Lithium secondary battery

Abstract

A lithium secondary battery comprises: an electrode group in which a band-shaped positive electrode and a band-shaped negative electrode are wound with a separator interposed therebetween; and a non-aqueous electrolyte. The positive electrode has a positive electrode current collector and a positive electrode mixture layer that is disposed on the positive electrode current collector. The positive electrode has one or more positive electrode current collector exposed portions at which the positive electrode current collector is exposed, and the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which a positive electrode lead is fixed. The negative electrode includes one or more negative electrode lead fixing portions to which a negative electrode lead is fixed. The negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions in a radial direction that is perpendicular to the winding axis, with the separator interposed therebetween.

Description

Lithium secondary battery CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-147991, filed on August 29, 2024, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a lithium secondary battery comprising a lithium ion conductive non-aqueous electrolyte.

[0003] Non-aqueous electrolyte secondary batteries are used in applications such as ICT (Information Communication Technology) applications such as personal computers and smartphones, in-vehicle applications, and power storage. In these applications, non-aqueous electrolyte secondary batteries are required to have even higher capacities. Lithium-ion batteries are known as high-capacity non-aqueous electrolyte secondary batteries. Higher capacities in lithium-ion batteries can be achieved by using, for example, graphite and an alloy active material such as a silicon compound as the negative electrode active material. However, the capacity of lithium-ion batteries is reaching its limit.

[0004] Lithium secondary batteries (lithium metal secondary batteries) are promising non-aqueous electrolyte secondary batteries with a higher capacity than lithium ion batteries. In lithium secondary batteries, lithium metal precipitates on the negative electrode during charging, and this lithium metal dissolves in the non-aqueous electrolyte during discharge.

[0005] Patent Document 1 proposes "a wound lithium secondary battery formed by winding, via a separator, a positive electrode body having a lead terminal provided on a current collector coated with a positive electrode mixture, and a negative electrode body having a lead terminal provided on lithium metal or a lithium alloy, wherein at least one of the lead terminals of the positive electrode body or the negative electrode body is provided on the innermost periphery of the winding core of the wound body, and the lead terminal of the positive electrode body or the lead terminal of the negative electrode body is provided in a region where the positive electrode body and the negative electrode body do not face each other."

[0006] Patent Document 2 proposes a lithium secondary battery comprising: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte having lithium ion conductivity, wherein lithium metal is deposited on the negative electrode during charging and the lithium metal is dissolved from the negative electrode during discharging; a spacer is provided between at least one of the positive electrode and the negative electrode and the separator; a first length of the separator in a first direction D1 is smaller than a second length of the separator in a second direction D2 intersecting with the first direction D1; and in a cross section of the spacer taken along the thickness direction of the separator and the first direction D1, at least one of an angle formed between the separator and the spacer on the spacer side and an angle formed between the spacer and an electrode in contact with the spacer is greater than 90°.

[0007] JP 2000-260473 A International Publication No. 2021 / 192645

[0008] In lithium secondary batteries, lithium metal is repeatedly deposited on the negative electrode and dissolved in the non-aqueous electrolyte during charge and discharge, which causes stress to accumulate in the electrode due to expansion and contraction of the negative electrode, making the electrodes more susceptible to breakage (fracture) and buckling deformation than in general cylindrical non-aqueous electrolyte batteries (e.g., lithium ion batteries).

[0009] As a countermeasure to this problem, a method of providing at least one of the positive electrode lead and the negative electrode lead on the innermost periphery of the winding core of the wound body as in Patent Document 1, and a method of forming a spacer layer on the separator to provide a space for lithium metal to deposit as in Patent Document 2 have been proposed. However, these methods are not sufficient countermeasures, and it is desired to suppress electrode folding (fracture) and buckling deformation at a high level.

[0010] The breakage (fracture) and buckling deformation of the electrode can occur due to stress applied to the electrode caused by the expansion and contraction of the negative electrode during charging and discharging. In particular, if the negative electrode lead is provided on the innermost side of the winding core of the wound body, stress is likely to be applied to the electrode on the inner side of the wound body, making the electrode more likely to break (fracture) and buckle. On the other hand, if the negative electrode lead is provided on the outermost side of the winding core of the wound body, stress concentration on the electrode on the inner side of the wound body can be suppressed, and the breakage (fracture) and buckling deformation of the electrode can be suppressed. However, the increase in the length of the current path from the lead portion to the innermost side of the negative electrode may increase the resistance of the lithium secondary battery.

[0011] One aspect of the present disclosure provides an electrode assembly including a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator interposed between them, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further includes one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly, and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, and the negative electrode has at least a negative electrode current collector, and during charging, a positive electrode mixture layer is formed on the negative electrode current collector. the positive electrode has one or more positive electrode current collector exposed portions where the positive electrode current collector is exposed, and the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which the positive electrode lead is fixed; the negative electrode includes one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, and the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions with the separator interposed therebetween in a radial direction perpendicular to the winding axis.

[0012] Another aspect of the present disclosure provides an electrode assembly including a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator interposed between them, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further includes: one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly; and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, and the negative electrode contains lithium metal or a lithium alloy disposed on the negative electrode current collector. the positive electrode has one or more positive electrode current collector exposed portions where the positive electrode current collector is exposed, and the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which the positive electrode lead is fixed; the negative electrode has one or more negative electrode current collector exposed portions where the negative electrode current collector is exposed, and the one or more negative electrode current collector exposed portions include one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, and the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions with the separator interposed therebetween in a radial direction perpendicular to the winding axis.

[0013] Another aspect of the present disclosure provides an electrode assembly including a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator interposed between them, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further includes one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly, and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, and the negative electrode is a lithium metal or lithium ion battery disposed on the negative electrode current collector. the positive electrode has one or more positive electrode current collector exposed portions where the positive electrode current collector is exposed, the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which the positive electrode lead is fixed; the lithium layer includes one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, the negative electrode lead fixing portions facing one of the one or more positive electrode current collector exposed portions with the separator interposed therebetween in a radial direction perpendicular to the winding axis; and the negative electrode lead is fixed to the lithium layer.

[0014] According to the present disclosure, it is possible to suppress an increase in the resistance of a lithium secondary battery that occurs with repeated charge and discharge cycles. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0015] 1 is a longitudinal sectional view schematically showing a lithium secondary battery according to an embodiment of the present disclosure; FIG. 2 is an enlarged view schematically showing a main part of the lithium secondary battery of FIG. 1; FIG. 3 is a top view showing a state before winding of a positive electrode and a negative electrode used in the lithium secondary battery of FIG. 1; FIG. 4 is a top view showing another example of a state before winding of a positive electrode and a negative electrode used in the lithium secondary battery of FIG. 1; FIG. 5 is a top view showing another example of a state before winding of a positive electrode and a negative electrode used in the lithium secondary battery of FIG. 1; FIG. 6 is a top view showing another example of a state before winding of a positive electrode and a negative electrode used in the lithium secondary battery of FIG. 1;

[0016] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or greater and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not greater than the upper limit. In the following description, when examples of components or methods are listed, only one of the listed examples may be used, or multiple of the listed examples may be used in combination, unless otherwise specified.

[0017] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0018] A lithium secondary battery according to an embodiment of the present disclosure includes an electrode group including a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator interposed therebetween, and a nonaqueous electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector. The lithium secondary battery further includes one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode group, and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode group.

[0019] The negative electrode has at least a negative electrode current collector. The negative electrode is an electrode in which lithium metal is deposited on the negative electrode current collector during charging and dissolves in a non-aqueous electrolyte during discharging. Here, "lithium metal is deposited on the negative electrode current collector" does not necessarily mean that the deposited lithium metal is in direct contact with the negative electrode current collector and that lithium metal is deposited on the surface of the negative electrode current collector, but also means that another layer (e.g., a lithium layer described below) is present on the negative electrode current collector and lithium metal is deposited on the surface of that layer. Hereinafter, the positive electrode and negative electrode may be collectively referred to as "electrodes."

[0020] In a lithium secondary battery, for example, 70% or more of the rated capacity is achieved by the deposition and dissolution of lithium metal. The movement of electrons at the negative electrode during charging and discharging is mainly due to the deposition and dissolution of lithium metal at the negative electrode. Specifically, 70 to 100% (e.g., 80 to 100% or 90 to 100%) of the movement of electrons (or current from another perspective) at the negative electrode during charging and discharging is due to the deposition and dissolution of lithium metal. In other words, the negative electrode of a lithium secondary battery differs from a negative electrode in which the movement of electrons at the negative electrode during charging and discharging is mainly due to the absorption and release of lithium ions by the negative electrode active material (e.g., graphite).

[0021] The positive electrode has one or more positive electrode current collector exposed portions where the positive electrode current collector is exposed. The positive electrode current collector exposed portions are portions of the positive electrode where the positive electrode mixture layer is not formed and the positive electrode current collector is exposed. The positive electrode current collector exposed portions preferably have the same width in the winding axis direction as the width of the positive electrode current collector in the winding axis direction. That is, the positive electrode current collector exposed portions are preferably continuously disposed across the entire width of the positive electrode current collector in the winding axis direction, from the first side to the second side in the winding axis direction.

[0022] The one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which a positive electrode lead is fixed. The negative electrode includes one or more negative electrode lead fixing portions to which a negative electrode lead is fixed. A positive electrode lead and a negative electrode lead are attached to at least one of the positive electrode lead fixing portions and the negative electrode lead fixing portions, respectively, and are used for electrical connection with an external terminal of the battery. The negative electrode lead fixing portion preferably has the same width in the direction of the winding axis as the width of the negative electrode current collector in the direction of the winding axis. In other words, the negative electrode lead fixing portion is preferably continuously disposed across the entire width of the negative electrode current collector in the direction of the winding axis, from the first side to the second side, in the direction of the winding axis.

[0023] The positive electrode current collector exposed portion and / or the negative electrode lead fixing portion may be disposed on both sides of the positive electrode or negative electrode, respectively, in corresponding regions on a first surface and a second surface opposite to the first surface.

[0024] The negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions in the radial direction perpendicular to the winding axis, with the separator (one circumference of the separator) interposed between them. The positive electrode current collector exposed portion facing the negative electrode lead fixing portion may be the positive electrode lead fixing portion, or may be a positive electrode current collector exposed portion that does not constitute the positive electrode lead fixing portion.

[0025] The region of the positive electrode facing the negative electrode lead fixing portion via the separator is an exposed portion of the positive electrode current collector where no positive electrode mixture layer is disposed, and has a step (recess). By disposing the negative electrode lead in the space formed by this recess, the electrode is prevented from being distorted around the negative electrode lead, preventing a decrease in the circularity of the electrode assembly. As a result, uneven charge / discharge reactions are prevented in the electrode winding direction, thereby preventing electrode breakage (fracture) and buckling deformation caused by localized accumulation of stress due to expansion and contraction of the negative electrode. Separator collapse is also suppressed. As a result, the increase in resistance of the lithium secondary battery due to repeated charge / discharge cycles can be suppressed, improving the cycle capacity retention rate.

[0026] Furthermore, the region of the positive electrode facing the negative electrode lead fixing part via the separator does not contribute to charge and discharge even if a positive electrode mixture layer is disposed therein. Therefore, by making the region of the positive electrode facing the negative electrode lead fixing part a positive electrode current collector exposed portion, it is possible to reduce the positive electrode mixture layer that does not contribute to charge and discharge. It is also easy to increase the connection area with the negative electrode lead within the negative electrode lead fixing part, which reduces the resistance of the negative electrode and makes it easier to realize a high-power lithium secondary battery.

[0027] To achieve a high-capacity lithium secondary battery, the positive electrode lead may be fixed to the positive electrode lead fixing portion so that it at least partially overlaps with the negative electrode lead opposing portion, which faces the negative electrode lead via a separator, in the winding axis direction. This configuration allows the positive electrode lead and the negative electrode lead to be arranged in a localized area in the winding direction (the longitudinal direction of the strip-shaped electrode), thereby increasing the circularity of the electrode assembly. As a result, the capacity of the lithium secondary battery increases. Note that "the positive electrode lead at least partially overlaps with the negative electrode lead opposing portion in the winding axis direction" means that, when the positive electrode is viewed from the main surface on the side where the positive electrode lead is attached, there is a straight line parallel to the winding axis direction that passes through both the positive electrode lead and the negative electrode lead opposing portion.

[0028] On the other hand, the positive electrode lead may be fixed to the positive electrode lead fixing portion so as not to overlap with the negative electrode lead opposing portion in the winding axis direction. In this case, the negative electrode lead may be disposed in the negative electrode lead fixing portion from the second side toward the first side, past the central position of the positive electrode current collector in the winding axis direction. Similarly, the positive electrode lead may be disposed in the positive electrode lead fixing portion from the first side toward the second side, past the central position of the positive electrode current collector in the winding axis direction. In this case, when a line is drawn that passes through the central position of the positive electrode current collector in the winding axis direction and is parallel to the winding direction (longitudinal direction of the electrode), the line passes through both the positive electrode lead and the negative electrode lead opposing portion.

[0029] The negative electrode lead may be fixed to the negative electrode current collector, or in the case of a negative electrode having a lithium layer containing lithium metal or a lithium alloy disposed on the negative electrode current collector, the negative electrode lead may be fixed to the lithium layer.

[0030] A negative electrode having a lithium layer may have one or more negative electrode current collector exposed portions where the negative electrode current collector is exposed. The negative electrode current collector exposed portions are portions of the negative electrode where no lithium layer is formed and the negative electrode current collector is exposed. The negative electrode current collector exposed portions preferably have the same width in the direction of the winding axis as the width of the negative electrode current collector in the direction of the winding axis. That is, the negative electrode current collector exposed portions are preferably arranged continuously across the entire width of the negative electrode current collector in the direction of the winding axis, from the first side to the second side in the direction of the winding axis.

[0031] At least one of the one or more negative electrode current collector exposed portions may constitute a negative electrode lead fixing portion. In this case, the negative electrode lead is fixed to the negative electrode current collector at a negative electrode current collector exposed portion on which no lithium layer is formed.

[0032] In a negative electrode having a lithium layer, the lithium layer may include one or more negative electrode lead fixing parts. In this case, the negative electrode lead is fixed to the lithium layer at the negative electrode lead fixing parts.

[0033] A negative electrode having a lithium layer is an electrode in which lithium metal is deposited on the negative electrode current collector or the lithium layer during charging, and the lithium metal dissolves in the non-aqueous electrolyte during discharging.

[0034] The positive electrode lead fixing portion and the negative electrode lead fixing portion may be positioned close to each other. Typically, the positive electrode lead is positioned near the center in the longitudinal direction, at a location sufficiently distant from both the winding start end and the winding end end of the positive electrode. In this case, the negative electrode lead may also be positioned near the center in the longitudinal direction, at a location sufficiently distant from both the winding start end and the winding end end of the negative electrode. By positioning the positive electrode lead and the negative electrode lead close to each other, the current collection path is shortened and the electrical resistance is reduced. Therefore, a lithium secondary battery with low resistance and high output can be easily realized.

[0035] As described above, when the positive electrode lead and the negative electrode lead opposing portion are fixed so that they at least partially overlap in the winding axis direction, the positive electrode lead and the negative electrode lead can be positioned at the same or close to each other in the radial direction of the electrode group.

[0036] However, when the positive electrode lead and the negative electrode lead facing portion are fixed so as not to overlap in the winding axis direction, if the positive electrode lead and the negative electrode lead are positioned at the same or close radial positions of the electrode group, the shape of the electrode group is likely to become distorted and the circularity is reduced. As a result, the charge / discharge reaction becomes non-uniform in the winding direction of the electrode, and stress due to expansion and contraction of the negative electrode accumulates locally, which may cause the electrode to break (fracture) and buckle. In order to suppress the electrode to break (fracture) and buckle and to suppress the increase in resistance of the lithium secondary battery due to repeated charge / discharge cycles, it is preferable that the positive electrode lead and the negative electrode lead are arranged so as not to overlap each other in the radial direction perpendicular to the winding axis direction.

[0037] The positive electrode lead and the portion of the positive electrode facing the negative electrode lead may be located at a position not less than L / 5 and not more than L / 2 from the winding start end of the positive electrode, where L is the length in the winding direction (longitudinal direction) of the positive electrode, and are preferably located not less than L / 4 and not more than 2L / 5 from the winding start end of the positive electrode.

[0038] The lithium secondary battery may have two or more positive electrode current collector exposed portions arranged at a distance in the longitudinal direction of the positive electrode. In this case, at least one of the two or more positive electrode current collector exposed portions constitutes a positive electrode lead fixing part. Of the two or more positive electrode current collector exposed portions, the positive electrode current collector exposed portion constituting the positive electrode lead fixing part may face the negative electrode lead fixing part via a separator in the radial direction perpendicular to the winding axis, and at least one remaining positive electrode current collector exposed portion that does not constitute the positive electrode lead fixing part may face the negative electrode lead fixing part via a separator in the radial direction perpendicular to the winding axis.

[0039] The electrode group can be housed in a bottomed cylindrical outer can together with a nonaqueous electrolyte. In this case, the negative electrode (negative electrode current collector and / or lithium layer) may be exposed at the outermost periphery of the electrode group. The exposed portion of the negative electrode at the outermost periphery of the electrode group may be in contact with the inner circumferential surface of the outer can. This forms a current collection path via the exposed portion of the negative electrode separate from the current collection path via the negative electrode lead, thereby reducing electrical resistance and easily realizing a high-power lithium secondary battery.

[0040] The negative electrode current collector may include stainless steel (SUS) because it has high breaking strength and is less likely to break under stress caused by expansion and contraction of the negative electrode. The stainless steel is not particularly limited, and may be ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, austenitic-ferritic stainless steel, or precipitation hardened stainless steel. Among these, ferritic stainless steel has excellent breaking strength. Austenitic stainless steel may be used because of its excellent corrosion resistance. Ferritic stainless steel includes SUS430. Austenitic stainless steel includes SUS304, SUS301, SUS310S, SUS316, etc.

[0041] The negative electrode may have a lithium metal or lithium alloy layer (lithium layer) formed on a SUS steel negative electrode current collector. The negative electrode may be a clad material in which the lithium layer is attached to the SUS steel by pressure bonding, or the lithium layer may be formed on the SUS steel by plating or vapor deposition.

[0042] The lithium layer may be, for example, a lithium alloy layer composed of lithium and an element other than lithium. Examples of the other element (e.g., another metal element) include magnesium (Mg), aluminum (Al), indium (In), copper (Cu), zinc (Zn), potassium (K), calcium (Ca), sodium (Na), silver (Ag), and gold (Au). The content of the other element may be 5% by mass or less (e.g., 1% by mass or less). The lithium alloy may contain Mg or Al as the element other than lithium.

[0043] The lithium secondary battery preferably further includes a spacer layer having convex portions arranged in a predetermined repeating pattern between at least one of the positive electrode and the negative electrode and the separator. The convex portions provide a space between at least one of the positive electrode and the negative electrode and the separator. The spacer layer may be provided on at least one member selected from the group consisting of the positive electrode, the negative electrode, and the separator. The spacer layer forms a space between the positive electrode and the separator or between the negative electrode and the separator, and suppresses expansion of the negative electrode during charge and discharge.

[0044] The spacer layer ensures a space for lithium metal to deposit on the negative electrode surface, reducing volumetric changes in the negative electrode associated with lithium metal deposition. The spacer layer is provided as a convex portion on at least one of the positive electrode, negative electrode, and separator. The spacer layer or convex portion may be provided on the surface of the positive electrode, the surface of the negative electrode, or the surface of the separator facing the positive electrode or negative electrode. The convex portion provided on the surface of the positive electrode and / or the surface of the separator facing the positive electrode forms a space between the positive electrode and the separator, while the convex portion provided on the surface of the negative electrode and / or the surface of the separator facing the negative electrode forms a space between the negative electrode and the separator. The space suppresses expansion of the negative electrode during charge and discharge, thereby suppressing deterioration of cycle characteristics.

[0045] The spacer layer may have convex portions arranged in a predetermined repeating pattern. The predetermined repeating pattern may be a straight or curved line pattern, a dot pattern, or a mesh pattern. A mesh pattern is obtained by connecting a plurality of straight and / or curved line patterns to form a mesh. A dot pattern corresponds to a case where the extension length (length of the straight or curved lines) of the line convex portions is as short as the line width of the line convex portions.

[0046] The spacer layer may include at least a first linear portion along a first geometric pattern and a second linear portion along a second geometric pattern. In addition to the first and second portions, the spacer layer may include a third linear portion along a third geometric pattern. The first and second portions may be disposed in a first region and a second region, respectively, on the surface of at least one member selected from the group consisting of a positive electrode, a negative electrode, and a separator. The first region is a portion closer to the center in a first direction parallel to the winding axis. The second region is located further outward from the center than the first region in the first direction parallel to the winding axis.

[0047] The first geometric pattern may be, for example, a substantially linear pattern extending along the second direction, or a pattern in which a plurality of linear protrusions are arranged (continuously or intermittently) along a plurality of straight lines substantially parallel to the second direction.

[0048] The second geometric pattern may be, for example, a substantially linear pattern extending along the second direction, or may be a mesh pattern. The second geometric pattern as a linear pattern may be, for example, a pattern in which a plurality of linear protrusions are intermittently arranged along a plurality of straight lines substantially parallel to the second direction. In this case, the plurality of linear protrusions may be arranged in a staggered pattern.

[0049] The shape of the mesh of the mesh pattern is not particularly limited, but may be polygonal, preferably rectangular or hexagonal. From the viewpoint of suppressing unevenness of the space between the electrode and the separator, the interior angle of the polygon may be 120° or less. The quadrangular mesh may be rectangular or square, or may be rhombic.

[0050] From the viewpoint of ensuring the minimum necessary space between the electrode and the separator, the average height h of the convex portions may be 0.02 mm or more and 0.09 mm or less, or 0.015 mm or more and 0.01 mm or less, depending on the battery size. The average height h of the convex portions is determined by averaging the measured values ​​at any 10 points.

[0051] From the viewpoint of improving the liquid circulation of the non-aqueous electrolyte on the negative electrode surface, the height of some of the protrusions may be different from the height of the remaining protrusions, and the heights of adjacent protrusions may be different. The multiple protrusions may include a protrusion with a height h1 and a protrusion with a height h2 smaller than the height h1. In this case, the ratio of the height h2 to the height h1 (h2 / h1) may be, for example, 0.8 or more and less than 1.0, or 0.8 or more and 0.95 or less. The width of the protrusions (the width in the direction perpendicular to the extension direction of the line-shaped protrusions) is, for example, 1 mm or less, and may be 0.1 mm or more and 1 mm or less.

[0052] From the viewpoint of suppressing deposition of lithium metal on the surface of the projections, the projections may be made of a material having lower conductivity than the electrodes, or may be made of a resin material.

[0053] The material constituting the spacer layer is not particularly limited. The spacer layer may be composed of a conductive material and / or an insulating material. Among these, an insulating material is preferable. Since lithium metal is less likely to deposit on the surface of an insulating material, the effect of suppressing expansion of the negative electrode can be enhanced.

[0054] The conductive material can be appropriately selected from the materials for the negative electrode current collector or the positive electrode current collector described below. Such a spacer layer may be provided by forming convex portions on the negative electrode current collector by pressing or the like. Alternatively, a conductive paint may be applied to the surface of the separator or electrode, or a conductive tape may be attached to the surface of the separator or electrode.

[0055] Examples of insulating materials include resin materials. Examples of resin materials include polyolefin resin, acrylic resin, polyamide resin, polyimide resin, silicone resin, fluorine-based resin, urethane resin, melamine resin, and urea resin. As the resin material, a cured product of a curable resin such as an epoxy resin may be used. Furthermore, inorganic fillers may be mixed into these resin materials.

[0056] The material constituting the spacer layer is preferably a material having a Young's modulus of 0.01 GPa or more and 10 GPa or less. This makes it easier to alleviate stress due to expansion and contraction of the negative electrode and to maintain the space for accommodating lithium metal. In addition, damage to the electrode caused by the spacer layer is easily suppressed. Examples of insulating materials having a Young's modulus in the above range include cured products of the above-mentioned curable resins.

[0057] The spacer layer can be formed, for example, by attaching a resin adhesive tape to the surface of the separator or electrode. Alternatively, the spacer layer can be formed by applying a solution or dispersion containing a resin material to the surface of the separator or electrode and drying it. The spacer layer can also be formed by applying a curable resin to the surface of the separator or electrode in a desired shape and curing it. Alternatively, the spacer layer can be formed by scattering particles of a resin material in a desired shape on the surface of the separator or electrode.

[0058] Each component of the lithium secondary battery will be described in more detail below. [Negative Electrode] The negative electrode includes a negative electrode current collector. In a lithium secondary battery, lithium metal is deposited on the surface of the negative electrode current collector upon charging. More specifically, lithium ions contained in the non-aqueous electrolyte receive electrons on the negative electrode current collector upon charging to become lithium metal, which is then deposited on the surface of the negative electrode current collector. The lithium metal deposited on the surface of the negative electrode current collector dissolves as lithium ions in the non-aqueous electrolyte upon discharging. The lithium ions contained in the non-aqueous electrolyte may be derived from a lithium salt added to the non-aqueous electrolyte, may be supplied from the positive electrode active material upon charging, or may be both.

[0059] The negative electrode current collector may be a conductive sheet, such as a foil or film.

[0060] The surface of the conductive sheet may be smooth. This makes it easier for lithium metal from the positive electrode to deposit evenly on the conductive sheet during charging. "Smooth" means that the maximum height roughness Rz of the conductive sheet is 20 μm or less. The maximum height roughness Rz of the conductive sheet may be 10 μm or less. The maximum height roughness Rz is measured in accordance with JIS B 0601:2013.

[0061] The material of the negative electrode current collector (conductive sheet) may be any conductive material other than lithium metal and lithium alloys. The conductive material may be a metallic material such as a metal or alloy, or may be an annealed metallic material. The conductive material is preferably a material that does not react with lithium. More specifically, a material that does not form an alloy or an intermetallic compound with lithium is preferred. Examples of such conductive materials include copper (Cu), nickel (Ni), iron (Fe), and alloys containing these metal elements, as well as graphite with a preferentially exposed basal plane. Examples of alloys include copper alloys and stainless steel (SUS). Among these, copper and / or copper alloys with high conductivity are preferred.

[0062] The thickness of the negative electrode current collector is not particularly limited and is, for example, 5 μm or more and 300 μm or less.

[0063] The surface of the negative electrode current collector may have the aforementioned lithium layer formed thereon, or a negative electrode composite layer (not shown) may be formed thereon. The negative electrode composite layer is formed, for example, by applying a paste containing a negative electrode active material such as graphite to at least a portion of the surface of the negative electrode current collector. However, from the viewpoint of achieving a high-capacity lithium secondary battery exceeding that of a lithium ion battery, the thickness of the negative electrode composite layer is set to be sufficiently thin so that lithium metal can be precipitated at the negative electrode. In this case, the open-circuit potential of the negative electrode at full charge may be 70 mV or less relative to lithium metal (lithium dissolution and deposition potential). When the open-circuit potential of the negative electrode at full charge is 70 mV or less relative to lithium metal, lithium metal is present on the surface of the lithium ion absorption layer at full charge. In other words, the negative electrode exhibits capacity due to the precipitation and dissolution of lithium metal.

[0064] [Positive Electrode] The positive electrode includes, for example, a positive electrode current collector and a positive electrode composite layer supported on the positive electrode current collector. The positive electrode composite layer includes, for example, a positive electrode active material, a conductive material, and a binder. The positive electrode composite layer may be formed on only one side of the positive electrode current collector, or may be formed on both sides. The positive electrode is obtained, for example, by applying a positive electrode composite slurry including the positive electrode active material, the conductive material, and the binder to both sides of the positive electrode current collector, drying the coating, and then rolling.

[0065] The positive electrode active material is a material that absorbs and releases lithium ions. Examples of the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides. Among these, lithium-containing transition metal oxides are preferred because of their low production cost and high average discharge voltage.

[0066] Examples of transition metal elements contained in the lithium-containing transition metal oxide include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, and W. The lithium-containing transition metal oxide may contain one or more transition metal elements. The transition metal element may be Co, Ni, and / or Mn. The lithium-containing transition metal oxide may contain one or more typical elements as needed. Examples of typical elements include Mg, Al, Ca, Zn, Ga, Ge, Sn, Sb, Pb, and Bi. The typical element may be Al, etc.

[0067] Among lithium-containing transition metal oxides, lithium-containing composite oxides having a layered rock salt structure are preferred in terms of obtaining high capacity. The lithium-containing composite oxide preferably contains Co, Ni, and / or Mn as a transition metal element and Al as an optional component. In this case, in the lithium secondary battery, the molar ratio mLi / mM of the total amount of lithium contained in the positive electrode and negative electrode mLi to the amount mM of metal M other than lithium contained in the positive electrode is set to, for example, 1.1 or less.

[0068] The conductive material is, for example, a carbon material, such as carbon black, acetylene black, ketjen black, carbon nanotubes, and graphite.

[0069] Examples of the binder include fluororesin, polyacrylonitrile, polyimide resin, acrylic resin, polyolefin resin, rubber polymer, etc. Examples of the fluororesin include polytetrafluoroethylene, polyvinylidene fluoride, etc.

[0070] The positive electrode current collector may be a conductive sheet. Examples of the conductive sheet include foil and film. The surface of the positive electrode current collector may be coated with a carbon material.

[0071] Examples of the material of the positive electrode current collector (conductive sheet) include metal materials containing Al, Ti, Fe, etc. The metal material may be Al, an Al alloy, Ti, a Ti alloy, an Fe alloy, etc. The Fe alloy may be stainless steel (SUS).

[0072] The thickness of the positive electrode current collector is not particularly limited and is, for example, 5 μm or more and 300 μm or less.

[0073] [Separator] A porous sheet having ion permeability and insulating properties is used for the separator. Examples of porous sheets include thin films, woven fabrics, and nonwoven fabrics having micropores. The spacer layer described above may be formed on the surface of the separator. The material of the separator is not particularly limited, but may be a polymer material. Examples of polymer materials include olefin resins, polyamide resins, and cellulose. Examples of olefin resins include polyethylene, polypropylene, and copolymers of ethylene and propylene. The separator may contain additives as needed. Examples of additives include inorganic fillers.

[0074] [Non-aqueous electrolyte] The non-aqueous electrolyte having lithium ion conductivity contains, for example, a non-aqueous solvent and lithium ions and anions dissolved in the non-aqueous solvent. The non-aqueous electrolyte may be in a liquid state or a gel state.

[0075] The liquid non-aqueous electrolyte is prepared by dissolving a lithium salt in a non-aqueous solvent, which generates lithium ions and anions.

[0076] The gel-like non-aqueous electrolyte contains a lithium salt and a matrix polymer, or a lithium salt, a non-aqueous solvent, and a matrix polymer. The matrix polymer is, for example, a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesin, acrylic resin, and polyether resin.

[0077] As the lithium salt or anion, any known material used in non-aqueous electrolytes for lithium secondary batteries can be used. Specifically, BF ４ － , ClO ４ － , P.F. ６ － , C.F. ３ SO ３ － , C.F. ３ CO ２－ , anions of imides, anions of oxalate complexes, etc. Examples of the anions of imides include N(SO ２ CF ３ ) ２ － , N(C ｍ F ２ｍ＋１ SO ２ ) ｘ (C ｎ F ２ｎ＋１ SO ２ ) ｙ － (m and n are each independently an integer of 0 or 1 or more, and x and y are each independently 0, 1, or 2, satisfying the relationship x+y=2.) The anion of the oxalate complex may contain boron and / or phosphorus. Examples of the anion of the oxalate complex include bisoxalate borate anion, BF ２ (C ２ O ４ ) － , P.F. ４ (C ２ O ４ ) － , P.F. ２ (C ２ O ４ ) ２ － The non-aqueous electrolyte may contain one of these anions alone or two or more of them.

[0078] From the viewpoint of suppressing the deposition of lithium metal in a dendritic form, the nonaqueous electrolyte preferably contains at least an anion of an oxalate complex. The interaction between the anion of the oxalate complex and lithium facilitates the uniform deposition of lithium metal in the form of fine particles. This facilitates the suppression of localized deposition of lithium metal. The anion of the oxalate complex may be combined with another anion. The other anion may be PF ６ － and / or an anion of an imide.

[0079] Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and halogen-substituted derivatives thereof. The non-aqueous electrolyte may contain one or more of these non-aqueous solvents. Examples of halogen-substituted derivatives include fluorides.

[0080] Examples of esters include carbonate esters and carboxylic acid esters. Examples of cyclic carbonate esters include ethylene carbonate, propylene carbonate, and fluoroethylene carbonate (FEC). Examples of chain carbonate esters include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate. Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone. Examples of chain carboxylic acid esters include ethyl acetate, methyl propionate, and methyl fluoropropionate.

[0081] Examples of the ether include cyclic ethers and chain ethers. Examples of the cyclic ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of the chain ethers include 1,2-dimethoxyethane, diethyl ether, ethyl vinyl ether, methyl phenyl ether, benzyl ethyl ether, diphenyl ether, dibenzyl ether, 1,2-diethoxyethane, and diethylene glycol dimethyl ether.

[0082] The concentration of the lithium salt in the non-aqueous electrolyte is, for example, 0.5 mol / L or more and 3.5 mol / L or less. The concentration of the anion in the non-aqueous electrolyte may be 0.5 mol / L or more and 3.5 mol / L or less. Furthermore, the concentration of the anion of the oxalate complex in the non-aqueous electrolyte may be 0.05 mol / L or more and 1 mol / L or less.

[0083] The non-aqueous electrolyte may contain an additive. The additive may form a coating on the negative electrode. The formation of a coating derived from the additive on the negative electrode makes it easier to suppress the formation of dendrites. Examples of such additives include vinylene carbonate, FEC, and vinyl ethyl carbonate (VEC).

[0084] The configuration of a lithium secondary battery according to the present disclosure will be described below with reference to the drawings, taking as an example a cylindrical battery including a wound electrode group, although the present disclosure is not limited to the following configuration.

[0085] FIG. 1 is a longitudinal cross-sectional view of a lithium secondary battery 10. The lithium secondary battery 10 is a cylindrical battery including a cylindrical battery case, a wound electrode group 14 housed in the battery case, and a nonaqueous electrolyte (not shown). The battery case is composed of a case body 15, which is a cylindrical metal container with a bottom, and a sealing body 16 that seals the opening of the case body 15. The case body 15 has an annular step 21 formed by partially pressing the side wall near the opening from the outside. The sealing body 16 is supported by the surface of the step 21 facing the opening. A gasket 27 is disposed between the case body 15 and the sealing body 16, thereby ensuring the hermeticity of the battery case. Within the case body 15, insulating plates 17 and 18 are disposed at both ends of the electrode group 14 in the winding axis direction.

[0086] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26. The cap 26 is disposed outside the case body 15, and the filter 22 is disposed inside the case body 15. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, with an insulating member 24 interposed between their respective peripheral edges. The filter 22 and the lower valve body 23 are connected to each other at their respective peripheral edges. The upper valve body 25 and the cap 26 are connected to each other at their respective peripheral edges. The lower valve body 23 has an air vent. If the internal pressure of the battery case increases due to abnormal heat generation or the like, the upper valve body 25 bulges toward the cap 26 and separates from the lower valve body 23. This breaks the electrical connection between the lower valve body 23 and the upper valve body 25. If the internal pressure increases further, the upper valve body 25 breaks, and gas is discharged through an opening formed in the cap 26.

[0087] The electrode group 14 is composed of a positive electrode 110, a negative electrode (negative electrode current collector) 120, and a separator 300. The positive electrode 110, the negative electrode 120, and the separator 300 interposed therebetween are all strip-shaped, and are spirally wound so that their width directions are parallel to the winding axis.

[0088] The positive electrode 110 is electrically connected to a cap 26, which also serves as a positive electrode terminal, via a positive electrode lead 19. One end of the positive electrode lead 19 is connected, for example, near the center in the longitudinal direction of the positive electrode 110. The other end of the positive electrode lead 19 extending from the positive electrode 110 is welded to the inner surface of the filter 22 through a through-hole formed in the insulating plate 17.

[0089] The negative electrode 120 is electrically connected to the case body 15, which also serves as a negative electrode terminal, via the negative electrode lead 20. One end of the negative electrode lead 20 is connected to a position (e.g., near the center in the longitudinal direction) sufficiently distant from both the winding start end and the winding end end of the negative electrode 120, and the other end is welded to the inner bottom surface of the case body 15.

[0090] 2 is an enlarged view schematically illustrating the discharge state of region X surrounded by a dashed line in FIG. 1 . In the illustrated example, the cross-sectional shape of the spacer layer is trapezoidal. However, embodiments of the present disclosure are not limited to this. In the illustrated example, the spacer layer is provided between the positive electrode and the separator. However, embodiments of the present disclosure are not limited to this, and the spacer layer may be provided between the negative electrode and the separator, or between the positive electrode, negative electrode, and the separator.

[0091] The positive electrode 110 includes a positive electrode current collector 111 and a positive electrode composite layer 112. A spacer layer 400 is provided between the positive electrode composite layer 112 and the separator 300. The spacer layer 400 includes linear protrusions 401 arranged along the second direction D2 (longitudinal direction) of the separator 300. In a discharged state, lithium metal is not deposited on the surface of the negative electrode current collector 121, and a space is maintained between the positive electrode 110 and the separator 300. On the other hand, in a charged state, lithium metal is deposited on the surface of the negative electrode current collector 121 and is accommodated in the space between the positive electrode 110 and the separator 300 while being subjected to the pressing force of the separator 300. That is, the negative electrode 120 includes the negative electrode current collector 121 in a discharged state, and includes the negative electrode current collector 121 and lithium metal deposited on its surface in a charged state.

[0092] Because the lithium metal is accommodated in the space between the positive electrode 110 and the separator 300, the apparent volume change of the electrode assembly due to the precipitation of the lithium metal during charge / discharge cycles is reduced, thereby suppressing the stress applied to the negative electrode current collector 121. Furthermore, because pressure is applied from the separator 300 to the lithium metal accommodated between the positive electrode 110 and the separator 300, the precipitation state of the lithium metal is controlled, making it less likely for the lithium metal to become isolated, and suppressing a decrease in charge / discharge efficiency.

[0093] 3 is a top view showing the positive electrode 110 and negative electrode 120 used in the lithium secondary battery 10 of FIG. 1 in a state before winding. The positive electrode 110 has a positive electrode current collector exposed portion 111A (positive electrode lead fixing portion) where the positive electrode composite layer 112 is not disposed and the positive electrode current collector 111 is exposed. The positive electrode current collector exposed portion 111A is disposed toward the center of the positive electrode 110, sufficiently distant from both the winding start end E1 and the winding end end E2. A positive electrode lead 19 is attached within the positive electrode current collector exposed portion 111A. A portion of the positive electrode lead 19 protrudes from a first side E3 in the winding direction of the electrode group.

[0094] The negative electrode 120 has a negative electrode lead fixing portion. A negative electrode lead 20 is attached to the negative electrode lead fixing portion. In the example of FIG. 3 , the negative electrode lead fixing portion is a region of the negative electrode current collector 121 that is close to the center and sufficiently distant from both the winding start end E1′ and the winding end end E2′ of the winding, and includes a contact region with the negative electrode lead. A portion of the negative electrode lead 20 protrudes from a second side E4 in the winding direction of the electrode group.

[0095] The position of the positive electrode 110 facing the negative electrode lead 20 with the separator 300 interposed therebetween is indicated by a dashed line as a negative electrode lead facing portion 20X. The negative electrode lead facing portion 20X overlaps with the positive electrode current collector exposed portion 111A. The positive electrode lead 19 overlaps at least partially with the negative electrode lead facing portion 20X in the winding axis direction.

[0096] In FIG. 3 , the length of the negative electrode 120 in the longitudinal direction, i.e., the winding direction, is longer than that of the positive electrode 110. Therefore, for example, when the winding start end E1 and winding start end E1' are aligned, and the negative electrode 120 is wound on the outer periphery of the positive electrode 110 with the separator 300 interposed therebetween to form an electrode group, the outermost periphery of the negative electrode 120 is located outer than the outermost periphery of the positive electrode 110. The outermost periphery of the electrode group is the negative electrode 120 or the separator 300, and if the length of the separator 300 is shorter than the length of the negative electrode 120, an exposed portion of the negative electrode 120 will be generated at the outermost periphery of the electrode group. By bringing the exposed portion of the negative electrode 120 into contact with the case body 15, it is possible to reduce the resistance of the battery.

[0097] Fig. 4A is a top view showing another example of the positive electrode 110 and negative electrode 120 used in the lithium secondary battery 10 of Fig. 1 in a state before being wound. In the example of Fig. 4, the negative electrode 120 has a lithium layer 124 disposed on a negative electrode current collector 121. The negative electrode 120 has a negative electrode current collector exposed portion 121A (negative electrode lead fixing portion) where the lithium layer 124 is not disposed and the negative electrode current collector 121 is exposed. A negative electrode lead 20 is attached within the negative electrode current collector exposed portion 121A. A portion of the negative electrode lead 20 protrudes from the second side E4 in the winding direction of the electrode group.

[0098] In the positive electrode 110, the position of the negative electrode lead facing portion 20X that faces the negative electrode lead 20 across the separator 300 overlaps with the positive electrode current collector exposed portion 111A. In the positive electrode 110, the region that faces the negative electrode lead fixing portion 121A across the separator 300 is within the positive electrode current collector exposed portion 111A. At least a portion of the positive electrode lead 19 overlaps with the negative electrode lead facing portion 20X in the winding axis direction.

[0099] FIG. 4B is a top view showing another example of the positive electrode 110 and negative electrode 120 used in the lithium secondary battery 10 of FIG. 1 in a state before winding. In the example of FIG. 4B , the negative electrode 120 has a lithium layer 124 disposed on a negative electrode current collector 121, similar to FIG. 4A . The negative electrode lead 20 is attached to the lithium layer 124. In the example of FIG. 4B , the negative electrode lead fixing portion is a region of the lithium layer 124 near the center, sufficiently distant from both the winding start end E1′ and the winding end end E2′ of the winding, and includes a contact area with the negative electrode lead. A portion of the negative electrode lead 20 protrudes from the second side E4 in the winding direction of the electrode group. In the positive electrode 110, the negative electrode lead facing portion 20X overlaps with the positive electrode current collector exposed portion 111A. At least a portion of the positive electrode lead 19 overlaps with the negative electrode lead facing portion 20X in the winding axis direction.

[0100] FIG. 5 is a top view showing another example of the positive electrode 110 and negative electrode 120 used in the lithium secondary battery 10 of FIG. 1 in a state before winding. In the example of FIG. 5, the positive electrode 110 has two positive electrode current collector exposed portions 111A and 111B spaced apart and positioned toward the center, sufficiently distant from both the winding start end E1 and the winding end end E2 of the positive electrode 110. The positive electrode current collector exposed portion 111A is a positive electrode lead fixing portion, to which a positive electrode lead 19 is attached. In the positive electrode 110, the negative electrode lead opposing portion 20X, which faces the negative electrode lead 20 across the separator 300, overlaps with the positive electrode current collector exposed portion 111A. At least a portion of the positive electrode lead 19 overlaps with the negative electrode lead opposing portion 20X in the winding axis direction.

[0101] 5, the positive electrode current collector exposed portion 111B does not constitute a positive electrode lead fixing portion, but may face the negative electrode lead 20 via the separator 300. In the positive electrode 110, the position of the negative electrode lead facing portion 20X that faces the negative electrode lead 20 via the separator 300 may overlap with the positive electrode current collector exposed portion 111B.

[0102] FIG. 6 is a top view showing another example of the positive electrode 110 and negative electrode 120 used in the lithium secondary battery 10 of FIG. 1 in a state before winding. In the example of FIG. 6, the positive electrode 110 has a positive electrode current collector exposed portion 111A located toward the center, sufficiently away from both the winding start end E1 and the winding end end E2 of the positive electrode 110. The positive electrode current collector exposed portion 111A is a positive electrode lead fixing portion, to which a positive electrode lead 19 is attached. In the positive electrode 110, the region facing the negative electrode lead fixing portion 121A across the separator 300 is within the positive electrode current collector exposed portion 111A. However, the positive electrode lead 19 does not overlap with the negative electrode lead facing portion 20X in the winding axis direction.

[0103] In the illustrated example, a cylindrical lithium secondary battery having a wound electrode group has been described, but the shape of the lithium secondary battery is not limited to this and can be appropriately selected from various shapes such as a cylindrical shape, a coin shape, a square shape, a sheet shape, a flat shape, etc., depending on the application, etc. The shape of the electrode group is also not particularly limited and may be a laminated type. In addition, known configurations other than the electrode group and non-aqueous electrolyte of the lithium secondary battery can be used without particular limitation.

[0104] <<Supplementary Note>> The above description of the embodiment discloses the following techniques. (Technology 1) An electrode assembly including a strip-shaped positive electrode and a strip-shaped negative electrode wound with a separator interposed therebetween; and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further includes one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly, and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, wherein the negative electrode has at least a negative electrode current collector, and is an electrode in which lithium metal is deposited on the negative electrode current collector during charge and the lithium metal dissolves in the non-aqueous electrolyte during discharge, wherein the positive electrode has one or more positive electrode current collector exposed portions where the positive electrode current collector is exposed, and the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixed portions to which the positive electrode leads are fixed, A lithium secondary battery, wherein the negative electrode includes one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, and the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions with the separator interposed therebetween in a radial direction perpendicular to the winding axis. (Technology 2) The lithium secondary battery according to Technology 1, wherein the negative electrode lead is fixed to the negative electrode current collector. (Technology 3) The lithium secondary battery according to Technology 1 or 2, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy arranged on the negative electrode current collector, the negative electrode has one or more negative electrode current collector exposed portions to which the negative electrode current collector is exposed, and at least one of the one or more negative electrode current collector exposed portions is the negative electrode lead fixing portion. (Technology 4) The lithium secondary battery according to Technology 1, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy arranged on the negative electrode current collector, the lithium layer includes the one or more negative electrode lead fixing portions, and the negative electrode lead is fixed to the lithium layer.(Technology 5) An electrode assembly including a strip-shaped positive electrode and a strip-shaped negative electrode wound with a separator interposed therebetween; and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further includes: one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly; and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy disposed on the negative electrode current collector, the positive electrode has one or more positive electrode current collector exposed portions at which the positive electrode current collector is exposed, the one or more positive electrode current collector exposed portions including one or more positive electrode lead fixed portions at which the positive electrode lead is fixed, and the negative electrode has one or more negative electrode current collector exposed portions at which the negative electrode current collector is exposed, the one or more negative electrode current collector exposed portions include one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, and the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions across the separator in a radial direction perpendicular to the winding axis. (Technology 6) An electrode assembly including a strip-shaped positive electrode and a strip-shaped negative electrode wound with a separator interposed therebetween; and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further includes: one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly; and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy disposed on the negative electrode current collector, the positive electrode has one or more positive electrode current collector exposed portions at which the positive electrode current collector is exposed, the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which the positive electrode lead is fixed, and the lithium layer includes one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions with the separator interposed therebetween in a radial direction perpendicular to the winding axis, and the negative electrode lead is fixed to the lithium layer.(Technology 7) The lithium secondary battery according to any one of Technologies 3 to 6, wherein the negative electrode is an electrode in which lithium metal precipitates on the negative electrode current collector or the lithium layer during charging and dissolves in the non-aqueous electrolyte during discharging. (Technology 8) The lithium secondary battery according to any one of Technologies 1 to 7, wherein the positive electrode lead is fixed to the positive electrode lead fixing part so as to at least partially overlap, in the direction of the winding axis, with a negative electrode lead opposing part that faces the negative electrode lead across the separator. (Technology 9) The lithium secondary battery according to any one of Technologies 1 to 8, wherein the lithium secondary battery has two or more positive electrode current collector exposed parts that are arranged at a distance from each other in the longitudinal direction of the positive electrode, and at least one of the two or more positive electrode current collector exposed parts is the positive electrode lead fixing part. (Technology 10) The lithium secondary battery according to any one of Technologies 1 to 9, wherein the positive electrode lead and the negative electrode lead are arranged so as not to overlap each other in a radial direction perpendicular to the direction of the winding axis. (Technology 11) The lithium secondary battery according to any one of Technologies 1 to 10, further comprising a bottomed cylindrical outer can accommodating the electrode group and the non-aqueous electrolyte, wherein the negative electrode is exposed at the outermost periphery of the electrode group, and the exposed portion of the negative electrode at the outermost periphery of the electrode group is in contact with the inner circumferential surface of the outer can. (Technology 12) The lithium secondary battery according to any one of Technologies 1 to 11, further comprising a spacer layer having convex portions arranged in a predetermined repeating pattern between the separator and at least one of the positive electrode and the negative electrode. (Technology 13) The lithium secondary battery according to any one of Technologies 1 to 12, wherein the positive electrode mixture layer contains a lithium-containing composite oxide as a positive electrode active material, and the lithium-containing composite oxide has a layered rock salt structure. (Technology 14) The lithium secondary battery according to any one of Technologies 1 to 13, wherein the negative electrode current collector contains stainless steel.

[0105] [Examples] The lithium secondary battery according to the present disclosure will be specifically described below based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0106] Example 1 (1) Preparation of Positive Electrode A rock salt type lithium-containing transition metal oxide (NCA; positive electrode active material) containing Li, Ni, Co, and Al (the molar ratio of Li to the total of Ni, Co, and Al is 1.0) and having a layered structure, acetylene black (AB; conductive material), and polyvinylidene fluoride (PVdF; binder) were mixed in a mass ratio of NCA:AB:PVdF = 95:2.5:2.5, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added and stirred to prepare a positive electrode mixture slurry. Next, the obtained positive electrode mixture slurry was applied to both sides of an Al foil (positive electrode current collector), dried, and the coating of the positive electrode mixture was rolled using a roller. Finally, the resulting laminate of the positive electrode current collector and the positive electrode composite was cut to a predetermined electrode size to produce a positive electrode having a positive electrode composite layer on both sides of the positive electrode current collector. The longitudinal length of the positive electrode was L. A current collector exposed portion (positive electrode lead fixing portion) where no positive electrode composite layer was located was provided at a position L / 3 from one longitudinal end (the winding start end) of the positive electrode.

[0107] (2) Preparation of Separator (Preparation of Substrate) A strip-shaped porous film made of polyethylene (average thickness 10 μm) was prepared as a separator substrate.

[0108] (Formation of First Spacer Layer) A coating liquid containing polyvinylidene fluoride and alumina particles (inorganic filler) was dispensed onto one surface (negative electrode side surface) of the separator using a dispenser. The coating liquid was then vacuum dried. In this manner, a spacer layer (first spacer layer) having a honeycomb-shaped mesh pattern was formed on one surface of the separator.

[0109] The mesh shape of the first spacer layer was a regular hexagon. The height of the linear convex portions constituting the first spacer layer was set to 30 μm (thickness of the first spacer layer: 30 μm). The spacing between two opposing sides of the regular hexagonal mesh was approximately 4.5 mm. The width of the linear convex portions was 0.25 mm. In the opposing region of the separator between the positive electrode and the negative electrode, the area S1 of the first spacer layer was 10% of the area S0 of the opposing region.

[0110] (Formation of second spacer layer) A coating liquid containing polyvinylidene fluoride and alumina particles (inorganic filler) was dispensed onto both sides of the positive electrode using a dispenser. The coating liquid was then vacuum dried. In this way, spacer layers (second spacer layers) having a honeycomb mesh pattern were formed on both sides of the positive electrode.

[0111] The mesh shape of the second spacer layer was a regular hexagon. The height of the linear convex portions constituting the second spacer layer was set to 10 μm (thickness of the second spacer layer: 10 μm). The spacing between two opposing sides of the regular hexagonal mesh was approximately 4.5 mm. The width of the linear convex portions was 0.25 mm. The area S2 of the second spacer layer was 10% of the area S0 of the region of the positive electrode facing the negative electrode.

[0112] (3) Fabrication of Negative Electrode (Preparation of Negative Electrode Current Collector) A strip of copper foil (thickness 10 μm) was used as the negative electrode current collector. (Welding of Negative Electrode Tab) A copper negative electrode tab (width 3 mm, thickness 100 μm) was welded to the negative electrode current collector using an ultrasonic welding machine. When the electrode group was fabricated, the negative electrode tab was attached to a position facing the exposed portion of the positive electrode current collector (positive electrode lead fixing portion) via the separator.

[0113] (4) Preparation of non-aqueous electrolyte: Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of EC:DMC=30:70, and LiPF was added to the resulting mixed solvent. ６ 1 mol / L, LiBF ２ (C ２ O ４ ) were dissolved in a concentration of 0.1 mol / L to prepare liquid non-aqueous electrolytes.

[0114] (5) Assembly of Battery An electrode assembly was produced by spirally winding the positive electrode and negative electrode current collector with the separator interposed therebetween in a dry atmosphere with a dew point of −30° C. or less. The electrode assembly was produced in such a way that the negative electrode was exposed at the winding end (outermost periphery) of the electrode assembly.

[0115] The electrode group was inserted into a cylindrical battery can (case body) with a bottom, a nonaqueous electrolyte was poured into it, and the opening of the battery can was sealed with a sealing member. At this time, the positive electrode lead was connected to the sealing member, and the negative electrode lead was connected to the battery can. A gasket was placed between the sealing member and the battery can. In this way, a cylindrical lithium secondary battery was completed, and lithium secondary battery A1 according to Example 1 was obtained.

[0116] Examples 2 to 5, Comparative Examples 1 to 8 Lithium secondary batteries A2 to A5 according to Examples 2 to 5 and lithium secondary batteries B1 to B8 according to Comparative Examples 1 to 8 were obtained in the same manner as battery A1 of Example 1, except that the material of the negative electrode and the negative electrode lead fixing portion on the negative electrode, and / or the attachment position of the negative electrode lead were changed to the materials shown in Table 1.

[0117] In Example 2, a stainless steel (SUS316L) foil (thickness: 10 μm) was used as the negative electrode (negative electrode current collector), and a negative electrode lead was attached to the stainless steel foil. As in Example 1, the negative electrode tab was attached to a position facing the exposed portion of the positive electrode current collector via the separator when the electrode group was produced.

[0118] In Example 3, the negative electrode used was a negative electrode current collector made of stainless steel (SUS316L) foil (10 μm thick) with Li layers (20 μm thick) formed on both sides. However, the Li layer at the negative electrode lead fixing portion was scraped off to expose the negative electrode current collector, and the negative electrode lead was attached to the stainless steel foil. As in Example 1, the negative electrode tab was attached to a position facing the exposed portion of the positive electrode current collector via the separator when the electrode group was produced.

[0119] In Example 4, the same negative electrode as in Example 3 was used. However, the negative electrode current collector was not exposed at the negative electrode lead fixing portion, and the negative electrode lead was attached onto the Li layer. As in Example 1, when the electrode group was produced, the negative electrode tab was attached in a position facing the exposed portion of the positive electrode current collector via the separator.

[0120] In Example 5, the negative electrode used was a negative electrode current collector made of stainless steel (SUS316L) foil (thickness 10 μm) with Li alloy layers (alloy containing Li and Mg in a mass ratio of 99:1, thickness 20 μm) formed on both sides. The negative electrode current collector was not exposed at the negative electrode lead fixing portion, and the negative electrode lead was attached onto the Li alloy layer. As in Example 1, when the electrode group was produced, the negative electrode tab was attached in a position facing the exposed portion of the positive electrode current collector via the separator.

[0121] In Comparative Example 1, the materials of the negative electrode and the negative electrode lead fixing part were the same as those of Example 1, and the negative electrode lead was attached at a position that did not face the exposed portion of the positive electrode current collector and was 20 mm inward from one end of the negative electrode in the longitudinal direction (the winding start end).

[0122] In Comparative Example 2, the materials of the negative electrode and the negative electrode lead fixing part were the same as those of Example 2, and the negative electrode lead was attached at a position that did not face the exposed portion of the positive electrode current collector and was 20 mm inward from one end of the negative electrode in the longitudinal direction (the winding start end).

[0123] In Comparative Example 3, the materials of the negative electrode and the negative electrode lead fixing part were the same as those in Example 2, and the negative electrode lead was attached at a position that did not face the exposed portion of the positive electrode current collector and was 20 mm on the outer circumferential side from the other end of the negative electrode in the longitudinal direction (the end where the winding ended).

[0124] In Comparative Example 4, the materials of the negative electrode and the negative electrode lead fixing part were the same as those in Example 3, and the negative electrode lead was attached at a position that did not face the exposed portion of the positive electrode current collector and was 20 mm inward from one end of the negative electrode in the longitudinal direction (the winding start end).

[0125] In Comparative Example 5, the materials of the negative electrode and the negative electrode lead fixing part were the same as those of Example 4, and the negative electrode lead was attached at a position that did not face the exposed portion of the positive electrode current collector and was 20 mm inward from one end of the negative electrode in the longitudinal direction (the winding start end).

[0126] In Comparative Example 6, the materials of the negative electrode and the negative electrode lead fixing part were the same as those of Example 4, and the negative electrode lead was attached at a position that did not face the exposed portion of the positive electrode current collector and was 20 mm on the outer circumferential side from the other end of the negative electrode in the longitudinal direction (the end where the winding ended).

[0127] In Comparative Example 7, the materials of the negative electrode and the negative electrode lead fixing part were the same as those of Example 5, and the negative electrode lead was attached at a position that did not face the exposed part of the positive electrode current collector and was 20 mm inward from one end of the negative electrode in the longitudinal direction (the winding start end).

[0128] In Comparative Example 8, the materials of the negative electrode and the negative electrode lead fixing part were the same as those of Example 5, and the negative electrode lead was attached at a position that did not face the exposed portion of the positive electrode current collector and was 20 mm on the outer circumferential side from the other end of the negative electrode in the longitudinal direction (the end where the winding ended).

[0129] [Evaluation 1] (Initial Resistance) After manufacture, each battery was subjected to constant current charging at a current of 0.1 C in an environment of 25° C. until the voltage reached 4.2 V, and then constant voltage charging at a voltage of 4.2 V until the current value reached 0.02 C. Thereafter, the battery was discharged at a current value of 0.5 C for 30 seconds, and the internal resistance of the battery was calculated from the voltage drop ΔV between the terminals during discharge relative to the voltage during charging (4.2 V), and this was taken as the initial resistance.

[0130] [Evaluation 2] (Rate of Resistance Increase) After evaluating the initial resistance, each battery was subjected to a charge-discharge cycle test. Charge and discharge were performed under the following conditions, with a 20-minute break between charge and discharge.

[0131] (Charging) In an environment of 25° C., constant current charging was performed at a current of 0.1 C until the voltage reached 4.2 V, and then constant voltage charging was performed at a voltage of 4.2 V until the current value reached 0.02 C. (Discharging) Constant voltage discharging was performed at a current value of 0.2 C until the voltage reached 3.0 V.

[0132] After carrying out this charge / discharge cycle 50 times, the internal resistance of the battery was measured using the same method as for the initial resistance evaluation, and the resistance R ５０ Resistance R of the first cycle １ The ratio (%) of the resistance increase rate to the resistance increase rate X was determined as (R ５０ / R １ ) x 100

[0133] The evaluation results are shown in Table 1. Table 1 also shows the materials of the negative electrode and the negative electrode lead fixing part of the negative electrode used in each battery, and the attachment position of the negative electrode lead. In Table 1, the initial resistance is shown as a relative value, with the initial resistance of battery B2 set to 100. Regarding the negative electrode lead position in Table 1, "facing" means that the negative electrode lead is located opposite the exposed portion of the positive electrode current collector with the separator interposed therebetween, and "not facing" means that the negative electrode lead is located not opposite the exposed portion of the positive electrode current collector with the separator interposed therebetween.

[0134]

[0135] Comparing batteries B1 to B8, when the negative electrode lead was attached via a separator in a position not facing the exposed portion of the positive electrode current collector (positive electrode lead fixing portion), batteries B2, B5, and B7, which had the negative electrode lead attached to the inner periphery, tended to have lower initial resistance but a higher rate of resistance rise compared to the same type of batteries B3, B6, and B8, which had the negative electrode lead attached to the outer periphery. This is thought to be because the negative electrode (negative electrode current collector) is exposed at the outermost periphery of the electrode assembly and in contact with the case, allowing electrical contact at two points: the current collection path via the outermost negative electrode and the current collection path via the inner negative electrode tab, resulting in lower initial resistance. Meanwhile, with regard to the rate of resistance rise, the location of the negative electrode lead on the inner periphery fixes the position of the inner electrode, so when the negative electrode expands and contracts repeatedly due to charge / discharge cycles, stress concentrates on the fixing portion on the inner periphery. This is thought to have caused the electrode to break or buckle the electrode assembly, resulting in poor electrical contact from the inner periphery and promoting the increase in resistance.

[0136] In contrast, in the batteries A1 to A5 in which the negative electrode lead was attached to a position facing the exposed portion of the positive electrode current collector (positive electrode lead fixing portion) via a separator, the initial resistance was low and the increase in resistance after charge-discharge cycles was also suppressed.

[0137] The lithium secondary battery of the present disclosure can be used in electronic devices such as mobile phones, smartphones, and tablet terminals, electric vehicles including hybrids and plug-in hybrids, and home storage batteries combined with solar cells.

[0138] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0139] REFERENCE SIGNS LIST 10 Lithium secondary battery 14 Electrode group 15 Case body 16 Sealing body 17, 18 Insulating plate 19 Positive electrode lead 20 Negative electrode lead 20X Negative electrode lead facing portion 21 Step portion 22 Filter 23 Lower valve body 24 Insulating member 25 Upper valve body 26 Cap 27 Gasket 100 Electrode 110 Positive electrode 111 Positive electrode current collector 111A, 111B Positive electrode current collector exposed portion (positive electrode lead fixing portion) 112 Positive electrode composite layer 120 Negative electrode 121 Negative electrode current collector 121A Negative electrode lead fixing portion 124 Lithium layer 300 Separator 400 Spacer layer 401 Convex portion

Claims

1. An electrode assembly comprising a strip-shaped positive electrode and a strip-shaped negative electrode wound with a separator interposed therebetween; and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further comprising: one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly; and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, wherein the negative electrode has at least a negative electrode current collector, and is an electrode in which lithium metal is deposited on the negative electrode current collector during charging and the lithium metal dissolves in the non-aqueous electrolyte during discharging, and the positive electrode has one or more positive electrode current collector exposed portions where the positive electrode current collector is exposed, and the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which the positive electrode leads are fixed, the negative electrode includes one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, and the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions across the separator in a radial direction perpendicular to the winding axis.

2. The lithium secondary battery according to claim 1, wherein the negative electrode lead is fixed to the negative electrode current collector.

3. The lithium secondary battery according to claim 1, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy disposed on the negative electrode current collector, the negative electrode has one or more negative electrode current collector exposed portions where the negative electrode current collector is exposed, and at least one of the one or more negative electrode current collector exposed portions is the negative electrode lead fixing portion.

4. The lithium secondary battery according to claim 1, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy disposed on the negative electrode current collector, the lithium layer includes the one or more negative electrode lead fixing portions, and the negative electrode lead is fixed to the lithium layer.

5. An electrode assembly comprising a strip-shaped positive electrode and a strip-shaped negative electrode wound with a separator interposed therebetween, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further comprising: one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly; and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy disposed on the negative electrode current collector, the positive electrode has one or more positive electrode current collector exposed portions at which the positive electrode current collector is exposed, the one or more positive electrode current collector exposed portions including one or more positive electrode lead fixed portions at which the positive electrode lead is fixed, and the negative electrode has one or more negative electrode current collector exposed portions at which the negative electrode current collector is exposed, the one or more negative electrode current collector exposed portions include one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, and the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions across the separator in a radial direction perpendicular to the winding axis.

6. An electrode assembly comprising a strip-shaped positive electrode and a strip-shaped negative electrode wound with a separator interposed therebetween, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, and further comprises: one or more positive electrode leads fixed to the positive electrode current collector and including a protrusion protruding from a first side in the winding axis direction of the electrode assembly; and one or more negative electrode leads fixed to the negative electrode and including a protrusion protruding from a second side in the winding axis direction of the electrode assembly, wherein the negative electrode has a lithium layer containing lithium metal or a lithium alloy disposed on the negative electrode current collector, the positive electrode has one or more positive electrode current collector exposed portions to which the positive electrode current collector is exposed, the one or more positive electrode current collector exposed portions include one or more positive electrode lead fixing portions to which the positive electrode lead is fixed, and the lithium layer includes one or more negative electrode lead fixing portions to which the negative electrode lead is fixed, the negative electrode lead fixing portion faces one of the one or more positive electrode current collector exposed portions with the separator interposed therebetween in a radial direction perpendicular to the winding axis, and the negative electrode lead is fixed to the lithium layer.

7. The lithium secondary battery according to claim 5 or 6, wherein the negative electrode is an electrode in which lithium metal is deposited on the negative electrode current collector or the lithium layer during charging, and the lithium metal dissolves in the non-aqueous electrolyte during discharging.

8. The lithium secondary battery according to any one of claims 1 to 6, wherein the positive electrode lead is fixed at the positive electrode lead fixing portion so as to overlap at least a portion of the positive electrode lead fixing portion with a negative electrode lead opposing portion that faces the negative electrode lead with the separator interposed therebetween in the winding axis direction.

9. The lithium secondary battery according to any one of claims 1 to 6, which has two or more positive electrode current collector exposed portions arranged at a distance in the longitudinal direction of the positive electrode, and at least one of the two or more positive electrode current collector exposed portions is the positive electrode lead fixing portion.

10. The lithium secondary battery according to any one of claims 1 to 6, wherein the positive electrode lead and the negative electrode lead are arranged so as not to overlap each other in a radial direction perpendicular to the direction of the winding axis.

11. The lithium secondary battery according to any one of claims 1 to 6, further comprising a cylindrical outer can with a bottom that houses the electrode group and the non-aqueous electrolyte, wherein the negative electrode is exposed at the outermost periphery of the electrode group, and the exposed portion of the negative electrode at the outermost periphery of the electrode group is in contact with the inner circumferential surface of the outer can.

12. The lithium secondary battery according to any one of claims 1 to 6, further comprising a spacer layer having protrusions arranged in a predetermined repeating pattern between the separator and at least one of the positive electrode and the negative electrode.

13. The lithium secondary battery according to any one of claims 1 to 6, wherein the positive electrode mixture layer contains a lithium-containing composite oxide as a positive electrode active material, and the lithium-containing composite oxide has a layered rock salt structure.

14. The lithium secondary battery according to any one of claims 1 to 6, wherein the negative electrode current collector comprises stainless steel.

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