Secondary battery

Abstract

The present invention provides a secondary battery having an electrode body with a transverse tab structure, suitable for maintaining battery performance while increasing capacity. The battery (secondary battery) of the present disclosure has a case (10), an electrode body (20), and an electrolyte (70). The case includes a bottom wall (11) and side walls (12, 13). The side wall (12) opposes the positive electrode tab portion (21T) of the electrode body in a first direction and extends in a second direction. The side wall (13) opposes the negative electrode tab portion (22T) in the first direction and extends in the second direction. The bottom wall is connected to the bottom ends (12a, 13a) of the side walls in the second direction. The aspect ratio of the length (L1) of the case in the first direction relative to the length (L2) of the case in the second direction is 2.0 or more. In a state in which an imaginary line passing through the bottom ends has an inclination angle of 45 degrees with respect to the horizontal, the electrolyte within the case does not contact the positive electrode tab portion and the negative electrode tab portion.

Description

Technical Field

[0001] This invention relates to secondary batteries. Background Technology

[0002] In recent years, rechargeable lithium-ion batteries and other rechargeable batteries have been used as power sources for portable devices and as driving power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). A rechargeable battery has an assembly comprising electrodes (positive and negative electrodes) that bear the battery reaction during charging and discharging, serving as an electrode body. The electrode body may, for example, have a laminated structure formed by alternating positive and negative electrodes separated by a separator. In such electrode bodies, positive electrode tabs are provided that are electrically connected to multiple portions (multilayers) of the positive electrode in the laminated structure, and negative electrode tabs are electrically connected to multiple portions (multilayers) of the negative electrode in the negative electrode structure. Sometimes, these tabs are located on the side of the electrode body (the side when the battery is in normal use) (a lateral tab structure design). For example, Patent Document 1 describes a rechargeable battery with an electrode body having a lateral tab structure as a non-aqueous electrolyte rechargeable battery.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2023-167298

[0004] There is a demand for high-capacity rechargeable batteries, especially for those used as power sources for vehicle propulsion. Summary of the Invention

[0005] This disclosure was made in this context, with the aim of providing a secondary battery suitable for maintaining battery performance while increasing capacity.

[0006] The secondary battery disclosed herein includes an electrode body, a non-aqueous electrolyte, and a casing housing the electrode body and the non-aqueous electrolyte. The electrode body has a positive electrode tab at one end in a first direction and a negative electrode tab at the other end. The casing includes a bottom wall, a first side wall, and a second side wall. The first side wall is opposite the positive electrode tab in the first direction and extends along a second direction. The first direction intersects the second direction. The second side wall is opposite the negative electrode tab in the first direction and extends along the second direction. The bottom wall is connected to the bottom ends of the first and second side walls in the second direction. The aspect ratio of the first length of the casing in the first direction to the second length of the casing in the second direction is 2.0 or more. With an imaginary line passing through the bottom ends of the first and second side walls at a 45-degree angle relative to the horizontal, the non-aqueous electrolyte inside the casing does not contact the positive or negative electrode tabs.

[0007] In this type of secondary battery structure, the aspect ratio is 2.0 or higher, which is suitable for achieving a large volume of the casing, and therefore suitable for achieving large-scale and high-capacity electrodes within the casing. Furthermore, in the case of a secondary battery with a lateral tab structure like the one described above, at a tilt angle of 45 degrees, the non-aqueous electrolyte within the casing does not contact the positive and negative electrode tabs. This is suitable for suppressing contact between components and foreign matter in the non-aqueous electrolyte and these electrode tabs (contact between the non-aqueous electrolyte and the electrode tabs may lead to a decrease in the function of the electrode tabs and even the battery performance, which is therefore undesirable). Therefore, the secondary battery of this disclosure is suitable for maintaining battery performance while achieving high capacity.

[0008] The higher the aspect ratio mentioned above, the higher the liquid level (upper end face) of the non-aqueous electrolyte in the relatively lower sidewall of the first and second sidewalls tends to reach when the secondary battery or casing is tilted. In a secondary battery with a transverse tab structure, the higher the liquid level reaches when the non-aqueous electrolyte is tilted, the easier it is for the non-aqueous electrolyte to contact the electrode tabs. Although contact between the non-aqueous electrolyte and the electrode tabs may lead to a decrease in the function of the electrode tabs and even the battery performance, since the secondary battery of this disclosure is configured such that the non-aqueous electrolyte does not contact the electrode tabs in the above-mentioned tilted state of 45 degrees, it is suitable for maintaining battery performance. Attached Figure Description

[0009] Figure 1 This is a perspective view of a secondary battery according to one embodiment of the present disclosure.

[0010] Figure 2 It is a schematic representation. Figure 1 The diagram shows a cross-sectional view of the internal structure of a secondary battery.

[0011] Figure 3 It is along Figure 2 A cross-sectional schematic diagram of the secondary cell of line III-III.

[0012] Figure 4 It means Figure 1 The diagram shows the structure of the electrode body of the secondary battery.

[0013] Figure 5 This is a magnified schematic diagram showing the main negative electrode end and its vicinity in the electrode body.

[0014] Figure 6 express Figure 1 and Figure 2 An example of the tilted state of a secondary battery is shown.

[0015] Figure 7 express Figure 1 and Figure 2 Another example of the tilted state of a secondary battery is shown. Detailed Implementation

[0016] Hereinafter, embodiments of the secondary battery of the present invention will be described with reference to the accompanying drawings. Matters not specifically mentioned in this specification but necessary for carrying out the present invention (e.g., the general structure and manufacturing process of the secondary battery not representing the present invention) can be understood by those skilled in the art based on prior art. The present invention can be implemented based on the disclosure in this specification and common technical knowledge in the field. Furthermore, in the following drawings, components and parts that perform the same function are indicated by the same reference numerals. The dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships.

[0017] Figure 1 This is a perspective view of a battery 100 as one embodiment of the secondary battery of the present invention. Figure 2 It is a schematic representation. Figure 1 A cross-sectional view of the internal structure of the battery 100 shown. Figure 3 This is a schematic cross-sectional view of battery 100 along line III-III in Figure 2. Figures 1-3 As shown, battery 100 is a non-aqueous electrolyte secondary battery comprising a casing 10, an electrode body 20, a positive terminal 30, a negative terminal 40, a positive current collector 50, a negative current collector 60, and an electrolyte 70 (non-aqueous electrolyte). In this embodiment, battery 100 is a lithium-ion secondary battery.

[0018] The casing 10 is the frame of the battery 100, such as Figure 2 As shown, the housing includes the electrode body 20 and the electrolyte 70. The housing 10 includes a housing body 10A and a sealing plate 10B. Figure 1 As shown, the housing 10 has a flat and generally cuboid shape (e.g., square) and extends along a first direction D1. In this embodiment, the housing 10 has a height in a second direction D2 orthogonal to the first direction D1 and a thickness in a third direction D3 orthogonal to both the first direction D1 and the second direction D2.

[0019] The main body 10A of the housing has a flat and generally rectangular shape, and in this embodiment, it has an opening 10a (e.g., Figure 2 and Figure 3The shell body 10A is a cylindrical, bottomed shell. Specifically, the shell body 10A has a bottom wall 11, a pair of side walls 12 and 13 (narrow side walls), and a pair of side walls 14 and 15 (wide side walls). Side walls 12 and 13, as well as side walls 14 and 15, constitute the peripheral side walls of the shell body 10A. In the shell body 10A, the bottom wall 11 is located at the lower end (the end opposite to the opening 10a) in the second direction D2. The bottom wall 11 has a long side extending along the first direction D1 and a short side extending along the third direction D3, forming a generally rectangular shape extending in the first direction D1 and the third direction D3. The bottom wall 11 is preferably a flat wall (bottom wall), and more preferably a flat rectangular wall (bottom wall). In addition, the side walls 12 and 13 each have a long side extending along the second direction D2 and a short side extending along the third direction D3, forming a generally rectangular shape extending in the second direction D2 and the third direction D3. A pair of sidewalls 12 and 13 are opposite each other in the first direction D1. Sidewalls 14 and 15 each have a long side extending along the first direction D1 and a short side extending along the second direction D2, forming a generally rectangular shape extending in both directions D1 and D2. A pair of sidewalls 14 and 15 are opposite each other in the third direction D3. The lower ends of sidewalls 12, 13, 14, and 15 in the second direction D2 are connected to the bottom wall 11. The bottom end of each sidewall on the bottom wall 11 side is located at the midpoint between the boundary or boundary region (e.g., a corner or R-section between each sidewall and the bottom wall 11) of the adjacent sidewalls (sidewalls 12, 13, 14, 15) and the bottom wall 11. In the main body 10A, specifically, the bottom wall 11 is connected to the bottom ends 12a of the side walls 12, 13a of the side walls 13, 14a of the side walls 14, and 15a of the side walls 15. This main body 10A is made of metal. Examples of materials used to construct the main body 10A include aluminum, aluminum alloys, iron, and iron alloys. From the viewpoint of balancing lightweight design and required rigidity, aluminum or aluminum alloys are preferred as the constituent material of the main body 10A.

[0020] The sealing plate 10B is a component that closes the opening 10a of the housing body 10A. The sealing plate 10B closes the opening 10a by being welded to the edge of the opening 10a of the housing body 10A throughout its entire circumference. In this embodiment, the sealing plate 10B is a flat plate component that is generally rectangular in plan view and has a shape capable of closing the opening 10a. Examples of materials used to construct the sealing plate 10B include aluminum, aluminum alloys, iron, and iron alloys. From the viewpoint of reducing the weight of the housing 10, aluminum or an aluminum alloy is preferred as the material for the sealing plate 10B.

[0021] The housing 10 includes a safety valve 16. In this embodiment, the safety valve 16 is located between the positive terminal 30 and the negative terminal 40 in the sealing plate 10B (upper surface) of the housing 10. The safety valve 16 is a thin-walled portion configured to rupture when the gas pressure inside the housing 10 exceeds a predetermined value. By rupturing the safety valve 16, gas inside the housing 10 is discharged outside the housing 10, preventing or suppressing further pressure increases inside the housing 10. In the housing 10, the safety valve 16 may also be provided in the housing body 10A instead of in the sealing plate 10B.

[0022] The housing 10 has an injection port (not shown) for injecting electrolyte 70 into the housing 10. The injection port is located, for example, between the positive terminal 30 and the safety valve 16 in the sealing plate 10B (upper surface) of the housing 10. Alternatively, the injection port may be located in the housing body 10A instead of in the sealing plate 10B. The injection port is sealed by a sealing member after the electrolyte 70 is injected.

[0023] like Figure 2 As shown, the housing 10 has a length L1 (first length) in the first direction D1 and a length L2 (second length) in the second direction D2. The aspect ratio (L1 / L2) of length L1 to length L2 is 2.0 or more, preferably 2.5 or more, and more preferably 2.8 or more. This structure is suitable for achieving a large volume of housing 10, and therefore suitable for achieving large-scale and high-capacity electrode bodies 20 within housing 10. The aspect ratio (L1 / L2) is preferably 4.0 or less, and more preferably 3.5 or less. This structure helps to prevent the electrolyte 70 from contacting the positive electrode tab 21T and the negative electrode tab 22T described later. Therefore, it is suitable to suppress the contact between the components and foreign matter in the electrolyte 70 and the positive electrode tab 21T and the negative electrode tab 22T. (In a non-aqueous electrolyte secondary battery with a transverse tab structure, the higher the aspect ratio of the battery casing, the higher the electrolyte level reaches the relatively lower side wall when tilted, and the easier it is for the electrolyte to contact the electrode tabs.)

[0024] In this embodiment, a plurality of electrode bodies 20 are housed within the casing 10 as described above. That is, in this embodiment, the battery 100 includes a plurality of electrode bodies 20. Figure 3 As shown, multiple electrode bodies 20 are stacked in the third direction D3 (in Figure 3 (An example is given in the case where three electrode bodies 20 are stacked). From the viewpoint of reducing dead space within the housing 10, this structure is preferred, as it helps to achieve a high volumetric energy density in the battery 100. Reducing the aforementioned dead space within the housing 10 also helps to reduce the amount of electrolyte 70 remaining, as described later.

[0025] Figure 4This is a schematic diagram showing the structure of each electrode body 20. The electrode body 20 includes a laminated structure formed by alternately arranging positive electrodes 21 and negative electrodes 22 separated by a separator 23. In this embodiment, the electrode body 20 is a wound electrode body having a strip-shaped positive electrode 21, a strip-shaped negative electrode 22, and a strip-shaped separator 23, with the positive and negative electrodes 21 and 22 wound in the long-side direction separated by the separator 23. Specifically, the electrode body 20 is a flat wound electrode body, formed by winding a strip-shaped laminate (with a width in a direction orthogonal to its long side direction) having a strip-shaped positive electrode 21, a strip-shaped separator 23, a strip-shaped negative electrode 22, and another strip-shaped separator 23 arranged sequentially. After winding, the wound electrode body can also be flattened by pressing it in the thickness direction (wound electrode body pressing process). The electrode body 20 has a third direction D3 (e.g., as shown in the diagram). Figure 3 The electrode body 20 (shown) has a flat shape. The third direction D3 intersects with the first direction D1 and the second direction D2 (orthogonal in this embodiment). Such an electrode body 20 (wound electrode body) is housed in the housing 10 along the direction of the first direction D1 with its winding axis Ax. Figure 2 Instead of the structure described above, the electrode body 20 can also be a stacked electrode body formed by stacking square positive electrodes and square negative electrodes in an insulated manner.

[0026] The positive electrode 21 has a laminated structure comprising a positive current collector 21c and a positive active material layer 21a. In this embodiment, the positive electrode 21 has a positive active material layer 21a on both sides of the positive current collector 21c. Examples of the positive current collector 21c include conductive metal foil and resin sheets with conductive metal layers on both sides. Examples of the conductive metal used for the positive current collector 21c include aluminum, aluminum alloys, nickel, titanium, and stainless steel, with aluminum being preferred. The positive active material layer 21a contains a positive active material capable of reversibly adsorbing and releasing charge carriers. The positive active material is preferably a lithium transition metal composite oxide. Specific examples of this oxide include lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel manganese composite oxide, lithium nickel cobalt composite oxide, and lithium nickel cobalt manganese composite oxide. The positive active material layer 21a may also contain additives other than the positive active material. Examples of additives include conductive materials, binders, and trilithium phosphate. Examples of conductive materials include acetylene black, Ketjen black, graphite, and carbon nanotubes. Examples of adhesives include fluorinated resins such as polyvinylidene fluoride (PVDF) and rubbers such as styrene-butadiene rubber (SBR).

[0027] The positive current collector 21c is located at one end of the electrode body 20 or the positive electrode 21 in the width direction W. Figure 4The left end of the middle section has multiple tabs 21t. The width direction W refers to the direction orthogonal to the long side direction of the above-mentioned strip-shaped laminate. In the positive current collector 21c, the tabs 21t are contained in the area exposed where the positive active material layer 21a is not laminated. In the electrode body 20, which is a wound electrode body, multiple tabs 21t overlap in the lamination direction of the above-mentioned laminated structure of the electrode body 20 to form a positive electrode tab portion 21T ( Figure 2 (As shown) (In the positive current collector 21c, a tab 21t is provided in such a configuration). The positive tab 21T functions as a current collector in the positive electrode 21. The tab 21t is connected to the positive current collector 50 (the positive current collector 50 is provided for each positive tab 21T) in such an overlapping and integrated state. As a constituent material of the positive current collector 50, aluminum and aluminum alloys are examples. As a connection method between the positive current collector 50 and the positive tab 21T in the positive electrode 21, ultrasonic bonding and laser welding are examples.

[0028] The negative electrode 22 has a laminated structure comprising a negative electrode current collector 22c and a negative electrode active material layer 22a. In this embodiment, the negative electrode 22 has a negative electrode active material layer 22a on both sides of the negative electrode current collector 22c. Examples of negative electrode current collector 22c include conductive metal foil and resin sheets with conductive metal layers on both sides. Examples of conductive metals used for the negative electrode current collector 22c include copper, copper alloys, nickel, and stainless steel, with copper foil being preferred. The negative electrode active material layer 22a contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. Examples of negative electrode active materials include carbon materials such as graphite, hard carbon, and soft carbon. Graphite can be either natural graphite or artificial graphite. The negative electrode active material layer 22a may also contain additives other than the negative electrode active material. Examples of additives include binders and thickeners. Examples of adhesives include rubbers such as styrene-butadiene rubber (SBR) and fluorinated resins such as polyvinylidene fluoride (PVDF). Examples of thickeners include cellulose-based resins such as carboxymethyl cellulose (CMC).

[0029] The negative current collector 22c has multiple tabs 22t at the other end (right end in the figure) of the electrode body 20 or the negative electrode 22 in the width direction W. In the negative current collector 22c, the tabs 22t are contained in the area exposed where the negative electrode active material layer 22a is not stacked. In the electrode body 20, which is a wound electrode body, the multiple tabs 22t overlap in the stacking direction of the aforementioned stacking structure of the electrode body 20 to form a negative electrode tab portion 22T. Figure 2(As shown) (In the negative current collector 22c, tabs 22t are provided in such a configuration). The negative tabs 22T function as current collectors in the negative electrode 22. The tabs 22t are connected to the negative current collector 60 (the negative current collector 60 is provided for each negative tab 22T) in such an overlapping and integrated state. As a constituent material of the negative current collector 60, copper and copper alloys are examples. As a connection method between the negative current collector 60 and the negative tabs 22T in the negative electrode 22, ultrasonic bonding and laser welding are examples.

[0030] The separator 23 is a component used to insulate the positive electrode 21 or the positive electrode active material layer 21a from the negative electrode 22 or the negative electrode active material layer 22a, and to maintain the ion conductivity of the electrolyte between the two layers. The separator 23 is preferably a porous resin sheet made of polyolefin resin. Examples of polyolefin resins include polyethylene (PE) and polypropylene (PP). A heat resistance layer (HRL) containing inorganic fillers may also be provided on the surface of the separator 23. Examples of materials constituting the inorganic fillers include alumina, boehmite, aluminum hydroxide, and titanium dioxide.

[0031] Figure 5 This is a magnified schematic diagram showing a portion of the electrode body 20, primarily located at and near the negative electrode 22. (See attached diagram.) Figure 5 As shown, the negative electrode 22 includes a counter portion 22F and a non-counter-edge end 22E. The negative electrode 22 has non-counter-edge ends 22E at both ends in the width direction W. The counter portion 22F is the region of the negative electrode 22 that is opposite to the positive electrode 21 across the separator 23. The non-counter-edge end 22E is the region of the negative electrode 22 that is not opposite to the positive electrode 21 across the separator 23. The negative electrode active material layer 22a of such a negative electrode 22 has a groove portion 22g. The groove portion 22g is the portion where the surface of the negative electrode active material layer 22a retracts from the separator 23 at the boundary region between the counter portion 22F and the non-counter-edge end 22E, or at the non-counter-edge end 22E. The groove portion 22g can be provided throughout the entire long side direction of the negative electrode active material layer 22a, or it can be provided in a portion thereof. The ratio of the depth of the groove 22g to the thickness of the negative electrode active material layer 22a is preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.7 or more, and preferably 0.95 or less, more preferably 0.85 or less, and even more preferably 0.80 or less. This structure is preferred for the groove 22g to function effectively as a storage space for the electrolyte 70. The depth of the groove 22g refers to the length (dimension) between the open end and the deepest part of the groove 22g in the thickness direction of the negative electrode active material layer 22a. Such a groove 22g can be formed, for example, by adjusting the pressing pressure in the above-mentioned winding electrode pressing process during the manufacturing process of the electrode body 20.

[0032] like Figure 2 As shown, within the housing 10, each electrode body 20 of the above structure has a positive electrode tab 21T at one end in the first direction D1 and a negative electrode tab 22T at the other end. The sidewall 12 of the housing 10 or housing body 10A faces the positive electrode tab 21T in the first direction D1 and extends along the second direction D2. The sidewall 13 faces the negative electrode tab 22T in the first direction D1 and extends along the second direction D2. Furthermore, the positive electrode tab 21T and the negative electrode tab 22T are located on the side opposite to the bottom wall 11 relative to the central position P of the electrode body 20 in the second direction D2. This structure helps to prevent the positive electrode tab 21T and the negative electrode tab 22T from contacting the electrolyte 70, thus effectively suppressing contact between components and foreign matter in the electrolyte 70 and the positive electrode tab 21T and the negative electrode tab 22T.

[0033] like Figure 1 and Figure 2 As shown, the positive terminal 30 is mounted on the sealing plate 10B. For example, the sealing plate 10B has a terminal opening extending through its thickness direction, and the positive terminal 30 is mounted with an insulating washer sandwiched between it and the sealing plate 10B relative to this opening. As a method of mounting the positive terminal 30 relative to the sealing plate 10B, riveting is an example (the mounting method for the negative terminal 40 described later is the same). The positive terminal 30 is exposed both outside and inside the housing 10. Inside the housing 10, the positive terminal 30 is connected to the positive current collector 50. As a connection method, laser welding is an example. Such a positive terminal 30 is preferably made of aluminum or an aluminum alloy.

[0034] The negative terminal 40 is mounted on the sealing plate 10B. The negative terminal 40 is exposed both externally and internally of the housing 10. Inside the housing 10, the negative terminal 40 is connected to the negative current collector 60. Laser welding can be used as a connection method. This negative terminal 40 is preferably made of copper or a copper alloy.

[0035] The electrolyte 70 and the electrode body 20 are housed together inside the casing 10. The electrolyte 70 is immersed in the electrode body 20. The electrolyte 70 is a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte (supporting salt). Examples of non-aqueous solvents include ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). The electrolyte is, for example, a fluorinated lithium salt. Examples of fluorinated lithium salts include lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiN(SO2F)2). Residual electrolyte 70 not immersed in the electrode body 20 is also stored inside the casing 10.

[0036] The ratio (injection ratio) of the amount of electrolyte 70 injected into the housing 10 to the sum of the void amounts of the multiple layers constituting the electrode body 20 is preferably 1.10 or more, more preferably 1.15 or more, and even more preferably 1.20 or more. This structure is preferred to prevent insufficient impregnation of the electrolyte 70 with the electrode body 20. The above-mentioned injection ratio is preferably 1.40 or less, more preferably 1.30 or less, and even more preferably 1.25 or less. Suppressing the amount of electrolyte 70 to this extent helps to prevent contact between the positive electrode tab 21T and the negative electrode tab 22T and the electrolyte 70, thus it is suitable to suppress the contact between components and foreign matter in the electrolyte 70 and the positive electrode tab 21T and the negative electrode tab 22T. The voids in the layers constituting the electrode body 20 refer to the voids through which the electrolyte 70 can impregnate from outside the electrode body 20. In this embodiment, the porosity of the multiple layers constituting the electrode body 20 includes the porosity of the positive electrode active material layer 21a, the porosity of the negative electrode active material layer 22a, and the porosity of the separator 23. The porosity of a layer can be calculated by the product of its area, thickness, and porosity. The porosity of a layer can be calculated, for example, based on the actual volume of the layer measured by a mercury porosimeter and the theoretical volume of the layer calculated from the battery material.

[0037] The amount of electrolyte 70 per unit energy density (Wh / L) in battery 100 is preferably 0.80 g·L / Wh or less, more preferably 0.75 g·L / Wh or less, and even more preferably 0.70 g·L / Wh or less. Suppressing the amount of electrolyte 70 to this level helps to prevent contact between the positive electrode tab 21T and the negative electrode tab 22T and the electrolyte 70, thus appropriately suppressing contact between components and foreign matter in the electrolyte 70 and the positive electrode tab 21T and the negative electrode tab 22T.

[0038] In the battery 100, the length L1 of the casing 10 is relative to the length L of the electrode body 20 in the first direction D1. E (like Figure 2 The ratio (L1 / L) shown) E The value is preferably 1.010 or higher, more preferably 1.030 or higher, and even more preferably 1.050 or higher. This structure ensures a space S within the housing 10 for storing residual electrolyte 70 that is not impregnated with the electrode body 20. Figure 2 As shown, the ratio (L1 / L) is preferred. E The electrolyte concentration is preferably 1.100 or less, more preferably 1.070 or less, and even more preferably 1.055 or less. This structure is preferred from the viewpoint of reducing the remaining amount of electrolyte 70. Reducing the remaining amount of electrolyte 70 helps to prevent the electrolyte 70 from contacting the electrode tabs (positive electrode tab 21T, negative electrode tab 22T) when the battery is tilted (the more remaining electrolyte, the closer the liquid surface 70a of the electrolyte 70 tends to be to the electrode tabs when the battery is tilted).

[0039] Figure 6 and Figure 7 This is an example of the tilted state of battery 100. Figure 6 The casing 10 of the battery 100 is in a state where the imaginary line PL passing through the bottom end 12a of the side wall 12 and the bottom end 13a of the side wall 13 is tilted at a 45-degree angle relative to the horizontal, and the side wall 12 is located relatively below the side wall 13 (first tilt state). Figure 7 This indicates the state where the imaginary line PL is tilted at a 45-degree angle relative to the horizontal, and sidewall 13 is positioned relatively below sidewall 12 (second tilted state). When the bottom wall 11 is flat, as... Figure 6 and Figure 7 As shown, the imaginary line PL passing through the bottom ends 12a and 13a of the sidewalls 12 and 13 also passes through the flat bottom wall 11. When the boundary region between the interconnected sidewalls 12 and 13 and the bottom wall 11 is R-section, the bottom ends 12a and 13a of the sidewalls 12 and 13 are located at the midpoint of the boundary region as described above, and the imaginary line PL passes through such bottom ends 12a and 13a. Furthermore, the battery 100 is configured such that, regardless of whether it is in the first or second tilted state, the electrolyte 70 inside the casing 10 does not contact the positive electrode tab 21T and the negative electrode tab 22T. Preferably, the bottom wall 11 is flat, and when the imaginary line PL extending along the first direction D1 through such bottom wall 11 and bottom ends 12a and 13a is tilted at a 45-degree angle relative to the horizontal, the electrolyte 70 inside the casing 10 does not contact the positive electrode tab 21T and the negative electrode tab 22T. In this case, it is more preferable that the bottom wall 11 is a rectangular flat plate. In addition, the battery 100 is configured such that although the amount of electrolyte 70 present outside the electrode body 20 inside the casing 10 varies depending on the charging and discharging of the battery 100, the electrolyte 70 does not come into contact with the positive electrode tab 21T and the negative electrode tab 22T even if the amount of electrolyte varies in this way.

[0040] In the battery 100 with the structure described above, as mentioned above, the ratio of the length L1 to the length L2 of the casing 10, i.e., the length-to-width ratio (L1 / L2), is 2.0 or higher. This is suitable for achieving a large volume of the casing 10, and therefore suitable for achieving a large size and high capacity of the electrode body 20 within the casing 10. In addition, in the battery 100 with a lateral tab structure, in the state where the above-mentioned imaginary line PL is tilted at a 45-degree angle relative to the horizontal (first tilt state, second tilt state), the electrolyte 70 within the casing 10 does not come into contact with the positive electrode tab 21T and the negative electrode tab 22T. This is suitable for suppressing the contact between the components and foreign matter in the electrolyte 70 and the positive electrode tab 21T and the negative electrode tab 22T. When the battery 100 is installed in a vehicle, for example as a power source for driving the vehicle, it is suitable for suppressing the contact between components and foreign matter in the electrolyte 70 and the positive electrode tab 21T and the negative electrode tab 22T, not only when the vehicle is driving on flat ground or parked, but also when driving on slopes and bumpy roads. Therefore, the battery 100 is suitable for maintaining battery performance while achieving high capacity.

[0041] The higher the aforementioned aspect ratio (L1 / L2), the higher the position 70h of the electrolyte level 70a (upper end face) in the relatively lower sidewall (sidewall 12 or sidewall 13) of the sidewalls 12 and 13 tends to be when the battery 100 or the casing 10 is tilted. In a non-aqueous electrolyte secondary battery with a lateral tab structure, the higher the position of the electrolyte level when the battery is tilted, the easier it is for the electrolyte to contact the electrode tabs. Contact between the electrolyte and the electrode tabs may reduce the function of the electrode tabs and even the battery performance, so it is not preferred. In contrast, since the battery 100 is configured such that the electrolyte 70 does not contact the positive electrode tab 21T and the negative electrode tab 22T in the first and second tilted states described above, it is suitable for maintaining battery performance.

[0042] Battery 100 can be used for various purposes. For example, battery 100 can be suitably used as a power source (drive power source) for motors in vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0043] Furthermore, the battery disclosed herein can also be an energy storage device other than a lithium-ion battery. Energy storage devices, in addition to batteries commonly referred to as lithium-ion batteries, lithium secondary batteries, etc., also include batteries such as nickel-metal hydride batteries. In this specification, "energy storage device" generally refers to a device that can be repeatedly charged and discharged.

[0044] The present invention has been described above in various ways. Unless specifically mentioned, the embodiments listed herein are not intended to limit the invention. Furthermore, the present invention is capable of various modifications; unless specific problems arise, the constituent elements and processes mentioned herein can be appropriately omitted or combined. Additionally, this specification includes the following disclosures.

[0045] Item 1:

[0046] A secondary battery includes an electrode body, a non-aqueous electrolyte, and a casing containing the electrode body and the non-aqueous electrolyte, wherein...

[0047] The aforementioned electrode body has a positive electrode tab at one end in the first direction and a negative electrode tab at the other end.

[0048] The aforementioned shell includes a bottom wall, a first side wall, and a second side wall.

[0049] The first sidewall is opposite to the positive electrode tab in the first direction and extends along a second direction that intersects the first direction.

[0050] The second sidewall is opposite to the negative electrode tab in the first direction and extends along the second direction.

[0051] The bottom wall is connected to the bottom end of the first side wall in the second direction and the bottom end of the second side wall in the second direction.

[0052] The aspect ratio of the first length of the aforementioned housing in the first direction to the second length of the aforementioned housing in the second direction is 2.0 or more.

[0053] With the imaginary line passing through the bottom ends of the first and second side walls at a 45-degree angle relative to the horizontal, the non-aqueous electrolyte inside the casing does not contact the positive and negative electrode tabs.

[0054] Item 2:

[0055] In the secondary battery described in item 1, the aspect ratio is 4.0 or less.

[0056] Item 3:

[0057] In the secondary battery described in item 1 or 2, the amount of the above-mentioned non-aqueous electrolyte per unit energy density (Wh / L) is less than 0.80 g·L / Wh.

[0058] Item 4:

[0059] In any of the secondary batteries described in items 1 to 3, the ratio of the first length of the casing to the length of the electrode body in the first direction is 1.100 or less.

[0060] Item 5:

[0061] In any of the secondary batteries described in items 1 to 4, the positive electrode tab and the negative electrode tab are respectively located on the side opposite to the bottom wall relative to the central position of the electrode body in the second direction.

[0062] Item 6:

[0063] In any of the secondary batteries described in items 1 to 5, the electrode body is a wound electrode body having a strip-shaped positive electrode, a strip-shaped negative electrode and a strip-shaped separator, and formed by winding the positive electrode and the negative electrode in the long side direction with the separator in between, and having a flat shape in a third direction that intersects the first direction and the second direction.

[0064] Item 7:

[0065] In the secondary battery described in item 6,

[0066] The aforementioned negative electrode has a laminated structure comprising a negative electrode current collector and a negative electrode active material layer, and includes a opposed portion that faces the aforementioned positive electrode across the aforementioned separator, and a non-opposed edge portion that faces the aforementioned positive electrode across the aforementioned separator.

[0067] The negative electrode active material layer has a groove formed by the surface of the negative electrode active material layer retracting from the diaphragm at the boundary region between the opposing portion and the non-opposing edge end, or at the non-opposing edge end.

[0068] Item 8:

[0069] In the secondary battery described in item 6 or item 7, the electrode body includes a plurality of the wound electrode bodies, and the plurality of wound electrode bodies are stacked in the third direction within the housing.

[0070] Item 9:

[0071] In any of the secondary batteries described in items 1 to 8, the ratio of the amount of the non-aqueous electrolyte to the sum of the void amounts of the multiple layers constituting the electrode body is 1.10 or more.

Claims

1. A secondary battery comprising an electrode body, a non-aqueous electrolyte, and a casing for containing the electrode body and the non-aqueous electrolyte. The secondary battery is characterized in that... The electrode body has a positive electrode tab at one end in the first direction and a negative electrode tab at the other end. The housing includes a bottom wall, a first side wall, and a second side wall. The first sidewall is opposite to the positive electrode tab in the first direction and extends along a second direction that intersects the first direction. The second sidewall is opposite to the negative electrode tab in the first direction and extends along the second direction. The bottom wall is connected to the bottom end of the first side wall in the second direction and the bottom end of the second side wall in the second direction. The aspect ratio of the first length of the housing in the first direction to the second length of the housing in the second direction is 2.0 or greater. With the imaginary line passing through the bottom end of the first sidewall and the bottom end of the second sidewall at a 45-degree angle relative to the horizontal, the non-aqueous electrolyte inside the housing does not contact the positive electrode tab or the negative electrode tab.

2. The secondary battery according to claim 1, characterized in that, The aspect ratio is 4.0 or less.

3. The secondary battery according to claim 1, characterized in that, The amount of the non-aqueous electrolyte per unit energy density, i.e. per Wh / L, is less than 0.80 g·L / Wh.

4. The secondary battery according to claim 1, characterized in that, The ratio of the first length of the housing to the length of the electrode body in the first direction is 1.100 or less.

5. The secondary battery according to claim 1, characterized in that, The positive electrode tab and the negative electrode tab are respectively located on the side opposite to the bottom wall relative to the center position of the electrode body in the second direction.

6. The secondary battery according to claim 1, characterized in that, The electrode body is a wound electrode body having a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped diaphragm, and is formed by winding the positive electrode and the negative electrode in the long side direction with the diaphragm in between, and has a flat shape in a third direction that intersects the first direction and the second direction.

7. The secondary battery according to claim 6, characterized in that, The negative electrode has a laminated structure comprising a negative electrode current collector and a negative electrode active material layer, and includes a opposed portion that faces the positive electrode across the membrane, and a non-opposed edge portion that does not face the positive electrode across the membrane. The negative electrode active material layer has a groove formed by the surface of the negative electrode active material layer retracting from the diaphragm at the boundary region between the opposing portion and the non-opposing edge end, or at the non-opposing edge end.

8. The secondary battery according to claim 6, characterized in that, The electrode body comprises a plurality of the wound electrode bodies. Within the housing, the plurality of wound electrode bodies are stacked in the third direction.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The ratio of the amount of the non-aqueous electrolyte to the sum of the void amounts of the multiple layers constituting the electrode body is 1.10 or more.

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