Secondary battery and battery pack

Abstract

The present application provides a secondary battery and a battery pack with high life performance. According to an embodiment, a secondary battery includes: an outer packaging member; an electrode group housed in the outer packaging member and having a stacked structure including one electrode, another electrode, and a separator located at least between the one electrode and the another electrode; and an electrolyte housed in the outer packaging member, wherein at least one side of the one electrode protrudes relative to at least one side of the another electrode in a direction intersecting a stacking direction of the electrode group, and the electrode group satisfies the following formula (1). Ra2 > Ra1 (1), wherein in the formula (1), Ra2 is an arithmetic average roughness of an end portion of at least one side of the one electrode in the electrode group, and Ra1 is an arithmetic average roughness of an inside adjacent to the end portion of the electrode group.

Description

Technical Field

[0001] Embodiments of the present invention relate to secondary batteries and battery packs. Background Technology

[0002] For batteries using electrodes containing niobium-containing titanium oxide, increasing the battery size presents the challenge of reducing thermal uniformity due to surface deformation and waveform formation. This reduced thermal uniformity leads to decreased battery lifespan. Summary of the Invention

[0003] The purpose of this invention is to provide a rechargeable battery and battery pack with high lifespan performance.

[0004] According to an embodiment, a secondary battery is provided, comprising: Outer packaging components; An electrode assembly, housed within an outer packaging component, has a laminated structure comprising one electrode, another electrode, and at least a diaphragm located between the two electrodes; and The electrolyte is contained within the outer packaging component. Wherein, in the direction intersecting the stacking direction of the electrode group, at least one side of one electrode protrudes relative to at least one side of the other electrode, and the electrode group satisfies the following equation (1).

[0005] Ra2>Ra1 (1) In equation (1), Ra2 is the arithmetic mean roughness of the end of at least one side of the electrode assembly containing one electrode, and Ra1 is the arithmetic mean roughness of the interior of the electrode assembly adjacent to the end.

[0006] According to other embodiments, a battery pack having the secondary battery described above is provided.

[0007] The secondary battery constructed as described above can improve its lifespan performance. Attached Figure Description

[0008] Figure 1 This is a partial cross-sectional perspective view schematically illustrating an example of a secondary battery according to an embodiment.

[0009] Figure 2 It is Figure 1 The enlarged cross-sectional view of part A of the secondary battery shown.

[0010] Figure 3 It means Figure 1 A schematic plan view of the electrode assembly of the secondary battery shown.

[0011] Figure 4 It is Figure 3 The diagram shows a cross-sectional view of the electrode assembly cut along line IV-IV.

[0012] Figure 5 It means Figure 3 A three-dimensional diagram showing the relationship between a portion of the long side of the electrode assembly and its projected area.

[0013] Figure 6 It is a schematic representation of what will Figure 3 The diagram shows a cross-sectional view of the electrode assembly set on a fixture used for measuring arithmetic mean roughness.

[0014] Figure 7 It is a schematic representation Figure 3 A cross-sectional view of the arithmetic mean roughness measurement method for the electrode assembly shown.

[0015] Figure 8 It is a cross-sectional view schematically representing the definition of arithmetic mean roughness.

[0016] Figure 9 This is a cross-sectional view schematically illustrating another example of a two-cell embodiment.

[0017] Figure 10 It is a schematic representation Figure 9 A three-dimensional view of the electrode assembly of the secondary battery shown.

[0018] Figure 11 A is a schematic representation. Figure 10 The diagram shows a plan view of the electrode assembly.

[0019] Figure 11 B is a schematic representation of "will" Figure 10 The diagram shows a cross-sectional view of the electrode assembly after it has been cut along the thickness direction.

[0020] Figure 12 It is Figure 9 The cross-sectional view of the secondary battery shown is taken near the end face of the electrode assembly along the winding axis.

[0021] Figure 13 This is a side view schematically showing the state of the initial charging process in the manufacturing of a secondary battery according to an embodiment.

[0022] Figure 14 This is an exploded perspective view that schematically illustrates an example of a battery pack embodiment.

[0023] Figure 15 It means Figure 14 A block diagram of an example of the circuitry for the battery pack shown.

[0024] (Explanation of reference numerals in the attached image) 1: Electrode assembly; 1A: End; 1B: Interior; 2: Outer packaging component; 3: Positive electrode; 3a: Positive current collector; 3b: Positive active material layer; 3c: Positive current collector tab; 4: Separator; 5: Negative electrode; 5a: Negative current collector; 5b: Negative active material layer; 6: Positive terminal; 7: Negative terminal; 14: Bracket; 24: Adhesive tape; 31: Container; 32: Cap; 33: Protective sheet. 34: Printed Circuit Board; 35: Wiring; 100: Secondary Battery; 300: Battery Pack; 342: Positive Side Connector; 343: Negative Side Connector; 345: Thermistor; 346: Protection Circuit; 342a: Wiring; 343a: Wiring; 350: External Terminal for Power Supply; 352: Positive Side Terminal; 353: Negative Side Terminal; 348a: Positive Side Wiring; 348b: Negative Side Wiring Detailed Implementation

[0025] The inventors conducted in-depth research and discovered the following insights. When using current collectors with electrodes containing active materials such as niobium titanium oxide that undergo volume changes during charging and discharging, and using ductile materials such as aluminum or aluminum alloys to manufacture batteries with flat sections, the battery surface easily deforms into a wavy shape due to volume changes. As a result, the battery's heat dissipation during use, such as charging and discharging, decreases. Specifically, if the battery deforms into a wavy shape, for example, in the thickness direction, air gaps are created between the batteries when multiple batteries are housed in a casing to form a battery pack or battery bank, resulting in heat accumulation between the batteries. In-depth research was conducted on methods to reduce such wavy deformation, and it was found that if deformation is completely eliminated, the electrolyte retention at the battery's outer edge decreases, potentially reducing battery life. Further investigation revealed that the wavy deformation at the battery's outer edge caused by volume changes improves electrolyte retention and has a positive effect on battery life. That is, the surface roughness relative to the flat portion of the battery was determined, and it is preferable that the outer edge portion, located outside the flat portion, has a rougher surface than the surface roughness of the flat portion. The flat portion with a small surface roughness can ensure uniform heat distribution within the battery, thus ensuring battery life performance. On the other hand, the outer edge portion with a large surface roughness can improve electrolyte retention, thus improving battery life performance.

[0026] Hereinafter, embodiments will be described with reference to the accompanying drawings. Furthermore, common components are labeled with the same reference numerals in the embodiments, and repeated descriptions are omitted. Additionally, the drawings are schematic diagrams used to facilitate the explanation and understanding of the embodiments; their shapes, dimensions, proportions, etc., may differ from those of the actual device, but these can be appropriately modified with reference to the following description and known techniques.

[0027] (First Implementation) According to a first embodiment, a secondary battery is provided. The secondary battery includes an outer packaging component, an electrode assembly housed in the outer packaging component, and an electrolyte housed in the outer packaging component. The electrode assembly has a laminated structure comprising one electrode, another electrode, and at least a separator located between the one electrode and the other electrode. In a direction intersecting the lamination direction of the electrode assembly, at least one side of one electrode protrudes relative to at least one side of the other electrode. The electrode assembly satisfies the following equation (1).

[0028] Ra2>Ra1 (1) In equation (1), Ra2 is the arithmetic mean roughness of the end portion of at least one side of the electrode assembly containing one electrode, and Ra1 is the arithmetic mean roughness of the interior of the electrode assembly adjacent to the end portion.

[0029] Reference Figures 1-10 The secondary battery of the embodiment will be described. Figures 1-10 In the examples shown, a secondary battery is assumed to have one negative electrode and the other positive electrode. Furthermore, in each figure, the electrode stacking direction is set to be parallel to the z-axis. Surfaces intersecting the electrode stacking direction approximately perpendicularly are set to be parallel to the xy-plane.

[0030] Figure 1 and Figure 2 The secondary battery 100 shown has Figure 1 and Figure 2 Electrode group 1 shown Figure 1 The outer packaging component 2 and the electrolyte (not shown) are shown. The electrode assembly 1 and the electrolyte are housed within the outer packaging component 2. The electrolyte is held within the electrode assembly 1.

[0031] The outer packaging component 2 is formed of a laminate containing two resin layers and a metal layer between them. The outer packaging component 2 has an electrode assembly storage portion 2A and a sealing portion 2B adjacent to one long side and two short sides of the electrode assembly storage portion 2A. A thermoplastic resin layer is provided on the inner surface of the sealing portion 2B, and the sealing portion 2B is sealed by hot-melt bonding.

[0032] like Figure 2 As shown, electrode assembly 1 is a stacked (or layered) electrode assembly. The stacked electrode assembly 1 has a structure in which positive electrode 3 and negative electrode 5 are alternately stacked along the z-axis, with a separator 4 sandwiched between them. Electrode assembly 1 has a generally flat shape. The two surfaces of electrode assembly 1 that intersect the electrode stacking direction (thickness direction or z-axis direction) are the outermost layers. Figure 2 In this case, the outermost layer is the separator 4. The outermost layer is not limited to the separator 4; it can also be the positive electrode 3 or the negative electrode 5.

[0033] The electrode assembly 1 includes multiple positive electrodes 3. Each positive electrode 3 has a positive current collector 3a and a layer 3b containing positive active material supported on both sides of the positive current collector 3a. Additionally, the electrode assembly 1 includes multiple negative electrodes 5. Each negative electrode 5 has a negative current collector 5a and a layer 5b containing negative active material supported on both sides of the negative current collector 5a.

[0034] Each positive electrode 3's positive current collector 3a includes a portion on one side parallel to the x-axis direction that does not support the positive active material layer 3b on any surface. This portion functions as a positive current collector tab 3c. Multiple positive current collector tabs 3c are electrically connected to a strip-shaped positive terminal 6. The front end of the strip-shaped positive terminal 6 extends along the y-axis direction and is led out to the outside of the outer packaging component 2.

[0035] Additionally, although not shown in the diagram, the negative current collector 5a of each negative electrode 5 includes a portion on one side parallel to the x-axis direction where no negative active material layer 5b is supported on any surface. This portion functions as a negative current collector tab. The negative current collector tab is located on the opposite side of the electrode group 1 relative to the positive current collector tab 3c. The negative current collector tab is electrically connected to the strip-shaped negative terminal 7. The front end of the strip-shaped negative terminal 7 extends along the y-axis direction opposite to that of the positive terminal 6 and is led out to the outside of the outer packaging component 2.

[0036] like Figure 2 As shown, in an extension direction parallel to the y-axis of the positive electrode 6 (denoted as the first direction y1), one side of the negative electrode active material layer 5b protrudes in the first direction y1 relative to the side of the positive electrode active material layer 3b. Figure 3 As shown, the remaining three sides of the negative electrode active material layer 5b, specifically one side facing the second direction y2 opposite to the first direction, and the two sides parallel to the x-axis direction, protrude relative to their respective sides of the positive electrode active material layer 3b. The sides of the separator (not shown) protrude from the four sides of the negative electrode active material layer 5b. It should be noted that... Figure 3 In the plan view of electrode group 1 shown, the current collectors, current collector tabs, and diaphragms of the positive and negative electrodes are omitted.

[0037] like Figures 3 to 5 As shown, the two sides 51 of the negative electrode 5, which are parallel to the y-axis direction, have a wavy or uneven shape in the electrode stacking direction (thickness direction or z-axis direction) of the electrode group 1. Figure 5 A schematic perspective view showing one of the two sides 51 of the negative electrode 5 that are parallel to the y-axis. The two sides of the diaphragm 4 that are in contact with these two sides are deformed in a wavy or convex shape along the negative electrode 5.

[0038] As described above, in the electrode assembly 1, in a direction that intersects or is substantially perpendicular to the electrode stacking direction (thickness direction or z-axis direction), the four sides of the negative electrode active material layer 5b protrude relative to the four sides of the corresponding positive electrode active material layer 3b. Furthermore, each side of the corresponding separator 4 protrudes relative to the four sides of the negative electrode active material layer 5b. The portion extending inward from any side of the negative electrode 5 at a distance L1 is defined as the end 1A of the electrode assembly 1. The portions extending inward from each of the four sides of the negative electrode 5 at a distance L1 are defined as the outer edges of the electrode assembly 1. The distance L1 can be, for example, 3 mm. Figure 5 As shown, the two sides 51 of the negative electrode 5, parallel to the y-axis, are wavy in three dimensions. Therefore, the projected area is used at the edges of the negative electrode 5 at a specified distance L1. (Refer to...) Figure 5 A detailed explanation follows. The distance L1 is the distance from the outline of the projected area 52 observed when viewing the edge 51 of the negative electrode 5 from the vertical direction (z-axis direction). Figure 5 In the example, the projected area 52 is rectangular. Therefore, the long side of the projected area 52 (the two sides in the y-axis direction) that corresponds to the outer edge of the side 51 of the negative electrode 5 becomes the starting point of the distance L1. Furthermore, regarding the interior 1B of the electrode assembly 1, as... Figure 4 As shown, in the portion defined by the two surfaces intersecting the stacking direction of the electrode assembly 1 (in this example, the outermost layer formed by the diaphragm 4), the portion enclosed by the outer edge is designated as the interior 1B of the electrode assembly 1. The interior 1B of the electrode assembly 1 is also called the flat portion.

[0039] Electrode group 1 satisfies equation (1).

[0040] Ra2>Ra1 (1) The end 1A of the electrode assembly 1 includes the edge of the negative electrode 5 exposed from the positive electrode 3. The edge of the negative electrode 5 exposed from the positive electrode 3 is difficult to be constrained by the positive electrode 3. Therefore, if an active material capable of volume change through charging and discharging is used in the negative electrode 5, and a malleable current collector is used, the negative electrode 5 exposed from the positive electrode 3 is prone to deformation through the charging and discharging reaction. By making the arithmetic mean roughness Ra2 of the end 1A of the electrode assembly 1 greater than the arithmetic mean roughness Ra1 of the interior 1B of the electrode assembly 1, the electrolyte retention of the end 1A of the electrode assembly 1 can be improved while ensuring the flatness of the interior 1B of the electrode assembly 1. This improves the lifespan performance of the secondary battery.

[0041] Furthermore, using multiple secondary batteries to construct a battery pack or battery module can suppress the formation of air gaps between the batteries, thus reducing heat accumulation between them. This improves the uniformity of battery heat distribution, resulting in improved battery lifespan. Additionally, it reduces energy density loss caused by air gaps between batteries, enabling the development of high-energy-density battery packs and modules.

[0042] The ratio (Ra2 / Ra1) of the electrode assembly is preferably 1.5 or higher. The electrode assembly is further preferably satisfied with the following formula (2).

[0043] Ra2 / Ra1≥3 (2) By satisfying equation (2) with the electrode assembly, the lifespan performance of the secondary battery, battery pack, and battery module can be further improved. Furthermore, the upper limit of the ratio (Ra2 / Ra1) is preferably set to 7.5, and more preferably to 5.0. A more preferred range for Ra2 / Ra1 is 1.5 or more and 7.5 or less, and more preferably 1.5 or more and 5.0 or less.

[0044] The arithmetic mean roughness Ra2 preferably satisfies the following equation (3).

[0045] Ra2≥d a (3) In equation (3), d a This refers to the thickness of the negative electrode. The thickness d of the negative electrode... a The measurement method is described below. When the negative electrode is assembled in the battery, the negative electrode is removed from the battery, for example, as described below. First, the battery is discharged to 0.0V, reaching an over-discharge state. Next, the battery is disassembled in an argon-filled glove box, and the negative electrode is removed. The thickness of the negative electrode is measured using a film thickness gauge.

[0046] By satisfying equation (3) with an arithmetic mean roughness Ra2, the electrolyte retention of the end 1A of electrode assembly 1 can be improved.

[0047] When the outer packaging component 2 is made of laminated film, it is preferable to satisfy the following formula (4).

[0048] R2cell>R1cell (4) In equation (4), R2cell is the arithmetic mean roughness of at least one end of the widest (or broadest) face of the secondary battery, and R1cell is the arithmetic mean roughness of the interior of the widest (or broadest) face of the secondary battery. Figure 1 and Figure 2In the case of the secondary battery 100 shown, the widest surface (widest surface) of the secondary battery corresponds to the bottom surface (xy plane) of the battery storage portion 2A of the outer packaging component 2, excluding the sealing portion 2B. Furthermore, when the electrode assembly 1 has a stacked structure, the arithmetic mean roughness R2cell is preferably the arithmetic mean roughness of the four ends of the bottom surface of the battery storage portion 2A of the outer packaging component 2. On the other hand, when the electrode assembly 1 has a wound structure, the arithmetic mean roughness R2cell is preferably the arithmetic mean roughness of the two ends of the bottom surface of the battery storage portion 2A of the outer packaging component 2 in the winding axis direction (y-axis direction).

[0049] The interior of the widest face (the widest part) of a secondary battery is the section enclosed by four ends. Figure 1 and Figure 2 In the case of the secondary battery shown, the part is formed by the four ends of the bottom surface of the battery storage section 2A of the outer packaging component 2.

[0050] When the outer packaging component 2 is made of laminated film, the lifespan performance of the secondary battery, battery pack, and battery module can be further improved by satisfying equation (4). To further improve lifespan performance, when the outer packaging component 2 is made of laminated film, the ratio (R2cell / R1cell) is preferably 1.5 or higher, and more preferably satisfies the following equation (5). The upper limit of the ratio (R2cell / R1cell) is preferably set to 7.5, and more preferably to 5.0. The more preferably R2cell / R1cell range is 1.5 or higher and 7.5 or lower, and more preferably 1.5 or higher and 5.0 or lower.

[0051] R2cell / R1cell≥3 (5) In addition, the internal arithmetic mean roughness R1cell preferably satisfies the following equation (6).

[0052] R1cell≤0.02d c (6) In equation (6), d c This refers to the thickness of the secondary battery. The thickness d of the secondary battery... c The measurement method is explained below. The secondary battery is discharged to the lower limit of its nominal voltage range at a rate below 0.05C, and the battery thickness is measured at the point where the state of charge (SOC) reaches 0. In cases where in-plane thickness deviations occur due to deformation of outer packaging components, the thinnest point is defined as the battery thickness. A stylus-type thickness gauge is preferably used for measurement.

[0053] By ensuring that the internal arithmetic mean roughness R1cell satisfies equation (6), the flatness of the widest surface (or the widest surface) of the outer packaging component 2 can be improved. This improves the flatness of the secondary battery, thereby further enhancing its thermal uniformity. Consequently, the lifespan performance of the secondary battery, battery pack, and battery module can be further improved.

[0054] It should be noted that, in Figures 1-5 In the structure, in the direction intersecting the stacking direction of the electrodes, each of the four sides of the negative electrode active material layer 5b protrudes relative to the corresponding four sides of the positive electrode active material layer 3b, but this structure is not limited to this. The protruding side can be only one side, or it can be two or three sides. In addition, the protruding side may not be the negative electrode 5, but the positive electrode 3.

[0055] <Method for determining arithmetic mean roughness> Reference Figures 6-8 The method for determining the arithmetic mean surface roughness is explained. Figure 6 and Figure 7 In this configuration, the electrode stacking direction (thickness direction) of electrode group 1 is set to be parallel to the z-axis. The extension directions of the positive and negative terminals 6 and 7 are set to be parallel to the y-axis. The direction that intersects the extension directions of the positive and negative terminals 6 and 7 approximately perpendicularly is set to be parallel to the x-axis.

[0056] The method for measuring the arithmetic mean roughness Ra2 of the end 1A of electrode assembly 1 is described.

[0057] First, the electrode assembly 1 is removed from the secondary battery 100. At this time, to avoid damage to the edges of the electrodes and to prevent affecting the thickness of the electrode assembly, the electrode assembly is separated by cutting open only the outer packaging of the battery. Two parallel plates 10 and 12 are used as measuring fixtures. The upper plate 10 is placed on one of the two surfaces of the electrode assembly 1 that intersect the electrode stacking direction (z-axis direction), and the lower plate 12 is placed on the other surface 1D. On the upper plate 10, a slit 11 is provided at a position corresponding to the distance L2 from the edge (profile) of the surface 1C of the electrode assembly 1, extending along the thickness direction (z-axis direction) of the plate and parallel to the long side direction (y-axis direction) of the plate. The distance L2 can be set to, for example, 1 mm. Here, the edge (profile) of the surface 1C of the electrode assembly 1 is determined by the profile defined by the projected area (excluding the separator) observed when viewing the surface 1C from the vertical direction. To prevent deformation of the electrode assembly 1, the upper plate 10 and the lower plate 12 are used to clamp and constrain the electrode assembly 1 with a pressure of 10 kPa or less. In this state, if the stylus 13 of the stylus-type thickness gauge is inserted into the slit 11 and brought into contact with the surface 1C of the electrode assembly 1, the height of this position from the lower plate 12 is measured as the surface roughness Ra. By moving the stylus 13 within the slit 11 along the y-axis, the surface roughness Ra of one side of the electrode assembly 1 parallel to the y-axis is measured. The length of this side is used as the reference length Ir to obtain the arithmetic mean roughness Ra. A diagram schematically showing the relationship between the surface roughness Ra, the arithmetic mean roughness Ra, and the reference length Ir is used as... Figure 8 And shown.

[0058] The reference length Ir varies depending on the length of the object whose surface roughness Ra is being measured. For example, when measuring the surface roughness Ra on both sides of electrode assembly 1, the sum of the lengths of both sides is taken as the reference length Ir.

[0059] Next, the method for measuring the arithmetic mean roughness Ra1 of the interior 1B of electrode assembly 1 will be explained.

[0060] In surface 1C or 1D of electrode assembly 1, the outer edge is defined as extending 3 mm inward from the quadrilateral. The portion enclosed by the outer edge is defined as the interior (also called the flat portion). The quadrilateral of each of surfaces 1C and 1D defines the outline of the projected area (excluding the diaphragm) observed when viewing each surface from a vertical direction. (The reference...) Figure 5The position of the slit 11 of the parallel plates 10 and 12 is changed to expose the interior of the electrode assembly 1. Another measuring fixture with the same structure as the parallel plates 10 and 12 is prepared. The electrode assembly 1 is clamped between the upper and lower plates of the other measuring fixture and constrained with a pressure of less than 10 kPa. The interior of surface 1C of the electrode assembly 1 is located at the slit of the upper plate. This interior (flat portion) 200 is divided into equal parts, and the stylus 13 of the stylus thickness gauge is brought into contact with the center of the diagonal of each section to calculate the surface roughness Ra. The average value of the obtained surface roughness Ra is taken as the arithmetic mean roughness Ra1.

[0061] The arithmetic mean roughness R2cell at at least one end of the widest face (or the widest surface) of the secondary battery, and the arithmetic mean roughness R1cell inside the widest face (or the widest surface) of the secondary battery, are measured using the secondary battery 100 instead of electrode group 1. The method for determining the profile of the widest face is the same as the method described in electrode group 1. Furthermore, the methods for measuring the arithmetic mean roughness at each end and inside the widest face are the same as the methods described in electrode group 1.

[0062] <End and interior of the wound electrode assembly> exist Figures 1 to 8 The example described uses a stacked electrode assembly, but the secondary battery of this embodiment is not limited to a stacked electrode assembly and can be applied to a wound electrode assembly. An example of a secondary battery having a wound electrode assembly is shown below. Figures 9 to 13 .

[0063] Figure 9 The secondary battery 100 shown includes a pouch-shaped outer packaging component 2, an electrode assembly 1, and an electrolyte (not shown). The electrode assembly 1 and the electrolyte are housed within the pouch-shaped outer packaging component 2. The electrolyte (not shown) is held within the electrode assembly 1. The thickness direction (the electrode stacking direction) of the secondary battery 100 is set to be parallel to the z-axis direction. The winding axis direction of the electrode assembly is set to be parallel to the y-axis direction. A direction that intersects the winding axis direction approximately perpendicularly is set to be parallel to the x-axis direction.

[0064] The bag-shaped outer packaging component 2 is formed of a laminated film comprising two resin layers and a metal layer between them. A thermoplastic resin layer is provided on the inner surface of the bag-shaped outer packaging component 2, and the opening is sealed by hot-melting and bonding it.

[0065] like Figure 10 As shown, electrode assembly 1 is a flat, wound electrode assembly. The flat, wound electrode assembly 1 includes a positive electrode 3, a separator 4, and a negative electrode 5. The separator 4 is located between the positive electrode 3 and the negative electrode 5. Figure 10For convenience, the diagrams of the positive electrode 3, diaphragm 4, negative electrode 5, and positive and negative terminals 6 and 7 are omitted. The end 1A and the interior (flat portion) 1B of the wound electrode assembly 1 will be described. Figure 10 The widest surface of the illustrated wound electrode assembly 1 corresponds to a flat surface 61 intersecting the thickness direction (z-axis direction). Furthermore, the wound electrode assembly 1 has end faces 63 on both sides of the winding axis direction 62 (y-axis direction). Each end face 63 has a flat helical shape. The definition of the outer edge of the widest surface will be explained. Figure 11 The outline of the projected area 64 (excluding the diaphragm and positive and negative electrode collector tabs) observed when viewed vertically from the widest surface, as shown in Figure A, is defined as the outer edge of the widest surface. The range from the two sides 65 parallel to the x-axis direction (intersecting the winding axis direction 62) to a distance L4 in the outline of the projected area 64 is the end 1A of the wound electrode assembly 1. Preferably, the distance L4 is 3 mm.

[0066] like Figure 11 A and Figure 11 As shown in Figure B, the interior (flat portion) 1B of the wound electrode assembly 1 is the area within the projected area 64 corresponding to the turn diameter L3, excluding the two ends 1A. The turn diameter L3 corresponds to the thickness of the wound electrode assembly 1. The method for measuring the thickness of the wound electrode assembly will be explained. When the wound electrode assembly is assembled in a battery, the electrode assembly is removed from the battery, for example, as follows: First, the battery is discharged to 0.0V to achieve a fully discharged state. Next, the battery is disassembled in a glove box filled with argon, and the electrode assembly is removed. The thickness of the electrode assembly is measured using a stylus-type thickness gauge. In cases where the in-plane thickness deviates due to deformation of the outer packaging components, the thinnest point is defined as the thickness of the battery.

[0067] Figure 12 It is Figure 10 The image shows a cross-sectional view taken along the y-axis near one end face (helical surface) of electrode assembly 1. Figure 12 For simplicity, the positive and negative extremes 6 and 7 are not illustrated. For example... Figure 12 As shown, the positive electrode 3 includes a positive current collector 3a and positive active material layers 3b supported on both sides of the positive current collector 3a. The positive current collector 3a of the positive electrode 3 has a portion on either side (the portion intersecting the y-axis) where no positive active material layer 3b is supported on either surface. This portion functions as a positive current collector tab 3c.

[0068] The negative electrode 5 has a negative current collector 5a and negative active material layers 5b supported on both sides of the negative current collector 5a. The negative current collector 5a of the negative electrode 5 includes portions on both long sides (the sides intersecting the y-axis) where neither surface is supported by a negative active material layer 5b. This portion functions as a negative current collector tab 5c.

[0069] like Figure 12 As shown, in electrode assembly 1, at one end along the winding axis (y-axis direction), the positive electrode collector 3c protrudes in the y-axis direction (let's call it the third direction y3) in a flattened spiral shape. Although the diagram is omitted, at the other end along the winding axis (y-axis direction), the negative electrode collector 5c (not shown) protrudes in the y-axis direction (let's call it the fourth direction y4) in a flattened spiral shape, facing the opposite direction to the first direction. The positive electrode collector 3c is electrically connected to the strip-shaped positive terminal 6. On the other hand, the negative electrode collector 5c is electrically connected to the strip-shaped negative terminal (not shown). Figure 9 The front end of the strip-shaped positive terminal 6 shown extends along the third direction y3 and is led out to the outside of the outer packaging component 2.

[0070] like Figure 12 As shown, at one end of the electrode assembly 1 along the winding axis direction (third direction y3), the separator 4, the negative electrode active material layer 5b, and the positive electrode active material layer 3b are sequentially located further inward than the positive electrode current collector 3c. Furthermore, although not shown in the diagram, at the other end of the electrode assembly 1 along the winding axis direction (fourth direction y4), the separator 4, the negative electrode active material layer 5b, and the positive electrode active material layer 3b are sequentially located further inward than the negative electrode current collector 5c. Additionally, the separator 4, negative electrode 5, and positive electrode 3 are all wound into a flattened spiral shape. At both ends of the electrode assembly 1 along the winding axis direction (y-axis direction), each long side of the negative electrode active material layer 5b protrudes relative to the corresponding long side of the positive electrode active material layer 3b. Therefore, the outline of the projected area of ​​the negative electrode active material layer 5b lies at the outline of the projected area 64.

[0071] In a secondary battery equipped with a wound electrode assembly 1, the lifespan performance can also be improved by satisfying equation (1) with the electrode assembly 1. It should be noted that the arithmetic mean roughness Ra2 of the end 1A and the arithmetic mean roughness Ra1 of the interior (flat portion) 1B of the wound electrode assembly 1 can be measured using the method described above.

[0072] Examples of secondary batteries include lithium secondary batteries, sodium secondary batteries, and non-aqueous electrolyte secondary batteries containing non-aqueous electrolytes.

[0073] The following provides a detailed description of the negative electrode, positive electrode, electrolyte, separator, outer packaging components, negative terminal, and positive terminal.

[0074] 1) Negative electrode The negative electrode may comprise a negative current collector and a layer containing a negative active material. The layer containing the negative active material may be formed on one or both sides of the negative current collector. The layer containing the negative active material contains the negative active material. The layer containing the negative active material may include conductive agents and binders as arbitrary components.

[0075] The negative current collector may be in the form of a plate, foil, or sheet. It may have a porous structure. Preferably, the negative current collector is made of copper, copper alloy, nickel, stainless steel, or aluminum, or an aluminum alloy. The aluminum alloy preferably contains one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The materials constituting the negative current collector may be one or more.

[0076] The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector with this thickness can achieve a balance between electrode strength and lightweight design.

[0077] Additionally, the negative current collector can be included in the portion of its surface where no layer of negative active material is formed. This portion can function as a negative current collector tab.

[0078] Examples of anode active materials include metals, nonmetals, alloys, oxides, sulfides, phosphides, oxysulfides, phosphoric acid, sulfuric acid compounds, and carbon materials. There can be one or more types of anode active materials.

[0079] Lithium is an example of a metal.

[0080] Silicon is an example of a nonmetal.

[0081] Examples of alloys include Sn alloys and Zn-containing alloys.

[0082] Examples of oxides include oxides containing at least one selected from titanium, niobium, tungsten, molybdenum, vanadium, iron, tin, and silicon. Specific examples include niobium oxides, titanium dioxide (TiO2), Fe2O3, and Li / Na oxides. x Ti / Nb y O z , silicon dioxide. Niobium oxides include niobium pentoxide (Nb₂O₅), Nb 12 O 29 FeNb 11 O 29 Monoclinic titanium niobium oxide (TNO), tetragonal titanium-niobium-tungsten composite oxide, and tetragonal titanium-niobium-molybdenum composite oxide, etc.

[0083] Examples of sulfides include FeS, CoS, and MoS2.

[0084] Examples of carbon materials include hard carbon black and graphite.

[0085] As examples of the aforementioned monoclinic niobium titanium oxides, Li can be cited as an example. x Ti1-y M1 y Nb 2-z M2 z O 7+δ The compound is indicated by M1, which is at least one selected from Zr, Si, and Sn. M2 is at least one selected from V, Ta, and Bi. The subscripts in the composition formula are 0 ≤ x ≤ 5, 0 ≤ y < 1, 0 ≤ z < 2, and -0.3 ≤ δ ≤ 0.3. As a specific example of a monoclinic niobium titanium oxide, Li can be cited. x Nb2TiO7 (0≤x≤5).

[0086] Other examples of monoclinic niobium titanium oxides include those based on Li x Ti 1-y M3 y+z Nb 2-z O 7-δ The compound is indicated by M3. Here, M3 is selected from at least one of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≤x≤5, 0≤y<1, 0≤z<2, and -0.3≤δ≤0.3.

[0087] Additionally, as examples of other oxides, lithium titanate (e.g., Li) with an orthorhombic manganese oxide structure can be cited. 2+ y Ti3O7, 0≤y≤3), lithium titanate with spinel structure (e.g., Li), 4+x Ti5O 12 (0≤x≤3), titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, manganese barite titanium composite oxide, and orthorhombic titanium composite oxide.

[0088] As examples of the orthorhombic titanium-containing composite oxides mentioned above, Li can be cited. 2+a M I 2-b Ti 6-c M II d O 14+σ The compound represented. Here, M I It is selected from at least one of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M II It is selected from at least one of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0 ≤ a ≤ 6, 0 ≤ b < 2, 0 ≤ c < 6, 0 ≤ d < 6, and -0.5 ≤ σ ≤ 0.5. As a specific example of an orthorhombic titanium-containing composite oxide, Li can be cited. 2+a Na2Ti6O 14(0≤a≤6).

[0089] As the negative electrode active material, it is preferable to include at least one first negative electrode active material selected from niobium oxide, hard carbon black, and graphite. When using the first negative electrode active material, the negative electrode current collector is preferably a first negative electrode current collector containing at least one of aluminum or an aluminum alloy. The first negative electrode active material expands and contracts during charging and discharging. Furthermore, the first negative electrode current collector is malleable. If at least one side of the negative electrode, which includes the first negative electrode active material and the first negative electrode current collector, is exposed from the positive electrode, it is prone to deformation due to volume changes caused by the charging and discharging reaction. Therefore, by ensuring that the arithmetic mean roughness relationship meets the range specified in this invention, lifespan performance can be reliably improved.

[0090] Furthermore, as the negative electrode active material, a second negative electrode active material selected from at least one of metals, non-metals, and alloys is preferred. When using a second negative electrode active material, the negative electrode current collector is preferably a second negative electrode current collector containing at least one of copper or copper alloys. The expansion and contraction of the second negative electrode active material due to charging and discharging is more significant than that of the first negative electrode active material. If at least one side of the negative electrode containing the second negative electrode active material and the second negative electrode current collector is exposed from the positive electrode, it is prone to deformation due to volume changes caused by the charging and discharging reaction. Therefore, by satisfying equation (1) in the relationship of arithmetic mean roughness, the life performance can be reliably improved. It is preferable that the content of the second negative electrode active material in the negative electrode active material is 20% by weight or more.

[0091] Adhesives can fill the gaps between dispersed active materials. Additionally, they can bond the active materials to the current collector. Examples of adhesives include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these can be used as an adhesive, or a combination of two or more can be used.

[0092] Conductive agents can improve current collection performance. Additionally, they can suppress the contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One or more of these can be used as a conductive agent. Alternatively, carbon coating or electronically conductive inorganic material coating can be applied to the surface of the active material particles instead of using a conductive agent.

[0093] The density of the negative electrode active material layer (excluding the current collector) is preferably 1.4 g / cm³. 3 Above and 2.8g / cm 3 The following describes the negative electrode with excellent energy density and electrolyte retention within a given density range for the negative electrode active material layer. A more preferred density for the negative electrode active material layer is 2.1 g / cm³. 3 Above and 2.6g / cm 3 the following.

[0094] The proportions of the active material, conductive agent, and binder in the active material layer can be appropriately varied depending on the application of the electrode. For example, it is preferable to combine the active material, conductive agent, and binder in proportions of 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively.

[0095] The negative electrode can be fabricated, for example, by the following method. First, a slurry is prepared by suspending the negative electrode active material, conductive agent, and binder in a solvent. This slurry is then coated onto one or both sides of the current collector. The solvent is not limited to water; for example, it can be other water-soluble solvents or organic solvents. Next, the coated slurry is dried to obtain a laminate containing a layer of negative electrode active material and a current collector. Then, the laminate is pressed. In this way, the negative electrode is fabricated.

[0096] Alternatively, the negative electrode can also be made by the following method: First, the negative electrode active material, conductive agent, and binder are mixed to obtain a mixture. Next, the mixture is shaped into granules. Then, by placing these granules on a current collector, the negative electrode can be obtained.

[0097] 2) Positive electrode The positive electrode may comprise a positive current collector and a layer containing a positive active material. The layer containing the positive active material may be formed on one or both sides of the positive current collector. The layer containing the positive active material may comprise the positive active material and any conductive agent and binder.

[0098] As positive electrode active materials, oxides or sulfides can be used, for example. The positive electrode can contain only one compound, or it can contain two or more compounds as positive electrode active materials. Examples of oxides and sulfides include compounds that can enable the insertion and extraction of alkali metals or alkali metal ions.

[0099] Such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, and lithium manganese composite oxides (e.g., Li). x Mn2O4 or Li x MnO2; 0 < x ≤ 1), lithium-nickel composite oxides (e.g., Li) xNiO2; 0 < x ≤ 1), lithium cobalt composite oxides (e.g., Li) x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxides (e.g., Li) x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxides (e.g., Li) x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxides with spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), ferric sulfate (Fe2(SO4)3), vanadium oxides (e.g., V2O5), lithium nickel cobalt manganese composite oxides (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1), sodium transition metal oxides, sodium transition metal phosphate compounds, Prussian blue-like complexes.

[0100] As a sodium transition metal oxide, examples include Na n M I x M II y M III z O2 (where M) I M II M III They can be the same or different, and each must be at least one element selected from Ni, Co, Mn, Fe, Cu, Al, and Zn, not necessarily limited to three. n, x, y, and z can be listed in the following conditions: 0.5 ≤ n ≤ 1.2, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1 and x + y + z = 1, etc. Specifically, NaNi can be listed. 0.33 Fe 0.33 Mn 0.33 O2, NaNi 0.2 Fe 0.33 Mn 0.33 Cu 0.13 O2, etc.

[0101] Sodium transition metal phosphate compounds, for example, Na n M x (P) y O z(Where M is selected from at least one element from Ni, Co, Mn, and Fe. In addition, some phosphorus can be replaced by Si, S, B, Ge, etc. Specifically, examples include Na4Fe3(PO4)2P2O7, Na3Fe2(PO4)3, and NaFePO4.)

[0102] As a Prussian blue-like complex, Na can be cited as an example. n M I x M II y (CN)6) (where M I M II They can be the same or different from each other, and each is selected from at least one element from Ni, Co, Mn and Fe; n, x, y are 1≤n≤3, 0≤x≤1, 0≤y≤1, x+y=2, etc.

[0103] Examples of compounds preferred as positive electrode active materials, as described above, include lithium manganese composite oxides having a spinel structure (e.g., Li). x Mn₂O₄; 0 < x ≤ 1), lithium-nickel composite oxides (e.g., Li₂O₄); x NiO2; 0 < x ≤ 1), lithium cobalt composite oxides (e.g., Li) x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxides (e.g., Li) x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxides with spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxides (e.g., Li) x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li) x FePO4; 0<x≤1) and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1). If these compounds are used as positive electrode active materials, the positive electrode potential can be increased.

[0104] When using room-temperature molten salt as the battery electrolyte, it is preferable to use electrolytes containing lithium iron phosphate or LiFePO4. xPositive electrode active materials include VPO4F (0≤x≤1), lithium manganese composite oxides, lithium nickel composite oxides, lithium nickel cobalt composite oxides, or mixtures thereof. These compounds exhibit low reactivity with room-temperature molten salts, thus improving cycle life. Details regarding room-temperature molten salts will be described later.

[0105] The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. Positive electrode active materials with a primary particle size of 100 nm or more are easy to process in industrial production. Positive electrode active materials with a primary particle size of 1 μm or less enable the smooth diffusion of alkali metal ions (such as lithium ions) within the solid.

[0106] The specific surface area of ​​the positive electrode active material is preferably 0.1 m². 2 / g or more and 10m 2 / g or less. Has 0.1m 2 Positive electrode active materials with a specific surface area of ​​over / g can adequately ensure the insertion and deintercalation sites for alkali metal ions such as lithium ions. With a specific surface area of ​​10m... 2 Positive electrode active materials with a specific surface area of ​​less than 1 g are easy to process in industrial production and can ensure good charge-discharge cycle performance.

[0107] Binders are used to fill the gaps between dispersed positive electrode active materials and to bond the positive electrode active materials to the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of them can be used as a binder, or two or more can be used in combination.

[0108] The positive current collector can be, for example, a current collector foil. The current collector foil may also have through holes. The positive current collector is preferably an aluminum foil, or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu and Si.

[0109] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0110] Additionally, the positive current collector can be included in the portion of its surface where no layer of positive active material is formed. This portion can function as a positive current collector tab.

[0111] Conductive agents are used to improve current collection performance and suppress contact resistance between the active material and the current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite, carbon nanotubes, and carbon nanofibers. One or more of these can be used as a conductive agent. Alternatively, a carbon coating or an electronically conductive inorganic material coating can be applied to the surface of the active material particles instead of a conductive agent. Furthermore, in positive electrode configurations, the conductive agent can be omitted.

[0112] Water-soluble adhesives can be used as binders. Cellulose-based components, such as sodium carboxymethyl cellulose (CMC), fluorinated rubbers, or styrene-butadiene rubbers, can be used as water-soluble adhesives, but are not limited to these.

[0113] The proportions of the active material, conductive agent, and binder in the active material layer can be appropriately varied depending on the application of the electrode. For example, it is preferable to combine the active material, conductive agent, and binder in proportions of 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively.

[0114] The positive electrode can be manufactured, for example, by the following method. First, a slurry is prepared by suspending the positive electrode active material, conductive agent, and binder in a solvent. This slurry is then coated onto one or both sides of the current collector. The solvent is not limited to water; for example, it can be other water-soluble solvents or organic solvents. Next, the coated slurry is dried to obtain a laminate containing a layer of positive electrode active material and a current collector. Then, the laminate is pressed. The positive electrode is manufactured in this manner.

[0115] Alternatively, the positive electrode can be manufactured using the following method. First, the positive electrode active material, conductive agent, and binder are mixed to obtain a mixture. Next, this mixture is shaped into granules. Then, by placing these granules onto a current collector, the positive electrode can be obtained.

[0116] 3) Electrolytes As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-like non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt, which is the solute, in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or higher and 2.5 mol / L or lower.

[0117] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), as well as mixtures thereof. Preferred electrolyte salts are those that are difficult to oxidize even at high potentials, with LiPF6 being the most preferred.

[0118] In addition, examples of electrolyte salts that allow Na or Na ions to be inserted or extracted into an active substance include sodium salts such as sodium perchlorate (NaClO4), sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium hexafluoroarsenate (NaAsF6), sodium trifluoromethanesulfonate (NaCF3SO3), and sodium bis(trifluoromethanesulfonyl)imide (NaN(CF3SO2)2), as well as mixtures thereof.

[0119] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); chain ethers such as dimethoxyethane (DME), diethoxyethane (DEE), and diethylene glycol dimethyl ether (diglyme (G2)); γ-butyrolactone (GBL); acetonitrile (AN); and sulfolane (SL). These organic solvents can be used alone or as mixed solvents.

[0120] Gel-like nonaqueous electrolytes are prepared by combining liquid nonaqueous electrolytes with polymeric materials. Examples of polymeric materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0121] Alternatively, as non-aqueous electrolytes, in addition to liquid non-aqueous electrolytes and gel non-aqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions or sodium ions, polymeric solid electrolytes, and inorganic solid electrolytes can also be used.

[0122] Room-temperature molten salts (ionic melts) refer to compounds of organic salts composed of a combination of organic cations and anions that exist as liquids at room temperature (above 15°C and below 25°C). Room-temperature molten salts include those that exist as liquids alone, those that become liquids by mixing with electrolyte salts, those that become liquids by dissolving in organic solvents, or mixtures thereof. Generally, the melting point of room-temperature molten salts used in secondary batteries is below 25°C. Furthermore, the organic cations typically possess a quaternary ammonium framework.

[0123] Polymer solid electrolytes are prepared by dissolving electrolyte salts in polymer materials and then solidifying them.

[0124] Examples of inorganic solid electrolytes include solid materials with lithium-ion conductivity and solid materials with sodium-ion conductivity. Lithium-ion conductivity, as referred to here, means exhibiting 1×10⁻⁶ conductivity at 25°C. -6 Lithium-ion conductivity of S / cm or higher. Examples of inorganic solid electrolytes include oxide-based and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are described below.

[0125] As an oxide-based solid electrolyte, it is preferable to use an electrolyte with a NASICON (Sodium(Na) Super Ionic Conductor) type structure and composed of the general formula Li 1+x Mα2(PO4)3 represents a lithium phosphate solid electrolyte. In the above general formula, Mα is, for example, selected from one or more of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is in the range of 0 ≤ x ≤ 2.

[0126] As a specific example of a lithium phosphate solid electrolyte with a NASICON-type structure, examples can be listed, such as those made from Li 1+ x Al x Ti2-x (PO4)3 represents LATP compounds where 0.1 ≤ x ≤ 0.5; derived from Li 1+x Al y Mβ 2-y (PO4)3 represents a compound in which Mβ is selected from one or more of Ti, Ge, Sr, Zr, Sn, and Ca, and 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1; derived from Li 1+x Al x Ge 2-x (PO4)3 represents compounds where 0 ≤ x ≤ 2; and compounds derived from Li 1+x Al x Zr 2-x (PO4)3 represents a compound in which 0 ≤ x ≤ 2; [The text abruptly ends here, likely due to an incomplete sentence or missing information.] 1+x+y Al x Mγ 2-x Si y P 3-y O 12 This indicates that Mγ is a compound selected from Ti and Ge, and 0 < x ≤ 2, 0 ≤ y < 3; derived from Li 1+2x Zr 1-x Ca x (PO4)3 represents a compound in which 0 ≤ x < 1.

[0127] In addition to the lithium phosphate solid electrolyte mentioned above, other oxide-based solid electrolytes include those made from Li... x PO y N z This refers to amorphous LIPON compounds (e.g., Li) with the following properties: 2.6 ≤ x ≤ 3.5, 1.9 ≤ y ≤ 3.8, and 0.1 ≤ z ≤ 1.3. 2.9 PO 3.3 N 0.46 ); Garnet-type structure composed of La 5+x A x La 3-x Mδ2O 12 This indicates a compound in which A is selected from one or more of Ca, Sr, and Ba, Mδ is selected from one or more of Nb and Ta, and 0 ≤ x ≤ 0.5; Li3Mδ 2-x L2O 12 This indicates a compound in which Mδ is selected from one or more of Nb and Ta, L may contain Zr, and 0 ≤ x ≤ 0.5; [The compound is derived from Li]. 7-3x Al x La3Zr3O 12 Represents compounds in which 0 ≤ x ≤ 0.5; derived from Li 5+x La3Mδ 2-x Zr x O 12This indicates that Mδ is an LLZ compound selected from Nb and Ta, and 0 ≤ x ≤ 2 (e.g., Li7La3Zr2O). 12 ); and having a perovskite-type structure and composed of La 2 / 3-x Li x TiO3 represents compounds in which 0.3 ≤ x ≤ 0.7.

[0128] One or more of the above-mentioned compounds can be used as a solid electrolyte. Two or more of the above-mentioned solid electrolytes can also be used. In addition, compounds in which Li is replaced by Na can be used as solid substances with sodium ion conductivity.

[0129] 4) Diaphragm The diaphragm can be formed, for example, from a porous membrane containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or from a nonwoven fabric made of synthetic resin. From a safety point of view, porous membranes made of polyethylene or polypropylene are preferred. This is because these porous membranes melt at a certain temperature and can block electric current.

[0130] The membrane may consist solely of a material disposed between the positive and negative electrodes, or it may comprise a portion that is covered only by one of the positive or negative electrodes.

[0131] 5) Outer packaging components As an outer packaging component, for example, a container formed of laminated film or a metal container can be used.

[0132] The thickness of the laminate is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0133] As a laminated film, a multilayer film comprising multiple resin layers and a metal layer between these resin layers is used. The resin layers include, for example, polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). For weight reduction, the metal layer is preferably formed of aluminum foil or aluminum alloy foil. The laminated film can be formed into the shape of an outer packaging component by sealing it using hot-melt bonding.

[0134] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0135] Metal containers are made of materials such as aluminum or aluminum alloys. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, their content is preferably less than 100 ppm by mass.

[0136] There are no particular limitations on the shape of the outer packaging components. The outer packaging components can be flat (thin), square, cylindrical, coin-shaped, or button-shaped, etc. The outer packaging components can be appropriately selected based on the battery size and intended use.

[0137] 6) Negative extremes The negative terminal can be formed from a material that is electrochemically stable and conductive at the insertion / deintercalation potential of alkali metals such as lithium in the aforementioned negative electrode active material. Specifically, examples of materials for the negative terminal include copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or aluminum alloys are preferred as the material for the negative terminal. To reduce the contact resistance with the negative electrode current collector, the negative terminal is preferably formed from the same material as the negative electrode current collector.

[0138] 7) Positive extreme The positive terminal can be in a potential range of 3V or higher and 4.5V or lower relative to the redox potential of lithium (vs. Li / Li). + The positive terminal is formed of a material that is electrically stable and conductive. Examples of materials for the positive terminal include aluminum, or aluminum alloys containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the positive current collector, the positive terminal is preferably formed of the same material as the positive current collector.

[0139] The battery described above, comprising a negative electrode, a positive electrode, an electrolyte, a separator, an outer packaging component, a negative terminal, and a positive terminal, enables the insertion and extraction of alkali metals or alkali metal ions into the active material. Preferred examples of alkali metals include lithium and sodium. When sodium or sodium ions are inserted and extracted into the active material, the positive electrode preferably comprises at least one selected from sodium transition metal oxides, sodium transition metal phosphate compounds, and Prussian blue-like complexes. Furthermore, the negative electrode preferably comprises at least one selected from hard carbon black, graphite, alloys, oxides, and sulfides. On the other hand, the electrolyte preferably contains a sodium salt.

[0140] The method for identifying electrode active materials is explained.

[0141] When the electrode to be measured is assembled in a battery, the electrode is removed from the battery, for example, as described below. First, the battery is discharged to 0.0V, reaching an over-discharge state. Next, the battery is disassembled in an argon-filled glove box, and the electrode is removed. If the electrode, along with the counter electrode and separator, forms an electrode assembly, the electrode assembly is removed and disassembled, and the electrode to be measured is separated from the electrode assembly.

[0142] The active substances can be identified by crystal structure analysis based on X-ray diffraction spectroscopy and compositional analysis based on inductively coupled plasma (ICP) emission spectroscopy.

[0143] XRD measurements can be performed, for example, as follows.

[0144] First, to determine the crystallization state of the active material, a state in which alkali metal ions such as lithium ions are completely extracted from and intercalated from the active material is achieved. For example, in the case of the negative electrode used in a battery, the battery is brought to a fully discharged state. For instance, the battery is discharged at 25°C with a current of 0.1C until the rated termination voltage or the battery voltage reaches 1.0V, and this operation is repeated multiple times. By ensuring that the discharge current is less than 1 / 100 of the rated capacity, the battery can be brought to a discharged state. Even in the discharged state, residual alkali metal ions may sometimes remain.

[0145] Next, the battery is disassembled in an argon-filled glove box, the electrodes are removed, and cleaned with a suitable solvent. For example, dimethyl carbonate can be used as a suitable solvent. If the electrodes are not cleaned sufficiently, impurity phases such as lithium carbonate and lithium fluoride may sometimes be introduced due to the influence of residual lithium ions in the electrodes. In this case, a gas-tight container capable of conducting the measurement in an inactive gas atmosphere can be used. The cleaned electrode is cut into an area equal to the area of ​​the holder of the powder X-ray diffraction apparatus, serving as the measurement sample. This sample is directly attached to the glass holder for measurement.

[0146] At this point, XRD is used to pre-determine and understand the peaks from the metal foil, conductive agent, and binder, which serve as current collectors. Of course, if these can be determined beforehand, this step can be omitted. In cases where the peaks of the current collector overlap with the peaks of the active material, it is preferable to peel off the active material layer from the current collector for measurement. This is to separate the overlapping peaks when quantitatively measuring the peak intensity. The active material layer can be peeled off physically, as described above, or by immersion in a solvent such as water. In the latter case, by evaporating the solvent, the electrode assembly (containing the active material, conductive agent, and binder) can be recovered. By filling the recovered electrode assembly into, for example, a capillary made of Lindeman glass, and performing the measurement, powder X-ray diffraction analysis of the active material can be conducted.

[0147] For example, the SmartLab device manufactured by Rigaku Corporation was used as the apparatus for powder X-ray diffraction. The measurement conditions are as follows: X-ray source: Cu target Output: 45kV 200mA Sola Slit: Both incident and received light angles are 5° Step size (2θ): 0.02 deg Scanning speed: 20 deg / minute Semiconductor detector: D / teX Ultra 250 Measurement range: 5°≤2θ≤90° Sample plate holder: Flat glass sample plate holder (thickness 0.5mm).

[0148] In the case of using other apparatus, in order to obtain the same measurement results as described above, measurements were performed using standard Si powder for powder X-ray diffraction, with the peak intensity and peak position adjusted to be consistent with the apparatus described above.

[0149] The composition of the active substance was determined by ICP emission spectroscopy according to the following steps.

[0150] The active material layer is peeled off from the electrode, which has been removed from the battery and cleaned, using the method described above. Next, the peeled portion is briefly heated in atmospheric air (e.g., at approximately 500°C for about 1 hour) to burn off unwanted components such as binders and conductive agents. By dissolving the residue with an acid, a liquid sample containing the active material can be prepared. Hydrochloric acid, nitric acid, sulfuric acid, hydrogen fluoride, etc., can be used as the acid. By performing ICP analysis on this liquid sample, the average composition of the active material can be determined.

[0151] <Manufacturing Method> The following describes a method for manufacturing the battery according to an embodiment. The battery of the embodiment can be manufactured, for example, by appropriately adjusting conditions such as the combination of active material and current collector, the coating amount of the slurry containing the active material, the pressing conditions during electrode manufacturing, the electrolyte quantity, and the initial charging conditions.

[0152] For example, regarding the electrolyte volume, it is preferable to increase the electrolyte injection ratio. Here, the electrolyte injection ratio is the electrolyte volume when the total void volume of the positive electrode and the negative electrode is set to 1. The void volume of the positive electrode and the void volume of the negative electrode are calculated based on the true density of the materials constituting each electrode and the size of each electrode, respectively. The electrolyte injection ratio is preferably in the range of 1.15 times or more and 1.4 times or less. Furthermore, the optimal electrolyte injection ratio may vary due to factors such as the method of forming the wave shape and the constraint state of the secondary battery during the first charge.

[0153] Initial charging is preferably performed with the secondary battery constrained from both sides on its wide sides (the two sides intersecting the thickness direction). An example of the constraint method is shown below. Figure 13 Multiple secondary batteries 100 are housed in a box-shaped bracket 14 with their wide surfaces (xy planes) in contact with each other. Next, the multiple secondary batteries 100 are pressurized in the thickness direction 16 (z-axis direction) by a constraint clamp 15. The positive terminal 6 and negative terminal 7 extending from each secondary battery 100 in the y-axis direction are located outside the bracket 14 and are therefore not subjected to pressure. By performing initial charging while the secondary batteries 100 are pressurized along the thickness direction 16 (z-axis direction) and appropriately adjusting the electrolyte injection coefficient, the secondary battery of the embodiment can be manufactured.

[0154] In addition, the secondary battery of the embodiment can also be manufactured by making the coating amount on the outer edge of the electrode less than that on others and continuously pressing it, thereby utilizing the difference in pressing elongation per unit area weight.

[0155] The secondary battery of the first embodiment includes an electrode assembly having a stacked structure comprising one electrode, another electrode, and a separator located at least between the one electrode and the other electrode. In a direction intersecting the stacking direction of the electrode assembly, at least one side of one electrode protrudes relative to at least one side of the other electrode. The electrode assembly satisfies equation (1): Ra2 > Ra1. In equation (1), Ra2 is the arithmetic mean roughness of the end portion of the electrode assembly containing at least one side of the electrode, and Ra1 is the arithmetic mean roughness of the interior of the electrode assembly adjacent to the end portion. According to the secondary battery of the first embodiment, electrolyte retention can be improved while ensuring the flatness and thermal uniformity of the battery. Therefore, lifespan performance can be improved.

[0156] (Second Implementation) According to a second embodiment, a battery pack is provided. This battery pack includes batteries with multiple embodiments.

[0157] In this battery pack, the individual cells can be electrically connected in series or in parallel, or a combination of series and parallel connections can be used.

[0158] The battery pack of this embodiment includes the battery of this embodiment. Therefore, it can exhibit high lifespan performance.

[0159] (Third implementation method) According to a third embodiment, a battery pack is provided. This battery pack includes the battery pack of the embodiment. Alternatively, the battery pack may include a single battery of the embodiment instead of the battery pack of the embodiment.

[0160] The battery pack can be further equipped with a protection circuit. This protection circuit controls the charging and discharging of the secondary battery. Alternatively, the circuitry within a device that uses the battery pack as a power source (such as electronic devices, automobiles, etc.) can be used as the battery pack's protection circuitry.

[0161] Furthermore, the battery pack may also include external terminals for power supply. These external terminals are used to supply current from the secondary battery to the external source and / or to supply current from the external source to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the external source through the external terminals. Additionally, when charging the battery pack, charging current (including regenerative energy from the power source of a vehicle, etc.) is supplied to the battery pack through the external terminals.

[0162] Next, an example of the battery pack according to the embodiments will be described with reference to the accompanying drawings.

[0163] Figure 14 This is an exploded perspective view that roughly represents an example of a battery pack. Figure 15 It means Figure 14 A block diagram of an example of the circuitry for the battery pack shown.

[0164] Figure 14 and Figure 15 The battery pack 300 shown includes a container 31, a cover 32, a protective sheet 33, a battery pack 200, a printed circuit board 34, wiring 35, and an insulating plate (not shown).

[0165] Figure 14 The container 31 shown is a square container with a rectangular base. The container 31 is configured to accommodate the protective sheet 33, the battery pack 200, the printed circuit board 34, and the wiring 35. The cover 32 has a rectangular shape. The cover 32 accommodates the battery pack 200 and the like by covering the container 31. Although not shown, the container 31 and the cover 32 are provided with openings or connection terminals for connecting to external devices.

[0166] The battery pack 200 includes multiple individual cells 100, positive electrode side lead 22, negative electrode side lead 23, and adhesive tape 24.

[0167] At least one of the multiple single cells 100 is a secondary battery in an embodiment. For example... Figure 15 As shown, multiple individual cells 100 are electrically connected in series. Multiple individual cells 100 can also be electrically connected in parallel, or a combination of series and parallel connections. When multiple individual cells 100 are connected in parallel, the battery capacity increases compared to a series connection.

[0168] Adhesive tape 24 is used to bundle multiple individual cells 100 together. Alternatively, heat shrinkable tape can be used to secure the multiple individual cells 100 instead of adhesive tape 24. In this case, protective sheets 33 are placed on both sides of the battery pack 200, and the heat shrinkable tape is wrapped around the pack and then heat-shrinked to bundle the multiple individual cells 100 together.

[0169] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more individual cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more individual cells 100.

[0170] A printed circuit board 34 is disposed along a width direction on the inner side of the receiving container 31. The printed circuit board 34 includes a positive-side connector 342, a negative-side connector 343, a thermistor 345, a protection circuit 346, wirings 342a and 343a, an external terminal 350 for power supply, positive-side wiring 348a, and negative-side wiring 348b. One main surface of the printed circuit board 34 faces one side of the battery pack 200. An insulating plate (not shown) is positioned between the printed circuit board 34 and the battery pack 200.

[0171] The other end 22a of the positive lead 22 is electrically connected to the positive connector 342. The other end 23a of the negative lead 23 is electrically connected to the negative connector 343.

[0172] A thermistor 345 is fixed to one main surface of the printed circuit board 34. The thermistor 345 detects the temperature of each individual cell 100 and sends its detection signal to the protection circuit 346.

[0173] An external terminal 350 for power supply is fixed to another main surface of the printed circuit board 34. The external terminal 350 for power supply is electrically connected to a device located outside the battery pack 300. The external terminal 350 for power supply includes a positive terminal 352 and a negative terminal 353.

[0174] The protection circuit 346 is fixed to another main surface of the printed circuit board 34. The protection circuit 346 is connected to the positive terminal 352 via positive side wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via negative side wiring 348b. Additionally, the protection circuit 346 is electrically connected to the positive connector 342 via wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the plurality of individual cells 100 via wiring 35.

[0175] The protective sheet 33 is disposed on two inner sides of the receiving container 31 in the longitudinal direction and on the inner side of the battery pack 200 opposite to the printed circuit board 34 in the width direction. The protective sheet 33 is formed, for example, of resin or rubber.

[0176] The protection circuit 346 controls the charging and discharging of multiple individual batteries 100. In addition, based on the detection signal sent from the thermistor 345, or the detection signal sent from each individual battery 100 or battery pack 200, the protection circuit 346 disconnects the electrical connection between the protection circuit 346 and the external terminals 350 (positive terminal 352, negative terminal 353) used to power external devices.

[0177] As a detection signal sent from the thermistor 345, examples include signals indicating that the temperature of a single cell 100 is above a predetermined temperature. As a detection signal sent from each single cell 100 or the battery pack 200, examples include signals indicating overcharging, over-discharging, and overcurrent of a single cell 100. In the case of detecting overcharging in each single cell 100, the battery voltage, or the positive or negative electrode potential, can be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each single cell 100.

[0178] In addition, as a protection circuit 346, a circuit contained in a device that uses the battery pack 300 as a power source (such as an electronic device, a car, etc.) can also be used.

[0179] Furthermore, as described above, the battery pack 300 includes an external terminal 350 for power supply. Therefore, the battery pack 300 can output current from the battery pack 200 to an external device and input current from an external device to the battery pack 200 via the external terminal 350. In other words, when the battery pack 300 is used as a power source, current from the battery pack 200 is supplied to the external device through the external terminal 350. Additionally, when charging the battery pack 300, charging current from the external device is supplied to the battery pack 300 through the external terminal 350. When the battery pack 300 is used as a vehicle battery, the regenerative energy from the vehicle's power source can be used as the charging current from the external device.

[0180] Furthermore, the battery pack 300 may also include multiple battery packs 200. In this case, the multiple battery packs 200 may be connected in series, in parallel, or a combination of series and parallel connections. Additionally, the printed circuit board 34 and wiring 35 may be omitted. In this case, the positive lead 22 and the negative lead 23 may be used as the positive terminal 352 and negative terminal 353 of the external terminal 350 for power supply, respectively.

[0181] Such battery packs are used in applications requiring excellent cycle performance when drawing high currents. Specifically, they are used as power sources for electronic devices, stationary batteries, and in-vehicle batteries for various vehicles. Examples of electronic devices include digital cameras. These battery packs are particularly suitable for use as in-vehicle batteries.

[0182] The battery pack of the third embodiment includes the secondary battery of the embodiment or the battery pack of the embodiment. Therefore, the battery pack has high lifespan performance.

[0183] [Example] The following describes the embodiments, but the implementation is not limited to the embodiments described below.

[0184] (Example 1) <Making the Negative Electrode> As the negative electrode active material, particles of a titanium-niobium composite oxide with a monoclinic crystal structure represented by the formula TiNb2O7 were prepared. These particles were referred to as niobium-containing oxides. Carbon nanotubes (CNTs) and acetylene black (AB) were prepared as conductive agents, and carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) were prepared as binders. These were mixed in pure water at a mass ratio of negative electrode active material: AB:CNT:CMC:SBR of 96.2:0.5:0.3:2:1 to obtain a slurry.

[0185] On both sides of the main surface of a current collector formed from an aluminum foil with a thickness of 15 μm, except for the long edges, the slurry is coated and allowed to dry. The uncoated portions of the current collector function as negative electrode tabs. This yields a laminate containing the current collector, a layer of negative active material formed on both sides of the current collector except for the long edges, and negative electrode tabs. Next, the resulting laminate is stretched to a density of 2.7 g / cm³ for the negative active material layer. 3 The method is to supply the rollers.

[0186] <The Making of the Positive Electrode> As the positive electrode active material, LiNi is prepared. 0.5 Co 0.2 Mn 0.3O2 represents lithium nickel cobalt manganese composite oxide particles. Additionally, acetylene black (AB) is prepared as a conductive agent, and polyvinylidene fluoride (PVdF) is prepared as a binder. These are mixed at a mass ratio of positive electrode active material:AB:PVdF of 90:5:5 to obtain a mixture. Next, the obtained mixture is dispersed in n-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The slurry is coated onto the main surfaces of both sides of a current collector formed from an aluminum foil with a thickness of 15 μm, excluding the long edges, and the coating is allowed to dry. The uncoated portions of the current collector function as positive electrode current collector tabs. Thus, a laminate containing a current collector, a layer of positive electrode active material formed on both sides of the current collector excluding the long edges, and positive electrode current collector tabs are obtained. Next, the obtained laminate is heated to a density of 3.05 g / cm³ containing the positive electrode active material layer. 3 The method is to supply the rollers.

[0187] <Electrode Assembly Manufacturing> Prepare a polyethylene (PE) membrane with a thickness of 15 μm. The aforementioned negative and positive electrodes are wound into a flat spiral shape while the membrane is sandwiched between them, thereby creating a flat electrode assembly. In the resulting electrode assembly, at one end along the winding axis, the membrane, the layer containing the negative electrode active material, and the layer containing the positive electrode active material are sequentially located further inside than the positive electrode current collector. Similarly, at the other end along the winding axis, the membrane, the layer containing the negative electrode active material, and the layer containing the positive electrode active material are sequentially located further inside than the negative electrode current collector. Therefore, at both ends along the winding axis, the long sides of the layers containing the negative electrode active material protrude relative to the corresponding long sides of the layers containing the positive electrode active material. An aluminum positive terminal is welded to the positive electrode current collector, and an aluminum negative terminal is welded to the negative electrode current collector.

[0188] <Preparation of Non-Aqueous Electrolytes> The non-aqueous electrolyte was prepared according to the following steps. First, propylene carbonate (PC) and diethyl carbonate (DEC) were mixed in a volume ratio of PC:DEC of 1:2 to obtain a mixed solvent. Lithium hexafluorophosphate (LiPF6) was then dissolved in this mixed solvent at a concentration of 1M to obtain a liquid non-aqueous electrolyte.

[0189] <Battery Assembly> The electrode assembly was placed in an aluminum metal can with a plate thickness of 0.2 mm and vacuum dried. Then, the electrolyte was injected with an injection coefficient of 1.3. After injection, the metal can was sealed to manufacture the battery. Here, the injection coefficient is the amount of electrolyte when the total void volume of the positive and negative electrodes is set to 1. The void volumes of the positive and negative electrodes are calculated based on the true density of the materials constituting each electrode and the dimensions of each electrode, respectively.

[0190] Next, the secondary battery of Example 1 is manufactured by initially charging it while pressurizing both sides of the wide side (pressurizing in the thickness direction of the battery) until the state of charge (SOC) reaches 100%.

[0191] (Example 2) The electrode assembly was fabricated in the same manner as described in Example 1. The electrode assembly was placed in a laminated film container and vacuum dried. Next, the electrolyte was injected using the injection coefficients shown in Table 1. After injection, the battery was manufactured by sealing the container. The laminated film used was a 0.1 mm thick laminate with polypropylene layers formed on both sides of a 40 μm thick aluminum foil.

[0192] Next, the obtained secondary battery was initially charged using the same method as described in Example 1 to manufacture the secondary battery of Example 2.

[0193] (Example 3) <Making the Negative Electrode> On both sides of the main surface of a current collector formed from an aluminum foil with a thickness of 15 μm, except for the short side of one side, a slurry prepared using the same method as described in Example 1 is coated, and the coating is dried. The current collector in the uncoated portion of the slurry functions as a negative electrode current collector tab. Thus, a laminate containing a current collector, a layer containing a negative electrode active material formed on both sides of the current collector except for the short sides, and a negative electrode current collector tab is obtained. Next, the resulting laminate is stretched to a density of 2.7 g / cm³ containing the negative electrode active material layer. 3 The method is to supply the rollers.

[0194] <The Making of the Positive Electrode> On both sides of the main surface of a current collector formed from an aluminum foil with a thickness of 15 μm, except for the short side of one side, a slurry prepared using the same method as described in Example 1 is coated, and the coating is allowed to dry. The current collector in the uncoated portion of the slurry functions as a positive electrode current collector tab. Thus, a laminate containing a current collector, a layer containing a positive active material formed on both sides of the current collector except for the short sides, and a positive electrode current collector tab is obtained. Next, the obtained laminate is stretched to a density of 3.05 g / cm³ containing the positive active material layer. 3 The method is to supply the rollers.

[0195] <Electrode Assembly Manufacturing> Prepare a polyethylene (PE) membrane with a thickness of 15 μm. Alternately stack the aforementioned negative and positive electrodes, with the membrane sandwiched between them, to fabricate a flat electrode assembly. On the four sides of the resulting electrode assembly, the layer containing the negative electrode active material and the layer containing the positive electrode active material are sequentially located further inside than the membrane. Weld an aluminum positive terminal to the positive electrode current collector tab, and weld an aluminum negative terminal to the negative electrode current collector tab.

[0196] <Preparation of Non-Aqueous Electrolytes> The non-aqueous electrolyte was prepared following the same steps as in Example 1.

[0197] <Battery Assembly> The electrode assembly was housed in an aluminum metal can with a plate thickness of 0.2 mm and vacuum dried. Next, the electrolyte was injected using the injection coefficients shown in Table 1. After injection, the metal can was sealed to manufacture the battery.

[0198] Next, the obtained secondary battery was initially charged using the same method as described in Example 1 to manufacture the secondary battery of Example 1.

[0199] (Example 4) Except for changing the liquid injection coefficient to the values ​​shown in Table 1, the secondary battery was manufactured in the same manner as in Example 3.

[0200] (Example 5) The stacked electrode assembly was fabricated using the same method as described in Example 3. The electrode assembly was placed in a laminated film container, similar to that in Example 2, and vacuum dried. Next, the electrolyte was injected using the injection coefficients shown in Table 1. After injection, the battery was manufactured by sealing the container.

[0201] Next, the obtained secondary battery is initially charged using the same method as described in Example 1 to manufacture a secondary battery.

[0202] (Example 6) Except for changing the liquid injection coefficient to the value shown in Table 1, the secondary battery was manufactured in the same manner as in Example 5.

[0203] (Example 7) The stacked electrode assembly was fabricated using the same method as described in Example 3. The electrode assembly was placed in a laminated film container, similar to that in Example 2, and vacuum dried. Next, the electrolyte was injected using the injection coefficients shown in Table 1. After injection, the battery was manufactured by sealing the container.

[0204] Next, a surface pressure of 0.3 MPa was applied to the surface of the secondary battery intersecting the thickness direction for constraint, and the battery was left idle for 3 hours under constraint. Then, the surface pressure was adjusted to 0.3 MPa by tightening again. Then, an initial charge was performed until the state of charge (SOC) reached 100%, thus manufacturing the secondary battery.

[0205] (Example 8) <Making the Negative Electrode> On both the inner and outer surfaces of a current collector formed from 15 μm thick aluminum foil, except for the short side of one side, a paste prepared using the same method as described in Example 1 is applied. Furthermore, the coating amount is adjusted such that the electrode weight per unit area from the long side of each of the two main surfaces of the current collector to 3 mm inside is 10% less than the others. Next, after the coating film dries, continuous rolling is performed to form a wavy shape on the two long sides of the negative electrode.

[0206] A flat electrode assembly is fabricated by alternately stacking the aforementioned negative electrode and a positive electrode (same as in Example 3) with a separator (same as in Example 3) sandwiched between them. On the two long sides of the resulting electrode assembly, the layer containing the negative electrode active material and the layer containing the positive electrode active material are sequentially located further inside than the separator. An aluminum positive terminal is welded to the positive electrode current collector tab, and an aluminum negative terminal is welded to the negative electrode current collector tab.

[0207] The resulting electrode assembly was placed in the same laminated film container as in Example 2 and vacuum dried. Next, the electrolyte was injected using the injection coefficients shown in Table 1. After injection, the container was sealed to manufacture the battery.

[0208] Next, a surface pressure of 0.3 MPa is applied to constrain the surface of the secondary battery that intersects with the thickness direction, and then initial charging is performed until the state of charge (SOC) reaches 100% to manufacture the secondary battery.

[0209] (Example 9) The negative electrode is manufactured using the method described below, with the liquid injection coefficient being the value shown in Table 1. Otherwise, the secondary battery is manufactured in the same manner as in Example 8.

[0210] In the fabrication of the negative electrode, graphite is used instead of monoclinic titanium-niobium composite oxide as the active material, resulting in a negative electrode active material layer density of 1.6 g / cm³. 3 Otherwise, it is carried out in the same manner as in Example 1.

[0211] (Example 10) The negative electrode is manufactured using the method described below, with the liquid injection coefficient being the value shown in Table 1. Otherwise, the secondary battery is manufactured in the same manner as in Example 5.

[0212] In the fabrication of the negative electrode, graphite and silicon dioxide (SiO2) are used. x The active material, prepared by mixing materials with a mass ratio of 95:5 (x≈1.0), replaces the monoclinic titanium-niobium composite oxide as the active material, and the density of the layer containing the negative electrode active material is set to 1.6 g / cm³. 3 Otherwise, it is carried out in the same manner as in Example 1.

[0213] (Example 11) Prepare the positive electrode, negative electrode, and electrolyte using the methods described below.

[0214] In the fabrication of the positive electrode, Na4Fe3(PO4)2P2O7 is used instead of lithium nickel cobalt manganese composite oxide as the active material, and the density of the layer containing the positive electrode active material is set to 1.8 g / cm³. 3 Otherwise, it is carried out in the same manner as in Example 1.

[0215] In the fabrication of the negative electrode, hard carbon black is used instead of monoclinic titanium-niobium composite oxide as the active material, resulting in a negative electrode active material layer density of 1.4 g / cm³. 3 Otherwise, it is carried out in the same manner as in Example 1.

[0216] As the electrolyte, a liquid non-aqueous electrolyte with the same composition as in Example 1 was prepared.

[0217] Using the prepared positive and negative electrodes and the same separator as in Example 3, a stacked electrode assembly was fabricated using the same method described in Example 3. The electrode assembly was placed in a laminated film container similar to that in Example 2 and vacuum dried. Next, the electrolyte was injected using the injection coefficients shown in Table 1. After injection, the battery was manufactured by sealing the container.

[0218] Next, the obtained secondary battery is initially charged using the same method as described in Example 1 to manufacture a secondary battery.

[0219] (Example 12) The stacked electrode assembly was fabricated using the same method as described in Example 3. The electrode assembly was placed in a laminated film container, similar to that in Example 2, and vacuum dried. Next, the electrolyte was injected using the injection coefficients shown in Table 1. After injection, the battery was manufactured by sealing the container.

[0220] Next, a surface pressure of 0.3 MPa was applied to the surface of the secondary battery intersecting the thickness direction for constraint, and the battery was left idle for 3 hours under constraint. Then, the surface pressure was adjusted to 0.3 MPa by tightening again. Then, an initial charge was performed until the state of charge (SOC) reached 100%, thus manufacturing the secondary battery.

[0221] (Compare Example 1 and Compare Example 2) Except for changing the liquid injection coefficient to the value shown in Table 1, the secondary battery was manufactured in the same manner as in Example 5.

[0222] (Comparative Example 3) The secondary battery was manufactured in the same manner as in Example 12, except that the liquid injection coefficient was changed to the value shown in Table 1.

[0223] (Comparative Example 4) The secondary battery was manufactured in the same manner as in Example 9, except that the liquid injection coefficient was changed to the value shown in Table 1.

[0224] (Comparative Example 5) The secondary battery was manufactured in the same manner as in Example 10, except that the liquid injection coefficient was changed to the value shown in Table 1.

[0225] (Comparative Example 6) The secondary battery was manufactured in the same manner as in Example 11, except that the injection coefficient was changed to the value shown in Table 1.

[0226] The arithmetic mean roughness Ra1, Ra2, and negative electrode thickness d of each secondary battery were measured using the above method. a Arithmetic mean roughness R1cell, R2cell, cell thickness d c The results are shown in Tables 1 and 2. It should be noted that in the secondary batteries of Examples 1, 3, and 4, since a metal can was used, the arithmetic mean roughness R1cell, R2cell, and cell thickness d were not measured. c .

[0227] In addition, for Examples 2, 5-12 and Comparative Examples 1-6 of pouch cells using laminated film containers, seven battery cells were grouped together and constrained while applying a constraint pressure of 0.2 MPa to the entire assembly. Cyclic tests were performed at SOC 0% to 100% under BMU monitoring with each battery cell adjusted to SOC 0% to 100%, by cycling through 1C charging and discharging at an ambient temperature of 25 degrees Celsius. The total thickness of the seven battery cells at 0.2 MPa is shown in Table 2 as the thickness of the battery group. The cycle life at 1000 cycles is shown in Table 2.

[0228] For the secondary batteries of Examples 1, 3, and 4 that used metal canisters, a cycle test was conducted at a SOC of 0% to 100% by performing a 1C charge followed by a 1C discharge cycle at an ambient temperature of 25 degrees Celsius. The capacity retention rate (%) at 1000 cycles is shown as the cycle life in Table 2.

[0229] As shown in Tables 1 and 2, when comparing Examples 1-8 and 12 using niobium oxide as the negative electrode material with Comparative Examples 1-3, it can be seen that the cycle life of the secondary batteries of Examples 1-8 and 12 is superior to that of Comparative Examples 1-3. Furthermore, a comparison of Example 9 using graphite as the negative electrode material with Comparative Example 4, Example 10 using Si as the negative electrode material with Comparative Example 5, and Example 11 using a sodium battery with Comparative Example 6 also shows that the cycle life of the secondary batteries in these examples is superior to that of the comparative examples.

[0230] In Examples 5 and 6, the ratio of the arithmetic mean roughness R2cell to the arithmetic mean roughness R1cell in Example 6 is greater than that in Example 5. Therefore, the ends of the electrode assembly in Example 6 have a larger wavy shape than those in Example 5. As a result, the battery pack thickness after charge-discharge cycles in Example 6 is thicker than that in Example 5.

[0231] In Example 7, since R2cell / R1cell > 3 and R1cell < 0.02d are satisfied... c Therefore, it has a long lifespan.

[0232] In Example 8, the ends of the electrode assembly are machined into a wavy shape. Therefore, regardless of the injection coefficient, Ra2 is greater than Ra1.

[0233] Furthermore, the results of Examples 9-11 show that anode materials other than niobium oxide can also achieve improved lifespan performance.

[0234] In Comparative Example 1, although an attempt was made to form waves through initial charging, the wave shape could not be formed due to an unsuitable electrolyte injection coefficient. Therefore, although the battery pack thickness was thinner than that of Example 5, its lifespan performance was worse than that of Example 5.

[0235] In Comparative Example 2, the liquid injection coefficient was slightly larger, and in addition, no tightening was performed during the initial charging, so the wave spread throughout the entire electrode assembly.

[0236] In Comparative Example 3, although the electrode was tightened during the initial charge, the liquid injection coefficient was large, resulting in waves throughout the entire electrode assembly.

[0237] A secondary battery according to at least one embodiment described above includes an electrode assembly with a stacked structure, the stacked structure comprising one electrode, another electrode, and a separator located at least between the one electrode and the other electrode. In a direction intersecting the stacking direction of the electrode assembly, at least one side of one electrode protrudes relative to at least one side of the other electrode. The electrode assembly satisfies equation (1): Ra2 > Ra1. In equation (1), Ra2 is the arithmetic mean roughness of the end portion of the electrode assembly containing at least one side of the one electrode, and Ra1 is the arithmetic mean roughness of the interior of the electrode assembly adjacent to the end portion. The secondary battery according to the embodiment can improve lifespan performance.

[0238] Several embodiments of the present invention have been described, but these embodiments are provided by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments or variations thereof are included in the scope or spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

[0239] The above-described implementation methods can be summarized into the following technical solutions.

[0240] {Technical Solution 1} A secondary battery comprising: Outer packaging components; An electrode assembly, housed within the aforementioned outer packaging component, has a laminated structure comprising one electrode, another electrode, and at least a diaphragm located between the one electrode and the other electrode; and The electrolyte is contained within the aforementioned outer packaging components. Wherein, in a direction intersecting the stacking direction of the aforementioned electrode group, at least one side of the aforementioned electrode protrudes relative to at least one side of the aforementioned other electrode, and the aforementioned electrode group satisfies the following equation (1), Ra2>Ra1 (1) In the above formula (1), Ra2 is the arithmetic mean roughness of the end of the electrode group containing the electrode at least one side, and Ra1 is the arithmetic mean roughness of the interior of the electrode group adjacent to the end.

[0241] {Technical Solution 2} According to the secondary battery described in {Technical Solution 1}, one of the electrodes is the negative electrode, and the other electrode is the positive electrode.

[0242] {Technical Solution 3} According to the secondary battery described in {Technical Solution 1} or {Technical Solution 2}, the negative electrode comprises: Contains a negative electrode active material layer, which includes at least one selected from niobium-containing oxides, hard carbon black, and graphite; and The current collector containing the aforementioned negative electrode active material layer comprises at least one of aluminum and aluminum alloy.

[0243] {Technical Solution 4} According to any one of {Technical Solution 1} to {Technical Solution 3}, the secondary battery wherein the negative electrode comprises: A layer containing a negative electrode active material, comprising at least one selected from metals, nonmetals, and alloys; and The current collector containing the aforementioned negative electrode active material layer comprises at least one of copper or a copper alloy.

[0244] {Technical Solution 5} According to any one of {Technical Solution 1} to {Technical Solution 4}, the secondary battery wherein the above-mentioned electrode assembly satisfies the following equation (2). Ra2 / Ra1≥3 (2).

[0245] {Technical Solution 6} According to any one of {Technical Solution 1} to {Technical Solution 5}, the secondary battery wherein Ra2 satisfies the following equation (3), Ra2≥d a (3) In equation (3) above, the above d a It is the thickness of the aforementioned negative electrode.

[0246] {Technical Solution 7} According to any one of {Technical Solution 1} to {Technical Solution 6}, the secondary battery wherein the outer packaging component is made of laminated film and satisfies the following formula (4), R2cell>R1cell (4) In equation (4) above, R2cell is the arithmetic mean roughness of at least one end of the widest surface of the secondary battery, and R1cell is the arithmetic mean roughness of the interior of the widest surface of the secondary battery.

[0247] {Technical Solution 8} The secondary battery according to any one of {Technical Solution 1} to {Technical Solution 7} satisfies the following equation (5): R2cell / R1cell≥3 (5).

[0248] {Technical Solution 9} According to any one of {Technical Solution 1} to {Technical Solution 8}, the secondary battery wherein the aforementioned R1cell satisfies the following equation (6), R1cell≤0.02d c (6) In equation (6) above, the above d c This refers to the thickness of the aforementioned secondary battery.

[0249] {Technical Solution 10} A battery pack comprising any one of the following technical solutions: {Technical Solution 1} to {Technical Solution 9}.

[0250] {Technical Solution 11} According to the battery pack described in {Technical Solution 10}, it also has: External terminals for power supply, and Protection circuit.

[0251] {Technical Solution 12} According to the battery pack described in {Technical Solution 11}, it comprises multiple of the aforementioned secondary batteries. The aforementioned secondary batteries are electrically connected in series, parallel, or a combination of series and parallel connections.

Claims

1. A secondary battery, comprising: Outer packaging components; An electrode assembly, housed within the outer packaging component, has a laminated structure comprising one electrode, another electrode, and at least a diaphragm located between the one electrode and the other electrode; and The electrolyte is contained within the outer packaging component. in, In a direction intersecting the stacking direction of the electrode group, at least one side of one electrode protrudes relative to at least one side of the other electrode, and the electrode group satisfies the following equation (1). Ra2>Ra1 (1) In equation (1), Ra2 is the arithmetic mean roughness of the end of the electrode group containing the at least one side of the electrode, and Ra1 is the arithmetic mean roughness of the interior of the electrode group adjacent to the end.

2. The secondary battery according to claim 1, wherein, One of the poles is the negative pole, and the other pole is the positive pole.

3. The secondary battery according to claim 2, wherein, The negative electrode comprises: Contains a negative electrode active material layer, which includes at least one selected from niobium-containing oxides, hard carbon black, and graphite; and A current collector containing a negative electrode active material layer, wherein the current collector comprises at least one of aluminum or an aluminum alloy.

4. The secondary battery according to claim 2, wherein, The negative electrode comprises: A layer containing a negative electrode active material, comprising at least one selected from metals, nonmetals, and alloys; and The current collector that retains the negative electrode active material layer comprises at least one of copper or a copper alloy.

5. The secondary battery according to claim 1, wherein, The electrode assembly satisfies the following equation (2). Ra2 / Ra1≥3 (2).

6. The secondary battery according to claim 2, wherein, The Ra2 satisfies the following equation (3), Ra2≥d a (3) In equation (3), d a It is the thickness of the negative electrode.

7. The secondary battery according to claim 1, wherein, The outer packaging component is made of laminated film and satisfies the following formula (4). R2cell>R1cell (4) In equation (4), R2cell is the arithmetic mean roughness of at least one end of the wide surface of the secondary battery, and R1cell is the arithmetic mean roughness of the interior of the wide surface of the secondary battery.

8. The secondary battery according to claim 7, which satisfies the following formula (5), R2cell / R1cell≥3 (5).

9. The secondary battery according to claim 7, wherein, The R1cell satisfies the following equation (6), R1cell≤0.02d c (6) Wherein, in equation (6), d c It is the thickness of the secondary battery.

10. A battery pack comprising the secondary battery according to any one of claims 1 to 9.

11. The battery pack according to claim 10, further comprising: External terminals for power supply, and Protection circuit.

12. The battery pack according to claim 11, comprising a plurality of said secondary batteries, The secondary batteries are electrically connected in series, parallel, or a combination of series and parallel connections.

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