JP2009048965A - Battery pack, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack capable of exhibiting a stable battery performance over a long term, and to provide a manufacturing method thereof. <P>SOLUTION: As for the battery pack 10, a plurality of single cells 12 in which an electrode body having a form that sheet-shaped electrodes are overlapped over each other is housed into a container together with an electrolytic solution are arranged in a plurality of numbers in a prescribed direction and restricted in a state applied with a load in the arranging direction. At the lower side in the vertical direction of the plurality of the single cells 12, a position restricted by the load larger than that of the upper side in the vertical direction of the single cells 12 is installed. Such a constitution is achieved, for example, by means that upper part restriction bands 211, 212 and lower part restriction bands 213, 214 bridged over in the arranging direction of the single cells 12 are arranged by making a position different in the vertical direction and that the restriction load of the lower part restriction band arranged more downward is made larger than that of the upper part restriction bands 211, 212. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an assembled battery formed by arranging a plurality of unit cells and a method for manufacturing the assembled battery.

An assembled battery formed by arranging a plurality of unit cells in a predetermined direction as a unit cell, such as a lithium ion battery, a nickel hydride battery or other secondary battery or a capacitor, which can obtain a light and high energy density, is mounted on a vehicle. It is becoming increasingly important as a power source for computers, or as a power source for personal computers and mobile terminals. In one typical configuration of such an assembled battery, the plurality of unit cells are constrained in a state where a load is applied in the arrangement direction in order to collect the plurality of unit cells in a compact manner and prevent mutual displacement. Yes. Patent Documents 1 to 3 are cited as prior art documents relating to this type of assembled battery.
In addition, an assembled battery in which a plurality of lithium ion batteries that are lightweight and have a high energy density are connected in series as single cells is expected to be particularly preferably used as a high-output power supply for vehicles.

JP-A-9-115490 JP 2001-68081 A JP-A-9-120808

  By the way, in the case of using a unit cell having a configuration in which a sheet-like electrode is stacked in a container together with a liquid electrolyte (electrolyte) as the unit cell, the electrolyte is used in the manufacturing process. Even if it is properly distributed to each part (typically sufficiently permeating the entire electrode body), there may be a portion where the electrolytic solution is partially insufficient due to long-term use or the like. . Since the arrangement of the electrolyte solution is affected by gravity, such a shortage of electrolyte solution (so-called “liquid drainage” phenomenon) is likely to occur particularly in a portion of the electrode body located on the upper side in the vertical direction. Occurrence of such an event is not preferable because there is a possibility that the battery performance is deteriorated.

  The present invention has been made to solve the above-described problems in the above-described conventional assembled battery, and can prevent the occurrence of the liquid withdrawing phenomenon and exhibit stable battery performance over a long period of time. The purpose is to provide. Moreover, this invention is providing the method of manufacturing such an assembled battery, and a vehicle provided with this assembled battery.

  According to the present invention, there is provided an assembled battery including a plurality of unit cells (typically, secondary batteries such as lithium ion batteries) in which electrode bodies in a form in which sheet-like electrodes are stacked are accommodated in a container together with an electrolytic solution. Provided. The plurality of single cells are arranged in a predetermined direction and are restrained in a state where a load is applied in the arrangement direction. Here, the restraint is such that a portion restrained by the load larger than the upper side in the vertical direction of the unit cells is provided on the lower side in the vertical direction of the plurality of unit cells.

  In general, a unit cell constituting an assembled battery (typically, an electrode body mainly constituting the unit cell) expands and contracts due to charging / discharging (that is, variation in the state of charge (SOC)), temperature change, and the like. At this time, if a part of the unit cell is constrained more strongly than the other part (that is, in a state where a larger load is applied), the part is relatively strongly restrained during the expansion. A kind of pumping action can be generated in which the electrolyte in the tank is sent out to a relatively weakly restrained portion. Therefore, according to the assembled battery disclosed herein, the lower side in the vertical direction of the assembled battery (hereinafter sometimes simply referred to as “lower”) is the upper side in the vertical direction of the assembled battery (hereinafter simply referred to as “upper”). By being restrained more strongly than the side, the electrolyte can be pushed up (moved) from the lower side to the upper side by the pumping action. As a result, the occurrence of the above-mentioned liquid withering can be prevented, and the state in which the electrolytic solution has been properly distributed to each part of the electrode body can be maintained. Therefore, according to the assembled battery according to the present invention, stable performance can be exhibited over a longer period.

  In the present specification, the “single cell” is a term indicating individual power storage elements constituting the assembled battery, and includes batteries and capacitors of various compositions unless specifically limited. The “secondary battery” refers to a battery that can be repeatedly charged, and includes so-called storage batteries such as lithium ion batteries and nickel metal hydride batteries. The electric storage element constituting the lithium ion battery is a typical example included in the “unit cell” referred to herein, and the lithium ion battery module including a plurality of such unit cells is disclosed in the “assembled battery” Is a typical example. In the technology disclosed herein, a predetermined number of single cells (for example, lithium ion batteries) having a flat outer shape are arranged in a direction in which the flat surfaces are stacked (stacking direction), and electrode terminals of the single cells are arranged in series. Or it can apply especially preferably to the assembled battery formed by connecting in parallel.

The assembled battery disclosed herein includes, as a preferred embodiment, a plurality of restraining bands that are spanned in the arrangement direction of the plurality of unit cells and restrain the plurality of unit cells. The plurality of restraint bands are arranged at different positions in the vertical direction. The restraint band disposed on the lower side in the vertical direction is configured to restrain the plurality of single cells with a greater restraining force than the restraint band disposed on the upper side in the vertical direction.
According to the assembled battery having such a configuration, the restraining force of the restraining band that restrains the lower side is made larger than the restraining band that restrains the upper side relatively (in other words, the lower restraining band is tightened more strongly). ) By adjusting the load applied to the part restrained by each restraining band by a simple method, and the restraint state where the place where a stronger load (restraint load) is applied to the lower side of the assembled battery as described above is provided Can be formed more accurately. Therefore, since the action of pushing up the electrolytic solution can be appropriately performed in the unit cell constituting the assembled battery, it is possible to more reliably maintain the state where the electrolytic solution is properly distributed to each part of the electrode body. Therefore, according to the assembled battery of this aspect, stable performance can be exhibited over a longer period.

  The assembled battery disclosed herein may be configured to include end plates that are disposed at both ends in the arrangement direction of the plurality of unit cells and are restrained together with the unit cells. According to such a configuration, a restraining load is applied to the plurality of single cells via the end plate. Therefore, a location where a relatively large load is applied to the lower side of the assembled battery and a relatively upper position of the assembled battery are compared. It is possible to easily realize a restraint state in which the load gradually changes between the places where a small load is applied. In an assembled battery in such a constrained state, the action of pushing up the electrolytic solution in the unit cell constituting the assembled battery can be made to work more appropriately, so that the state in which the electrolytic solution is properly distributed to each part of the electrode body is more It can be reliably maintained. Therefore, according to the assembled battery of this aspect, stable performance can be exhibited over a longer period.

  The technique disclosed herein is, for example, a wound electrode body obtained by winding the stacked sheet-like electrode, and the winding direction is such that the arrangement direction is a side surface direction of a winding axis. The present invention can be preferably applied to an assembled battery including a unit cell having a configuration in which a rotating electrode body is accommodated in the container. The wound electrode body generally expands and contracts more greatly in the side surface direction of the winding shaft than in the winding shaft direction. Therefore, according to the unit cell including the wound electrode body arranged so that the side surface direction of the wound shaft is the arrangement direction (that is, the direction in which the restraining load is applied), the action of pushing up the electrolyte can be more appropriately performed. Therefore, it is possible to more reliably maintain the state in which the electrolytic solution is properly distributed to each part of the electrode body. Therefore, according to the assembled battery including the single battery having the above-described configuration, stable performance can be exhibited over a longer period.

According to the present invention, a method for manufacturing an assembled battery including a plurality of single cells is also provided. The method includes preparing (manufacturing, purchasing, etc.) a plurality of unit cells in which an electrode body in a form in which sheet-like electrodes are superimposed is housed in a container together with an electrolytic solution. Further, the method includes arranging the plurality of unit cells in a predetermined direction. Further, the method includes restraining the plurality of arranged single cells in a state where a load is applied in the arrangement direction. Here, the restraint is performed such that a portion restrained by the load larger than the upper side in the vertical direction of the unit cells is provided below the plurality of unit cells.
According to such a method, an assembled battery that can maintain the state in which the electrolyte is appropriately distributed to each part of the electrode body by the above-described pumping action by providing a portion that is restrained more strongly than the upper side on the lower side in the vertical direction. Can be manufactured properly. Therefore, according to the assembled battery manufactured by the method of the present invention, stable performance can be exhibited over a longer period. The above manufacturing method can be preferably employed as a method for manufacturing any of the assembled batteries disclosed herein.

  Any of the assembled batteries disclosed herein (which may be an assembled battery manufactured by any of the methods disclosed herein) can exhibit stable performance over a long period of time as described above. It is suitable as an assembled battery (for example, a power source for a motor (electric motor) of a vehicle such as an automobile) mounted on the vehicle. Therefore, according to this invention, the vehicle provided with one of the assembled batteries disclosed here is provided.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention (for example, configuration and manufacturing method of positive electrode, negative electrode and separator, manufacturing method of electrode body, assembled battery for vehicle) The mounting method) can be grasped as a design matter of those skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
The assembled battery according to the present invention can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Accordingly, as schematically shown in FIG. 7, the present invention provides a vehicle (typically an automobile equipped with an electric motor such as an automobile, particularly a hybrid automobile, an electric automobile, and a fuel cell automobile) 1 having such an assembled battery 10 as a power source. I will provide a.

  An assembled battery manufactured by applying the technology disclosed herein is a single battery (typically, an electrode body in which sheet-like electrodes (a positive electrode sheet and a negative electrode sheet) are overlapped and accommodated in a container together with a liquid electrolyte. The battery may be an assembled battery in which unit cells having a flat box-shaped outer shape are arranged and restrained in the arrangement direction (stacking direction), and the configuration of each unit cell is not particularly limited. Examples of a single battery suitable as an application target of the present invention include secondary batteries such as a lithium secondary battery (for example, a lithium ion battery), a nickel metal hydride battery, and an electric double layer capacitor. In particular, application to an assembled battery in which a lithium ion battery is a single battery is preferable. Since the lithium ion battery is a secondary battery that can achieve high output at a high energy density, a high-performance assembled battery, in particular, an assembled battery for a vehicle (battery module) can be constructed. The present invention is also suitable as an assembled battery in which a plurality of arranged single cells are connected in series or in parallel (typically in series) and a method for manufacturing the battery.

  Although not intended to be particularly limited, hereinafter, a flat box-shaped (rectangular) lithium ion battery is referred to as a single cell, and a plurality of the single cells have a wide surface (the surface having the largest area). The present invention will be described in detail by taking as an example an assembled battery arranged in an overlapping direction (stacking direction) and connected in series. Moreover, in the following drawings, the same code | symbol is attached | subjected to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted or simplified.

The cell constituting the assembled battery according to the embodiment shown below is typically a predetermined battery constituent material (positive and negative electrodes on each positive and negative electrode current collector, as in the case of the single battery equipped in the conventional assembled battery. And an electrode body having a sheet-like electrode, a separator and the like in which the active material is held, and a container for housing the electrode body and an appropriate liquid electrolyte (electrolyte).
As an example, as shown in FIGS. 1 and 2, the assembled battery 10 according to this example includes a plurality (typically about 10 to 50, for example, 28) of unit cells 12 having the same shape arranged in the stacking direction. Is provided. The unit cell 12 includes a container 14 having a shape (a flat box shape in this embodiment) that can accommodate a flat wound electrode body to be described later. The assembled battery 10 is typically used in a posture in which the stacking direction is substantially horizontal, in other words, in a posture in which the wide surface 14A of the flat box-shaped container 14 is substantially vertical (for example, mounted in a vehicle). )

The container 14 is provided with a positive electrode terminal 15 electrically connected to the positive electrode of the wound electrode body and a negative electrode terminal 16 electrically connected to the negative electrode of the electrode body. As shown in the figure, one positive terminal 15 and the other negative terminal 16 are electrically connected by a connector 17 between adjacent unit cells 12. Thus, the assembled battery 10 of the desired voltage is constructed | assembled by connecting each cell 12 in series.
These containers 14 may be provided with a safety valve or the like for venting the gas generated inside the container as in the case of a conventional single cell container. Since the configuration of the container 14 itself does not characterize the present invention, a detailed description is omitted.

  The material of the container 14 is not particularly limited as long as it is the same as that used in the conventional unit cell. Appropriately imparting a restraining load that is different between the upper and lower sides to each unit cell (especially, the electrode body accommodated in the container) to facilitate effective pumping action due to expansion and contraction of the unit cell, and for mounting on a vehicle or the like From the viewpoint of suitability, materials suitable for the implementation of the present invention include materials that are relatively lightweight and are easily deflected by restraint loads. For example, a container made of a metal (for example, aluminum or steel), a container made of a synthetic resin (for example, a polyolefin resin such as polyethylene or polypropylene, or a high melting point resin such as polyethylene terephthalate, polytetrafluoroethylene, or polyamide resin) is preferable. Can be used. Alternatively, a resin film container conventionally used as a battery exterior body, for example, an outer surface (protection) layer composed of a high-melting resin (for example, a high-melting resin such as polyethylene terephthalate, polytetrafluoroethylene, or polyamide-based resin) A barrier layer composed of a metal foil (for example, aluminum or steel) (that is, a layer capable of blocking gas and moisture) and a heat-fusible resin (a resin having a relatively low melting point, such as ethylene vinyl acetate or polyethylene, It may be a laminate film container having a three-layer structure with an adhesive layer made of a polyolefin-based resin such as polypropylene. The container 14 according to this example is made of aluminum having a wall thickness of about 0.8 mm.

  As shown in FIG. 1 and FIG. 2, the plurality of single cells 12 having the same shape are reversed one by one so that the positive terminals 15 and the negative terminals 16 are alternately arranged, and the wide surface of the container 14. 14A (that is, a surface corresponding to a flat surface of a wound electrode body 30 described later housed in the container 14) is arranged in a facing direction. A cooling plate 11 having a predetermined shape is arranged in close contact with the wide surface 14 </ b> A of the container 14 between the arranged unit cells 12 and both outsides in the unit cell arrangement direction (stacking direction). The cooling plate 11 functions as a heat radiating member for efficiently radiating the heat generated in each unit cell during use, and introduces a cooling fluid (typically air) between the unit cells 12. It has a possible frame shape (for example, an uneven shape when viewed from the side like a comb shape shown in the figure). A cooling plate 11 made of metal having good thermal conductivity or lightweight and hard polypropylene or other synthetic resin is suitable.

  A pair of end plates is disposed on the outer side of the cooling plate 11 arranged on both outsides of the unit cell 12 and the cooling plate 11 (hereinafter collectively referred to as “single cell group 24”). 18 and 19 are arranged. A plurality of fastening cells are attached so that the whole cell group 24 and the end plates 18 and 19 (hereinafter also referred to as “constrained bodies”) 20 are attached so as to bridge (connect) the end plates 18 and 19. The restraint band 21 is restrained in a state where a load is applied in the stacking direction (arrangement direction) of the restrained bodies 20.

  More specifically, as shown in FIG. 1, the plurality of restraining bands 21 are arranged at the same height along one side surface and the other side surface of the restrained body 20 in the arrangement direction of the restrained body 20. A pair (two) of upper restraint bands 211, 212 spanned and substantially the same along one side surface and the other side surface of the restraint body 20 in the vertical direction below these upper restraint bands 211, 212. It consists of another pair (two) of lower restraint bands 213 and 214 spanned in the arrangement direction of the restrained body 20 at a height. The upper restraint bands 211 and 212 and the lower restraint bands 213 and 214 are arranged substantially in parallel with different heights in the vertical direction. The upper restraining bands 211 and 212 are connected to the end plates 18 and 19 at both ends in the longitudinal direction of the restraining bands 211 and 212 so that the upper portion of the restrained body 20 is restrained by a predetermined restraining force (constraint load) F1. For example, it is attached by fixing with a rivet 22. The lower restraining bands 213 and 214 restrain the lower portion of the restrained body 20 with a predetermined restraining force (constraint load) F2 larger than the restraining force F1 (that is, F2> F1). Both ends of the bands 213 and 214 in the longitudinal direction are attached to the end plates 18 and 19 by fixing them with rivets 22, respectively.

The restraint force (upper restraint load) F1 and restraint force (lower restraint load) F2 are, for example, about 20% to 95% (preferably 30% to 90%) of the upper restraint load F1 with the lower restraint load F2 being 100%. For example, it can be set to be 50% to 80%. Further, F1 and F2 can be set so that the lower restraint load F2 is larger than the upper restraint load F1 by about 1 × 10 ³ N (about 100 kgf), preferably about 2 × 10 ³ N or more. The upper limit of the difference between the lower restraint load F2 and the upper restraint load F1 is not particularly limited, but it is usually appropriate that the difference between the restraint loads (F2−F1) is about 10 × 10 ³ N (about 1000 kgf) or less. is there. For example, the upper restraint load F1 is about 6 × 10 ³ N to 8 × 10 ³ N (about 600 kgf to 800 kgf, for example 700 kgf), and the lower restraint load F2 is about 10 × 10 ³ N to 12 × 10. ³ N (about 1000 kgf to 1200 kgf, for example, 1100 kgf). The upper restraint load referred to here indicates the total restraint load (restraint force) applied by the two upper restraint bands 211 and 212. The same applies to the lower restraint load.

  The upper restraint bands 211 and 212 are positioned slightly lower (for example, about 10 to 30 mm) than the upper end of the wide surface 14A of the unit cell 12 (that is, the upper corner of the container 12), and the lower restraint bands 213 and 214 are It is arranged at a position slightly higher (for example, about 10 to 30 mm) than the lower end of the wide surface 14A of the unit cell 12 (that is, the lower end corner of the container 12). By disposing the corners in such a position, the restraining force by the restraining bands 21 is appropriately applied to the wide surface 14A of each unit cell 12, and the pumping action by the expansion and contraction of the unit cell 12 is more efficiently performed. It can be demonstrated. In addition, in FIGS. 1 and 2, an example is shown in which the restraint band spanned along one side surface of the restrained body 20 and the restraint band spanned along the other side surface are separate. For example, the upper portion of the restrained body 20 is restrained by a single restraining band attached so as to go around the end plate 19 from the end plate 18 and return to the end plate 18, and by another restraining band similarly configured. The lower part of the restrained body 20 may be restrained.

  The material and shape of the end plates 18 and 19 are not particularly limited as long as a larger restraining load can be applied to the lower part of the unit cell group 24 arranged between the end plates than to the upper part of the unit cell group 24. In other words, the end plates 18 and 19 may be made of materials and shapes that can appropriately reflect the difference between the restraining loads F1 and F2 as a difference in force that compresses the unit cell group 24 in the arrangement direction. For example, an end plate mainly composed of metal, ceramic, resin (resin reinforced by blending fibers and the like) and a composite material thereof can be used. In this embodiment, an end plate made of fiber reinforced plastic in which glass fiber is blended with nylon 66 at a ratio of 30 to 40% by mass was used. The end plate is formed in a plate shape having a thickness of about 15 mm and having substantially the same planar shape (that is, a rectangular shape) as the wide surface 14A of the unit cell 12. As a method for coupling the end plate and the restraining band (that is, a restraining band fixing method), for example, screwing may be employed in addition to the riveting as described above.

Next, the cell 20 used for construction of the assembled battery 10 will be described. The unit cell 20 has a sheet-like positive electrode 32 (hereinafter also referred to as “positive electrode sheet 32”) and a sheet-like negative electrode 34 (hereinafter also referred to as “negative electrode sheet 34”), similarly to a wound electrode body of a normal lithium ion battery. Are laminated together with a total of two sheet-like separators 36 (hereinafter also referred to as “separator sheet 36”), wound in the longitudinal direction, and then the obtained wound body is laterally oriented (transverse direction with respect to the winding axis). ) And squeezed away.
Here, the positive electrode sheet 32 and the negative electrode sheet 34 are wound in a state in which the positions are slightly shifted in the width direction of these long sheets. As a result, as shown in FIG. 2, one end in the width direction of the positive electrode sheet 32 is provided at one end and the other end in the winding axis direction of the wound electrode body 12. The positive electrode active material layer forming portion, the negative electrode active material layer forming portion of the negative electrode sheet 34, and the portion where the separator sheet 36 is wound tightly), and the positive electrode protruding portion 32A protruding outward, and the width direction of the negative electrode sheet 34 A negative electrode protruding portion 34 </ b> A in which one end thereof protrudes outward from the wound core portion 19 is formed. A positive electrode lead terminal 32B and a negative electrode lead terminal 34B are attached to the positive electrode protruding portion (ie, the non-formed portion of the positive electrode active material layer) 32A and the negative electrode protruding portion (ie, the non-formed portion of the negative electrode active material layer) 34A, respectively. Lead terminals 32B and 34B are electrically connected to the positive electrode terminal 15 and the negative electrode terminal 16, respectively.

The material and the member constituting the wound electrode body 30 may be the same as those of a conventional lithium ion battery, and are not particularly limited. For example, the positive electrode sheet 32 can be formed by applying a positive electrode active material layer for a lithium ion battery on a long positive electrode current collector. For the positive electrode current collector, an aluminum foil (this embodiment) or other metal foil suitable for the positive electrode is preferably used. As the positive electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. Preferable examples include lithium transition metal oxides such as LiNiO ₂ , LiCoO ₂ , and LiMn ₂ O ₄ . For example, an aluminum foil having a length of 2 to 6 m (for example, 4.5 m), a width of 8 to 15 cm (for example, 12 cm), and a thickness of about 5 to 20 μm (for example, 15 μm) is used as a current collector. A positive electrode active material layer for lithium ion batteries mainly composed of lithium nickelate is formed by a conventional method (for example, lithium nickelate 88% by mass, acetylene black 10% by mass, polytetrafluoroethylene 1% by mass, carboxymethylcellulose 1% by mass). Thus, a suitable positive electrode sheet 32 is obtained.

  On the other hand, the negative electrode sheet 34 can be formed by applying a negative electrode active material layer for a lithium ion battery on a long negative electrode current collector. For the negative electrode current collector, a copper foil (this embodiment) or other metal foil suitable for the negative electrode is preferably used. As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides (such as lithium titanium oxide), and lithium transition metal nitrides. For example, a copper foil having a length of 2 m to 6 m (for example, 5 m), a width of 8 cm to 15 cm (for example, 12 cm), and a thickness of about 5 μm to 20 μm (for example, 10 μm) is used. A suitable negative electrode sheet 34 is obtained by forming a negative electrode active material layer for lithium ion batteries (for example, 98% by mass of graphite, 1% by mass of styrene butadiene rubber, and 1% by mass of carboxymethyl cellulose).

  Moreover, as a suitable separator sheet 36 used between the positive / negative electrode sheets 32 and 34, what was comprised with the porous polyolefin-type resin is illustrated. For example, a porous material made of a synthetic resin (for example, made of polyolefin such as polyethylene or polypropylene) having a length of 2 to 6 m (for example, 5.5 m), a width of 8 to 12 cm (for example, 10 cm), and a thickness of about 5 to 30 μm (for example, 25 μm). A separator sheet can be suitably used.

The obtained flat wound electrode body 30 is accommodated in the container 14 so that the winding axis is laid down as shown in FIG. 4 and an appropriate supporting salt (for example, a lithium salt such as LiPF ₆ ). A single battery 12 is constructed by injecting and sealing a nonaqueous electrolyte such as a mixed solvent of diethyl carbonate and ethylene carbonate (for example, a mass ratio of 1: 1) containing an appropriate amount (for example, concentration 1M). The injection amount of the non-aqueous electrolyte (amount used per unit cell) is such that the electrolyte is properly distributed to each part of the battery components (therefore, the wound electrode body 30 is accommodated in the container 14). The wound electrode body 30 including the upper part and the center of the wound in a state of being fully infiltrated between the sheets of the electrode body 30), and some electrolyte remains as a surplus. It is appropriate to use a quantity. This excess electrolyte solution (surplus electrolyte solution) stays in the lower part of the container 14 by gravity. It is preferable that the amount of electrolyte used is such that the excess electrolyte stored below can immerse a part of the lower side of the electrode body 30.

  The unit cells 14 thus configured are arranged together with the cooling plate 11 as described above to form a unit cell group 24, and further, end plates 18 and 19 are disposed on both outer sides of the constrained body 20. Are restrained by two pairs (four in total) of restraining bands 21 so as to satisfy the predetermined restraining loads F1 and F2 described above. Then, the assembled battery 10 which concerns on this embodiment is obtained by connecting the positive electrode terminal 15 and the negative electrode terminal 16 of the adjacent cell 12 in series with the connection tool 17. FIG.

  The function of the assembled battery 10 thus configured will be described. That is, each unit cell 12 constituting the assembled battery 10 has a portion restrained by the lower restraint bands 213 and 214 (upper restraint band 211 as compared with the place restrained by the upper restraint bands 211 and 212 as described above. , 212 is more strongly restrained in the vertical direction (lower than the part restrained at 212). Thus, a portion restrained by a restraining load larger than the upper side in the vertical direction of the unit cell is provided on the lower side in the vertical direction of the unit cell 12. In FIG. 4, the difference in the restraint load depending on the position in the vertical direction is schematically represented as the length of the arrow toward the wide surface 14 </ b> A of the container 14. In such a restrained state, when the wound electrode body 30 tries to expand in the thickness direction (in the stacking direction of the unit cells 12) due to charging / discharging (that is, variation in the state of charge (SOC)), temperature change, or the like, the expansion is resisted. The restraining load presses the lower part of the unit cell 12 (electrode body 30) more strongly than the upper part. As a result, as schematically shown by a thick arrow in the figure, the electrolytic solution at the lower part of the unit cell 12 is pushed upward (in the opposite vertical direction) (pumping action). Accordingly, the electrolyte can be supplied (supplemented) to the upper portion of the electrode body 30 where the electrolyte tends to be insufficient due to long-term use or the like.

In order to confirm the effect of applying the configuration of the present invention, the following experiment was performed. That is, the unit cell 12 according to the above embodiment (here, eight lithium ion batteries are used as the unit cell 12), the cooling plate 11, and the end plates 18 and 19 are arranged as shown in FIG. The restraint load (total) of the upper restraint bands 211 and 212 is 700 kgf (approximately 7 × 10 ³ N), and the restraint load (total) of the lower restraint bands 213 and 214 is 1100 kgf (approximately 1.1 × 10). ³ N), and the terminals of adjacent unit cells were connected in series to produce the assembled battery 10 according to the example. On the other hand, the set according to the embodiment except that the restraint load (total) of the upper restraint bands 211 and 212 and the restraint load (total) of the lower restraint bands 213 and 214 are both 1000 kgf (about 1 × 10 ³ N). The assembled battery 10 according to the comparative example was produced in the same manner as the production of the battery 10.

The assembled batteries according to these examples and comparative examples were adjusted to a SOC of 60% by CC-CV charging. Each assembled battery is discharged at a constant power (W) of 40 W, 60 W, 80 W and 100 W, and the time (discharge seconds) from the start of discharge until the battery voltage drops to 3.0 V (discharge cut voltage) is measured. did. By plotting the power value (W) in the constant power discharge against the discharge seconds, a power value at which the discharge seconds becomes 2 seconds was obtained, and this was used as the initial discharge output at room temperature of the assembled battery. .
Next, these assembled batteries were charged at a constant current (10 A) from 3.0 V to 4.1 V under a condition of 60 ° C., and then, at a constant current (10 A) from 4.1 V to 3.0 V at the same temperature. The number of cycles corresponding to the maximum use in the market was repeated (charge / discharge cycle test at 60 ° C.). For the assembled battery after the cycle test, the discharge output (post-cycle discharge output) was measured by the same method as the initial discharge output. And when the initial discharge output for each assembled battery was set to 100% and the ratio (output maintenance rate) of the post-cycle discharge output of the assembled battery to the initial discharge output was calculated, the post-cycle discharge output of the assembled battery according to the example was The output retention rate was improved by 10 to 15% compared to the post-cycle discharge output of the assembled battery according to the comparative example. This result shows that the assembled battery according to the example is less deteriorated than the assembled battery according to the comparative example, and maintains stable battery performance (here, discharge output) over a longer period.

  As described above, some of the preferred embodiments of the assembled battery manufacturing method of the present invention and the assembled battery that can be manufactured by the method have been described in detail, but the present invention is not intended to be limited to such specific embodiments.

For example, in the above-described embodiment, the restraint loads of a plurality of restraint bands arranged at different positions in the vertical direction are made to be restrained by the load larger than the upper side on the lower side of the cells constituting the assembled battery. However, the method for realizing the restraint state is not limited to the above-described embodiment. For example, as shown in FIG. 5, the shape of the end plates 118 and 119 arranged on both outer sides of the unit cell group 24 is a shape in which a portion thicker than the upper side is provided on the lower side in the vertical direction (here, the inner side of the array). In other words, the end plates 118 and 119 having a shape that is thicker from the top to the bottom by configuring the surface facing the unit cell group 24 as a tapered surface are illustrated.) Also by the structure which restrained the center part with the restraint band 21, the said restraint state is realizable similarly to the said embodiment.
Further, as shown in FIG. 6, both end portions 21 </ b> A and 21 </ b> B that wrap around the outer surfaces of the end plates 18 and 19 of the restraining band 21 and are fixed to the end plates 18 and 19 are formed from above the restraining band 21. It is good also as a shape which becomes thick inside (side facing the outer surface of the end plates 18 and 19) toward the lower part. In addition, a method in which a part or all of the cooling plates constituting the unit cell group are formed in a shape in which a portion thicker than the upper portion is provided in the lower portion of the cooling plate (for example, a tapered shape that becomes thicker downward), As a separate member from the cooling plate, a spacer member having a thicker (e.g., plate-like) lower part than the upper part is sandwiched in any part of the constrained body. ) Can be used as appropriate.

  1 and 2, the restraint band 21 is disposed so that the upper restraint bands 211 and 212 and the lower restraint bands 213 and 214 are bridged between the end plates 18 and 19 along the side surface of the restrained body 20. However, the arrangement of the restraining bands is not limited to such an embodiment. For example, one upper restraining band extends from the end plate 18 along the upper surface of the restrained body 20 and reaches the end plate 19. It is good also as an aspect.

  Further, in the above-described embodiment, the electrode body 30 is accommodated in the container 14 in such a direction that the winding axis of the wound electrode body 30 is in the width direction of the unit cell 12 (that is, lying down). The electrode body 30 may be accommodated in the container 14 in a direction that is the height direction of the battery 12 (vertical direction in FIG. 2). Further, instead of the wound type electrode body 30, a laminated type electrode body in which a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately laminated together with a separator sheet may be used. The invention disclosed herein is a unit cell in which electrode bodies having various configurations are accommodated in a container (especially a wound type or a laminate type electrode body, and a sheet constituting the electrode body is a laminate of unit cells. The present invention can be preferably applied to an assembled battery in which a plurality of single cells housed in a container in an overlapping direction are arranged in the stacking direction.

In addition, the type of unit cell constituting the assembled battery is not limited to the above-described lithium ion battery, but batteries having various contents with different electrode body constituent materials and electrolytes, for example, lithium secondary batteries having lithium metal or a lithium alloy as a negative electrode, It may be a nickel metal hydride battery, a nickel cadmium battery, or an electric double layer capacitor.
In addition, the assembled battery 10 shown in FIG. 1 has a simple configuration in order to explain the present invention, but various modifications and additions of equipment can be made without impairing the configuration and effects of the present invention. It is clear to the contractor. For example, when mounted on a vehicle such as an automobile, an exterior cover for protecting the main part (unit cell group, etc.) of the assembled battery, a part for fixing the assembled battery to a predetermined part of the vehicle, a plurality of assembled batteries ( However, the presence or absence of such equipment does not affect the technical scope of the present invention.

It is a perspective view which shows the structure of the assembled battery which concerns on one Embodiment. It is a side view which shows the structure of the assembled battery which concerns on one Embodiment. It is a front view which shows typically an example of a wound electrode body. It is sectional drawing which shows typically the structure of the cell of the assembled battery which concerns on one Embodiment. It is a side view which shows typically the structure of the assembled battery which concerns on other one Embodiment. It is a side view which shows typically the structure of the assembled battery which concerns on other one Embodiment. It is a side view which shows typically the vehicle (automobile) provided with the assembled battery.

Explanation of symbols

1 Vehicle (Automobile)
10 assembled battery 12 single cell 14 container 14A wide surface 18, 19, 118, 119 end plate 20 restrained body 21 restraint band 211, 212 upper restraint band (restraint band)
213, 214 Lower restraint band (restraint band)
24 cell group 30 wound electrode body

Claims (6)

An assembled battery including a plurality of unit cells in which a sheet-like electrode is stacked and an electrode body is housed in a container together with an electrolyte,
The plurality of single cells are arranged in a predetermined direction and restrained in a state where a load is applied in the arrangement direction,
Here, the restraint is an assembled battery in which a portion restrained by the load larger than the upper side in the vertical direction of the unit cells is provided on the lower side in the vertical direction of the plurality of unit cells. A plurality of restraining bands that are spanned in the arrangement direction of the plurality of unit cells and restrain the plurality of unit cells;
The plurality of restraint bands are arranged at different positions in the vertical direction, and the restraint band placed on the lower side in the vertical direction has a greater restraining force than the restraint band placed on the upper side in the vertical direction. The assembled battery according to claim 1, wherein the assembled battery is configured to restrain the single battery.   The assembled battery according to claim 1, further comprising end plates disposed at both ends in the arrangement direction of the plurality of unit cells and restrained together with the unit cells.   The electrode body is a wound electrode body formed by winding the stacked sheet-like electrodes, and the wound electrode body is accommodated in the container in a direction in which the arrangement direction is a side surface direction of the winding axis. The assembled battery according to any one of claims 1 to 3. A method of manufacturing a battery pack having a plurality of single cells:
Preparing a plurality of unit cells in which electrode bodies in a form in which sheet-like electrodes are superimposed are housed in a container together with an electrolyte;
Arranging the plurality of single cells in a predetermined direction; and
Restraining the plurality of arranged cells in a state where a load is applied in the arrangement direction;
Including
Here, the restraint is performed in such a manner that a portion restrained by the load larger than the upper side in the vertical direction of the unit cells is provided below the plurality of unit cells.   A vehicle comprising the assembled battery according to any one of claims 1 to 4.

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