JP5267873B2 - Secondary battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a secondary battery. In detail, it is related with the structure of the secondary battery provided with the flat wound electrode body.

  In recent years, lithium-ion batteries, nickel-metal hydride batteries, and other secondary batteries have become increasingly important as power sources for vehicles or as power sources for personal computers and portable terminals. In particular, a lithium ion battery that is lightweight and has a high energy density is expected to be preferably used as a high-capacity power supply for mounting on a vehicle. As a typical example of such a high-capacity lithium ion battery, there is a battery including an electrode body (winding electrode body) having a spiral structure. That is, the positive electrode sheet and the negative electrode sheet are arranged so as to face each other with the separator sheet interposed therebetween, and the reaction area of the positive electrode and the negative electrode can be increased by further winding the positive electrode sheet and the negative electrode sheet in a spiral shape. To increase the capacity.

This type of lithium ion battery includes a positive electrode having a configuration in which a positive electrode active material capable of reversibly occluding and releasing Li ions is held on a positive electrode current collector. Examples of positive electrode active materials used for such positive electrodes include lithium and transition metal elements such as lithium nickelate (LiNiO ₂ ), lithium cobaltate (LiCoO ₂ ), and lithium manganate (LiMn ₂ O ₄ ). Examples thereof include a positive electrode active material mainly containing an oxide (lithium transition metal oxide) containing as an element. Moreover, as a positive electrode electrical power collector used for a positive electrode, the sheet-like or foil-shaped member which has aluminum or aluminum alloy as a main component is mentioned.

JP 2000-021452 A

  By the way, in the above-described wound electrode body, a battery may be housed in a rectangular battery case (typically a flat box case). In such a case, the wound electrode body formed in a flat shape is inserted into the rectangular battery case. For example, Patent Document 1 is disclosed as a secondary battery having a flat wound electrode body accommodated in this type of rectangular battery case.

  However, in the secondary battery having the conventional flat wound electrode body, the curvature around the innermost circumference of the wound R portion is too large (because the radius of curvature is too small), so the positive electrode sheet is wound in a flat shape. In some cases, the positive electrode active material layer in the vicinity of the innermost periphery of the wound R portion was cracked, and the positive electrode active material layer was sometimes peeled off from the positive electrode current collector. In the secondary battery having the above-described conventional flat wound electrode body, when the positive electrode active material in the positive electrode active material layer repeatedly expands and contracts along with charge and discharge, the innermost circumference of the wound R portion having a high curvature is obtained. Since stress was applied in the vicinity, the positive electrode active material layer was cracked, and the positive electrode active material layer was sometimes peeled off from the positive electrode current collector. When the positive electrode active material layer is peeled off from the positive electrode current collector as described above, a short circuit occurs inside the battery and the output performance is degraded due to current concentration, so that the charge / discharge cycle characteristics are significantly degraded.

  This invention is made | formed in view of this point, The main objective is to provide a secondary battery with favorable charging / discharging cycling characteristics. Another object of the present invention is to provide a method for manufacturing a secondary battery having such characteristics stably (with high quality stability).

  One secondary battery provided by the present invention includes a positive electrode sheet in which a positive electrode active material layer is provided on both sides of a positive electrode current collector, and a negative electrode sheet in which a negative electrode active material layer is provided on both sides of the negative electrode current collector. Is a battery provided with an electrode body (flat wound electrode body) that is wound around a separator sheet and has a flat outer shape. The separator sheet has a separator sheet extra length wound inside from the innermost peripheral portion of the positive electrode sheet. The separator sheet surplus length portion is disposed so as to wind at least two rounds inside the innermost peripheral portion of the positive electrode sheet.

  According to the configuration of the present invention, since the separator sheet surplus length portion is wound two or more times inside the innermost peripheral portion of the positive electrode sheet, the thickness of the innermost peripheral portion of the flat wound electrode body increases. The curvature of the positive electrode sheet in the vicinity of the innermost circumference of the winding R portion becomes small. Therefore, stress applied to the positive electrode sheet during charge / discharge is alleviated, and peeling of the positive electrode active material layer can be suppressed. As a result, it is possible to prevent a short circuit inside the battery and to prevent a decrease in output characteristics due to current concentration, so that a highly reliable secondary battery excellent in charge / discharge cycle characteristics can be obtained.

  In a preferred aspect of the secondary battery disclosed herein, the negative electrode sheet has a negative electrode sheet extra length wound inside the innermost peripheral portion of the positive electrode sheet. The negative electrode sheet surplus length part is provided with the negative electrode active material layer on both surfaces of the negative electrode current collector until the winding start end, and at least one turn inside the innermost peripheral part of the positive electrode sheet. Are arranged to be. According to such a configuration, the negative electrode active material layer is wound on the both sides up to the winding start end because the thick negative electrode sheet extra length is wound more than one turn inside the innermost peripheral part of the positive electrode sheet. The curvature of the positive electrode sheet near the innermost periphery of the wound R portion becomes smaller. Therefore, the stress applied to the positive electrode sheet during charge / discharge is further reduced, and peeling of the positive electrode active material layer can be more reliably suppressed.

  According to the present invention, the positive electrode sheet in which the positive electrode active material layer is provided on both sides of the positive electrode current collector and the negative electrode sheet in which the negative electrode active material layer is provided on both sides of the negative electrode current collector are interposed via the separator sheet. A battery is provided that is an electrode body that is wound and has an electrode body (flat wound electrode body) that exhibits a flat outer shape. The negative electrode sheet surplus length part is provided with the negative electrode active material layer on both surfaces of the negative electrode current collector until the winding start end, and at least one turn inside the innermost peripheral part of the positive electrode sheet. Are arranged to be. According to such a configuration, the negative electrode active material layer is wound on the both sides up to the winding start end because the thick negative electrode sheet extra length is wound more than one turn inside the innermost peripheral part of the positive electrode sheet. The thickness of the innermost peripheral portion of the flat wound electrode body is increased, and the curvature of the positive electrode sheet near the innermost periphery of the wound R portion is decreased. Therefore, stress applied to the positive electrode sheet during charge / discharge is alleviated, and peeling of the positive electrode active material layer can be suppressed. As a result, a highly reliable secondary battery having excellent charge / discharge cycle characteristics can be obtained. In a preferable aspect, the separator sheet has a separator sheet extra length portion wound inward from the innermost peripheral portion of the positive electrode sheet. According to this aspect, since the separator extra length part is wound inside the innermost peripheral part of the positive electrode sheet, the curvature of the positive electrode sheet near the innermost periphery of the wound R part becomes smaller. Therefore, the stress applied to the positive electrode sheet during charge / discharge is further reduced, and peeling of the positive electrode active material layer can be more reliably suppressed. The separator sheet surplus portion is preferably arranged so as to wind at least one round inside the innermost circumferential portion of the positive electrode sheet, and is arranged so as to wind at least two rounds. More preferred.

  In a preferable aspect of the secondary battery disclosed herein, the flat wound electrode body includes two opposed wound flat portions, and two wound R portions that connect ends of the two flat portions. It is composed of In the positive electrode sheet, the positive electrode active material layer is provided on both surfaces of the positive electrode current collector to the winding start end, and the winding start end is disposed on one of the winding flat portions. If the winding start end of the positive electrode sheet is arranged in the winding R portion having a high curvature, the positive electrode active material layer is easily peeled off due to stress applied during charging and discharging. According to the above configuration, the curvature of the winding start end of the positive electrode sheet is Since there is no winding flat part, peeling of the positive electrode active material layer can be suppressed.

  Moreover, according to this invention, the method of manufacturing the secondary battery which has the said flat wound electrode body is provided. That is, a positive electrode sheet having a positive electrode active material layer provided on both sides of a positive electrode current collector and a negative electrode sheet having a negative electrode active material layer provided on both sides of the negative electrode current collector are wound through a separator sheet. It is an electrode body and a manufacturing method of a battery provided with the electrode body which exhibits a flat external shape. The method includes a step of laminating a positive electrode sheet and a negative electrode sheet via a separator sheet and winding in a cylindrical shape, and a step of crushing the cylindrical wound body in a radial direction to obtain a flat wound electrode body Is included. In the winding step, the separator sheet is wound two or more times inside the innermost peripheral portion of the wound positive electrode sheet.

  According to the method of the present invention, the separator sheet is wound two or more times inside the innermost peripheral portion of the positive electrode sheet, and then the wound body is crushed. Less stress on the seat. Therefore, the wound body can be crushed while suppressing peeling of the positive electrode active material layer. Therefore, according to the present invention, a highly reliable secondary battery having excellent discharge cycle characteristics can be manufactured stably (with high quality stability).

  In a preferable aspect of the secondary battery manufacturing method disclosed herein, the negative electrode sheet is provided with the negative electrode active material layer on both surfaces of the negative electrode current collector to the winding start end. Here, in the winding step, the negative electrode sheet is wound one or more times inside the innermost peripheral portion of the wound positive electrode sheet. According to this method, since the wound body is crushed after winding the negative electrode sheet one or more times inside the innermost peripheral portion of the positive electrode sheet, the stress applied to the positive electrode sheet during crushing is reduced. Therefore, the wound body can be crushed while more reliably suppressing the peeling of the positive electrode active material layer.

  In a preferred aspect of the secondary battery manufacturing method disclosed herein, the flat wound electrode body has two wound flat portions facing each other and two windings R connecting the ends of the two flat portions. It consists of a part. In the positive electrode sheet, the positive electrode active material layer is provided on both surfaces of the positive electrode current collector until the winding start end. Here, in the crushing step, the wound body is crushed so that the winding start end of the positive electrode sheet is disposed in one of the winding flat portions. According to such a method, since the wound body is crushed so that the winding start end of the positive electrode sheet is disposed on the wound flat portion, the stress applied to the positive electrode sheet during crushing is reduced. Therefore, the wound body can be crushed while more reliably suppressing the peeling of the positive electrode active material layer.

  Such a secondary battery (for example, a lithium ion secondary battery) exhibits favorable battery performance as described above, and thus is suitable as a secondary battery mounted on a vehicle such as an automobile. Therefore, according to the present invention, there is provided a vehicle including any of the secondary batteries disclosed herein (which may be in the form of an assembled battery in which a plurality of batteries are connected). In particular, since good load characteristics can be obtained, a vehicle (for example, an automobile) including the secondary battery as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is provided.

1 is a perspective view schematically showing a secondary battery according to an embodiment of the present invention. It is sectional drawing which shows the II-II cross section of FIG. 1 typically. It is a figure for demonstrating the flat wound electrode body which concerns on one Embodiment of this invention. It is sectional drawing of the flat wound electrode body which concerns on one Embodiment of this invention. It is principal part sectional drawing of the flat wound electrode body which concerns on one Embodiment of this invention. 1 is a side view showing a vehicle including a secondary battery according to an embodiment of the present invention.

  Several preferred embodiments of the present invention will be described with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. Hereinafter, the structure of the battery of the present invention will be described in detail by taking the prismatic lithium ion secondary battery 100 as an example, but the present invention is not intended to be limited to the one described in the embodiment. Further, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect actual dimensional relationships.

  Although it is not intended to be particularly limited, in the following, a flatly wound electrode body (wound electrode body) and a nonaqueous electrolyte solution are accommodated in a flat box-shaped (cuboid shape) container. The present invention will be described in detail by taking a lithium secondary battery (lithium ion battery) as an example.

  A schematic configuration of a lithium ion battery according to an embodiment of the present invention is shown in FIGS. The lithium ion battery 100 includes a flat electrode body (flat wound electrode body) in which a long positive electrode sheet 10 and a long negative electrode sheet 20 are wound through long separators 30A and 30B. 80 has the structure accommodated in the container 50 of the shape (flat box shape) which can accommodate this winding electrode body 80 with the nonaqueous electrolyte solution which is not shown in figure.

  The container 50 includes a flat rectangular parallelepiped container body 52 having an open upper end, and a lid body 54 that closes the opening. As a material constituting the container 50, a metal material such as aluminum or steel is preferably used (in this embodiment, aluminum). Or the container 50 formed by shape | molding resin materials, such as PPS and a polyimide resin, may be sufficient. On the upper surface of the container 50 (that is, the lid 54), a positive electrode terminal 70 that is electrically connected to the positive electrode 10 of the wound electrode body 80 and a negative electrode terminal 72 that is electrically connected to the negative electrode 20 of the electrode body 80 are provided. ing. Inside the container 50, a flat wound electrode body 80 is accommodated together with a non-aqueous electrolyte solution (not shown).

  As shown in FIG. 3, the flat wound electrode body 80 according to the present embodiment has a long (strip-shaped) sheet structure at a stage before assembling the wound electrode body 80.

  The positive electrode sheet 10 has a structure in which a positive electrode active material layer 14 containing a positive electrode active material is held on both surfaces of a long sheet-like foil-shaped positive electrode current collector 12. However, the positive electrode active material layer 14 is not attached to one side edge (the lower side edge portion in FIG. 3) along the edge in the width direction of the positive electrode sheet 10, and the positive electrode current collector 12 has a constant width. The exposed portion of the positive electrode active material layer is not formed.

  Similarly to the positive electrode sheet 10, the negative electrode sheet 20 has a structure in which a negative electrode active material layer 24 containing a negative electrode active material is held on both surfaces of a long sheet-like foil-shaped negative electrode current collector 22. However, the negative electrode active material layer 24 is not attached to one side edge (upper side edge portion in FIG. 3) along the edge in the width direction of the negative electrode sheet 20, and the negative electrode current collector 22 has a constant width. An exposed negative electrode active material layer non-forming portion is formed.

  When producing the flat wound electrode body 80, the positive electrode sheet 10 and the negative electrode sheet 20 are laminated via the separator sheets 30A and 30B. At this time, the positive electrode sheet 10 and the negative electrode sheet so that the positive electrode active material layer non-formation part of the positive electrode sheet 10 and the negative electrode active material layer non-formation part of the negative electrode sheet 20 protrude from both sides in the width direction of the separator sheets 30A and 30B, respectively. 20 are overlapped with a slight shift in the width direction. The laminated body thus stacked is wound, and then the obtained wound body is crushed from the side surface direction and ablated, whereby a flat wound electrode body 80 can be produced.

  A wound core portion 82 (that is, the positive electrode active material layer 14 of the positive electrode sheet 10, the negative electrode active material layer 24 of the negative electrode sheet 20, and the separator sheets 30 </ b> A and 30 </ b> B) is formed at the central portion in the winding axis direction of the wound electrode body 80. A densely stacked portion) is formed. Moreover, the electrode composite material layer non-formation part of the positive electrode sheet 10 and the negative electrode sheet 20 protrudes outward from the winding core part 82 at both ends in the winding axis direction of the wound electrode body 80, respectively. A positive electrode lead terminal 74 and a negative electrode lead terminal 76 are respectively provided on the protruding portion 84 (that is, a portion where the positive electrode active material layer 14 is not formed) 84 and the protruding portion 86 (that is, a portion where the negative electrode active material layer 24 is not formed) 86. Attached and electrically connected to the positive terminal 70 and the negative terminal 72 described above.

  Moreover, as shown in FIG. 2, the winding cross-sectional shape of the flat wound electrode body 80 obtained in this way has two wound flat portions 90A and 90B facing each other and ends of the two flat portions. And two winding R portions 92A and 92B that communicate with each other. The flat wound electrode body 80 can be accommodated in the container 50 such that the winding axis direction is the horizontal direction (left-right direction in FIG. 1).

  Subsequently, the flat wound electrode body 80 according to the present embodiment will be described in more detail. FIG. 4 is a diagram schematically showing a wound cross-sectional shape of the flat wound electrode body 80, and FIG. 5 is an enlarged cross-sectional view of a main part of FIG.

  4 and 5, the flat wound electrode body 80 includes a positive electrode sheet 10 having a positive electrode active material layer 14 provided on both surfaces of the positive electrode current collector 12 and a negative electrode active material on both surfaces of the negative electrode current collector 22. The negative electrode sheet 20 on which the material layer 24 is provided is wound in a flat shape via two separator sheets 30A and 30B, and the negative electrode sheet 20 is disposed on the outermost side of the wound outermost side than the positive electrode sheet 10 at the outermost periphery. Arranged to wind.

  The separator sheet 30 </ b> A is disposed between the negative electrode sheet 20 wound around the outer peripheral side and the positive electrode sheet 10 wound around the inner circumference of the negative electrode sheet 20. The separator sheet 30 </ b> A has a separator sheet surplus length portion 38 </ b> A that is wound inside the innermost peripheral portion 16 of the positive electrode sheet 10 in the wound innermost peripheral portion. The separator sheet surplus length portion 38 </ b> A is disposed so as to wind at least two rounds inside the innermost peripheral portion 16 of the positive electrode sheet 10. That is, the separator sheet 30 </ b> A is excessively wound around the innermost peripheral portion of the flat wound electrode body 80 by two or more rounds longer than the positive electrode sheet 10.

  Similarly to the separator sheet 30A, the separator sheet 30B also has a separator sheet surplus portion 38B that is wound inside the innermost peripheral portion 16 of the positive electrode sheet 10 at the wound innermost peripheral portion. The separator sheet surplus length portion 38 </ b> B is disposed so as to wind at least two rounds inside the innermost peripheral portion 16 of the positive electrode sheet 10. In other words, the separator sheet 30 </ b> B is wound around the innermost peripheral portion of the flat wound electrode body 80 longer than the positive electrode sheet 10 by two or more turns.

  As described above, in the battery 100 of the present embodiment, the separator sheet surplus length portions 38A and 38B are wound more than two times inside the innermost peripheral portion 16 of the positive electrode sheet 10, so that the flat wound electrode The thickness of the innermost peripheral portion of the body 80 increases, and the curvature of the positive electrode sheet 10 (16A, 16B) near the innermost periphery of the wound R portions 38A, 38B decreases. Therefore, the stress applied to the positive electrode sheet 10 during charging / discharging is reduced, and peeling of the positive electrode active material layer 14 can be suppressed.

  Moreover, in this embodiment, the negative electrode sheet 20 also has the negative electrode sheet surplus length part 28 wound inside the innermost peripheral part 16 of the positive electrode sheet 10 like the separator sheets 30A and 30B. As shown in FIG. 5, the negative electrode sheet extra length portion 28 is provided with negative electrode active material layers 24 a and 24 b on both surfaces of the negative electrode current collector 22 up to the winding start end 25. That is, the negative electrode sheet extra length portion 28 is not only on the outer surface facing the positive electrode sheet 10 but also on the inner surface not facing the positive electrode sheet 10 (the surface on the side that does not directly contribute to the charge / discharge reaction in terms of battery configuration). A negative electrode active material layer 24b is provided. Thus, by providing the negative electrode active material layers 24 a and 24 b on both surfaces of the negative electrode current collector 22, the thickness of the negative electrode sheet extra length portion 28 is increased. The thick negative electrode sheet surplus portion 28 is disposed so as to wind at least one round inside the innermost peripheral portion 16 of the positive electrode sheet 10. That is, the negative electrode sheet 20 is wound around the innermost circumferential portion of the flat wound electrode body 80 by one or more turns longer than the positive electrode sheet 10.

  According to the above configuration, the thick negative electrode sheet surplus portion 28 in which the negative electrode active material layers 24 a and 24 b are provided on both surfaces up to the winding start end 25 is at least one turn inside the innermost peripheral portion 16 of the positive electrode sheet 10. Since it is wound, the curvature of the positive electrode sheet 10 in the vicinity of the innermost circumference of the wound R portions 38A and 38B becomes smaller. Therefore, the stress applied to the positive electrode sheet 10 at the time of charging / discharging is further reduced, and peeling of the positive electrode active material layer 14 can be more reliably suppressed. That is, according to the present embodiment, since the curvature of the positive electrode sheet 10 (16A, 16B) near the innermost circumference of the wound R portions 38A, 38B is reduced, the stress applied to the positive electrode sheet 10 during charge / discharge is reduced, The peeling of the positive electrode active material layer 14 can be suppressed. As a result, a minute short circuit inside the battery can be prevented, and the output characteristics are not deteriorated due to current concentration. Therefore, the highly reliable secondary battery 100 having excellent charge / discharge cycle characteristics can be provided.

  In addition, what is necessary is just to adjust suitably the frequency | count of circumference | surroundings of separator sheet surplus length part 38A, 38B so that the positive electrode sheet 10 (16A, 16B) near innermost circumference of winding R part 38A, 38B may become a desired curvature. For example, the number of rounds of the separator sheet surplus length portions 38A and 38B is about 2 to 10 rounds, preferably about 2 to 5 rounds, and usually about 2 to 3 rounds. If it is less than this range, the curvature of the positive electrode sheet 10 may be reduced and the effect of suppressing the peeling of the positive electrode active material layer 14 may not be sufficiently obtained. Since the separator sheet in the peripheral portion increases too much, the battery performance may deteriorate. In this embodiment, the separator sheet surplus length portions 38 </ b> A and 38 </ b> B are wound around the inside of the positive electrode sheet 10 two and a half rounds in one direction, and then folded half a turn in the direction opposite to the one direction. Thus, the separator sheet surplus length portions 38A and 38B may include a portion that is folded back in the direction opposite to the one direction. Even in this case, if the separator sheet surplus length portions 38A and 38B are laminated in the thickness direction of the flat wound electrode body 80 inside the innermost peripheral portion 16 of the positive electrode sheet 10, the positive electrode sheet 10 Thus, the effect of suppressing the peeling of the positive electrode active material layer 14 can be obtained.

  Further, the number of turns of the negative electrode sheet extra length portion 28 may be appropriately adjusted so that the positive electrode sheet 10 (16A, 16B) near the innermost circumference of the wound R portions 38A, 38B has a desired curvature. For example, the number of rounds of the negative electrode sheet extra length portion 28 is about 1 to 5 rounds, preferably about 1 to 3 rounds, and usually about 1 to 2 rounds. If the amount is less than this range, the curvature of the positive electrode sheet 10 may be reduced and the effect of suppressing the peeling of the positive electrode active material layer 14 may not be sufficiently obtained. Since the proportion of the innermost peripheral negative electrode sheet that does not contribute to the reaction increases, the battery performance may deteriorate. In this embodiment, the negative electrode sheet surplus length portion 28 is wound around the inside of the positive electrode sheet 10 in one direction.

  Furthermore, in this embodiment, as shown in FIG. 5, the positive electrode sheet 10 is provided with the positive electrode active material layer 14 on both surfaces of the positive electrode current collector 12 up to the winding start end 15. In this case, it is desirable that the winding start end 15 of the positive electrode sheet 10 is disposed on one of the winding flat portions 90A and 90B as shown in FIG. Is placed). When the winding start end 15 of the positive electrode sheet 10 is disposed in the winding R portions 92A and 92B having a high curvature, the positive electrode active material layer 14 is easily peeled off due to stress applied during charging and discharging. Since the winding start end 15 is disposed in the winding flat portions 90A and 90B having no curvature, peeling of the positive electrode active material layer 14 can be suppressed. When the winding start end 15 is arranged in the winding flat portions 90A and 90B, the plane existence ratio of the positive electrode sheet 10 with respect to the winding flat portions 90A and 90B is approximately 50% or more (more preferably 75% or more). preferable. Thereby, peeling of the positive electrode active material layer 14 can be suppressed more reliably.

  Next, the manufacturing method of the secondary battery according to the present embodiment will be described by taking the flat wound electrode body 80 having the above structure and the secondary battery 100 including the flat wound electrode body 80 as an example.

First, the positive electrode sheet 10 and the negative electrode sheet 20 are produced. The positive electrode sheet 10 can be formed by providing a positive electrode active material layer 14 on both sides of a long positive electrode current collector 12. For the positive electrode current collector 12, an aluminum foil 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 LiMn ₂ O ₄ , LiCoO ₂ , LiNiO _{2 and the} like. For example, an aluminum foil having a length of 2 m to 7 m (for example, 5 m), a width of 6 cm to 15 cm (for example, 8 cm), and a thickness of about 5 μm to 20 μm (for example, 15 μm) is used as a current collector. By forming the positive electrode active material layer 14 having a thickness of about 40 μm to 300 μm (for example, 80 μm), a suitable positive electrode sheet 10 can be obtained.

  The negative electrode sheet 20 may be formed by providing a negative electrode active material layer 24 on both sides of a long negative electrode current collector 22. For the negative electrode current collector 22, a copper foil 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-containing transition metal oxides and transition metal nitrides. For example, a copper foil having a length of 2 m to 7 m (for example, 5.2 m), a width of 6 cm to 15 cm (for example, 8 cm), and a thickness of about 5 μm to 20 μm (for example, 10 μm) is used. A suitable negative electrode sheet 20 can be obtained by forming a negative electrode active material layer having a thickness of about 40 μm to 300 μm (for example, 80 μm).

  Suitable separator sheets 30A and 30B used between the positive and negative electrode sheets 20 and 30 include those made of a porous polyolefin resin. For example, a porous separator sheet made of a synthetic resin (for example, made of polyolefin such as polyethylene) having a length of 2 m to 7 m (for example, 5.5 m), a width of 8 cm to 12 cm (for example, 9 cm), and a thickness of about 5 μm to 30 μm (for example, 20 μm). Preferably used.

  Once the positive electrode sheet 10, the negative electrode sheet 20, and the separator sheets 30A and 30B are prepared, a flat wound electrode body 80 is then produced. The flat wound electrode body 80 is manufactured through a winding process and a crushing process. Hereinafter, the winding process and the crushing process will be described in this order.

  The winding process is a process in which the positive electrode sheet 10 and the negative electrode sheet 20 are stacked via separator sheets 30A and 30B and wound into a cylindrical shape. In the winding step, the positive electrode sheet 10, the separator sheet 30A, the negative electrode sheet 20, and the separator sheet 30B are laminated in this order, and the outer periphery in a cross-sectional shape perpendicular to the axis is wound around a winding core (not shown) with a perfect circle. To do.

  At that time, the separator sheets 30 </ b> A and 30 </ b> B are wound two or more times inside the innermost peripheral portion 16 of the wound positive electrode sheet 10. In this case, before winding the positive electrode sheet 10 on the winding core, it is preferable to wind the separator sheets 30A and 30B in advance two or more times. Then, by winding the positive electrode sheet 10 together with the separator sheet, the separator sheets 30A and 30B can be wound two or more times inside the positive electrode sheet 10.

  Further, the negative electrode sheet 20 is wound more than once around the innermost peripheral portion 16 of the wound positive electrode sheet 10. In this case, before winding the positive electrode sheet 10 around the winding core, the negative electrode sheet 20 may be wound in advance for one or more turns. Thereafter, by winding the positive electrode sheet 10 together with the negative electrode sheet 20, the negative electrode sheet 20 can be wound one or more times inside the positive electrode sheet 10.

  Note that the cross-sectional shape of the winding core does not have to be a perfect circle. The winding core only needs to have a shape (typically a substantially circular shape) in which each sheet is laminated and wound into a substantially cylindrical shape.

  The crushing step is a step of obtaining the flat wound electrode body 80 by crushing the cylindrical wound body in the radial direction. In this crushing step, the wound body is crushed so that the winding start end 15 of the positive electrode sheet 10 is disposed on one of the winding flat portions 90A and 90B.

  In this case, what is necessary is just to determine the crushing direction of a winding body suitably so that the winding start end 15 may be arrange | positioned in a winding flat part. Alternatively, when the crushing direction is determined by the device configuration or the like, in the winding step, the setting position of the winding start end 15 may be adjusted so that the winding start end 15 is disposed on the winding flat portion. Thereby, the electrode body 80 in which the winding start end 15 of the positive electrode sheet 10 is disposed in the winding flat portions 90A and 90B is obtained.

  In this way, the flat wound electrode body 80 according to the present embodiment can be manufactured. The above steps can also be grasped as a method for manufacturing the flat wound electrode body 80.

Subsequently, the flat wound electrode body 80 having such a configuration is accommodated in the container body 52, and an appropriate nonaqueous electrolytic solution is disposed (injected) into the container body 52. As the non-aqueous electrolyte accommodated in the container main body 52 together with the wound electrode body 80, the same non-aqueous electrolyte as used in conventional lithium ion batteries can be used without any particular limitation. For example, an appropriate amount (for example, concentration 1M) of lithium salt such as LiPF ₆ is dissolved in a nonaqueous electrolytic solution such as a mixed solvent of diethyl carbonate and ethylene carbonate (for example, volume ratio 1: 1) and used as an electrolytic solution. That's fine.

  The electrolytic solution is accommodated in the container main body 52 together with the wound electrode body 80, and the opening of the container main body 52 is sealed by welding or the like with the lid body 54, thereby constructing (assembling) the battery 100 according to the present embodiment. Is completed. In addition, the sealing process of the container main body 52 and the arrangement | positioning (injection) process of electrolyte solution can be performed similarly to the method currently performed by manufacture of the conventional lithium ion battery. Thereafter, the battery is conditioned (initial charge / discharge). You may perform processes, such as degassing and a quality inspection, as needed.

  According to the manufacturing method of this embodiment, since the separator sheets 30A and 30B are wound two or more times inside the innermost peripheral portion 16 of the positive electrode sheet 10, the wound body is crushed. The stress applied to the positive electrode sheet 10 is reduced. In addition, since the thick negative electrode sheet 20 is wound on the inner side of the innermost peripheral portion 16 of the positive electrode sheet 10 for one or more turns and then the wound body is crushed, the stress applied to the positive electrode sheet 10 during the crushing is further increased. Get smaller. Therefore, the wound body can be crushed while suppressing peeling of the positive electrode active material layer 14. Therefore, according to the present embodiment, the highly reliable secondary battery 100 having excellent discharge cycle characteristics can be manufactured stably (with high quality stability).

  In addition, as a method of producing the flat wound electrode body 80, it is not restricted to the method of crushing after winding in the cylindrical shape mentioned above. For example, you may wind so that it may become flat shape from the beginning using a flat winding core. However, since the cylindrical winding is easier to wind at a higher speed than the flat winding, the productivity of the flat wound electrode body 80 can be increased by adopting a method of crushing after winding into a cylindrical shape.

  In order to confirm that the secondary battery is constructed using the flat wound electrode body 80 according to the present embodiment, it is possible to provide a battery having excellent charge / discharge cycle characteristics (output maintaining performance). went.

  That is, as Examples 1 to 4, a positive electrode sheet 10 (length 5 m, width 8 cm, thickness 80 μm) in which the positive electrode active material layer 14 was coated on both surfaces of an aluminum foil as the positive electrode current collector 12, and the negative electrode current collector A negative electrode sheet 20 (length: 5.2 m, width: 8 cm, thickness: 80 μm) in which the negative electrode active material layer 24 is coated on both surfaces of a copper foil as the electric body 22 is separated into two separator sheets (length: 5. 5 mm, width 9 cm, and thickness 20 μm) to produce a cylindrical wound body (the number of times of winding is 30 turns). At that time, the forming condition of the wound body was adjusted so that the separator sheet surplus length part was wound longer than the innermost peripheral part 16 of the wound positive electrode sheet 10 by the number of turns shown in Table 1. . Moreover, the forming conditions of the wound body were adjusted so that the negative electrode sheet extra length portion was wound longer than the innermost peripheral portion 16 of the wound positive electrode sheet 10 by the number of turns shown in Table 1. Subsequently, the flat wound electrode body 80 was produced by crushing the obtained wound body in the radial direction. At that time, the direction in which the wound body was crushed was adjusted so that the winding start end 15 of the positive electrode was disposed on the wound flat portion.

  Further, as Comparative Example 1, a flat wound electrode body 80 was produced using the negative electrode sheet surplus length portion 28 on which the negative electrode active material layer was coated on one side to the winding start end 25. A flat wound electrode body was produced in the same manner as in Example 1 except that the negative electrode sheet extra length portion 28 on which the negative electrode active material layer was coated on one side to the winding start end 25 was used. Further, as Comparative Example 2, a flat wound electrode body 80 in which the winding start end 15 of the positive electrode was disposed in the wound R portion was produced. A flat wound electrode body was produced in the same manner as in Comparative Example 1 except that the winding start end 15 of the positive electrode was disposed in the wound R portion.

  The flat wound electrode bodies according to Examples 1 to 4 and Comparative Examples 1 and 2 thus produced were flattened battery containers 50 (height 9.2 cm, width 11 cm, thickness together with non-aqueous electrolyte). A lithium ion battery for testing was assembled by sealing the opening of the battery container 50 in an airtight manner. Thereafter, an initial charge / discharge treatment (conditioning) was performed by a conventional method to obtain a test lithium ion battery.

  For each of the test lithium ion batteries obtained as described above, a charge / discharge cycle test was repeated. Specifically, under a condition of a temperature of 60 ° C., a charge / discharge cycle in which charging is performed up to a maximum voltage of 4.1 V at a constant current of 10 A and discharging is performed up to a minimum voltage of 3.0 V at a constant current of 10 A is repeated 10,000 times. And repeated.

  Moreover, the output maintenance factor was calculated from the initial output before the charge / discharge cycle test and the output after the charge / discharge cycle test. In the output test, each battery was adjusted to 50% of the battery capacity (SOC = 50%) under the condition of a temperature of 25 ° C., and the current when the voltage after 10 seconds became 3.0 V after flowing an arbitrary current. A value was obtained, and an output (W) was calculated from the product of the current value and the voltage value. The output retention rate (%) was calculated by “(output after charge / discharge cycle test / initial output) × 100”. In addition, after the output test, each battery was disassembled, and whether or not the positive electrode active material layer 14 was detached after the cycle test was visually confirmed. The results are shown in Table 1.

  As shown in Table 1, in the batteries of Examples 1 to 4 in which the negative electrode sheet surplus portion 28 with the negative electrode active material layer coated on both sides was wound on the inside of the positive electrode one or more times, the negative electrode active material layer was coated on one side. Compared with the batteries of Comparative Examples 1 and 2 in which the negative electrode sheet surplus length portion 28 is wound around the inside of the positive electrode one or more times, a high output retention rate is exhibited, and there is no detachment of the positive electrode active material layer after the cycle test I understood. From this, the negative electrode sheet surplus length portion 28 coated with both sides of the negative electrode active material layer is wound inside the positive electrode one or more times, thereby avoiding the detachment of the positive electrode active material layer and improving the charge / discharge cycle characteristics. It was confirmed that it was possible. In addition, the batteries of Examples 3 and 4 in which the separator extra length was wound twice or more inside the positive electrode maintained a higher output than the battery of Example 1 in which the separator extra length was wound one round inside the positive electrode. Showed the rate. From this, it was confirmed that the charge / discharge cycle characteristics can be improved by winding the separator extra length portion two or more times inside the positive electrode.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, the type of 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 a negative electrode made of lithium metal or lithium alloy, nickel hydrogen batteries, nickel cadmium It may be a battery.

  Note that the battery 100 according to the present embodiment is excellent in battery performance (particularly cycle characteristics) as described above, and thus can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, as schematically shown in FIG. 6, the present invention provides a vehicle (typically an automobile, in particular, a vehicle including such a lithium secondary battery (which may be an assembled battery formed by connecting in series) 100 as a power source. A vehicle including an electric motor such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle) 1 is provided.

DESCRIPTION OF SYMBOLS 10 Positive electrode sheet 12 Positive electrode collector 14 Positive electrode active material layer 15 Winding start end 16 of positive electrode sheet Innermost peripheral portion 20 of positive electrode sheet Negative electrode sheet 22 Negative electrode current collector 24 Negative electrode active material layer 25 Winding start end 28 of negative electrode sheet Sheet surplus length portion 30A, 30B Separator sheet 38A, 38B Separator sheet surplus length portion 50 Container 52 Container body 54 Lid 70 Positive electrode terminal 72 Negative electrode terminal 74 Positive electrode lead terminal 76 Negative electrode lead terminal 80 Flat wound electrode body 82 Winding core portion 90A, 90B Winding flat part 92A, 92B Winding R part 100 Secondary battery

Claims (10)

A positive electrode sheet having a positive electrode active material layer provided on both sides of the positive electrode current collector and a negative electrode sheet having a negative electrode active material layer provided on both sides of the negative electrode current collector are wound through a separator sheet to be flat. A battery having a flat wound electrode body having an outer shape of
The separator sheet has a separator sheet surplus length portion wound inside than the innermost peripheral portion of the positive electrode sheet,
The separator sheet surplus length portion is a secondary battery that is disposed so as to wind at least two rounds inside the innermost peripheral portion of the positive electrode sheet. The negative electrode sheet has a negative electrode sheet extra length wound inside than the innermost peripheral portion of the positive electrode sheet,
The negative electrode sheet surplus length portion is provided on both surfaces of the negative electrode current collector until the negative electrode active material layer is wound to the winding start end, and at least one turn inside the innermost peripheral portion of the positive electrode sheet. The secondary battery according to claim 1, wherein the secondary battery is arranged as described above. The flat wound electrode body is composed of two wound flat portions facing each other and two wound R portions that connect the ends of the two flat portions,
In the positive electrode sheet, the positive electrode active material layer is provided on both surfaces of the positive electrode current collector up to a winding start end, and the winding start end is disposed on one of the winding flat portions. Item 3. The secondary battery according to Item 1 or 2. A positive electrode sheet in which a positive electrode active material layer is provided on both sides of a positive electrode current collector and a negative electrode sheet in which a negative electrode active material layer is provided on both sides of a negative electrode current collector are wound in a flat shape via a separator sheet. A battery comprising a flat wound electrode body having a flat outer shape,
The negative electrode sheet has a negative electrode sheet extra length wound inside than the innermost peripheral portion of the positive electrode sheet,
The negative electrode sheet surplus length portion is provided on both surfaces of the negative electrode current collector until the negative electrode active material layer is wound to the winding start end, and at least one turn inside the innermost peripheral portion of the positive electrode sheet. A secondary battery arranged to be. The separator sheet has a separator sheet surplus length portion wound inside than the innermost peripheral portion of the positive electrode sheet,
The secondary battery according to claim 4, wherein the separator sheet extra length portion is disposed so as to wind at least two rounds inside the innermost peripheral portion of the positive electrode sheet. The flat wound electrode body is composed of two wound flat portions facing each other and two wound R portions that connect the ends of the two flat portions,
In the positive electrode sheet, the positive electrode active material layer is provided on both surfaces of the positive electrode current collector up to a winding start end, and the winding start end is disposed on one of the winding flat portions. Item 6. The secondary battery according to Item 4 or 5. A positive electrode sheet having a positive electrode active material layer provided on both sides of the positive electrode current collector and a negative electrode sheet having a negative electrode active material layer provided on both sides of the negative electrode current collector are wound in a flat shape via a separator sheet. A method of manufacturing a battery comprising a flat wound electrode body that exhibits a flat outer shape,
A step of laminating a positive electrode sheet and a negative electrode sheet via a separator sheet, and winding in a cylindrical shape;
Crushing the cylindrical wound body in the radial direction to obtain a flat wound electrode body,
In the winding step, the separator sheet is wound two or more times inside the innermost peripheral portion of the wound positive electrode sheet. In the negative electrode sheet, the negative electrode active material layer is provided on both sides of the negative electrode current collector until the winding start end,
The manufacturing method according to claim 7, wherein in the winding step, the negative electrode sheet is wound one or more times inside an innermost peripheral portion of the wound positive electrode sheet. The flat wound electrode body is composed of two wound flat portions facing each other and two wound R portions that connect the ends of the two flat portions,
In the positive electrode sheet, the positive electrode active material layer is provided on both surfaces of the positive electrode collector until the winding start end,
9. The crushing step here, wherein the winding body is crushed so that a winding start end of the positive electrode sheet is disposed in one of the winding flat portions. Manufacturing method.   A vehicle comprising the secondary battery according to any one of claims 1 to 6 or the secondary battery produced by the production method according to any one of claims 7 to 9.

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