JP2016058314A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preventing overcurrent without increasing the internal resistance.SOLUTION: A secondary battery includes a battery element that can be charged and discharged, a positive electrode terminal connected with the battery element, a negative electrode terminal 6 connected with the battery element, and a reaction material layer 20 formed on the surface of the positive electrode terminal or the negative electrode terminal 6. Sulfur contained in the reaction material layer 20 reacts on the copper contained in the positive electrode terminal or the negative electrode terminal 6 as the temperature rises, to create a product material layer 21 containing copper sulfide having a volume increased compared with a portion in the positive electrode terminal or a negative electrode terminal 20 contributive to the reaction.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a secondary battery.

  Secondary batteries such as lithium ion batteries and all solid state batteries are used in various fields such as automobiles and portable devices due to the recent improvement in performance. As its use progresses, further improvements in performance and safety are desired for secondary batteries.

  Techniques for preventing overcharge, overdischarge, and overcurrent have been studied as methods for improving safety. For example, Patent Document 1 discloses a technique of inserting a porous polymer that expands due to a temperature rise into an electrode active material layer or between an electrode active material layer and a separator as prevention of overcurrent. According to Patent Document 1, the electrolyte solution is also present in the porous polymer during normal operation and can move through the porous polymer. However, when an overcurrent occurs, the porous polymer expands due to temperature rise. The liquid is drained from the porous polymer and cannot move through the porous polymer. As a result, the porous polymer has a high resistance when an overcurrent is generated as compared with the normal operation, and suppresses or cuts off the current.

JP 2001-229912 A

  In the method of inserting the porous polymer in the electrode active material layer or between the electrode active material layer and the separator as in Patent Document 1, the electrolyte is also contained in the porous polymer during normal operation. An increase in internal resistance due to the porous polymer is inevitable. In other words, the technique of Patent Document 1 sacrifices internal resistance in order to realize a function of preventing overcurrent. A technique for preventing overcurrent without increasing the internal resistance is desired.

  According to the present invention, a chargeable / dischargeable battery element, a positive terminal portion connected to the battery element, a negative terminal portion connected to the battery element, and a surface of the positive terminal portion or the negative terminal portion A reaction material layer formed, and sulfur contained in the reaction material layer reacts with copper contained in the positive electrode terminal portion or the negative electrode terminal portion due to a temperature rise, and thereby the positive electrode terminal portion or the negative electrode terminal portion. A product material layer containing copper sulfide having a volume larger than that of the portion contributing to the reaction is generated.

  According to the present invention, overcurrent can be prevented without increasing the internal resistance.

FIG. 1 is a schematic top view illustrating a configuration example of the secondary battery according to the embodiment. FIG. 2 is a schematic partial side view showing a configuration example of the battery element according to the embodiment. FIG. 3 is a schematic partial side view showing a configuration example of the secondary battery according to the first embodiment. FIG. 4 is a schematic perspective view showing the relationship between the reactant layer and the extension member according to the first embodiment. FIG. 5 is a schematic partial top view illustrating a configuration example of the secondary battery according to the second embodiment. FIG. 6 is a schematic side view showing the relationship between the reactant layer and the weld according to the second embodiment.

  According to the present invention, a chargeable / dischargeable battery element, a positive terminal portion connected to the battery element, a negative terminal portion connected to the battery element, and a surface of the positive terminal portion or the negative terminal portion A reaction material layer formed, and sulfur contained in the reaction material layer reacts with copper contained in the positive electrode terminal portion or the negative electrode terminal portion due to a temperature rise, and thereby the positive electrode terminal portion or the negative electrode terminal portion. A product material layer containing copper sulfide having a volume larger than that of the portion contributing to the reaction is generated.

  According to such a secondary battery, when an overcurrent occurs and the temperature of the positive electrode terminal portion or the negative electrode terminal portion rises due to Joule heat, it is included in the copper and the reactant layer contained in the positive electrode terminal portion or the negative electrode terminal portion. As a result, the product material layer containing copper sulfide is generated. At that time, the volume of copper sulfide in the product material layer expands more than the volume of copper in the portion contributing to the reaction in the positive electrode terminal portion or the negative electrode terminal portion. Therefore, the structure of the copper sulfide in the product material layer is sparse and its strength is low. As a result, fracture occurs in the copper sulfide of the product material layer due to stress generated between the copper sulfide of the product material layer and the copper of the adjacent material during volume expansion, or the product material layer is sulfided. Fracture occurs at the boundary between copper and the adjacent material copper. That is, the positive electrode terminal portion or the negative electrode terminal portion is cut. Thereby, an overcurrent can be interrupted. Here, the sulfur in the reactant layer is formed on the surface of all or part of the copper in the positive electrode terminal portion or the negative electrode terminal portion, but hardly reacts with the positive electrode terminal portion or the negative electrode terminal portion unless overcurrent occurs. Therefore, it does not affect the flow of current at the positive terminal portion or the negative terminal portion. Therefore, this secondary battery can cut off the overcurrent without causing an increase in internal resistance during normal operation. Further, when forming the reactant layer, it is not necessary to reduce the cross-sectional area of the positive electrode terminal portion itself or the negative electrode terminal portion itself. Furthermore, since the reactant layer is thin and light, there is no risk of reducing the energy density of the secondary battery.

  Examples of the material for the reactant layer include materials containing sulfur, and sulfur is preferably used. As the other material, a material that is very reactive at high temperature and reacts with a metal used for the positive electrode terminal portion or the negative electrode terminal portion to form a product layer can be considered. However, the product substance layer has a density relatively lower than the density of the material used for the positive electrode terminal portion or the negative electrode terminal portion due to volume expansion during the reaction, and has a relatively sparse structure. Moreover, as a material of a positive electrode terminal part or a negative electrode terminal part, the material containing copper is mentioned, Copper is used suitably. As the other material, a material that causes the above reaction with the material of the reactant layer and forms the above-mentioned product substance can be considered.

  The positive electrode terminal portion includes a positive electrode extension member extending from an end of the positive electrode current collector of the battery element, and a positive electrode tab connected to the positive electrode extension member, and the negative electrode terminal portion of the battery element You may provide the negative electrode extension member extended from the edge part of a negative electrode electrical power collector, and the negative electrode tab connected to the said negative electrode extension member. In this case, the reactive substance layer is a surface of the positive electrode tab that connects the positive electrode extension member and the positive electrode tab, or a positive electrode welded portion that connects the positive electrode extension member and the positive electrode tab. It is preferable to form in the negative electrode welding part which connects a tab, or those peripheral parts.

  When the secondary battery has a structure in which a plurality of single cells are stacked, a plurality of positive electrode extension members are collectively connected to the positive electrode tab at the positive electrode welding portion. Similarly, a plurality of negative electrode extension members are collectively connected to the negative electrode tab at the negative electrode weld. Therefore, for example, a plurality of positive electrode extension members are collectively removed from the positive electrode tab by forming a reactive material layer on the surface of the positive electrode tab and around the positive electrode weld. That is, the connection between the plurality of positive electrode extension members and the positive electrode tab is collectively cut. As a result, it is possible to reliably prevent a phenomenon in which a positive electrode extension member that is not cut remains, current concentrates on the positive electrode extension member, and heat generation further increases. The case where the reactive material layer is formed on the surface of the negative electrode tab and around the negative electrode welded portion is the same as the case of the surface of the positive electrode tab.

  The method for producing the reactive material layer 20 is not particularly limited as long as a film can be formed. For example, any coating method such as a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, and a screen printing method. Thus, a method of applying the slurry containing the material of the reactant layer 20 to the surface of all or a part of the positive electrode terminal portion or the negative electrode terminal portion and drying the slurry is exemplified. The slurry is formed, for example, by mixing a binder with sulfur powder. Examples of the binder include PVDF. As another method, a method of forming a film on all or a part of the positive electrode terminal portion or the negative electrode terminal portion by sputtering using a target containing the material of the reactant layer 20 is exemplified.

  Hereinafter, a secondary battery according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic top view showing a configuration example of the secondary battery A according to the present embodiment. The secondary battery A includes a battery element 1, a laminate film 2, a positive electrode terminal portion 3, and a negative electrode terminal portion 4. The battery element 1 is a chargeable / dischargeable battery. The positive electrode terminal portion 3 is a positive electrode side terminal of the secondary battery A, and includes a positive electrode extension member 16 a and a positive electrode tab 5. The positive electrode extension member 16a is a member extending from an end portion of a positive electrode current collector (described later), and may be integrated with the positive electrode current collector. The positive electrode tab 5 is a member that pulls out the positive electrode extension member 16 a to the outside, and is connected to the positive electrode extension member 16 a and the positive electrode welding portion 18. That is, the positive electrode extension member 16a is welded to the positive electrode tab 5 by a method such as ultrasonic welding. The negative electrode terminal portion 4 is a terminal on the negative electrode side of the secondary battery A, and includes a negative electrode extension member 17 a and a negative electrode tab 6. The negative electrode extension member 17a is a member extending from an end portion of a negative electrode current collector (described later), and may be integrated with the negative electrode current collector. The negative electrode tab 6 is a member that pulls out the negative electrode extension member 17 a to the outside, and is connected to the negative electrode extension member 17 a by the negative electrode welding portion 18. That is, the negative electrode extension member 17a is welded to the negative electrode tab 6 by a method such as ultrasonic welding. The laminate film 2 is a film that protects the battery element 1, the positive electrode terminal portion 3, and the negative electrode terminal portion 4, and covers the battery element 1, the positive electrode terminal portion 3, and the negative electrode terminal portion 4 from both side surfaces. However, the illustration of the laminate film on the near side of the drawing is omitted.

  FIG. 2 is a schematic partial side view showing a configuration example of the battery element 1. The battery element 1 has a configuration in which a plurality of single cells 10 are stacked. The unit cell 10 is a chargeable / dischargeable cell, and includes a positive electrode layer 11, a negative electrode layer 12, and an electrolyte layer 13 disposed between the positive electrode layer 11 and the negative electrode layer 12. Examples of the electrolyte layer 13 include a solid electrolyte, an electrolytic solution, and a gel electrolyte containing the electrolytic solution. The electrolyte layer 13 may include a separator. The positive electrode layer 11 includes a positive electrode active material layer 14 containing a positive electrode active material, and a positive electrode current collector 16 that collects current from the positive electrode active material layer 14. The positive electrode extension member 16 a is a portion obtained by extending the end of the positive electrode current collector 16. The negative electrode layer 12 includes a negative electrode active material layer 15 containing a negative electrode active material, and a negative electrode current collector 17 that collects current from the negative electrode active material layer 15. The negative electrode extension member 17 a is a portion obtained by extending the end of the negative electrode current collector 17. Adjacent single cells 10 are stacked such that, for example, the positive electrode layers 11 or the negative electrode layers 12 are in contact with each other with a separator interposed therebetween.

  FIG. 3 is a schematic partial side view showing a configuration example of the secondary battery A. In this figure, a part of the secondary battery A is enlarged, and the vicinity of the negative electrode tab 6 and the negative electrode extension member 17a is viewed from the side. A plurality of negative electrode extension members 17 a extending from the plurality of single cells 10 are connected to the negative electrode tab 6 by negative electrode welds 19 on the negative electrode tab 6. Although not shown, similarly, a plurality of positive electrode extension members 16 a extending from the plurality of single cells 10 are connected to the positive electrode tab 5 at the positive electrode welds 18 on the positive electrode tab 5. The secondary battery A further includes a reactant layer 20. The reactive substance layer 20 is formed on the surface of the positive electrode terminal portion 3 or the negative electrode terminal portion 4 in each unit cell 10. In the example of this figure, the reactant layer 20 is formed on the surface of a part of the negative electrode extension member 17a. The reactant layer 20 may be formed on a part of the surface of the positive electrode extension member 16a. However, the reactive material layer 20 does not need to be formed on both the negative electrode extending member 17a and the positive electrode extending member 16a, and may be formed on only one of them. The negative electrode extension member 17a and the negative electrode current collector 17 may be formed of the same material, or may be formed of different materials. The positive electrode extension member 16a and the positive electrode current collector 16 are the same. These materials may be used, or may be formed from different materials.

  FIG. 4 is a schematic perspective view showing the relationship between the reactant layer 20 and the negative electrode extension member 17a. As shown in FIG. 4A, the reactant layer 20 covers a part of the surface of the negative electrode extension member 17a. Specifically, the reactant layer 20 is formed on the surface of the negative electrode extension member 17a so as to cross from one end to the other end in the width direction of the negative electrode extension member 17a. As shown in FIG. 4B, when the negative electrode extension member 17a generates heat due to Joule heat accompanying overcurrent, the negative electrode extension member 17a and the reactant layer 20 react to generate a product substance layer 21. . At this time, since the reactive substance layer 20 is formed so as to cross the negative electrode extension member 17a from one end to the other end in the width direction, the product substance layer 21 also includes the negative electrode extension member 17a in the width direction. It is formed so as to cross from one end to the other end. Further, since the volume of the product material layer 21 is larger than the volume of the portion 30 (FIG. 4A) that contributes to the reaction in the negative electrode extension member 17a, the thickness of the product material layer 21 is the same as that of the original negative electrode extension member 17a. Thicker than the thickness. As a result, the product material layer 21 is formed so as to cross the negative electrode extension member 17a from one end to the other end in the thickness direction. And as shown in FIG.4 (c), the production | generation substance layer 21 becomes a low density and becomes a sparse structure | tissue, and intensity | strength becomes low. Therefore, the product material layer 21 itself breaks due to stress or the like generated in the negative electrode extension member 17a, or a breakage occurs between the product material layer 21 and the adjacent negative electrode extension member 17a. At this time, the product material layer 21 is formed so as to cross the negative electrode extension member 17a in the width direction and the thickness direction from one end to the other end. Is completely broken, so that the overcurrent is reliably interrupted. In addition, since it is the same as that of the above also when the reactive substance layer 20 is formed in the surface of the positive electrode extension member 16a, the description is abbreviate | omitted.

Next, the material of the battery element 1 will be described.
The materials constituting the positive electrode layer 11, the negative electrode layer 12, and the electrolyte layer 13 are not particularly limited as long as the battery element 1 described above can be formed. Below, the positive electrode layer 11, the negative electrode layer 12, and the electrolyte layer 13 of an all-solid-state lithium secondary battery are demonstrated as a typical example.

(Positive electrode layer and negative electrode layer)
The positive electrode layer 11 includes the positive electrode current collector 16 including the positive electrode extension member 16a and the positive electrode active material layer 14 as described above. As described above, the negative electrode layer 12 includes the negative electrode current collector 17 including the negative electrode extension member 17a and the negative electrode active material layer 15.

(Positive electrode active material layer)
The positive electrode active material layer 14 includes a positive electrode active material and a solid electrolyte.
The positive electrode active material is not particularly limited as long as it is an active material that can be used for a Li ion battery, and examples thereof include layered, olivine-based, and spinel type compounds. Specifically, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), lithium nickel manganese cobaltate (LiNi _1-yz Co _y Mn _z O ₂ , such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium nickel cobaltate (LiNi _1-x Co _x O ₂ ), nickel lithium manganate (LiNi _1-x Mn _x O ₂ ), lithium manganate (LiMn) ₂ O ₄ ), a lithium manganate compound (Li _{1 + x} M _y Mn _2−xy O ₄ ; M = Al, Mg, Fe, Cr, Co, Ni, Zn), lithium metal phosphate (LiMPO ₄ , M = Fe, Mn, Co, Ni), lithium metal fluorophosphate (Li ₂ MPO ₄ F, M = Fe, Mn, Co, Ni ), Lithium metal phosphate (Li ₂ MP ₂ O ₇ , M = Fe, Mn, Co, Ni), lithium titanate (Li _x TiO _y ), and the like.

  The positive electrode active material layer 14 includes the positive electrode active material described above and a solid electrolyte, preferably a sulfide solid electrolyte, and may further include other components such as a conductive additive and a binder. The solid electrolyte will be described later. Examples of the conductive assistant include VGCF (vapor grown carbon fiber), carbon black, carbon materials such as graphite, and metal materials. Examples of the binder include polytetrafluoroethylene, styrene butadiene rubber, and polyvinylidene fluoride.

(Positive electrode current collector)
Examples of the material of the positive electrode current collector 16 include aluminum, nickel, iron, and titanium. Examples of the shape of the positive electrode current collector 16 include a foil shape, a plate shape, and a mesh shape. When the positive electrode extension member 16 a is formed integrally with the positive electrode current collector 16, the positive electrode extension member 16 a is formed of the same material as the positive electrode current collector 16. When the positive electrode extension member 16a is formed separately and is joined to the positive electrode current collector 16 by welding or the like, the positive electrode extension member 16a is formed of the same or different material as the positive electrode current collector 16. Examples of the material include copper as well as the above materials. Moreover, foil shape etc. are illustrated as a shape of the positive electrode extension member 16a.

(Positive electrode tab)
As a material of the positive electrode tab 5, a material that can be used as a material of the positive electrode current collector 16 or the positive electrode extension member 16 a can be used. However, the material of the positive electrode tab 5 may be the same as or different from the material of the positive electrode current collector 16 or the positive electrode extension member 16a.

(Negative electrode active material)
The negative electrode active material layer 15 includes a negative electrode active material and a solid electrolyte.
The negative electrode active material is not particularly limited as long as it is an active material that can be used for a Li ion battery, and examples thereof include metals and carbon materials. Examples of the metal include metals such as Li, Sn, Si, Al, In, and Sb, alloys that combine some of these, and the like. As the carbon material, a carbon material including a graphite structure (layered structure) at least partially, specifically, natural or artificial graphite, soft carbon, hard carbon, low-temperature calcined carbon, or some of these The material which combined these is illustrated.

  The negative electrode active material layer 15 includes a negative electrode active material and a solid electrolyte, preferably a sulfide solid electrolyte, and may further include other components such as a conductive additive and a binder. About a solid electrolyte, a conductive support agent, and a binder, the material similar to the case of the above-mentioned positive electrode active material layer 14 can be used.

(Negative electrode current collector)
As a material for the negative electrode current collector 17, copper can be used in addition to the material for the positive electrode current collector 16 described above. As the shape of the negative electrode current collector 17, the same shape as that of the positive electrode current collector 16 can be adopted. When the negative electrode extension member 17 a is formed integrally with the negative electrode current collector 17, the negative electrode extension member 17 a is formed of the same material as the negative electrode current collector 17. When the negative electrode extension member 17a is formed as a separate body and joined to the negative electrode current collector 17 by welding or the like, the negative electrode extension member 17a is formed of the same material as or different from the negative electrode current collector 17. Moreover, foil shape etc. are illustrated as a shape of the negative electrode extension member 17a.

(Negative electrode tab)
As a material of the negative electrode tab 6, a material that can be used as a material of the negative electrode current collector 17 or the negative electrode extension member 17a can be used. However, the material of the negative electrode tab 6 may be the same as or different from the material of the negative electrode current collector 17 or the negative electrode extension member 17a.

(Solid electrolyte layer)
The solid electrolyte of the electrolyte layer 13 is not particularly limited, and examples thereof include inorganic solid electrolytes such as sulfides, oxides, nitrides, and halides. The solid electrolyte may be crystalline, amorphous or glass ceramic. Examples of inorganic solid electrolytes include Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Li ₂ S—P ₂ S ₅ , LiI—Li ₂ S—B ₂ S ₃ , Li ₃ PO ₄ —. _{Li 2 S-Si 2 S,} Li 3 PO 4 -Li 2 S-SiS 2, LiPO 4 -Li 2 S-SiS, LiI-Li 2 S-P 2 O 5, LiI-Li 3 PO 4 -P 2 S ₅ , solid sulfide-based amorphous electrolyte powders such as Li ₇ P ₃ S ₁₁ , Li ₃ PS ₄ , and Li ₂ S—P ₂ S ₅ are exemplified. Examples of the inorganic solid electrolyte include solids such as Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—SiO ₂ , Li ₂ O—B ₂ O ₃ , Li ₂ O—B ₂ O ₃ —ZnO. An oxide-based amorphous electrolyte powder is exemplified. The inorganic solid _{electrolyte, LiI, LiI-Al 2 O} 3, Li 3 N, Li 3 N-LiI-LiOH, Li 1.3 Al 0.3 Ti 0.7 (PO 4) 3, Li 1 + x + y A x Ti _2-x Si _y P _3-y O ₁₂ (A = Al or Ga, 0 ≦ x ≦ 0.4, 0 <y ≦ 0.6), [(B _1/2 Li _1/2 ) _1-z C _z ] TiO ₃ (B = La, Pr, Nd, Sm, C = Sr or Ba, 0 ≦ x ≦ 0.5), Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , LiPON Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li ₃ PO _{(4-3 / 2w)} N _w (w <1), Li _3.6 Si _0.6 P _0.4 O ₄ crystalline oxide powder, Examples thereof include halide powder, nitride powder, and oxynitride powder.

(Other components)
As another component, a separator (not shown) may be used for the all-solid lithium secondary battery. The separator is disposed between the positive electrode current collector 16 and the negative electrode current collector 17 described above. Examples of the material for the separator include polyethylene and polypropylene. The separator may have a single layer structure or a multilayer structure.

  Battery element 1 according to the present embodiment is not necessarily limited to the above-described all solid lithium secondary battery. Any battery element including at least a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer is included in battery element 1 according to the present embodiment.

  In the secondary battery A of the present embodiment, when an overcurrent is generated, the positive electrode terminal portion 3 or the negative electrode terminal portion 6 is heated by Joule heat due to the overcurrent, whereby a portion of the positive electrode terminal portion 3 or the negative electrode terminal portion 6 is The reaction material layer 20 formed on the surface reacts to generate a product material layer 21. At that time, since the product material layer 21 has a sparse structure due to volume expansion, the fracture occurs in the product material layer 21 or at the boundary between the product material layer 21 and an adjacent member. Thereby, the electric current which flows through the positive electrode terminal part 3 or the negative electrode terminal part 6 can be interrupted | blocked. Thus, the secondary battery A can realize a shutdown mechanism in which the positive electrode terminal portion 3 or the negative electrode terminal portion 6 is cut to stop the current when an overcurrent is generated. At this time, the reactive material layer 20 is only attached on the positive electrode terminal portion 3 or the negative electrode terminal portion 6, and it is not necessary to reduce the cross-sectional area of the positive electrode terminal portion 3 or the negative electrode terminal portion 6. Despite being provided, an increase in the internal resistance of the secondary battery A during normal operation can be avoided. Furthermore, since the reactive substance layer 20 is a thin and light substance, the energy density of the secondary battery A can be prevented from being lowered despite the provision of a shutdown mechanism.

(Second Embodiment)
The secondary battery A according to the present embodiment is different from the secondary battery A according to the first embodiment in the position where the reactant layer 20 is formed. Hereinafter, mainly the differences will be mainly described.

  FIG. 5 is a schematic partial top view illustrating a configuration example of the secondary battery A. In this figure, a part of the secondary battery A is enlarged, and the vicinity of the negative electrode tab 6 and the negative electrode extension member 17a is viewed from above. A plurality of negative electrode extension members 17 a extending from the plurality of single cells 10 are connected to the negative electrode tab 6 by negative electrode welds 19 on the negative electrode tab 6. Although not shown, similarly, a plurality of positive electrode extension members 16 a extending from the plurality of single cells 10 are connected to the positive electrode tab 5 at the positive electrode welds 18 on the positive electrode tab 5. The secondary battery A further includes a reactant layer 20. The reactive substance layer 20 is formed on the surface of all or part of the positive electrode terminal portion or the negative electrode terminal portion in each single cell 10. In the example of this figure, the reactant layer 20 is formed on the surface of the negative electrode tab 6 and around the negative electrode welded portion 19. The reactive material layer 20 may be formed on the surface of the positive electrode tab 5 and around the positive electrode welded portion 18. However, the reactive material layer 20 does not need to be formed on both the negative electrode tab 6 and the positive electrode tab 5, and may be formed on only one of them.

  FIG. 6 is a schematic side view showing the relationship between the reactant layer 20 and the negative electrode weld 19. As shown in FIG. 6A, the reactant layer 20 covers a part of the surface of the negative electrode tab 6. Specifically, the reactant layer 20 is formed on the surface of the negative electrode tab 6 and around the negative electrode welded portion 19. That is, the reactant layer 20 is formed on the surface of the negative electrode tab 6 so as to partially surround the negative electrode welded portion 19. Preferably, it is formed so as to completely surround the negative electrode welded portion 19. As shown in FIG. 6B, when the negative electrode tab 6 generates heat due to Joule heat accompanying overcurrent, the negative electrode tab 6 and the reactive material layer 20 react to generate a product material layer 21. At this time, since the reactive material layer 20 is formed so as to partially or completely surround the negative electrode welded portion 19, the product material layer 21 is formed so as to enter the lower side of the negative electrode welded portion 19. Further, since the volume of the product material layer 21 is larger than the volume of the portion 30 (FIG. 6A) that contributes to the reaction in the negative electrode tab 6, the thickness of the product material layer 21 depends on the reaction of the original negative electrode tab 6. It becomes thicker than the thickness of the contributed portion 30. The product material layer 21 has a low density and a sparse structure, and has a low strength. Therefore, the product material layer 21 itself breaks due to the stress generated in the negative electrode tab 6 and the negative electrode welded portion 19 or the product material layer 21 and the negative electrode welded portion 19 break. At this time, since the product material layer 21 is formed so as to enter the lower side of the negative electrode welded portion 19, the negative electrode welded portion 19 is completely peeled off from the negative electrode tab 6 due to the breakage of the product material layer 21. The current is reliably cut off. In addition, since it is the same as that of the above also when the reactive substance layer 20 is formed in the surface of a part of positive electrode tab 5 (peripheral part of the positive electrode welding part 18), the description is abbreviate | omitted.

  Also in this embodiment, the same effects as those of the first embodiment can be obtained. In addition, when the secondary battery A has a structure in which a plurality of single cells 10 are laminated, a plurality of reactant layers 20 are formed on the surface of the positive electrode welded portion 18 or a part of the positive electrode tab 5 or its peripheral portion, thereby The connection between the positive electrode extension member 16a and the positive electrode tab 5 can be cut at once. Similarly, by forming the reactive substance layer 20 on the surface of a part of the negative electrode welded part 19 or the negative electrode tab 6 or its peripheral part, the connection between the plurality of negative electrode extension members 17a and the negative electrode tab 6 can be cut at once. Can do. As a result, the positive electrode extension member 16a and the negative electrode extension member 17a that are not cut remain, and the phenomenon that current is concentrated on the positive electrode extension member 16a and the negative electrode extension member 17a and heat generation further increases can be reliably prevented.

Examples of the present invention will be described below. The following examples are for illustrative purposes only and are not intended to limit the invention.
In the example, a secondary battery was produced, and the behavior of the secondary battery when an overcurrent was supplied was evaluated. However, supply of current to the secondary battery and measurement of voltage were performed with the following devices.
Current supply and voltage measurement device: TOSCAT-3200 manufactured by Toyo System

(Example 1)
(1) Production of Secondary Battery (1-1) Synthesis of Solid Electrolyte Li ₂ S and P ₂ S ₅ are weighed and mixed for 5 minutes in an agate mortar, and then heptane is put in, and 40 using a planetary ball mill. A sulfide solid electrolyte was obtained by mechanical milling for a period of time.
(1-2) Preparation of positive electrode layer LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material, VGCF as a conductive additive, and the above sulfide solid electrolyte material were weighed and used as a binder. A slurry was obtained by mixing with PVDF and heptane as a solvent. And the obtained slurry was apply | coated on the aluminum foil as a positive electrode electrical power collector, and the positive electrode layer was obtained. An aluminum foil positive electrode extension member extends from the positive electrode current collector.
(1-3) Production of Negative Electrode Layer Graphite as a negative electrode active material as a negative electrode active material and the above sulfide solid electrolyte material were weighed and mixed with PVDF as a binder and heptane as a solvent to obtain a slurry. And the obtained slurry was apply | coated on the copper foil as a negative electrode collector, and the negative electrode layer was obtained. A negative electrode extending member of copper foil extends from the negative electrode current collector.
(1-4) Production of electrode body The positive electrode layer, the separator, and the negative electrode layer were pressed at 4 ton / cm ² to form an electrode body. The electrode body has a positive electrode layer disposed on one side of the separator, a negative electrode layer disposed on the other side, a positive electrode extension member of the positive electrode current collector extends from the positive electrode layer, and a negative electrode current collector extends from the negative electrode layer. The body's negative electrode extension member extends.
(1-5) Production of Reactive Material Layer Sulfur as a material of the reactive material layer was weighed and mixed with PVDF as a binder to obtain a slurry of the reactive material layer. Then, as shown in FIGS. 3 and 4, slurry was applied to the negative electrode extension member of the negative electrode current collector to form a reactant layer.
(1-6) Production of Solid Electrolyte Layer The above-mentioned sulfide solid electrolyte material was weighed and mixed with PVDF as a binder and heptane as a solvent to obtain a slurry. The obtained slurry was impregnated into a polypropylene mesh material as a reinforcing material and dried to obtain a solid electrolyte layer.
(1-7) Production of Battery Element A plurality of the above-mentioned electrode bodies and the above-mentioned solid electrolyte layers (the uppermost part is an electrode body) were laminated and pressed at 4 ton / cm ² to obtain a battery element.
(1-8) Preparation of Tabs The positive electrode extension members and the positive electrode tabs of the plurality of positive electrode current collectors of the above laminate were welded with ultrasonic waves. Similarly, the negative electrode extension members and negative electrode tabs of the plurality of negative electrode current collectors of the laminate were welded with ultrasonic waves.
(1-9) Laminate The battery element including the electrode tab and the reactant layer was covered with a laminate film and sealed to obtain a secondary battery.
(2) Evaluation of overcurrent About the obtained secondary battery, the overcurrent exceeding a regulation current was supplied and it was investigated whether overcurrent interrupted.
(3) Evaluation results Although there were a plurality of negative electrode extension members of the negative electrode current collector, all the negative electrode extension members were cut almost simultaneously, and the overcurrent was cut off. This is because the plurality of negative electrode extension members are all made of metal, which is also a material having high thermal conductivity, so there is very little temperature variation among the plurality of negative electrode extension members, and all the reactant layers are almost simultaneously This is thought to be due to the change to the product material layer. However, in more detail, it was found that, in a very short time interval, the individual negative electrode extension members were cut separately, and finally, all the negative electrode extension members were cut and the overcurrent was cut off. . In the process, it was found that there is a concern that the flowing current concentrates and heat generation increases at a portion where the extension portion is not cut, although it is an extremely short time.

(Example 2)
(1) Production of Secondary Battery A secondary battery was produced in the same manner as in Example 1 except that the production method of the reactant layer was different.
The method for producing the reactant layer is as follows. The reactant layer slurry was applied to the periphery of the negative electrode welded portion where the negative electrode extension members of the plurality of negative electrode current collectors and the negative electrode tab were welded on the surface of the negative electrode tab.
(2) Evaluation of overcurrent Overcurrent was evaluated in the same manner as in Example 1 above.
(3) Evaluation results The negative electrode welded portion of the negative electrode extension member of the negative electrode current collector was peeled off from the negative electrode tab, so that the overcurrent was interrupted. Since the reactive material layer is formed between the negative electrode weld and the negative electrode tab (the surface of the negative electrode tab in the periphery of the negative electrode weld), it is generated when the reactive material layer changes into a product material layer and expands in volume. This is probably because the material layer wraps around the negative electrode weld. In this case, since the plurality of negative electrode extension members are peeled together from the negative electrode tab and there is no negative electrode extension member that remains connected to the negative electrode tab, it is possible to prevent the flowing current from concentrating and increasing heat generation. That is, the overcurrent can be more safely interrupted than in the first embodiment.

DESCRIPTION OF SYMBOLS 1 Battery element 2 Laminate film 3 Positive electrode terminal part 4 Negative electrode terminal part 5 Positive electrode tab 6 Negative electrode tab 11 Positive electrode layer 12 Negative electrode layer 13 Solid electrolyte layer 14 Positive electrode active material layer 15 Negative electrode active material layer 16 Positive electrode collector 16a Extension part 17 Negative electrode Current collector 17a Extension part 18 Welding part 19 Welding part 20 Reactive substance layer 21 Generating substance layer 30 Part which contributed to reaction A Secondary battery

Claims (1)

A chargeable / dischargeable battery element;
A positive terminal portion connected to the battery element;
A negative electrode terminal connected to the battery element;
A reactant layer formed on a surface of the positive electrode terminal portion or the negative electrode terminal portion;
With
The sulfur contained in the reactant layer reacts with the copper contained in the positive electrode terminal portion or the negative electrode terminal portion due to a temperature rise, and the volume increases compared to the portion contributing to the reaction in the positive electrode terminal portion or the negative electrode terminal portion. A secondary battery that produces a product layer containing copper sulfide.

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