NIPPON SOKEN; TOYOTA MOTOR CORP
`
`¥M
`
`y veyWSS
`
`
`AMANO JUNKO; MUKOYAMA MASATO
`Staf-
`AL EASS
`
`
`IPC
`HO1M10/04; HO1M2/18;
`
`CPC
`
`Y02E60/10 (EP);
`Deceyye fac
`
`PHOT es
`
`JP2O142 TGO86A
`ENJA
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`
`
`PROBLEM TO BE SOLVED: Toprovide a battery which can prevent an increase in internal
`resistance of a battery when charging and discharging are repeatedly performed.SOLUTION: A
`battery 10 comprises an elastic spacer 80 whichis arrangedin a flat-plate lamination part 30h of an
`electrode body 30 or arranged outsidethe flat-plate lamination part 30h while overlappingtheflat-
`plate lamination part 30h in a battery case 20. In a compressed constant state wheretheflat-plate
`lamination part 30h and so forth are compressed 1n a lamination direction FH of theflat-plate
`lamination part 30h via the battery case 20 and the dimension in the lamination direction FH of the
`battery case 20 is kept constant, the elastic spacer 80 has a compressiveelasticity modulus Ks and a
`total free thickness Tsa which allows a gap volume Vic ofa first active material layer 43 to be kept
`constant even if the battery 10 1s charged and discharged.
`
`DESCRIPTION
`
`

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`{O001] The present invention relates to a battery including an electrode assembly having 3
`first siectrode plate, a second electrode plate, and a separator, and a batlery case
`accommodating the electrode assembly.
`
`{G002] A battery is conventionally known thal includes an electrode body having a first
`electrode plate (for example, a negative electrode plate), a second electrode plate (for
`example, a positive electrode plate), and a separator, and 4 battery case for housing the
`electrode body. As the electrode body, a first active material layer (far exampie, a negative
`electrode active material layer} of a first electrode plate and a second active material layer
`(far example, 4 posilive electrode active material layer) of a secand electrode plate, such as
`a fiat wound electrode body There is a type having a flat plate laminated partion in which Y
`and Y overlap each other in a flat slate shape via a separator. Furthermore, itis known ta
`use, as the first active material particies (for exarnpis, negative siectrode active material
`particles) constituting the first active material layer, those which expand and contract with
`charge and discharge. For example, Patent Document 1 discloses using, as negative
`electrode active material particies, graphite particies that expand in a charging process and
`coniract in a discharging process.
`
`[0003]RAF 10-645 15 B28
`
`{G004] In the first active material layer containing the first active material particles that
`expand and contract with charge and discharge, the volume of voids cantained in the layer
`(hereinafter also referred to as void volumes) increases or decreases with charge and
`discharge. For example, when the battery case itself has high rigidity in the thickness
`direction of ine first active material layer, or when the battery case is rigidly restrained fram
`ine outside in the thickness direction of the first active material layer, When the battery is
`used whils being restrained, the thickness of the first active material layer can not increase
`or decrease even if charge and discharge are performed (ihe thickness of the first active
`material layer also becomes constant). in this case, when the first active material particles
`expand due to charge or discharge, the void volume in the first active material layer
`decreases accordingly. Then, the electrolyte solution filled in the voids in the first active
`material layer is discharged from the first active material layer as much as the void volume
`decreases. On the other hand, when the first active material particles contract due to
`discharge or charge, the void volume in the first active material layer increases accordingly.
`Then, the electrolyte solution is absorbed into the first active material layer by an amount
`corresponding to the increase of the void volumes. Repeatedly charging and discharging
`such a battery is not preferable because concentration distribution occurs in the electrolytic
`
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`solution as the electrolytic solution held in the first active material layer moves in and out,
`and the internal resistance of the battery increases.
`
`{O008] On the other hand, when using a battery with a constant pressure (or in a free state}
`of the battery, when the first active material particles expand due to charging or discharging,
`the first active material layer expands from the expansion of the first active material
`particles. Also expand greatly. This is because the gap volume is also increased because
`the distance belween adjacent first active material particies is increased. Conversely, when
`the first active material particies contract due to discharge or charge, the first active material
`layer contracts more than the contraction of the first active material particles. This is
`because the volume of the vaid volume is also reduced because the distance befween
`
`adjacentfirst active material particles is reduced. Also in this case, since the electralytic
`solution comes in and out of the first active material layer with charge and discharge of the
`battery, concentration distrioution occurs in the electrolytic sciution, and the internal
`resistance of the battery is increased, which is not preferabie.
`
`{O006] The oresent invention has been made in view of the present situation, and an object
`of the present invention is to provide 4 battery capable of suppressing an increase in
`infernal resistance of the battery when charging and discharging are repeated.
`
`{8007] One aspect of the present invention for solving the above problems is a first
`giectrode foil, and a porous first active material layer formed on the first electrode foil and
`including a first active material particle that expands and contracts with charge and
`discharge. A second slectrode plais having a first electrode plate, a secand siectrode foil,
`and a second active material layer formed thereon, and a separator, wherein the first active
`material layer and the second An electrode body having a flat plate laminated portion in
`which a material layer overlaps with each other in a flat plate shape via the separator, and a
`batlery case accommodating the electrode body, wherein the battery is disposed in the flat
`plate larninated portion or The battery case includes one or a plurality of elastic spacers
`made of an elastic material and disposed outside the flat plate laminated partion so as to
`overlap the flat plate laminated portion, and the elastic spacer includes the flat plate
`laminated portion and the elastic spacer The flat area through the battery case Vvhen the
`battery is charged and discharged under the compression sizing condition in which the
`battery case is compressed in the stacking direction and the dimensions of the battery case
`in the stacking direction are kept constant, the voids of the first active material layeritis a
`battery having a compressive elastic modulus Ks and a free total thickness Tsa in which the
`volume Vic is kept constant.
`
`

`

`{0008] This battery is provided with an elastic spacer which is disposed in the flat plate
`laminate portion of the electrode body or which is disposed outsides tne flat plate laminate
`portion so as to overlap the flat plate laminate portion in the battery case. This elastic
`spacer has a compressive elastic modulus Ks and a free total thickness Tsa such that the
`yoid volume Vic of the first active material layer Gor example, the negative slectrode active
`material layer) can be kept constant even when the battery is charged and discharged in a
`compressed sizing state. Have. For this reason, even if the first active material particles (for
`example, negative electrode active material particles) expand or contract due to charge or
`discharge, the void volume Vic of the first active material layer is kept constant. Therefore,
`in this battery, the void volume Vic of the first active material layer is prevented from
`changing with charge and discharge in the flat plate laminate portion, and the electrolyte
`solution comes in and out of the first active material layer with charge and discharge.
`Absorption) can be suppressed. Therefore, itis possible to suppress an increase in internal
`resistance of the battery when charging and discharging are repeated.
`
`{G008] In addition, as an “slectrode body", the flat-snaped wound-type electrode body and
`laminated-type electrode body which have a flat plate lamination | stacking part are
`mentioned. In addition, in the state that “the cimension in the stacking direction of the
`battery case is kept constant,” tne batiery case itself has a high rigidity not to be deformed
`inthe stacking direction along with charge anc cischarge, or the battery case alang with
`charge and discharges. There is a state in which the battery case is rigidly restrained fram
`the outside in the stacking direction so as not to be deformed in the stacking direction.
`
`{O076] Furthermore, in the above battery, the total thickness of ine first active material layer
`overlapping in the stacking direction in the flat plate stacking portion in the compressed
`sizing state and at SOC O%is Tic, and the compression thickness is determined. The total
`thickness at the time of SOC 100% and the total thickness change ratio At of the first active
`material layer in the compressed fixed size state is Al = (Tid-Tic} / Tic, and the first active
`material layer Among the volumes of the first active material particles per unit area, the
`volume in the compressed sizing state and SOC 0%is Vre, the volume in the compression
`sizing state and SOC 106%is Vrd, and the compression sizing size The volume change
`rate Ev of the first active material particle in the state is By = (rd-Vre} / Vre, and the above-
`mentioned compression dimension state and SOC 0%, the per unit area of the first active
`material layer ist Ife The clastic spacer satisfies At = By x Dc, where an apparent volume
`of the porous layer is Vic, and a THiing rate Dc of the first active material particies in the first
`active material layer is Dc = Vro / Vic. itis preferabie that the battery nas the compressive
`elastic modulus Ks and the free total thickness Tsa.
`
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`

`{O071] The elastic spacer according to this battery has a compressive elastic modulus Ks
`and a ioial free thickness Tsa that satisfy At = By x Da. For this reason, wnen the first active
`material particles expand due to charge or discharge and the thickness of the first active
`material layer increases, the first active material layer is generated by the reaction force
`generated (increased) by the elastic spacer being compressed. An increase in thickness of
`the first active material particle is suppressed only by an increase in the thickness of the first
`active material particle. Therefore, even if the first active material particles expand, the void
`volume Vic of the first active material layer is kept constant.
`
`{0042} On the other hand, when the first active material particies contract due to discharge
`or charge and the thickness of the first active material layer decreases, the thickness of the
`elastic spacerincreases by that amount and the pressing force (reaction force) by the
`elastic spacer decreases. The reduction of the thickness of the first active material layer is
`suppressed (ihe reduction of ihe thickness is stopped only by the contraction of the first
`active maisrial particles}. Therefore, even if the first active material particies shrink, the void
`volume Vic of the first active material layer is kept constant. Therefore, in this battery, the
`yoid volume Vic of the first active material layer is prevented from changing with charge and
`discharge in the flat plate laminate portion, and the electrolyte salution comes in and out of
`the first active material layer with charge and discharge. Absorption) can be suppressed.
`
`{O073] Furthermore, in the above battery, among the total thicknesses of the first active
`material layer, the total thickness af free sfate and af SOC 0%is Tfa, and the total thickness
`at free state and SOC 100%is Tfb, 5OCO Assuming that the compression elastic modulus
`of the first active material layer when K%is Kfa, the elastic spacer is such that Tsa/ Ks =
`(Ev x De x Tic) / (Tfo-Tfa-By x Dc x Tic} x (Tfa ft is preferable that the battery has the
`compressive elastic modulus Ks and the free fofal thickness Tsa which satisfy T_/Kfa}.
`
`{O0714] The clastic spacer according to this battery has a compressive elastic modulus Ks
`and a free total thickness Tsa satisfying the above equation. Such an elastic spacer
`satisfies At = By x Bc. Therefore, as described above, the void volume Vic of the first active
`material layer is constant even if the first active material particles expand or contract with
`charge and discharge. Be kept Therefore, in this battery, the void volume Vic of the first
`active material layer is prevented from changing with charge and discharge in the flat plate
`laminate portion, and the electrolyte solution comes in and out of the first active material
`layer with charge and discharge. Absorption} can be suppressed.
`
`{O0715] Further, another aspectis a first electrode plate including a first slectrode foll and a
`parous first active material layer formed on the first electrode fail and including a first active
`
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`material particie that expands and contracts with charge anc discharge. A second eiectrode
`foil, and a second electrode plate having a second active material layer formed thereon, and
`a separator, wherein the first active material layer and the second active material layer
`intervene through the separator A battery including an electrode assembly having flat plate
`laminations overlapping each other in the form of a fat plate, and a battery case
`accommodating the electrode assembly, wherein the flat plate is disposed in the flat plate
`lamination or is a flat plate in the battery case And a spacer having one or more layers
`which are disposed outside the flat plate laminated partion and nave a thick portion with a
`large thickness and a thin portion thinner than the thick partion; Of the 7 active material
`layer, a portion overlapping with the thick portion in the stacking direction Is a first portion,
`and a portion overlapping the thin portion in the stacking direction is a second portion, and
`of the total thickness of the first portion, the flat portion and the thick portion of the spacer
`are the battery case via the battery case in the compression sizing state in which the battery
`case is compressed in the stacking direction and the dimensions in the stacking direction of
`ihe battery case are kept constant, the total thickness at SOC 0%is Tfc, and the
`compression sizing state is SOC 100%. A total thickness change ratio At of the first partion
`inthe compressed dimension state is represented by At = (Tfid-Ttc) / Tfc, and a total
`thickness of the first active material particles per unit area of the first portion is Tid. Among
`ine volumes, Vre is the volume at SOC 0% when in the compressed dimension state, Vrd is
`ine volume when SOC is 100%when in the compressed dimension state, and the volume
`change rate of the first active material particles in the compressed dimension state. By, By
`The apparent volume of the first portion per unit area of the first portion is Vic in ihe
`compression dimension state and at SOC 0%, where (Vrd-\Vre) / Vre is the first portion in
`the first portion. Assuming thai the filing rate Dc of the active material particles is De = Vre/
`Vic, the thickness portion satisfies Al <By = Dc when the battery is charged and discharged
`under the compression sizing state. Filed, the thin portion does not press the second
`portion, and the area Sa of the first portion and the area Sb of the second portion satisfy
`0.67 $Sa/Sb = 1.5. And a battery.
`
`fO048] This battery is provided with a spacer which is dispased in the flat plate laminated
`partion of the electrade badly or is disposed outside the flat plate laminated portion so as to
`overlap the flat plate laminated portion in the battery case and has a thick portion and @ thin
`partion. in the spacer, when the battery is charged and discharged under the compression
`dimiension state, ihe thick portion satisfies Af <By x Dc, and the thin partion does not press
`ine secand partion, and 0.67 S Sa/ Sb it has a form that satisfies = 1.5.
`
`

`

`{00777 In this battery, it is possible fo suppress an increase or decrease in the void volume
`Vic of the first active material layer due to charge and dischargs when viewed in the entire
`first active material layer in the flat plate laminate portion. That is, when the first active
`material particles expand due to charge or discharge and the thickness of the first active
`material layer increases, the strong portion of the spaceris pressed against the first portion
`of the first active material layer. The force suppresses an increase in thickness at the first
`portion. Since this first portion satisfies At <By x Da, the void volume Vic decreases (4 part
`of the expansion of the first active material particles is covered by the decrease of the void
`volume Vic}, and the electrolyte is discharged. Ru.
`
`{0078] On the other hand, since no reaction force is generated in the thin portion of the
`spacer, an increase in thickness is not suppressed in the second portion of the first active
`material layer. Therefore, at the second portion, the void volume Vic is increased to absorb
`the electrolyte. Thus, as seen in the entire first active material layer in the flat plate laminate
`portion, the decrease in void volume Vic at the first site and the increase in void valume Vic
`at the second site are offset, so the change in void volume Vic is Be suppressed. Therefore,
`in this battery, itis possible to suppress that the electrolytic sclution cames in and out of the
`first active material layer in the flat plate lamination part along with charges and discharge,
`and itis possible to suppress an increase in internal resistance of tne battery when chargs
`and discharge are repeated. .
`
`{O01S] 1 is a perspective view of a battery according to Embodiment 1. FIG It is sectional
`drawing which cut | disconnected the battery which concerns on Embodiment 7 by the plane
`in alignment with batlery horizontal direction CH and battery longitudinal direction DHLIf is
`sectional drawing which cut | disconnected the battery which concerns on Embodiment 7 by
`the plane in alignment with battery thickness direction BH and battery longitudinal direction
`DRJtis sectional drawing which cut | disconnected the battery which concerns on
`Embodiment 7 in the plane in alignment with the battery thickness direction BH and the
`battery horizontal direction CHJt concerns on Embodiment 1, and is a disassembied
`perspective view of 4 caver member, a positive electrade terminal member, a negative
`electrode terminal member, etc. FIG. 3 is a perspective view of an electrode body according
`to Embodiment 1.FiG. 5 is a development view of an electrode assembly according to
`Embodiment 7, snowing a siate in which a pasitive slectrode plats and a negative electrode
`plate are stacked on each other with a separator in between. FIG. 2 is a side view of the
`battery pack according to the first embodimentit is a graph which shows the relationship
`between ine surface pressure concerning a negative electrode active material layer, and the
`total thickness of a negative siecirode active material layer.Jt is sectional drawing which cut
`
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`| disconnected the battery which concerns on Embadiment 2 by the plane in alignment with
`battery thickness direction BH and battery longitudinal direction DH. itis sectional drawing
`which cut | disconnected the battery which concerns on Embodiment 2 in the plane in
`alignment with the battery thickness direction BH and the battery horizontal direction CH Lit
`is a graph which shows the relationship between the cycle number of charging /
`discharging, and the internal resistance of a battery regarding the charging / discharging
`cycle test of each battery concerning Example 1, 2 and a comparative example.
`
`{OO26] Embodiment 1 Hereinafter, an embodiment of the present invention will be described
`with reference to the drawings. 1 to 4 show a battery 10 according to the first embodiment.
`Further, FIG. S shows the lid member 23 of the battery case 20, the positive electrade
`terminal member 60, the negative electrode terminal member 70, and tne like. 6 and 7 show
`the electrode assembly SO and a state in which the electrode assembly 30 is developed.
`Hereinafter, the battery thickness direction BH, the battery lateral direction CH, and the
`battery longitudinal direction DH of the battery 10 wil be described as the directions shown
`in FIGS. 1 to 4. The axial direction EH, the electrode thickness direction (stacking direction)
`FH, and the electrode width direction GH of the electrode assembly 30 will be described as
`the directions shown in FIGS. 2 to 4 and 6 and 7. In FIG. 3, the description of the positive
`electrode terminal member 6O and the like is omitted.
`
`{OO21] The battery 10 is a rectangular and sealed iifhium ion secondary battery mounted on
`a vehicle such as a hybrid car or an electric car. As described later, the battery 10 Is used
`as a battery assembly 100 in which a olurality of batteries 10 are restrained by a restraining
`member 110 (see FiG. &). in FIG. 8, the positive electrade terminal member 60 and the
`negative electrode ferminal member 70 of the battery 10 are amitted. The battery 10
`includes a rectangular battery case 20, a flat wound siectrode body 30 housed in the battery
`case 20, and a positive electrode terminal member 60 and 4 negative electracde terminal
`member 70 supported by the battery case 20. Ht consists of In the battery case 20, a nan-
`aqueous electrolytic solution 27 is neid. Further, in the battery 10, 2 olaic-like elastic spacer
`890 is disposed befweenthe Datiery case 20 and the electrode body 30.
`
`(6022) Among these, the battery case 20 is formed of metal (specifically, aluminum). The
`battery case 20 includes a botiomed rectangular cylindrical case main bady 21 having a
`rectangular opening 27h only on the upper side, and a rectanquiar plate-like lid member 23
`sealing the opening 21h of the case main body 21. (See FIGS. 4 to 4). A non-return type
`safety vaive 23v is provided in the vicinity of the center of the id: member 23 in the
`longitudinal direction (the battery lateral direction CH). In the vicinity of the safety vaive 23v,
`4 liquid injection hole 23h used when infecting the electralytic solution 27 into the battery
`
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`

`case 20 is provided, and the liquid injection hole 23his airtightly sealed by a sealing
`member 28.
`
`{O0023] Further, in the vicinity of Doth ends in the longitudinal direction af the lid member 23,
`4 positive electrode terminal member 60 and a negative electrade terminal member 70
`which extend from the inside to the outside of the battery case 20 are respectively fixedly
`provided (FIG. 1, 2 and 5). Specifically, while the positive electrode terminal member 60 and
`the negative electrode terminal member 7O are connected to the electrode body 30 in the
`battery case 20, respectively, a first terminal extending throuch the lid member 23 to the
`ouiside of the battery case 20 it is comprised from the members 67 and 771 and the crank-
`like 2nd terminal members 62 and 72 which were arrange | positioned on the cover member
`25, and were crimped anc fixed to the ist terminal members 61 and 71. As shown in FIG.
`The positive electrode terminal member 60 and the negative electrade terminal member 70
`are disposed an the inner side (the inner side of the case) of the lid member 23 together
`with metal fastening members 65 and 75 for fastening connection terminals outside the
`battery, such as bus bars and crimp terminals. itis fixed to the idl member23 via the first
`insulating members G7 and 77 made of resin and the secand insulating members 68 and 78
`made of resin disposed on the outer side (the outer side of ine case) of tne lid member 23.
`
`[6024] Nexi, the electrode assembly 30 will be described (see FIGS. 2 to 4 and FIGS. 6 and
`7). in the electrode assembly 30, the axial direction EH coincides with the battery lateral
`direction CH, the electrode thickness direction FH coincides with the battery thickness
`direction BH, and the electrode width direction GH coincides with the battery longitudinal
`direction DH. tis accornmodated in case 20 (refer FIG. 2 and FIG.4). The electrode body 30
`is farmed by laminating a strip-shaped positive electrode plate (second electrode plate) 34
`and 4 sirip-shaped negalive electrode plate (first electrode plate} 41 via 4 pair of sirip-like
`separators 51 and 51 made of porous resin. (Refer to FIG. 7}, If is wound around the axis
`line AX and compressed into a flat shape (refer to FIG. 5).
`
`(6025) The positive slectrade plate 31 has a strip-like positive electrode foil (second
`electrode foil} 32 made of aluminum as a core material. Of the front and back surfaces of
`the positive electrode foil 32, a part in the width direction (vertical direction in FiGS. 6 and 7)
`(a lower part in FIGS. The porous positive electrode active material layers (second active
`material layers} 23 and 35 are formed in a strip shape extending in the left-right direction.
`The positive electrode active material layer 32 is formed of positive electrode active material
`particles, a conductive material, and a binder. In the first embodiment, a lithium-cobait-
`nickel-manganese composite oxide is used as 4 positive slectrode active material,
`
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`

`aceiyiens black (AB) is usec as a conductive material, and polyvinylidene fluoride (PVDF) is
`used as 4 binder.
`
`{O026] The negative electrode plate 41 has a sirip-like negative electracde foil (first electrade
`fail} 42 made of copper as a core material. OF the front and back surfaces of this negative
`electrode foil 42, on @ part (upper part in FIGS. 6 and 7} in the width direction (vertical
`chrection in FIGS. The porous negative electrode active material layers (first active material
`layers) 43 and 43 are formed in a strio shape extending in the left-right direction. The
`negative electrode active material layer 43 is formed of negative electrode active maternal
`particles (first active material particles), a binder and a thickener. in Embodirnent 7, natural
`graphite particles are used as negalive siectrode active material particles, styrene
`bufadiene rubber (SBR) is used as a binder, and carboxymethyl cellulose (CMC) is used as
`a thickener. The negative electrode active material particles expand in the charging process
`and contract in the discharging process, as described tater.
`
`[O027] A portion of the positive electrode plate 37 protrudes in 4 flat spiral form fram the
`separator 51 toward one side EC (upper in FiG. S, upper in FIG. 2 and FiG. 4) in the axial
`direction EH. The positive electrode protruding and winding partion 30c is formed. The first
`terminal member 61 of the pasitive electrode terminal member 60 is connected (welded) to
`the positive electrode protruding and winding partion 30c. In addition, a part of the negative
`electrode plate 41 protrudes in a flat spiral shape from the separator 51 toward the other
`side ED in the axial direction EH (downward in FIG. 6, rightward in FIG. 2 and FIG. 4) Thirty
`negative electrode protruding and wound portions 30d are formed. The first terminal
`member 71 of the negative electrode terminal member 70 is connected (welded) ta the
`negative electrode prajecting wound portion 30 d.
`
`{60287 In the electrode body 30, the positive electrode active material layer 33 and the
`negative electrode active material layer 43 are located on the inner side (center) in the axial
`direction EH with respect to the positive electrode protruding wound portion SOc and the
`negative electrode protruding wound portion 20d. A portion overlapping each otheris
`referred to as a central winding portion 30e (see FIGS. 2, 4, 6 and 7). The central winding
`portion 30e is further divided into a first curved and SOF, a second curved end 30g, and a flat
`plate laminated partion 30h in the electrode body width direction GH (see FIGS. 3 and 6).
`Among them, the one side curved end 30f is located at the end of the one side GA in the
`electrade bady width direction GH, and the positive slectroade active material layer 33, the
`negative electrode active material layer 43 and the separator 57 are bentin a
`semicylindrical shape and overlap each other. itis. The other side curved end 30g is
`located at the end of the other side GB of the electrode body width direction GH, and the
`
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`

`positive electrode active material layer 33, the negative siectrode active material layer 42,
`and the separator 51 are bent in a semicylindrical shape and overlap each other It is.
`
`{O028] The flat slaie lamination portion 30h is located between the one side curved end 30f
`and the other side curved end 30g, and the positive electrode active material layer 33, the
`negative electrode active material layer 43, and the separator 51 have a flat plate shape in
`the electrode body thickness direction Stacking direction) A partion overlapping with FH,
`Specifically, in the flat plate laminated portion 30 h, 30 positive electrode piates 371 and 30
`negative electrodes 47 overlap with each other via the separator 51. Accardingly, 60
`positive electrode active material layers 33 and SO negative electrode active material layers
`43 are stacked in total on ine flat plate laminated partion 30h.
`
`{6036] Next, the elastic spacer 80 will be described (see FIGS. 2 to 4). The elastic spacers
`80 are disposed on both sides of the electrode body 30 in the slectrade body width direction
`GH in the battery case 20. These two (wo-layer) elastic spacers 50 have a rectangular
`plate shape having a slightly larger area (the dimensions in the axial direction EH and the
`electrade body width direction GH are respectively larger) than the flat plate laminated
`portion 30 h of the electrode body 30. It overlaps with the stacked portion 30h and is
`dispased outside the flat stacked portion 30h. The elastic spacer 80 is made of ethylene
`propylene diene rubber (EPDM), and the compressian elastic madulus Ks is Ks = 10.0
`MPa. Further, since the free thickness per elastic spacer 80 is 0.475 mm, the total free
`thickness Tsa is Tsa = 0.475 mm x 2 sheets = 0.950 mm.
`
`(O031] As described above, this battery 10 is used as the battery assembly 100 (see FIG.
`8}. The battery assembly 100 includes a plurality of batteries 10, a plurality of inter-battery
`spacers 130, and a restraint member 110. The plurality of cells 10 are arranged in a row in
`tne cell thickness direction BH (electrode body thickness direction FH), and adjacent cells
`{0 are electrically connected in series by a bus bar (not shown). in addition, the inter-battery
`spacer 130 has a rectangular plate shape, and is disposed between adiacent batteries 10.
`
`{O032] Further, the consiraining member 770 rididly constrains the battery 10 and the inter-
`battery spacer 130 while pressing in the battery thickness direction BH. Note that “restrain
`fo rigid’ means @ state in which a change in dimension in the battery thickness direction BH
`of the battery case 20 accompanying charge and discharge of SOC 0%ta 100%is
`suppressed to G.005 mm or less. The restraint member 110 has a pair of end plates 174,
`four restraint bands 7173, and eight fastening bolfs 175. The end plaie 117 has a rectangular
`plate shape and is dispased on both sides of the cells 10 and the inier-cell spacer 130
`arranged in a row. The restraint Band 113 has a cylindrical shape, is disposed between the
`
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`

`pair of end plates 171, and connects between the end plates 111. The fastening bolt 115 is
`inserted into a through hole (not shown} provided in the end plate 117 to fasten the end 1173
`t of the restraining band 113 to the end plate 117.
`
`{G033] In ihe state in which the battery assembly 100 is configured, the flat plate lamination
`portion 30h of the electrade bady 30 of each batlery 10 and the elastic spacer 80 are
`compressed in ihe lamination direction (electrode body thickness direction) FH via the
`battery case 20, and Even when the negative siectrode active material particies expand and
`coniract by charging and discharging 10, the size af the battery case 20 in the stacking
`direction FH (the battery thickness direction BH) is maintained in a fixed dimension. in the
`first embodiment, a contact pressure of Pc = 1.00 MPa is generated on the flat plate
`laminaied portion 30 h and the elastic spacer 80 in the cormpressed fixed state and at SOC
`0%. On the other hand, in the compressed fixed size state and al 100% SOC, a surface
`pressure of Pd = 3.02 MPa is generated on the flat plate laminated portion 30 fh and the
`@iastic spacer 80. The surface pr