JP6113972B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery including a stacked electrode group in which positive plates and negative plates are alternately stacked.

  In recent years, lithium secondary batteries have been used as power source batteries for portable electronic devices such as mobile phones and notebook computers because they have a high energy density and can be reduced in size and weight. Further, since the capacity can be increased, it has been attracting attention as a motor drive power source for electric vehicles (EV) and hybrid electric vehicles (HEV), and a storage battery for power storage.

  In the lithium secondary battery, an electrode group in which a positive electrode plate and a negative electrode plate are arranged opposite to each other with a separator interposed therebetween is housed in an outer case constituting a battery can, filled with an electrolyte, and positive electrode current collectors of a plurality of positive electrode plates A positive current collecting lead coupled to the tab; a positive external terminal electrically connected to the positive current collecting lead; a negative current collecting lead coupled to the negative current collecting tabs of the plurality of negative electrode plates; and the negative current collecting lead. It is set as the structure provided with the negative electrode external terminal electrically connected with an electrical lead.

  As the electrode group, a wound type and a laminated type are known. The wound electrode group has a configuration in which a separator is interposed between a positive electrode plate and a negative electrode plate, and is integrally wound. The laminated electrode group has a positive electrode plate and a negative electrode plate interposed via a separator. It is the structure which laminated | stacked multiple layers.

  In a lithium secondary battery including a stacked electrode group, an electrode group in which a plurality of layers of a positive electrode plate and a negative electrode plate are stacked via a separator is housed in an outer case and filled with a non-aqueous electrolyte, respectively. A positive current collecting lead connected to the positive current collecting tab of the positive electrode plate, an external terminal electrically connected to the positive current collecting lead, and a negative current collecting lead connected to the negative current collecting tab of the negative electrode plate And an external terminal electrically connected to the negative electrode current collecting lead.

  In a lithium secondary battery having a laminated electrode group having the above-described configuration, when an external force such as vibration is applied, the electrode group is displaced and the connection state between the current collecting lead and the external terminal deteriorates, or the electrode plate There is a risk of causing a short circuit due to stacking error.

  Therefore, at least one of the positive electrode plate, the negative electrode plate, and the separator is fixed to the electrode group support through the electrode group support, and the stacked electrode group is positioned in the battery container. Has already been proposed (see, for example, Patent Document 1) in which the battery does not move within the battery container and prevents damage to the positive electrode plate and the negative electrode plate.

  In addition, in the lithium secondary battery, the internal pressure rises when overcharged or overdischarged, so in order to avoid rupture of the battery can, etc., a safety valve that breaks when the internal pressure rises above a predetermined pressure, Some have a current interrupting mechanism that detects an increase in internal pressure and interrupts the current.

  In addition, in order to cut off the current by increasing the internal pressure in a thin battery, a battery with a current cut-off mechanism has already been proposed in which an easy-cut portion that breaks in response to the swelling of the battery case is provided on a part of the lead terminal plate (for example, , See Patent Document 2).

JP 2006-66319 A JP 2001-313021 A

  In order to increase the capacity of the secondary battery having the positive electrode plate, the negative electrode plate, and the electrolyte and to extend the battery life, it is preferable to increase the power generation area and increase the amount of the electrolyte to be filled. The area of the electrode plate is increased, the number of layers to be stacked is increased, and the amount of electrolyte solution to be filled tends to increase. If it does so, the capacity | capacitance of the exterior case which comprises a battery can will become large, the clearance gap between an electrode group and an exterior case will become large, and it will be in the state which an electrode group moves easily by external forces, such as a vibration.

  If an external force such as vibration is applied to the outer case and the electrode group moves, the connection between the positive electrode (negative electrode) current collector lead and the positive electrode (negative electrode) external terminal is broken, and a predetermined battery capacity cannot be obtained, which becomes a problem. . In addition, when displaced in the stacking direction, the contact distance between the positive electrode plate and the negative electrode plate is changed, which causes a problem that a predetermined battery capacity cannot be exhibited.

  Therefore, in a stacked secondary battery including an electrode group in which a large number (for example, several tens of layers) of positive electrode plates, negative electrode plates, and separators are stacked, when an external force such as vibration is applied, the electrode group is It is desired that the movement in the direction of the current collecting lead is effectively suppressed and that each electrode plate is not separated in the stacking direction and is not displaced in the surface direction. In addition, it is preferable that the stacked positive electrode plate, negative electrode plate, and all electrode plates of the separator are positioned at the same time so as not to be displaced with respect to the stacking direction and the plane direction orthogonal to the stacking direction.

  Therefore, as in the secondary battery described in Patent Document 1, it is not sufficient to fix any one of the positive electrode plate, the negative electrode plate and the separator to the electrode group support. In addition, as described above, in the stacked secondary battery, in addition to the lateral displacement in the plane direction, the vertical displacement in the stacking direction is also suppressed, and the electrode group formed by laminating a large number of electrode plates is stabilized. It is desirable to fix the position.

  Further, it is desirable that the current can be interrupted when the internal pressure increases, but it is desirable that the current interrupting function can be exhibited with a low-cost configuration without newly providing a current interrupting mechanism.

  Therefore, in view of the above problems, the present invention can suppress the displacement of the electrode group in the battery can during normal operation in a secondary battery including a stacked electrode group, and can quickly cut off the current when the internal pressure increases. It aims at providing the secondary battery which can be exhibited.

  In order to achieve the above object, the present invention provides an electrode group in which a positive electrode plate and a negative electrode plate are laminated via a separator, an outer case that contains the electrode group and is filled with an electrolyte, and an external case provided in the outer case A secondary battery comprising: a terminal; a positive / negative current collecting lead electrically connecting the positive / negative electrode plate and the external terminal; and a lid member attached to the outer case. A position shift prevention member for fixing the position at a predetermined position in the outer case is provided, and the position shift prevention member is fixed to an easily deformable portion provided at a predetermined portion of the battery can, and according to the deformation of the battery can The current collection lead is fixed to the position displacement prevention member in a direction in which the current collection lead is separated from the external terminal when the position displacement prevention member is displaced.

  According to this configuration, during normal operation, the electrode group can be fixed so as not to be displaced via the displacement prevention member, and when the internal pressure increases, the easily deformable portion of the battery can is deformed, and at the same time, the displacement prevention member is Since it is displaced, the current collecting lead can be peeled off from the external terminal via this misalignment prevention member. Therefore, it is possible to obtain a secondary battery that can suppress the displacement of the electrode group in the battery can during normal operation and that quickly exhibits a current interruption function when the internal pressure increases.

  In the secondary battery having the above-described configuration, the easily deformable portion includes a thin-walled portion provided on the lid member, and the current collecting lead is fixed to a surface of the external terminal facing the lid member. It is a feature. According to this configuration, when the internal pressure increases, the lid member expands through the thin portion that becomes the easily deformable portion, and the displacement prevention member can be displaced according to the expansion. Further, by utilizing this displacement, the current collecting lead connected to the external terminal can be peeled off from the external terminal.

  In the secondary battery having the above-described configuration, the easily deformable portion includes the thin cover member, and the current collecting lead is fixed to a surface of the external terminal facing the cover member. Yes. According to this configuration, when the internal pressure increases, the thin cover member expands, and the displacement prevention member can be displaced in accordance with the expansion. Further, by utilizing this displacement, the current collecting lead connected to the external terminal can be peeled off from the external terminal.

  Further, in the secondary battery having the above-described configuration, the electrode group includes a laminated surface parallel to a bottom surface of the outer case, and the misalignment prevention member is provided on a side surface side where the current collecting lead is provided. And a lead support portion for inserting and supporting the current collecting lead in the lateral slip prevention member, and the upper surface of the lateral slip prevention member is fixed to the lid member. According to this configuration, the lateral displacement of the electrode group can be suppressed via the lateral displacement prevention member, and when the lid member is deformed due to an increase in internal pressure, the current collecting lead supported by the lateral displacement prevention member is displaced to the outside. It can be peeled off from the terminal.

  Further, in the secondary battery having the above configuration according to the present invention, the misalignment prevention member is disposed close to a side surface side of the electrode group, and the current collecting tabs of the respective electrode plates can be respectively inserted. A first member, and a second member provided with a lead support portion that is disposed close to the external terminal and supports the current collecting lead that is connected to the current collecting tabs together. The upper surfaces of the first member and the second member are both fixed to the lid member. According to this configuration, when the internal pressure rises and the lid member is deformed, both the first member and the second member are displaced. Further, since the second member fixing the collecting portion of the current collecting lead is disposed close to the external terminal, the collecting portion can be easily peeled off from the external terminal.

  According to the present invention, in the secondary battery configured as described above, the misalignment prevention member includes a covering portion that covers the current collecting lead protruding from the lead support portion. According to this structure, even if a current collection lead peels from an external terminal, it can prevent that this current collection lead contacts an exterior case.

  According to the present invention, in the secondary battery configured as described above, the covering portion has a protruding length corresponding to a gap between the misalignment prevention member and the outer case. According to this configuration, it is possible to easily position the electrode group and the position shift prevention member with respect to the exterior case.

  According to the present invention, in the secondary battery having the above-described configuration, an opening window portion is provided in the covering portion to enable an operation of overlapping and welding the current collecting lead and the external terminal. According to this configuration, it is possible to place the current collecting lead on the external terminal, attach the position shift prevention member, and then overlap and weld the current collecting lead and the external terminal through the opening window. become.

  According to the present invention, in the secondary battery having the above configuration, the lid member is provided with a locking piece protruding toward the inside of the battery can, and the misalignment prevention member is provided with a locking portion into which the locking piece is fitted. When the lid member is deformed, the locking piece that follows the displacement moves the displacement prevention member via the locking portion. According to this configuration, when the internal pressure rises and the lid member is deformed, the locking pieces are simultaneously displaced, and the misalignment prevention member can be reliably moved and the current collecting lead can be peeled off from the external terminal.

  According to the present invention, the current collecting lead is fixed to the misalignment prevention member, and the misalignment prevention member is fixed to the easily deformable portion provided at a predetermined portion of the battery can. It is possible to obtain a secondary battery that can suppress the displacement of the group and can quickly exhibit a current interruption function when the internal pressure increases.

1 is a schematic cross-sectional view showing a first embodiment of a secondary battery according to the present invention. It is a schematic sectional drawing explaining the electric current interruption function with which the secondary battery which concerns on this invention is provided. It is a front view which shows an example of a position shift prevention member. It is a cross-sectional schematic diagram which shows 2nd Embodiment of the secondary battery which concerns on this invention. It is a cross-sectional schematic diagram which shows 3rd Embodiment of the secondary battery which concerns on this invention. It is a principal part enlarged view of 4th Embodiment of the secondary battery which concerns on this invention. It is a top view of the position shift prevention member shown to FIG. 6A. It is a principal part enlarged view of 5th Embodiment of the secondary battery which concerns on this invention. It is AA cross section of FIG. 7A, Comprising: It is sectional drawing which shows the mounting structural example of a position shift prevention member. It is a disassembled perspective view of a secondary battery. It is a disassembled perspective view of the electrode group with which a secondary battery is provided. It is a perspective view which shows the completed product of a secondary battery. It is a schematic sectional drawing of an electrode group.

  Embodiments of the present invention will be described below with reference to the drawings. Moreover, the same code | symbol is used about the same component, and detailed description is abbreviate | omitted suitably.

  A lithium secondary battery will be described as the secondary battery according to the present invention. For example, the secondary battery RB1 according to this embodiment shown in FIG. 1 is a stacked lithium secondary battery, and includes a stacked electrode group 1 in which a plurality of positive electrode plates and negative electrode plates are stacked via a separator. I have. Further, by increasing the area of the electrode plate and increasing the number of stacked layers, it becomes a secondary battery having a relatively large capacity, and can be applied to a storage battery for electric vehicles or a storage battery for power storage.

  Next, specific configurations of the stacked lithium secondary battery RB and the electrode group 1 will be described with reference to FIGS.

  As shown in FIG. 8, the stacked lithium secondary battery RB has a rectangular shape in plan view, and includes an electrode group 1 in which a positive electrode plate, a negative electrode plate, and a separator, each of which is rectangular, are stacked. Moreover, it accommodates in the battery can 10 comprised from the exterior case 11 and the cover member 12 which are provided with the bottom part 11a and the side parts 11b-11e, and is made into a box shape, and the side surface (for example, side part 11b, The charging / discharging is performed from an external terminal 11f provided on two opposing side surfaces of 11c.

  The electrode group 1 has a configuration in which a plurality of positive electrode plates and negative electrode plates are laminated via a separator, and as shown in FIG. 9, a positive electrode active material is formed on both surfaces of a positive electrode current collector 2b (for example, an aluminum foil). The positive electrode plate 2 having the positive electrode active material layer 2a formed thereon and the negative electrode plate 3 having the negative electrode active material layer 3a formed of the negative electrode active material formed on both surfaces of the negative electrode current collector 3b (for example, copper foil) It is laminated through.

  Although the separator 4 insulates the positive electrode plate 2 and the negative electrode plate 3 from each other, lithium ions can be transferred between the positive electrode plate 2 and the negative electrode plate 3 through the electrolyte filled in the outer case 11. It has become.

Here, as the positive electrode active material of the positive electrode plate 2, oxides of lithium is contained (such as _{LiCoO 2, LiNiO 2, LiFeO 2} , LiMnO 2, LiMn 2 O 4) or a part of the transition metal in the oxide And a compound in which is substituted with other metal elements. Among these, in a normal use, if a material that can use 80% or more of lithium held in the positive electrode plate 2 for the battery reaction is used as the positive electrode active material, safety against accidents such as overcharge can be improved.

  Further, as the negative electrode active material of the negative electrode plate 3, a material containing lithium or a material capable of inserting / removing lithium is used. In particular, in order to have a high energy density, it is preferable to use a lithium insertion / extraction potential close to the deposition / dissolution potential of metallic lithium. A typical example is natural graphite or artificial graphite in the form of particles (scale-like, lump-like, fibrous, whisker-like, spherical and pulverized particles).

  In addition to the positive electrode active material of the positive electrode plate 2, and in addition to the negative electrode active material of the negative electrode plate 3, a conductive material, a thickener, a binder, and the like may be contained. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance of the positive electrode plate 2 or the negative electrode plate 3. For example, carbon black, acetylene black, ketjen black, graphite (natural graphite, artificial graphite) ), Carbonaceous materials such as carbon fibers, conductive metal oxides, and the like can be used.

  As the thickener, for example, polyethylene glycols, celluloses, polyacrylamides, poly N-vinyl amides, poly N-vinyl pyrrolidones and the like can be used. The binder serves to hold the active material particles and the conductive material particles together, and includes a fluorine-based polymer such as polyvinylidene fluoride, polyvinyl pyridine and polytetrafluoroethylene, a polyolefin polymer such as polyethylene and polypropylene, Styrene butadiene rubber or the like can be used.

  Moreover, as the separator 4, it is preferable to use a microporous polymer film. Specifically, films made of a polyolefin polymer such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, polybutene can be used.

  Moreover, it is preferable to use an organic electrolytic solution as the electrolytic solution. Specifically, as an organic solvent for the organic electrolyte, esters such as ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, dioxolane , Diethyl ether, dimethoxyethane, diethoxyethane, methoxyethoxyethane, and other ethers, dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate, and methyl acetate can be used. These organic solvents may be used alone or in combination of two or more.

Further, the organic solvent may contain an electrolyte salt. Examples of the electrolyte salt include lithium perchlorate (LiClO ₄ ), lithium borofluoride, lithium hexafluorophosphate, trifluoromethanesulfonic acid (LiCF ₃ SO ₃ ), lithium fluoride, lithium chloride, lithium bromide, and iodide. And lithium salts such as lithium and lithium tetrachloroaluminate. In addition, these electrolyte salts may be used independently and may be used in mixture of 2 or more types.

  The concentration of the electrolyte salt is not particularly limited, but is preferably about 0.5 to about 2.5 mol / L, and more preferably about 1.0 to 2.2 mol / L. When the concentration of the electrolyte salt is less than about 0.5 mol / L, the carrier concentration in the electrolytic solution is lowered, and the resistance of the electrolytic solution may be increased. On the other hand, when the concentration of the electrolyte salt is higher than about 2.5 mol / L, the dissociation degree of the salt itself is lowered, and there is a possibility that the carrier concentration in the electrolytic solution does not increase.

  The battery can 10 includes an outer case 11 and a lid member 12, and is made of iron, nickel-plated iron, stainless steel, aluminum, or the like. Further, in the present embodiment, as shown in FIG. 10, the battery can 10 is formed so that the outer shape is substantially a flat rectangular shape when the outer case 11 and the lid member 12 are combined. ing.

  The outer case 11 is a box shape having a bottom portion 11a having a substantially rectangular bottom surface and four side portions 11b to 11e erected from the bottom portion 11a, and the electrode group 1 is accommodated inside the box shape. To do. The electrode group 1 includes a positive current collecting lead coupled to a current collecting tab of the positive electrode plate and a negative current collecting lead coupled to the current collecting tab of the negative electrode plate, and is electrically connected to these current collecting tabs. External terminals 11 f are provided on the sides of the outer case 11. The external terminal 11f is provided, for example, at two locations on the opposite two side portions 11b and 11c. Reference numeral 10a denotes a liquid injection port from which an electrolytic solution is injected.

  After the electrode group 1 is accommodated in the outer case 11 and each current collecting lead is connected to the external terminal, or each external terminal is connected to the current collecting lead of the electrode group 1 and accommodated in the outer case 11, After fixing the terminal to a predetermined portion of the outer case, the lid member 12 is fixed to the opening edge of the outer case 11. Then, the electrode group 1 is sandwiched between the bottom portion 11 a of the outer case 11 and the lid member 12, and the electrode group 1 is held inside the battery can 10. The lid member 12 is fixed to the exterior case 11 by, for example, laser welding. Further, the connection between the current collecting lead and the external terminal can be performed using a conductive adhesive in addition to welding such as ultrasonic welding, laser welding, and resistance welding.

  As described above, the stacked secondary battery according to the present embodiment includes an electrode group 1 in which a plurality of positive electrode plates 2 and negative electrode plates 3 are stacked via a separator 4, and the electrode group 1 is accommodated in an electrolyte solution. , An external terminal 11f provided on the external case 11, positive and negative current collecting leads that electrically connect the positive and negative electrode plates and the external terminal 11f, and a lid member attached to the external case 11 12.

  For example, as shown in FIG. 11, the electrode group 1 accommodated in the outer case 11 includes a positive electrode plate 2 in which a positive electrode active material layer 2a is formed on both surfaces of a positive electrode current collector 2b, and both surfaces of a negative electrode current collector 3b. The negative electrode plate 3 on which the negative electrode active material layer 3a is formed is laminated via the separator 4, and the separator 4 is disposed on both end faces. Moreover, it is good also as a structure which replaces with the separator 4 of both end surfaces, and winds the resin film of the same material as this separator 4, and coat | covers the electrode group 1 with the resin film which has insulation. In any case, the upper surface of the laminated electrode group 1 has a configuration in which members having electrolyte permeability and insulating properties are laminated. Therefore, the lid member 12 can be brought into direct contact with this surface and can be pressed with a predetermined pressure via the lid member 12.

  The lid member 12 may have a flat plate shape or a flat plate shape, and may have a dish shape that fits inside the can. When the dish-shaped lid member is used, it is possible to prevent the lid member from moving when welding the lid member, and the welding operation is facilitated. Moreover, it can respond easily to the change of the thickness of the electrode group to accommodate by changing the amount of depressions of a dish shape.

  In addition, when the battery can 10 becomes larger and the electrode group 1 is thicker due to the increase in capacity, when the external force such as vibration is applied, the electrode group 1 is displaced in the battery can and collected current. There is an increased risk that the lead and external terminals will be deformed or damaged. Further, it is desirable that the current can be interrupted when the internal pressure increases, but it is desirable that the current interrupting function can be exhibited with a low-cost configuration without newly providing a current interrupting mechanism.

  Therefore, in the present embodiment, the secondary battery is configured to be able to suppress the positional deviation of the electrode group in the battery can during normal operation and to quickly exhibit the current interruption function when the internal pressure increases. For this purpose, a displacement prevention member for fixing the electrode group 1 at a predetermined position in the exterior case 11 is provided, and the current collecting lead 5 is secured to the displacement prevention member, and is formed from the exterior case 11 and the lid member 12. A thin easily deformable portion is provided at a predetermined portion of the battery can 10 and the displacement prevention member is fixed to the easily deformable portion, and is displaced according to the deformation of the easily deformable portion to release the connection with the external terminal 11f. By adopting such a configuration, the misregistration prevention member can simultaneously exhibit the misregistration prevention function and the current interruption function.

  Next, a specific embodiment of a secondary battery having the above-described configuration will be described with reference to FIGS. FIG. 1 shows a schematic cross-sectional view of the secondary battery RB1 of the first embodiment, FIG. 4 shows a schematic cross-sectional view of the secondary battery RB1 of the second embodiment, and FIG. 5 shows the secondary battery of the third embodiment. The cross-sectional schematic diagram of battery RB1 is shown. FIG. 2 is a schematic cross-sectional view for explaining the current interruption function, and FIG. 3 shows an example of a misalignment prevention member.

<First Embodiment>
A secondary battery RB1 of the first embodiment shown in FIG. 1 includes an electrode group 1 in which a plurality of layers of a positive electrode plate and a negative electrode plate are stacked via a separator, and an exterior case that contains the electrode group 1 and is filled with an electrolyte. 11, an external terminal 11 f provided in the outer case 11, a positive / negative current collecting lead 5 that electrically connects the positive and negative electrode plates and the external terminal, and a lid member 12 </ b> A attached to the outer case 11. Type secondary battery. Further, in order to suppress the positional deviation of the electrode group 1, a positional deviation preventing member 6 is provided, and further, an easily deformable portion is provided on the lid member 12A, and the positional deviation preventing member 6 is fixed to the easily deformable portion.

  The misregistration prevention member 6 is, for example, a lateral deviation prevention member that suppresses lateral deviation of the electrode group 1 on which the current collecting leads 5 are provided. For this purpose, as shown in FIG. 3, a misalignment prevention member 6 is installed on the side of the electrode group 1 where the current collection leads 5 are provided, and the current collection lead is located at the center of the body of the misalignment prevention member 6. An elongated insertion hole 61 through which 5 can be inserted is formed. As this misalignment prevention member 6, a foam having insulating properties (for example, polyethylene or polypropylene foam) is used. In particular, a foam made of polyethylene is suitable as a misalignment prevention member used in this embodiment because it is excellent in mechanical strength and chemical resistance and also in heat resistance.

  The current collecting lead 5 is preferably fixed to the insertion hole 61. For this purpose, the size of the insertion hole 61 may be fixed so as to fit the sheet-metal current collecting lead 5 tightly, or may be bonded and fixed after fitting. In any case, the insertion hole 61 serves as a lead support portion for inserting and supporting the current collecting lead 5.

  The secondary battery RB1 assembled with the displacement prevention member 6 can be fixed so that the electrode group 1 is not displaced. Therefore, even if an external force such as vibration is applied, the electrode group 1 is not displaced and the terminal is damaged. Absent. Further, when the internal pressure rises, the easily deformable portion of the battery can 10A is deformed, and at the same time, the displacement prevention member 6 is displaced. Therefore, the current collection lead 5 is connected to the external terminal by using the displacement of the displacement prevention member 6. It can be peeled off from 11f. Therefore, it is possible to obtain the secondary battery RB1 that can suppress the positional deviation of the electrode group 1 in the battery can during normal operation and that quickly exhibits a current interruption function when the internal pressure increases.

  An easily deformable part is realizable by providing a thin part in the predetermined site | part of a battery can. In the present embodiment, the lid member 12A is provided with an easily deformable portion. This easily deformable portion may be formed from a thin portion provided on the lid member, or may be formed from an easily deformable portion 12Aa having a reduced overall plate thickness. Therefore, as shown by the solid line in the figure, the entire lid member 12A may be the easily deformable part 12Aa, and as shown by the broken line in the figure, the frame part fixed to the exterior case 11 is thickened, Only the central part can be made thin so as to be easily deformed.

  In short, the lid member 12A may be configured to easily expand as the internal pressure increases, and may be configured to fix the misalignment prevention member 6 to the easily deformable easily deforming portion. Therefore, when the internal pressure of the battery can 10A rises, the lid member 12A expands through the thin wall portion that becomes the easily deformable portion, or the thin plate thickness lid member 12A expands, and the displacement prevention is performed according to these expansions. The member 6 can be displaced. Further, by utilizing this displacement, the current collecting lead 5 connected to the external terminal 11f can be peeled off from the external terminal 11f.

  In the secondary battery RB1 having the above-described configuration including the easily deformable portion 12Aa, when the internal pressure rises due to the overcharge or overdischarge state, the easily deformable portion 12Aa is largely deformed first to a state as shown in FIG. . Further, by fixing the misalignment preventing member 6 to the easily deformable portion 12Aa by bonding or the like, the misalignment preventing member 6 can be displaced together with the easily deformable portion 12Aa.

  Therefore, if the current collecting lead 5 is fixed in a direction away from the external terminal 11f when the displacement prevention member 6 is displaced according to the deformation of the battery can 10A, that is, on the upper side of the external terminal 11f, the current collecting lead 5 is easily deformed. The displacement prevention member 6 is displaced according to the deformation of the portion 12Aa, and the current collecting lead 5 can be peeled off from the external terminal 11f.

  For example, when the current collecting lead 5 is placed on the external terminal 11f and overlapped and welded, and the welding conditions are set to a welding depth of 0.5 mm, a welding width of 1 mm, and a welding length of about 20 mm, It was confirmed that welding was peeled off when the deformed portion 12Aa expanded by 10 mm.

  At this time, the misalignment prevention member 6 can be fixed to the easily deformable portion 12Aa by using an adhesive (BM-140S manufactured by Zeon Corporation). The same adhesive is also used when the current collecting lead 5 is bonded and fixed to the insertion hole 61. That is, the current collection lead 5 is bonded and fixed to the insertion hole 61 of the position shift prevention member 6, the current collection lead 5 is welded and fixed to the external terminal 11f, and then the position shift prevention member 6 is bonded and fixed to the easily deformable portion 12Aa. The secondary battery RB1 having the above configuration can be manufactured by the procedure of fixing the lid member 12A.

  The lid member 12 </ b> A may have a flat plate shape as shown in the figure, or may have a dish shape in which a portion contacting the upper surface of the electrode group 1 protrudes in a convex shape and fits into the outer case 11. Therefore, 2nd Embodiment using the plate-shaped cover member 12B is described using FIG.

Second Embodiment
FIG. 4 is a schematic cross-sectional view showing the secondary battery RB2 of the second embodiment. The secondary battery RB2 is the same as the secondary battery RB1 of the first embodiment described above except for the shape of the lid member.

  The lid member 12B provided in the secondary battery RB2 has a dish shape, and the easily deformable portion provided in the lid member 12B is entirely configured as shown in the figure, even if only the central portion described above is thinned. The thin easily deformable portion 12Ba may be used.

  Even in this configuration, the current collecting leads 5 connected to the current collecting tabs of the respective electrode plates are inserted and fixed to the insertion holes 61 of the misalignment preventing member 6, and the current collecting leads 5 are welded and fixed to the external terminals 11f. Then, the positional deviation preventing member 6 can be bonded and fixed to the easily deformable portion 12Ba, so that the positional deviation preventing member 6 can simultaneously exhibit the positional deviation preventing function and the current interruption function.

  That is, even with the dish-shaped lid member 12B, by providing the easily deformable portion 12Ba having a thin plate thickness, the current collecting lead 5 can be peeled off from the external terminal 11f when the internal pressure increases. The easily deformable portion 12Ba can be deformed.

  Next, a third embodiment in which the misalignment prevention member 6 is composed of a plurality of members will be described with reference to FIG.

<Third Embodiment>
The misalignment prevention member shown in FIG. 5 is disposed close to the side surface side of the electrode group 1, and approaches the first member 6B through which the current collecting tab of each electrode plate can be inserted, and the external terminal 11f. And a second member 6A provided with a lead support portion for inserting and fixing and supporting the current collecting leads 5 collectively connecting the current collecting tabs.

  In addition, the present embodiment is configured such that the displacement prevention member abuts on the upper surface of the electrode group 1 and can suppress longitudinal displacement in the stacking direction, and both the upper surfaces of the first member 6B and the second member 6A are covered with the lid member. It is fixed (adhered) to 12B (easily deformable portion 12Ba). With this configuration, when the internal pressure rises and the lid member (the easily deformable portion 12Ba) is deformed, both the first member 6B and the second member 6A are displaced. Further, since the second member 6A for fixing the current collecting lead 5 which is the collecting portion of the current collecting tab is disposed close to the external terminal 11f, the current collecting lead 5 can be easily connected to the external terminal 11f. It can be peeled off.

  That is, in this embodiment, the second member 6 </ b> A serves as a misalignment prevention member including a lead support portion that inserts and supports the current collecting lead 5. Even in this case, the easily deformable portion may be deformed as the internal pressure increases, and the second member 6A serving as the lead support portion may be displaced in synchronization with the internal pressure. You may comprise as.

  Furthermore, by devising the shape of the misalignment prevention member 6 made of a foam having insulating properties, it becomes possible to achieve safety and ease of assembly. Such an embodiment is illustrated as a fourth embodiment. This will be described with reference to 6A and FIG. 6B.

<Fourth embodiment>
The position shift prevention member 6C illustrated in FIG. 6A includes a covering portion 62 that covers the current collecting lead 5 protruding from the lead support portion (insertion hole 61). Moreover, it is preferable that this coating | coated part 62 has insulation. Therefore, even if it is the position shift prevention member 6C made of a foam having an insulating shape integrally provided with the covering portion 62 protruding from the main body portion of the position shift prevention member 6C, the foam having a separate insulation property. 6C of position shift prevention members which combined the body may be sufficient.

  As described above, if the configuration has the covering portion 62 that covers the current collecting lead 5 protruding from the lead support portion (insertion hole 61), even if the current collecting lead 5 is peeled off from the external terminal 11f, the current collecting lead 5 Can be prevented from coming into contact with the outer case 11 and safety is improved.

  In addition, the protruding length L1 of the covering portion 62 is preferably a length corresponding to the gap between the misalignment prevention member 6C and the outer case 11. With this configuration, the covering portion 62 can be positioned in contact with the inner surface of the outer case 11, so that the electrode group 1 and the displacement prevention member 6C can be easily positioned with respect to the outer case 11.

  Further, as shown in FIG. 6B, it is preferable to provide an opening window 63 in the covering 62. If it is this structure, the overlap welding of the external terminal 11f and the current collection lead | read | reed 5 can be easily performed through this opening window part 63. FIG. Further, since the step of the opening window 63 can be recognized during the welding operation, the positioning operation is facilitated.

Further, since the lid member and the misregistration prevention member can be fixed by a method other than the above-described bonding, an embodiment using a method other than the bonding is used as a fifth embodiment with reference to FIGS. 7A and 7B. I will explain.

<Fifth Embodiment>
The misalignment prevention member 6D of the fifth embodiment shown in FIG. 7A is configured to include a locking portion 64 that is mechanically coupled to the lid member. That is, the locking portion 64 is a groove formed in a T shape with an insertion groove 64a and a locking groove 64b, and a locking piece that engages with the insertion groove 64a and the locking groove 64b is formed on the lid member. The lid member and the misalignment prevention member are fixed by providing and fitting the locking piece into the locking portion 64.

  For example, as shown in FIG. 7B showing an example of a mounting configuration of the misalignment prevention member 6D in the AA cross-sectional direction in FIG. 7A, a locking piece 12Ca having a reverse T-shaped cross section is provided below the lid member 12C. The position shift preventing member 6D can be fixed by fitting the stop piece 12Ca into the engaging portion 64 of the position shift preventing member 6D.

  With this configuration, the lower extending portion of the locking piece 12Ca provided on the lid member 12C is fitted and locked in the locking groove 64b, so that when the lid member 12C is displaced, the displacement prevention member 6D can be displaced integrally. become. That is, when the internal pressure rises and the lid member 12C is deformed, the locking pieces 12Ca are simultaneously displaced, and the misalignment prevention member 6D can be reliably moved to peel off the current collecting lead 5 from the external terminal 11f. Obviously, in addition to this mechanical coupling, the aforementioned adhesion may be used simultaneously.

  Next, the actually produced lithium secondary battery will be described.

(Example)
[Preparation of positive electrode plate]
LiFePO4 (90 parts by weight) as a positive electrode active material, acetylene black (5 parts by weight) as a conductive material, and polyvinylidene fluoride (5 parts by weight) as a binder are mixed, and N- A slurry is prepared by appropriately adding methyl-2-pyrrolidone to disperse each material, and the slurry is uniformly applied on both sides of an aluminum foil (thickness 20 μm) as a positive electrode current collector and dried, and then rolled. It compressed with the press and cut | disconnected by predetermined size, and produced the plate-shaped positive electrode plate 2. As shown in FIG.

  Moreover, the size of the produced positive electrode plate was 140 mm × 250 mm, the thickness was 230 μm, and 70 positive electrode plates 2 were used.

[Preparation of negative electrode plate]
Natural graphite (90 parts by weight) as a negative electrode active material and polyvinylidene fluoride (10 parts by weight) as a binder are mixed, and N-methyl-2-pyrrolidone as a solvent is appropriately added to each material. A slurry is prepared by dispersing, and the slurry is uniformly applied on both sides of a copper foil (thickness 16 μm) as a negative electrode current collector and dried, then compressed by a roll press, and cut into a predetermined size. A plate-like negative electrode plate 3 was produced.

  Further, the size of the produced negative electrode plate was 142 mm × 255 mm, the thickness was 146 μm, and 71 negative electrode plates 2 were used.

  Further, as a separator, 140 polyethylene films having a size of 145 mm × 255 mm and a thickness of 25 μm were prepared.

[Preparation of non-aqueous electrolyte]
A non-aqueous electrolyte was prepared by dissolving 1 mol / L of LiPF ₆ in a mixed solution (solvent) in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 30:70.

[Production of battery cans]
As materials for the outer case and the lid member constituting the battery can, nickel-plated iron plates were used, respectively. In addition, the outer case has a plate thickness of 0.8 mm, the lid member has a plate thickness of 0.4 mm, and the longitudinal direction × short direction × depth has internal dimensions, 320 mm × 150 mm × 40 mm battery can size. Then, a rectangular lithium secondary battery with an inlet plug that can be opened and closed was produced. The lid member was a flat plate.

[Assembly of secondary battery]
A positive electrode plate and a negative electrode plate are alternately laminated via a separator. At that time, 70 positive electrode plates, 71 negative electrode plates, and 140 separators were laminated so that the negative electrode plate was located outside the positive electrode plate, and this laminate was used a polyethylene film having a thickness of 25 μm as the separator. As a structure to be wound, an electrode group (laminated body) having a thickness of about 30 mm was constructed.

  As described above, the size of the separator interposed between the positive and negative electrode plates is 145 mm × 255 mm, which is slightly larger than the positive electrode plate (140 × 250) and the negative electrode plate (142 × 255). Thereby, the active material layer formed on the positive electrode plate and the negative electrode plate can be reliably coated. Moreover, the connection piece of the current collection member (current collection lead) was connected to the current collector exposed portion of the positive electrode and the current collector exposed portion of the negative electrode.

  As the displacement prevention member 6, a polyethylene foam having a size of 30 mm (thickness) × 150 mm × 40 mm was used on the lateral side. In addition, a polyethylene foam having a size of 4 mm (thickness) × 255 mm × 40 mm on the side in the longitudinal direction and a size of 10 mm (thickness) × 142 mm × 255 mm were used on the laminate. Moreover, the thing of a transversal direction was fixed to the cover member using the adhesive agent (The thing which is not corroded by electrolyte solution: For example, BM-140S by Nippon Zeon Co., Ltd.).

  As the external case external terminal member, an aluminum plate having a size of 35 mm × 30 mm × 2 mm was used on the positive electrode side. Moreover, the copper plate of the same size was used for the negative electrode side. Further, as the current collecting lead, a 20 mm × 30 mm × 0.7 mm aluminum member was used on the positive electrode side, and a nickel member of the same size was used on the negative electrode side. Then, the electrode group to which the current collecting lead is connected is housed in the exterior case, a position shift prevention member is installed, the current collecting lead and the external terminal are connected, the lid member is attached and sealed, and the non-water is introduced from the liquid injection hole. The electrolyte was injected under reduced pressure. After the liquid injection, the liquid injection hole was sealed, and 10 secondary batteries of each embodiment were produced.

  Example 1 corresponds to the secondary battery RB1 of the first embodiment, and a position shift prevention member in the short direction is bonded and fixed to the lid member. Moreover, although a comparative example is the same structure, the position shift prevention member of a transversal direction is not adhesive-fixed.

  In each of the examples and comparative examples, 10 pieces were produced and overcharge tests were conducted. In this test, an overcharged state was established by applying a constant current of 50 A to a fully charged battery. In addition, the current is continuously applied until the current interruption is confirmed or until the electrolyte is ejected from the safety valve.

  Using the 10 secondary batteries of Example 1 and Comparative Example, the above-described overcharge test was conducted to confirm the presence or absence of current interruption, the presence or absence of electrolyte spillage, and the presence or absence of peeling of the current collecting leads. The experimental results are shown in Table 1.

  When the current interruption was insufficient, the internal pressure continued to rise and then the electrolyte spilled out from the safety valve. The presence or absence of this phenomenon was confirmed. As a result of the above overcharge test, in Example 1 (corresponding to the first embodiment), current interruption was confirmed in all 10 pieces, of which 6 pieces had the current collecting lead on the negative electrode side peeled and 4 pieces However, the current collecting lead on the positive electrode side was peeled off. In addition, in all cases, there was no spilled electrolyte, and the secondary battery according to Example 1 was found to have a current interruption function and exhibit high safety.

  However, in the comparative example in which the position shift prevention member was not bonded and fixed, current interruption was confirmed in three of the ten samples, but in all cases, the safety valve was subsequently opened and electrolyte spillage occurred. That is, it was confirmed that the secondary battery according to the comparative example has an insufficient current interruption function and an insufficient safety.

  As described above, in the secondary battery according to the present embodiment, the electrode group can be fixed so as not to be displaced through the misalignment preventing member during normal operation, and the battery can can be easily removed in the event of an abnormal increase in internal pressure. Since the deformed portion is deformed and the misalignment preventing member is displaced at the same time, the current collecting lead can be peeled off from the external terminal via the misalignment preventing member. Therefore, it is possible to obtain a secondary battery that can suppress the displacement of the electrode group in the battery can during normal operation and that quickly exhibits a current interruption function when the internal pressure increases.

  In addition, since the easily deformable portion can be formed by reducing the thickness of the lid member, the current collecting lead can be connected to the external terminal according to the deformation of the battery can by fixing the displacement prevention member to the thin portion of the lid member. Can be peeled off.

  In addition, if the misalignment prevention member has a covering portion that covers the current collecting lead, the current collecting lead can be prevented from coming into contact with the outer case when the current collecting lead is peeled off from the external terminal. Will improve. In addition, the positioning of the electrode group and the position shift prevention member with respect to the outer case becomes easy.

  As mentioned above, the structure intended to prevent misalignment during normal operation exhibits a current interruption function when the internal pressure rises, so there is no need for a separate current interruption structure and it is safe while reducing the cost of the secondary battery. Performance and ease of assembly can be exhibited.

  That is, according to the present invention, in a secondary battery including a stacked electrode group, the position deviation of the electrode group in the battery can can be suppressed during normal operation, and a current interruption function can be quickly exhibited when the internal pressure increases. Thus, a secondary battery that exhibits safety and ease of assembly can be obtained.

  Therefore, the secondary battery according to the present invention can be suitably used for a large-capacity storage battery that requires performance stabilization and safety.

DESCRIPTION OF SYMBOLS 1 Electrode group 2 Positive electrode plate 3 Negative electrode plate 4 Separator 5 Current collection lead 6 Position shift prevention member 6A 1st member (position shift prevention member)
6B Second member (position shift prevention member)
6C, 6D Position shift prevention member 10 Battery can 11 Exterior case 11f External terminal 12 Lid member 12A, 12B Lid member 12Aa, 12Ba Easily deformable part 61 Insertion hole (lead support part)
62 Covering part 63 Opening window part RB, RB1 to RB3 Secondary battery

Claims (9)

An electrode group in which a positive electrode plate and a negative electrode plate are laminated via a separator, an outer case that contains this electrode group and is filled with an electrolyte, an external terminal provided in the outer case, the positive and negative electrode plates, and the external A secondary battery comprising positive and negative current collecting leads for electrically connecting terminals and a lid member attached to the outer case,
While providing a displacement prevention member for fixing the electrode group at a predetermined position in the outer case,
The current collecting lead is fixed to the misalignment prevention member, and the misalignment prevention member is configured to be fixed to an easily deformable portion provided at a predetermined portion of the battery can.
When the easily deformable portion is deformed by an increase in internal pressure of the battery can, and the displacement prevention member is displaced in accordance with the deformation, the current collecting lead is moved in a direction away from the external terminal. A secondary battery, which is fixed to a position shift prevention member.   The secondary battery according to claim 1, wherein the easily deformable portion includes a thin portion provided on the lid member, and the current collecting lead is fixed to a surface of the external terminal facing the lid member. .   The secondary battery according to claim 1, wherein the easily deformable portion includes the lid member having a thin plate thickness, and the current collecting lead is fixed to a surface of the external terminal facing the lid member.   The electrode group has a laminated surface parallel to the bottom surface of the outer case, and the misalignment prevention member has a lateral displacement prevention member provided on a side surface where the current collecting lead is provided. The secondary battery according to any one of claims 1 to 3, wherein a lead support portion for inserting and supporting the electric lead is provided, and an upper surface of the lateral displacement prevention member is fixed to the lid member. The displacement prevention member is disposed close to the side surface side of the electrode group, and is disposed close to the external member and a first member through which current collecting tabs of the respective electrode plates can be inserted. And a second member provided with a lead support part for inserting and fixing and supporting the current collecting leads to which the current collecting tabs are connected together, and the upper surfaces of the first member and the second member are both The secondary battery according to claim 4, wherein the secondary battery is fixed to the lid member.   The secondary battery according to claim 4, wherein the misalignment prevention member has a covering portion that covers the current collecting lead protruding from the lead support portion.   The secondary battery according to claim 6, wherein the covering portion has a protruding length corresponding to a gap between the misalignment prevention member and the exterior case.   8. The secondary battery according to claim 6, wherein the covering portion is provided with an opening window portion that enables an operation of superposing and welding the current collecting lead and the external terminal. 9.   The lid member is provided with a locking piece protruding toward the inside of the battery can, the locking member is provided with a locking portion into which the locking piece is fitted, and the displacement follows the displacement when the lid member is deformed. 9. The secondary battery according to claim 1, wherein the locking piece moves the displacement prevention member via the locking portion. 10.

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