Non-aqueous electrolyte secondary battery

Abstract

A non-aqueous electrolyte secondary battery according to the present invention comprises a receiving container having a positive electrode can, a gasket, and a negative electrode can, and a power generation element including an electrolyte. The positive electrode can is formed in a cylindrical shape with a bottom having a bottom wall portion and an outer wall portion. The negative electrode can is formed in a cylindrical shape with a top wall portion and an inner wall portion. The portion of the outer wall portion located on the top wall portion side is a caulking portion (12b) that is curved with a radius of curvature R toward the inner wall portion side as it extends from the bottom wall portion side toward the edge of the opening of the outer wall portion. The diameter of the non-aqueous electrolyte secondary battery is 4.6 mm to 5.0 mm. The height H2 of the positive electrode can is within the range of 74% to 79% of the height H1 of the non-aqueous electrolyte secondary battery. The radius of curvature R of the caulking portion is within the range of 0.7 mm to 1.1 mm.

Description

Technology Field

[0001] The present invention relates to a non-aqueous electrolyte secondary battery. Background Technology

[0002] A non-aqueous electrolyte secondary battery is a secondary battery that primarily comprises a positive electrode and a negative electrode constituting a pair of polarizable electrodes, a separator disposed between the positive and negative electrodes, and an electrolyte containing a supporting salt and a solvent, all contained within a sealed container. Due to its high energy density and lightweight nature, this type of non-aqueous electrolyte secondary battery is utilized, for example, in power supply units of electronic devices or in storage units that absorb fluctuations in the power generation of power generation devices.

[0003] In particular, a non-aqueous electrolyte secondary battery containing silicon oxide (SiOx) coated with carbon on its surface as a negative electrode active material is suitablely used as a small coin-type (button-type) non-aqueous electrolyte secondary battery because a high discharge capacity is obtained.

[0004] Coin-type non-aqueous electrolyte secondary batteries are known to have excellent charge-discharge characteristics with high voltage and high energy density, as well as long cycle life and high reliability. For this reason, coin-type non-aqueous electrolyte secondary batteries are suitablely utilized in various small electronic devices, such as mobile phones, PDAs, portable game consoles, and digital cameras, for example, as backup power sources for semiconductor memory or clock functions.

[0005] As such, a non-aqueous electrolyte secondary battery of this type is known to be able to be used while suppressing the volatilization of the electrolyte or the intrusion of moisture even in a high-temperature environment of, for example, around 80°C (for example, see Patent Document 1 below).

[0006] In this non-aqueous electrolyte secondary battery, the outer diameter is in the range of 4 to 12 mm and the height is in the range of 1 to 3 mm. By specifying the radius of curvature (R) of the curved surface of the positive electrode can during sealing (caulking) and the shoulder height (height of the positive electrode can H2 / height of the secondary battery H1), the formation of a gap between the positive electrode can or the negative electrode can and the gasket is suppressed. By doing so, the sealing performance is improved. As a result, it is possible to suppress the volatilization of the electrolyte and the intrusion of moisture into the battery. Prior art literature

[0007] Japanese Patent Publication No. 2015-159102 The problem to be solved

[0008] In coin-type non-aqueous electrolyte secondary batteries, as the outer diameter decreases, they become susceptible to effects such as the volatilization of the electrolyte under high-temperature environments or the intrusion of moisture into the battery. In this regard, along with the further miniaturization and thinning of various electronic devices, it is expected that coin-type non-aqueous electrolyte secondary batteries with an outer diameter of 4mm to 6mm will become mainstream in the future. Therefore, it is required to further improve the encapsulation properties of the battery.

[0009] Furthermore, in coin-type non-aqueous electrolyte secondary batteries, it is required to support reflow mounting to improve soldering efficiency during mounting. Even when reflow mounting (reflow soldering) is performed, it is important to suppress electrolyte leakage and continuously maintain the electrolyte within the battery to enable stable charging and discharging during long-term use or storage.

[0010] However, when reflow packaging is performed, for example, the peak temperature reaches about 260°C, and the battery is exposed to another high-temperature environment. Consequently, the internal pressure of the battery increases, and there is a risk that the battery shape will be deformed. Because of this, due to the deformation of the battery shape, a gap is likely to form between the positive or negative can and the gasket, making it easy for the electrolyte to volatilize or for moisture to enter the battery.

[0011] Therefore, even with the conventional non-aqueous electrolyte secondary battery described in Patent Document 1, if reflow mounting is assumed, it is prone to causing a decrease in the reliability of the battery, such as cycle characteristics and long-term storage, and the leakage rate is prone to increasing. Therefore, considering the reflow mounting, there was room for improvement.

[0012] The present invention has been made in consideration of these circumstances, and its purpose is to provide a compact non-aqueous electrolyte secondary battery that exhibits excellent leakage resistance even when exposed to high-temperature environments, as well as excellent cycle characteristics and long-term storage capabilities. means of solving the problem

[0013] (1) The non-aqueous electrolyte secondary battery according to the present invention comprises a receiving container having a positive electrode can and a negative electrode can that is caulked and fixed to the positive electrode can with a gasket interposed therebetween, and an electrolyte, and a power generation element contained within the receiving container. The positive electrode can is formed in a cylindrical shape with a bottom having a bottom wall portion and an outer wall portion formed along the outer edge of the bottom wall portion. The negative electrode can is formed in a cylindrical shape with a top wall portion and an inner wall portion formed along the outer edge of the top wall portion and disposed inside the outer wall portion. The portion of the outer wall portion located on the side of the top wall portion is a caulked portion that is curved with a radius of curvature R toward the inner wall portion as it extends from the side of the bottom wall portion toward the edge of the opening of the outer wall portion. The diameter D of the non-aqueous electrolyte secondary battery is 4.6 mm to 5.0 mm. The height H2 of the positive electrode can is within the range of 74% to 79% with respect to the height H1 of the non-aqueous electrolyte secondary battery. The radius of curvature R of the coking portion is within the range of 0.7mm to 1.1mm.

[0014] According to the non-aqueous electrolyte secondary battery of the present invention, the positive electrode can and the negative electrode can are fixed by caulking using a caulking portion in which the so-called shoulder height (H2 / H1) is defined within the range of 74% to 79% and the radius of curvature R is defined within the range of 0.7mm to 1.1mm, with a gasket interposed therein. Accordingly, the negative electrode can be fixed while firmly pressing it while compressing the gasket appropriately.

[0015] In addition, if the radius of curvature R of the caulking portion is smaller than 0.7 mm, the caulking portion is formed concentrated in the area around the opening edge on the outer wall. In this case, although the cathode can and gasket can be strongly pressed toward the bottom wall of the anode can, the force pressing the cathode can and gasket toward the center of the receiving container is weakened. Consequently, a gap is likely to form between the anode or cathode can and the gasket, raising concerns about leakage (including the volatilization of the electrolyte) or moisture intrusion. This leads to a deterioration in cycle characteristics and long-term storage performance.

[0016] Conversely, when the radius of curvature R of the caulking portion is greater than 1.1 mm, the caulking portion is formed over a wide area of ​​the outer wall. In this case, the force pressing the cathode can and gasket toward the center of the receiving container becomes stronger, but the force pressing the cathode can and gasket toward the bottom wall of the anode can becomes weaker. Therefore, even in this case, a gap is likely to form between the anode can or cathode can and the gasket, and the same problem as described above occurs.

[0017] In addition, if the shoulder height (H2 / H1) is less than 74%, stress becomes concentrated at the opening end of the inner wall of the cathode can during caulking (sealing). Consequently, the inner wall of the cathode can is prone to bulging deformation. This results in appearance defects and leads to product defects.

[0018] Conversely, if the shoulder height (H2 / H1) is greater than 79%, sufficient stress cannot be applied to the negative can during sealing, and a gap is created between the positive or negative can and the gasket, causing the aforementioned problem to occur.

[0019] In contrast, in the non-aqueous electrolyte secondary battery according to the present invention, the shoulder height (H2 / H1) is within the range of 74% to 79%, and the radius of curvature R of the coking portion is within the range of 0.7mm to 1.1mm. Therefore, the aforementioned problem is unlikely to occur, and it is possible to make a non-aqueous electrolyte secondary battery with excellent leakage resistance, cycle characteristics, and long-term storage capabilities. For this reason, even if miniaturization is achieved with a diameter D in the 4mm range (within the range of 4.6mm to 5.0mm), leakage resistance can be maintained. Furthermore, leakage resistance can be maintained even when used or stored in a high-temperature environment. Therefore, it is possible to make an easy-to-use non-aqueous electrolyte secondary battery with improved operational reliability.

[0020] (2) The radius of curvature R of the above-mentioned caulking part may be within the range of 0.8mm to 1.0mm.

[0021] In this case, the formation of a gap between the positive or negative can and the gasket can be effectively suppressed, making it more difficult for leakage or moisture intrusion to occur. Consequently, superior leakage resistance can be achieved, and the battery capacity can be maintained stably over a long period.

[0022] (3) The above power generation element has a positive electrode installed on the positive electrode can side and containing spinel-type lithium manganese oxide as a positive electrode active material, a negative electrode installed on the negative electrode can side and containing carbon-coated SiOx (0 < x < 2) as a negative electrode active material, and a separator disposed between the positive electrode and the negative electrode, and the electrolyte may include a mixed solvent containing ethylene carbonate (EC) and vinylene carbonate (VC) in a glame-based solvent.

[0023] In this case, a combination of a positive electrode active material containing spinel-type lithium manganese oxide and a negative electrode active material containing carbon-coated SiOx is combined with an electrolyte containing a mixed solvent containing ethylene carbonate (EC) and vinylene carbonate (VC) in a gla-lime solvent. Therefore, even if subjected to heating associated with reflow mounting (reflow soldering), there is little risk of the solvent vaporizing. Consequently, heat resistance capable of withstanding heating can be obtained, and the degradation of the positive electrode, negative electrode, and electrolyte can be suppressed. Furthermore, since there is little risk of the solvent vaporizing even if subjected to heating associated with reflow mounting, there is less risk of the internal pressure of the receiving vessel rising, making it possible to use a non-aqueous electrolyte secondary battery that is less prone to deformation of the receiving vessel.

[0024] Therefore, it can be made into a non-aqueous electrolyte secondary battery that can be reflow-mounted. In particular, even if the internal pressure increases due to exposure to a high-temperature environment, such as 260°C, when reflow-mounted, excellent leakage resistance is maintained as described above, so excellent cycle characteristics and long-term storage can be maintained even after reflow. Effects of the invention

[0025] According to the present invention, a small non-aqueous electrolyte secondary battery is provided that has excellent leakage resistance even when exposed to a high-temperature environment, and excellent cycle characteristics and long-term storage properties. Brief explanation of the drawing

[0026] FIG. 1 is a cross-sectional view showing an embodiment of a non-aqueous electrolyte secondary battery according to the present invention. Figure 2 is an enlarged cross-sectional view of the periphery of the caulking portion shown in Figure 1. Figure 3 is a diagram showing the relationship between the radius of curvature of the caulking section, the leakage rate, and the capacity retention rate. Figure 4 is a diagram showing the relationship between shoulder height (H2 / H1), leakage rate, and bulging deformation rate. Specific details for implementing the invention

[0027] Hereinafter, embodiments of a non-aqueous electrolyte secondary battery according to the present invention will be described with reference to the drawings. Furthermore, the non-aqueous electrolyte secondary battery of the present embodiment is a secondary battery configured such that an active material used as a positive or negative electrode and a separator are contained within a receiving container.

[0028] As shown in FIGS. 1 and 2, the non-aqueous electrolyte secondary battery (1) of the present embodiment is a so-called coin (button) type battery and mainly comprises a receiving container (2) and a power generation element (3) contained inside the receiving container (2).

[0029] The receiving container (2) mainly comprises an anode can (10) and a cathode can (20) fixed to the anode can (10) via a gasket (30). The anode can (10) and the cathode can (20) are fixed such that the lower wall portion (11) of the anode can (10), described later, and the upper wall portion (21) of the cathode can (20), described later, face each other.

[0030] In this embodiment, the axis line passing through the center of the bottom wall (11) and the top wall (21), and extending along the direction in which the bottom wall (11) and the top wall (21) face each other, is called the battery axis (O). Additionally, when viewed from a plane in the direction of the battery axis (O), the direction that intersects the battery axis (O) is called the radial direction, and the direction that circles around the battery axis (O) is called the main direction. Furthermore, along the battery axis (O), the direction from the bottom wall (11) toward the top wall (21) is called the upward direction, and the opposite direction is called the downward direction.

[0031] The power generation element (3) mainly comprises an anode (40) installed on the anode can (10) side, a cathode (50) installed on the cathode can (20) side, and a separator (60) disposed between the anode (40) and the cathode (50). The power generation element (3) includes an electrolyte (70) and is contained within a receiving space (S) formed inside a receiving container (2).

[0032] (Container)

[0033] The receiving container (2) is described in detail.

[0034] The receiving container (2) mainly comprises a metal positive can (10) formed in a cylindrical shape with a bottom, and a metal negative can (20) formed in a cylindrical shape with a top and fixed to the positive can (10) by caulking with a gasket (30).

[0035] The material of the anode can (10) is not limited to a specific material, but examples include SUS316L or SUS329J4L. In addition, conventionally known stainless steel may be used as the material of the anode can (10). Furthermore, metal materials other than stainless steel may be used for the anode can (10).

[0036] The material of the cathode can (20) is not limited to a specific material, but, for example, SUS316L, SUS329J4L, etc., can be used, just like the material of the anode can (10). In addition, for the material of the cathode can (20), SUS304-BA, etc., or other conventionally known stainless steels may be used. Furthermore, metal materials other than stainless steel may be used for the cathode can (20). For example, a clad material formed by pressing copper, nickel, etc., onto stainless steel may be used for the cathode can (20).

[0037] (Positive can)

[0038] The positive electrode can (10) is formed in a cylindrical shape having a bottom, which has a circular bottom wall (11) formed when viewed from a flat surface, and an annular outer wall (12) formed along the main direction of the bottom wall (11) and extended upward along the outer edge of the bottom wall (11).

[0039] The lower wall portion (12a), which is continuously installed at the outer edge of the lower wall portion (11) among the outer wall portions (12), is the portion that becomes the maximum outer diameter of the non-aqueous electrolyte secondary battery (1). Accordingly, the outer diameter of the lower wall portion (12a) corresponds to the diameter D of the non-aqueous electrolyte secondary battery (1).

[0040] In this embodiment, the positive electrode can (10) is formed such that the diameter D is within the range of 4.6 mm to 5.0 mm.

[0041] The upper wall portion located on the positive wall side of the negative can (20) among the outer wall portions (12) is formed as a caulking portion (12b) that is curved inward in the radial direction (toward the inner wall portion (22) side of the negative can (20)) from the bottom wall portion (11) side toward the edge of the opening end of the outer wall portion (12) with a radius of curvature R.

[0042] In this embodiment, the caulking portion (12b) is formed such that the radius of curvature R is within the range of 0.7mm to 1.1mm.

[0043] In the illustrated example, the radius of curvature of the outer surface of the caulking portion (12b) is set to R. However, it is acceptable to set the radius of curvature of the inner surface of the caulking portion (12b) or the unillustrated neutral line of the caulking portion (12b) (a part that does not receive tensile or compressive stress even when the caulking portion (12b) is bent) to R.

[0044] In addition, in the shear layer where caulking is performed, the entire outer wall portion (12), including the caulking portion (12b), is formed in a cylindrical shape that extends along the battery axis (O) and is open upward. Then, when sealing (caulking), by applying stress to the caulking portion (12b), the caulking portion (12b) is formed to curve inward in the radial direction with the radius of curvature R. The negative electrode can (20) is firmly caulked and fixed through the gasket (30) by caulking by the caulking portion (12b) facing inward in the radial direction.

[0045] Additionally, as shown in FIG. 2, the total height of the outer wall portion (12) along the battery axis (O) after coking corresponds to the height H2 of the positive electrode can (10). In this embodiment, the relationship between the positive electrode can (10) and the negative electrode can (20) is defined such that the height H2 of the positive electrode can (10) is within the range of 74% to 79% of the height H1 of the non-aqueous electrolyte secondary battery (1). This point will be explained again later.

[0046] (Cathode can)

[0047] As shown in FIGS. 1 and 2, the cathode can (20) is formed in a cylindrical shape having a ceiling, a circular inner wall (22) formed along the main direction of the circular wall (21) when viewed in a planar view, and an annular inner wall (22) extending downward along the outer edge of the circular wall (21).

[0048] The cathode can (20) is assembled from above with respect to the anode can (10) such that the inner wall portion (22) fits inside the outer wall portion (12), and then fixed by caulking with a gasket (30) interposed, thereby being integrally assembled with the anode can (10). Accordingly, the cathode can (20) is assembled in a state where it is precisely positioned with respect to the anode can (10) by the gasket (30).

[0049] The positive wall portion (21) is positioned above the coking portion (12b) of the outer wall portion (12) of the positive can (10). At this time, the height along the battery axis (O) between the lower surface of the bottom wall portion (11) of the positive can (10) and the upper surface (top surface) of the positive wall portion (21) of the negative can (20) is the total height H1 of the non-aqueous electrolyte secondary battery (1).

[0050] In this embodiment, the positive electrode can (10) and the negative electrode can (20) are combined so that the total height H1 of the non-aqueous electrolyte secondary battery (1) after coking is within the range of 1.0 mm to 3.0 mm. At this time, the positive electrode can (10) and the negative electrode can (20) are combined so that the height H2 of the positive electrode can (10) is within the range of 74% to 79% of the height H1 of the non-aqueous electrolyte secondary battery (1).

[0051] In addition, regarding the height H2 of the positive can (10), if the so-called shoulder height (H2 / H1) falls within the range of 74% to 79%, it may be selected arbitrarily.

[0052] The inner wall portion (22) is formed to extend downward from the outer edge of the positive wall portion (21), and the lower portion (22a) is positioned above the bottom wall portion (11) of the positive can (10) with the gasket (30) in between.

[0053] In the illustrated example, the inner wall portion (22) is formed in a two-stage cylindrical shape that is expanded from the top to the bottom. However, it is not limited to two stages, and for example, the inner wall portion (22) may be formed in a multi-stage cylindrical shape that is expanded in stages of three or more stages from the top to the bottom.

[0054] In addition, in the illustrated example, the inner wall portion (22) is bent upward from the lower portion (22a), and an annular bend portion (23) that overlaps from the outer side in the radial direction with respect to the inner wall portion (22) is integrally formed. Accordingly, the outer diameter of this bend portion (23) is the part that becomes the maximum outer diameter as a cathode can (20). Also, the outer diameter of the bend portion (23) is smaller than the inner diameter of the lower wall portion (12a) in the outer wall portion (12). Also, the bend portion (23) is not essential and may not be provided.

[0055] In the cathode can (20) configured as described above, the caulking portion (12b) of the anode can (10) is bent by caulking so as to be positioned above the bending portion (23). Accordingly, the cathode can (20) is reliably prevented from falling upward by interposing a gasket (30).

[0056] (Gasket)

[0057] The gasket (30) is formed in a double annular shape to surround the inner wall portion (22) of the cathode can (20) along the entire circumference from the outer side in the radial direction and the inner side in the radial direction.

[0058] The gasket (30) is provided with an annular outer gasket portion (31) disposed between the outer wall portion (12) of the positive electrode can (10) and the inner wall portion (22) of the negative electrode can (20), an annular inner gasket portion (32) disposed inside the inner wall portion (22) of the negative electrode can (20), and an annular flange portion (33) connecting the lower end of the outer gasket portion (31) and the lower end of the inner gasket portion (32) in the radial direction.

[0059] The outer gasket portion (31) is positioned in a predetermined compressed state between the outer wall portion (12) and the inner wall portion (22) by caulking by the caulking portion (12b). The outer gasket portion (31) is fitted tightly without gaps to the inner surface of the outer wall portion (12) and the outer surface of the inner wall portion (22), respectively. The flange portion (33) is positioned in a predetermined compressed state between the lower portion (22a) of the inner wall portion (22) and the bottom wall portion (11) by caulking by the caulking portion (12b). The flange portion (33) is fitted tightly without gaps to the lower portion (22a) of the inner wall portion (22) and the bottom wall portion (11), respectively. The inner gasket portion (32) is tightly fitted without gaps to the inner surface of the inner wall portion (22) by caulking by the caulking portion (12b).

[0060] Accordingly, the gasket (30) is firmly fitted between the positive electrode can (10) and the negative electrode can (20) by caulking by the caulking part (12b). In addition, the gasket (30) integrally combines the positive electrode can (10) and the negative electrode can (20) while forming a sealed receiving space (S) between the positive electrode can (10) and the negative electrode can (20).

[0061] Additionally, the receiving space (S) is a space surrounded by the bottom wall (11) of the positive can (10), the top wall (21) of the negative can (20), and the inner gasket (32).

[0062] The above-described gasket (30) is preferably made of a resin with a heat deformation temperature of, for example, 230°C or higher. If the heat deformation temperature of the resin material used for the gasket (30) is 230°C or higher, it is possible to suppress the problem of the gasket (30) being significantly deformed and the electrolyte (70) leaking due to reflow soldering or heating during use of the non-aqueous electrolyte secondary battery (1).

[0063] Examples of materials for this type of gasket (30) include polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyamide, liquid crystal polymer (LCP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), polyetheretherketone resin (PEEK), polyethernitrile resin (PEN), polyetherketone resin (PEK), polyarylate resin, polybutylene terephthalate resin (PBT), polycyclohexanedimethylene terephthalate resin, polyethersulfone resin (PES), polyaminobismaleimide resin, polyetherimide resin, fluorine resin, etc.

[0064] Among these, if either PPS or PEEK is used, it is possible to suppress significant deformation of the gasket (30) during use or storage in a high-temperature environment, which is desirable from the perspective of further improving the encapsulation properties of the non-aqueous electrolyte secondary battery (1).

[0065] In addition, glass fiber, mica whiskers, ceramic fine powder, etc., can be added to the above-described material in an amount of 30 mass% or less, and this can be suitablely used for the gasket (30). By using such a material, the problem of the gasket (30) being significantly deformed by heating during reflow and the electrolyte (70) leaking can be suppressed.

[0066] In the receiving container (2) configured as described above, as explained above, it is configured to satisfy all arrangement and dimensional relationships of (1) to (3) shown below.

[0067] (1) The diameter D of the non-aqueous electrolyte secondary battery (1) is within the range of 4.6 mm to 5.0 mm.

[0068] (2) The radius of curvature R of the coking portion (12b) in the positive can (10) is within the range of 0.7mm to 1.1mm.

[0069] (3) Shoulder height (H2 / H1), i.e., height H2 of the positive can (10) is within the range of 74% to 79% of the height H1 of the non-aqueous electrolyte secondary battery (1).

[0070] In addition, the thickness of the metal plate used for the positive electrode can (10) and the negative electrode can (20) is generally about 0.1 to 0.3 mm, and for example, the average thickness of the entire positive electrode can (10) or negative electrode can (20) is about 0.15 mm.

[0071] (Development Factors)

[0072] Next, the development element (3) is explained in detail.

[0073] As previously described, the power generation element (3) mainly comprises an anode (40), a cathode (50), and a separator (60), and is contained in a receiving space (S) in a receiving container (2) together with an electrolyte (70).

[0074] The positive electrode (40) installed on the positive electrode can (10) side and the negative electrode (50) installed on the negative electrode can (20) side are arranged facing each other in the direction of the battery axis (O) with a separator (60) interposed, and are placed within the receiving space (S). Additionally, the positive electrode (40), the negative electrode (50), and the separator (60) are impregnated with an electrolyte (70) filled in a receiving container.

[0075] The positive electrode (40) is electrically connected to the upper surface of the bottom wall (11) of the positive electrode can (10) via a positive electrode current collector (41). In contrast, the negative electrode (50) is electrically connected to the lower surface of the top wall (21) of the negative electrode can (20) via a negative electrode current collector (51).

[0076] However, this is not limited to this case. For example, the positive electrode current collector (41) and the negative electrode current collector (51) may be omitted, and the positive electrode (40) may be directly connected to the positive electrode can (10) to have the function of a current collector in the positive electrode can (10), and the negative electrode (50) may be directly connected to the negative electrode can (20) to have the function of a current collector in the negative electrode can (20).

[0077] Additionally, the separator (60) is held by the gasket (30) by the outer edge of the separator (60) coming into contact with the gasket (30) inside the receiving container (2).

[0078] (anode)

[0079] In the positive electrode (40), the type of positive electrode active material is not particularly limited, but for example, it is preferable to use a positive electrode active material containing spinel-type lithium manganese oxide.

[0080] The content of the positive active material in the positive electrode (40) is determined by taking into account the discharge capacity required for the non-aqueous electrolyte secondary battery (1), and, for example, can be in the range of 50 to 95 mass%. If the content of the positive active material is greater than or equal to the lower limit of the above-mentioned preferred range, a sufficient discharge capacity is easily obtained, and if it is less than or equal to the preferred upper limit, the positive electrode (40) is easy to form.

[0081] The anode (40) may contain a conductive agent (hereinafter, the conductive agent used in the anode (40) may be referred to as the “anode conductive agent”).

[0082] Examples of carbonaceous materials that can be used as anode conductive agents include furnace black, Ketjen black, acetylene black, and graphite.

[0083] The anode conductive agent may be used as a single type of the above, or two or more types may be used in combination.

[0084] The anode (40) may contain a binder (hereinafter, the binder used in the anode (40) may be referred to as the “anode binder”).

[0085] As a positive electrode binder of this type, conventional known materials may be used, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), etc., and a binder composed of a combination of these may be used.

[0086] In addition, the anode binder may be used alone or in combination of two or more types. The content of the anode binder in the anode (40) can be, for example, 1 to 20 mass%.

[0087] In addition, when upper and lower limits are indicated for numerical ranges using "~" in this specification, the range shall include the upper and lower limits unless specifically explained otherwise. Accordingly, for example, when stated as 1 to 20 mass%, it means 1 mass% or more and 20 mass% or less.

[0088] As for the positive current collector (41), a conventional known one may be used, such as a conductive resin adhesive in which carbon is used as a conductive filler.

[0089] In addition, in this embodiment, as a positive electrode active material, in addition to the above-mentioned lithium manganese oxide, other positive electrode active materials may be included, and may include one or more of other oxides such as molybdenum oxide, lithium iron phosphate compound, lithium cobalt oxide, lithium nickel oxide, vanadium oxide, etc.

[0090] (cathode)

[0091] In the case of the cathode (50), the type of cathode active material is not particularly limited, but for example, it is preferable to contain silicon oxide as the cathode active material.

[0092] In the case of the cathode (50), it is preferable that the cathode active material be carbon-coated SiOx, for example, silicon oxide represented as SiOx (0 < x < 2) coated with carbon.

[0093] In addition, the cathode (50) may contain other cathode active materials in addition to the above SiOx (0 < x < 2) as a cathode active material, and may contain other cathode active materials such as Si, C, etc.

[0094] When granular SiOx (0 < x < 2) is used as the negative electrode active material, the particle diameter (D50) is not particularly limited, but for example, a range of 0.1 to 30 μm can be selected, and more preferably a range of 1 to 10 μm can be selected.

[0095] If the particle diameter (D50) of SiOx is less than the lower limit of the above range, for example, when the non-aqueous electrolyte secondary battery (1) is stored and used in a harsh high-temperature and high-humidity environment, or when reactivity increases due to reflow soldering, there is a risk that the battery characteristics may be damaged. In addition, if the particle diameter (D50) of SiOx exceeds the upper limit of the above range, there is a risk that the discharge rate may decrease.

[0096] The content of the negative electrode active material, namely SiOx (0 < x < 2), in the negative electrode (50) is determined by taking into account the discharge capacity required for the non-aqueous electrolyte secondary battery (1), and a range of 50 mass% or more can be selected, and it is preferable to select a range of 60 to 80 mass%.

[0097] In the case of the cathode (50), if the content of the cathode active material made of the above element is greater than or equal to the lower limit of the above range, a sufficient discharge capacity is easily obtained, and if it is less than or equal to the upper limit, the cathode (50) is easy to form.

[0098] The cathode (50) may contain a conductive agent (hereinafter, the conductive agent used in the cathode (50) may be referred to as a “cathode conductive agent”). For example, the cathode conductive agent may be the same as the anode conductive agent.

[0099] The cathode (50) may contain a binder (hereinafter, the binder used in the cathode (50) may be referred to as a “cathode binder”).

[0100] As a cathode binder of this type, for example, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethylcellulose (CMC), polyimide (PI), polyamideimide (PAI), etc. can be selected.

[0101] The cathode binder may be used as a single type of the above, or two or more types may be used in combination.

[0102] In addition, when polyacrylic acid is used as the cathode binder, the polyacrylic acid can be adjusted to a pH of 3 to 10 in advance. In this case, for adjusting the pH, alkali metal hydroxides such as lithium hydroxide or alkaline earth metal hydroxides such as magnesium hydroxide can be used.

[0103] The content of the cathode binder in the cathode (50) is, for example, in the range of 1 to 20 mass%.

[0104] In addition, in this embodiment, the size and thickness of the negative electrode (50) can be formed to be the same as the size and thickness of the positive electrode (40).

[0105] Additionally, a configuration may be adopted in which a lithium body (80), such as a lithium foil, is installed on the surface of the cathode (50), that is, between the cathode (50) and the separator (60), as shown in the drawing. However, the lithium body (80) is not essential and may not be provided.

[0106] (Separator)

[0107] The separator (60) is interposed between the positive electrode (40) and the negative electrode (50), and an insulating film having high ion permeability and also mechanical strength is used.

[0108] As for the separator (60), any material conventionally used as a separator for a non-aqueous electrolyte secondary battery can be applied without any limitation, such as glass such as alkali glass, borosilicate glass, quartz glass, lead glass, etc., and nonwoven fabric made of resin such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyethylene terephthalate (PET), polyamideimide (PAI), polyamide, polyimide (PI).

[0109] Among the above, a glass nonwoven fabric is preferred as the separator (60), and a borosilicate glass nonwoven fabric is more preferred. Since the glass nonwoven fabric has excellent mechanical strength and high ion permeability, it can reduce internal resistance and improve discharge capacity.

[0110] In addition, the thickness of the separator (60) is determined by taking into account the size of the non-aqueous electrolyte secondary battery (1) or the material of the separator (60), and can be, for example, 5 to 300 μm.

[0111] (Electrolyte)

[0112] The electrolyte (70) is typically a liquid in which a supporting salt is dissolved in a non-aqueous solvent.

[0113] In this embodiment, the non-aqueous solvent forming the electrolyte (70) may use a mixed solvent in which tetraglam (TEG) is the main solvent, diethoxyethane (DEE) is the auxiliary solvent, and ethylene carbonate (EC) and vinylene carbonate (VC) are added as additives.

[0114] The non-aqueous solvent is typically determined by taking into account the heat resistance and viscosity required for the electrolyte (70), but in this embodiment, the solvent composed of each of the above is used. In addition, the main solvent for constituting the glyme-based solvent may be tetraglyme, triglyme, pentaglyme, deglyme, etc.

[0115] In this embodiment, an electrolyte (70) using a non-aqueous solvent containing tetraglam (TEG), diethoxyethane (DEE), and ethylene carbonate (EC) may be used. By adopting this composition, DEE and TEG are solvated into the Li ions forming the support salt.

[0116] At this time, since DEE has a higher donor number than TEG, DEE is selectively solvated with Li ions. In this way, DEE and TEG are solvated with the Li ions forming the support salt, thereby protecting the Li ions. As a result, even if moisture enters the interior of the non-aqueous electrolyte secondary battery (1) under high temperature and high humidity conditions, the reaction between the moisture and Li can be prevented, and the decrease in discharge capacity is suppressed, thereby obtaining the effect of improving storage stability.

[0117] The ratio of each solvent in the non-aqueous solvent in the electrolyte (70) is not particularly limited, but for example, TEG: 30 mass% or more and 48.5 mass% or less (30~48.5%), DEE: 30 mass% or more and 48.5 mass% or less (30~48.5%), EC: 0.5 mass% or more and 10 mass% or less (0.5~10%), VC: 2 mass% or more and 13 mass% or less (2~13%), can be selected in the range (total 100%).

[0118] When the ratio of TEG, DEE, and EC contained in the non-aqueous solvent is within the above range, the effect of protecting the Li ion is obtained by the aforementioned DEE being solvated by the Li ion.

[0119] Even within the above-described range, regarding the VC content, a range of 2.5 mass% or more and 10 mass% or less (2.5~10%) is preferred, and a range of 5.0 mass% or more and 7.5 mass% (5.0~7.5%) is more preferred. Regarding the upper limit of the TEG and DEE content, 48.25 mass% or less is preferred, and 48 mass% or less is more preferred.

[0120] When the VC content is in the range of 2 mass% or more and 13 mass% or less, even if heated during reflow soldering, the change in thickness occurring in the receiving container (2) composed of the positive electrode can (10) and the negative electrode can (20) is small, so the increase in internal resistance can be reduced. Also, when the VC content is in the range of 2.5 mass% or more and 10.0 mass% or less, even if heated during reflow soldering, the change in thickness occurring in the receiving container (2) can be reduced even more, so the increase in internal resistance can be reduced even more. Even within these ranges, a range of 5.0 mass% or more and 7.5 mass% or less for the VC content is most preferable.

[0121] The support salt may be a known Li compound used as a support salt in the electrolyte of a non-aqueous electrolyte secondary battery, and examples include lithium salts of organic acids such as LiCH3SO3, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiN(CF3SO3)2, LiN(FSO2)2, etc.; lithium salts such as lithium salts of inorganic acids such as LiPF6, LiBF4, LiB(C6H5)4, LiCl, LiBr, etc.

[0122] Among the above, lithium salts that are compounds having lithium ion conductivity are preferred, LiN(CF3SO2)2, LiN(FSO2)2, and LiBF4 are more preferred, and LiN(CF3SO2)2 is particularly preferred from the perspective of having low heat resistance and reactivity with moisture and being able to sufficiently exhibit preservation characteristics.

[0123] In addition, the supporting salt may be used alone or in combination of two or more types.

[0124] The content of the supporting salt in the electrolyte (70) can be determined by taking into account the type of supporting salt, for example, 0.1 to 3.5 mol / L is preferred, 0.5 to 3 mol / L is more preferred, and 1 to 2.5 mol / L is particularly preferred.

[0125] If the concentration of the supporting salt in the electrolyte (70) is too high or too low, the conductivity decreases, and there is a risk of adverse effects on the battery characteristics.

[0126] (Operation of non-aqueous electrolyte secondary batteries)

[0127] According to the non-aqueous electrolyte secondary battery (1) configured as described above, the non-aqueous solvent comprises tetraglame (TEG) and diethoxyethane (DEE) as the main components, and the electrolyte (70) comprises ethylene carbonate (EC) and vinylene carbonate (VC) in appropriate amounts.

[0128] Therefore, heat resistance capable of withstanding heating during reflow mounting (reflow soldering) can be obtained, and even if subjected to heating associated with reflow mounting, there is little risk of the solvent vaporizing. Thus, in addition to obtaining heat resistance capable of withstanding heating, the deterioration of the anode (40), cathode (50), and electrolyte (70) can be suppressed. Furthermore, since there is little risk of the solvent vaporizing even if subjected to heating associated with reflow mounting, there is little risk of the internal pressure of the receiving container (2) rising, so it can be made into a non-aqueous electrolyte secondary battery (1) that is unlikely to cause deformation in the receiving container (2).

[0129] In addition, if the solvent is a glyme-based solvent containing tetraglyme (TEG) and diethoxyethane (DEE) as the main components, the heat resistance of the electrolyte (70) can be increased due to the high boiling point of these solvents.

[0130] With this, a non-water electrolyte secondary battery (1) corresponding to the reflow circuit can be made.

[0131] In addition, according to the non-aqueous electrolyte secondary battery (1) of the present embodiment, the so-called shoulder height (H2 / H1) is defined within the range of 74% to 79%, and the radius of curvature R is defined within the range of 0.7mm to 1.1mm, and the positive electrode can (10) and the negative electrode can (20) are fixed by caulking using a gasket (30). Thus, the negative electrode can (20) can be fixed while firmly pressing it while compressing the gasket (30) appropriately.

[0132] In addition, if a non-aqueous electrolyte secondary battery (1) is subjected to heating equivalent to reflow soldering, and some of the solvent constituting the electrolyte (70) vaporizes, causing the internal pressure of the receiving container (2) to rise, there is a possibility that deformation may occur in the receiving container (2) due to the rise in internal pressure. In this case, the sealing structure of the receiving container (2) may change along with the deformation, and there is a risk that, for example, a path may be formed for the electrolyte (70) to leak out of the receiving container (2).

[0133] In this case, if the radius of curvature R of the caulking portion (12b) is smaller than 0.7 mm, the caulking portion (12b) is formed concentrated in the area around the opening end of the outer wall portion (12). In this case, the negative electrode can (20) and the gasket (30) can be strongly pressed toward the bottom wall portion (11) of the positive electrode can (10), but the force pressing the negative electrode can (20) and the gasket (30) toward the center of the receiving container (2) is weakened.

[0134] Therefore, a gap is likely to form between the positive electrode can (10) or the negative electrode can (20) and the gasket (30), and there is a risk that a path may be formed for the electrolyte (70) to leak out of the receiving container (2) when subjected to heating equivalent to reflow. Consequently, there is a possibility of leakage (including volatilization of the electrolyte (70)) or moisture intrusion, which leads to a decrease in cycle characteristics or long-term storage performance.

[0135] Conversely, when the radius of curvature R of the caulking portion (12b) is greater than 1.1 mm, the caulking portion (12b) is formed over a wide area of ​​the outer wall portion (12). In this case, the force pressing the cathode can (20) and gasket (30) toward the center of the receiving container (2) becomes stronger, but the force pressing the cathode can (20) and gasket (30) toward the bottom wall portion (11) of the anode can (10) becomes weaker. Therefore, even in this case, a gap is likely to form between the anode can (10) or cathode can (20) and the gasket (30), and the same problem as described above occurs.

[0136] In addition, if the shoulder height (H2 / H1) is less than 74%, stress is concentrated on the lower part (22a) of the inner wall (22) of the cathode can (20) during sealing (caulking). Consequently, the positive wall (21) of the cathode can (20) is prone to bulging upward, causing deformation. This results in an appearance defect, which leads to product defects.

[0137] Conversely, if the shoulder height (H2 / H1) is greater than 79%, sufficient stress cannot be applied to the negative can (20) during sealing, so a gap is created between the positive can (10) or negative can (20) and the gasket (30), and the problem described above occurs.

[0138] In contrast, in the non-aqueous electrolyte secondary battery (1) of the present embodiment, the shoulder height (H2 / H1) is within the range of 74% to 79%, and the radius of curvature R of the coking portion (12b) is within the range of 0.7mm to 1.1mm. Therefore, the various problems described above are less likely to occur, and the non-aqueous electrolyte secondary battery (1) can be made to have excellent leakage resistance, excellent cycle characteristics, and excellent long-term storage capabilities.

[0139] Therefore, even if miniaturization is pursued with a diameter D in the 4mm range (within the range of 4.6mm to 5.0mm), leakage resistance can be maintained. Thus, it can be made into an easy-to-use non-aqueous electrolyte secondary battery (1) with improved operational reliability.

[0140] In addition, even if the internal pressure increases due to exposure to a high-temperature environment reaching, for example, 260°C during reflow mounting, excellent leakage resistance as described above allows for the maintenance of excellent cycle characteristics and long-term storage capabilities even after reflow.

[0141] Thus, a small non-aqueous electrolyte secondary battery (1) can be made that is reflowable, has excellent leakage resistance even when exposed to a high-temperature environment, and has excellent cycle characteristics and long-term storage capabilities.

[0142] In addition, it is preferable to have the radius of curvature R of the caulking portion (12b) within the range of 0.8 mm to 1.0 mm. In this case, the formation of a gap between the positive electrode can (10) or the negative electrode can (20) and the gasket (30) can be effectively suppressed, making it more difficult for leakage or moisture intrusion to occur. Therefore, it is possible to exhibit even better leakage resistance and maintain the battery capacity stably over a long period of time.

[0143] Examples

[0144] Next, regarding the non-aqueous electrolyte secondary battery according to the present invention, a non-aqueous electrolyte secondary battery (1) with the configuration shown in FIG. 1 and FIG. 2 was actually fabricated and then an evaluation test was performed as described below to confirm the above-described effects.

[0145] In conducting this evaluation test, a non-aqueous electrolyte secondary battery (1) was fabricated under the following requirements.

[0146] For the first time, as the anode (40), commercially available lithium manganese oxide (Li1 . 14 Co0. 06 Mn1 . 80 In O4), graphite was mixed as a conductive agent and polyacrylic acid as a binder in the following proportions to form an anode composite.

[0147] · Ratio "Lithium manganese oxide:graphite:polyacrylic acid = 95:4:1 (mass ratio)"

[0148] And, 16.4 mg of the aforementioned anode mixture, at 2 ton / cm 2 By applying pressure with the pressure, it was pressure-molded into disc-shaped pellets with a diameter of 2.8 mm.

[0149] Next, the obtained pellet (anode (40)) was bonded to the inner surface of an anode can (10) made of stainless steel (SUS329J4L: thickness t=0.20mm) using a conductive resin adhesive containing carbon, and the two were integrated to obtain an anode unit. Next, the anode unit was heated and dried under reduced pressure in the atmosphere at 120°C for 11 hours. Next, a sealant was applied to the inner surface of the outer wall (12) of the anode can (10) in the anode unit.

[0150] Next, as a cathode (50), SiO powder with carbon (C) formed over its entire surface was prepared and used as a cathode active material. Then, graphite was mixed with the cathode active material as a conductive agent and polyacrylic acid as a binder in the following proportions to form a cathode composite.

[0151] · Ratio "SiO powder:graphite:polyacrylic acid = 75:20:5 (mass ratio)"

[0152] And, 3.1 mg of the aforementioned cathode mixture, 2 ton / cm² 2 By applying pressure, it was pressure-molded into disc-shaped pellets with a diameter of 2.8 mm.

[0153] Next, the obtained pellet (cathode (50)) was bonded to the inner surface of a cathode can (20) made of stainless steel (SUS316L: thickness t=0.20mm) using a conductive resin adhesive in which carbon is used as a conductive filler, and the two were integrated to obtain a cathode unit. Next, the cathode unit was dried under reduced pressure in the atmosphere at 160°C for 11 hours. Next, a lithium foil blanked to a diameter of 2.8mm and a thickness of 0.44mm was pressed onto the pellet-shaped cathode (50) to form a lithium-cathode stacked electrode.

[0154] As described above, in this evaluation test, the positive current collector (41) and negative current collector (51) shown in the above embodiment were not installed, and the positive can (10) was made to function as the positive current collector (41), and the negative can (20) was made to function as the negative current collector (51). Furthermore, this point does not affect the results of this evaluation test.

[0155] Next, a nonwoven fabric made of glass fibers was dried and then blanked into a disc shape with a diameter of 3.6 mm to form a separator (60). Then, this separator (60) was placed on a lithium foil pressed onto the cathode (50), and a gasket (30) made of PEEK resin (polyetheretherketone resin) was placed in the opening of the cathode can (20).

[0156] (Preparation of electrolyte)

[0157] As for the electrolyte (70), each solvent of tetraglam (TEG), diethoxyethane (DEE), ethylene carbonate (EC), and vinylene carbonate (VC) was mixed to form a non-aqueous solvent. Then, the electrolyte (70) was obtained by dissolving LiTFSI (1M) as a supporting salt in the obtained non-aqueous solvent.

[0158] The mixing ratio of each solvent at this time was set to TEG:DEE:EC:VC = 44.8:42.7:5.0:7.5 in volume ratio.

[0159] Next, the electrolyte (70), adjusted in the order described above, was filled into the positive electrode can (10) and negative electrode can (20) prepared as described above, with a total of 7 μL per battery.

[0160] Next, the cathode unit was combined with the anode unit so that the separator (60) contacted the anode (40), and the anode can (10) and the cathode can (20) were sealed by caulking the caulking portion (12b) of the anode can (10). Then, a sample battery (non-aqueous electrolyte secondary battery (1)) for evaluation testing was produced by leaving it at 25°C for 7 days.

[0161] In addition, when making sample cells, seven sample cells were made with different radius of curvature R of the caulking portion (12b), as shown in Table 1. Specifically, a total of seven sample cells were made with different radius of curvature R at intervals of 0.1 mm within the range of 0.6 mm to 1.2 mm.

[0162] Among these, a sample cell of 0.7 mm, in which the radius of curvature R falls within the range of the present invention (0.7 mm to 1.1 mm), was designated as Example 1, a sample cell of 0.8 mm was designated as Example 2, a sample cell of 0.9 mm was designated as Example 3, a sample cell of 1.0 mm was designated as Example 4, and a sample cell of 1.1 mm was designated as Example 5. In addition, a sample cell of 0.6 mm, in which the radius of curvature R is outside the range of the present invention, was designated as Comparative Example 1, and a sample cell of 1.2 mm was designated as Comparative Example 2.

[0163]

[0164] In addition, all of the seven sample cells described above had a diameter D of 4.8 mm, which falls within the range of the present invention (4.6 mm to 5.0 mm), and the cell height H1 was set to 2.1 mm.

[0165] In addition, when conducting this evaluation test, five sample cells were produced with different ratios of so-called shoulder height (H2 / H1) as shown in Table 2, in the case where the radius of curvature R of the caulking part (12b) is 0.9 mm.

[0166] Specifically, a total of five sample cells were prepared with a shoulder height (H2 / H1) ratio ranging from 71% to 81%. Among these, a sample cell with a shoulder height (H2 / H1) ratio of 74%, which falls within the range of the present invention (74% to 79%), was designated as Example 6, a sample cell with a ratio of 76% was designated as Example 7, and a sample cell with a ratio of 79% was designated as Example 8. Additionally, a sample cell with a shoulder height (H2 / H1) ratio of 71%, which falls outside the range of the present invention, was designated as Comparative Example 3, and a sample cell with a ratio of 81% was designated as Comparative Example 4.

[0167]

[0168] (Evaluation Test)

[0169] For each of the above-described sample batteries (Examples 1 to 8, Comparative Examples 1 to 4), heating was performed under reflow conditions, and the appearance after heating was observed. By performing this observation, the presence or absence of leakage and the presence or absence of bulging deformation of the positive wall portion (21) of the negative electrode can (20) were confirmed.

[0170] In addition, the battery capacity immediately after heating (initial capacity) was measured, and the battery capacity was measured again after a certain period of time to calculate the capacity retention rate.

[0171] Specifically, for each of the seven sample cells in total of Examples 1 to 5 and Comparative Examples 1 and 2 shown in Table 1, heating was performed at 260°C for 10 seconds. At this time, 60 of each sample cell were prepared and heated. Then, an external inspection was performed on all 60 sample cells, and the number of sample cells in which the electrolyte (70) was leaking out from inside the cell was counted to determine the leakage rate (%).

[0172] In addition, the heat treatment of heating at 260°C for 10 seconds corresponds to the heating conditions associated with reflow mounting (reflow soldering).

[0173] The results of the measured leakage rate are shown in Table 1 and Figure 3. Also, the results of measuring the initial capacity (mAh) after heating are shown in Table 1 and Figure 3.

[0174] In addition, after performing the heating described above, each sample battery was stored for 480 hours in a constant temperature bath adjusted to an atmosphere of 80°C and 90% relative humidity (RH), and then the battery capacity was measured again. Then, the capacity retention rate (%) was calculated by comparing the measured capacity with the initial capacity. By doing so, it is possible to determine the degree of degradation of the non-aqueous electrolyte secondary battery under a high temperature and high humidity environment.

[0175] The results of the calculated capacity retention rate are shown in Table 1 and Figure 3.

[0176] In addition, for each of the five sample cells in total of Examples 6 to 8 and Comparative Examples 3 and 4 shown in Table 2, heating was performed at 260°C for 10 seconds as described above. At this time, 20 of each sample cell were prepared and heated. Then, an external inspection was performed on all 20 of each sample cell, and the leakage rate (%) was calculated as described above. In addition, whether bulging deformation occurred was visually confirmed, and the bulging deformation rate (%) was calculated.

[0177] The results of the measured leakage rates and bulging deformation rates are shown in Table 2 and Figure 4.

[0178] As shown in Table 1 and Fig. 3, in the case of the sample batteries of Examples 1 to 5 in which the radius of curvature R of the coking portion (12b) falls within the range of the present invention (0.7 mm to 1.1 mm), it was confirmed that there was no leakage and the capacity retention rate after storage in a high temperature and high humidity environment exceeded 50%. Accordingly, it was actually confirmed that the sample batteries of Examples 1 to 5 are non-aqueous electrolyte secondary batteries with excellent leakage resistance, cycle characteristics, and long-term storage capabilities.

[0179] In particular, in the case of the sample cells of Examples 2 to 4, in which the radius of curvature R is within the range of 0.8 mm to 1.0 mm, it was confirmed that the capacity retention rate after storage under a high temperature and high humidity environment exceeded 60%. By this, it was actually confirmed that it is a non-aqueous electrolyte secondary battery capable of maintaining battery capacity.

[0180] In contrast, in the case of sample cells of Comparative Examples 1 and 2 in which the radius of curvature R of the caulking portion (12b) falls outside the range of the present invention (0.7mm to 1.1mm), it was confirmed that leakage actually occurred and the capacity retention rate tended to be below 50%.

[0181] In addition, as shown in Table 2 and Figure 4, in the case of the sample cells of Examples 6 to 8, in which the ratio of shoulder height (H2 / H1) falls within the scope of the present invention (74% to 79%), it was confirmed that there was no leakage and no bulging deformation. Accordingly, it was actually confirmed that the sample cells of Examples 6 to 8 are non-aqueous electrolyte secondary batteries with excellent leakage resistance, cycle characteristics, and long-term storage properties.

[0182] In contrast, in the case of the sample cells of Examples 3 and 4, in which the ratio of shoulder height (H2 / H1) falls outside the scope of the present invention (74% to 79%), it was confirmed that leakage and bulging deformation actually occurred.

[0183] The embodiments of the present invention have been described above. These embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments may be implemented in various other forms, and various omissions, substitutions, and modifications may be made within the scope of not departing from the essence of the invention. Embodiments and variations thereof include, for example, those that can be easily conceived by a person skilled in the art, substantially identical ones, and those within the scope of equivalence.

[0184] [Industrial Applicability]

[0185] According to the present invention, a compact non-aqueous electrolyte secondary battery can be obtained that exhibits excellent leakage resistance even when exposed to high-temperature environments, as well as excellent cycle characteristics and long-term storage capabilities. Therefore, it has industrial applicability. Explanation of the symbols

[0186] D: Diameter of the non-aqueous electrolyte secondary battery R: Radius of curvature of the coking section H1: Height of non-aqueous electrolyte secondary battery H2: Height of positive can 1: Non-aqueous electrolyte secondary battery 2: Receiving container 3: Power Generation Factor 10: Positive Can 11: Bottom wall section 12: Outer wall section 12b: Caulking section 20: Cathode can 21: Front wall section 22: Inner wall section 30: Gasket 60: Separator 70: Electrolyte

Claims

Claim 1 A reflow-mounted type non-aqueous electrolyte secondary battery comprising a receiving container having a positive electrode can and a negative electrode can caulked and fixed to the positive electrode can via a gasket, an electrolyte, and a power generation element contained within the receiving container, wherein the positive electrode can is formed in a cylindrical shape with a bottom having a bottom wall portion and an outer wall portion formed along the outer edge of the bottom wall portion, and the negative electrode can is formed in a cylindrical shape with a top wall portion and an inner wall portion formed along the outer edge of the top wall portion and disposed inside the outer wall portion, wherein the portion of the outer wall portion located on the side of the top wall portion is a caulked portion curved with a radius of curvature R toward the inner wall portion side as it extends from the side of the bottom wall portion toward the edge of the opening of the outer wall portion, and wherein the diameter D of the non-aqueous electrolyte secondary battery is 4.8 mm and the height H1 of the non-aqueous electrolyte secondary battery is 2.1 mm A non-aqueous electrolyte secondary battery characterized in that the height H2 of the positive electrode can is within the range of 74% to 79% with respect to the height H1 of the non-aqueous electrolyte secondary battery, and the radius of curvature R of the coking portion is 0.9mm. Claim 2 A non-aqueous electrolyte secondary battery according to claim 1, wherein the generating element comprises a positive electrode installed on the positive electrode can side and containing spinel-type lithium manganese oxide as a positive active material, a negative electrode installed on the negative electrode can side and containing carbon-coated SiOx (0 < x < 2) as a negative active material, and a separator disposed between the positive electrode and the negative electrode, and wherein the electrolyte comprises a mixed solvent containing ethylene carbonate (EC) and vinylene carbonate (VC) in a glame-based solvent. Claim 3 delete

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