JP6414700B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

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

  Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries (lithium secondary batteries) are lighter and have higher energy density than existing batteries. It is used as a power source. In particular, lithium-ion secondary batteries that are lightweight and provide high energy density will become increasingly popular as high-output power sources for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). It is expected to do.

  As one form of the nonaqueous electrolyte secondary battery, a form in which a flat electrode body is accommodated in a flat battery case can be mentioned. The electrode body can expand and contract with charge / discharge. The expansion and contraction associated with charging / discharging of the electrode body may cause a decrease in battery performance. Therefore, when a compression member is disposed between the battery case and the electrode body, or when a plurality of nonaqueous electrolyte secondary batteries are assembled into an assembled battery, the electrode is applied by applying a restraining pressure to the battery case by the restraining member. By applying a load to the body, the expansion and contraction of the electrode body is suppressed to prevent a decrease in battery performance (see, for example, Patent Document 1).

  In addition, a non-aqueous electrolyte secondary battery is usually provided with a safety valve that is set to release the internal pressure when the internal pressure of the battery case rises above a predetermined level. When the temperature of the nonaqueous electrolyte secondary battery increases due to an internal short circuit or the like, the internal pressure of the battery case increases due to the electrolyte, electrode decomposition gas, electrolyte vaporized gas, or the like. The safety valve is designed to open at a pressure lower than the burst pressure of the battery case, and when the internal pressure of the battery case suddenly increases due to an internal short circuit, etc., the gas is exhausted from the safety valve, causing the battery Case rupture is suppressed.

JP 2014-110190 A

  When a non-aqueous electrolyte secondary battery causes an internal short circuit, etc., and the amount of gas generated is large, even after the safety valve is opened, the gas is not completely exhausted from the safety valve and the internal pressure of the battery case May rise and the battery case may expand. Here, in order to be able to withstand the increase in internal pressure of the battery case, it is necessary to increase the size of the battery case, improve the durability, and the like, causing problems in terms of cost and space. For this reason, when an internal short circuit occurs, it is desired that the generated gas is more reliably exhausted from the safety valve.

  Therefore, an object of the present invention is to provide a non-aqueous electrolyte secondary battery that can more reliably exhaust the generated gas from the safety valve when an internal short circuit occurs.

The nonaqueous electrolyte secondary battery disclosed herein includes an electrode body having a flat shape, a case having the flat shape and containing the electrode body, and a U-shaped restraining plate. The case includes a safety valve outside the flat surface of the case. The constraining plate is arranged on at least one flat surface of the case so that the U-shaped opening portion faces a direction of the safety valve so that smoke can be discharged from the safety valve when an internal short circuit of the nonaqueous electrolyte secondary battery is performed. Then, a load is applied to an end portion of the flat surface of the electrode body other than the end portion closest to the safety valve.
According to such a configuration, the smoke exhaust path when the gas generated from the electrode body is exhausted from the inside of the non-aqueous electrolyte secondary battery through the safety valve is shorter than that in the prior art. As a result, the nonaqueous electrolyte secondary battery can more reliably exhaust the generated gas from the safety valve than the conventional technology.

It is a perspective view which shows typically the external shape of the lithium ion secondary battery which concerns on one Embodiment of this invention. It is a longitudinal cross-sectional view which shows typically the cross-sectional structure which follows the II-II line | wire in FIG. It is a schematic diagram which shows the structure of the wound electrode body used for the lithium ion secondary battery which concerns on one Embodiment of this invention. 1 is a perspective view schematically showing the inside of a lithium ion secondary battery according to an embodiment of the present invention. (A) is a perspective view which shows typically the structure of the conventional lithium ion secondary battery, (b) is the perspective view which shows typically the structure of the lithium ion secondary battery which concerns on one Embodiment of this invention. FIG. (A) No. 1 is a perspective view schematically showing a battery for evaluation according to No. 1; 2 is a perspective view schematically showing a battery for evaluation according to No. 2; 3 is a perspective view schematically showing a battery for evaluation according to No. 3; 4 is a perspective view schematically showing a battery for evaluation according to No. 4; 6 is a perspective view schematically showing a battery for evaluation according to FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. Note that matters other than the matters specifically mentioned in this specification and necessary for the implementation of the present invention (for example, a general configuration and manufacturing process of a nonaqueous electrolyte secondary battery that does not characterize the present invention) Can be understood as a design matter of those skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a so-called storage battery such as a lithium ion secondary battery and a power storage element such as an electric double layer capacitor.
Hereinafter, the present invention will be described in detail by taking a flat rectangular lithium ion secondary battery having a flat electrode body and a flat battery case as an example. However, the present invention is described in this embodiment. It is not intended to be limited to.

  A lithium ion secondary battery 100 shown in FIGS. 1 and 2 includes a battery case (that is, an exterior container) 30 in which a flat wound electrode body 20 and a nonaqueous electrolyte (not shown) are flat (flat rectangular). This is a sealed lithium ion secondary battery 100 constructed by being housed in a battery. The battery case 30 has a pair of flat surfaces (wide surfaces) 32. The battery case 30 is provided with a positive terminal 42 and a negative terminal 44 for external connection. Further, in the vicinity of the central portion of the upper surface of the battery case 30 outside the flat surface 32 of the battery case 30, a thin wall set so as to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. The safety valve 36 is provided. In addition, the battery case 30 is provided with an inlet (not shown) for injecting a nonaqueous electrolyte. The positive terminal 42 is electrically connected to the positive current collector 42a. The negative electrode terminal 44 is electrically connected to the negative electrode current collector plate 44a. As the material of the battery case 30, for example, a light metal material having good thermal conductivity such as aluminum is used.

  As shown in FIGS. 2 and 3, the wound electrode body 20 has a positive electrode active material layer 54 formed along the longitudinal direction on one side or both sides (here, both sides) of an elongated positive electrode current collector 52. The positive electrode sheet 50 and the negative electrode sheet 60 in which the negative electrode active material layer 64 is formed along the longitudinal direction on one side or both sides (here, both sides) of the long negative electrode current collector 62 are two long shapes. The separator sheet 70 is overlapped and wound in the longitudinal direction. The wound electrode body has a pair of flat surfaces 22. The positive electrode active material layer non-forming portion 52a (that is, the positive electrode active material) formed so as to protrude outward from both ends in the winding axis direction of the wound electrode body 20 (referred to as the sheet width direction orthogonal to the longitudinal direction). A portion where the positive electrode current collector 52 is exposed without forming the layer 54) and a negative electrode active material layer non-forming portion 62a (that is, a portion where the negative electrode active material layer 64 is not formed and the negative electrode current collector 62 is exposed). Are respectively joined to the positive electrode current collector plate 42a and the negative electrode current collector plate 44a.

  As the positive electrode sheet 50 and the negative electrode sheet 60, the same ones used in conventional lithium ion secondary batteries can be used without particular limitation. One typical embodiment is shown below.

Examples of the positive electrode current collector 52 constituting the positive electrode sheet 50 include aluminum foil. Examples of the positive electrode active material included in the positive electrode active material layer 54 include lithium transition metal oxides (eg, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O). ₄ , LiNi _0.5 Mn _1.5 O ₄ etc.), lithium transition metal phosphate compounds (eg, LiFePO ₄ etc.) and the like. The positive electrode active material layer 54 can include components other than the active material, such as a conductive material and a binder. As the conductive material, for example, carbon black such as acetylene black (AB) and other (eg, graphite) carbon materials can be suitably used. As the binder, for example, polyvinylidene fluoride (PVDF) can be used.

  Examples of the negative electrode current collector 62 constituting the negative electrode sheet 60 include copper foil. As the negative electrode active material contained in the negative electrode active material layer 64, for example, a carbon material such as graphite, hard carbon, or soft carbon can be used. The negative electrode active material layer 64 can include components other than the active material, such as a binder and a thickener. As the binder, for example, styrene butadiene rubber (SBR) can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

  Examples of the separator 70 include a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat resistant layer (HRL) may be provided on the surface of the separator 70.

The non-aqueous electrolyte can be the same as that of a conventional lithium ion secondary battery, and typically, an organic solvent (non-aqueous solvent) containing a supporting salt can be used. As the non-aqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, lactones and the like used in electrolytes of general lithium ion secondary batteries are used without particular limitation. Can do. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), Examples thereof include monofluoromethyl difluoromethyl carbonate (F-DMC) and trifluorodimethyl carbonate (TFDMC). Such a non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types as appropriate. As the supporting salt, for example, a lithium salt such as LiPF ₆ , LiBF ₄ , LiClO ₄ (preferably LiPF ₆ ) can be suitably used. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less.

  In addition, the non-aqueous electrolyte is, for example, a gas generating agent such as biphenyl (BP) or cyclohexylbenzene (CHB); an oxalato complex compound containing a boron atom and / or a phosphorus atom, as long as the effects of the present invention are not significantly impaired. Various additives such as a film forming agent such as vinylene carbonate (VC); a dispersant; a thickener may be included.

  The lithium ion secondary battery 100 includes a U-shaped restraining plate 80 as shown in FIG. In the present embodiment, the restraining plate 80 is provided on the inner wall side of the flat surface 32 of the battery case 30. The restraint plate 80 is configured and arranged so that the lithium ion secondary battery 100 can exhaust smoke from the safety valve 36 when an internal short circuit occurs. Specifically, the restraint plate 80 is arranged so that the U-shaped opening faces the direction of the safety valve 36. The restraint plate 80 is sandwiched between the flat surface 32 of the battery case 30 and the flat surface 22 of the electrode body 20, so that the end portions of the flat surface 22 of the electrode body 20 other than the end portion closest to the safety valve 36. A load is applied to In order to apply a load appropriately, a load may be further applied by providing the lithium ion secondary battery with a restraining member, a restraining band, or the like. The application of a load by a restraining member, a restraining band or the like can be effectively performed particularly when a battery pack is configured by combining a plurality of lithium ion secondary batteries, but it is also performed on a single lithium ion secondary battery. be able to. A load is also applied to a part of the end portion of the flat surface 22 of the electrode body 20 closest to the safety valve 36 by the upper end portion of the U-shaped restraining plate 80.

  In this specification, “non-aqueous electrolyte secondary battery (lithium ion secondary battery) can be discharged from a safety valve when an internal short circuit occurs” means, for example, a non-aqueous electrolyte secondary battery (lithium ion secondary battery) When a steel nail with a diameter of 3 mm was penetrated at a speed of 10 mm / sec in a central part of the flat surface of the plate at a speed of 10 mm / sec, and the internal short circuit occurred, the battery case did not expand and was generated from the safety valve It means that gas can be released.

  FIG. 5A is a diagram schematically showing a configuration of a conventional lithium ion secondary battery 200. In FIG. 5A, the hatched area indicates the restrained portion 184 where a load is applied on the electrode body 120. As described above, in the conventional lithium ion secondary battery 200, a load is applied to almost the entire flat surface 122 of the electrode body 120. Therefore, the smoke exhaust path when the gas generated from the electrode body 120 is exhausted from the inside of the lithium ion secondary battery 200 through the safety valve 136 is as shown by a broken line arrow in FIG. That is, typically, the generated gas is exhausted from the end of the electrode body 120 in the width direction (the left-right direction in the drawing) to the safety valve 136 above the electrode body 120.

  On the other hand, in this embodiment, by using the U-shaped restraint plate 80, a restraint portion 84 where a load is applied to the electrode body 20 in a region indicated by hatching in FIG. It becomes. As described above, in the lithium ion secondary battery 100 according to the present embodiment, a load is applied to the end other than the end closest to the safety valve 36 of the flat surface 22 of the electrode body 20, and the constraint to which the load is applied is applied. The shape of the part 84 is U-shaped. The U-shaped opening faces the direction of the safety valve 36. Therefore, the smoke exhaust path when the gas generated from the electrode body 20 is exhausted from the inside of the lithium ion secondary battery 100 through the safety valve 36 is as indicated by a broken line arrow in FIG. That is, when a load is applied to the end of the electrode body 20 in the width direction (left-right direction in the drawing) and the end close to the bottom surface (lower surface in the drawing) of the lithium ion secondary battery 100, the generated gas is The smoke is exhausted from above the electrode body 20 to the safety valve 36.

  Therefore, as is clear from the comparison between the broken line arrow in FIG. 5A and the broken line arrow in FIG. 5B, in this embodiment, the flue gas path is shorter than in the prior art. For this reason, in this embodiment, the generated gas can be more reliably exhausted from the safety valve than in the prior art.

  When the constraining plate 80 is arranged so that the U-shaped opening is on the top as shown in FIG. 4, the width of the U-shaped vertical bar is equal to the width of the electrode body 20 (the length in the horizontal direction in the figure). It is preferable that it is 1/4 or less of the length along the width direction of the vertical bar portion. Moreover, it is preferable that the width of the U-shaped horizontal bar portion is ¼ or less of the height of the electrode body 20 (length in the vertical direction in the figure; length along the width direction of the horizontal bar portion). The width of the U-shaped vertical bar portion of the constraining plate 80 is larger than ¼ of the width of the electrode body 20 or the width of the U-shaped horizontal bar portion of the constraining plate 80 is equal to the height of the electrode body 20. If it is larger than 1/4, the range in which the load is applied to the electrode body 20 becomes too wide, and a smoke exhaust path other than the broken line arrow in FIG. 36 may not be able to exhaust smoke completely.

  The restraint plate 80 applies a load to the end of the flat surface 22 of the electrode body 20 other than the end closest to the safety valve 36, and the magnitude of this load is 10 kgf (98.0665N) or more. Is preferred. If this load is less than 10 kgf, a smoke exhaust path other than the dashed arrow in FIG. 5B is generated, and there is a possibility that the gas generated by the internal short circuit cannot be completely exhausted from the safety valve 36.

  The shape of the restraint plate 80 may be U-shaped, and is not limited to a U-shape in which a square vertical bar and a square horizontal bar are connected as shown in FIG. For example, the connecting portion between the lower end of the U-shaped vertical bar portion and both ends of the U-shaped horizontal bar portion may have a curved shape.

  The position of the restraint plate 80 is the outermost end of the U-shaped vertical bar portion and the outer end of the horizontal bar portion, except for the end closest to the safety valve 36 of the flat surface 22 of the electrode body 20. Does not necessarily match. Ends other than the end closest to the safety valve 36 on the flat surface 22 of the electrode body 20 are located at the outer ends of the U-shaped vertical bar and the outer bar within the range in which the effect of the present invention is obtained. It may be slightly outside or slightly inside than the extreme end. For example, the position of the outer end of the U-shaped vertical bar is on the inside or outside of the outermost end of the width direction of the electrode body 20 by about 1/10 of the length in the width direction of the electrode body 20. May be. Similarly, for example, the position of the outer end of the U-shaped horizontal bar is higher in the height direction of the electrode body 20 than the outermost end of the electrode body 20 near the bottom surface of the lithium ion secondary battery 100. It may be on the inside or outside about 1/10 of the length.

  The restraint plate 80 may be provided only on one flat surface 22 of the battery case 30 or may be provided on both of the two flat surfaces 22. Even when the restraint plate 80 is provided only on one flat surface 22 of the battery case 30, the effect of the present invention can be obtained.

  The lithium ion secondary battery 100 configured as described above can be used for various applications. Suitable applications include driving power sources mounted on vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). The lithium ion secondary battery 100 can also be used in the form of a battery pack typically formed by connecting a plurality of lithium ion secondary batteries 100 in series and / or in parallel.

  Next, a modified example of the lithium ion secondary battery 100 according to this embodiment will be described. In the example of the embodiment described above, the restraint plate is installed on the inner wall side of the flat surface of the battery case. However, in this modification, the restraint plate is installed on the outer wall side of the flat surface of the battery case. Even if the restraint plate is installed on the outer wall side of the flat surface of the battery case, a region as shown by hatching in FIG. 5B, that is, a U-shaped restraint portion can be formed, and a broken line arrow in FIG. It is possible to form a smoke exhaust path as shown in FIG. Therefore, also in this modification, compared with the prior art, the generated gas can be more reliably discharged from the safety valve.

  About the point except installing a restraint board in the outer wall side of the flat surface of a battery case, it can be the same as that of the example of embodiment mentioned above. However, in this modification, a restraint plate is arranged on the outer wall side of the flat surface of the battery case of the lithium ion secondary battery, and a load is applied using a restraint band or the like. Or a restraint board is arrange | positioned at the outer wall side of two flat surfaces of the battery case of a lithium ion secondary battery, respectively, and a load is applied by binding restraint boards. In addition, in the case of using a lithium ion secondary battery as the form of the assembled battery, instead of the cooling plate or the spacer disposed between the single cells or the spacer, or in addition to the cooling plate or the spacer, the restraint plate Place. Since the assembled battery is constrained by a restraining band, a restraining member, or the like, a U-shaped load can be applied to the electrode body inside the unit cell by a constraining plate disposed between the unit cell. .

  In the above, the flat rectangular lithium ion secondary battery 100 having the flat electrode body 20 and the flat battery case 30 has been described as an example. It can also be configured as a laminated lithium ion secondary battery having a flat shape.

  For example, a laminate-type lithium ion secondary battery includes an electrode body having a flat shape and a laminate case that accommodates the electrode body and has a flat shape. The laminate case includes a safety valve outside its flat surface. The safety valve is disposed near the center of one side of the flat surface of the laminate case. The U-shaped restraint plate is disposed on at least one flat surface of the laminate case so that the U-shaped opening portion faces a certain direction of the safety valve so that smoke can be discharged from the safety valve when the battery is short-circuited inside. Yes. The restraint plate may be disposed on either the inside or the outside of the laminate case. The restraint plate applies a load to an end portion of the flat surface of the electrode body other than the end portion closest to the safety valve.

  In the above description, the wound electrode body is described as an example of the flat electrode body. However, the flat electrode body may be a stacked electrode body. Moreover, the technique disclosed here is applicable also to nonaqueous electrolyte secondary batteries other than a lithium ion secondary battery.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Production of test battery>
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ (LNCM) as a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder of these materials A positive electrode active material slurry was prepared by charging into a kneader so that the mass ratio was LNCM: AB: PVDF = 90: 8: 2 and kneading while adjusting the viscosity with N-methyl-2-pyrrolidone (NMP). . The slurry was applied to both surfaces of an aluminum foil (positive electrode current collector), dried and pressed to prepare a positive electrode sheet having a positive electrode active material layer on both surfaces of the positive electrode current collector.

  Natural graphite (C) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a dispersant, the mass ratio of these materials is C: SBR: CMC = 98: 1 : 1 was added to a kneader and kneaded while adjusting the viscosity with ion-exchanged water to prepare a negative electrode active material slurry. This slurry was applied to both sides of a thick copper foil (negative electrode current collector), dried and pressed to prepare a negative electrode sheet having a negative electrode active material layer on both sides of the negative electrode current collector.

  The positive electrode sheet and the negative electrode sheet prepared above were laminated together with two separator sheets (here, a porous sheet in which polypropylene (PP) was laminated on both sides of polyethylene (PE)), wound, A flat wound electrode body was produced by pressing and rubbing from the direction. Next, the positive electrode terminal and the negative electrode terminal were connected to the wound electrode body and accommodated in a flat rectangular battery case having a safety valve and an electrolyte inlet. At this time, one constraining plate was inserted between the flat inner wall of the battery case and the wound electrode body.

After depressurizing the inside of the battery case, a non-aqueous electrolyte solution was injected from the electrolyte solution inlet, and the wound electrode body was impregnated with the non-aqueous electrolyte solution. As a non-aqueous electrolyte, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of EC: DMC: EMC = 30: 40: 30 is used as a supporting salt. In which LiPF ₆ was dissolved at a concentration of 1.0 mol / L was used. Subsequently, the electrolyte injection port was sealed to obtain a lithium ion secondary battery. A restraining member was applied to the flat surface of the battery case using a restraining member for this lithium ion secondary battery so that a load of 10 kgf was applied to the electrode body via the restraining plate, and this was used as a test battery.

  In addition, as a test battery, five types (No. 1 to No. 5) having different shapes or arrangements of restraint plates were produced. The restraint plate of each test battery is described below. Further, in FIGS. 1-No. 5 schematically shows a battery for evaluation. A solid line in FIG. 6 is an evaluation battery (outer shape thereof), and an ellipse at the center of the upper surface represents a safety valve. A rectangular parallelepiped indicated by a broken line in the evaluation battery is an electrode body, and a diagonal line on the flat surface of the electrode body represents a region where a load is applied. The cylinder at the center of the flat surface of the evaluation battery represents a nail used in the following nail penetration test. Moreover, a broken line arrow represents the assumed smoke exhaust path.

(Test battery No. 1)
U-shaped restraint plate is used. The U-shaped opening is placed on the flat surface of the battery case so that it faces the direction of the safety valve, and a load is applied to the end of the flat surface of the electrode body other than the end closest to the safety valve. The width of the U-shaped vertical bar is 1/4 of the width of the electrode body. The width of the U-shaped horizontal bar is 1/4 of the height of the electrode body.
(Test battery No. 2)
A rectangular restraint plate with dimensions slightly smaller than the flat surface of the electrode body is used. A load is applied to almost the entire flat surface of the electrode body.
(Test battery No. 3)
Two rectangular restraint plates are used. Place the constraining plate so that one of the long sides of each constraining plate is along the respective end of the electrode body in the width direction, and apply a load to both ends of the electrode body in the width direction.
(Test battery No. 4)
U-shaped restraint plate is used. The U-shaped opening is placed on the flat surface of the battery case so that it faces the bottom surface of the battery, and a load is applied to the flat surface of the electrode body at the end closest to the safety valve and both ends in the width direction. The width of the U-shaped vertical bar is 1/4 of the width of the electrode body. The width of the U-shaped horizontal bar is 1/4 of the height of the electrode body.
(Test battery No. 5)
U-shaped restraint plate is used. The U-shaped opening is placed on the flat surface of the battery case so that it faces the direction of the safety valve, and a load is applied to the end of the flat surface of the electrode body other than the end closest to the safety valve. The width of the U-shaped vertical bar is 1/3 of the width of the electrode body. The width of the U-shaped horizontal bar is 1/3 of the height of the electrode body.

[Nail penetration test]
Each evaluation battery is charged to SOC 100%, and an iron nail having a diameter of 3 mm is passed through the central portion of the flat surface of each evaluation battery at a speed of 10 mm / sec in a temperature environment of 25 ° C., thereby internally short-circuiting. It was. And it evaluated whether a battery case expand | swells by the internal pressure rise by an internal short circuit. The results are shown in Table 1.

As shown in Table 1, no. In the evaluation battery according to No. 1, all the gas generated by the internal short circuit could be exhausted from the safety valve. This is no. In the evaluation battery according to No. 1, it is considered that the smoke exhaust path is a short distance from the upper part of the electrode body to the safety valve.
On the other hand, no. In the evaluation battery according to No. 2, after the safety valve was opened, the generated gas could not be sufficiently exhausted from the safety valve, the internal pressure increased, and the battery case was expanded. This is no. In the evaluation battery according to 2, it is considered that the smoke exhaust path is a long distance from the end in the width direction of the electrode body to the safety valve.
No. Even in the evaluation battery according to No. 3, after the safety valve was opened, the generated gas could not be sufficiently exhausted from the safety valve, the internal pressure increased, and the battery case was expanded. This is no. In the evaluation battery according to No. 3, there is considered to be a long-distance smoke exhaust path from the lower part of the electrode body to the safety valve in addition to the smoke exhaust path from the upper part of the electrode body to the safety valve.
No. Even in the evaluation battery according to No. 4, after the safety valve was opened, the generated gas could not be sufficiently exhausted from the safety valve, the internal pressure increased, and the battery case was expanded. This is no. In the evaluation battery according to No. 4, the smoke exhaust path is considered to be a long distance from the lower part of the electrode body to the safety valve.
No. Even in the evaluation battery according to No. 5, after the safety valve was opened, the generated gas could not be sufficiently exhausted from the safety valve, the internal pressure increased, and the battery case was expanded. This is because gas is generated from the periphery of the electrode body by applying a load from the restraining plate to the electrode body in a wide range, and in addition to the short-distance smoke exhaust path from the upper part of the electrode body to the safety valve, This is probably because there was a smoke exhaust path from the lower part to the safety valve or from the end in the width direction of the electrode body to the safety valve.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

20 wound electrode body 22 flat surface 30 battery case 32 flat surface 36 safety valve 42 positive electrode terminal 42a positive electrode current collector plate 44 negative electrode terminal 44a negative electrode current collector plate 50 positive electrode sheet (positive electrode)
52 Positive Electrode Current Collector 52a Positive Electrode Active Material Layer Non-Forming Portion 54 Positive Electrode Active Material Layer 60 Negative Electrode Sheet (Negative Electrode)
62 Negative electrode current collector 62a Negative electrode active material layer non-formed portion 64 Negative electrode active material layer 70 Separator sheet (separator)
80 Restraint plate 84 Restraint part 100 Lithium ion secondary battery

Claims (1)

An electrode body having a flat shape;
A case having the electrode body and having a flat shape;
A non-aqueous electrolyte secondary battery comprising a U-shaped restraint plate,
The case includes a safety valve outside the flat surface of the case,
The constraining plate is arranged on at least one flat surface of the case so that the U-shaped opening portion faces a direction of the safety valve so that smoke can be discharged from the safety valve when an internal short circuit of the nonaqueous electrolyte secondary battery is performed. The load is applied to the end of the flat surface of the electrode body other than the end closest to the safety valve,
Non-aqueous electrolyte secondary battery.

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