mm portion from the end face of the exposed portion of the negative electrode was immersed in liquid EC. Thereafter, the liquid EC was solidified by allowing to stand at room temperature. Thereby, the reinforcing member was provided in the exposed part of the positive electrode and the exposed part of the negative electrode, and an electrode group could be formed.

  Thereafter, a current collecting structure was formed.

  Specifically, first, the circular portion of the aluminum current collector having the shape shown in FIGS. 3A and 3B is pressed against the end surface of the exposed portion of the positive electrode, and the vertical hole is removed so as to remove the central hole. The cross was irradiated with a laser. Thereby, the current collector plate made of aluminum could be joined to the end face of the exposed portion of the positive electrode.

  Also, press the circular part of the nickel current collector plate with the shape shown in Figs. 3 (a) and 3 (b) against the end face of the exposed part of the negative electrode, and irradiate the laser beam on the vertical and horizontal characters so as to remove the central hole. did. Thereby, the nickel current collector plate could be joined to the end face of the exposed portion of the negative electrode, and a current collector structure was formed.

The formed current collecting structure was inserted into a nickel-plated iron cylindrical case. Thereafter, the tab portion of the nickel current collector plate was bent and resistance welded to the bottom of the case. Further, the tab portion of the aluminum current collector plate was laser welded to the sealing plate, and a non-aqueous electrolyte was injected into the case. At this time, the non-aqueous electrolyte is composed of lithium hexafluorophosphate (solute) as a solute in a mixed solvent in which EC and ethyl methyl carbonate (EMC) are mixed at a mixing ratio of 1: 3 by volume. It was prepared by dissolving LiPF6) at a concentration of 1 mol / dm3. Thereafter, the sealing plate was crimped on the case and sealed. Thus, a lithium ion secondary battery having a nominal capacity of 5 Ah was produced. This battery is referred to as battery A.
( Reference Example 1 )
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the production method of the negative electrode was changed.

Specifically, the negative electrode mixture was applied to the entire surface of the copper foil and cut so as to have a width of 105 mm. Thereafter, the mixture layer was peeled off at one end in the longitudinal direction of the copper foil to form an exposed portion having a width of 7 mm. A nickel lead having a width of 5 mm was resistance-welded to the exposed portion. This produced the negative electrode shown in FIG. And the lithium ion secondary battery was produced like Example 1 except not having provided the reinforcement member in the negative electrode side after rolling a positive electrode and a negative electrode. This battery is referred to as a battery B.
( Reference Example 2 )
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the manufacturing method of the positive electrode was changed.

Specifically, the positive electrode material mixture was applied to the entire surface of the aluminum foil and cut so as to have a width of 100 mm. Thereafter, the mixture layer was peeled off at one end in the longitudinal direction of the aluminum foil to form an exposed portion having a width of 7 mm. An aluminum lead having a width of 5 mm was resistance-welded to the exposed portion. This produced the positive electrode shown in FIG. And the lithium ion secondary battery was produced like Example 1 except not having provided the reinforcement member in the positive electrode side after winding a positive electrode and a negative electrode. This battery is referred to as a battery C.
(Example 2 )
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the material of the reinforcing member was changed.

Specifically, a PVDF solution dissolved in NMP was prepared. In the PVDF solution, a portion from the end face of the exposed portion of the positive electrode to 10 mm was immersed, and then heated to 80 ° C. to remove NMP. Similarly, a portion from the end face of the exposed portion of the negative electrode to 10 mm was immersed in the PVDF solution, and then heated to 80 ° C. to remove NMP. This battery is referred to as a battery D.
( Reference Example 3 )
A lithium ion secondary battery was produced in the same manner as in Reference Example 1 except that the material of the reinforcing member was changed.

Specifically, PTFE was dispersed in water to prepare a solution. The portion from the end face of the exposed portion of the positive electrode to 10 mm was immersed in the solution, and then heated to 80 ° C. to remove water. This battery is referred to as a battery E.
( Reference Example 4 )
A lithium ion secondary battery was produced in the same manner as in Reference Example 2 except that the material of the reinforcing member was changed.

Specifically, an aqueous solution of rubber particles (SBR, binder) made of a styrene-butadiene copolymer was prepared. The part from the end surface of the exposed part of the negative electrode to 10 mm was immersed in the solution, and then heated to 80 ° C. to remove water. This battery is referred to as a battery F.
(Example 3 )
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the material of the reinforcing member was changed.

  Specifically, 1000 g of alumina having an average particle size of 0.3 μm and 375 g of polyacrylonitrile-modified rubber (binder) (solid content is 8% by weight) together with an appropriate amount of NMP solvent and planetary A slurry-like porous material was produced by kneading in a mixer.

A portion from the end face of the exposed portion of the positive electrode to 10 mm was immersed in the slurry-like porous material, and then heated to 80 ° C. to remove the NMP solvent. Moreover, the part from the end surface of the exposed part of a negative electrode to 10 mm was immersed in the slurry-like porous material, Then, it heated at 80 degreeC and the NMP solvent was removed. This battery is referred to as a battery G.
( Reference Example 5 )
Except that the lead type negative electrode described in Reference Example 1 and the porous membrane slurry described in Example 3 were used, and the reinforcing member was not provided on the negative electrode side after the positive electrode and the negative electrode were wound around, the same as in Example 3. Thus, a lithium ion secondary battery was produced. This battery is referred to as a battery H.
( Reference Example 6 )
Similar to Example 3 except that the lead-type positive electrode plate described in Reference Example 2 and the porous membrane slurry described in Example 3 were used, and the positive electrode and the negative electrode were wound and no reinforcing member was provided on the positive electrode side. Thus, a lithium ion secondary battery was produced. This battery is referred to as a battery I.
(Example 4 )
A lithium ion secondary battery was produced according to the method described in Example 1 except for the production method of the positive electrode and the negative electrode.

Specifically, liquid EC heated to 50 ° C. was applied to the exposed portions on both sides of the positive electrode and the exposed portions on both sides of the negative electrode. At this time, liquid EC was not applied to the range of 1 mm from the end of the exposed portion of the positive electrode and the exposed portion of the negative electrode. Then, it was cooled. Thereafter, in the positive electrode, the thickness of the reinforcing member was set to 40 μm, which was substantially the same as the thickness of the positive electrode mixture layer, and in the negative electrode, the thickness of the reinforcing member was set to 50 μm, which was substantially the same as the thickness of the negative electrode mixture layer. And the lithium ion secondary battery was produced like Example 1 except not having provided the reinforcement member after winding a positive electrode and a negative electrode. This battery was designated as battery J.
(Example 5 )
A lithium ion secondary battery was produced according to the method described in Example 2 except for the production method of the positive electrode and the negative electrode.

Specifically, a PVDF solution dissolved in NMP was applied to the exposed portions on both sides of the positive electrode and the exposed portions on both sides of the negative electrode. At this time, the PVDF solution was not applied to a range of 1 mm from the end of the exposed portion of the positive electrode and the exposed portion of the negative electrode. Then, it was made to dry and NMP was removed. Thereafter, in the positive electrode, the thickness of the reinforcing member was set to 40 μm, which was substantially the same as the thickness of the positive electrode mixture layer, and in the negative electrode, the thickness of the reinforcing member was set to 50 μm, which was substantially the same as the thickness of the negative electrode mixture layer. And the lithium ion secondary battery was produced like Example 2 except not having provided the reinforcement member after rolling a positive electrode and a negative electrode. This battery was designated as battery K.
(Example 6 )
A lithium ion secondary battery was produced according to the method described in Example 3 except for the production method of the positive electrode and the negative electrode.

Specifically, a slurry-like porous material using NMP as a solvent was applied to the exposed portions on both sides of the positive electrode and the exposed portions on both sides of the negative electrode. At this time, the slurry-like porous material was not applied to a range of 1 mm from the end of the exposed portion of the positive electrode and the exposed portion of the negative electrode. Then, it was made to dry and NMP was removed. Thereafter, in the positive electrode, the thickness of the reinforcing member was set to 40 μm, which was substantially the same as the thickness of the positive electrode mixture layer, and in the negative electrode, the thickness of the reinforcing member was set to 50 μm, which was substantially the same as the thickness of the negative electrode mixture layer. And the lithium ion secondary battery was produced like Example 2 except not having provided the reinforcement member after rolling a positive electrode and a negative electrode. This battery was designated as a battery L.
(Comparative Example 1)
A lithium ion secondary battery was prepared in the same manner as in Example 1 except that the negative electrode described in Reference Example 1 and the positive electrode described in Reference Example 2 were used, and the reinforcing member was not provided after the positive electrode and the negative electrode were rolled. Produced. This battery is referred to as a battery M.
(Comparative Example 2)
Without providing the reinforcing member, the current collecting plate shown in FIGS. 4A and 4B was used as a current collecting plate for the positive electrode, and this current collecting plate was pressed against the end face of the exposed portion of the positive electrode to be joined. Except for this, a lithium ion secondary battery was fabricated in the same manner as in Example 1. This battery is referred to as a battery N.

  Twenty pieces of each of the above batteries were produced. The following evaluation was performed on each obtained battery.

(Short-circuit inspection)
After the current collector plate was welded to the electrode group, a voltage of 250 V was applied between the positive electrode terminal and the negative electrode terminal, and the presence or absence of leakage current at that time was confirmed. Thereby, the presence or absence of the short circuit of an electrode group was confirmed. About the electrode group of the comparative example 1, this test | inspection was implemented after winding an electrode plate.

(DC internal resistance measurement test)
An electrode group in which no abnormality was found in the short-circuit inspection described above was assembled into a battery. Then, 3 cycles charge / discharge was implemented in the voltage range of 3-4.2V by the electric current value of 1A in 25 degreeC environment, and the battery capacity was confirmed. Thereafter, each battery is charged at a constant current up to 60% in a 25 ° C. environment, charged and discharged for 10 seconds at various constant currents in a range of 5 to 50 A, and each pulse is applied. The voltage at the later 10 seconds was measured and plotted against the current value. Further, each voltage plot on the discharge pulse side was linearly approximated by the least square method, and the value of the slope was defined as direct current internal resistance (DCIR). As the DCIR is smaller, a larger output can be obtained in a certain time.

  Table 1 shows the configuration of the battery in each example and the evaluation results. In Table 1, “DCIR” indicates an average value in each example. Regarding the battery capacity, it was confirmed that the nominal capacity was around 5 Ah in any battery. Further, it was confirmed that each of the current collector plates had sufficient welding strength for the electrode group.

  Consider the results in Table 1.

  First, the number of short circuits in the electrode group will be considered.

  In the battery N having a tabless current collecting structure and not provided with the reinforcing member, the electrode group was short-circuited in five lithium ion secondary batteries out of 20 inspections. When the electrode group in which the short circuit occurred was disassembled and observed, it was confirmed that the separator had a hole. This hole was presumed to be formed as a result of spatter entering the inside of the separator when the current collector plate was laser welded to the end face of the electrode group. Moreover, when the circumference | surroundings of the part welded to the current collector plate among current collectors were observed, the bending of the exposed part or the buckling of the exposed part was confirmed. It is estimated that the bending of the exposed portion or the buckling of the exposed portion was formed by pressing the current collector plate against the electrode group. It is thought that many short circuits occurred due to these factors.

  On the other hand, in the batteries A to I and the battery M, the number of short circuits was reduced compared to the battery N. When the battery electrode group short-circuited among the batteries A to I and the battery M was disassembled and observed, the buckling of the exposed portion and the opening of the separator could not be confirmed. From these results, it is considered that by providing the reinforcing member, it was possible to reinforce the strength of the exposed portion and to suppress spatter and the like from being scattered inside the electrode group. The reason for the confirmation of the short circuit is that there is a black spot on the surface of the separator inside the electrode group, so it is assumed that this is a physical reason such as foreign matter entering the electrode group. ing.

  Also, in the batteries J to L, the number of short circuits was reduced as compared with the battery N. When the battery electrode group short-circuited among the batteries J to L was disassembled and confirmed, the degree of bending of the exposed portion was smaller than that of the battery N. The reason for this is considered that the reinforcing member was formed around the exposed portion, so that the strength of the exposed portion could be reinforced compared to the case where the reinforcing member was not provided. Moreover, the partial hole resulting from the sputter | spatter which generate | occur | produced when the current collector plate was laser-welded was confirmed by the separator. It was speculated that a short circuit occurred when a hole was opened in the part between the positive electrode and the negative electrode of the separator, but it was speculated that a short circuit could be prevented if a hole was opened in the part of the separator that was in contact with the reinforcing member. .

  From the above results, it is estimated that the buckling of the exposed portion can be reduced because the strength of the exposed portion can be reinforced by providing the reinforcing member. In addition, it was difficult to prevent the occurrence of a short circuit when a hole was opened in the part sandwiched between the positive electrode and the negative electrode in the separator. Since generation | occurrence | production of a short circuit could be suppressed, it is estimated that generation | occurrence | production of a short circuit could be suppressed by providing a reinforcement member.

  Next, the results of DCIR will be considered.

  In the battery M that collects current through the current collecting lead, the DCIR was 10.9 mΩ, which was larger than the DCIR of other batteries. On the other hand, in the batteries A, D, G, J to L and N having the tabless current collecting structure, the DCIR is 6.2 to 6.6 mΩ, which is about 40% lower than the DCIR of the battery M. did it. This is because the current collection resistance can be reduced by adopting the tabless current collection structure. Also, in the batteries B, C, E, F, H, and I in which one of the positive electrode and the negative electrode has a tabless current collecting structure, the DCIR can be reduced by about 20% compared to the DCIR of the battery M. did it.

  From the above results, the batteries A to L were able to suppress the occurrence of an internal short circuit during welding compared to the battery N, and the DCIR could be reduced compared to the battery M. Therefore, in the batteries A to L, an internal short circuit generated when the battery was manufactured could be suppressed, and the resistance was low and a high output could be obtained.

  The present invention is extremely useful, for example, in the field of lithium ion secondary batteries that require high rate characteristics. The lithium ion secondary battery of the present invention is useful as a drive power source for notebook computers, mobile phones, digital still cameras, electric tools, electric vehicles, and the like.

It is a figure which shows the structure of the electrode group in Embodiment 1 of this invention, (a) is the perspective view, (b) is a longitudinal cross-sectional view in IB area | region shown to (a). It is a top view of the positive electrode and negative electrode of this invention. It is a figure which shows the structure of a current collecting plate, (a) is the top view, (b) is the sectional drawing. It is a figure which shows another structure of a current collecting plate, (a) is the top view, (b) is the sectional drawing. It is a longitudinal cross-sectional view which shows the current collection structure in Embodiment 1 of this invention. It is a longitudinal cross-sectional view which shows the current collection structure in Embodiment 2 of this invention. It is a longitudinal cross-sectional view which shows the current collection structure in Embodiment 3 of this invention. It is a longitudinal cross-sectional view which shows the current collection structure in a reference form . It is a top view of the conventional positive electrode and negative electrode. (A) And (b) is a longitudinal cross-sectional view which shows a structure when the reinforcement member is provided in the conventional lithium ion secondary battery, respectively.

Explanation of symbols

5 Current collector 6 Mixture layer 6a End face 7 Exposed portion 8 Positive electrode 8a End face 9 Current collector 10 Mixture layer 10a End face 11 Exposed portion 12 Negative electrode 12a End face 13 Separator 14, 24, 34, 44 Electrode group 15 Reinforcing member 19, 29 Current collector

Claims (6)

An electrode group in which a positive electrode and a negative electrode are wound or laminated with a separator interposed therebetween, a non-aqueous electrolyte held in the separator, and a current collector plate joined to the electrode group,
At one end in the width direction of one of the positive electrode and the negative electrode, there is an exposed portion where the current collector is exposed from the mixture layer,
In the electrode group, the exposed part protrudes in the width direction of the electrode from the end face of the separator and the end face of the other electrode, and the current collector plate is joined to the end face of the exposed part,
Between the exposed portion adjacent reinforcing member for reinforcing the strength of the exposed portion is provided et al is,
The non-aqueous electrolyte secondary battery , wherein the reinforcing member covers the end surface of the mixture layer of the one electrode, the end surface of the separator, and the end surface of the other electrode in contact with each other . The nonaqueous electrolyte secondary battery according to claim 1 ,
The thickness of the portion of the reinforcing member that covers and covers the end surface of the other electrode is the thickness of the portion of the reinforcing member that covers and contacts the end surface of the mixture layer of the one electrode. A non-aqueous electrolyte secondary battery that is thinner than the thickness. The nonaqueous electrolyte secondary battery according to claim 1 or 2 ,
The reinforcing member is a porous nonaqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 3 ,
The non-aqueous electrolyte secondary battery, wherein the reinforcing member is a binder. The nonaqueous electrolyte secondary battery according to claim 1 or 2 ,
The non-aqueous electrolyte contains a non-aqueous solvent and a solute,
The reinforcing member includes a non-aqueous electrolyte secondary battery including the solidified non-aqueous solvent. The nonaqueous electrolyte secondary battery according to claim 5 ,
The reinforcing member is made of ethylene carbonate, a nonaqueous electrolyte secondary battery

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