Negative electrode plate and secondary battery

Abstract

To provide a negative electrode plate that can suppress damage to the negative electrode tab due to repeated charging and discharging. [Solution] The negative electrode active material layer 24 of the negative electrode plate 20 disclosed herein comprises a first region A1 in which the degree of planar orientation of carbon particles is 300 or more, and a second region A2 in which the degree of planar orientation of carbon particles is 200 or less. When the total length of the negative electrode active material layer 24 in the first direction D1 is L, the first region A1 extends from the first end 24a to the second end 24b of the negative electrode active material layer 24 for a length of 1 / 10L or more, and the second region A2 extends from the second end 24b to the first end 24a of the negative electrode active material layer 24 for a length of 8 / 10L or more. With this configuration, since the first region A1, which has a small amount of expansion and contraction in the planar direction, is adjacent to the negative electrode tab 26, damage to the negative electrode tab 26 due to repeated application of large stresses can be suppressed.

Description

[Technical Field]

[0001] The technology disclosed herein relates to a negative electrode plate and a secondary battery. [Background technology]

[0002] Secondary batteries, such as lithium-ion batteries, sometimes use a sheet-shaped negative electrode (negative electrode plate). This negative electrode plate comprises a negative electrode core, which is a conductive metal foil; a negative electrode active material layer applied to the surface of the negative electrode core; and a negative electrode tab protruding from one end of the negative electrode active material layer. The negative electrode tab is a region where the negative electrode active material layer is not applied and the negative electrode core is exposed. A conductive metal plate (negative electrode current collector) is connected to this negative electrode tab.

[0003] Patent Document 1 discloses an example of a negative electrode for a lithium-ion secondary battery. In the negative electrode described in Patent Document 1, graphite particles (negative electrode active material) are oriented along the thickness direction of the negative electrode composite layer (negative electrode active material layer). It has been confirmed that this improves battery performance, such as cycle characteristics. Patent Documents 2 and 3 disclose other examples of techniques for controlling the orientation of the negative electrode active material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-74286 [Patent Document 2] Japanese Patent Publication No. 2023-104840 [Patent Document 3] Japanese Patent Publication No. 2013-69432 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, as described in Patent Document 1, when the negative electrode active material is oriented along the thickness direction of the negative electrode active material layer, the negative electrode tab sometimes cracks when the secondary battery is repeatedly charged and discharged. The technology disclosed herein was developed to solve this problem and aims to provide a negative electrode plate that can suppress damage to the negative electrode tab due to repeated charging and discharging. [Means for solving the problem]

[0006] The negative electrode plate disclosed herein comprises a negative electrode core body which is a conductive metal foil, a negative electrode active material layer which is applied to the surface of the negative electrode core body and contains a negative electrode active material, and a negative electrode tab which protrudes outward from one end of the negative electrode active material layer in a first direction and is not covered by the negative electrode active material layer, exposing the negative electrode core body. The negative electrode active material of this negative electrode plate contains at least carbon particles. Furthermore, the negative electrode active material layer has a peak intensity of P in the (110) plane in the X-ray diffraction spectrum. 110 Peak intensity P of the (002) plane relative to the (002) plane 002 The ratio (P 002 / P 110 The negative electrode core, represented by ), comprises a first region where the degree of orientation of carbon particles relative to the surface is 300 or more, and a second region where the degree of orientation of carbon particles is 200 or less. When the total length of the negative electrode active material layer in the first direction is L, the first region extends from one end of the negative electrode active material layer toward the other end for a length of 1 / 10L or more, and the second region extends from the other end of the negative electrode active material layer toward the first end for a length of 8 / 10L or more.

[0007] The negative electrode active material layer of the negative electrode plate disclosed herein has two regions with different degrees of orientation of the negative electrode active material (carbon particles). As will be explained in more detail later, the "degree of orientation of carbon particles relative to the surface of the negative electrode core" in this specification refers to the degree of orientation along the planar direction (planar orientation), and therefore decreases as the number of negative electrode active material particles oriented along the thickness direction increases. That is, in the second region, where the planar orientation degree is 200 or less, the orientation of the negative electrode active material is controlled to face the thickness direction. This second region contributes to improving cycle characteristics, but has the characteristic of having a large amount of expansion and contraction in the planar direction during charging and discharging. On the other hand, in the first region, where the planar orientation degree is 300 or more, the orientation in the thickness direction is not controlled. This first region contributes relatively little to improving cycle characteristics, but has a small amount of expansion and contraction in the planar direction during charging and discharging. In the negative electrode plate disclosed herein, a first region of a certain size or larger is formed adjacent to the negative electrode tab. This prevents the area near the negative electrode tab from expanding and contracting significantly in the planar direction, thereby suppressing damage to the negative electrode tab due to expansion and contraction. Furthermore, in the negative electrode plate disclosed herein, a second region of sufficient size is formed away from the negative electrode tab. This allows for improvement of cycle characteristics and other properties without directly applying large stresses to the negative electrode tab. As described above, the technology disclosed herein makes it possible to suppress damage to the negative electrode tab due to repeated charging and discharging while maintaining high battery performance. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic plan view showing a negative electrode plate according to one embodiment. [Figure 2] Figure 2 schematically shows a negative electrode active material layer with a high degree of orientation of the negative electrode active material. [Figure 3] Figure 3 schematically shows a negative electrode active material layer with a low degree of orientation of the negative electrode active material. [Figure 4] Figure 4 is a schematic perspective view showing a secondary battery according to one embodiment. [Figure 5] Figure 5 is a view along the VV arrow in Figure 4. [Figure 6]FIG. 6 is a perspective view schematically showing an electrode body of a secondary battery according to an embodiment. [Figure 7] FIG. 7 is a view taken along the arrow VII-VII in FIG. 4. [Figure 8] FIG. 8 is a plan view for explaining a method of manufacturing a negative electrode plate according to an embodiment. [Figure 9] FIG. 9 is a perspective view schematically showing an electrode body of a secondary battery according to another embodiment. [Figure 10] FIG. 10 is a plan view schematically showing a negative electrode plate in FIG. 9. [Figure 11] FIG. 11 is a plan view schematically showing a negative electrode plate according to another embodiment. [Figure 12] FIG. 12 is a plan view schematically showing a negative electrode plate according to another embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. In addition, matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and the common technical knowledge in the relevant field. In addition, the notation "A to B" indicating a range in this specification includes the meaning of "preferably larger than A" and "preferably smaller than B" as well as the meaning of "A or more and B or less".

[0010] [Negative electrode plate] Hereinafter, an embodiment of the negative electrode plate disclosed herein will be described. FIG. 1 is a plan view schematically showing the negative electrode plate according to this embodiment. FIG. 2 is a schematic view for explaining the expansion and contraction of a negative electrode active material layer with a large degree of orientation of the negative electrode active material. FIG. 3 is a schematic view for explaining the expansion and contraction of a negative electrode active material layer with a small degree of orientation of the negative electrode active material. In FIGS. 1 to 3, the symbol D1 indicates the "first direction", the symbol D2 indicates the "second direction", and the symbol D3 indicates the "third direction".

[0011] As shown in Figure 1, the negative electrode plate 20 according to this embodiment is a long rectangular sheet extending in a first direction D1. That is, the first direction D1 in this embodiment is the longitudinal direction of the negative electrode plate 20. The second direction D2 is the short direction of the negative electrode plate 20. And the third direction D3 is the thickness direction of the negative electrode plate 20.

[0012] The negative electrode plate 20 according to this embodiment comprises a negative electrode core 22, a negative electrode active material layer 24, and a negative electrode tab 26. Each part will be described below.

[0013] 1. Negative electrode core The negative electrode core 22 is a conductive metal foil. Examples of materials for the negative electrode core 22 include copper and copper alloys. The thickness of the negative electrode core 22 is preferably 30 μm or less, more preferably 20 μm or less, and particularly preferably 15 μm or less. While making the negative electrode core 22 thinner contributes to improving the energy density of the secondary battery, it reduces the strength of the negative electrode tab 26. However, according to the technology disclosed herein, even when using a low-grade negative electrode core 22, damage to the negative electrode tab 26 during charging and discharging can be suppressed. That is, the technology disclosed herein is particularly suitable for negative electrode plates 20 with a negative electrode core 22 thickness of 30 μm or less. Furthermore, from the viewpoint of reliably preventing damage to the negative electrode tab 26, the thickness of the negative electrode core 22 is preferably 2.5 μm or more, more preferably 5 μm or more, even more preferably 6.0 μm or more, and particularly preferably 8.0 μm or more.

[0014] 2.Negative electrode active material layer The negative electrode active material layer 24 is applied to the surface of the negative electrode core 22. From the viewpoint of battery performance, it is preferable that the negative electrode active material layer 24 is applied to both sides of the negative electrode core 22. Furthermore, the thickness of the negative electrode active material layer 24 is preferably 50 μm or more, more preferably 80 μm or more, and particularly preferably 100 μm or more. As the thickness of the negative electrode active material layer 24 increases, the battery capacity tends to improve. On the other hand, the thickness of the negative electrode active material layer 24 is preferably 300 μm or less, more preferably 250 μm or less, and particularly preferably 200 μm or less.

[0015] The negative electrode active material layer 24 contains a negative electrode active material. In this embodiment, the negative electrode active material contains carbon particles C (see Figures 2 and 3). Since the carbon particles C are oriented along an external magnetic force, their orientation within the negative electrode active material layer 24 can be easily controlled. Examples of carbon particles C include graphite, hard carbon, soft carbon, amorphous carbon, etc. Another example of carbon particles C is core-shell particles in which the surface of graphite particles is coated with metal or amorphous carbon. The average aspect ratio of the carbon particles is preferably 1.1 or higher (preferably 1.1 to 1.7, more preferably 1.1 to 1.4, even more preferably 1.2 to 1.4, and particularly preferably 1.2 to 1.3). This allows the carbon particles to be easily oriented in a predetermined direction. In measuring this average aspect ratio, first, a cross-sectional SEM image of the negative electrode active material layer is acquired, and multiple (e.g., 50 or more) carbon particles are randomly extracted from the cross-sectional SEM image. Next, draw the smallest rectangle that circumscribes the extracted carbon particles, and measure the length of the shorter side a and the length of the longer side b of that rectangle. Then, calculate the aspect ratio (b / a), which is the ratio of the length of the shorter side a to the length of the longer side b. Finally, calculate the average aspect ratio by taking the arithmetic mean of the aspect ratios (b / a) of multiple carbon particles.

[0016] Furthermore, the negative electrode active material may contain silicon-based materials in addition to carbon particles C. Examples of such silicon-based materials include silicon and silicon oxide (silica). The silicon-based material may also contain other metallic elements (e.g., alkaline earth metals) or their oxides. However, from the viewpoint of orientation control, it is preferable that the negative electrode active material contains a certain amount of carbon particles C. Specifically, the content of carbon particles C relative to the total amount of negative electrode active material is preferably 80% by mass or more, more preferably 85% by mass or more, and particularly preferably 90% by mass or more. On the other hand, the upper limit of the carbon particle C content is not particularly limited and may be 100% by mass or less, 99% by mass or less, or 98% by mass or less.

[0017] Furthermore, the negative electrode active material layer 24 may contain additives other than the negative electrode active material. Examples of such additives include binders and thickeners. Examples of binders include rubber-based binders such as styrene-butadiene rubber (SBR). Examples of thickeners include carboxymethylcellulose (CMC). These organic components can improve the adhesion of the negative electrode active material layer 24 to the negative electrode core 22. The content of the negative electrode active material when the total solid content of the negative electrode active material layer 24 is taken as 100% by mass is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. This makes it possible to form a negative electrode active material layer 24 with excellent charge-discharge performance. On the other hand, considering the adhesion to the negative electrode core 22, the content of the negative electrode active material is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less.

[0018] In this specification, the total length of the negative electrode active material layer 24 in the first direction D1 is denoted as L. On the other hand, the total width of the negative electrode active material layer 24 in the second direction D2 is denoted as W. In this case, the ratio L / W of the total length L to the total width W of the negative electrode active material layer 24 is preferably 1.5 or more, more preferably 2 or more, even more preferably 2.5 or more, and particularly preferably 3 or more. Such a long negative electrode plate 20 has a smaller amount of expansion and contraction in the second direction D2, and can therefore more effectively exhibit the effects of the technology disclosed herein. On the other hand, the upper limit of the above ratio L / W is not particularly limited and may be 10 or less, 8 or less, 6 or less, or 4 or less.

[0019] 3. Negative electrode tab As shown in Figure 1, the negative electrode tab 26 protrudes outward (to the right in Figure 1) from one end (hereinafter referred to as "first end 24a") of the negative electrode active material layer 24 in the first direction D1. The negative electrode tab 26 is not covered by the negative electrode active material layer 24, and the negative electrode core 22 is exposed. As will be described in more detail later, this negative electrode tab 26 is connected to the negative electrode current collector 76 (see Figures 5 and 7) when constructing the secondary battery.

[0020] In this embodiment, the negative electrode tab 26 protrudes from a portion of the first edge 24a of the negative electrode active material layer 24. In other words, the width W1 of the negative electrode tab 26 in the second direction D2 is shorter than the total width W of the negative electrode active material layer 24. As will be described in detail later, this narrow negative electrode tab 26 can be easily bent when constructing a secondary battery, thus contributing to an improvement in the energy density of the secondary battery. On the other hand, the narrow negative electrode tab 26 is difficult to deform in accordance with the expansion and contraction of the negative electrode active material layer 24, making it prone to damage during charging and discharging. However, according to the technology disclosed herein, even when a narrow negative electrode tab 26 is formed, damage during charging and discharging can be sufficiently suppressed. The ratio W1 / W of the width W1 of the negative electrode tab 26 to the total width W of the negative electrode active material layer 24 is preferably 4 / 5 or less, more preferably 3 / 5 or less, even more preferably 2 / 5 or less, and particularly preferably 1 / 5 or less. On the other hand, the lower limit of the above ratio W1 / W is not particularly limited and may be 1 / 20 or greater, or 1 / 10 or greater.

[0021] 4. Orientation of the negative electrode active material layer In this embodiment, the negative electrode active material layer 24 of the negative electrode plate 20 has multiple regions with different degrees of orientation of carbon particles C relative to the surface of the negative electrode core 22 (hereinafter also referred to as "degree of planar orientation"). This makes it possible to suppress damage to the negative electrode tab 26 while maintaining high battery performance. This will be explained in detail below.

[0022] First, we will explain the "degree of planar orientation of carbon particles C" as used in this specification. Here, the "degree of planar orientation of carbon particles C" refers to the peak intensity P of the (110) plane in the X-ray diffraction spectrum. 110 Peak intensity P of the (002) plane relative to the (002) plane 002 Ratio P 002 / P 110It is as follows. The planar orientation degree of such carbon particles C is measured according to the following procedure. First, X-rays are irradiated along the thickness direction (the third direction D3 in FIGS. 2 and 3) of the negative electrode active material layer, and an X-ray diffraction spectrum is obtained based on JIS K 131-1996. Near 2θ = 25° of the X-ray diffraction spectrum at this time, a peak based on the (002) plane of the carbon particles C is confirmed. This peak of the (002) plane is detected when the X-rays are irradiated so as to intersect the long axis direction of the carbon particles C. On the other hand, near 2θ = 78° of the X-ray diffraction spectrum, a peak based on the (110) plane of the carbon particles C is confirmed. This peak of the (110) plane is confirmed when the X-rays are irradiated along the long axis direction of the carbon particles C. Therefore, as shown in FIG. 3, in the negative electrode active material layer having many carbon particles C oriented along the thickness direction (the third direction D3), the peak intensity P 110 of the (110) plane increases, so the planar orientation degree of the carbon particles (the above ratio P 002 / P 110 ) decreases. On the other hand, as shown in FIG. 2. In the negative electrode active material layer having many carbon particles C oriented in the planar direction (the first direction D1 or the second direction D2) along the surface of the negative electrode core 22, the peak intensity P 002 of the (002) plane increases, so the planar orientation degree of the carbon particles C increases.

[0023] Next, the relationship between the planar orientation degree of the carbon particles C and the breakage of the negative electrode tab 26 will be described. First, the carbon particles C have the property that they are difficult to expand and contract in the long axis direction and are easy to expand and contract in the short axis direction. Therefore, as shown in FIG. 3, when the long axis direction of the carbon particles C and the thickness direction of the negative electrode active material layer 24 are aligned, the expansion and contraction of the negative electrode active material layer 24 in the thickness direction can be suppressed. In addition, when the carbon particles C are oriented in the thickness direction, the electrolyte easily flows into the gaps between the carbon particles C (negative electrode active material). By these actions, the cycle characteristics and the like can be improved. However, when the carbon particles C are oriented in the thickness direction, since the planar direction (the first direction D1 and the second direction D2) and the short axis direction of the carbon particles C coincide, the amount of expansion and contraction of the negative electrode active material layer 24 in the planar direction becomes large. As a result, since a large stress is repeatedly applied to the negative electrode tab 26 adjacent to the negative electrode active material layer 24, the root 26a of the negative electrode tab 26 may be damaged.

[0024] In contrast, the negative electrode active material layer 24 of the negative electrode plate 20 according to this embodiment has a first region A1 and a second region A2 in which the orientation of carbon particles C differs. The first region A1 is a region in which the planar orientation of carbon particles C is 300 or more. In this first region A1, since the orientation of carbon particles C is not controlled, the direction of expansion and contraction of carbon particles C is dispersed, as shown in Figure 2. For this reason, the amount of expansion and contraction in the planar direction (first direction D1 or second direction D2) during charging and discharging is small in the first region A1. On the other hand, the second region A2 is a region in which the planar orientation of carbon particles C is 200 or less. As shown in Figure 3, in this second region A2, carbon particles C are oriented along the thickness direction D3. For this reason, the second region A2 contributes to improving cycle characteristics, etc., but has the characteristic of having a large amount of expansion and contraction in the planar direction.

[0025] As described above, the first region A1 has little expansion and contraction in the planar direction because the orientation of the carbon particles C is not controlled. In this embodiment, the first region A1 extends from the first edge 24a to the second edge 24b of the negative electrode active material layer 24 (from the right to the left in Figure 1) for a length of 1 / 10 L or more. In other words, in this embodiment, a first region A1 of a certain size or larger is formed adjacent to the negative electrode tab 26. This prevents large stresses from being repeatedly applied to the base 26a of the negative electrode tab 26 during charging and discharging, thereby suppressing damage to the negative electrode tab 26.

[0026] Next, in this embodiment, the second region A2 extends from the second edge 24b of the negative electrode active material layer 24 toward the first edge 24a (from left to right in Figure 1) for a length of 8 / 10L or more. In other words, in the negative electrode plate 20 according to this embodiment, a second region A2 of sufficient size is formed at a location away from the negative electrode tab 26. This makes it possible to improve cycle characteristics and the like without directly applying large stress to the negative electrode tab 26.

[0027] As described above, in the negative electrode plate 20 according to this embodiment, a first region A1 with a planar orientation degree of 300 or more is formed near the negative electrode tab 26, and a second region A2 with a planar orientation degree of 200 or less occupies most of the negative electrode active material layer 24 at a position away from the negative electrode tab 26. This makes it possible to sufficiently improve battery performance such as cycle characteristics and suppress damage to the negative electrode tab 26 due to repeated charging and discharging.

[0028] Furthermore, the degree of planar orientation in the first region A1 (the above intensity ratio P) 002 / P 110 The value of ) is preferably 310 or higher, more preferably 320 or higher, even more preferably 330 or higher, and particularly preferably 340 or higher. This further reduces the amount of expansion and contraction in the planar direction in the first region A1, thereby more effectively suppressing damage to the negative electrode tab 26. On the other hand, the upper limit of the degree of planar orientation in the first region A1 is preferably 600 or less, more preferably 500 or less, and particularly preferably 400 or less. This suppresses expansion and contraction in the thickness direction of the first region A1, thereby contributing to improvements in cycle characteristics, etc.

[0029] Furthermore, the degree of planar orientation in the second region A2 is preferably 190 or less, more preferably 180 or less, even more preferably 170 or less, and particularly preferably 160 or less. This further reduces the amount of expansion and contraction in the thickness direction (third direction D3) of the second region A2, thereby further improving the cycle characteristics of the secondary battery. On the other hand, if the degree of planar orientation in the second region A2 is made too small, a large difference in the amount of expansion and contraction in the planar direction will occur between the first region A1 and the second region A2. This may cause the negative electrode plate 20 to bend during charging and discharging. From this viewpoint, the degree of planar orientation in the second region A2 is preferably 105 or more, more preferably 110 or more, even more preferably 115 or more, and particularly preferably 120 or more.

[0030] The difference in the degree of planar orientation between the first region A1 and the second region A2 is preferably 400 or less, more preferably 390 or less, even more preferably 380 or less, and particularly preferably 370 or less. This effectively suppresses the deflection of the negative electrode plate 20 due to the difference in expansion and contraction between the first region A1 and the second region A2. On the other hand, the lower limit of the difference in the degree of planar orientation between the first region A1 and the second region A2 is not particularly limited and may be 100 or more, 200 or more, 250 or more, or 300 or more.

[0031] Furthermore, as shown in Figure 1, in the negative electrode plate 20 according to this embodiment, a third region A3 is formed between the first region A1 and the second region A2, having a plane orientation degree greater than 200 and less than 300. That is, the third region A3 has a plane orientation degree intermediate between the first region A1 and the second region A2. This prevents abrupt changes in the amount of expansion and contraction in the plane of the negative electrode active material layer 24, thereby more effectively preventing deflection of the negative electrode plate 20 during charging and discharging. Moreover, it is even more preferable that the plane orientation degree of the third region A3 gradually decreases from the first region A1 towards the second region A2. This further effectively prevents deflection of the negative electrode plate 20 during charging and discharging.

[0032] [Secondary battery] The negative electrode plate 20 according to this embodiment has been described above. Next, a secondary battery 100 using the negative electrode plate 20 with the above configuration will be described. In this specification, "secondary battery" refers to an energy storage device in general in which a charge-discharge reaction occurs through the movement of a charge carrier between a pair of electrodes (positive electrode and negative electrode) via an electrolyte. Below, a lithium-ion secondary battery will be described as an example of a secondary battery.

[0033] Figure 4 is a schematic perspective view of a secondary battery according to one embodiment. Figure 5 is a view taken along the VV arrow in Figure 4. Figure 6 is a schematic perspective view of the electrode body of a secondary battery according to one embodiment. Figure 7 is a view taken along the VII-VII arrow in Figure 4. Figure 8 is a side view illustrating a method for manufacturing a negative electrode plate according to one embodiment. In Figures 4 to 8, the symbol X indicates the "depth direction," the symbol Y indicates the "width direction," and the symbol Z indicates the "up and down direction." In the depth direction X, F indicates "front" and Rr indicates "back." In the width direction Y, L indicates "left" and R indicates "right." In the up and down direction Z, U indicates "up" and D indicates "down." However, these directions are defined for the convenience of explanation and are not intended to limit the installation configuration of the secondary battery.

[0034] As shown in Figures 4 to 8, the secondary battery 100 according to this embodiment comprises an electrode body 40 and a case 50. The following describes each component.

[0035] 1. Electrode body The electrode body 40 is a power generation element including a positive electrode plate 10 and a negative electrode plate 20. In this embodiment, the secondary battery 100 is equipped with three electrode bodies 40 (see Figure 7). However, the number of electrode bodies 40 is not particularly limited and may be one or multiple. Also, as shown in Figure 6, the electrode body 40 in this embodiment is a laminated electrode body. In this laminated electrode body 40, a rectangular sheet-shaped positive electrode plate 10 and a rectangular sheet-shaped negative electrode plate 20 are alternately stacked with a rectangular sheet-shaped separator 30 in between. The configuration of the electrode body 40 will be described in detail below.

[0036] (1) Positive plate As shown in Figure 6, the positive electrode plate 10 comprises a positive electrode core 12, a positive electrode active material layer 14, and a positive electrode tab 16. The positive electrode core 12 is a long metal foil extending in the width direction Y. The positive electrode active material layer 14 is applied to the surface of the positive electrode core 12. This positive electrode active material layer 14 contains positive electrode active material. The positive electrode tab 16 protrudes outward from the left end edge 14a of the positive electrode active material layer 14 in the width direction Y. The positive electrode tab 16 is not covered by the positive electrode active material layer 14, and the positive electrode core 12 is exposed. The materials of the constituent members of the positive electrode plate 10 can be conventionally known materials without particular limitation, and since this does not limit the technology disclosed herein, a detailed explanation is omitted.

[0037] (2) Negative plate In the secondary battery 100 according to this embodiment, the negative electrode plate 20 with the above configuration is used. Since the details of the negative electrode plate 20 have already been described, a redundant explanation will be omitted.

[0038] (3) Separator The separator 30 is an insulating sheet placed between the positive electrode plate 10 and the negative electrode plate 20. This separator 30 has the function of preventing contact between the positive electrode plate 10 and the negative electrode plate 20, while also allowing the charge carrier to pass through. An example of such a separator 30 is a resin sheet in which multiple fine holes are formed, through which the charge carrier can pass. The material of the separator 30 can be any conventionally known material without particular limitation, and since this does not limit the technology disclosed herein, a detailed explanation is omitted.

[0039] (4) Structure of the electrode As described above, the electrode body 40 according to this embodiment is a laminated electrode body in which positive electrode plates 10 and negative electrode plates 20 are alternately stacked with a separator 30 in between. In this electrode body 40, the components are stacked such that the positive electrode tabs 16 protrude from the left side L and the negative electrode tabs 26 protrude from the right side R. As a result, a group of positive electrode tabs 42, consisting of multiple stacked positive electrode tabs 16, is formed at the left end L of the electrode body 40 (see Figure 5). On the other hand, a group of negative electrode tabs 44, consisting of multiple stacked negative electrode tabs 26, is formed at the right end R of the electrode body 40. Furthermore, a core portion 46, consisting of a stacked positive electrode active material layer 14 and a stacked negative electrode active material layer 24, is formed in the center of the electrode body 40 in the width direction Y. This core portion 46 is the main site where the charge and discharge reactions occur. The number of each component constituting the electrode body 40 (number of stacks) is not particularly limited and can be increased or decreased as appropriate according to the dimensions of the secondary battery 100, etc.

[0040] 2. Case The case 50 is a housing for the electrode body 40. In this embodiment, the case 50 has a flat, bottomed rectangular parallelepiped (square) shape. The material of the case 50 is not particularly limited, and conventionally known materials can be used. Also, as shown in Figure 2, the case 50 comprises an outer casing 52 and a sealing plate 54. The outer casing 52 is a flat, square container with an opening 52h on its top surface. On the other hand, the sealing plate 54 is a plate-shaped member with a substantially rectangular planar shape. The case 50 is constructed by sealing the opening 52h on the top surface of the outer casing 52 with the sealing plate 54.

[0041] 3. Electrode terminal In this embodiment, a pair of electrode terminals (positive electrode terminal 60 and negative electrode terminal 70) are attached to the sealing plate 54 of the case 50. Each electrode terminal is connected to an electrode body 40 inside the case 50. A detailed explanation follows below.

[0042] First, the positive electrode terminal 60 is attached to one end (left side L in Figure 5) in the width direction Y of the sealing plate 54. This positive electrode terminal 60 comprises a positive electrode external terminal 62, a positive electrode internal terminal 64, and a positive electrode current collector member 66. The positive electrode external terminal 62 is a plate-shaped member located outside the case 50. The positive electrode internal terminal 64 is a conductive member that penetrates the case 50 (sealing plate 54). The upper end 64a of this positive electrode internal terminal 64 is connected to the positive electrode external terminal 62 outside the case 50. Next, the positive electrode current collector member 66 is a long plate-shaped member extending in the height direction Z. The upper end 66a of the positive electrode current collector member 66 is connected to the lower end 64b of the positive electrode internal terminal 64. The lower end 66b of the positive electrode current collector member 66 is also connected to the positive electrode tab group 42 (positive electrode tab 16) of the electrode body 40.

[0043] Furthermore, the negative electrode terminal 70 has the same configuration as the positive electrode terminal 60. Specifically, the negative electrode terminal 70 is attached to the other end (right side R in Figure 5) in the width direction Y of the sealing plate 54. The negative electrode terminal 70 comprises a negative electrode external terminal 72, a negative electrode internal terminal 74, and a negative electrode current collector member 76. The negative electrode external terminal 72 is a plate-shaped member located outside the case 50. The negative electrode internal terminal 74 is a conductive member that penetrates the case 50 (sealing plate 54). The upper end portion 74a of the negative electrode internal terminal 74 is connected to the negative electrode external terminal 72 outside the case 50. Next, the negative electrode current collector member 76 is a long plate-shaped member extending in the height direction Z. The upper end portion 76a of the negative electrode current collector member 76 is connected to the lower end portion 74b of the negative electrode internal terminal 74. Furthermore, the lower end portion 76b of the negative electrode current collector 76 is connected to the group of negative electrode tabs 44 (negative electrode tabs 26) of the electrode body 40.

[0044] Here, as shown in Figure 7, in this embodiment, the electrode body 40 is housed in the case 50 with the negative electrode tab 26 (negative electrode tab group 44) bent. Specifically, the negative electrode tab 26 is bent so that the negative electrode current collector 76 and the side surface of the electrode body 40 face each other. In this embodiment, similar to the negative electrode tab 26, the positive electrode tab 16 (positive electrode tab group 42) is also bent so that it faces the side surface of the electrode body 40. This allows the ratio of the width Y2 of the core portion 46 to the width Y1 inside the case 50 to be increased, which contributes to improving the energy density. On the other hand, when the negative electrode tab 26 is bent, stress is applied to the base 26a of the negative electrode tab 26 (see Figure 1). If the expansion and contraction of the negative electrode active material layer 24 near the negative electrode tab 26 is repeated in this state, the negative electrode tab 26 becomes even more susceptible to damage. However, in the negative electrode plate 20 according to this embodiment, the expansion and contraction of the negative electrode active material layer 24 (first region A1) near the negative electrode tab 26 is suppressed, thus preventing damage to the negative electrode tab 26. In other words, the negative electrode plate 20 according to this embodiment is particularly suitable for use in a secondary battery 100 having a configuration in which the negative electrode tab 26 is bent.

[0045] 4. Electrolyte Although not shown in the diagram, the case 50 also contains an electrolyte in addition to the electrode body 40. The electrolyte penetrates into the interior of the electrode body 40 (between the positive electrode plate 10 and the negative electrode plate 20). This allows the charge carrier to be moved between the positive electrode plate 10 and the negative electrode plate 20. The material of the electrolyte can be any conventionally known material without any particular limitations, and since this does not limit the technology disclosed herein, a detailed explanation is omitted.

[0046] The secondary battery 100 according to this embodiment has been described above. The secondary battery 100 includes a negative electrode plate 20 with the above configuration. As described above, the negative electrode active material layer 24 of the negative electrode plate 20 has a first region A1 in which the degree of planar orientation of carbon particles C is 300 or more, and a second region A2 in which the degree of planar orientation is 200 or less. The first region A1 extends from the first edge 24a to the second edge 24b of the negative electrode active material layer 24 with a length of 1 / 10L or more. The second region A2 extends from the second edge 24b to the first edge 24a of the negative electrode active material layer 24 with a length of 8 / 10L or more. This makes it possible to sufficiently improve the cycle characteristics of the secondary battery 100 and prevent the conduction path from being interrupted due to damage to the negative electrode tab 26.

[0047] [Manufacturing method for negative electrode plates] Next, the method for manufacturing the negative electrode plate 20 according to this embodiment will be described. This method for manufacturing the negative electrode plate 20 comprises a coating step, an orientation control step, a drying step, and a tab formation step. Figure 8 is a schematic plan view showing the method for manufacturing the negative electrode plate according to this embodiment.

[0048] As shown in Figure 8, in the coating process, a negative electrode slurry S containing negative electrode active material is applied to the surface of the negative electrode core 22, which is a conductive metal foil. This negative electrode slurry S is obtained by dispersing the components of the negative electrode active material layer described above in a liquid medium. Conventional coating equipment (gravure coater, comma coater, slit coater, die coater, etc.) can be used to apply this negative electrode slurry S. In this specification, the negative electrode core 22 to which the negative electrode slurry S has been applied is referred to as the "negative electrode precursor 200". In this embodiment, the negative electrode slurry S is not applied to one end of the negative electrode core 22 in the first direction (longitudinal direction) (the left end in Figure 8). This makes it possible to form an exposed region 210 where the negative electrode core 22 is exposed and a coated region 220 to which the negative electrode slurry S has been applied.

[0049] Next, in the orientation control step, the negative electrode precursor 200 is driven so that the coated area 220 of the negative electrode precursor 200 passes between a pair of magnets that are facing each other with a predetermined gap in the third direction D3 (thickness direction). As a result, the negative electrode active material (carbon particles) is oriented along the magnetic field formed between the pair of magnets.

[0050] In the negative electrode plate 20 shown in Figure 1, three regions are formed: a first region A1, a second region A2, and a third region A3. When manufacturing such a negative electrode plate 20, it is preferable to adopt the following procedure. First, as shown in Figure 8, in the manufacturing method according to this embodiment, a first magnet M11 and a second magnet M12 with different lengths in the first direction D1 are prepared. Here, the length of the first magnet M11 is 9 / 10 of the total length of the coated region 220 in the first direction D1. The length of the second magnet M12 is 8 / 10 of the total length of the coated region 220 in the first direction D1. Although not shown in the figure, the first magnet M11 and the second magnet M12 are a pair of magnets that face each other vertically with the negative electrode precursor 200 in between. Then, in the manufacturing method according to this embodiment, the first magnet M11 and the second magnet M12 are arranged along the second side 220b of the coated region 220. Then, as shown by the arrow in Figure 8, the negative electrode precursor 200 is moved along the second direction D2. As a result, the coated area 220 of the negative electrode precursor 200 has regions where both the first magnet M11 and the second magnet M12 have passed, regions where only the first magnet M11 has passed, and regions where neither the first magnet M11 nor the second magnet M12 has passed.

[0051] In the drying process, the negative electrode precursor 200 is heated to dry the coated region 220. This fixes the orientation direction of the negative electrode active material (carbon particles) within the coated region 220, and the negative electrode active material layer 24 is formed. At this time, in the orientation control process, the region that has passed through both the first magnet M11 and the second magnet M12 becomes the second region A2. The region that has passed through only the first magnet M11 becomes the third region A3. The region that has not passed through either the first magnet M11 or the second magnet M12 becomes the first region A1.

[0052] In the tab formation process, a portion of the exposed area 210 is removed. This forms a negative electrode tab 26 that protrudes outward from the first edge 24a of the negative electrode active material layer 24. As a result, the negative electrode plate 20 according to this embodiment, as shown in Figure 1, is manufactured. In the tab formation process, conventionally known cutting devices (lasers, cutting blades, etc.) can be used without particular limitation.

[0053] The above describes an example of a method for manufacturing the negative electrode plate 20 according to this embodiment. However, the negative electrode plate 20 according to this embodiment is not limited to that manufactured by the above-described manufacturing method. For example, a part of the negative electrode core may be cut off to form a negative electrode tab, and then the coating process to the drying process may be carried out. Also, as shown in Figure 11 which will be described later, when manufacturing a negative electrode 20B having only the first region A1 and the second region A2, it is sufficient to use only the second magnet M12 with a length corresponding to the second region A2 in the orientation control process. This makes it possible to manufacture a negative electrode 20B having only the first region A1 and the second region A2.

[0054] <Other Embodiments> The above describes one embodiment of the technology disclosed herein. The above embodiment is merely an example of how the technology disclosed herein may be applied and is not intended to limit the scope of the technology disclosed herein.

[0055] For example, in the above-described embodiment, a laminated electrode body is used as the electrode body. However, the electrode body is not limited to a laminated electrode body and does not need to include a positive electrode plate and a negative electrode plate. Another example of such an electrode body is a wound electrode body. As shown in Figure 9, the wound electrode body 40A is a wound laminate in which a positive electrode plate 10, a negative electrode plate 20, and a separator 30 are laminated. The technology disclosed herein can also be applied to a secondary battery using a wound electrode body 40A. In this wound electrode body 40A, rounded (R) portions are formed at both ends in the winding direction. In this case, the expansion and contraction of the negative electrode active material layer 24 during charging and discharging is restricted by the rounded portions, resulting in a force that causes deformation in the thickness direction. This may cause buckling of the negative electrode plate 20A. Considering this, the technology disclosed herein is preferably applied to a laminated electrode body in which each of the multiple negative electrode plates 20 is independent.

[0056] Furthermore, as shown in Figure 1, in the above-described embodiment, the longitudinal direction of the negative electrode plate 20 is defined as the first direction D1, and the short direction of the negative electrode plate 20 is defined as the second direction D2. However, in the technology disclosed herein, it is sufficient that the first region is adjacent to the negative electrode tab and the second region is spaced away from the negative electrode tab, and the definition of each direction is not limited. For example, Figure 10 shows a strip-shaped negative electrode plate 20A used in a wound electrode body 40A (see Figure 9). Multiple negative electrode tabs 26 protrude from one end of the negative electrode active material 24 in the short direction. The first region A1 extends from one end 24a to the other end 24b in the short direction of the negative electrode active material layer 24. The second region A2 extends from the other end 24b to the other end 24a in the short direction of the negative electrode active material layer 24. As described above, in the strip-shaped negative electrode plate 20A shown in Figure 10, the longitudinal direction of the negative electrode plate 20A is the second direction D2, and the transverse direction is the first direction D1. The technology disclosed herein can also be applied to a negative electrode plate 20 with such a configuration.

[0057] Furthermore, in the negative electrode plate 20 according to the above embodiment, a third region A3 is formed between the first region A1 and the second region A2. However, the third region A3 is not an essential component of the negative electrode disclosed herein. That is, the technology disclosed herein also includes a negative electrode plate 20B in which the first region A1 and the second region A2 are adjacent (see Figure 11). Even with a negative electrode plate 20B with such a configuration, it is possible to sufficiently improve battery performance such as cycle characteristics and suppress damage to the negative electrode tab 26 due to repeated charging and discharging. When the first region A1 and the second region A2 are adjacent, either the length of the first region A1 or the second region A2 may be extended. That is, the first region A1 can be formed in a range of 1 / 10L to 2 / 10L from the first edge 24a to the second edge 24b of the negative electrode active material layer 24. On the other hand, the second region A2 can be formed in a range of 8 / 10L to 9 / 10L from the second edge 24b to the first edge 24a of the negative electrode active material layer 24.

[0058] Furthermore, in the embodiments shown in Figures 1, 10, and 11, the boundaries of the first region A1 to the third region A3 extend approximately parallel to the second direction D2. However, the boundaries of each region may be inclined at an angle with respect to the second direction D2 (see Figure 12). Even with a negative electrode plate 20C configured in this way, if the lengths of the first region A1 and the second region A2 are appropriate, it is possible to sufficiently improve battery performance such as cycle characteristics while suppressing damage to the negative electrode tab 26. Note that if the boundaries of each region are inclined with respect to the second direction D2, the length of the first region A1 can be measured multiple times (for example, at 10 locations), and the average value can be taken as the "length of the first region." Similarly, the length of the second region A2 can be measured multiple times (for example, at 10 locations), and the average value can be taken as the "length of the first region."

[0059] The embodiments of the technology disclosed herein have been described above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. For example, the technology disclosed herein encompasses the embodiments described in the following sections.

[0060] <Item 1> The negative electrode core is a conductive metal foil, The surface of the aforementioned negative electrode core body is provided with a negative electrode active material layer containing a negative electrode active material, A negative electrode tab protrudes outward from one end of the negative electrode active material layer in the first direction, and is not provided with the negative electrode active material layer, and the negative electrode core is exposed. Equipped with, The negative electrode active material contains at least carbon particles, The aforementioned negative electrode active material layer is Peak intensity P of the (110) plane in the X-ray diffraction spectrum 110 Peak intensity P of the (002) plane relative to the (002) plane 002 Ratio P 002 / P 110 A first region in which the degree of orientation of the carbon particles with respect to the surface of the negative electrode core body represented by is 300 or more, A second region in which the orientation degree of the carbon particles is 200 or less It is equipped with, When the total length of the negative electrode active material layer in the first direction is L, the first region extends from one end of the negative electrode active material layer to the other end for a length of 1 / 10 L or more, and The second region is a negative electrode plate extending from the other end of the negative electrode active material layer toward the first end with a length of 8 / 10L or more.

[0061] <Item 2> The negative electrode plate described in item 1, wherein the average aspect ratio of the carbon particles is 1.1 or more and 1.7 or less.

[0062] <Item 3> The negative electrode plate according to item 1 or 2, wherein the degree of orientation in the first region is 600 or less.

[0063] <Item 4> A negative electrode plate according to any one of items 1 to 3, wherein the degree of orientation in the second region is 105 or more.

[0064] <Item 5> A negative electrode plate according to any one of items 1 to 4, wherein the difference between the degree of orientation in the first region and the degree of orientation in the second region is 400 or less.

[0065] <Item 6> A negative electrode plate according to any one of items 1 to 5, wherein a third region having an orientation degree greater than 200 and less than 300 is formed between the first region and the second region.

[0066] <Item 7> The negative electrode plate according to item 6, wherein the third region has a gradually decreasing degree of orientation from the first region to the second region.

[0067] <Item 8> The negative electrode tab protrudes from a portion of one end of the negative electrode active material layer, as described in any one of items 1 to 7.

[0068] <Item 9> The negative electrode plate according to item 8, wherein the ratio W1 / W of the width W1 of the negative electrode tab to the total width W of the negative electrode active material layer is 1 / 5 or less.

[0069] <Item 10> A negative electrode plate according to any one of items 1 to 9, wherein the ratio L / W of the total length L of the negative electrode active material layer to the total width W of the negative electrode active material layer is 3 or more.

[0070] <Item 11> A negative electrode plate according to any one of items 1 to 10, wherein the thickness of the negative electrode core is 30 μm or less.

[0071] <Item 12> An electrode body including a positive electrode plate and a negative electrode plate, A case for housing the electrode body and A secondary battery that includes, A secondary battery wherein the negative electrode plate is a negative electrode plate described in any one of items 1 to 11.

[0072] <Item 13> The secondary battery according to item 12, wherein the electrode body is a laminated electrode body in which rectangular sheet-shaped positive electrode plates and rectangular sheet-shaped negative electrode plates are alternately stacked with rectangular sheet-shaped separators in between.

[0073] <Item 14> The secondary battery according to item 12 or 13, wherein the electrode body is housed in the case with the negative electrode tab folded. [Explanation of Symbols]

[0074] 10 Positive plate 12 Positive electrode core 14 Cathode active material layer 16 Positive Tab 20 Negative electrode plates 22 Negative electrode core 24 Negative electrode active material layer 26 Negative Electrode Tabs 30 Separators 40 Electrode body 42 Positive electrode tab group 44 Negative electrode tab group 46 Core section 50 cases 52 Exterior 54 Sealing plate 60 Positive terminal 62 Positive external terminal 64 Positive internal terminal 66 Positive electrode current collector 70 Negative terminal 72 Negative external terminal 74 Negative internal terminal 75 Negative electrode current collector 76 Negative electrode current collector 100 Secondary battery A1 1st area A2 2nd area A3 Third area

Claims

1. The negative electrode core is a conductive metal foil, The surface of the aforementioned negative electrode core body is provided with a negative electrode active material layer containing a negative electrode active material, A negative electrode tab protrudes outward from one end of the negative electrode active material layer in the first direction, and is not provided with the negative electrode active material layer, and the negative electrode core is exposed. Equipped with, The negative electrode active material contains at least carbon particles, The aforementioned negative electrode active material layer is Peak intensity P of the (110) plane in the X-ray diffraction spectrum １１０ Peak intensity P of the (002) plane relative to the (002) plane ００２ Ratio P ００２ / P １１０ A first region in which the degree of orientation of the carbon particles with respect to the surface of the negative electrode core body represented by is 300 or more, A second region in which the orientation degree of the carbon particles is 200 or less It is equipped with, When the total length of the negative electrode active material layer in the first direction is L, the first region extends from one end of the negative electrode active material layer to the other end for a length of 1 / 10 L or more, and The second region is a negative electrode plate that extends from the other end of the negative electrode active material layer toward the first end with a length of 8 / 10 L or more.

2. The negative electrode plate according to claim 1, wherein the average aspect ratio of the carbon particles is 1.1 or more and 1.7 or less.

3. The negative electrode plate according to claim 1, wherein the degree of orientation in the first region is 600 or less.

4. The negative electrode plate according to claim 1, wherein the degree of orientation in the second region is 105 or more.

5. The negative electrode plate according to claim 1, wherein the difference between the degree of orientation in the first region and the degree of orientation in the second region is 400 or less.

6. The negative electrode plate according to claim 1, wherein a third region having an orientation degree greater than 200 and less than 300 is formed between the first region and the second region.

7. The negative electrode plate according to claim 6, wherein the degree of orientation in the third region gradually decreases from the first region toward the second region.

8. The negative electrode plate according to claim 1, wherein the negative electrode tab protrudes from a portion of one end of the negative electrode active material layer.

9. The negative electrode plate according to claim 8, wherein the ratio W1 / W of the width W1 of the negative electrode tab to the total width W of the negative electrode active material layer is 1 / 5 or less.

10. The negative electrode plate according to claim 1, wherein the ratio L / W of the total length L of the negative electrode active material layer to the total width W of the negative electrode active material layer is 3 or more.

11. The negative electrode plate according to claim 1, wherein the thickness of the negative electrode core is 30 μm or less.

12. An electrode body including a positive electrode plate and a negative electrode plate, A case for housing the electrode body and A secondary battery that includes, A secondary battery wherein the negative electrode plate is the negative electrode plate described in any one of claims 1 to 11.

13. The secondary battery according to claim 12, wherein the electrode body is a laminated electrode body in which rectangular sheet-shaped positive electrode plates and rectangular sheet-shaped negative electrode plates are alternately stacked with rectangular sheet-shaped separators in between.

14. The secondary battery according to claim 12, wherein the electrode body is housed in the case with the negative electrode tab folded.

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