JP2021068588A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a new non-aqueous electrolyte secondary battery in which occurrence of uneven salt concentration in an electrode body is suppressed.SOLUTION: A non-aqueous electrolyte secondary battery 1 includes an electrode body 20, a non-aqueous electrolyte solution (not shown), and a battery case 10 for accommodating the electrode body 20 and the non-aqueous electrolyte solution. The battery case 10 includes a case body 11 having an opening, and a lid member 12 for covering the opening 11a. The case body 11 has a bottom surface 11b on an opposite side to the opening 11a, and a side surface 11c that is provided to be erected continuously with the bottom surface 11b and arranged along a lamination structure. When the side surface 11c is divided into a first portion P1 on a side closer to the opening 11a and a second portion P2 on a side closer to the bottom surface 11b along one direction connecting the opening 11a and the bottom surface 11b, the average thickness of the second portion P2 not less than 0.6 time and not more than 0.75 time the average thickness of the first portion P1.SELECTED DRAWING: Figure 3

Description

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

Conventionally, a non-aqueous electrolytic solution secondary battery in which a positive electrode and a negative electrode are wound or laminated to form an electrode body, and the electrode body is housed together with a non-aqueous electrolytic solution in an outer case has been used. This secondary battery is also used in the form of an assembled battery in which a plurality of batteries are arranged and connected in series or in parallel. Patent Document 1 discloses an assembled battery in which a spacer having a convex portion is arranged between the secondary batteries so as to press a portion corresponding to the upper side of the electrode body of the secondary battery more strongly (for example, Patent Document 1). Reference 1). As a result, it is possible to prevent the electrolytic solution unevenly distributed below the electrode body from being pushed out from the electrode body that expands and contracts with charging and discharging and discharged from the electrode body. As a result, it is possible to suppress the occurrence of uneven salt concentration in the electrode body.

JP-A-2018-060755

However, in general, the convex portions provided on the spacer are provided in a plurality of linear shapes in order to secure a gap between the secondary batteries and to obtain the effect of suppressing or cooling the heat generation of the secondary battery due to charging and discharging. There is. Therefore, a large eccentric load is generated on the outer case between the upper side and the lower side, and between the portion where the linear convex portion of the spacer abuts and the portion where the spacer does not abut. As a result, in a battery for high-rate charging / discharging, when the battery expands, the convex portion of the spacer bites into the outer case, causing a secondary problem that the outer case is damaged or damaged. was there.

Therefore, an object of the present invention is to provide a new non-aqueous electrolyte secondary battery in which the occurrence of uneven salt concentration in the electrode body is suppressed.

The non-aqueous electrolytic solution secondary battery disclosed herein accommodates an electrode body having a laminated structure in which a positive electrode, a separator, and a negative electrode are laminated, a non-aqueous electrolytic solution, the electrode body, and the non-aqueous electrolytic solution. It is equipped with a battery case. The battery case includes a case body having an opening and a lid member for covering the opening. The case body includes a bottom surface opposite to the opening and side surfaces that are continuously erected on the bottom surface and arranged along the laminated structure. Here, when the side surface is divided into a first portion on the side close to the opening and a second portion on the side close to the bottom surface along one direction connecting the opening and the bottom surface, the first portion is described. The average thickness of the two portions is 0.6 times or more and 0.75 times or less the average thickness of the first portion.

According to the above configuration, when the battery case is arranged with the side of the lid member facing upward, the thickness of the case is thinner in the second portion located below than in the first portion located above. As a result, the surface pressure applied to the lower region of the electrode body becomes smaller than the surface pressure applied to the upper region of the electrode body. Therefore, by relatively reducing the surface pressure applied to the lower region of the electrode body where the electrolytic solution is likely to be unevenly distributed due to gravity and allowing the electrode body to expand in this lower region, the electrolysis that has permeated into the electrode body. It is possible to prevent the liquid from being pushed out from the electrode body and causing uneven salt concentration. As a result, it is possible to suppress an increase in battery resistance due to uneven salt concentration and maintain the high rate characteristics of the battery in a high state.

This means that the same effect can be exhibited not only in a single non-aqueous electrolyte secondary battery (single battery) but also in the form of an assembled battery in which a plurality of the batteries are constrained. Therefore, in another aspect, the technique disclosed herein has another object of providing an assembled battery using such a non-aqueous electrolyte secondary battery. In the assembled battery using the non-aqueous electrolyte secondary battery disclosed herein, for example, it is not necessary to press the region above the battery case more strongly. Therefore, the height of the convex portion of the spacer may be uniform over the entire surface of the battery case, and for example, the difference in the height of the convex portion can be made smaller than in the conventional case. As a result, the problem that the battery case is damaged or damaged by the convex portion of the spacer is solved.

It is a perspective view which shows typically the structure of the assembled battery which concerns on one Embodiment. It is a notch perspective view which shows typically the structure of the non-aqueous electrolyte secondary battery which concerns on one Embodiment. It is sectional drawing of the case main body of the non-aqueous electrolyte secondary battery which concerns on one Embodiment. It is a partial development view explaining the structure of the winding type electrode body of the non-aqueous electrolytic solution secondary battery which concerns on one Embodiment. (A) and (B) are diagrams for explaining the configuration of the convex portion of the spacer used in each example.

Hereinafter, embodiments according to the techniques disclosed herein will be described. Matters other than those specifically mentioned in the present specification and necessary for the implementation of the present technology (for example, general configurations and manufacturing processes of batteries that do not characterize the present technology) are the fields concerned. It can be grasped as a design matter of a person skilled in the art based on the prior art in. The present technology can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art. In this specification, the notation "A to B" indicating a numerical range means A or more and B or less.

[Battery set]
FIG. 1 is a perspective view schematically showing the assembled battery 100 according to the embodiment. FIG. 2 is a perspective view schematically showing the cell 1 according to the embodiment. The symbols U, D, F, Rr, L, and R in the drawings mean up, down, front, back, left, and right, respectively. The symbols X, Y, and Z in the drawings mean the width direction, the thickness direction, and the height direction of the cell 1 respectively, and the thickness direction coincides with the arrangement direction of the assembled batteries 100. In this embodiment, the width direction X, the arrangement direction Y, and the height direction Z are orthogonal to each other. Further, the arrangement direction Y is the front-rear direction, the width direction is the width direction of the cell 1 and the winding axis WL direction of the flat winding type electrode body 20 described later, and the height direction Z is the flat winding type electrode body 20. It coincides with the major axis direction and the vertical direction of the cross section. However, these are merely directions for convenience of explanation, and do not limit any mode such as arrangement and use of the assembled battery.

The assembled battery 100 includes a plurality of cell batteries 1, a plurality of spacers 60, a pair of end plates 70A and 70B, and a plurality of restraint bands 72. The cell 1 in the present embodiment has a flat rectangular parallelepiped shape, and the plurality of cell 1s are arranged along the array direction Y so that the wide side surface is orthogonal to the array direction Y. The plurality of spacers 60 are arranged between the plurality of cell cells 1 and at the ends of the front F and the rear Rr thereof in the arrangement direction Y so as to abut on the wide side surface of the cell 1. The end plates 70A and 70B are arranged in the front F and the rear Rr so as to sandwich the cell 1 and the spacer 60 in a predetermined arrangement direction Y. The plurality of restraint bands 72 are jigs having a substantially U-shaped plan view. The restraint band 72 is in a state where the arrangement of the cell 1, spacer 60 and the end plates 70A and 70B is compressed in the arrangement direction Y by a predetermined stress, and the front F is prevented from recovering in the tensile direction by a reaction force. And from the rear Rr, it is bridged so as to lock the end plates 70A and 70B.

The restraint band 72 is fixed to the end plates 70A and 70B by a plurality of screws 74. The plurality of restraint bands 72 are respectively installed so as to maintain the restraint pressure applied to the cell 1, the spacer 60, and the end plates 70A and 70B in the direction of compression along the arrangement direction Y. For the plurality of restraint bands 72, for example, the compressive load applied to the arrangement direction Y of the cell 1 can be about 0.1 to 10 tf, typically about 0.5 to 5 tf. Therefore, the length of the arrangement direction Y is designed so that the compressive stress is about 0.1 to 50 MPa, for example, about 0.5 to 10 MPa as the surface pressure (average surface pressure applied to the wide side surface). There is. Although not specifically shown, a screw may be inserted at any position between the pair of end plates 70A and 70B in order to finely adjust the restraining pressure. As a result, in the assembled battery 100, a predetermined compressive stress is inherent in the arrangement direction Y with respect to the plurality of cell cells 1 and the plurality of spacers 60. The end plates 70A and 70B, the plurality of restraint bands 72, and the plurality of screws 74 in the present embodiment are examples of restraint members. However, the restraint member is not limited to this.

The cell 1 is a non-aqueous electrolyte secondary battery disclosed herein. The non-aqueous electrolyte secondary battery refers to a general storage device capable of repeatedly charging and discharging using a non-aqueous electrolyte as an electrolyte, and is a term that includes a so-called storage battery and a storage element such as an electric double layer capacitor. .. Hereinafter, the present technology will be described by taking the case where the battery is a lithium ion secondary battery as an example. The cell 1 according to the present embodiment includes a flat wound electrode body (hereinafter, may be simply referred to as an “electrode body”) 20, a non-aqueous electrolytic solution (not shown), and a battery case 10. ..

As shown in FIG. 4, the electrode body 20 has a laminated structure in which a positive electrode 30, a separator 50, and a negative electrode 40 are laminated. The electrode body 20 having this laminated structure is a power storage element. The electrode body 20 in this embodiment is a wound electrode body. The electrode body 20 is a positive electrode body 20 in a state in which a long sheet-shaped positive electrode 30 and a long sheet-shaped negative electrode 40 are laminated with each other insulated from each other via two long sheet-shaped separators 50. The width direction W orthogonal to the longitudinal direction of the negative electrodes 30 and 40 is wound as the winding axis WL, and the negative electrodes 30 and 40 are formed so as to have an oval cross section.

The positive electrode 30 typically includes a positive electrode current collector 32 and a porous positive electrode active material layer 34 formed on both sides of the current collector 32. The positive electrode current collector 32 is provided with a current collector 32A in which the current collector is exposed once along the width direction W, and the positive electrode active material layer 34 is formed in other portions. Examples of the positive electrode current collector constituting the positive electrode 30 include aluminum foil and the like. Examples of the positive electrode active material contained in the positive electrode active material layer 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 may contain 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) or other carbon material (eg, graphite or the like) can be preferably used. As the binder, for example, polyvinylidene fluoride (PVdF) or the like can be used. The positive electrode active material layer 34 may contain, for example, a film forming agent such as trilithium phosphate (LPO) that forms a film suitable for the negative electrode 40.

The negative electrode 40 typically includes a negative electrode current collector 42 and a porous negative electrode active material layer 44 formed on both sides of the current collector 42. The negative electrode current collector 42 is provided with a current collector 42A in which the current collector is exposed once along the width direction W, and the negative electrode active material layer 44 is formed in other portions.
Examples of the negative electrode current collector constituting the negative electrode 40 include copper foil and the like. As the negative electrode active material contained in the negative electrode active material layer, for example, a carbon material such as graphite, hard carbon, or soft carbon; lithium titanate (Li ₄ Ti ₅ O ₁₂ : LTO); Si; Sn or the like can be used. The negative electrode active material layer may contain components other than the active material, such as a binder and a thickener. As the binder, for example, styrene-butadiene rubber (SBR) or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like can be used.

Examples of the separator 50 include a polyolefin resin such as polyethylene (PE) and polypropylene (PP), and a porous sheet made of a resin such as 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) containing an inorganic filler may be provided on the surface (one side or both sides) of the separator 50.

As the non-aqueous electrolyte solution, a solution in which an electrolyte salt is dissolved in a non-aqueous solvent can be preferably used. Examples of the electrolyte salt include lithium salts such _{as LiPF 6 , LiBF 4} , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N, and LiCF ₃ SO _3. The non-aqueous solvent is not particularly limited as long as the electrolyte salt can be dissolved, and carbonates, ethers, esters, nitriles, sulfones and the like can be used. Of these, the use of carbonates such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) is preferable. These can be used alone or in combination of two or more. The concentration of the electrolyte salt may be appropriately determined depending on the type of the electrolyte salt, and is typically 0.5 mol / L or more and 5 mol / L or less, preferably 0.7 mol / L or more and 2.5 mol / L or less. .. The non-aqueous electrolytic solution contains, for example, a gas generating agent such as biphenyl (BP) and cyclohexylbenzene (CHB); other film forming agent; dispersant; thickener, as long as the effect of the present technology is not significantly impaired. Etc. may be included.

In the wound electrode body 20, the width W1 of the positive electrode active material layer 34, the width W2 of the negative electrode active material layer 44, and the width W3 of the separator satisfy the relationship of W1 <W2 <W3. Further, the negative electrode active material layer 44 covers the positive electrode active material layer 34 at both ends in the width direction, and the separator 50 covers the negative electrode active material layer 44 at both ends in the width direction. The positive electrode 30, the negative electrode 40, and the separator 50 are laminated so that the positive electrode current collector 32A and the negative electrode current collector 42A project to the opposite ends in the width direction. The electrode body 20 has a battery case such that the width direction of the positive and negative electrodes 30 and 40 (that is, the winding axis direction) is the width direction of the battery case 10 and the long axis of the oval cross section is the height direction Z. It is housed in 10. Here, the positive electrode current collecting portion 32A is welded to the positive electrode current collecting terminal 38a, and the negative electrode current collecting portion 42A is welded to the negative electrode current collecting terminal 48a. The positive electrode current collecting terminal 38a and the negative electrode current collecting terminal 48a are fixed to the electrode body 20 at both ends in the width direction, and stably support the electrode body 20 at a position separated from the lid member 12. As a result, the position of the electrode body 20 in the battery case 10 is defined, and the electrode body 20 is electrically connected to the positive electrode terminal 38 and the negative electrode terminal 48, respectively. The wound electrode body 20 is electrically insulated from the battery case 10 by being covered with an insulating film (not shown).

The battery case 10 is a housing that houses the electrode body 20 and the electrolytic solution in a sealed state. The battery case 10 of the present embodiment has a relatively thin (flat) rectangular parallelepiped shape. The battery case 10 includes a case body 11 having an opening 11a and a lid member 12. The case body 11 has a bottomed square cylinder shape and is a housing having one open surface. The lid member 12 is attached to the opening 11a of the case body 11 to cover the opening 11a of the case body 11. The material of the battery case 10 is not particularly limited. As an example, the battery case 10 is preferably made of a metal material having high strength, relatively light weight, and good thermal conductivity, for example, aluminum, aluminum alloy, iron, stainless steel, nickel-plated steel, or the like. It may be there. Further, although the battery case 10 of the present embodiment has a rectangular parallelepiped shape in outer shape, it may be in another form such as a cylindrical type or a button type.

A positive electrode terminal 38 and a negative electrode terminal 48 for external connection are attached to the lid member 12 in a state of being insulated from the lid member 12. The positive electrode terminal 38 and the negative electrode terminal 48 penetrate the battery case 10 (lid member 12) and project to the outside of the battery case 10. The positive electrode terminal 38 and the negative electrode terminal 48 are electrically connected to and mechanically fixed to the positive electrode current collecting terminal 38a and the negative electrode current collecting terminal 48a in the battery case 10. As a result, the electrode body 20 can be charged or power can be supplied from the electrode body 20 to the external load via the positive electrode terminal 38 and the negative electrode terminal 48. The positive electrode current collecting terminal 38a and the negative electrode current collecting terminal 48a can be made of a metal having good electrical conductivity such as copper, nickel, and an aluminum alloy. The lid member 12 in the present embodiment is provided with a thin-walled safety valve 16 set to release the internal pressure in the battery case 10 and a liquid injection hole 18a for injecting a non-aqueous electrolytic solution. The liquid injection hole 18a is hermetically sealed by a liquid injection plug 18b. The case body 11 containing the electrode body 20 is sealed by welding the lid member 12. Further, the adjacent positive electrode terminal 38 and the negative electrode terminal 48 are electrically connected by a bus bar 14. As a result, the assembled batteries 100 of the present embodiment are electrically connected in series. However, the size, number, arrangement, connection method, etc. of the cell 1 constituting the assembled battery 100 are not limited to the modes disclosed herein, and can be appropriately changed.

The case body 11 has a bottom surface 11b opposite to the opening 11a, a pair of wide side surfaces 11c, and a pair of narrow side surfaces 11d. The bottom surface 11b is orthogonal to the height direction Z. The pair of wide side surfaces 11c are erected continuously on the bottom surface 11b along the width direction and orthogonal to the thickness direction. The pair of narrow side surfaces 11d are erected continuously on the bottom surface 11b and the pair of wide side surfaces 11b along the thickness direction and orthogonal to the width direction. The case body 11 has an opening 11a and an internal space (cavity) formed by being surrounded by the pair of wide side surfaces 11c, the bottom surface 11b, and the pair of narrow side surfaces 11d. The case body 11 accommodates the electrode body 20 in the internal space through the opening 11a above the case body 11. In the square case body 11, the wide side surface 11c is a side surface along the laminated structure of the electrode body 20. The wide side surface 11c is a surface substantially parallel to the positive and negative electrodes 30, 40 and the separator 50 that form the laminated structure of the electrode body 20. The dimensions of the case body 11 are generally adjusted to a size that can accommodate the electrode body 20 described later with less dead space. The wide side surface 11c may be deformed by being pressed from the inside when the electrode body 20 described later expands due to charging / discharging.

The case body 11 has a first portion P1 on the side closer to the opening 11a and a second portion P2 on the side closer to the bottom surface 11b along one direction (here, the height direction) connecting the opening 11a and the bottom surface 11b. It can be divided into. Generally, in the secondary battery accommodating the non-aqueous electrolytic solution, the lid member 12 (that is, the opening 11a) is installed so as to be vertically above, so that the first portion P1 is a region located above and the second portion P2. Is the area located below. Here, as shown in FIG. 3, the dimension of the case body 11 along the height direction is L, the dimension of the first portion P1 is L1, and the dimension of the second portion P2 is L2. These satisfy the relationship of "L = L1 + L2". The dimension L1 of the first portion P1 may be approximately 40% L or more and 60% L or less, and is typically approximately 50% L. The dimension L2 of the second portion P2 may be approximately 60% L or less and 40% L or more, and is typically approximately 50% L.

The material and thickness of the case body 11 are usually set according to the intended use, physique, and the like. However, according to the study by the present inventors, it has been found that the battery case does not necessarily have to have a uniform thickness as a whole as long as the strength is secured at the important points. Therefore, the wide side surface 11c of the case body 11 disclosed here is configured so that the average thickness of the second portion P2 is 0.75 times or less the average thickness of the first portion P1. Since the average thickness of the second portion P2 is thin, when the electrode body 20 expands due to charging and discharging, the electrode body 20 is accommodated in the second portion P2 rather than the first portion P1 on the side surface of the battery case 10. It is permissible to expand more by the difference in thickness. In other words, more non-aqueous electrolyte can remain impregnated in the second portion P2 than in the first portion P1. On the other hand, in the first portion P1 rather than the second portion P2, the battery case 10 restrains the electrode body 20 more strongly in the compression direction to shorten the distance between the positive and negative electrodes, and contributes to the suppression of the increase in resistance. In other words, the first portion P1 can give a higher surface pressure to the electrode body 20 when the electrode body 20 swells than the second portion P2. The average thickness of the second portion P2 is preferably 0.73 times or less, more preferably 0.7 times or less, or 0.65 times or less the average thickness of the first portion P1. However, if the second portion P2 is too thin, it may not be possible to secure the required strength of the battery case 10 depending on the application, which is not preferable. The average thickness of the second portion P2 may be, for example, about 0.6 times or more the average thickness of the first portion P1.

The thinning of the second portion P2 as described above is not limited to this, but is achieved by removing the inner surface of the wide side surface 11c of the case body 11 as shown in FIG. It is preferable to be done. Further, it is preferable that the outer surface of the wide side surface 11c of the case body 11 is flush with the first portion P1 and the second portion P2. As a result, the volume below the second portion P2 of the case body 11 can be increased, and swelling below the electrode body 20 can be easily allowed.

The average thickness of the side surface can be, for example, an arithmetic mean value of the thickness of the side surface measured at 10 points for each case body 11. For the square battery case, the arithmetic mean value obtained for the wide side surface 11c is adopted.

The average thickness of the case body 11 is not strictly limited because it depends on the use and physique of the cell 1. Typically, from the viewpoint of weight reduction, the average thickness (plate thickness) of the flat surfaces of the side surfaces (wide side surface 11c and narrow side surface 11d) is approximately 1 mm or less. As described above, the wide side surface 11c of the case body 11 has a different average thickness between the first portion P1 and the second portion P2. Therefore, the average thickness of the first portion P1 is preferably 1 mm or less, more preferably 0.9 mm or less, and may be, for example, 0.8 mm or less. However, in the cell 1 constituting the assembled battery 100, if the first portion P1 and the second portion P2 are too thin, the case main body 11 may be damaged, which is not preferable. From this point of view, the average thickness of the first portion P1 is preferably, for example, 0.65 mm or more, more preferably 0.7 mm or more, and may be, for example, 0.75 mm or more. The thickness of the second portion P2 can be appropriately set so as to be the ratio as described above with respect to the first portion P1. As an example, the average thickness of the second portion P2 may be 0.5 mm or more and 0.8 mm or less, for example, 0.5 mm or more and 0.6 mm or less.

The method of manufacturing the case body 11 of the battery case 10 is not particularly limited. From the viewpoint of manufacturing efficiency, the case body 11 may be formed mainly by drawing from one metal plate. In general, a case body 11 having a uniform thickness between the first portion P1 and the second portion P2 can be produced by deep drawing. The case body 11 according to the present technology can be manufactured, for example, by thinning the second portion P2 with respect to the case body 11 having a uniform thickness of the first portion P1 and the second portion P2. The means for thinning the layer is not particularly limited. For example, while maintaining the outer shape with a die, the portion corresponding to the second part P2 is pressed from the inside of the case, spinning, spinning, and rolling. Examples include stretching and cutting. From the viewpoint of not generating cutting chips, it is preferable to employ plastic working such as press drawing, spinning, rolling, and drawing. As an example, the case main body 11 is formed into a case main body having a predetermined outer shape and thickness by deep drawing, and then the outer shape of the case main body is maintained by a predetermined mold (die) in the second portion P2. It can be produced by plastically deforming the corresponding region thinly to a desired thickness by spinning from the inside of the case.

The spacer 60 is arranged so as to abut on the wide side surface 11c of the cell 1 and has a function of efficiently dissipating the heat generated inside the cell 1 between the plurality of cell 1. The spacer 60 is made of, for example, a resin material such as polypropylene (PP) or polyphenylene sulfide (PPS), or a metal material having good thermal conductivity. The spacer 60 typically includes a base portion 62, a rib portion (convex portion) 64, a frame portion 66, and a support portion (not shown), as shown in FIGS. 5A and 5B. The support portion is a member that supports the base portion 62. For example, when the assembled battery 100 is constructed, the support portion secures a space for sending the cooling fluid below the cell 1 and other members such as positive and negative terminals 38 and 48 above the cell 1. Secure a safety space to prevent contact with.

The base portion 62 is a main member of the spacer 60. The shape of the base portion 62 corresponds to the shape of the wide side surface 11c of the battery case 10 of the cell cell 1. The frame portion 66 projects in a frame shape in the arrangement direction at the outer edge of the base portion 62. The protruding dimension (dimension in the arrangement direction) of the frame portion 66 can be made higher than the protruding dimension T of the rib portion 64, which will be described later. The protruding dimension of the frame portion 66 is, for example, (protruding dimension T + 1 to 3 of the rib portion 64) mm. The inner dimension of the area surrounded by the frame portion 66 substantially coincides with the outer dimension of the wide side surface 11c of the cell battery 1. Therefore, the spacer 60 and the cell 1 are appropriately positioned by fitting the cell 1 to the spacer 60 so that the wide side surface 11c and the base portion 62 face each other. Further, a cooling space for introducing the cooling fluid is formed in the space surrounded by the base portion 62, the frame portion 66, and the wide side surface 11c. Although not shown in FIGS. 5A and 5B, the frame portion 66 has an inflow port for allowing the cooling fluid to flow into the cooling space from the outside of the frame portion 66, and a cooling fluid from the cooling space. An outlet for flowing out to the outside may be provided.

A plurality of rib portions 64 are integrally formed with the base portion 62 in the spacer 60. The rib portion 64 is provided so as to project from the base portion 62 in the arrangement direction. The rib portion 64 is provided on both sides of the base portion 62, that is, the front surface and the rear surface in the arrangement direction. The rib portions 64 project with the same projecting dimension (height) T. The rib portion 64 has, for example, a wall shape erected with respect to the base portion 62 so that the front view is linear. As a result, the rib portion 64 functions as a flow path wall that regulates the movement of the cooling fluid in the cooling space, and at the same time presses the wide side surface 11c of the battery case 10. In the present technology, as shown in FIG. 5B, the rib portion 64 may be designed to be arranged substantially uniformly with respect to the base portion 62. In other words, the rib portion 64 may be configured to press the wide side surface 11c substantially uniformly (evenly). For example, the area of the rib portion 64 in the area of the base portion 62 may be the same in the region corresponding to the first portion P1 and the second portion P2 of the wide side surface 11c. As a result, even when the assembled battery is constructed with a strong binding force, it is possible to prevent the wide side surface 11c of the battery case 10 from being damaged. Although not particularly limited, the height T of the rib portion 64 is typically equal to or less than the thickness of the base portion 62 (that is, the dimension in the arrangement direction), and is 2 mm or less in one example, and typically 1 mm or less. For example, 0.5 to 1 mm. The width W of the rib portion 64 in front view is typically not more than the thickness of the base portion 62, and is 2 mm or less in one example, typically 1 mm or less, for example, 0.5 to 1 mm.

According to the above configuration, the battery case 10 itself of the cell 1 includes a first portion P1 capable of applying a higher surface pressure to the electrode body 20 and a second portion P2 allowing the electrode body 20 to swell. There is. As a result, the distance between the electrodes is shortened in the first portion P1 to suppress the increase in resistance during high-rate charging / discharging, and the discharge of the electrolytic solution from the electrode body 20 due to the high-rate charging / discharging is suppressed in the second portion P2. It is possible to suppress an increase in resistance due to uneven concentration of electrolyte. As a result, the increase in resistance due to high-rate charging / discharging can be effectively reduced.

Further, according to the above configuration, when the assembled battery 100 is composed of the plurality of cell cells 1 and the spacer 60, the increase in resistance due to high-rate charging / discharging can be effectively reduced. Therefore, it is not necessary to locally change the arrangement and height of the rib portion 64 of the spacer 60. For example, the rib portion 64 of the spacer 60 can be provided uniformly and locally evenly on the wide side surface 11c. Thereby, the rib portion 64 of the spacer 60 can reduce the possibility of damaging the wide side surface 11c of the battery case.

The non-aqueous electrolyte secondary battery 1 configured as described above can be used for various purposes. Suitable applications include drive power supplies mounted on vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs) that charge and discharge at high rates. The lithium ion secondary battery 1 may also be used in the form of an assembled battery, which typically consists of a plurality of batteries connected in series and / or in parallel.

In the above description, the square lithium ion secondary battery 1 including the flat winding type electrode body 20 has been described. However, the cell 1 may include a laminated electrode body in which a plurality of plate-shaped positive electrodes 30 and 40 are laminated via a separator 50.

Hereinafter, examples relating to the present technology will be described, but the present technology is not intended to be limited to those shown in such examples.

[Manufacturing of assembled battery for evaluation]
As a battery case, a square battery case made of an aluminum alloy composed of a square case body and a lid member was prepared. Here, the case body has a thickness T1 (mm) on the opening side (hereinafter referred to as the first portion) and a bottom surface side (hereinafter referred to as the second portion) when the side surface is substantially bisected in the height direction. The thickness T2 (mm) and the one manufactured so as to have the combination shown in Table 1 below were used. That is, the battery cases of Examples 1 to 3 are battery cases manufactured by a known deep drawing process so that the thickness of the wide side surface is constant at 1.0 mm or 0.8 mm. In the battery cases of Examples 4 to 10, first, a square case having a predetermined outer shape with a thickness of T1 (mm) is formed by deep drawing, and then the outer shape of the case is maintained by a die, and a second case is formed. It is manufactured by cutting a portion corresponding to a portion from the inside of the case so as to have a thickness of T2 (mm). Regarding the thickness of the first portion and the thickness of the second portion, it was confirmed that the arithmetic mean values of the thickness measured at 10 points per case were T1 and T2 shown in Table 1. The outer shape of the battery case of Examples 1 to 10 was about 63.2 mm in height × about 137 mm in width × about 12.9 mm in thickness, all of which were the same.

An external positive electrode terminal and an external negative electrode terminal, and a positive electrode current collecting terminal and a negative electrode current collecting terminal were fixed to the lid member via insulating members, respectively. The lid member is provided with a liquid injection hole for injecting the electrolytic solution into the battery case, and a sealing member for sealing the liquid injection hole.
Further, as an electrolyte, 1 _{LiPF 6} was added to a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of EC: DMC: EMC = 30:40:30. A non-aqueous electrolyte solution dissolved at a concentration of 0.0 mol / L was prepared.

_{LiNi 1/3} Co _1/3 Mn _1/3 O ₂ (LNCM) powder as a positive electrode active material, trilithium phosphate (LPO) powder, acetylene black (AB) as a conductive material, and polyvinylidene fluoride as a binder. First, vinylidene fluoride (PVdF) was blended so that the mass ratio of LNCM: AB: PVdF = 90: 8: 2 and the content of LPO with respect to the positive electrode active material was 2.8% by mass, and N -A positive electrode slurry was prepared by mixing with methylpyrrolidone (NMP). A positive electrode sheet was prepared by applying this slurry to both sides of the strip-shaped aluminum foil, leaving an uncoated portion along one end in the width direction, applying the slurry to the other regions on both sides, drying the slurry, and then rolling pressing the slurry.

Natural graphite-based carbon material (C) as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener are used as C: SBR: CMC = 98: 1: 1. A slurry for the negative electrode was prepared by mixing with ion-exchanged water at the mass ratio of. A negative electrode sheet was prepared by applying this slurry to both sides of the strip-shaped copper foil, leaving an uncoated portion along one end in the width direction, applying the slurry to the other regions on both sides, drying the slurry, and then rolling pressing the slurry.

By using a microporous polyolefin sheet with a three-layer structure of PP / PE / PP as a base material and forming a heat-resistant layer (HRL) containing an inorganic filler on one surface of this base material, a separator sheet with HRL can be obtained. I prepared one. Then, the positive electrode sheet and the negative electrode sheet were laminated in a state of being insulated from each other via a separator sheet, and wound so as to have a substantially oval cross section to prepare an electrode body. The separators were stacked so that the HRL was arranged on the positive electrode side. The positive electrode sheet and the negative electrode sheet are different from each other so that the negative electrode active material layer protrudes from both ends of the positive electrode active material layer in the width direction, and the uncoated portion (collecting foil) of the positive electrode sheet and the negative electrode sheet is different in the width direction. They were overlapped so as to protrude in the direction. The electrode body was fixed to the lid member by welding the positive electrode current collecting terminal and the negative electrode current collecting terminal to the uncoated portions of the positive electrode and the negative electrode protruding from both ends in the winding axis direction of the electrode body.

[Insertability evaluation]
The electrode body fixed to the lid member was inserted into the case body through the opening, and it was confirmed whether the insertion at that time was smooth. The results are shown in the "Insertability" column of Table 1 below. Among the evaluations of insertability, "good" indicates that the insert could be inserted into the case without being supported by the electrode body, and "poor" indicates that the electrode body was supported and could not be inserted in the middle.
For the example using the battery case in which the electrode body could be inserted, the following test was proceeded, and in the case using the battery case in which the electrode body could not be inserted, the evaluation was discontinued.

In the example in which the electrode body could be inserted, the electrode body was heated and dried together with the case, the lid member was fitted to the case body, and the lid member and the case body were laser welded. Next, a predetermined amount of non-aqueous electrolytic solution was injected into the battery case from the injection hole of the lid member to seal the injection hole, thereby preparing a secondary battery (cell cell) for evaluation of each example. ..
Further, as a spacer, as shown in FIG. 5, (A) spacer A having both ends in the width direction and convex portions on the upper portion of one surface of the substrate, and (B) substantially evenly distributed on one surface of the substrate. A spacer B having a convex portion and a spacer B were prepared. The spacer A and the spacer B have the same shape and area of the substrate, and the area of the convex portion (that is, the contact area with the battery case) is designed to be 15% of the area of the spacer substrate.
Then, one cell of each example and the spacer A or spacer B shown in Table 1 are superposed so that the convex portion of the spacer is on the cell side, and the restraining member exerts a predetermined restraining pressure (3.8 MPa). By restraining, a simulated assembled battery for evaluation of each example was prepared.

[conditioning]
The following conditioning was performed on the simulated assembled batteries of each example. That is, in an environment of 25 ° C., a constant current (CC) charge is performed at 1 C to 4.1 V, and a constant voltage (CV) charge is performed until the current value becomes 1/50 C. The initial charging process was performed so that the SOC) was fully charged (SOC 100%). Next, an initial aging treatment was performed at 60 ° C. for 24 hours to form a film on the surface of the negative electrode active material layer. After that, CC discharge was performed at a rate of 1C up to 3.0V, and the state of charge at this time was set to SOC 0%. Note that 1C is a current value capable of charging the battery capacity (Ah) predicted from the theoretical capacity of the active material in one hour.

[High rate cycle test]
The IV resistance of the simulated assembled battery after conditioning was measured. That is, the initial resistance value (IV resistance) was obtained from the slope of the discharge curve when the simulated assembled battery adjusted to SOC 56% in an environment of 25 ° C. was discharged at 30 C for 10 seconds. Next, the assembled battery whose charging state was adjusted to SOC 40% in an environment of 25 ° C. was charged at about 30 C for 10 seconds, then discharged at 2.3 C for 125 seconds with a rest period of 5 seconds, and discharged for 5 seconds. 2000 high-rate charge / discharge cycles were performed, with the rest being one cycle. Then, the IV resistance after the cycle was measured by the above method, and the resistance increase rate was calculated based on the following equation: resistance increase rate (%) = post-cycle resistance ÷ initial resistance × 100; and is shown in Table 1.

[Case durability test]
For the simulated assembled batteries of each example, the restraint pressure was fluctuated within a fluctuation range (ΔP) ± 0.2 MPa for 100,000 cycles, and it was confirmed whether or not cracks were observed in the battery case after the cycles. The presence or absence of cracks was first visually confirmed, and if the presence or absence of cracks was unclear visually, the cross section of the suspected crack was confirmed by SEM (scanning electron microscope) in the battery case. Table 1 shows the presence or absence of cracks in the battery case.

From the comparison of Examples 1 and 2, regarding the battery case having the dimensions of the present embodiment, assuming that the thickness of the side surface is 1 mm for both the first portion on the opening side and the second portion on the bottom surface side, the opening dimension of the case becomes the electrode body. On the other hand, since it was not sufficient, it was confirmed that the insertability of the electrode body was significantly reduced. However, if the thickness of the side surface is 0.8 mm for both the first portion on the opening side and the second portion on the bottom surface side, the opening size corresponding to the electrode body of the present embodiment can be secured, and the insertability of the electrode body is good. It turned out to be. Regarding the combination of the battery case having the predetermined outer dimensions and the electrode body of the predetermined standard in the present embodiment, it was found that the critical size on the insertion surface is that the thickness of the side surface of the battery case is 0.8 mm. It was.

Next, from the comparison of Examples 2 and 3, the spacer A can locally and appropriately press the battery case and the electrode body on a wide side surface, and the increase in resistance can be suppressed to a low level even after repeated high-rate charging / discharging. I understood. On the other hand, the spacer B presses the battery case and the electrode body almost evenly from the wide side surface side, so that the electrolytic solution is discharged from the electrode body by repeating high-rate charging and discharging, and the salt concentration of the electrolytic solution becomes uneven. It was found that the increase in resistance was the largest among all cases. However, although Example 2 is an example in which a battery case having a relatively thick thickness of 0.8 mm is used for both the first portion and the second portion, the battery case is cracked due to local pressing by the spacer A. It was found that it was easy to occur and there was a problem with durability. From the above, it was found that the use of the spacer A may cause a problem in the durability of the battery case, and the use of the spacer B cannot sufficiently suppress the increase in resistance due to high-rate charging / discharging.

Examples 4 to 10 are examples in which the spacer B is used, which cannot sufficiently suppress the increase in resistance due to high-rate charging / discharging. In Examples 4 to 10, the thickness of the second portion is made thinner than that of the first portion on the side surface of the battery case, and as a result, the pressure on the electrode body by the second portion is relaxed. From this, it was found that in Examples 4 to 10, even after high-rate charging / discharging using the spacer B, the resistance increase rate is reduced by about 25% (Example 4) or more as compared with Example 3. It was.

From the comparison of Examples 3 to 7, the thinner the thickness of the second portion with respect to the first portion, the lower the resistance increase rate, and the reduction effect is saturated when the thickness of the second portion reaches 0.5 mm. I understood it. Further, in Example 7 in which the thickness of the second portion was thinner than 0.5 mm, for example 0.4 mm, it was found that there is a possibility that a problem may occur in the durability of the battery case. Therefore, it can be said that the thickness of the second portion is preferably 0.5 mm or more, for example.

In Example 4 in which the thickness of the second portion was 0.7 mm (0.88 times the thickness of the first portion), it was found that the effect of suppressing the resistance increase rate may not be sufficient. It is considered that this is because the degree of reduction in the thickness of the second portion is not sufficient. Further, from the comparison between Examples 5 and 6 and Examples 8 and 9, even if the thickness of the second portion is the same, if the thickness of the first portion is reduced, the resistance increase rate increases, and the second portion It turned out that the effect of thinning the part was offset. This indicates that increasing the thickness of the first portion and applying a certain amount of restraining pressure to the electrode body is effective in suppressing an increase in resistance due to high-rate charging / discharging. This can also be confirmed from the comparison of Examples 6, 9 and 10. From these facts, for example, in order to suppress the resistance increase rate after high-rate charging / discharging to 125% or less, the thickness of the second portion should be 0.75 times or less of the thickness of the first portion, and 0.7 times or less. Or, it can be said that it is more preferable to make it 0.65 times or less. Further, for example, in order to suppress the resistance increase rate after high-rate charging / discharging to 125% or less, it can be said that the thickness of the first portion is thicker than 0.6 mm, for example, 0.7 mm or more. As a whole, it can be said that the thickness of the second portion should exceed 0.5 times the thickness of the first portion, for example, 0.6 times or more.

According to the battery according to the present embodiment described above, it can be seen that the metal foreign matter that inevitably enters the battery case can be suppressed from being mixed into the electrode body, and the occurrence of a minute short circuit due to the metal foreign matter can be suppressed. Although specific examples of the present technology have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

1 Battery 10 Battery case 11 Case body 12 Lid member 20 Electrode body 60 Spacer 100 assembly Battery P1 1st part P2 2nd part

Claims (1)

An electrode body having a laminated structure in which a positive electrode, a separator, and a negative electrode are laminated, a non-aqueous electrolytic solution, and a battery case for accommodating the electrode body and the non-aqueous electrolytic solution are provided.
The battery case includes a case body having an opening and a lid member for covering the opening.
The case body includes a bottom surface opposite to the opening and side surfaces that are continuously erected on the bottom surface and arranged along the laminated structure.
When the side surface is divided into a first portion on the side close to the opening and a second portion on the side close to the bottom surface along one direction connecting the opening and the bottom surface, the second portion A non-aqueous electrolyte secondary battery having an average thickness of 0.6 times or more and 0.75 times or less the average thickness of the first portion.

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