Non-aqueous electrolyte secondary battery

Abstract

A non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure comprises: an electrode group in which a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator disposed between the strip-shaped positive electrode and the strip-shaped negative electrode are wound in the length direction; and a non-aqueous electrolyte. The strip-shaped positive electrode has a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the strip-shaped positive electrode current collector. The strip-shaped negative electrode has a strip-shaped negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the strip-shaped negative electrode current collector. An exposed portion of the positive electrode current collector in which the positive electrode mixture layer is not arranged is provided on at least one end side of the strip-shaped positive electrode current collector in the width direction, and a positive electrode tab is connected to the exposed portion of the positive electrode current collector. A tensile strength A (N / m) of the strip-shaped positive electrode current collector and a tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies a specific relationship.

Description

Nonaqueous electrolyte secondary battery

[0001] This invention relates to a non-aqueous electrolyte secondary battery.

[0002] Non-aqueous electrolyte secondary batteries, such as lithium-ion secondary batteries, are used in a variety of applications due to their characteristics, including high capacity. A non-aqueous electrolyte secondary battery comprises a positive electrode, a negative electrode, a separator placed between the positive and negative electrodes, and a non-aqueous electrolyte (e.g., electrolyte solution). Among non-aqueous electrolyte secondary batteries, there is a known type that comprises an electrode group in which a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator placed between the strip-shaped positive and negative electrodes are wound in the longitudinal direction. Such an electrode group is also called a wound electrode group.

[0003] In a non-aqueous electrolyte secondary battery, a strip-shaped positive electrode may be used, comprising a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the strip-shaped positive electrode current collector, and a strip-shaped negative electrode may be used, comprising a strip-shaped negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the strip-shaped negative electrode current collector. The positive electrode mixture layer contains a positive electrode active material, and the negative electrode mixture layer contains a negative electrode active material. Both the positive electrode active material and the negative electrode active material intercept and release lithium ions during charging and discharging of the non-aqueous electrolyte secondary battery. As a result of this intercept and release of lithium ions, the positive electrode active material and the negative electrode active material expand and contract. During charging and discharging of a non-aqueous electrolyte secondary battery, the negative electrode active material often expands and contracts more than the positive electrode active material. In this case, the negative electrode mixture layer also expands and contracts more than the positive electrode mixture layer. As a result, greater tensile stress is generated in the negative electrode current collector than in the positive electrode current collector.

[0004] In a non-aqueous electrolyte secondary battery equipped with a wound electrode group, as described above, if the negative electrode current collector experiences greater tensile stress than the positive electrode current collector, the expansion of the positive electrode current collector may not be able to keep up with the expansion of the negative electrode current collector, causing only the negative electrode current collector to expand. As a result, variations may occur in the distance between the strip-shaped positive electrode and the strip-shaped negative electrode. In this case, parts of the wound electrode group become more easily charged and parts become less easily charged (i.e., charge / discharge unevenness occurs), and the battery capacity of the non-aqueous electrolyte secondary battery decreases with each repeated charge / discharge cycle. In other words, the cycle maintenance rate decreases. Furthermore, if metallic lithium is locally deposited in the easily charged part of the strip-shaped negative electrode of the wound electrode group, there is a concern that as the internal temperature of the non-aqueous electrolyte secondary battery rises, the metallic lithium will react with the non-aqueous electrolyte, reducing the thermal stability of the non-aqueous electrolyte secondary battery. For this reason, various proposals have been made to suppress the decrease in cycle maintenance rate and thermal stability of non-aqueous electrolyte secondary batteries equipped with a wound electrode group.

[0005] Patent Document 1 discloses a non-aqueous electrolyte secondary battery comprising a wound electrode group including a long positive electrode, a long negative electrode, and a separator disposed between the positive electrode and the negative electrode, a non-aqueous electrolyte, and a rectangular battery case housing these, wherein the cross-section of the electrode group has a major axis and a minor axis, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, and the tensile strength of the positive electrode is 15 N / cm or less when the elongation rate of the positive electrode in the longitudinal direction is 1%.

[0006] International Publication No. 2009 / 122717

[0007] Incidentally, in a strip-shaped positive electrode of a wound electrode group, an exposed portion of the strip-shaped positive electrode current collector is provided on at least one end side in the width direction of the strip-shaped positive electrode current collector, and when a positive electrode tab is connected to the exposed portion of the positive electrode current collector, the movement of the exposed portion of the positive electrode current collector in the radial direction is restricted at the connection portion with the positive electrode tab. Therefore, when the negative electrode mixture layer expands and presses the strip-shaped positive electrode in the radial direction during charging of the wound electrode group, the pressing may cause breakage of the exposed portion of the positive electrode current collector. That is, "foil breakage" may occur in the strip-shaped positive electrode. Then, breakage of the exposed portion of the positive electrode current collector may cause the positive electrode tab to be isolated, resulting in a significant decrease in current collection performance. However, in any known documents including Patent Document 1, it is difficult to say that sufficient studies have been conducted to suppress breakage of the exposed portion of the positive electrode current collector.

[0008] Further, in Patent Document 1, although a proposal has been made for a non-aqueous electrolyte secondary battery including a wound electrode group to suppress a decrease in cycle retention rate and a decrease in thermal stability, there is still room for further study on suppression of a decrease in cycle retention rate and improvement of safety of the non-aqueous electrolyte secondary battery (including suppression of a decrease in thermal stability). Particularly in recent years, in response to the demand for higher capacity, in a wound electrode group in which the thickness of the positive electrode mixture layer and the negative electrode mixture layer is increased and the thickness of the positive electrode current collector and the negative electrode current collector is reduced, breakage of the exposed portion of the positive electrode current collector, a decrease in cycle retention rate, and a decrease in safety are likely to occur. In this case, there is still room for more sufficient study on suppression of breakage of the exposed portion of the positive electrode current collector, suppression of a decrease in cycle retention rate, and improvement of safety.

[0009] Accordingly, an object of the present disclosure is to provide a non-aqueous electrolyte secondary battery that can suppress breakage of an exposed portion of a positive electrode current collector, can suppress a decrease in cycle retention rate, and can improve safety.

[0010] One aspect of the present invention relates to a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery includes an electrode group in which a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator disposed between the strip-shaped positive electrode and the strip-shaped negative electrode are wound in a length direction, and a non-aqueous electrolyte. In the non-aqueous electrolyte secondary battery, the strip-shaped positive electrode includes a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the strip-shaped positive electrode current collector, and the strip-shaped negative electrode includes a strip-shaped negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the strip-shaped negative electrode current collector. In the non-aqueous electrolyte secondary battery, at least one end side in the width direction of the strip-shaped positive electrode current collector is provided with an exposed portion of the positive electrode current collector where the positive electrode mixture layer is not disposed, and a positive electrode tab is connected to the exposed portion of the positive electrode current collector. In the non-aqueous electrolyte secondary battery, the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m, and the ratio (A / C) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies 1.00 ≤ A / C ≤ 1.86.

[0011] According to the present disclosure, it is possible to provide a non-aqueous electrolyte secondary battery capable of suppressing breakage of the exposed portion of the positive electrode current collector, suppressing a decrease in cycle retention rate, and improving safety.

[0012] It is a cross-sectional view schematically showing a non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to 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 materials may be applied as long as the effects of the present disclosure can be obtained. Known constituent elements may be applied to the constituent elements characteristic of the present disclosure. In this specification, when the term "range from numerical value A to numerical value B" is used, the range includes both numerical value A and numerical value B.

[0014] In the following explanation, when examples are given for the lower and upper limits of numerical values ​​related to specific physical properties or conditions, any combination of either of the given lower limits and any of the given upper limits is permitted, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, unless otherwise specified, one type may be selected and used alone, or two or more types may be used in combination.

[0015] This disclosure includes any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims. In other words, any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims is possible, as long as it does not result in a technical inconsistency.

[0016] [Non-aqueous electrolyte secondary battery] A non-aqueous electrolyte secondary battery according to the embodiment of this disclosure comprises an electrode group in which a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator disposed between the strip-shaped positive electrode and the strip-shaped negative electrode are wound in the longitudinal direction, and a non-aqueous electrolyte. Hereinafter, the electrode group in which a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator disposed between the strip-shaped positive electrode and the strip-shaped negative electrode are wound in the longitudinal direction will also be simply referred to as a wound electrode group.

[0017] In the non-aqueous electrolyte secondary battery according to the embodiment of the present disclosure, the strip-shaped positive electrode has a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the strip-shaped positive electrode current collector, and the strip-shaped negative electrode has a strip-shaped negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the strip-shaped negative electrode current collector. In the non-aqueous electrolyte secondary battery according to the embodiment of the present disclosure, at least one end of the strip-shaped positive electrode current collector in the width direction is provided with an exposed portion of the positive electrode current collector where the positive electrode mixture layer is not disposed, and a positive electrode tab is connected to the exposed portion of the positive electrode current collector.

[0018] The exposed portion of the positive electrode current collector may be provided at one location, for example, traversing the width direction of the strip-shaped positive electrode current collector. That is, the exposed portion of the positive electrode current collector may be provided so as to include both ends of the strip-shaped positive electrode current collector in the width direction. Alternatively, the exposed portion of the positive electrode current collector may be provided at multiple locations spaced apart along the length direction of the strip-shaped positive electrode current collector on one end of the strip-shaped positive electrode current collector in the width direction. In this case, the exposed portion of the positive electrode current collector only needs to be formed to have an area of ​​a size to which a positive electrode tab can be connected.

[0019] In the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m, and the ratio (A / C) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies 1.00 ≤ A / C ≤ 1.86.

[0020] In the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, it is important that (i) at least one end of the strip-shaped positive electrode current collector in the width direction is provided with an exposed portion of the positive electrode current collector where the positive electrode mixture layer is not disposed, and a positive electrode tab is connected to the exposed portion of the positive electrode current collector; (ii) the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m; and (iii) the ratio (A / C) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies the relationship 1.00 ≤ A / C ≤ 1.86. The reasons for this will be explained below.

[0021] When a non-aqueous electrolyte secondary battery has a wound electrode group, if the strip-shaped negative electrode current collector experiences greater tensile stress than the strip-shaped positive electrode current collector, the expansion of the positive electrode current collector may not be able to keep up with the expansion of the negative electrode current collector, causing only the strip-shaped negative electrode current collector to expand. As a result, variations may occur in the radial distance between the strip-shaped positive electrode and the strip-shaped negative electrode of the wound electrode group. In this case, parts of the wound electrode group become more easily charged and parts become less easily charged (i.e., charge / discharge unevenness occurs), and the battery capacity of the non-aqueous electrolyte secondary battery decreases with each repeated charge / discharge cycle. In other words, the cycle maintenance rate of the non-aqueous electrolyte secondary battery decreases. Furthermore, if metallic lithium is locally deposited in the easily charged part of the strip-shaped negative electrode of the wound electrode group, there is a concern that as the internal temperature of the non-aqueous electrolyte secondary battery rises, the metallic lithium will react with the non-aqueous electrolyte, reducing the thermal stability of the non-aqueous electrolyte secondary battery.

[0022] Furthermore, in the band-shaped positive electrode of a wound electrode group, if an exposed portion of the positive electrode current collector is provided on at least one end in the width direction of the band-shaped positive electrode current collector, and the positive electrode tab is connected to the exposed portion of the positive electrode current collector, then the radial movement of the exposed portion of the positive electrode current collector is restricted at the connection point with the positive electrode tab. Therefore, when the negative electrode mixture layer expands during charging of the wound electrode group and presses the band-shaped positive electrode radially, this pressure may cause the exposed portion of the positive electrode current collector to break. In other words, "foil breakage" may occur in the band-shaped positive electrode. And, as a result of the breakage of the exposed portion of the positive electrode current collector, the positive electrode tab may become isolated, and the current collecting performance may be significantly reduced.

[0023] However, in the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, (i) at least one end of the strip-shaped positive electrode current collector in the width direction is provided with an exposed portion of the positive electrode current collector where the positive electrode mixture layer is not disposed, and a positive electrode tab is connected to the exposed portion of the positive electrode current collector, (ii) the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m, and (iii) the ratio (A / C) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies the relationship 1.00 ≤ A / C ≤ 1.86. In other words, in the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, a positive electrode tab is connected to the exposed portion of the positive electrode current collector, and although the radial movement of the exposed portion of the positive electrode current collector is restricted, as described in (ii) above, since the strip-shaped positive electrode current collector has sufficient tensile strength, even if the negative electrode mixture layer expands and presses radially against the strip-shaped positive electrode during charging of the wound electrode group, it is possible to suppress the rupture of the exposed portion of the positive electrode current collector. In other words, it is possible to suppress the occurrence of "foil breakage" in the strip-shaped positive electrode.

[0024] Furthermore, in the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, (ii) and (iii) above are satisfied. That is, the tensile strength A of the strip-shaped positive electrode current collector is set within an appropriate range, and the tensile strength A of the strip-shaped positive electrode current collector and the tensile strength C of the strip-shaped negative electrode current collector are not excessively separated. Therefore, even if a large tensile stress is generated in the strip-shaped negative electrode current collector during charging and discharging of the non-aqueous electrolyte secondary battery, the strip-shaped positive electrode current collector can sufficiently follow the elongation of the strip-shaped negative electrode current collector. As a result, it is possible to suppress the elongation of only the strip-shaped negative electrode current collector, and thus sufficiently suppress variations between the strip-shaped positive electrode and the strip-shaped negative electrode in the radial direction of the wound electrode group. As a result, the occurrence of charge-discharge unevenness in the wound electrode group is suppressed, and thus a decrease in the cycle maintenance rate in the non-aqueous electrolyte secondary battery can be suppressed. In addition, it is possible to suppress a decrease in the safety of the non-aqueous electrolyte secondary battery (for example, a decrease in thermal stability) caused by charge-discharge unevenness.

[0025] The configuration of the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure will be described in detail below.

[0026] (Positive Electrode) A non-aqueous electrolyte secondary battery according to the embodiment of the present disclosure comprises a strip-shaped positive electrode. As described above, the strip-shaped positive electrode comprises a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the strip-shaped positive electrode current collector. The positive electrode mixture layer may be disposed on only one surface of the strip-shaped positive electrode current collector, or it may be disposed on both surfaces of the strip-shaped positive electrode current collector (two opposing surfaces in the thickness direction).

[0027] The positive electrode mixture layer contains a positive electrode active material as an essential component. The positive electrode mixture layer may also contain conductive materials, binders, and thickeners as optional components. The positive electrode mixture layer can be obtained by applying a positive electrode mixture slurry containing the positive electrode active material to at least one surface of a strip-shaped positive electrode current collector to form a coating, and then drying this coating. The dried coating may be rolled as needed. The positive electrode mixture slurry may contain conductive materials, binders, and thickeners. The positive electrode mixture slurry may also contain a dispersion medium for dispersing the positive electrode active material, etc. Examples of dispersion media include water, alcohol, ether, and N-methyl-2-pyrrolidone (NMP).

[0028] The thickness of the positive electrode mixture layer may be 3 μm or more, or 5 μm or more. Alternatively, the thickness of the positive electrode mixture layer may be 200 μm or less, or 150 μm or less.

[0029] As the positive electrode active material, a material that reversibly intercepts and releases lithium ions can be used. For example, an olivine-type lithium salt (LiFePO) can be used as the positive electrode active material. ４etc.), chalcogen compounds (e.g., titanium disulfide or molybdenum disulfide), manganese dioxide, and lithium-containing composite metal oxides. Examples of the lithium-containing composite metal oxide include lithium transition metal composite oxides containing lithium and a transition metal. The lithium transition metal composite oxide contains, as a transition metal element, at least one selected from the group consisting of Sc, Y, Mn, V, Fe, Co, Ni, Cu, and Cr, for example. The lithium transition metal composite oxide may contain an element other than the transition metal element. The element other than the transition metal element may be, for example, at least one selected from the group consisting of Na, Mg, Zn, Al, Pb, Sb, and B. Among the various elements described above, the lithium transition metal composite oxide preferably contains at least one selected from the group consisting of Mn, Al, Co, Ni, and Mg. The positive electrode active material is usually used in a particulate state.

[0030] Examples of the positive electrode active material include Li ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Li ｘ Co ｙ M １－ｙ O ｚ , Li ｘ Ni １－ｙ M ｙ O ｚ , Li ｘ Mn ２ O ４ , Li ｘ Mn ２－ｙ M ｙ O ４ , LiMPO ４ , and Li ２ MPO ４Examples include F. In the above compositional formula, M is at least one element selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and B. Also, in the above compositional formula, x satisfies 0 < x ≤ 1.2, y satisfies 0 ≤ y ≤ 0.9, and z satisfies 2.0 ≤ z ≤ 2.3.

[0031] The positive electrode mixture layer may contain one type of positive electrode active material as described above, or it may contain two or more types in combination.

[0032] Examples of conductive materials include carbon black and carbon fibers. Examples of carbon black include acetylene black and Ketjenblack, and examples of carbon fibers include carbon nanotubes. Examples of binders include fluororesins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubbery polymers. Examples of fluororesins include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF). Examples of rubbery polymers include styrene-butadiene rubber (SBR) and nitrile-butadiene copolymer (NBR). Examples of thickeners include carboxymethylcellulose (CMC) and salts of CMC. Examples of salts include sodium salts and potassium salts.

[0033] As a strip-shaped positive electrode current collector, for example, a conductive sheet can be used. The strip-shaped positive electrode current collector may be a non-porous conductive sheet. The non-porous conductive sheet may be, for example, a non-porous metal foil. The strip-shaped positive electrode current collector may be a porous conductive sheet. The porous conductive sheet may be, for example, a metal mesh sheet or perforated metal. Examples of materials constituting the positive electrode current collector include Al, Al alloy, Ti, Ti alloy, Fe, and Fe alloy. The thickness of the positive electrode current collector may be, for example, 5 μm to 50 μm, or 10 μm to 30 μm.

[0034] When the thickness of the strip-shaped positive electrode current collector is TA (μm) and the thickness of the positive electrode mixture layer is TB (μm), the ratio of TA to the sum of TA and TB (TA + TB) (TA / (TA + TB)) may be 0.07 or greater, or 0.08 or greater. Also, TA / (TA + TB) may be 0.15 or less, or 0.10 or less. In recent years, in order to increase the capacity of non-aqueous secondary batteries, the thickness of the positive electrode mixture layer of the strip-shaped positive electrode has been increasing, and consequently, the thickness of the strip-shaped positive electrode current collector of the strip-shaped positive electrode has been decreasing. However, as long as TA / (TA + TB) is within the above range, even if the negative electrode mixture layer expands and contracts significantly during charging and discharging, it is possible to suitably suppress the rupture of the exposed portion of the positive electrode current collector as a result, and to suitably suppress a decrease in cycle maintenance rate and safety. In other words, in a non-aqueous electrolyte secondary battery, it is possible to achieve high capacity while effectively suppressing the breakage of the exposed portion of the positive electrode current collector, and effectively suppressing a decrease in cycle maintenance rate and safety.

[0035] (Negative Electrode) A non-aqueous electrolyte secondary battery according to the embodiment of the present disclosure includes a strip-shaped negative electrode. As described above, the strip-shaped negative electrode includes a strip-shaped negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the strip-shaped negative electrode current collector. The negative electrode mixture layer may be disposed on only one surface of the strip-shaped negative electrode current collector, or on both surfaces of the strip-shaped negative electrode current collector (two opposing surfaces in the thickness direction).

[0036] The negative electrode mixture layer contains a negative electrode active material as an essential component. The negative electrode mixture layer may also contain conductive materials, binders, and thickeners as optional components. The conductive materials, binders, and thickeners exemplified in the positive electrode mixture layer can be used. The negative electrode mixture layer can be obtained by applying a negative electrode mixture slurry containing the negative electrode active material to at least one surface of a strip-shaped negative electrode current collector to form a coating, and then drying this coating. The dried coating may be rolled as needed. The negative electrode mixture slurry may contain conductive materials, binders, and thickeners. The negative electrode mixture slurry may also contain a dispersion medium for dispersing the negative electrode active material, etc. Examples of dispersion media include water, alcohol, ether, and N-methyl-2-pyrrolidone (NMP).

[0037] The thickness of the negative electrode mixture layer may be 3 μm or more, or 5 μm or more. Alternatively, the thickness of the negative electrode mixture layer may be 200 μm or less, or 150 μm or less.

[0038] As the negative electrode active material, a material that reversibly intercepts and releases lithium ions can be used. The negative electrode active material is usually used in particulate form. Examples of negative electrode active materials include carbonaceous materials and silicon-containing materials. Examples of carbonaceous materials include graphite, easily graphitizable carbon (soft carbon), and poorly graphitizable carbon (hard carbon). Examples of silicon-containing materials include elemental Si, silicon alloys, silicon compounds, and composite materials in which a silicon phase is dispersed within the lithium ion conducting phase. Examples of silicon compounds include silicon oxides. In composite materials, the lithium ion conducting phase is also called the matrix phase.

[0039] The negative electrode mixture layer may contain one type of negative electrode active material as described above, or it may contain a combination of two or more types. Preferably, the negative electrode mixture layer contains a silicon-containing material as the negative electrode active material. By including a silicon-containing material in the negative electrode mixture layer, the capacity of the non-aqueous electrolyte secondary battery can be increased. The content of the silicon-containing material in the negative electrode mixture layer is preferably 2% by mass or more, and more preferably 5% by mass or more.

[0040] When the negative electrode mixture layer contains 2% by mass or more of silicon-containing material, it is possible to further increase the capacity of the non-aqueous electrolyte secondary battery. However, the degree of expansion and contraction of the negative electrode mixture layer during charging and discharging increases, and the problems caused by this become even more pronounced. Specifically, problems such as rupture of the exposed portion of the positive electrode current collector, a decrease in cycle maintenance rate, and a decrease in safety become even more pronounced. However, in the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m, and the ratio of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector (A / C) satisfies the relationship 1.00 ≤ A / C ≤ 1.86. Therefore, even in such a case, rupture of the exposed portion of the positive electrode current collector can be sufficiently suppressed, and a decrease in cycle maintenance rate and a decrease in safety can be sufficiently suppressed.

[0041] Furthermore, the content of silicon-containing material in the negative electrode mixture layer is preferably 15% by mass or less, and more preferably 10% by mass or less. In addition to the silicon-containing material, the negative electrode mixture layer may also contain carbonaceous material. In this case, the mass ratio of the carbonaceous material to the total mass of the silicon-containing material and the carbonaceous material may be, for example, 80% by mass or more, or 90% by mass or more.

[0042] The negative electrode composite layer preferably contains a composite material as the silicon-containing material. As described above, the composite material is composed of a silicon phase dispersed within the lithium-ion conductive phase. In the composite material, stress is generated due to the expansion and contraction of the silicon phase during charging and discharging, but this stress can be relieved by the lithium-ion conductive phase. This suppresses the occurrence of cracks and fractures in the composite material. Therefore, in addition to achieving high capacity by including silicon, the composite material can suppress the deterioration of cycle characteristics caused by the occurrence of cracks and fractures.

[0043] In composite materials, examples of lithium ion conducting phases include silicate phase, silicon oxide phase, carbon phase, and silicide phase. The lithium ion conducting phase may contain a silicate phase as its main component (content of 50% by mass or more), and may further contain a silicon oxide phase.

[0044] The silicate phase is composed of a compound containing a metal element, silicon (Si), and oxygen (O). Examples of metal elements include alkali metal elements and Group 2 elements of the long-period periodic table. An example of an alkali metal element is lithium. Hereafter, Group 2 elements of the long-period periodic table will also be simply referred to as Group 2 elements. The silicon oxide phase is composed of a compound of Si and O. The main component of the silicon oxide phase (for example, 95-100% by mass) may be silicon dioxide. The silicon oxide phase is composed of SiO ｘ The phase may be represented by (0.5 ≤ x < 1.6). The carbon phase may contain crystalline carbon (graphite) or amorphous carbon with low crystallinity (i.e., amorphous carbon). The amorphous carbon may be, for example, poorly graphitizable carbon (hard carbon), easily graphitizable carbon (soft carbon), or other types. The silicide constituting the silicide phase may be an intermetallic compound of silicon and the metallic element Me. The metallic element Me may be at least one selected from the group consisting of Al, Mg, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

[0045] The silicate phase preferably includes a lithium silicate phase. The silicate phase may also be a lithium silicate phase. The lithium silicate phase is advantageous in that lithium ions can easily enter and exit. The lithium silicate phase is also advantageous in that it has a smaller irreversible capacity compared to the silicon oxide phase. The lithium silicate phase is Li ２ Si ２ O ５ Li ２ SiO ３ , and Li ４ SiO ４ It may include at least one selected from the group consisting of the following.

[0046] In the lithium silicate phase, the atomic ratio of O to Si (O / Si) may be greater than 2 and less than 4. This is advantageous in that it can improve the stability and ionic conductivity of the lithium silicate phase. The atomic ratio of O / Si may be greater than 2 and less than 3. Also, in the lithium silicate phase, the atomic ratio of Li to Si (Li / Si) may be greater than 0 and less than 4.

[0047] The silicate phase may contain an element M in addition to Li, Si, and O. The inclusion of element M in the silicate phase can improve its stability and ionic conductivity. Furthermore, the inclusion of element M in the silicate phase can suppress side reactions between the silicate phase and the non-aqueous electrolyte.

[0048] The silicate phase may contain, as element M, at least one of an alkali metal element other than lithium and at least one of a group 2 element. As the alkali metal element other than lithium, at least one of Na and K is used due to its low cost. The group 2 element may be at least one of Ca and Mg.

[0049] The silicate phase may contain, as element M, at least one selected from the group consisting of boron (B), aluminum (Al), zirconium (Zr), niobium (Nb), tantalum (Ta), vanadium (V), lanthanum (La), yttrium (Y), titanium (Ti), phosphorus (P), bismuth (Bi), zinc (Zn), tin (Sn), lead (Pb), antimony (Sb), cobalt (Co), erbium (Er), fluorine (F), and tungsten (W).

[0050] The silicate phase may contain, as element M, rare earth elements other than lanthanum (La), yttrium (Y), and erbium (Er). The silicate phase may also contain, as rare earth elements, at least one selected from the group consisting of cerium (Ce), praseodymium (Pr), and neodymium (Nd).

[0051] The silicate phase may contain metallic elements such as iron (Fe), chromium (Cr), nickel (Ni), manganese (Mn), copper (Cu), and molybdenum (Mo).

[0052] Element M may form a compound. This compound may be a silicate containing element M, or an oxide containing element M. In a silicate containing element M, the proportion of element M among elements other than oxygen may be 1 mol% or more and 40 mol% or less.

[0053] From the viewpoint of increasing capacity and improving cycle characteristics, the silicon phase content in the composite material may be 45% by mass or more, 50% by mass or more, or 58% by mass or more. Furthermore, the upper limit of the silicon phase content in the composite material may be 70% by mass.

[0054] The average particle size of the composite material may be 1 μm or larger, 4 μm or larger, or 6 μm or larger. Alternatively, the average particle size of the composite material may be 25 μm or smaller, 15 μm or smaller, or 8 μm or smaller. In this case, good battery performance is easily obtained in non-aqueous electrolyte secondary batteries. The average particle size of the composite material refers to the particle size (median diameter (D50)) at which the cumulative frequency of the smallest particle size accounts for 50% in the volume-based particle size distribution. This particle size is also called the median diameter. The average particle size of the composite particles can be determined using a laser diffraction / scattering particle size distribution analyzer.

[0055] At least a portion of the surface of the composite material may be covered with a coating layer. In a composite material covered with a coating layer, the ratio R of the mass of the coating layer to the total mass of the composite material and the coating layer is preferably 3% by mass or more and 5% by mass or less. The ratio R can be determined from the difference in mass of the composite material before and after the formation of the coating layer. The coating layer may contain a conductive carbon material. From the viewpoint of ensuring conductivity, the thickness of the coating layer is preferably 1 nm or more. The thickness of the coating layer may be 200 nm or less, 100 nm or less, or 10 nm or less.

[0056] The coating layer can be formed, for example, by obtaining a mixture of a carbon material and composite particles, and then firing this mixture to carbonize the carbon material. This allows for the formation of a coating layer that covers at least a portion of the surface of the composite particles. Examples of carbon materials for forming the coating layer include coal pitch, petroleum pitch, and phenolic resin. The firing temperature can be, for example, in the range of 450°C to 1000°C. The firing time may be in the range of 1 hour to 10 hours.

[0057] As a strip-shaped negative electrode current collector, for example, a conductive sheet can be used. The strip-shaped negative electrode current collector may be a non-porous conductive sheet. The non-porous conductive sheet may be, for example, a non-porous metal foil. The strip-shaped negative electrode current collector may be a porous conductive sheet. The porous conductive sheet may be, for example, a metal mesh sheet or perforated metal. Examples of materials constituting the negative electrode current collector include stainless steel, nickel, nickel alloys, copper, and copper alloys. The thickness of the negative electrode current collector may be, for example, 5 μm to 50 μm, or 10 μm to 30 μm.

[0058] <Method for Manufacturing Composite Materials> The following describes a method for manufacturing composite materials containing a lithium silicate phase as the lithium ion conducting phase. Composite materials containing a lithium silicate phase are manufactured through the following four steps.

[0059] <<Step 1>> Step 1 is the step of preparing or synthesizing lithium silicate. In Step 1, lithium silicate may be prepared by purchasing a commercially available product, or lithium silicate may be synthesized by various known methods.

[0060] ≪Second Step≫ The second step is to combine lithium silicate and silicon to form a composite intermediate containing a lithium silicate phase and a silicon phase dispersed in the lithium silicate phase. The silicon may be silicon particles. In the second step, for example, after obtaining a mixture of lithium silicate and silicon, the mixture is crushed while applying shear force to obtain a finely powdered composite intermediate. The crushing of the mixture may be carried out while stirring the mixture. The crushing of the mixture can be carried out using a crushing device such as a ball mill. At this time, in the composite intermediate, the crushed silicon is dispersed in the lithium silicate. That is, in the composite intermediate, the crushed silicon constitutes the silicon phase, and the lithium silicate constitutes the lithium silicate phase (matrix phase).

[0061] <Third Step> The third step is to heat-treat the composite intermediate obtained in the second step to form a sintered body containing a lithium silicate phase and a silicon phase dispersed in the lithium silicate phase. In the third step, for example, the sintered body is formed by firing the composite intermediate obtained in the second step while applying pressure with a hot press or the like. The firing of the composite intermediate may be carried out in an inert atmosphere. The inert atmosphere may be an argon gas atmosphere or a nitrogen gas atmosphere. The firing temperature of the composite intermediate may be, for example, in the range of 450°C to 1000°C. The firing time of the composite intermediate may be, for example, 1 hour to 10 hours.

[0062] <<Fourth Step>> The fourth step is to pulverize the sintered body obtained in the third step to obtain a composite material containing a silicate phase and a silicon phase dispersed within the silicate phase. By appropriately adjusting the pulverization conditions, a composite material having a desired average particle size can be obtained. In this case, the composite material will be in a granular state. In the fourth step, the above pulverization can also be carried out using a pulverizing device such as a ball mill.

[0063] Furthermore, when manufacturing a composite material that includes a phase other than the lithium silicate phase as the lithium ion conducting phase, in the first step of the composite material manufacturing method described above, a material for forming the desired phase may be prepared or synthesized instead of lithium silicate. For example, when manufacturing a composite material that includes a carbon phase or a silicide phase as the lithium ion conducting phase, a carbon material or silicide may be prepared instead of lithium silicate, or silicide may be synthesized by various known methods.

[0064] In the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m, as described above. Furthermore, in the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, the ratio (A / C) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies 1.00 ≤ A / C ≤ 1.86.

[0065] The tensile strength A of a strip-shaped positive electrode current collector can be adjusted by the material used to form the positive electrode current collector. For example, comparing pure aluminum and aluminum alloys, aluminum alloys generally have higher tensile strength. Therefore, the tensile strength A can be increased by forming the strip-shaped positive electrode current collector from an aluminum alloy. On the other hand, the tensile strength A can be decreased by forming the strip-shaped positive electrode current collector from pure aluminum. Furthermore, when forming the strip-shaped positive electrode current collector from pure aluminum, the tensile strength A can also be increased by making the aluminum crystal grains finer. Conversely, the tensile strength A can also be decreased by making the aluminum crystal grains coarser. The tensile strength C of a strip-shaped negative electrode current collector can be adjusted by the material used to form the negative electrode current collector. For example, the tensile strength C of the strip-shaped negative electrode current collector can be increased by forming it from a metal material with fine crystal grains. On the other hand, the tensile strength C of the strip-shaped negative electrode current collector can be decreased by forming it from a metal material with coarse crystal grains.

[0066] The tensile strength A of a strip-shaped positive electrode current collector can be measured by a tensile test in accordance with JIS Z 2241. Specifically, the tensile strength A can be measured according to the following procedure. Measurement procedure (1) Cut out strip-shaped test pieces measuring 120 mm in length and 8 mm in width from any five locations on the strip-shaped positive electrode current collector. Each strip-shaped test piece is cut from the strip-shaped positive electrode current collector so that its length and width directions are approximately the same as the length and width directions of the strip-shaped positive electrode current collector, respectively. Hereinafter, the strip-shaped test pieces will also be simply referred to as test pieces. (2) Pull the first test piece in the length direction using a tensile testing machine. Specifically, with both ends of the first test piece in the length direction gripped by a pair of chuck fixtures arranged vertically, pull the first test piece in the length direction. The tensile speed shall be 5 mm / min. Of the pair of chuck fixtures, the one positioned vertically upward is attached to the crosshead, so the tensile speed is adjusted to 5 mm / min by setting the displacement speed of the crosshead to 5 mm / min. (3) The first test piece is pulled at a tensile speed of 5 mm / min until fracture occurs, and the maximum stress generated until the first test piece fractures is determined. Then, this maximum stress is divided by the width of the test piece (8 mm (= 0.008 m)) to calculate the value, and this calculated value is taken as the tensile strength of the first test piece. The unit of the above maximum stress is N. (4) Steps (2) and (3) above are performed for each of the five test pieces (the first to fifth test pieces), and after determining the tensile strength for each of the five test pieces, these are arithmetic mean to determine the tensile strength A of the strip-shaped positive electrode current collector.

[0067] Furthermore, when determining the tensile strength A (N / m) of a strip-shaped positive electrode current collector using a wound electrode group taken from a non-aqueous electrolyte secondary battery, the strip-shaped test piece described in (1) above can be obtained by cutting it out from the exposed portion of the positive electrode current collector on the strip-shaped positive electrode after the strip-shaped positive electrode has been taken from the wound electrode group. Alternatively, the strip-shaped test piece described in (1) above may be obtained by removing at least a portion of the positive electrode mixture layer from the strip-shaped positive electrode using a solvent or the like to obtain the exposed portion of the positive electrode current collector, and then cutting it out from the obtained exposed portion of the positive electrode current collector.

[0068] The tensile strength C of a strip-shaped negative electrode current collector can be measured in the same manner as the tensile strength A of a strip-shaped positive electrode current collector. Specifically, it can be measured by a tensile test in accordance with JIS Z 2241, following the same procedure as described above.

[0069] The tensile strength C of the strip-shaped negative electrode current collector may be 1.5 N / m or more, or 2.0 N / m or more. Alternatively, the tensile strength C of the strip-shaped negative electrode current collector may be 3.9 N / m or less, 3.0 N / m or less, or 2.2 N / m or less. By having the tensile strength C of the strip-shaped negative electrode current collector within the above range, it is possible to suppress the tensile strength C of the strip-shaped negative electrode current collector from becoming excessively greater than the tensile strength A of the strip-shaped positive electrode current collector. This makes it possible to suppress excessive elongation of only the strip-shaped negative electrode current collector during charging and discharging of a non-aqueous electrolyte secondary battery equipped with a wound electrode group. Furthermore, by having the tensile strength C of the strip-shaped negative electrode current collector within the above range, it becomes easier to adjust A / C within the above range (1.00 ≤ A / C ≤ 1.86).

[0070] In the non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, the product (A × B) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector and the elongation at break B (%) of the strip-shaped positive electrode current collector is preferably 7.5 N / m・% ≤ A × B. A × B may also satisfy the relationship 8.0 N / m・% ≤ A × B, or 8.5 N / m・% ≤ A × B. Furthermore, A × B may satisfy the relationship A × B ≤ 20.0 N / m・%, A × B ≤ 15.0 N / m・%, or A × B ≤ 10.0 N / m・%. By A × B being within the above range, the strip-shaped positive electrode current collector exhibits sufficient strength while also exhibiting sufficient elongation. In other words, the strip-shaped positive electrode current collector exhibits excellent toughness.

[0071] The elongation at break B of a strip-shaped positive electrode current collector can be adjusted by the material used to form the positive electrode current collector. For example, the elongation at break B can be increased by forming the strip-shaped positive electrode current collector with a metal material with coarse grains. On the other hand, the elongation at break B can be decreased by forming the strip-shaped positive electrode current collector with a metal material with fine grains.

[0072] The elongation at break B (%) of a strip-shaped positive electrode current collector can be measured according to the following procedure in accordance with JIS Z 2241. Measurement procedure (1) Cut out strip-shaped test pieces measuring 120 mm in length and 8 mm in width from any five locations on the strip-shaped positive electrode current collector. Each strip-shaped test piece is cut from the strip-shaped positive electrode current collector so that its length and width directions are approximately the same as those of the strip-shaped positive electrode current collector. Hereinafter, the strip-shaped test pieces will also be simply referred to as test pieces. (2) Pull the first test piece in the length direction using a tensile testing machine. Specifically, with both ends of the first test piece in the length direction gripped by a pair of chuck fixtures arranged vertically, the first test piece is pulled in the length direction. The tensile speed shall be 5 mm / min. Of the pair of chuck fixtures, the one positioned vertically upward is attached to the crosshead, so the tensile speed is adjusted to 5 mm / min by setting the displacement speed of the crosshead to 5 mm / min. (3) The first test piece is pulled at a tensile speed of 5 mm / min until fracture occurs. The percentage of elongation is calculated from the distance the crosshead moves (mm) at the time of fracture relative to the length between the chucks of the first test piece before testing (50 mm), and this calculated value is taken as the fracture elongation rate (%) of the first test piece. (4) The above steps (2) and (3) are performed for each of the five test pieces (the first to fifth test pieces), and after determining the fracture elongation rate for each of the five test pieces, these are arithmetic mean to obtain the fracture elongation rate B (%) of the strip-shaped positive electrode current collector.

[0073] Furthermore, when determining the break elongation B (%) of a strip-shaped positive electrode current collector using a wound electrode group taken from a non-aqueous electrolyte secondary battery, the strip-shaped test piece described in (1) above can be obtained by cutting it out from the exposed portion of the positive electrode current collector on the strip-shaped positive electrode after taking the strip-shaped positive electrode from the wound electrode group. Alternatively, the strip-shaped test piece described in (1) above may be obtained by removing at least a portion of the positive electrode mixture layer from the strip-shaped positive electrode using a solvent or the like to obtain the exposed portion of the positive electrode current collector, and then cutting it out from the obtained exposed portion of the positive electrode current collector.

[0074] The elongation rate B (%) at break of the strip-shaped positive electrode current collector may be 1.5% or more, or 2.0% or more. Furthermore, the elongation rate B (%) at break of the strip-shaped positive electrode current collector may be 4.0% or less, 3.0% or less, or 2.5% or less. By having the elongation rate B (%) at break of the strip-shaped positive electrode current collector within the above range, even if the negative electrode mixture layer of the strip-shaped negative electrode expands and presses against the strip-shaped positive electrode during charging of the non-aqueous electrolyte secondary battery, the strip-shaped positive electrode current collector can stretch appropriately. In this case, the strip-shaped positive electrode current collector can adequately follow the stretch of the strip-shaped negative electrode current collector. Additionally, having the elongation rate B (%) at break of the strip-shaped positive electrode current collector within the above range makes it easier to adjust A × B within the above range (7.5 ≤ A × B). Furthermore, the strip-shaped positive electrode current collector exhibits excellent toughness.

[0075] (Separator) The non-aqueous electrolyte secondary battery according to the embodiment of this disclosure comprises a strip-shaped separator. The strip-shaped separator is disposed between a strip-shaped positive electrode and a strip-shaped negative electrode. Various known separators can be used as the separator in a non-aqueous electrolyte secondary battery. The separator may be, for example, a microporous film formed using a polymer material. Examples of polymer materials include polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, and cellulose compounds. Examples of cellulose compounds include carboxymethylcellulose (CMC) and hydroxypropylcellulose. The thickness of the separator is not particularly limited and may be 10 μm or more, or 15 μm or more. The thickness of the separator may be 30 μm or less, or 20 μm or less.

[0076] (Non-aqueous electrolyte) The non-aqueous electrolyte may be a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte. The non-aqueous electrolyte may be a gel electrolyte using a gel-like polymer or the like. When the non-aqueous electrolyte is a non-aqueous electrolyte solution, the non-aqueous electrolyte may contain a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. The concentration of the lithium salt in the non-aqueous electrolyte may be, for example, 0.5 mol / L or more and 2.0 mol / L or less. By setting the concentration of the lithium salt within the above range, a non-aqueous electrolyte with excellent ionic conductivity and appropriate viscosity can be obtained. However, the concentration of the lithium salt is not limited to the above range.

[0077] Examples of non-aqueous solvents include cyclic carbonate esters, linear carbonate esters, cyclic carboxylic acid esters, and linear carboxylic acid esters. Examples of cyclic carbonate esters include propylene carbonate (PC) and ethylene carbonate (EC). Cyclic carbonate esters may also include cyclic carbonate esters having carbon-carbon unsaturated bonds. Examples of such cyclic carbonate esters include fluorinated cyclic carbonate esters (e.g., fluoroethylene carbonate (FEC)), vinylene carbonate (VC), and vinylethylene carbonate. Examples of linear carbonate esters include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone (GVL). Examples of linear carboxylic acid esters include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate. The non-aqueous solvent may be used alone or in combination of two or more types.

[0078] Various known lithium salts can be used as the lithium salt. For example, LiClO ４ LiBF ４ LiPF ６ LiAlCl ４LiSbF ６ , LiSCN, LiCF ３ SO ３ LiCF ３ CO ２ LiAsF ６ LiB １０ Cl １０ It is preferable to use lithium lower aliphatic carboxylates, LiCl, LiBr, LiI, borates, and imide salts. Examples of borates include lithium bis(1,2-benzenediolate(2-)-O,O')borate, lithium bis(2,3-naphthalenediolate(2-)-O,O')borate, lithium bis(2,2'-biphenyldiolate(2-)-O,O')borate, and lithium bis(5-fluoro-2-oleate-1-benzenesulfonic acid-O,O')borate. Examples of imide salts include lithium bis(fluorosulfonyl)imide (LiN(FSO) ２ ) ２ ), bistrifluoromethanesulfonate lithium (LiN(CF ３ SO ２ ) ２ ), trifluoromethanesulfonic acid nonafluorobutanesulfonic acid lithium (LiN(CF ３ SO ２ ) (C ４ F ９ SO ２ )), and bispentafluoroethanesulfonate lithium (LIN(C) ２ F ５ SO ２ ) ２ Examples include the following. Lithium salts may be used individually or in combination of two or more types.

[0079] (Outer casing) A non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure may include an outer casing. In a non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure, an electrode group in which a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator placed between the strip-shaped positive electrode and the strip-shaped negative electrode are wound in the longitudinal direction, and a non-aqueous electrolyte are housed inside the outer casing. The outer casing may be a battery case. Various known battery cases can be used as the battery case. The battery case may have a cylindrical shape or a rectangular shape. The battery case may include a case body having a bottomed cylindrical shape, a sealing body that seals the opening of the case body, and a gasket disposed between the case body and the sealing body. The case body can be formed using, for example, a metal material. The case body may be, for example, a metal case body mainly composed of iron.

[0080] In the following, an example of a non-aqueous electrolyte secondary battery according to one embodiment of this disclosure will be described with reference to the drawings.

[0081] Figure 1 is a schematic longitudinal cross-sectional view showing a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure. As shown in Figure 1, the non-aqueous electrolyte secondary battery 10 is a cylindrical battery comprising a cylindrical case, an electrode group 14, and a non-aqueous electrolyte (not shown). In the example shown in Figure 1, the electrode group 14 is a wound electrode group. The electrode group 14 is housed in the battery case and is in contact with the non-aqueous electrolyte.

[0082] The battery case includes a case body 15, which is a bottomed cylindrical metal container, and a sealing body 16 that seals the opening of the case body 15. A gasket 27 is placed between the case body 15 and the sealing body 16. The placement of the gasket 27 ensures that the battery case is airtight. Inside the case body 15, insulating plates 17 and 18 are placed at both ends of the electrode group 14 in the direction of the winding axis, respectively.

[0083] The case body 15 has, for example, a stepped portion 21. The stepped portion 21 is formed, for example, by partially pressing the side wall of the case body 15 from the outside. The stepped portion 21 may be formed in an annular shape on the side wall of the case body 15 along the circumferential direction of a virtual circle defined by the case body 15. In this case, the sealing body 16 is supported, for example, by the opening side surface of the stepped portion 21.

[0084] 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. These members are stacked in this order in the sealing body 16. The sealing body 16 is installed in the opening of the case body 15 such that the cap 26 is located on the outside of the case body 15 and the filter 22 is located on the inside of the case body 15.

[0085] The lower valve body 23 and the upper valve body 25 are connected at their respective centers. An insulating member 24 is positioned between the peripheral edge of the lower valve body 23 and the peripheral edge of the upper valve body 25. The filter 22 and the lower valve body 23 are connected at their respective peripheral edges. The upper valve body 25 and the cap 26 are connected at their respective peripheral edges. Each of the above-mentioned components constituting the sealing body 16 has, for example, a disc shape or a ring shape. Each of the above-mentioned components is electrically connected to one another, except for the insulating member 24.

[0086] The lower valve body 23 has a ventilation hole. Therefore, if the internal pressure of the battery case rises due to abnormal heat generation or other reasons, the upper valve body 25 bulges towards the cap 26 and separates from the lower valve body 23. This disconnects the electrical connection between the lower valve body 23 and the upper valve body 25. If the internal pressure rises further, the upper valve body 25 ruptures, and gas is released through the opening formed in the cap 26.

[0087] The electrode group 14 includes a positive electrode 11, a negative electrode 12, and a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all strip-shaped. The width direction of the strip-shaped positive electrode 11 and negative electrode 12 is, for example, parallel to the winding axis direction of the electrode group 14. The separator 13 is positioned between the positive electrode 11 and the negative electrode 12. The positive electrode 11 and the negative electrode 12 are wound in a spiral shape with the separator 13 interposed between them.

[0088] In the non-aqueous electrolyte secondary battery 10, when observing a cross-section of the electrode group 14 in a direction perpendicular to the winding axis, the positive electrode 11 and the negative electrode 12 are alternately stacked in the radial direction of a virtual circle defined by the case body 15, with a separator 13 interposed between them.

[0089] The positive electrode 11 is electrically connected to a cap 26, which functions as a positive electrode terminal, via a positive electrode lead 19. In this specification, the positive electrode lead is synonymous with the positive electrode tab. The positive electrode lead 19 extends from the positive electrode 11 to the filter 22 through a through hole formed in the insulating plate 17. One end of the positive electrode lead 19 is connected, for example, near the center of the positive electrode 11 in the longitudinal direction, and the other end of the positive electrode lead 19 is welded, for example, to the electrode group 14 side of the filter 22.

[0090] The negative electrode 12 is electrically connected to the case body 15, which functions as a negative electrode terminal, via a negative electrode lead 20. One end of the negative electrode lead 20 is connected, for example, to the end of the negative electrode 12 in the longitudinal direction, and the other end of the negative electrode lead 20 is welded, for example, to the inner bottom surface of the case body 15. In this specification, the negative electrode lead is synonymous with the negative electrode tab.

[0091] (Note) The following technologies are disclosed in accordance with the above description. (Technology 1) A group of electrodes formed by winding a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator disposed between the strip-shaped positive electrode and the strip-shaped negative electrode in the longitudinal direction, and a non-aqueous electrolyte, wherein the strip-shaped positive electrode has a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the strip-shaped positive electrode current collector, the strip-shaped negative electrode has a strip-shaped negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the strip-shaped negative electrode current collector, at least one end of the strip-shaped positive electrode current collector in the width direction is provided with an exposed portion of the positive electrode current collector where the positive electrode mixture layer is not disposed, a positive electrode tab is connected to the exposed portion of the positive electrode current collector, the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m (Technology 2) A non-aqueous electrolyte secondary battery, wherein the ratio (A / C) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies 1.00 ≤ A / C ≤ 1.86. (Technology 1) The non-aqueous electrolyte secondary battery according to Technology 1, wherein the negative electrode mixture layer contains a silicon-containing material as a negative electrode active material, and the content of the silicon-containing material in the negative electrode mixture layer is 2% by mass or more. (Technology 3) The non-aqueous electrolyte secondary battery according to Technology 1 or 2, wherein the product (A × B) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector and the elongation at break B (%) of the strip-shaped positive electrode current collector satisfies 7.5 N / m・% ≤ A × B.

[0092] The present disclosure will be described below in detail based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0093] (Example 1) (1) Preparation of the negative electrode Silicon dioxide and Li ２ CO ３ The two were mixed to obtain a first mixture. The first mixture was calcined in air at 950°C for 10 hours to obtain a silicate. The obtained silicate was pulverized to an average particle size of 10 μm.

[0094] The silicate obtained as described above was mixed with silicon (average particle size 10 μm) to obtain a second mixture. In the second mixture, the mass ratio of silicate to silicon was 42:58.

[0095] The second mixture was ground while being mixed using a planetary ball mill. Specifically, the second mixture and 24 stainless steel balls were placed in the pot of the planetary ball mill, the lid of the pot was closed, and the second mixture was ground while being mixed at a rotation speed of 200-300 rpm for 25 hours. This yielded a powdered second mixture. The planetary ball mill used was a Fritsch P-5 model. The pot was made of stainless steel and had a volume of 500 mL. The diameter of the stainless steel balls was 20 mm. The mixing and grinding of the second mixture were carried out in an inert atmosphere. The inert atmosphere was an argon atmosphere. The same procedure was followed for subsequent experiments.

[0096] In an inert atmosphere, the powdered second mixture was removed from the pot of the planetary ball mill, and then, in an inert atmosphere, the powdered second mixture was fired using a hot press while applying pressure. This yielded a sintered body of the second mixture.

[0097] The sintered body of the second mixture was crushed to obtain particulate sintered body of the second mixture (hereinafter simply referred to as sintered body particles). The sintered body particles were sieved through a mesh to obtain composite particles with an average particle size (median diameter) of 6 μm. The composition of the main component of the silicate phase in the composite particles was Li ２ Si ２ O ５ The composition of the main component of the silicate phase in the composite particles was determined by cross-sectional SEM-EDX analysis.

[0098] The above composite particles and coal tar pitch were mixed in a mass ratio of 95:5 to obtain a third mixture. Then, the third mixture was calcined in an inert atmosphere at a temperature of 800°C to form a coating layer that covered at least a portion of the composite particles. In other words, the coating layer was formed by carbonizing a carbon material. As a result of the calcination, at least a portion of the coal tar pitch became amorphous carbon. Thus, the silicon-containing material according to Example 1 was obtained.

[0099] In the silicon-containing material according to Example 1, the ratio R of the mass of the coating layer to the total mass of the composite material and the coating layer was 3% by mass. The ratio R was measured according to the method described in the above Embodiments section.

[0100] The silicon-containing material described above and graphite were mixed to obtain the negative electrode active material according to Example 1. In the negative electrode active material according to Example 1, the mass ratio of the silicon-containing material to graphite was 5:95. The negative electrode active material according to Example 1, carboxymethylcellulose (CMC) sodium salt, styrene-butadiene rubber (SBR), and water were mixed to prepare a negative electrode mixture slurry. In the negative electrode mixture slurry, the mass ratio of the negative electrode active material, CMC sodium salt, and SBR was negative electrode active material:CMC sodium salt:SBR = 97.5:1.0:1.5. The above negative electrode mixture slurry was applied to both sides of the negative electrode current collector to form a coating film, and after drying the coating film, the dried coating film was rolled. This formed a negative electrode mixture layer on both sides of the negative electrode current collector.

[0101] In the negative electrode according to Example 1, the density of the negative electrode mixture layer is 1.5 g / cm³. ３ Yes, it was. Furthermore, a strip of copper foil (thickness: 8 μm) with a tensile strength C of 2.09 N / m was used as the negative electrode current collector. The tensile strength C of the strip of copper foil was measured according to the method described in the above embodiment section.

[0102] (2) Preparation of the positive electrode A positive electrode slurry was prepared by mixing lithium nickelate, which is the positive electrode active material, acetylene black (AB), polyvinylidene fluoride (PVDF), and N-methyl-2-pyrrolidone (NMP). In the positive electrode slurry, the mass ratio of lithium nickelate, AB, and PVDF was set to lithium nickelate:AB:PVDF = 95:2.5:2.5. The above positive electrode slurry was applied to both sides of the positive electrode current collector to form a coating film, and after drying the coating film, the dried coating film was rolled. This formed a positive electrode layer on both sides of the positive electrode current collector. In the positive electrode of Example 1, an exposed portion of the positive electrode current collector (an area where the positive electrode layer is not placed) was provided at one location that crosses the width direction of the strip-shaped positive electrode current collector. In other words, in the positive electrode of Example 1, one exposed portion of the positive electrode current collector was provided so as to include both ends in the width direction of the strip-shaped positive electrode current collector.

[0103] In the positive electrode according to Example 1, the density of the positive electrode mixture layer is 3.5 g / cm³. ３ Furthermore, a strip of aluminum foil with a tensile strength A of 3.84 N / m and a breaking elongation B of 2.4% was used for the positive electrode current collector. Therefore, in the positive electrode current collector of Example 1, the product of tensile strength A and breaking elongation B (A × B) was 9.2 N / m·%. Also, in Example 1, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.84. The tensile strength A and the elongation B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0104] (3) Preparation of non-aqueous electrolytes LiPF ６ A non-aqueous electrolyte was obtained by dissolving [the substance]. As the non-aqueous solvent, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was used, with EC:DEC = 3:7 by volume. In addition, LiPF in the non-aqueous electrolyte ６ The concentration was set to 1.0 mol / L.

[0105] (4) Fabrication of a non-aqueous electrolyte secondary battery An Al positive electrode tab was attached to the strip-shaped positive electrode obtained as described above. One end of the positive electrode tab was connected to the exposed portion of the positive electrode current collector located at one end of the strip-shaped positive electrode current collector in the width direction. An Al negative electrode tab was attached to the strip-shaped negative electrode obtained as described above. One end of the negative electrode tab was connected to the end in the length direction of the strip. Next, the strip-shaped positive electrode and the strip-shaped negative electrode were wound in a spiral shape via a strip-shaped separator to fabricate a wound electrode group. A polyethylene thin film was used as the strip-shaped separator.

[0106] Next, the electrode group was housed in a bottomed cylindrical case body (outer casing), and the other end of the negative electrode tab was welded to the inner bottom surface of the case body. The other end of the positive electrode tab was welded to the internal terminal plate of the sealing body. Then, a non-aqueous electrolyte was injected into the case body, and the opening of the case body was sealed using the sealing body and gasket. This completed the fabrication of the non-aqueous electrolyte secondary battery according to Example 1.

[0107] (Example 2) A non-aqueous electrolyte secondary battery according to Example 2 was manufactured in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 3.71 N / m and an elongation at break B of 2.4% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector in Example 2 was 8.9 N / m・%. In Example 2, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.78. In Example 2 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0108] (Example 3) A non-aqueous electrolyte secondary battery according to Example 3 was manufactured in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 3.56 N / m and an elongation at break B of 2.4% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector in Example 3 was 8.5 N / m・%. In Example 3, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.70. In Example 3 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0109] (Comparative Example 1) A non-aqueous electrolyte secondary battery according to Comparative Example 1 was prepared in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 2.63 N / m and an elongation at break B of 3.0% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector of Comparative Example 1 was 7.9 N / m・%. In Comparative Example 1, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.26. In Comparative Example 1 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the Embodiments section above.

[0110] (Comparative Example 2) A non-aqueous electrolyte secondary battery according to Comparative Example 2 was prepared in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 3.98 N / m and an elongation at break B of 2.1% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector of Comparative Example 2 was 8.4 N / m・%. In Comparative Example 2, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.90. In Comparative Example 2 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0111] (Comparative Example 3) A non-aqueous electrolyte secondary battery according to Comparative Example 3 was prepared in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 3.98 N / m and an elongation at break B of 2.4% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector of Comparative Example 3 was 9.6 N / m・%. In Comparative Example 3, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.90. In Comparative Example 3 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0112] (Comparative Example 4) A non-aqueous electrolyte secondary battery according to Comparative Example 4 was prepared in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 4.05 N / m and an elongation at break B of 1.9% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector of Comparative Example 4 was 7.7 N / m・%. In Comparative Example 4, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.94. In Comparative Example 4 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0113] (Comparative Example 5) A non-aqueous electrolyte secondary battery according to Comparative Example 5 was prepared in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 3.59 N / m and an elongation at break B of 1.9% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector of Comparative Example 5 was 6.8 N / m・%. In Comparative Example 5, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.72. In Comparative Example 5 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0114] (Comparative Example 6) A non-aqueous electrolyte secondary battery according to Comparative Example 6 was prepared in the same manner as in Example 1, except that a strip of aluminum foil with a tensile strength A of 3.12 N / m and an elongation at break B of 1.9% was used as the positive electrode current collector in (2) above. Therefore, the product of the tensile strength A and the elongation at break B (A × B) of the positive electrode current collector of Comparative Example 6 was 5.9 N / m・%. In Comparative Example 6, the ratio of the tensile strength A of the strip of positive electrode current collector to the tensile strength C of the strip of negative electrode current collector (A / C) was 1.49. In Comparative Example 6 as well, the tensile strength A and the elongation at break B of the strip of aluminum foil were measured according to the method described in the above embodiment section.

[0115] Table 1 below shows the values ​​for each example (Examples 1-3 and Comparative Examples 1-6), including the tensile strength A (N / m) of the positive electrode current collector, the elongation at break B (%) of the positive electrode current collector, the tensile strength C (N / m) of the negative electrode current collector, the product of tensile strength A and elongation at break B (A × B, in units of N / m·%), and the ratio of tensile strength A to tensile strength C (A / C).

[0116]

[0117] [Evaluation] <Cycle Maintenance Rate> For each example (Examples 1-3 and Comparative Examples 1-6), the non-aqueous electrolyte secondary batteries were subjected to the following charge-discharge tests. First, constant current charging was performed at a 3-hour rate current (0.33C) under normal temperature conditions (25±2℃) until the battery voltage reached 4.2V. Next, constant voltage charging was performed with a termination current of a 50-hour rate current (0.02C) at a battery voltage of 4.2V. Next, constant current discharge was performed at a 3-hour rate current until the battery voltage reached 3V. Then, the above charge-discharge cycle was considered one cycle, and a total of 400 charge-discharge cycles were performed. Then, the capacity maintenance rate for each example's non-aqueous electrolyte secondary battery was calculated based on the following formula, and this was defined as the cycle maintenance rate. The results of calculating the cycle maintenance rate for each example's non-aqueous electrolyte secondary battery are shown in Table 2 below. ・Capacity maintenance rate (%) = {(Discharge capacity at 400th cycle) / (Discharge capacity at 1st cycle)} × 100

[0118] <Foil breakage of the positive electrode current collector> After evaluating the cycle maintenance rate, the non-aqueous electrolyte secondary batteries for each example were disassembled, and the electrode groups were removed from the bottomed cylindrical case body. Then, the strip-shaped positive electrodes were removed from each electrode group. For each example, the presence or absence of foil breakage was checked at the exposed portion of the positive electrode current collector to which the positive electrode tab is connected was checked. The presence or absence of foil breakage was checked visually. The results of the check for foil breakage of the positive electrode current collector are shown in Table 2 below.

[0119] <Safety> The non-aqueous electrolyte secondary batteries for each example were charged as described in the section on cycle maintenance rate above. Next, the charged non-aqueous electrolyte secondary batteries for each example were left in a room temperature environment (25±2℃) until the battery temperature (temperature of the case body) reached room temperature (25±2℃). Next, one end of a 15.8φ (15.8 mm diameter) round rod was brought into contact with the outer surface of the case body of the non-aqueous electrolyte secondary battery for each example, and a weight of 9.1 kg was dropped from a height of 61 cm onto the other end of the round rod. Then, the voltage and temperature behavior of the non-aqueous electrolyte secondary batteries for each example was examined. This safety test was performed on 10 non-aqueous electrolyte secondary batteries for each example, and those in which neither ignition nor overheating was confirmed were deemed to pass, and those in which at least one of ignition or overheating was confirmed were deemed to fail. The number of non-aqueous electrolyte secondary batteries that passed out of 10 was then determined. The results are shown in Table 2 below. In Table 2, "Z / 10" means that Z non-aqueous electrolyte secondary batteries out of 10 are in the passing category. For example, "10 / 10" means that all 10 non-aqueous electrolyte secondary batteries are in the passing category, and "7 / 10" means that 7 non-aqueous electrolyte secondary batteries out of 10 are in the passing category.

[0120]

[0121] Table 2 shows that in the non-aqueous electrolyte secondary batteries of each example (Examples 1 to 3), no foil breakage was observed in the positive electrode current collector, and both the cycle maintenance rate evaluation results and the safety evaluation results were good. On the other hand, in the non-aqueous electrolyte secondary battery of Comparative Example 1, although the cycle maintenance rate evaluation results and safety evaluation results were good, foil breakage was observed in the positive electrode current collector. Furthermore, in the non-aqueous electrolyte secondary batteries of Comparative Examples 2 to 4, no foil breakage was observed in the positive electrode current collector, and the safety evaluation results were good, but the cycle maintenance rate evaluation results were poor. In addition, in the non-aqueous electrolyte secondary batteries of Comparative Examples 5 and 6, no foil breakage was observed in the positive electrode current collector, and the cycle maintenance rate evaluation results were good, but the safety evaluation results were poor.

[0122] Furthermore, a good cycle maintenance rate evaluation means that the cycle maintenance rate exceeds 80%, and a good safety evaluation means that all 10 non-aqueous electrolyte secondary batteries meet the passing criteria.

[0123] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0124] The non-aqueous electrolyte secondary battery described herein can be used in applications where it is required to suppress breakage of the exposed portion of the positive electrode current collector, suppress a decrease in cycle maintenance rate, and improve safety.

[0125] 10: Non-aqueous electrolyte secondary battery, 11: Positive electrode, 12: Negative electrode, 13: Separator, 14: Electrode group

Claims

1. The electrode group comprises a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator wound in the longitudinal direction between the strip-shaped positive electrode and the strip-shaped negative electrode, and a non-aqueous electrolyte, wherein the strip-shaped positive electrode has a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the strip-shaped positive electrode current collector, the strip-shaped negative electrode has a strip-shaped negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the strip-shaped negative electrode current collector, at least one end of the strip-shaped positive electrode current collector in the width direction is provided with an exposed portion of the positive electrode current collector where the positive electrode mixture layer is not disposed, a positive electrode tab is connected to the exposed portion of the positive electrode current collector, and the tensile strength A (N / m) of the strip-shaped positive electrode current collector satisfies 2.7 N / m ≤ A ≤ 3.9 N / m. A non-aqueous electrolyte secondary battery in which the ratio (A / C) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector to the tensile strength C (N / m) of the strip-shaped negative electrode current collector satisfies 1.00 ≤ A / C ≤ 1.

86.

2. The anode mixture layer contains a silicon-containing material as an anode active material, and the content of the silicon-containing material in the anode mixture layer is 2% by mass or more, the non-aqueous electrolyte secondary battery according to claim 1.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the product (A × B) of the tensile strength A (N / m) of the strip-shaped positive electrode current collector and the elongation at break B (%) of the strip-shaped positive electrode current collector satisfies 7.5 N / m・% ≤ A × B.

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