JP2019160587A - Nonaqueous electrolyte secondary battery and battery pack including the same - Google Patents

Abstract

To provide a nonaqueous electrolyte secondary battery having a small change in reaction force due to a change in a charging state and also having a high volume output density, and a battery pack including the same.SOLUTION: A nonaqueous electrolyte secondary battery includes a wound electrode body 3 including a power generation part 3a in which a positive electrode active material mixture layer and a negative electrode active material mixture layer are stacked with a separator interposed therebetween. The power generation part 3a has a flat portion 3b with a flat outer surface. When, as viewed from a direction perpendicular to a first side wall 1b of a rectangular exterior body 1, in an internal space of a battery case configured from the rectangular exterior body 1 and a sealing plate 2, a space in an area that overlaps the flat portion 3b is defined as a flat portion housing space S1, the volume of the flat portion housing space S1 is defined as V1(cm), and the total volume of gaps in the flat portion housing space S1 is defined as V2(cm), V2(cm)/V1(cm) is 0.40-0.42.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a non-aqueous electrolyte secondary battery and an assembled battery using the same.

  As a driving power source for an electric vehicle (EV), a hybrid electric vehicle (HEV, PHEV) or the like, an assembled battery in which a plurality of nonaqueous electrolyte secondary batteries are connected in series or in parallel is used.

  In such an assembled battery, a plurality of nonaqueous electrolyte secondary batteries are arranged so that the wide side surfaces of adjacent nonaqueous electrolyte secondary batteries face each other through an insulating spacer or the like. For example, a plurality of non-aqueous electrolyte secondary batteries are arranged between a pair of end plates, and the pair of end plates are connected by a bind bar to form one assembled battery (Patent Document 1 below).

  In a nonaqueous electrolyte secondary battery, the electrode body expands and contracts due to charge and discharge or the like. When the electrode body expands, the electrode body presses the battery case outward. As a result, if the nonaqueous electrolyte secondary battery expands and the force (reaction force) that presses the other becomes excessively large, members constituting the assembled battery, such as the bind bar and end plate, may be damaged or broken. . In order to prevent damage and breakage of the members constituting the assembled battery, it is conceivable to make the assembled battery a sturdy structure, but there is a problem that the size or weight of the assembled battery increases.

  On the other hand, if the reaction force of the nonaqueous electrolyte secondary battery is excessively small, the nonaqueous electrolyte secondary battery may move in the assembled battery or the electrode body may move in the battery case due to vibration or impact. is there.

Japanese Patent Laying-Open No. 2015-210971

  An object of the present invention is to provide a nonaqueous electrolyte secondary battery having a small volumetric power density and a small change in reaction force due to a change in a charged state, and an assembled battery using the same.

The nonaqueous electrolyte secondary battery according to one aspect of the present invention is
A positive electrode plate having a positive electrode active material mixture layer on the positive electrode core; a negative electrode plate having a negative electrode active material mixture layer on the negative electrode core; and an electrode body including a separator;
A battery case that houses the electrode body,
The battery case includes a rectangular exterior body having an opening, a bottom, a pair of first side walls, and a pair of second side walls, and a sealing plate that seals the opening.
The area of the first side wall is larger than the area of the second side wall,
The electrode body has a power generation unit in which the positive electrode active material mixture layer and the negative electrode active material mixture layer are laminated via the separator,
The power generation unit has a flat portion having a flat outer surface,
When viewed from a direction perpendicular to the first side wall, in the space inside the battery case, a space overlapping the flat part is defined as a flat part accommodating space,
The volume of the flat housing space and V1 (cm ^3),
When the total volume of the voids in the flat portion accommodating space is V2 (cm ³ ),
^{V2 (cm 3) / V1 (} cm 3) is 0.40 to 0.42.

  With the configuration of the nonaqueous electrolyte secondary battery according to one embodiment of the present invention, a nonaqueous electrolyte secondary battery with a small volumetric power density and a small change in reaction force due to a change in charge state is obtained. In addition, by using a non-aqueous electrolyte secondary battery with a small change in reaction force due to a change in the state of charge, damage or breakage of members constituting the assembled battery can be suppressed while suppressing an increase in the size or weight of the assembled battery. Can be prevented. Moreover, it can suppress effectively that a nonaqueous electrolyte secondary battery moves within an assembled battery, or an electrode body moves within a battery case.

  ADVANTAGE OF THE INVENTION According to this invention, the change of the reaction force by the change of a charge state is small, and a nonaqueous electrolyte secondary battery with a high volumetric power density and an assembled battery using the same can be provided.

1 is a perspective view of a nonaqueous electrolyte secondary battery according to an embodiment. 2A is a cross-sectional view taken along the line IIA-IIA in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. It is a perspective view of the assembled battery which concerns on embodiment. It is a top view of the positive electrode plate which concerns on embodiment. It is a top view of the negative electrode plate which concerns on embodiment. It is a top view of the winding electrode body which concerns on embodiment. (A) is sectional drawing along the transversal direction of the sealing plate of the part containing the electric power generation part of a nonaqueous electrolyte secondary battery. (B) is a figure which shows only the square exterior body in (a). (C) is a figure which shows only the electrode body in (a). (D) is a figure which shows only the resin sheet in (a). It is a side view of the sample for reaction force measurement.

  First, the nonaqueous electrolyte secondary battery 20 according to the embodiment will be described. The nonaqueous electrolyte secondary battery 20 according to the embodiment is a prismatic secondary battery. In addition, this invention is not limited to the following forms. FIG. 1 is a perspective view of a non-aqueous electrolyte secondary battery 20. 2A is a cross-sectional view taken along the line IIA-IIA in FIG. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. The nonaqueous electrolyte secondary battery 20 includes a battery case 80 including a bottomed rectangular cylindrical prismatic outer body 1 having an opening and a sealing plate 2 that seals the opening of the rectangular outer body 1. The rectangular exterior body 1 has a bottom 1a, a pair of first side walls 1b, and a pair of second side walls 1c. The pair of first side walls 1b are arranged to face each other. The pair of second side walls 1c are arranged so as to face each other. The area of the first side wall 1b is larger than the area of the second side wall 1c. The rectangular exterior body 1 and the sealing plate 2 are preferably made of metal, and more preferably made of aluminum or aluminum alloy.

In the battery case 80, a flat wound electrode body 3 is disposed in which a belt-like positive electrode plate 40 and a belt-like negative electrode plate 50 are wound through a belt-like separator. The wound electrode body 3 is disposed in the battery case 80 in such a direction that its winding axis is parallel to the bottom portion 1 a of the rectangular exterior body 1. In the wound electrode body 3, the wound positive electrode core exposed portion 4 is provided at one end in the direction in which the winding shaft extends, and the wound negative electrode core exposed portion 5 is provided at the other end. Is provided. The wound electrode body 3 has a pair of flat outer surfaces and a pair of curved outer surfaces that connect the pair of flat outer surfaces. The pair of flat outer surfaces are arranged so as to face the first side wall 1b, respectively. Moreover, the wound positive electrode core exposed portion 4 and the wound negative electrode core exposed portion 5 are arranged so as to face the second side wall 1c, respectively. An electrically insulating resin sheet 14 is disposed between the rectangular exterior body 1 and the wound electrode body 3.

  A positive electrode current collector 6 is connected to the outer surface of the wound positive electrode core exposed portion 4. A metal positive electrode terminal 7 is attached to the sealing plate 2. The positive electrode current collector 6 is electrically connected to the positive electrode terminal 7. Between the positive electrode terminal 7 and the sealing plate 2, a resin-made external insulating member 10 is disposed. Between the positive electrode current collector 6 and the sealing plate 2, a resin-made inner insulating member 11 is disposed.

  A negative electrode current collector 8 is connected to the outer surface of the wound negative electrode core exposed portion 5. A metal negative electrode terminal 9 is attached to the sealing plate 2. The negative electrode current collector 8 is electrically connected to the negative electrode terminal 9. Between the negative electrode terminal 9 and the sealing plate 2, a resin-made external insulating member 12 is disposed. Between the negative electrode current collector 8 and the sealing plate 2, a resin-made inner insulating member 13 is disposed.

  The positive electrode current collector 6 includes a connecting portion 6a connected to the positive electrode core exposed portion 4, a base portion 6c disposed between the sealing plate 2 and the wound electrode body 3, and a wound electrode body from the base portion 6c. 3 has a lead portion 6b that extends to 3 and connects the base portion 6c and the connecting portion 6a. The positive electrode current collector 6 is made of metal, and is preferably made of aluminum or aluminum alloy.

  The negative electrode current collector 8 includes a connecting portion 8a connected to the negative electrode core exposed portion 5, a base portion 8c disposed between the sealing plate 2 and the wound electrode body 3, and a wound electrode body from the base portion 8c. 3 has a lead portion 8b that extends to 3 and connects the base portion 8c and the connecting portion 8a. The negative electrode current collector 8 is made of metal, and is preferably made of copper or a copper alloy.

  The sealing plate 2 is provided with a gas discharge valve 15 that breaks when the pressure in the battery case 80 becomes a predetermined value or more and discharges the gas in the battery case 80 to the outside of the battery case 80. The sealing plate 2 is provided with an electrolyte solution injection hole (not shown). The electrolyte injection hole is sealed with a sealing plug 16.

  Next, the assembled battery 100 including the plurality of nonaqueous electrolyte secondary batteries 20 will be described.

  FIG. 3 is a perspective view of the battery pack 100. Ten nonaqueous electrolyte secondary batteries 20 are disposed between the pair of metal end plates 101. The pair of end plates 101 are connected by a metal binding bar 102. The bind bar 102 is fixed to the end plate 101 with bolts 103. In the assembled battery 100, two bind bars 102 are disposed on one side surface, and two bind bars 102 are disposed on the other side surface.

  A resin spacer 60 is disposed between the adjacent nonaqueous electrolyte secondary batteries 20. The nonaqueous electrolyte secondary batteries 20 are arranged in a direction in which the first side walls 1 b face each other with the spacer 60 interposed therebetween. The positive electrode terminal 7 of the nonaqueous electrolyte secondary battery 20 is electrically connected to the negative electrode terminal 9 of the adjacent nonaqueous electrolyte secondary battery 20 by a metal bus bar 104. In the assembled battery 100, each spacer 60 has a structure that presses the first side wall 1 b of the rectangular exterior body 1 of each opposing nonaqueous electrolyte secondary battery 20.

  Next, a method for manufacturing the nonaqueous electrolyte secondary battery 20 will be described.

[Production of positive electrode plate]
LiNi _0.35 Co _0.35 Mn _0.30 O ₂ as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, carbon black as a conductive material, and N-methyl-2- 2 as a dispersion medium Pyrrolidone (NMP) is kneaded so that the mass ratio of positive electrode active material: binder: conductive material is 90.9: 7: 2.1 to prepare a positive electrode active material mixture slurry.

  A positive electrode active material mixture slurry is applied to both surfaces of an aluminum foil having a thickness of 15 μm as a positive electrode core. Thereafter, the positive electrode active material mixture slurry is dried, and NMP in the positive electrode active material mixture slurry is removed. Thereby, a positive electrode active material mixture layer is formed. Thereafter, the positive electrode active material mixture layer is compressed by a compression roller so as to have a predetermined filling density. Then, the positive electrode plate 40 is cut into a predetermined shape.

  Here, the length of the positive electrode plate 40 is 440 cm, and the width of the positive electrode plate 40 is 12.8 cm. Further, in the positive electrode plate 40, the width of the positive electrode active material mixture layer 40b is 11.0 cm.

  FIG. 4 is a plan view of the positive electrode plate 40. The positive electrode plate 40 includes a strip-shaped positive electrode core body 40a and a positive electrode active material mixture layer 40b formed on both surfaces of the positive electrode core body 40a. The positive electrode core body 40a is provided with a positive electrode core body exposed portion 4 in which the positive electrode active material mixture layer 40b is not formed on both surfaces along the longitudinal direction at the end in the width direction.

[Production of negative electrode plate]
Graphite as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, and water, a mass ratio of negative electrode active material: binder: thickener is 98. The mixture is kneaded so as to be 1: 1, and a negative electrode active material mixture slurry is prepared.

  A negative electrode active material mixture slurry is applied to both surfaces of a copper foil having a thickness of 8 μm as a negative electrode core. Thereafter, the negative electrode active material mixture slurry is dried, and water in the negative electrode active material mixture slurry is removed. Thereby, a negative electrode active material mixture layer is formed. Thereafter, the negative electrode active material mixture layer is compressed by a compression roller so as to have a predetermined filling density. Then, the negative electrode plate 50 is cut into a predetermined shape.

  Here, the length of the negative electrode plate 50 is 450 cm, and the width of the negative electrode plate 50 is 13.0 cm. In the negative electrode plate 50, the width of the negative electrode active material mixture layer 50b is 11.5 cm.

  FIG. 5 is a plan view of the negative electrode plate 50. The negative electrode plate 50 includes a strip-shaped negative electrode core 50a and a negative electrode active material mixture layer 50b formed on both surfaces of the negative electrode core 50a. The negative electrode core body 50a is provided with negative electrode core body exposed portions 5 in which the negative electrode active material mixture layers 50b are not formed on both surfaces along the longitudinal direction at both ends in the width direction. The width of one negative electrode core exposed portion 5 is larger than the width of the other negative electrode core exposed portion 5. The negative electrode current collector 8 is connected to the negative electrode core exposed portion 5 having the larger width.

[Production of wound electrode body]
The strip-shaped positive electrode plate 40 and the strip-shaped negative electrode plate 50 produced by the above-described method are wound through a strip-shaped polypropylene / polyethylene / polypropylene three-layer separator and pressed into a flat shape. The obtained flat wound electrode body 3 has a positive electrode core exposed portion 4 wound on one side in the direction in which the winding axis extends, and a negative electrode core exposed portion wound on the other end. 5

[Adjustment of non-aqueous electrolyte]
A mixed solvent is prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio (25 ° C., 1 atm) of 30:30:40. This mixed solvent was added LiPF ₆ as a 1 mol / L. Furthermore, vinylene carbonate (VC) is added so that the addition amount is 0.3% by mass with respect to the total mass of the non-aqueous electrolyte, and the addition amount is 1% by mass with respect to the total mass of the non-aqueous electrolyte. Lithium bisoxalatoborate is added so that

[Attaching parts to the sealing plate]
An external insulating member 10 is disposed on the battery outer surface side around a positive terminal mounting hole (not shown) provided in the sealing plate 2. An inner insulating member 11 and a base portion 6c of the positive electrode current collector 6 are disposed on the battery inner surface side around a positive electrode terminal mounting hole (not shown) provided in the sealing plate 2. Then, the positive electrode terminal 7 is inserted into the through hole of the external insulating member 10, the positive terminal mounting hole, the through hole of the internal insulating member 11, and the through hole of the base portion 6 c of the positive electrode current collector 6 from the outside of the battery, The tip of the positive electrode terminal 7 is caulked on the base portion 6 c of the positive electrode current collector 6. Thereby, the positive electrode terminal 7 and the positive electrode current collector 6 are fixed to the sealing plate 2. Furthermore, it is preferable to weld the positive electrode terminal 7 and the base portion 6c. The negative electrode terminal 9, the external insulating member 12, the sealing plate 2, the internal insulating member 13, and the negative electrode current collector 8 can be fixed in the same manner on the negative electrode side.

[Attaching the current collector to the flat wound electrode body]
The connecting portion 6 a of the positive electrode current collector 6 is welded to the wound positive electrode core exposed portion 4. The connecting portion 8 a of the negative electrode current collector 8 is welded to the wound negative electrode core exposed portion 5.

[Assembly of non-aqueous electrolyte secondary battery]
A flat wound electrode body 3 arranged in a resin sheet 14 bent into a box shape is inserted into the rectangular exterior body 1. Then, the sealing plate 2 and the rectangular exterior body 1 are welded, and the opening of the rectangular exterior body 1 is sealed by the sealing plate 2. Thereafter, a nonaqueous electrolytic solution is injected into the battery case 80 from the electrolytic solution injection hole provided in the sealing plate 2, and the electrolytic solution injection hole is sealed with the sealing plug 16. As a result, the nonaqueous electrolyte secondary battery 20 is obtained. The battery capacity of the nonaqueous electrolyte secondary battery 20 is 8.4 Ah.

[Each region in the flat wound electrode body]
As shown in FIG. 6, in the flat wound electrode body 3, a positive electrode active material mixture layer 40b and a negative electrode active material mixture layer 50b are laminated via a separator at the center in the direction in which the winding axis extends. It has the electric power generation part 3a. The power generation unit 3a has a flat portion 3b having a flat outer surface, a first curved portion 3c having a curved outer surface located on the sealing plate 2 side, and a curved outer surface located on the bottom portion 1a side of the rectangular exterior body 1. It has the 2nd curved part 3d. A boundary between the first bending portion 3 c and the flat portion 3 b is defined as a first boundary portion 25. The first boundary portion 25 extends in the direction in which the winding axis extends. The boundary between the second curved portion 3d and the flat portion 3b is defined as a second boundary portion 26. The second boundary portion 26 extends in the direction in which the winding axis extends. The height of the flat portion 3b (the length in the direction perpendicular to the bottom portion 1a of the rectangular exterior body 1) is defined as H1 (cm). The width of the flat portion 3b (the length in the direction perpendicular to the second side wall 1c of the rectangular exterior body 1) is defined as W1 (cm).

[Volume of flat part storage space]
As shown in FIGS. 7A and 7B, the spirally wound electrode body 3 is flat when viewed from a direction perpendicular to the first side wall 1 b in the space formed inside the battery case 80. A space overlapping the portion 3b is defined as a flat portion storage space S1. And let the volume of flat part storage space S1 be V1 (cm < ³ >).
In the direction perpendicular to the first side wall 1b, the distance between one first side wall 1b and the other first side wall 1b is T1 (cm).
The volume of the flat portion housing space S1 V1 (cm ³⁾ is calculated by H1 (cm) × W1 (cm ) × T1 (cm).

[Total volume of voids in flat part storage space]
Let V2 (cm ³ ) be the total volume of the gaps in the flat portion storage space S1. The total volume V2 (cm ³ ) of the gaps in the flat part storage space S1 is a gap inside the flat part 3b, a gap between the first side wall 1b of the rectangular exterior body 1 and the resin sheet 14 in the flat part storage space S1, and It is the total of the gaps between the resin sheet 14 and the flat portion 3b in the flat portion storage space S1. The resin sheet 14 is not an essential configuration, and the resin sheet 14 may not be used. Further, when a void is present in the resin sheet 14 such as when the porous resin sheet 14 is used, the void in the resin sheet 14 also has a total volume of voids in the flat portion storage space S1 of V2 (cm ³ ). Add.
The space in the flat portion storage space S1 is a volume obtained by adding the volume of the portion occupied by the nonaqueous electrolyte, the volume of the portion occupied by the gas, and the volume of the vacuum portion.

The total volume V2 (cm ³ ) of the voids in the flat portion storage space S1 can be determined as follows.
First, for each of the positive electrode plate 40, the negative electrode plate 50, and the separator constituting the flat spirally wound electrode body 3, the density, volume, and mass of each member, the inside of the flat portion 3b of the flat spirally wound electrode body 3 is determined. The total volume V2x (cm ³ ) of the voids is calculated. In addition, when the flat winding electrode body 3 contains members, such as a winding tape, these are also considered.
Next, from the volume V1 (cm ³ ) of the flat part storage space S1, the volume of the flat part 3b (apparent volume not taking into account the internal gap) and the volume of the resin sheet 14 disposed in the flat part storage space S1 Is drawn, the total volume V2y (cm) of the gap between the rectangular exterior body 1 and the resin sheet 14 in the flat portion storage space S1 and the gap between the resin sheet 14 and the flat portion 3b in the flat portion storage space S1. ³ ) is calculated.
Then, V2x (cm ³ ) and V2y (cm ³ ) are added together to obtain the total volume V2 (cm ³ ) of the voids in the flat portion storage space S1. When the resin sheet 14 is porous, the total volume V2z of the voids in the resin sheet 14 is also included in the total volume V2 (cm ³ ) of the voids in the flat portion storage space S1.

[Nonaqueous electrolyte secondary battery A]
The non-aqueous electrolyte secondary battery having the configuration of the non-aqueous electrolyte secondary battery 20 described above, and the non-aqueous electrolyte secondary battery having the following configuration was designated as non-aqueous electrolyte secondary battery A.
Flat portion housing space S1 is, T1 (cm) = 1.7cm, a H1 (cm) = 4cm, W1 (cm) = 11cm, and the ^{V1 (cm 3) = 74.8cm 3} .
The thickness of the flat part 3b of the wound electrode body 3 was 1.5 cm.
The thickness of the resin sheet 14 was 0.15 mm. In addition, the resin sheet 14 does not have pores.
The total volume of voids in the flat portion housing space S1 V2 (cm ³⁾ was set to 31.0cm ^3.
Therefore, V2 (cm ³ ) / V1 (cm ³ ) = 0.41.

[Nonaqueous electrolyte secondary battery B]
The nonaqueous electrolyte secondary battery having the configuration of the nonaqueous electrolyte secondary battery 20 described above, and the nonaqueous electrolyte secondary battery having the following configuration was designated as a nonaqueous electrolyte secondary battery B.
Flat portion housing space S1 is, T1 (cm) = 1.7cm, H1 (cm) = 3.7cm, a W1 (cm) = ^10.9cm, was ^{V1 (cm 3) = 68.6cm 3} .
The thickness of the flat part 3b of the wound electrode body 3 was 1.5 cm.
The thickness of the resin sheet 14 was 0.15 mm. In addition, the resin sheet 14 does not have pores.
In addition, the total volume V2 (cm ³ ) of the voids in the flat portion storage space S1 was 26.2 cm ³ .
Therefore, V2 (cm ³ ) / V1 (cm ³ ) = 0.38.

  Using the non-aqueous electrolyte secondary battery A and the non-aqueous electrolyte secondary battery B, samples 1 to 6 for measuring reaction force were prepared, and the following tests were performed. The nonaqueous electrolyte secondary battery A and the nonaqueous electrolyte secondary battery B have a width (length in a direction perpendicular to the second side wall 1c) of 14.8 cm and a height (perpendicular to the bottom 1a). The length in the direction perpendicular to the first side wall 1b) was 1.7 cm.

First, a common configuration of samples 1 to 6 will be described with reference to FIG. FIG. 8 is a view of Samples 1 to 6 as viewed from the side.
The first pressing jig 160 is made of a stainless steel plate having a thickness of 1.3 cm. The second pressing jig 161 is made of a stainless steel plate having a thickness of 1.3 cm. The first pressing jig 160 is disposed so that the first pressing jig 160 is in contact with one first side wall 1b of the nonaqueous electrolyte secondary battery 20. The second pressing jig 161 is disposed so that the other first side wall 1b of the nonaqueous electrolyte secondary battery 20 and the second pressing jig 161 are in contact with each other. Then, on the surface of the second pressing jig 161 opposite to the surface on which the nonaqueous electrolyte secondary battery 20 is disposed, a 1.5 cm-thick stainless steel intermediate plate 171 and a load cell 172 (models manufactured by Minebea Co., Ltd.) A base plate 170 made of stainless steel having a thickness of 1.9 cm is arranged via CMP1-2T). Then, bolts 173 are inserted into through holes provided at four corners of each of the first pressing jig 160, the second pressing jig 161, and the base plate 170, and the members are fixed together by the nut 174.

Samples 1 to 6 were produced as follows.
[Sample 1]
Nonaqueous electrolyte secondary battery A was used as nonaqueous electrolyte secondary battery 20. Further, the interval (constraint thickness) between the first pressing jig 160 and the second pressing jig 161 was fixed to 17.7 cm.
[Sample 2]
Nonaqueous electrolyte secondary battery A was used as nonaqueous electrolyte secondary battery 20. Further, the distance (constraint thickness) between the first pressing jig 160 and the second pressing jig 161 was fixed to 17.5 cm.
[Sample 3]
Nonaqueous electrolyte secondary battery A was used as nonaqueous electrolyte secondary battery 20. Further, the distance (constraint thickness) between the first pressing jig 160 and the second pressing jig 161 was fixed to 17.3 cm.
[Sample 4]
Nonaqueous electrolyte secondary battery B was used as nonaqueous electrolyte secondary battery 20. Further, the interval (constraint thickness) between the first pressing jig 160 and the second pressing jig 161 was fixed to 17.7 cm.
[Sample 5]
Nonaqueous electrolyte secondary battery B was used as nonaqueous electrolyte secondary battery 20. Further, the distance (constraint thickness) between the first pressing jig 160 and the second pressing jig 161 was fixed to 17.5 cm.
[Sample 6]
Nonaqueous electrolyte secondary battery B was used as nonaqueous electrolyte secondary battery 20. Further, the distance (constraint thickness) between the first pressing jig 160 and the second pressing jig 161 was fixed to 17.3 cm.

  For samples 1 to 6, the load applied to the load cell 172 when the nonaqueous electrolyte secondary battery has a charge depth (SOC) of 0% and the nonaqueous electrolyte secondary battery has a charge depth (SOC) of 100%. Measured and used as the reaction force of each sample. The reaction force of each sample is shown in Table 1.

  As shown in Table 1, when samples having the same constrained thickness are compared, samples 1 to 3 using the nonaqueous electrolyte secondary battery A having V2 / V1 of 0.41 have V2 / V1 of 0.38. The difference between the reaction force when the SOC is 100% and the reaction force when the SOC is 0% is smaller than that of the samples 4 to 6 using the nonaqueous electrolyte secondary battery B.

  Thus, by setting V2 / V1 to 0.40 to 0.42, the change in the reaction force due to the change in the state of charge can be kept small. In addition, it becomes a nonaqueous electrolyte secondary battery with a high volumetric power density by setting V2 / V1 to 0.42 or less.

  As shown in Table 2, the difference between the maximum reaction force and the minimum reaction force in the sample using the non-aqueous electrolyte secondary battery A is 2368 N, and the maximum reaction force in the sample using the non-aqueous electrolyte secondary battery B is It is smaller than 3045N which is the difference between the force and the minimum reaction force. Thus, when V2 / V1 is 0.40 to 0.42, the change in the reaction force due to the change in the restrained state and the charged state of the nonaqueous electrolyte secondary battery can be further reduced.

  In the state where the nonaqueous electrolyte secondary battery is constrained by the thickness of the nonaqueous electrolyte secondary battery, the difference between the reaction force (N) when the SOC is 100% and the reaction force (N) when the SOC is 0% Is preferably 1200 N or less, more preferably 800 N to 1200 N.

  The total volume of voids inside the flat portion 3b of the flat wound electrode body 3 is the amount of voids in the positive electrode active material mixture layer, the amount of voids in the negative electrode active material mixture layer, and the amount of voids in the separator. Etc. can be controlled by changing them.

The porosity of the positive electrode active material mixture layer is preferably 35% to 39%. If the positive electrode active material is a lithium transition metal composite oxide, the amount of the formed positive electrode active material mixture layer formed on one surface of the positive electrode substrate is preferably 120g ^/ m ² ~180g / m 2 . Further, it is preferable that the filling density of the positive electrode active material mixture layer is ^{2.5g / cm 3 ~2.7g / cm 3} . The ratio of the total thickness of the positive electrode active material mixture layers formed on both surfaces of the positive electrode core to the thickness of the positive electrode plate is preferably 75% to 85%. The thickness of the positive electrode plate is preferably 66 μm to 76 μm, more preferably 68 μm to 74 μm, and further preferably 70 μm to 72 μm. The number of stacked positive plates in the flat wound electrode body 3 is preferably 72 to 90 layers, more preferably 74 to 88 layers, and still more preferably 76 to 86 layers. .

The porosity of the negative electrode active material mixture layer is preferably 50% to 54%. If the anode active material is a carbon material, formation of the negative electrode active material mixture layer formed on one surface of the negative electrode substrate is preferably ^{60g / m 2 ~100g / m 2} . Further, it is preferable that the filling density of the negative electrode active material mixture layer is ^{1.0g / cm 3 ~1.2g / cm 3} . The ratio of the total thickness of the negative electrode active material mixture layers formed on both surfaces of the negative electrode core to the thickness of the negative electrode plate is preferably 85% to 95%. The thickness of the negative electrode plate is preferably 71 μm to 81 μm, more preferably 73 μm to 79 μm, and even more preferably 75 μm to 77 μm.

  The thickness of the separator is preferably 14 μm to 26 μm, more preferably 15 μm to 25 μm, and still more preferably 16 μm to 24 μm.

  The ratio of the thickness of the flat portion 3b to the distance between the pair of first side walls 1b of the rectangular exterior body 1 is preferably 92% to 96%.

[Others]
As materials such as a positive electrode plate, a negative electrode plate, a non-aqueous electrolyte, and a separator, known materials used for lithium ion secondary batteries can be used.

  As the positive electrode active material, it is preferable to use a lithium transition metal composite oxide. Examples of the lithium transition metal composite oxide include lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel manganese composite oxide, lithium nickel cobalt composite oxide, and lithium nickel cobalt manganese composite oxide. Moreover, what added Al, Ti, Zr, W, Nb, B, Mg, Mo, etc. to said lithium transition metal complex oxide can also be used.

  As the negative electrode active material, a carbon material capable of inserting and extracting lithium ions is preferably used. Examples of the carbon material capable of occluding and releasing lithium ions include graphite, non-graphitizable carbon, graphitizable carbon, fibrous carbon, coke, and carbon black. Of these, graphite is particularly preferable. Furthermore, examples of the non-carbon material include silicon, tin, and alloys and oxides mainly containing them.

  As the nonaqueous solvent (organic solvent) of the nonaqueous electrolyte, carbonates, lactones, ethers, ketones, esters and the like can be used, and two or more of these solvents can be used in combination. it can. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate can be used. In particular, it is preferable to use a mixed solvent of a cyclic carbonate and a chain carbonate. Moreover, unsaturated cyclic carbonates such as vinylene carbonate (VC) can also be added to the nonaqueous electrolyte.

As the electrolyte salt of the non-aqueous electrolyte, those generally used as the electrolyte salt in the conventional lithium ion secondary battery can be used. For example, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiAsF ₆ , LiClO ₄ , Li ₂ B ₁₀ Cl ₁₀ , Li ₂ B ₁₂ Cl ₁₂ , LiB (C ₂ O ₄ ) ₂ , LiB ( C ₂ O ₄ ) F ₂ , LiP (C ₂ O ₄ ) ₃ , LiP (C ₂ O ₄ ) ₂ F ₂ , LiP (C ₂ O ₄ ) F _{4 and the} like and mixtures thereof are used. Among these, LiPF ₆ is particularly preferable. The amount of electrolyte salt dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / L.

  As the separator, a resin porous film is preferably used. For example, it is preferable to use a porous film made of polyolefin. As the polyolefin, polypropylene (PP), polyethylene (PE) and the like are particularly preferable. A separator having a three-layer structure (PP / PE / PP or PE / PP / PE) of polypropylene (PP) and polyethylene (PE) can also be used.

Filling density of the positive electrode active material mixture layer ^is preferably ^{1.5g / cm 3 ~4.0g / cm 3} , more preferably ^{2.0g / cm 3 ~3.0g / cm 3} . The packing density of the negative electrode active material mixture layer ^is preferably ^{0.5g / cm 3 ~2.5g / cm 3} , more preferably ^{0.8g / cm 3 ~1.8g / cm 3} .

  A porous protective layer made of ceramic particles and a binder may be provided on at least one of the positive electrode active material mixture layer surface, the negative electrode active material mixture layer surface, and the separator surface.

  The electrode body is not limited to a wound electrode body. A laminated electrode body including a plurality of positive plates and a plurality of negative plates may be used. However, if the wound electrode body has a wound positive electrode core exposed portion and a wound negative electrode core exposed portion, a non-aqueous electrolyte secondary battery with more excellent output characteristics is obtained.

20 ... Non-aqueous electrolyte secondary battery 80 ... Battery case 1 ... Rectangular outer casing 1a ... Bottom 1b ... First side wall 1c ... Second side wall 2 ... Sealing plate 3 .... Winding electrode body 3a ... Power generation part 3b ... Flat part 3c ... First bending part 3d ... Second bending part 25 ... First boundary part 26 ... Second boundary part DESCRIPTION OF SYMBOLS 40 ... Positive electrode plate 40a ... Positive electrode core body 40b ... Positive electrode active material compound layer 4 ... Positive electrode core body exposed part 50 ... Negative electrode plate 50a ... Negative electrode core body 50b ... Negative electrode Active material mixture layer 5 ... negative electrode core exposed portion 6 ... positive electrode current collector 6a ... connection portion 6b ... lead portion 6c ... base portion 7 ... positive electrode terminal 8 ... Negative electrode current collector 8a ... connection part 8b ... lead part 8c ... base part 9 ... negative electrode terminal 10 ... external insulating member 11 ... internal insulating member 1 ... External insulating member 13 ... Internal insulating member 14 ... Resin sheet 15 ... Gas discharge valve 16 ... Sealing plug 100 ... Battery battery 101 ... End plate 102 ...・ Bind bar 103 ... Bolt 104 ... Bus bar 60 ... Spacer

160 ... first pressing jig 161 ... second pressing jig 170 ... base plate 171 ... intermediate plate 172 ... load cell 173 ... bolt 174 ... nut

Claims (5)

A positive electrode plate having a positive electrode active material mixture layer on the positive electrode core; a negative electrode plate having a negative electrode active material mixture layer on the negative electrode core; and an electrode body including a separator;
A battery case that houses the electrode body,
The battery case includes a rectangular exterior body having an opening, a bottom, a pair of first side walls, and a pair of second side walls, and a sealing plate that seals the opening.
The area of the first side wall is larger than the area of the second side wall,
The electrode body has a power generation unit in which the positive electrode active material mixture layer and the negative electrode active material mixture layer are laminated via the separator,
The power generation unit has a flat portion having a flat outer surface,
When viewed from a direction perpendicular to the first side wall, in the space inside the battery case, a space overlapping the flat part is defined as a flat part accommodating space,
The volume of the flat portion accommodating space is V1 (cm ³ ),
When the total volume of the voids in the flat portion accommodating space is V2 (cm ³ ),
A nonaqueous electrolyte secondary battery in which V2 (cm ³ ) / V1 (cm ³ ) is 0.40 to 0.42. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a ratio of a total volume (cm ³ ) of voids in the flat portion to a volume (cm ³ ) of the flat portion is 0.42 to 0.46. The electrode body is a flat wound electrode body in which the belt-like positive electrode plate and the belt-like negative electrode plate are wound through the belt-like separator,
The wound electrode body includes a wound positive electrode core exposed portion disposed on one side of the pair of second side walls and a wound negative electrode core disposed on the other side of the pair of second side walls. A body exposed portion,
A positive electrode current collector is connected to the positive electrode core exposed portion,
A negative electrode current collector is connected to the negative electrode core exposed portion,
The power generation unit has a curved outer surface and a first curved portion located on the sealing plate side of the flat portion, and a second curved portion having a curved outer surface and located on the bottom side of the flat portion. The nonaqueous electrolyte secondary battery according to claim 1, comprising:   When the reaction force is measured by restraining the non-aqueous electrolyte secondary battery with the thickness of the non-aqueous electrolyte secondary battery, the reaction force (N) and non-water at a charging depth of 100% of the non-aqueous electrolyte secondary battery are measured. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein a difference from a reaction force (N) at a charging depth of 0% of the electrolyte secondary battery is 800N to 1200N. An assembled battery including a plurality of the nonaqueous electrolyte secondary batteries according to claim 1,
A battery pack in which a plurality of the nonaqueous electrolyte secondary batteries are stacked between a pair of end plates.

Images