JP2020161293A - Lithium ion secondary battery - Google Patents

Abstract

To suppress a separator of a lithium-ion secondary battery from being damaged.SOLUTION: A negative electrode plate 16 of a lithium ion secondary battery has a facing portion 16D facing positive electrode mixture layers 19 of positive electrode plates 15 via a separator 17, and a non-facing portion 16C which does not face the positive electrode mixture layers 19. A tip of a first negative electrode mixture layer 21A and a tip of a second negative electrode mixture layer 21B in the non-facing portion 16C interposed between a connection portions 15A of the positive electrode plate 15 are displaced from each other in a direction to a tip of the non-facing portion 16C. A first relative distance which is the shortest distance between a base end 50 of the non-facing portion 16C and the tip of the first negative electrode mixture layer 21A is shorter than a second relative distance which is the shortest distance between the base end 50 of the non-facing portion 16C and the tip of the second negative electrode mixture layer 21B. A difference between the first relative distance and the second relative distance is in a range from not less than 30 μm to not more than 300 μm, and the first relative distance and the second relative distance are in a range which is greater than 0 mm and less than 2.9 mm.SELECTED DRAWING: Figure 3

Description

The present invention relates to a lithium ion secondary battery.

Lithium-ion secondary batteries have a high energy density and a high capacity, and are therefore used as a driving power source for electric vehicles (EVs) and hybrid vehicles (HVs).
As shown in FIG. 7, the lithium ion secondary battery described in Patent Document 1 has a positive electrode plate 100 having positive electrode mixture layers 102 on both sides of a positive electrode base material 101 and a negative electrode combination on both sides of a negative electrode base material 111. It has an electrode body in which a negative electrode plate 110 provided with an agent layer 112 is superposed via a separator 120. Further, the positive electrode plate 100 has a connecting portion 116 that does not have the positive electrode mixture layer 102. The negative electrode plate 110 includes a connecting portion 117 that does not have the negative electrode mixture layer 112. These connecting portions 116 and 117 function as current collectors for extracting electricity from the positive electrode plate and the negative electrode plate. The connecting portions 116 of the plurality of positive electrode plates 100 are pressed against each other to form a bundle, and are electrically connected to the positive electrode side current collecting member. Further, the connecting portions 117 of the plurality of negative electrode plates 110 are also pressed against each other to form a bundle, and are electrically connected to the current collecting member on the negative electrode side.

Further, since the length of the negative electrode mixture layer 112 provided on the electrode body is larger than the length of the positive electrode mixture layer 102, the negative electrode plate 110 faces the positive electrode mixture layer 102 via the separator 120. In addition to 118, a non-opposing portion 119, which is a portion not facing the positive electrode mixture layer 102, is provided (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2015-997700

Like the battery described in Patent Document 1, in a state where a part of the non-opposing portion 119 of the negative electrode plate 110 is sandwiched between the connecting portions 116 of the positive electrode plate 100, the connecting portions 116 are collected to collect current on the positive electrode side. When the portion is formed, the non-opposing portion 119 of the negative electrode plate 110 interposed between the connecting portions 116 receives the pressing force. At this time, if the non-opposing portion 119 does not bend along the direction of the pressing force, the adjacent separator 120 may be damaged depending on the internal structure of the battery.

The present invention has been made in view of such circumstances, and an object of the present invention is to suppress damage to a separator of a lithium ion secondary battery.

The lithium ion secondary battery that solves the above problems includes a positive electrode base material, a positive electrode mixture layer provided on both sides of the positive electrode base material, and a portion of the positive electrode base material not provided with the positive electrode mixture layer on both sides. A positive electrode plate having a connection portion, a negative electrode base material, a first negative electrode mixture layer provided on one surface of the negative electrode base material, a second negative electrode mixture layer provided on the other surface of the negative electrode base material, and the above. The positive electrode plate includes a negative electrode plate having a connection portion that is a portion where the first negative electrode mixture layer and the second negative electrode mixture layer are not provided, and a separator provided between the positive electrode plate and the negative electrode plate. A positive electrode side current collecting portion including the connection portion of the positive electrode plate is provided at one end of the negative electrode plate and the laminated body in which the separator is laminated or the wound body in which the laminated body is wound, and the other end. A lithium ion secondary battery having an electrode body provided with a negative electrode side current collecting portion including the connection portion of the negative electrode plate, wherein the negative electrode plate is a combination of the positive electrodes of the positive electrode plate via the separator. The first negative electrode mixture layer in the non-opposing portion having a facing portion facing the agent layer and a non-opposing portion not facing the positive electrode mixture layer and sandwiched between connecting portions of the positive electrode plates. And the tip of the second negative electrode mixture layer are displaced in the direction toward the tip of the non-opposing portion, which is the shortest distance between the base end of the non-opposing portion and the tip of the first negative electrode mixture layer. The first relative distance is shorter than the second relative distance, which is the shortest distance between the base end of the non-opposing portion and the tip of the second negative electrode mixture layer, and the difference between the first relative distance and the second relative distance. Is a range of 30 μm or more and less than 300 μm, and the first relative distance and the second relative distance are within a range larger than 0 mm and smaller than 2.9 mm.

According to the above configuration, among the non-opposing portions sandwiched between the connecting portions of the positive electrode plates, the tip of the first negative electrode mixture layer and the tip of the second negative electrode mixture layer are displaced in the direction toward the tip of the non-opposing portion. There is. Further, the first relative distance from the base end of the non-opposing portion to the tip of the first negative electrode mixture layer is shorter than the second relative distance from the base end of the non-opposing portion to the tip of the second negative electrode mixture layer. By forming the positive electrode side current collecting portion, the non-opposing portion of the negative electrode plate sandwiched between the positive electrode plates via the separator is compressed by receiving pressing pressure from both sides, but the first negative electrode mixture layer is short. By being provided so as to be, it becomes easy to bend in the direction of the larger pressing force among the pressing forces received from both sides. In this way, the non-opposing portion of the negative electrode plate does not oppose or break against the pressing force, but bends with an appropriate curvature along the direction of the pressing force, so that the negative electrode base material and the negative electrode mixture layer are strongly pressed against the separator. Damage to the separator due to this can be suppressed.

Further, if the difference between the first relative distance and the second relative distance is too small, the non-opposing portion of the negative electrode plate is less likely to bend when forming the positive electrode side current collector, so that the separator may be different depending on the configuration of the electrode body. It may be damaged. Further, if the difference between the first relative distance and the second relative distance is excessive, wrinkles are generated on the negative electrode base material, and the lithium ion concentration in the wrinkles is locally increased, so that lithium is likely to be deposited on the positive electrode plate. .. Further, in the battery manufacturing process, wrinkles may be generated on the separator due to the influence of wrinkles generated on the negative electrode base material, and the separator may be damaged. According to the above configuration, since the difference between the first relative distance and the second relative distance is 30 μm or more, damage to the separator can be suppressed. Further, since the difference between the first relative distance and the second relative distance is less than 300 μm, it is possible to suppress the precipitation of lithium and the damage of the separator.

Further, when the first relative distance from the base end of the non-opposing portion to the tip of the first negative electrode mixture layer and the second relative distance from the base end of the non-opposing portion to the tip of the second negative electrode mixture layer become long, it is not yet. Since the number of facing portions increases, the concentration of lithium ions that move from the non-opposing portion to the end portion of the positive electrode mixture layer during discharge also increases. As the concentration of lithium ions at this end increases, lithium tends to precipitate at this portion. According to the above configuration, under the condition that the difference between the first relative distance and the second relative distance is in the range of 30 μm or more and less than 300 μm, the first relative distance and the second relative distance are larger than 0 mm, so that the non-opposing portion Can be secured. Further, since the first relative distance and the second relative distance are smaller than 2.9 mm, the concentration of lithium ions contained in the non-opposing portion can be set in an appropriate range, and the precipitation of lithium on the positive electrode plate can be suppressed.

Regarding the lithium ion secondary battery, it is preferable that the tip of the negative electrode base material protrudes from the first negative electrode mixture layer and the second negative electrode mixture layer.
According to the above configuration, the tip of the negative electrode base material projects more than the first negative electrode mixture layer and the second negative electrode mixture layer, so that the tip of the negative electrode base material easily bends in the direction of the pressing force received from the positive electrode plate via the separator. As a result, the non-opposing portion bends with an appropriate curvature between the connecting portions of the positive electrode plates, so that damage to the separator due to contact between the negative electrode plate and the separator can be suppressed.

Regarding the lithium ion secondary battery, the third relative distance from the base end of the non-opposing portion to the tip end of the negative electrode base material is preferably 0.3 mm or more and 3.0 mm or less.
If the third relative distance from the base end of the non-opposing portion to the tip of the negative electrode base material, that is, the negative electrode base material of the non-opposing portion is too short, the tip of the first negative electrode mixture layer and the tip of the second negative electrode mixture layer are pressed. It becomes difficult to shift. Further, if the negative electrode base material of the non-opposing portion is too long, the separator is easily damaged when forming the positive electrode side current collecting portion. According to the above configuration, since the third relative distance in the negative electrode base material is 0.3 mm or more, the tip of the first negative electrode mixture layer and the tip of the second negative electrode mixture layer can be shifted by providing a sufficient difference. it can. Further, since the third relative distance is set to 3.0 mm or less, damage to the separator can be suppressed.

According to the present invention, damage to the separator of the lithium ion secondary battery can be suppressed.

The figure which shows the outline of the perspective structure about one Embodiment which embodied the lithium ion secondary battery. It is the electrode body of the same embodiment, and the figure which developed a part thereof. It is sectional drawing at the position 3-3 of the electrode body of FIG. 2, and is the figure which shows a part of it schematically. It is a part of the electrode body of FIG. 3, and is an enlarged view of the non-opposing portion of the negative electrode plate. It is a schematic diagram of the non-opposed portion at the time of assembling the electrode body in the same embodiment or after the electrode body is assembled, (a) is the non-opposed portion of the present embodiment, and (b) is the conventional non-opposed portion. Shown. Table of Examples and Comparative Examples in which the configuration of the non-opposing portion of the lithium ion secondary battery was changed. It is a part of a conventional lithium ion secondary battery, and is an enlarged view of a non-opposing part of a negative electrode plate.

An embodiment of the lithium ion secondary battery will be described with reference to FIGS. 1 to 6.
As shown in FIG. 1, the lithium ion secondary battery 10 is housed inside a rectangular parallelepiped battery case 11 having an opening on the upper side, a lid portion 12 for sealing the battery case 11, and the inside of the battery case 11. It includes an electrode body 20. Further, a non-aqueous electrolyte is housed in the battery case 11. The lithium ion secondary battery 10 is formed by attaching a lid portion 12 to the battery case 11 to form a sealed battery case. Further, the lithium ion secondary battery 10 is provided with two external terminals 13 used for charging and discharging electric power on the lid portion 12.

The electrode body 20 is provided with a positive electrode side current collector 20A at one end and a negative electrode side current collector 20B at the other end. The positive electrode side current collecting unit 20A is electrically connected to the positive electrode side current collecting member 51, and the negative electrode side current collecting unit 20B is electrically connected to the negative electrode side current collecting member 52. The positive electrode side current collecting member 51 is electrically connected to the external terminal 13 of the positive electrode, and the negative electrode side current collecting member 52 is electrically connected to the external terminal 13 of the negative electrode.

The configuration of the electrode body 20 will be described with reference to FIG. The electrode body 20 is a wound body obtained by winding a laminated body in which a positive electrode plate 15 and a negative electrode plate 16 are laminated via a separator 17. It is a laminated body wound around the separator 17. The positive electrode plate 15 is formed in a long shape and includes a sheet-shaped positive electrode base material 18 and a positive electrode mixture layer 19 provided on both sides of the positive electrode base material 18. The negative electrode plate 16 is formed in a long shape and includes a sheet-shaped negative electrode base material 23 and a negative electrode mixture layer 21 provided on both sides of the negative electrode base material 23. The laminated body before winding is laminated in the order of the positive electrode plate 15, the separator 17, the negative electrode plate 16, and the separator 17 so that the longitudinal directions of the positive electrode plate 15 and the negative electrode plate 16 coincide with each other.

The electrode body 20 is wound in the long direction of the positive electrode plate 15 and the negative electrode plate 16, and is formed into a flat shape by pressing the wound laminated body from the peripheral surface thereof. At one end of the positive electrode plate 15 in the lateral direction, a connecting portion 15A is provided in which the positive electrode mixture layer 19 is not formed and the positive electrode base material 18 is exposed. The connecting portion 15A constitutes a positive electrode side current collecting portion 20A. In the positive electrode side current collector 20A, the facing surfaces of the plurality of connecting portions 15A are pressed against each other.

At one end of the negative electrode plate 16 in the lateral direction, a connecting portion 16A is provided in which the negative electrode mixture layer 21 is not formed and the negative electrode base material 23 is exposed. The connecting portion 16A constitutes the negative electrode side current collecting portion 20B. In the negative electrode side current collector 20B, the facing surfaces of the plurality of connecting portions 16A are pressed against each other.

The configurations of the positive electrode plate 15 and the negative electrode plate 16 will be described with reference to FIG. FIG. 3 is a diagram schematically showing a cross section at positions 3 and 3 in FIG. The positive electrode base material 18 is formed of a metal foil (or a thin metal plate). The material constituting the positive electrode base material 18 includes, for example, aluminum or an aluminum alloy. The tip of the positive electrode mixture layer 19 has a tapered shape on the connection portion 15A side of the positive electrode base material 18, but the tip of the positive electrode mixture layer 19 does not have a tapered shape and has the same thickness as the other parts. You may be.

As the positive electrode active material contained in the positive electrode mixture, one or a plurality of various materials known to be usable as the positive electrode active material of the lithium ion secondary battery can be used. As a preferable example, lithium composite metal oxides such as layered type and spinel type (for example, LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiCrMnO ₄ , LiFePO ₄ ). Can be mentioned. Examples of the conductive material include carbon black such as acetylene black and Ketjen black, and other powdered carbon materials (such as graphite). Examples of the binder include polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE) and the like. The positive electrode mixture contains a conductive agent, a binder, and the like in addition to the positive electrode active material.

The negative electrode plate 16 includes a first negative electrode mixture layer 21A provided on one surface of the negative electrode base material 23 and a second negative electrode mixture layer 21B provided on the other surface. When the first negative electrode mixture layer 21A and the second negative electrode mixture layer 21B are described without distinguishing them from each other, they are simply described as the negative electrode mixture layer 21. The negative electrode base material 23 is formed of a metal foil. The material constituting the negative electrode base material 23 includes, for example, copper or nickel.

As the negative electrode active material contained in the negative electrode mixture, one or more kinds of various materials known to be usable as the negative electrode active material of the lithium ion secondary battery can be used. For example, carbon materials such as graphite (graphite), non-graphitized carbon (hard carbon), easily graphitized carbon (soft carbon), and carbon nanotubes can be mentioned. The negative electrode mixture contains a conductive agent, a binder, and the like in addition to the negative electrode active material.

The separator 17 is a sheet made of a resin such as a polyolefin resin. Further, an insulating layer may be provided on the surface of the separator 17. The insulating layer is an inorganic filler having an insulating property, a resin having an insulating property, or the like. The separator 17 has a lower rigidity than the positive electrode base material 18 and the negative electrode base material 23.

Further, the length L2 in the width direction of the negative electrode mixture layer 21 is longer than the length L1 in the width direction of the positive electrode mixture layer 19. As a result, the negative electrode mixture layer 21 of the negative electrode plate 16 is not opposed to the positive electrode mixture layer 19 via the separator 17, and the facing portion 16D is opposed to the positive electrode mixture layer 19 via the separator 17. Parts 16B and 16C are provided. After the electrode body 20 is formed, the non-opposing portion 16C is sandwiched between the connecting portion 15A of the upper positive electrode plate 15 in FIG. 3 and the connecting portion 15A of the lower positive electrode plate 15 (not shown).

FIG. 4 is an enlarged view of the region Z including the non-opposing portion 16C of the negative electrode plate 16 shown in FIG. The base end 50 shown by the broken line is the base end of the non-opposing portion 16C and indicates the boundary between the facing portion 16D and the non-opposing portion 16C. Further, the length of the first negative electrode mixture layer 21A from the base end 50 is "length A", the length of the second negative electrode mixture layer 21B from the base end 50 is "length B", and the negative electrode base material 23. Let the length from the base end 50 of the be "length C".

Of the length A, the length B, and the length C, the length C of the negative electrode base material 23 is the largest. That is, at the tip of the negative electrode plate 16, the negative electrode base material 23 protrudes most (C> A, C> B). Further, the length B of the second negative electrode mixture layer 21B is longer than the length A of the first negative electrode mixture layer 21A (B> A).

The operation of the lithium ion secondary battery of the present embodiment will be described with reference to FIG. FIG. 5A shows the tip portion of the negative electrode plate 16 of the present embodiment including the non-opposing portion 16C. When the positive electrode side current collecting portion 20A is formed, the connecting portion 15A of the positive electrode plate 15 is pressed to have a predetermined thickness, so that the tip portion of the negative electrode plate 16 sandwiched between the connecting portions 15A is formed. It receives pressing force from their connection portion 15A via the separator 17. As a result, the tip of the negative electrode plate 16 bends toward the larger pressing force. Since the first negative electrode mixture layer 21A, the second negative electrode mixture layer 21B, and the negative electrode base material 23 have rigidity, the tip portion of the negative electrode plate 16 has a portion where the first negative electrode mixture layer 21A is not provided on one side. As much as it has, it becomes easier to bend along the pressing force.

Further, in the negative electrode base material 23, the protruding portion longer than the first negative electrode mixture layer 21A is shown at the tip position 103 of the first negative electrode mixture layer 21A and the tip position 104 of the second negative electrode mixture layer 21B. It bends step by step under the pressing force from the middle left side and the pressing force from the right side. Therefore, the non-opposing portion 16C of the negative electrode base material 23 can be bent with an appropriate curvature without breaking in the middle. Note that FIG. 5A shows a state in which the non-opposing portion 16C is bent toward the first negative electrode mixture layer 21A, but the non-opposing portion 16C is bent toward the second negative electrode mixture layer 21B. Also in this case, the negative electrode base material 23 bends stepwise, and the action is the same.

FIG. 5B shows a non-opposing portion 16Z of the conventional negative electrode plate 16. In the non-opposing portion 16Z, the tip of the first negative electrode mixture layer 21A and the tip of the second negative electrode mixture layer 21B are provided at the same position without being displaced. Compared to the non-opposing portion 16C of the present embodiment, the non-opposing portion 16Z has a longer first negative electrode mixture layer 21A and a second negative electrode mixture layer 21B, so that the rigidity as a whole is increased and it is difficult to bend. When the pressing force from both sides of the negative electrode plate 16 is small and the pressing force from both sides is large, the contact point P1 between the second negative electrode mixture layer 21B and the separator 17 and the first negative electrode mixture layer 21A are formed. The force applied to the contact point P2 between the separator 17 and the separator 17 becomes particularly large. As a result, the separator 17 may be damaged. Further, when only the tip of the negative electrode base material 23 is projected without shifting the tip of the first negative electrode mixture layer 21A and the tip of the second negative electrode mixture layer 21B, the tip of the negative electrode base material 23 is easily bent. , It does not bend stepwise like the non-opposing portion 16C of the present embodiment. Therefore, the protruding portion of the negative electrode base material 23 is likely to be broken from the base end or the curvature is too large to protrude toward the separator 17 side to damage the separator 17.

Next, a preferable range of the length A of the first negative electrode mixture layer 21A, the length B of the second negative electrode mixture layer 21B, and the length C of the negative electrode base material 23 in the non-opposing portion 16C will be described. As described above, the length B of the second negative electrode mixture layer 21B is longer than the length A of the first negative electrode mixture layer 21A, and the length C of the negative electrode base material 23 is the length C of the first negative electrode mixture layer 21A. It is assumed that the length A and the length B of the second negative electrode mixture layer 21B are longer (C> B> A).

The difference (“BA”) between the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B is preferably 30 μm or more and less than 300 μm (condition 1). If the difference between the length A and the length B is less than 30 μm, the tip portion of the negative electrode plate 16 including the non-opposing portion 16C becomes difficult to bend when the positive electrode side current collector 20A is formed, so that the separator 17 is damaged. there is a possibility. Further, when the difference between the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B is 300 μm or more, wrinkles are likely to occur on the negative electrode base material 23. That is, the negative electrode mixture is in the form of a paste when applied to the negative electrode base material 23, but when it dries, the negative electrode mixture layer 21 generates a force to pull the negative electrode base material 23. When the difference between the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B becomes 300 μm or more and the difference in tensile force on both sides of the negative electrode base material 23 becomes large, the negative electrode base material Wrinkles occur in 23 due to the difference in tensile force. When wrinkles are formed on the negative electrode base material 23, lithium ions are likely to stay in the wrinkles during charging and discharging of the lithium ion secondary battery. Then, when the lithium ions staying in the wrinkles are concentrated on the end portion of the positive electrode mixture layer 19, lithium is likely to be deposited at the end portion. Further, if the negative electrode base material 23 is wrinkled in this way, the separator 17 may also be wrinkled in the process of winding the positive electrode plate 15, the negative electrode plate 16, and the separator 17, and the separator 17 may be damaged. .. By setting the difference between the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B within the above range, lithium precipitation is suppressed and damage to the separator 17 is suppressed. The effect is enhanced.

Further, the length C of the negative electrode base material 23 is preferably 0.3 mm or more and 3.0 mm or less (condition 2). When the length C is less than 0.3 mm, a sufficient space for shifting the tip of the first negative electrode mixture layer 21A and the tip of the second negative electrode mixture layer 21B cannot be secured. Further, if the negative electrode base material 23 of the non-opposing portion 16C exceeds 3.0 mm, the tip of the negative electrode base material 23 tends to come into contact with the separator 17 when forming the positive electrode side current collector 20A, and the separator 17 is damaged. there's a possibility that. By setting the length C of the negative electrode base material 23 to the above range, the effect of suppressing damage to the separator 17 is enhanced.

Further, the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B are preferably in a range larger than 0 mm and smaller than 2.9 mm (Condition 3). When the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B are 2.9 mm or more, the non-opposing portion 16C increases. More lithium ions move to the end of the mixture layer 19. When the concentration of lithium ions increases at the end of the positive electrode mixture layer 19, lithium tends to precipitate. By setting the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B within the above ranges, the negative electrode capacity can be secured and the precipitation of lithium can be suppressed. It is preferable that this "condition 3" is premised on "condition 1 (30 μm ≦ BA <300 μm)".

The effect of this embodiment will be described.
(1) According to the above configuration, among the tips of the negative electrode plates 16 sandwiched between the connecting portions 15A of the positive electrode plates 15, the tips of the first negative electrode mixture layer 21A and the tips of the second negative electrode mixture layer 21B are negative electrodes. It is displaced in the direction toward the tip of the plate 16. Further, the length A from the base end 50 of the non-opposing portion 16C to the tip of the first negative electrode mixture layer 21A is the length B from the base end 50 of the non-opposing portion 16C to the tip of the second negative electrode mixture layer 21B. Shorter than. By forming the positive electrode side current collecting portion 20A, the tip portion of the negative electrode plate 16 sandwiched between the positive electrode plates 15 via the separator 17 receives pressing pressure from both sides, but the first negative electrode mixture layer 21A is short. By being provided so as to be, it becomes easy to bend in the direction of the larger pressing force among the pressing forces received from both sides. In this way, the non-opposing portion 16C of the negative electrode plate 16 does not oppose or break against the pressing force, but bends with an appropriate curvature along the direction of the pressing force, so that the separator 17 is formed by contact between the negative electrode plate 16 and the separator 17. Damage can be suppressed.

Further, if the difference between the length A and the length B is too small, the non-opposing portion 16C of the negative electrode plate 16 becomes difficult to bend when forming the positive electrode side current collecting portion 20A. Therefore, depending on the configuration of the electrode body 20, The separator 17 may be damaged. Further, if the difference between the length A and the length B is too large, wrinkles are generated on the negative electrode base material 23, and lithium ions are likely to stay in the wrinkles. Therefore, the edge of the positive electrode plate 15 to which those lithium ions move moves. Lithium is likely to precipitate in the part. Further, in the battery manufacturing process, the separator 17 may also be wrinkled due to the influence of the wrinkles generated on the negative electrode base material 23, and the separator 17 may be damaged. In the above embodiment, since the difference between the length A and the length B is 30 μm or more, damage to the separator 17 can be suppressed. Further, since the difference between the length A and the length B is less than 300 μm, it is possible to suppress the precipitation of lithium and the damage of the separator 17.

(2) The tip of the negative electrode base material 23 protrudes from the first negative electrode mixture layer 21A and the second negative electrode mixture layer 21B, so that the tip of the negative electrode base material 23 can easily bend in the direction of the pressing force received from the positive electrode plate 15 via the separator 17. .. As a result, the non-opposing portion 16C bends with an appropriate curvature between the connecting portions 15A of the positive electrode plate 15, so that damage to the separator 17 due to contact between the negative electrode plate 16 and the separator 17 can be suppressed.

(3) The length A from the base end 50 of the non-opposing portion 16C to the tip of the first negative electrode mixture layer 21A and the length B from the base end 50 of the non-opposing portion 16C to the tip of the second negative electrode mixture layer 21B. As the length increases, the number of non-opposed portions 16C increases, so that the concentration of lithium ions that move from the non-opposed portion 16C to the end portion of the positive electrode mixture layer 19 during discharge also increases. As the concentration of lithium ions at this end increases, lithium tends to precipitate at this portion. In the above embodiment, since the length A and the length B are made larger than 0 mm, the non-opposing portion 16C can be secured. Further, since the length A and the length B are made smaller than 2.9 mm, the concentration of lithium ions contained in the non-opposing portion 16C can be set in an appropriate range, and the precipitation of lithium on the positive electrode plate 15 can be suppressed.

(4) If the length C from the base end 50 of the non-opposing portion 16C to the tip of the negative electrode base material 23, that is, the length C of the negative electrode base material 23 is too short, the tip of the first negative electrode mixture layer 21A and the second It becomes difficult to shift the tip of the negative electrode mixture layer 21B. Further, if the negative electrode base material 23 of the non-opposing portion 16C is too long, the separator 17 is likely to be damaged when the positive electrode side current collecting portion 20A is formed. By setting the length of the negative electrode base material 23 to 0.3 mm or more, the tip of the first negative electrode mixture layer 21A and the tip of the second negative electrode mixture layer 21B can be displaced by providing a sufficient difference. Further, since the length C is set to 3.0 mm or less, damage to the separator 17 can be suppressed.

Hereinafter, Examples 1 to 11 and Comparative Examples 1 to 5 will be described with reference to FIG. The examples do not limit the present invention. In addition, Examples 1 to 11 satisfy all the above-mentioned conditions 1 to 3.

(Example 1)
A negative electrode mixture paste containing graphite as a negative electrode active material is formed, and the negative electrode mixture paste is provided with connecting portions 16A and non-opposing portions 16B and 16C on both sides of a long negative electrode base material 23 made of copper foil. It was applied. Further, the negative electrode base material coated with the negative electrode mixture paste was dried and pressed to prepare the negative electrode plate 16. In the non-opposing portion 16C opposite to the connecting portion 16A, the length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the base. The length C of the negative electrode base material 23 from the end 50 was set to 950 μm, 980 μm, and 1 mm. In this case, the difference between the length A and the length B is 30 μm.

Further, a positive electrode mixture layer 19 was formed on both sides of a positive electrode base material 18 made of a long aluminum foil with connection portions 15A provided to prepare a positive electrode plate 15. Then, the positive electrode plate 15, the separator 17, the negative electrode plate 16, and the separator 17 were laminated in this order so that the connecting portion 15A of the positive electrode plate 15 protrudes to one side and the connecting portion 16A of the negative electrode plate 16 projects to the other side. .. As the separator 17, a sheet made of a polyolefin resin was used. Then, the laminated body was wound from the end portion in the longitudinal direction to prepare a wound body, and pressed from both sides so that the cross section had a flat shape. Further, a positive electrode side current collecting portion 20A was formed on one side of the wound body, and the positive electrode side current collecting member 51 was welded. Further, the connecting portion 16A protruding to the other side of the wound body was pressed to form the negative electrode side current collecting portion 20B, and the negative electrode side current collecting member 52 was welded.

Then, the electrode body 20 is housed in the battery case 11, and a non-aqueous electrolyte in which lithium hexafluorophosphate is dissolved in a solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC) is housed. Then, the lid portion 12 was attached to the battery case 11 to prepare the lithium ion secondary battery 10. Further, the electrode body 20 was housed in the battery case 11 and the lid portion 12 was attached to prepare a lithium ion secondary battery without a non-aqueous electrolyte.

(Example 2)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. The thickness was 900 μm, 950 μm, and 1 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Example 3)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 200 μm, 250 μm, and 0.3 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Example 4)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 200 μm, 250 μm, and 1 mm. Other than that, a secondary battery was prepared in the same manner as in Example 1.

(Example 5)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. The thickness was 900 μm, 950 μm, and 1 mm. Other than that, a secondary battery was prepared in the same manner as in Example 1.

(Example 6)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 2800 μm, 2850 μm, and 2.9 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Example 7)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 100 μm, 200 μm, and 0.3 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Example 8)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 850 μm, 950 μm, and 1 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Example 9)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. The thickness was 700 μm, 850 μm, and 1 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Example 10)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. The thickness was 700 μm, 800 μm, and 1 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Example 11)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 2600 μm, 2750 μm, and 2.9 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1.

(Comparative Example 1)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 950 μm, 950 μm, and 1 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1. The difference (“BA”) between the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B is 0 μm, and the length A and the length B of the condition 1 Does not meet the preferred range of differences.

(Comparative Example 2)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 950 μm, 970 μm, and 1 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1. The difference (“BA”) between the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B is 20 μm, and the length A and the length B of the condition 1 Does not meet the preferred range of differences.

(Comparative Example 3)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 2900 μm, 2950 μm, and 3 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1. The length C of the negative electrode base material 23 is 3 mm, which does not satisfy the preferable range of the length C of the condition 2 and the suitable range of the lengths A and B of the condition 3.

(Comparative Example 4)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 2700 μm, 2850 μm, and 3 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1. The length C of the negative electrode base material 23 is 3 mm, which does not satisfy the suitable range of the length C of the condition 2.

(Comparative Example 5)
The length A of the first negative electrode mixture layer 21A from the base end 50, the length B of the second negative electrode mixture layer 21B from the base end 50, and the length C of the negative electrode base material 23 from the base end 50, respectively. It was set to 650 μm, 950 μm, and 1 mm. Other than that, a lithium ion secondary battery was prepared in the same manner as in Example 1. The difference between the length A of the first negative electrode mixture layer 21A and the length B of the second negative electrode mixture layer 21B (“BA”) is preferably the difference between the length A and the length B of the condition 1. Does not meet the above range.

(Evaluation)
The lithium ion secondary batteries containing the non-aqueous electrolytes of Examples 1 to 11 and Comparative Examples 1 to 5 were charged at 30 C and then discharged at 30 C. With this as one cycle, charging and discharging were repeated for 1000 cycles, and the presence or absence of lithium precipitation at the end of the positive electrode plate 15 was visually observed and observed with an electron microscope. Further, in order to confirm the insulating function of the separator 17, a high voltage insulation test was conducted in which a high voltage of 400 V was applied to a lithium ion secondary battery without a non-aqueous electrolyte and whether or not a current flowed was observed. The case where the precipitation of lithium was confirmed was evaluated as “x”, and the case where no precipitation was confirmed was evaluated as “〇”. In the high voltage insulation test, the case where no current flowed was evaluated as "○", and the case where current flowed was evaluated as "x".

In each of the secondary batteries of Examples 1 to 11, no lithium precipitation was confirmed and no current flowed in the high voltage insulation test, so the evaluation was set to "◯". On the other hand, in Comparative Examples 1 and 2, although lithium was not deposited, a current flowed in the high voltage insulation test, so the evaluation of the high voltage insulation test was set to “x”.

In Comparative Example 3, since the precipitation of lithium was confirmed and the current flowed in the high voltage insulation test, the evaluation of the precipitation of lithium and the high voltage insulation test was set to “x”. In Comparative Example 4, although there was no precipitation of lithium, a current flowed in the high voltage insulation test, so the evaluation of the high voltage insulation test was set to “x”. In Comparative Example 5, since the precipitation of lithium was confirmed and the current flowed in the high voltage insulation test, the evaluation of the precipitation of lithium and the high voltage insulation test was set to “x”.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-In the above embodiment, the electrode body 20 of the lithium ion secondary battery 10 satisfies all of the conditions 1 to 3, but at least one may be satisfied. When at least one of the conditions 1 to 3 is satisfied, it is possible to obtain an effect of suppressing damage to the separator 17 or an effect of suppressing the precipitation of lithium depending on the condition.

In the above embodiment, the negative electrode base material 23 is projected from the first negative electrode mixture layer 21A and the second negative electrode mixture layer 21B in the non-opposing portion 16C of the negative electrode plate 16. However, not limited to this, the length B of the second negative electrode mixture layer 21B is the same as the length C of the negative electrode base material 23, and the length A of the first negative electrode mixture layer 21A is made shorter than those lengths. You may do so.

-In the above embodiment, the lithium ion secondary battery has a wound structure in which the electrode body 20 is a flatly wound positive electrode plate and a long negative electrode plate via a long separator. It was explained as. However, the present invention is not limited to this, and a plurality of positive electrode plates and a plurality of negative electrode plates may be laminated alternately via a separator. Even in the laminated body, one end of the electrode body is pressed to form the positive electrode side current collecting portion 20A, and the other end of the electrode body is pressed to form the negative electrode side current collecting portion 20B. The same effect as that of the above embodiment can be obtained by shifting the tips of the first negative electrode mixture layer and the second negative electrode mixture layer at the tip of each negative electrode plate sandwiched between the connecting portions 15A of the positive electrode plates. it can.

-The lithium ion secondary battery 10 may be used in vehicles such as electric vehicles, hybrid vehicles, gasoline vehicles and diesel vehicles, and other moving bodies. Alternatively, it may be fixedly installed.

10 ... Lithium ion secondary battery, 11 ... Battery case, 12 ... Lid, 13 ... External terminal, 15 ... Positive electrode plate, 15A ... Connection part, 16 ... Negative electrode plate, 16A ... Connection part, 16B, 16C ... Non-opposing part , 16D ... opposed portion, 16Z ... non-opposed portion, 17 ... separator, 18 ... positive electrode base material, 19 ... positive electrode mixture layer, 20 ... electrode body, 20A ... positive electrode side current collecting part, 20B ... negative electrode side current collecting part, 21A ... 1st negative electrode mixture layer, 21B ... 2nd negative electrode mixture layer, 23 ... negative electrode base material, 50 ... base end, 51 ... positive electrode side current collecting member, 52 ... negative electrode side current collecting member.

Claims (3)

A positive electrode base material, a positive electrode mixture layer provided on both sides of the positive electrode base material, a positive electrode plate having a connecting portion which is a portion where the positive electrode mixture layer is not provided on both sides of the positive electrode base material, and a positive electrode plate.
The negative electrode base material, the first negative electrode mixture layer provided on one surface of the negative electrode base material, the second negative electrode mixture layer provided on the other surface of the negative electrode base material, the first negative electrode mixture layer and the second negative electrode mixture layer. A negative electrode plate having a connecting portion, which is a portion where the negative electrode mixture layer is not provided,
A separator provided between the positive electrode plate and the negative electrode plate is provided.
A positive electrode side current collecting portion including the connection portion of the positive electrode plate is provided at one end of the positive electrode plate, the negative electrode plate and the laminated body in which the separator is laminated, or the wound body in which the laminated body is wound. A lithium ion secondary battery having an electrode body provided with a negative electrode side current collecting portion including the connecting portion of the negative electrode plate at the other end.
The negative electrode plate is
The positive electrode plate has a facing portion facing the positive electrode mixture layer and a non-facing portion not facing the positive electrode mixture layer via the separator.
The tip of the first negative electrode mixture layer and the tip of the second negative electrode mixture layer in the non-opposing portion sandwiched between the connecting portions of the positive electrode plates are displaced in the direction toward the tip of the non-opposing portion. The first relative distance, which is the shortest distance between the base end of the non-opposing portion and the tip of the first negative electrode mixture layer, is the shortest distance between the base end of the non-opposing portion and the tip of the second negative electrode mixture layer. Shorter than the second relative distance, which is the distance,
The difference between the first relative distance and the second relative distance is in the range of 30 μm or more and less than 300 μm, and the first relative distance and the second relative distance are in a range larger than 0 mm and smaller than 2.9 mm. Lithium-ion secondary battery inside. The lithium ion secondary battery according to claim 1, wherein the tip of the negative electrode base material protrudes from the first negative electrode mixture layer and the second negative electrode mixture layer. The lithium ion secondary battery according to claim 1 or 2, wherein the third relative distance from the base end of the non-opposing portion to the tip end of the negative electrode base material is 0.3 mm or more and 3.0 mm or less.