Non-aqueous electrolyte secondary battery

Abstract

The nonaqueous electrolyte secondary battery according to the present application includes a storage container having a positive electrode can, a gasket, and a negative electrode can, and a power generating element containing an electrolyte. The positive electrode can is formed in a bottomed cylindrical shape having a bottom wall portion and an outer wall portion. The negative electrode can is formed in a toped cylindrical shape having a top wall portion and an inner wall portion. A portion of the outer wall portion on the top wall portion side is a calked portion 12b that is curved toward the inner wall portion side with a curvature radius R from the bottom wall portion side to an opening end edge of the outer wall portion. The nonaqueous electrolyte secondary battery has a diameter of 4.6 mm to 5.0 mm. A height H2 of the positive electrode can is in a range of 74% to 79% relative to a height H1 of the nonaqueous electrolyte secondary battery. The curvature radius R of the calked portion is in a range of 0.7 mm to 1.1 mm.

Description

Technical Field

[0001] This invention relates to non-aqueous electrolyte secondary batteries. Background Technology

[0002] A non-aqueous electrolyte secondary battery is a type of secondary battery that, within a sealed container, mainly comprises: a positive electrode and a negative electrode forming a pair of polarized electrodes, a separator disposed between the positive and negative electrodes, and an electrolyte containing supporting salts and a solvent. Because of its high energy density and lightweight nature, this type of non-aqueous electrolyte secondary battery is used, for example, in the power supply units of electronic devices and in the energy storage units that absorb fluctuations in the power output of power generation devices.

[0003] In particular, non-aqueous electrolyte secondary batteries containing silicon oxide (SiOx) with a carbon-coated surface as the negative electrode active material are suitable for use as small non-aqueous electrolyte secondary batteries in coin-shaped (button-shaped) form due to their high discharge capacity.

[0004] Coin-shaped non-aqueous electrolyte secondary batteries are known to have excellent charge-discharge characteristics at high voltage and high energy density, as well as long cycle life and high reliability. Therefore, coin-shaped non-aqueous electrolyte secondary batteries are suitable for use as backup power for semiconductor memory or clock functions in various small electronic devices such as mobile phones, PDAs, portable game consoles, and digital cameras.

[0005] As such coin-shaped non-aqueous electrolyte secondary batteries, for example, non-aqueous electrolyte secondary batteries that can be used even in high-temperature environments of around 80°C while suppressing electrolyte evaporation and moisture intrusion are known (see, for example, Patent Document 1 below).

[0006] In this non-aqueous electrolyte secondary battery, by specifying the outer diameter (4-12 mm) and height (1-3 mm), and defining the radius of curvature (R) and shoulder height (height h2 of the positive electrode can / height h1 of the secondary battery) of the positive electrode can during sealing (sealing), gaps between the positive or negative electrode can and the gasket are suppressed. This improves the sealing performance. Consequently, electrolyte evaporation and moisture intrusion into the battery are suppressed.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent document 1: Japanese Patent Application Publication No. 2015-159102. Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In coin-shaped non-aqueous electrolyte secondary batteries, the smaller the outer diameter, the more susceptible they are to the effects of electrolyte evaporation at high temperatures or the intrusion of moisture into the battery. In this regard, with the further miniaturization and thinning of various electronic devices, it is expected that the outer diameter of coin-shaped non-aqueous electrolyte secondary batteries will become mainstream at around 4mm to 6mm in the future. Therefore, further improvements in battery sealing are required.

[0012] Furthermore, in coin-type non-aqueous electrolyte secondary batteries, the ability to handle reflow mounting is required to improve welding efficiency during installation. It is important to maintain stable charge and discharge during long-term use or storage, even after reflow mounting (reflow soldering), and to suppress electrolyte leakage, ensuring the electrolyte remains continuously within the battery.

[0013] However, during reflow installation, for example, when the peak temperature reaches around 260°C, the battery is exposed to a higher temperature environment. Therefore, there is a risk of increased internal pressure and battery deformation. This deformation can easily create gaps between the positive or negative electrode canister and the gasket, potentially leading to electrolyte evaporation or moisture intrusion into the battery.

[0014] Therefore, even with the conventional non-aqueous electrolyte secondary batteries described in Patent Document 1, the reliability of the battery, such as cycle characteristics and long-term storage, is easily reduced when reflux installation is assumed, and the leakage rate is likely to increase. Therefore, there is room for improvement in the case of reflux installation.

[0015] The present invention was made in view of the following circumstances, and its purpose is to provide a small 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.

[0016] Methods for solving problems

[0017] (1) The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery having a housing and a power generation element. The housing has a positive electrode can and a negative electrode can fixed to the positive electrode can via a gasket and a converging seam. The power generation element contains an electrolyte and is housed inside the housing. The positive electrode can is formed as a bottomed cylindrical shape, having a bottom wall portion and an outer wall portion formed along the outer periphery of the bottom wall portion. The negative electrode can is formed as a top cylindrical shape, having a top wall portion and an inner wall portion formed along the outer periphery 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 converging seam portion, which bends with a radius of curvature R towards the inner wall portion from the opening edge of the bottom wall portion towards the opening edge 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 in the range of 74% to 79% relative to the height H1 of the non-aqueous electrolyte secondary battery. The radius of curvature R of the converging slit is in the range of 0.7 mm to 1.1 mm.

[0018] According to the non-aqueous electrolyte secondary battery of the present invention, while specifying the so-called shoulder height (H2 / H1) within the range of 74% to 79%, the positive electrode can and the negative electrode can are fixed together via a gasket using a converging joint with a radius of curvature R specified within the range of 0.7 mm to 1.1 mm. Therefore, the negative electrode can be securely pressed in while appropriately compressing the gasket.

[0019] It should be noted that when the radius of curvature R of the seam is smaller than 0.7 mm, the seam is concentrated in the area around the opening of the outer wall. In this case, although the negative electrode can and gasket can be firmly pressed towards the bottom wall of the positive electrode can, the force pressing the negative electrode can and gasket towards the center of the container is weakened. Therefore, gaps can easily form between the positive or negative electrode can and the gasket, potentially leading to leakage (including electrolyte evaporation) or moisture intrusion. This results in reduced cycle performance or long-term shelf life.

[0020] Conversely, when the radius of curvature R of the seam is larger than 1.1 mm, the seam forms in a wide area on the outer wall. In this case, although the force pressing the negative electrode can and gasket towards the center of the receiving container becomes stronger, the force pressing the negative electrode can and gasket towards the bottom wall of the positive electrode can becomes weaker. Therefore, in this case, gaps are also easily generated between the positive or negative electrode can and the gasket, resulting in the same undesirable situation as described above.

[0021] Furthermore, when the shoulder height (H2 / H1) is less than 74%, stress concentrates on the open end of the inner wall of the negative electrode can during the sealing process. This easily leads to bulging deformation, such as expansion of the top wall of the negative electrode can. Consequently, this results in poor appearance and ultimately, product defects.

[0022] Conversely, when the shoulder height (H2 / H1) is greater than 79%, sufficient stress cannot be provided to the negative electrode can during sealing, resulting in a gap between the positive electrode can or negative electrode can and the gasket, thus causing the aforementioned defects.

[0023] In contrast, in the non-aqueous electrolyte secondary battery of this invention, the shoulder height (H2 / H1) is in the range of 74% to 79%, and the radius of curvature R of the slit is in the range of 0.7 mm to 1.1 mm. Therefore, the aforementioned adverse conditions are difficult to occur, and a non-aqueous electrolyte secondary battery with excellent leakage resistance, cycle characteristics, and long-term storage properties can be manufactured. Therefore, even when miniaturizing the diameter D to approximately 4 mm (within the range of 4.6 mm to 5.0 mm), leakage resistance can be maintained. Furthermore, leakage resistance can be maintained even when used or stored at high temperatures. Therefore, a non-aqueous electrolyte secondary battery with improved operational reliability and ease of use can be manufactured.

[0024] (2) The radius of curvature R of the converging slit can also be in the range of 0.8mm to 1.0mm.

[0025] In this configuration, gaps between the positive or negative electrode canister and the gasket can be effectively suppressed, making leakage or moisture intrusion less likely. Therefore, it exhibits superior leakage resistance and can maintain battery capacity stably over a long period.

[0026] (3) The power generation element comprises: a positive electrode disposed on the positive electrode tank side, containing spinel-type lithium manganese oxide as the positive electrode active material; a negative electrode disposed on the negative electrode tank side, containing carbon-coated SiOx (0 < x < 2) as the negative electrode active material; and a separator disposed between the positive electrode and the negative electrode; the electrolyte may contain a mixed solvent containing ethylene glycol ester (EC) and vinylene carbonate (VC) in a glycol dimethyl ether solvent.

[0027] In this configuration, 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, which is a glycol dimethyl ether-based solvent containing ethylene glycol ester (EC) and vinylene carbonate (VC). Therefore, even under the heating associated with reflow assembly (reflow soldering), the risk of solvent vaporization is minimal. Consequently, heat resistance to withstand heating is achieved while suppressing degradation of the positive electrode, negative electrode, and electrolyte. Furthermore, since the risk of solvent vaporization is minimal even under the heating associated with reflow assembly, there is less risk of pressure rise in the storage container, allowing for the fabrication of a non-aqueous electrolyte secondary battery whose storage container is less prone to deformation.

[0028] Therefore, a non-aqueous electrolyte secondary battery capable of reflow installation can be manufactured. In particular, even when the internal pressure rises during reflow installation, for example due to exposure to a high temperature environment such as 260°C, as mentioned above, the leakage resistance is excellent, thus maintaining excellent cycle characteristics and long-term shelf life even after reflow.

[0029] The effects of the invention

[0030] According to the present invention, a small non-aqueous electrolyte secondary battery is provided, which has excellent leakage resistance even when exposed to high temperature environments, and excellent cycle characteristics and long-term storage properties. Attached Figure Description

[0031] [ Figure 1 [ ] A cross-sectional view showing an embodiment of the non-aqueous electrolyte secondary battery according to the present invention.

[0032] [ Figure 2 ] Will Figure 1 An enlarged cross-sectional view of the area surrounding the seam shown.

[0033] [ Figure 3 The graph shows the relationship between the radius of curvature of the joint and the leakage rate and capacity maintenance rate.

[0034] [ Figure 4 The graph shows the relationship between shoulder height (H2 / H1) and the incidence of leakage and bulging deformation. Detailed Implementation

[0035] The embodiments of the non-aqueous electrolyte secondary battery according to the present invention will be described below with reference to the accompanying drawings. It should be noted that the non-aqueous electrolyte secondary battery of this embodiment is a secondary battery constructed by housing the active material used as the positive or negative electrode and the separator within a housing container.

[0036] like Figure 1 and Figure 2As shown, the non-aqueous electrolyte secondary battery 1 of this embodiment is a so-called coin (button) type battery, which mainly includes a storage container 2 and a power generation element 3 stored inside the storage container 2.

[0037] The storage container 2 mainly comprises a positive electrode container 10 and a negative electrode container 20 which is fixed to the positive electrode container 10 via a gasket 30. The positive electrode container 10 and the negative electrode container 20 are fixed in such a way that the bottom wall portion 11 of the positive electrode container 10 (described later) and the top wall portion 21 of the negative electrode container 20 (described later) face each other.

[0038] In this embodiment, the axis extending through the center of the bottom wall portion 11 and the top wall portion 21 in a direction facing each other is called the battery axis O. Furthermore, in a top view viewed from the direction of the battery axis O, the direction intersecting the battery axis O is called radial, and the direction of rotation around the battery axis O is called circumferential. Additionally, the direction along the battery axis O from the bottom wall portion 11 to the top wall portion 21 is called upward, and the opposite direction is called downward.

[0039] The power generation element 3 mainly comprises a positive electrode 40 disposed on the positive electrode tank 10 side, a negative electrode 50 disposed on the negative electrode tank 20 side, and a diaphragm 60 disposed between the positive electrode 40 and the negative electrode 50. The power generation element 3 contains an electrolyte 70 and is housed within a storage space S formed inside the storage container 2.

[0040] (Storage container)

[0041] A detailed description of storage container 2 is provided.

[0042] The storage container 2 mainly comprises a bottomed cylindrical metal positive electrode container 10 and a topped cylindrical metal negative electrode container 20 which is fixed to the positive electrode container 10 by a gasket 30.

[0043] The material of the positive electrode container 10 is not limited to a specific material; for example, SUS 316L or SUS329J4L can be used. Furthermore, conventionally known stainless steel can be used as the material for the positive electrode container 10. Additionally, other metal materials besides stainless steel can also be used for the positive electrode container 10.

[0044] The material of the negative electrode container 20 is not limited to a specific material; for example, it can be made of the same material as the positive electrode container 10, such as SUS 316L or SUS 329J4L. Alternatively, SUS 304-BA or other conventionally known stainless steels can be used as the material for the negative electrode container 20. Furthermore, metal materials other than stainless steel can be used for the negative electrode container 20. For example, a cladding material formed by pressing copper, nickel, or other materials onto stainless steel can be used for the negative electrode container 20.

[0045] (Positive electrode container)

[0046] The positive electrode can 10 is formed into a bottomed cylindrical shape, and includes: a bottom wall portion 11 formed into a circular shape when viewed from above, and an annular outer wall portion 12 formed along the circumference of the bottom wall portion 11 and extending upward at the outer periphery of the bottom wall portion 11.

[0047] The lower sidewall portion 12a, which is connected to the outer periphery of the bottom wall portion 11 in the outer wall portion 12, is the portion that forms the largest outer diameter of the non-aqueous electrolyte secondary battery 1. Therefore, the outer diameter of the lower sidewall portion 12a is equivalent to the diameter D of the non-aqueous electrolyte secondary battery 1.

[0048] In this embodiment, the positive electrode can 10 is formed with a diameter D in the range of 4.6 mm to 5.0 mm.

[0049] A converging slit 12b is formed on the upper side wall of the outer wall portion 12 located on the top wall side of the negative electrode tank 20. The converging slit 12b bends with a radius of curvature R towards the radially inward side (toward towards the inner wall portion 22 of the negative electrode tank 20) ​​from the bottom wall portion 11 side toward the opening edge of the outer wall portion 12.

[0050] In this embodiment, the slit portion 12b is formed with a radius of curvature R in the range of 0.7 mm to 1.1 mm.

[0051] In the illustrated example, the radius of curvature of the outer peripheral surface of the slit portion 12b is taken as R. However, the radius of curvature of the inner peripheral surface of the slit portion 12b or the neutral line of the slit portion 12b (not shown, the part of the slit portion 12b that does not bear tensile or compressive stress even when bent) may also be taken as R.

[0052] It should be noted that, prior to the seam-sealing process, the outer wall portion 12, including the seam-sealing portion 12b, is integrally formed as a cylinder extending along the battery axis O and opening upwards. Then, during sealing (seam-sealing), stress is applied to the seam-sealing portion 12b, causing it to bend radially inwards with the aforementioned radius of curvature R. By seaming the seam-sealing portion 12b towards the radial inwards, the negative electrode can 20 is securely seamed and fixed via the gasket 30.

[0053] It should be noted that, as Figure 2 As shown, the overall height of the outer wall portion 12 along the battery shaft O after the seam is closed is equivalent to the height H2 of the positive electrode container 10. In this embodiment, the relationship between the positive electrode container 10 and the negative electrode container 20 is defined such that the height H2 of the positive electrode container 10 is in the range of 74% to 79% relative to the height H1 of the non-aqueous electrolyte secondary battery 1. This will be explained again later.

[0054] (Negative electrode container)

[0055] like Figure 1 and Figure 2As shown, the negative electrode tank 20 is formed into a top cylindrical shape, which includes: a top wall portion 21 formed into a circular shape when viewed from above, and an annular inner wall portion 22 formed along the circumference of the top wall portion 21 at the outer periphery of the top wall portion 21 and extending downward.

[0056] After the negative electrode container 20 is assembled with the positive electrode container 10 from above, with its inner wall portion 22 entering the inner side of the outer wall portion 12, it is fixed by a seam seal via a gasket 30, thereby integrally assembling with the positive electrode container 10. Therefore, the negative electrode container 20 is assembled with high precision relative to the positive electrode container 10 via the gasket 30.

[0057] Compared to the constricted slit 12b of the outer wall portion 12 of the positive electrode container 10, the top wall portion 21 is positioned above. At this time, the height along the battery axis O between the lower surface of the bottom wall portion 11 of the positive electrode container 10 and the upper surface (top surface) of the top wall portion 21 of the negative electrode container 20 is taken as the overall height H1 of the non-aqueous electrolyte secondary battery 1.

[0058] In this embodiment, the positive electrode container 10 and the negative electrode container 20 are combined such that the overall height H1 of the non-aqueous electrolyte secondary battery 1 after the seam is closed is in the range of 1.0 mm to 3.0 mm. At this time, the positive electrode container 10 and the negative electrode container 20 are combined such that the height H2 of the positive electrode container 10 is in the range of 74% to 79% relative to the height H1 of the non-aqueous electrolyte secondary battery 1.

[0059] It should be noted that the height H2 of the positive electrode tank 10 can be chosen arbitrarily as long as the so-called shoulder height (H2 / H1) falls within the range of 74% to 79%.

[0060] The inner wall portion 22 is formed to extend downward from the outer periphery of the top wall portion 21 and is positioned above the bottom wall portion 11 of the positive electrode tank 10, with the lower end portion 22a clamping the gasket 30.

[0061] In the illustrated example, the inner wall portion 22 is formed as a two-section cylindrical shape that expands in diameter from top to bottom. However, it is not limited to two sections; for example, the inner wall portion 22 can be formed as a multi-section cylindrical shape that gradually expands in diameter from top to bottom in three or more sections.

[0062] Furthermore, in the illustrated example, the inner wall portion 22 folds back upwards from the lower end portion 22a, integrally forming an annular folded-back portion 23 that overlaps radially outwards relative to the inner wall portion 22. Therefore, the outer diameter of this folded-back portion 23 is the portion that becomes the maximum outer diameter of the negative electrode container 20. It should be noted that the outer diameter of the folded-back portion 23 is smaller than the inner diameter of the lower side wall portion 12a of the outer wall portion 12. It should also be noted that the folded-back portion 23 is not essential and may be omitted.

[0063] In the negative electrode can 20 configured as described above, the constriction portion 12b of the positive electrode can 10 is bent through the constriction portion in a manner located above the folded-back portion 23. Therefore, the negative electrode can 20 is reliably prevented from falling upwards via the gasket 30.

[0064] (washer)

[0065] The gasket 30 is formed in a double ring shape, which surrounds the inner wall 22 of the negative electrode tank 20 from the radial outer side and the radial inner side throughout the entire circumference.

[0066] The gasket 30 includes: an annular outer gasket portion 31 disposed between the outer wall portion 12 of the positive electrode tank 10 and the inner wall portion 22 of the negative electrode tank 20; an annular inner gasket portion 32 disposed on the inner side of the inner wall portion 22 of the negative electrode tank 20; and an annular flange portion 33 that connects the lower end of the outer gasket portion 31 and the lower end of the inner gasket portion 32 in the radial direction.

[0067] The outer washer portion 31 is disposed between the outer wall portion 12 and the inner wall portion 22 in a predetermined compressed state by being joined by the joining portion 12b. The outer washer portion 31 fits tightly and without gap with the inner circumferential surface of the outer wall portion 12 and the outer circumferential surface of the inner wall portion 22, respectively. The flange portion 33 is disposed between the lower end portion 22a of the inner wall portion 22 and the bottom wall portion 11 in a predetermined compressed state by being joined by the joining portion 12b. The flange portion 33 fits tightly and without gap with the lower end portion 22a of the inner wall portion 22 and the bottom wall portion 11, respectively. The inner washer portion 32 fits tightly and without gap with the inner circumferential surface of the inner wall portion 22 by being joined by the joining portion 12b.

[0068] Thus, the gasket 30 is securely clamped between the positive electrode can 10 and the negative electrode can 20 by the seam 12b. Furthermore, the gasket 30 integrates the positive electrode can 10 and the negative electrode can 20 into one unit, forming a sealed storage space S between the positive electrode can 10 and the negative electrode can 20.

[0069] It should be noted that the storage space S is the space surrounded by the bottom wall 11 of the positive electrode tank 10, the top wall 21 of the negative electrode tank 20, and the inner gasket 32.

[0070] The gasket 30 is preferably made of a resin with a heat distortion temperature of 230°C or higher. If the heat distortion temperature of the resin material used in the gasket 30 is 230°C or higher, it can suppress the gasket 30 from deforming significantly due to reflow soldering or heating during use of the non-aqueous electrolyte secondary battery 1, thereby preventing electrolyte leakage and other adverse conditions.

[0071] Examples of materials that can be used for this type of gasket 30 include polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyamide, liquid crystal polymer (LCP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyether ether ketone resin (PEEK), polyether nitrile resin (PEN), polyether ketone resin (PEK), polyacrylate resin, polybutylene terephthalate resin (PBT), polycyclohexanediol terephthalate resin, polyethersulfone resin (PES), polyaminobismaleimide resin, polyetherimide resin, and fluoropolymers.

[0072] Among them, when using either PPS or PEEK, it is preferable from the viewpoint that the gasket 30 can be significantly deformed during use or storage in high-temperature environments, thereby further improving the sealing performance of the non-aqueous electrolyte secondary battery 1.

[0073] Furthermore, materials containing glass fibers, mica whiskers, ceramic powder, etc., added to the above-mentioned materials at an amount of less than 30% by mass can be suitably used for gasket 30. By using such a material, adverse conditions such as significant deformation of gasket 30 due to heating during reflow and leakage of electrolyte 70 can be suppressed.

[0074] Regarding the storage container 2 constructed as described above, it is designed such that all the configuration and dimensional relationships shown in (1) to (3) are satisfied.

[0075] (1) The diameter D of the non-aqueous electrolyte secondary battery 1 is in the range of 4.6 mm to 5.0 mm.

[0076] (2) The radius of curvature R of the converging part 12b of the positive electrode tank 10 is in the range of 0.7mm to 1.1mm.

[0077] (3) The shoulder height (H2 / H1), that is, the height H2 of the positive electrode tank 10 relative to the height H1 of the non-aqueous electrolyte secondary battery 1, is in the range of 74%~79%.

[0078] It should be noted that the thickness of the metal plates used in the positive electrode tank 10 and the negative electrode tank 20 is usually around 0.1~0.3mm. For example, the average thickness of the positive electrode tank 10 or the negative electrode tank 20 as a whole is about 0.15mm.

[0079] (Power generation element)

[0080] Next, the power generation element 3 will be described in detail.

[0081] As mentioned above, the power generation element 3 mainly has a positive electrode 40, a negative electrode 50 and a diaphragm 60, which are stored together with the electrolyte 70 in the storage space S of the storage container 2.

[0082] The positive electrode 40, located on the positive electrode tank 10 side, and the negative electrode 50, located on the negative electrode tank 20 side, are arranged facing each other in the storage space S via a separator 60. It should be noted that the positive electrode 40, the negative electrode 50, and the separator 60 are impregnated with electrolyte 70, which is filled within the storage container.

[0083] The positive electrode 40 is electrically connected to the upper surface of the bottom wall portion 11 of the positive electrode container 10 via the positive electrode current collector 41. In contrast, the negative electrode 50 is electrically connected to the lower surface of the top wall portion 21 of the negative electrode container 20 via the negative electrode current collector 51.

[0084] However, this is not the only option. For example, the positive current collector 41 and the negative current collector 51 can be omitted, and the positive electrode 40 can be directly connected to the positive electrode container 10, so that the positive electrode container 10 has the function of a current collector. Alternatively, the negative electrode 50 can be directly connected to the negative electrode container 20, so that the negative electrode container 20 has the function of a current collector.

[0085] It should be noted that the outer periphery of the diaphragm 60 inside the storage container 2 is in contact with the gasket 30, and is thus held in place by the gasket 30.

[0086] (positive electrode)

[0087] In the positive electrode 40, there are no special restrictions on the type of positive electrode active material. For example, it is preferable to use a material containing spinel-type lithium manganese oxide as the positive electrode active material.

[0088] The content of the positive electrode active material in the positive electrode 40 is determined by considering the required discharge capacity of the non-aqueous electrolyte secondary battery 1, and can be set to a range of 50 to 95% by mass. If the content of the positive electrode active material is above the lower limit of the above-mentioned preferred range, it is easy to obtain a sufficient discharge capacity; if it is below the upper limit of the preferred range, it is easy to form the positive electrode 40.

[0089] The positive electrode 40 may contain conductive additives (hereinafter, the conductive additives used in the positive electrode 40 are sometimes referred to as "positive electrode conductive additives").

[0090] Examples of positive electrode conductive additives include carbonaceous materials such as furnace black, Ketjen black, acetylene black, and graphite.

[0091] The positive electrode conductive additive can be one of the above materials alone, or two or more can be used in combination.

[0092] The positive electrode 40 may contain a binder (the binder used in the positive electrode 40 is sometimes referred to as the "positive electrode binder").

[0093] As such a positive electrode binder, conventionally known materials can be used, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), etc., and binders composed of multiple combinations thereof can be used.

[0094] In addition, one of the above-mentioned substances may be used alone as the positive electrode binder, or two or more may be used in combination. The content of the positive electrode binder in the positive electrode 40 may, for example, be set to 1-20% by mass.

[0095] It should be noted that in this specification, when using "~" to represent the upper and lower limits for numerical ranges, unless otherwise specified, the range is assumed to include both the upper and lower limits. Therefore, for example, when recorded as 1~20% by mass, it means 1% or more and 20% or less by mass.

[0096] As the positive current collector 41, conventionally known materials can be used, such as conductive resin binders that use carbon as a conductive filler.

[0097] In addition, in this embodiment, as the positive electrode active material, besides the aforementioned lithium manganese oxide, other positive electrode active materials may also be included, such as any one or more of other oxides such as molybdenum oxide, lithium iron phosphorus oxide, lithium cobalt oxide, lithium nickel oxide, and vanadium oxide.

[0098] (negative electrode)

[0099] In the negative electrode 50, there are no special restrictions on the type of negative electrode active material, but silicon oxide is preferred as the negative electrode active material.

[0100] In the negative electrode 50, the negative electrode active material is preferably composed of a material formed by carbon-coated SiOx, for example, carbon coating of silicon oxide represented by SiOx (0 < x < 2).

[0101] In addition, the negative electrode 50 may contain other negative electrode active materials besides SiOx (0 < x < 2), such as Si, C and other negative electrode active materials.

[0102] When using granular SiOx (0 < x < 2) as the negative electrode active material, their particle size (D50) is not particularly limited, for example, it can be selected in the range of 0.1 to 30 μm, and more preferably in the range of 1 to 10 μm.

[0103] If the particle size (D50) of SiOx is lower than the lower limit of the above range, the battery characteristics may be impaired, for example, when stored in harsh high-temperature and high-humidity environments, when using a non-aqueous electrolyte secondary battery 1, or due to increased reactivity caused by reflow soldering. Furthermore, if the particle size (D50) of SiOx exceeds the upper limit of the above range, the discharge rate may decrease.

[0104] The content of the negative electrode active material, i.e., SiOx (0 < x < 2), in the negative electrode 50 is determined by considering the discharge capacity required by the non-aqueous electrolyte secondary battery 1, and can be selected in the range of 50% by mass or more, preferably in the range of 60 to 80% by mass.

[0105] In the negative electrode 50, if the content of the negative electrode active material composed of the above elements is above the lower limit of the above range, it is easy to obtain sufficient discharge capacity. In addition, if it is below the upper limit, it is easy to form the negative electrode 50.

[0106] The negative electrode 50 may contain a conductive additive (hereinafter sometimes referred to as the "negative electrode conductive additive"). The negative electrode conductive additive may, for example, be the same substance as the positive electrode conductive additive.

[0107] The negative electrode 50 may contain a binder (the binder used in the negative electrode 50 is sometimes referred to as the "negative electrode binder").

[0108] As such a negative electrode binder, options include, for example, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethyl cellulose (CMC), polyimide (PI), polyamide-imide (PAI), etc.

[0109] The negative electrode binder may be one of the above substances used alone, or two or more substances may be used in combination.

[0110] It should be noted that when using polyacrylic acid as a negative electrode binder, the pH of the polyacrylic acid can be pre-adjusted to around 3-10. In this case, pH adjustment can be achieved, for example, using alkali metal hydroxides such as lithium hydroxide or alkaline earth metal hydroxides such as magnesium hydroxide.

[0111] The content of the negative electrode binder in the negative electrode 50 can be set to, for example, a range of 1 to 20% by mass.

[0112] It should be noted that, in this embodiment, the size and thickness of the negative electrode 50 can be formed in the same way as the size and thickness of the positive electrode 40.

[0113] It should be noted that a structure in which lithium foil or other lithium body 80 is provided on the surface of the negative electrode 50, that is, between the negative electrode 50 and the separator 60, as shown in the figure. However, the lithium body 80 is not necessary and may be omitted.

[0114] (Diaphragm)

[0115] The separator 60 is located between the positive electrode 40 and the negative electrode 50, and can be an insulating membrane with high ion permeability and mechanical strength.

[0116] As the separator 60, materials that have been used for separators in non-aqueous electrolyte secondary batteries can be used without any restrictions. Examples include glasses such as alkaline glass, borosilicate glass, quartz glass, and lead glass, and nonwoven fabrics made of resins such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyamide-imide (PAI), polyamide, and polyimide (PI).

[0117] Of the aforementioned materials, glass nonwoven fabric is preferred as the diaphragm 60, and borosilicate glass nonwoven fabric is more preferred. Glass nonwoven fabric not only has excellent mechanical strength but also high ion permeability, thus reducing internal resistance and improving discharge capacity.

[0118] It should be noted that the thickness of the separator 60 is determined by factors such as the size of the non-aqueous electrolyte secondary battery 1 or the material of the separator 60, and can be set to 5~300μm.

[0119] (electrolyte)

[0120] Electrolyte 70 is typically a liquid prepared by dissolving the supporting salt in a non-aqueous solvent.

[0121] In this embodiment, the non-aqueous solvent used to form the electrolyte 70 can be a mixed solvent containing tetraethylene glycol dimethyl ether (TEG) as the main solvent, diethoxyethane (DEE) as the secondary solvent, and ethylene glycol carbonate (EC) and vinylene carbonate (VC) as additives.

[0122] The choice of non-aqueous solvent is usually determined by considerations such as the heat resistance or viscosity required by the electrolyte 70. In this embodiment, a non-aqueous solvent composed of the solvents described above is used. It should be noted that the main solvent used to constitute the glycol dimethyl ether-based solvent can be tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc.

[0123] In this embodiment, an electrolyte 70 containing a non-aqueous solvent, tetraethylene glycol dimethyl ether (TEG), diethoxyethane (DEE), and ethylene glycol carbonate (EC), can be used. With this configuration, DEE and TEG are solvated with Li ions that form a supporting salt.

[0124] At this point, since the number of donors for DEE is higher than that for TEG, DEE selectively solvates with Li ions. Thus, DEE and TEG solvate with Li ions that form a supporting salt, protecting the Li ions. Therefore, even in high-temperature and high-humidity environments where moisture penetrates the interior of the non-aqueous electrolyte secondary battery 1, the reaction between moisture and Li is prevented, suppressing the decrease in discharge capacity and achieving improved storage stability.

[0125] The ratios of the above-mentioned solvents in the non-aqueous solvents of electrolyte 70 are not particularly limited. For example, the following ratios can be selected: TEG: 30% by mass or more and 48.5% by mass or less (30~48.5%), DEE: 30% by mass or more and 48.5% by mass or less (30~48.5%), EC: 0.5% by mass or more and 10% by mass or less (0.5~10%), and VC: 2% by mass or more and 13% by mass or less (2~13%) (totaling 100%).

[0126] When the proportions of TEG, DEE, and EC contained in the non-aqueous solvent are within the above range, the protection of Li ions is achieved by solvating Li ions with DEE.

[0127] Within the aforementioned range, the VC content is preferably between 2.5% by mass and 10% by mass (2.5 to 10%), more preferably between 5.0% by mass and 7.5% by mass (5.0 to 7.5%). The upper limit for the content of TEG and DEE is preferably 48.25% by mass or less, more preferably 48% by mass or less.

[0128] When the VC content is between 2% by mass and 13% by mass, even when subjected to heating during reflow soldering, the thickness change of the receiving container 2, consisting of the positive electrode container 10 and the negative electrode container 20, is small, thus reducing the increase in internal resistance. Furthermore, when the VC content is between 2.5% by mass and 10.0% by mass, even when subjected to heating during reflow soldering, the thickness change of the receiving container 2 can be further reduced, further reducing the increase in internal resistance. Within these ranges, the VC content is most preferably between 5.0% by mass and 7.5% by mass.

[0129] Supporting salts can be known Li compounds used as supporting salts in the electrolyte of non-aqueous electrolyte secondary batteries. Examples include organic lithium acid salts such as LiCH3SO3, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiN(CF3SO3)2, and LiN(FSO2)2, as well as inorganic lithium acid salts such as LiPF6, LiBF4, LiB(C6H5)4, LiCl, and LiBr.

[0130] Among the above compounds, lithium salts that are lithium-ion conductive compounds are preferred, and LiN(CF3SO2)2, LiN(FSO2)2, and LiBF4 are more preferred. From the viewpoint of heat resistance and low reactivity with moisture, and the ability to fully utilize preservation properties, LiN(CF3SO2)2 is particularly preferred.

[0131] It should be noted that the supporting salt can be used alone or in combination with two or more of the above compounds.

[0132] The content of the supporting salt in the electrolyte 70 is determined by considering the type of supporting salt, etc., and is preferably 0.1 to 3.5 mol / L, more preferably 0.5 to 3 mol / L, and particularly preferably 1 to 2.5 mol / L.

[0133] Excessive or insufficient concentration of supporting salts in electrolyte 70 can lead to a decrease in conductivity, which may adversely affect battery characteristics.

[0134] (The role of non-aqueous electrolyte secondary batteries)

[0135] The non-aqueous electrolyte secondary battery 1 constructed as described above includes an electrolyte 70, wherein the non-aqueous solvent contains tetraethylene glycol dimethyl ether (TEG) and diethoxyethane (DEE) as the main components, and contains ethylene glycol carbonate (EC) and vinylene carbonate (VC) in appropriate amounts.

[0136] Therefore, while achieving heat resistance to withstand the heating during reflow assembly (reflow soldering), there is little risk of solvent vaporization even when subjected to the heating associated with reflow assembly. Thus, while achieving heat resistance to withstand heating, the degradation of the positive electrode 40, negative electrode 50, and electrolyte 70 can be suppressed. Furthermore, since there is little risk of solvent vaporization even when subjected to the heating associated with reflow assembly, there is less risk of pressure rise in the housing 2, allowing for the manufacture of a non-aqueous electrolyte secondary battery 1 whose housing 2 is less prone to deformation.

[0137] It should be noted that, as a solvent, if it contains dimethyl glycol ether (TEG) and diethoxyethane (DEE) as the main components, the high boiling point of these solvents can improve the heat resistance of electrolyte 70.

[0138] Based on the above, a non-aqueous electrolyte secondary battery 1 that can be manufactured to withstand reflux installation can be produced.

[0139] Furthermore, in the non-aqueous electrolyte secondary battery 1 according to this embodiment, while specifying the so-called shoulder height (H2 / H1) within the range of 74% to 79%, the positive electrode can 10 and the negative electrode can 20 are fixed together via a gasket 30 using a slit portion 12b with a radius of curvature R within the range of 0.7 mm to 1.1 mm. Therefore, the negative electrode can 20 can be securely pressed in while appropriately compressing the gasket 30.

[0140] It should be noted that if the non-aqueous electrolyte secondary battery 1 is subjected to heating equivalent to reflow soldering, causing a portion of the solvent constituting the electrolyte 70 to vaporize and the internal pressure of the storage container 2 to rise, the storage container 2 may deform due to the increased internal pressure. In this case, the sealing structure of the storage container 2 changes with the deformation, and there is a risk of the electrolyte 70 leaking to the outside of the storage container 2.

[0141] In this case, when the radius of curvature R of the converging slit 12b is smaller than 0.7 mm, the converging slit 12b is concentrated in the area around the opening end of the outer wall portion 12. In this case, although the negative electrode can 20 and the gasket 30 can be pressed forcefully toward the bottom wall portion 11 of the positive electrode can 10, the force that presses the negative electrode can 20 and the gasket 30 toward the center of the storage container 2 is weakened.

[0142] Therefore, gaps can easily form between the positive electrode container 10 or the negative electrode container 20 and the gasket 30. When subjected to heating equivalent to a reflow installation, there is a risk of electrolyte 70 leaking to the outside of the receiving container 2. As a result, leakage (including evaporation of electrolyte 70) or moisture intrusion may occur, leading to a decrease in cycle characteristics or long-term shelf life.

[0143] Conversely, when the radius of curvature R of the converging portion 12b is larger than 1.1 mm, the converging portion 12b is formed in a wide area of ​​the outer wall portion 12. In this case, although the force pressing the negative electrode can 20 and the gasket 30 towards the center of the receiving container 2 becomes stronger, the force pressing the negative electrode can 20 and the gasket 30 towards the bottom wall portion 11 of the positive electrode can 10 becomes weaker. Therefore, in this case, gaps are also easily generated between the positive electrode can 10 or the negative electrode can 20 and the gasket 30, resulting in the same undesirable situation as described above.

[0144] Furthermore, when the shoulder height (H2 / H1) is less than 74%, stress concentration occurs on the lower end 22a side of the inner wall 22 of the negative electrode can 20 during sealing (sealing). This easily leads to bulging deformation, such as the top wall 21 of the negative electrode can 20 expanding upwards. Consequently, this results in poor appearance and ultimately, product defects.

[0145] Conversely, when the shoulder height (H2 / H1) is greater than 79%, sufficient stress cannot be provided to the negative electrode can 20 during sealing, resulting in a gap between the positive electrode can 10 or the negative electrode can 20 and the gasket 30, thus causing the aforementioned defects.

[0146] In contrast, in the non-aqueous electrolyte secondary battery 1 of the present invention, the shoulder height (H2 / H1) is in the range of 74% to 79%, and the radius of curvature R of the slit portion 12b is in the range of 0.7 mm to 1.1 mm. Therefore, it is difficult to produce the above-mentioned various adverse conditions, and a non-aqueous electrolyte secondary battery 1 with excellent leakage resistance, cycle characteristics, and long-term storage properties can be manufactured.

[0147] Therefore, even with miniaturization to a diameter D of approximately 4 mm (within the range of 4.6 mm to 5.0 mm), leakage resistance can be maintained. Thus, a user-friendly, non-aqueous electrolyte secondary battery with improved operational reliability can be manufactured.

[0148] Furthermore, during reflow installation, even when the internal pressure rises due to exposure to high temperatures such as 260°C, as mentioned above, the leakage resistance is excellent, thus maintaining excellent circulation characteristics and long-term preservation even after reflow.

[0149] Based on the above, a small non-aqueous electrolyte secondary battery 1 can be manufactured that can be reflowed, has excellent leakage resistance even when exposed to high temperature environments, and has excellent cycle characteristics and long-term storage properties.

[0150] It should be noted that the radius of curvature R of the slit portion 12b is preferably within the range of 0.8 mm to 1.0 mm. In this case, the formation of gaps between the positive electrode can 10 or the negative electrode can 20 and the gasket 30 can be effectively suppressed, making leakage or moisture intrusion less likely. Therefore, while exhibiting superior leakage resistance, the battery capacity can be maintained stably over a long period of time. Example

[0151] Next, regarding the non-aqueous electrolyte secondary battery involved in this invention, in actual trial production... Figure 1 and Figure 2 After the non-aqueous electrolyte secondary battery 1 with the structure shown was subjected to the evaluation test described later, the following description is given for the embodiment that confirmed the above-mentioned effects.

[0152] In conducting this evaluation test, a non-aqueous electrolyte secondary battery 1 was fabricated under the following conditions.

[0153] First, as the positive electrode 40, in commercially available lithium manganese oxide (Li 1.14 Co 0.06 Mn 1.80In O4), a positive electrode mixture is prepared by mixing graphite as a conductive additive and polyacrylic acid as a binder in the following proportions:

[0154] • The ratio is “lithium manganese oxide:graphite:polyacrylic acid = 95:4:1 (mass ratio)”.

[0155] Then, by using 2ton / cm 2 The above-mentioned positive electrode mixture of 16.4 mg was pressurized and molded into disc-shaped granules with a diameter of 2.8 mm.

[0156] Next, the obtained granules (positive electrode 40) are bonded to the inner surface of a stainless steel (SUS329J4L: thickness t=0.20mm) positive electrode can 10 using a carbon-containing conductive resin adhesive to integrate them into a positive electrode unit. The positive electrode unit is then subjected to reduced pressure heating and drying in atmospheric conditions at 120°C for 11 hours. Finally, a sealant is applied to the inner surface of the outer wall 12 of the positive electrode can 10.

[0157] Next, as the negative electrode 50, SiO powder with carbon (C) formed on its entire surface is prepared and used as the negative electrode active material. Then, a negative electrode mixture is prepared by mixing graphite as a conductive agent and polyacrylic acid as a binder in the following proportions:

[0158] • The ratio of SiO powder: graphite: polyacrylic acid is 75:20:5 (mass ratio).

[0159] Then, by using 2ton / cm 2 The above-mentioned negative electrode mixture of 3.1 mg was pressurized and molded into disc-shaped granules with a diameter of 2.8 mm.

[0160] Next, the obtained granules (negative electrode 50) are bonded to the inner surface of a negative electrode can 20 made of stainless steel (SUS316L: thickness t=0.20mm) using a conductive resin binder with carbon as a conductive filler, to integrate them into a negative electrode unit. Then, the negative electrode unit is dried under reduced pressure at 160°C for 11 hours in atmospheric conditions. Next, lithium foil stamped to a diameter of 2.8mm and a thickness of 0.44mm is pressed onto the granular negative electrode 50 to form a lithium-negative electrode stack.

[0161] As described above, in this evaluation test, a non-aqueous electrolyte secondary battery 1 was manufactured in a state where the positive electrode current collector 41 and the negative electrode current collector 51 shown in the above embodiment were not provided, but the positive electrode container 10 had the function of the positive electrode current collector 41 and the negative electrode container 20 had the function of the negative electrode current collector 51. It should be noted that this does not affect the results of this evaluation test.

[0162] Next, after drying the nonwoven fabric made of glass fiber, it is stamped into a disc shape with a diameter of 3.6 mm to form a separator 60. Then, the separator 60 is placed on the lithium foil pressed onto the negative electrode 50, and a gasket 30 made of PEEK resin (polyether ether ketone resin) is placed at the opening of the negative electrode can 20.

[0163] (Electrolyte preparation)

[0164] As electrolyte 70, a non-aqueous solvent is prepared by mixing tetraethylene glycol dimethyl ether (TEG), diethoxyethane (DEE), ethylene glycol carbonate (EC), and vinylene carbonate (VC). Then, electrolyte 70 is obtained by dissolving LiTFSI (1M) as a supporting salt in the obtained non-aqueous solvent.

[0165] The mixing ratio of the solvents at this point, in volume ratio, is TEG:DEE:EC:VC = 44.8:42.7:5.0:7.5.

[0166] Next, in the positive electrode container 10 and negative electrode container 20 prepared as described above, fill each battery with a total of 7 μL of electrolyte 70 adjusted according to the above procedure.

[0167] Next, the negative electrode unit and the positive electrode unit are combined by contacting the separator 60 with the positive electrode 40. Then, the positive electrode tank 10 and the negative electrode tank 20 are sealed by closing the slit 12b of the positive electrode tank 10. Then, a sample battery (non-aqueous electrolyte secondary battery 1) for evaluation test is made by standing at 25°C for 7 days.

[0168] It should be noted that, as shown in Table 1, seven sample cells with different radii of curvature R of the converging slit 12b were fabricated during the preparation of the sample cells. Specifically, a total of seven sample cells were fabricated with radii of curvature R varying at 0.1 mm intervals and within the range of 0.6 mm to 1.2 mm.

[0169] In this invention, a sample battery with a radius of curvature R of 0.7 mm (0.7 mm to 1.1 mm, which is within the scope of this invention) was used as Example 1; a sample battery with R of 0.8 mm was used as Example 2; a sample battery with R of 0.9 mm was used as Example 3; a sample battery with R of 1.0 mm was used as Example 4; and a sample battery with R of 1.1 mm was used as Example 5. Additionally, a sample battery with a radius of curvature R of 0.6 mm (outside the scope of this invention) was used as Comparative Example 1; and a sample battery with R of 1.2 mm was used as Comparative Example 2.

[0170] [Table 1]

[0171] The radius of curvature R (mm) of the seam. Leakage rate Initial capacity (mAh) Capacity maintenance rate Comparative Example 1 0.6 5.0% 1.51 48% Example 1 0.7 0% 1.50 52% Example 2 0.8 0% 1.53 63% Example 3 0.9 0% 1.52 67% Example 4 1.0 0% 1.49 69% Example 5 1.1 0% 1.50 58% Comparative Example 2 1.2 1.7% 1.51 52%

[0172] It should be noted that the diameter D of the above 7 sample batteries is set to 4.8 mm, which is within the range of the invention in this application (4.6 mm to 5.0 mm). In addition, the battery height H1 is set to 2.1 mm.

[0173] Furthermore, during this evaluation test, with the radius of curvature R of the slit section 12b being 0.9 mm, as shown in Table 2, five sample cells with different ratios of so-called shoulder height (H2 / H1) were prepared.

[0174] Specifically, a total of five sample batteries were fabricated with a shoulder height (H2 / H1) ratio ranging from 71% to 81%. Among them, a sample battery with a shoulder height (H2 / H1) ratio of 74% (74% to 79%), which is within the scope of this invention, was designated Example 6; a sample battery with a shoulder height of 76% was designated Example 7; and a sample battery with a shoulder height of 79% was designated Example 8. Additionally, a sample battery with a shoulder height (H2 / H1) ratio of 71% (outside the scope of this invention) was designated Comparative Example 3; and a sample battery with a shoulder height of 81% was designated Comparative Example 4.

[0175] [Table 2]

[0176] Shoulder height (H2 / H1) ratio (%) Height H2 (mm) of the positive electrode container Leakage rate Incidence of bulging deformation Comparative Example 3 71 1.50 0% 30% Example 6 74 1.55 0% 0% Example 7 76 1.60 0% 0% Example 8 79 1.65 0% 0% Comparative Example 4 81 1.70 20% 0%

[0177] (Evaluation Test)

[0178] For the above-mentioned sample batteries (Examples 1 to 8, Comparative Examples 1 to 4), heating under reflux conditions was performed, and the appearance after heating was observed. By performing this observation, it was confirmed whether leakage occurred and whether bulging deformation occurred in the top wall 21 of the negative electrode tank 20.

[0179] In addition, the battery capacity is measured again after a certain period of time while the battery capacity is being heated (initial capacity) to calculate the capacity retention rate.

[0180] Specifically, for the seven sample batteries shown in Table 1 (Examples 1-5, Comparative Examples 1 and 2), each was heated at 260°C for 10 seconds. At this time, 60 of each sample battery were prepared and heated. Then, all 60 sample batteries were visually inspected, and the number of sample batteries from which electrolyte 70 leaked was measured to determine the leakage rate (%).

[0181] It should be noted that the heating treatment at 260°C for 10 seconds is equivalent to the heating conditions associated with reflow installation (reflow soldering).

[0182] The results of the measured leakage rates are shown in Table 1 and... Figure 3In addition, the results obtained by measuring the initial capacity (mAh) after heating are also shown in Table 1 and... Figure 3 middle.

[0183] Furthermore, after the aforementioned heating, each sample battery was stored in a constant temperature bath at 80°C and 90% relative humidity for 480 hours, and the battery capacity was measured again. Then, by comparing the measured capacity with the initial capacity, the capacity retention rate (%) was calculated. This allows confirmation of the degree of degradation of non-aqueous electrolyte secondary batteries under high temperature and high humidity conditions.

[0184] The calculated capacity maintenance rates are shown in Table 1 and... Figure 3 middle.

[0185] In addition, for the five sample batteries of Examples 6-8 and Comparative Examples 3 and 4 shown in Table 2, they were heated at 260°C for 10 seconds in the same manner as described above. At this time, 20 of each sample battery were prepared and heated. Then, all 20 sample batteries were visually inspected, and the leakage rate (%) was calculated in the same manner as described above. In addition, after visually confirming whether bulging deformation occurred, the bulging deformation rate (%) was calculated.

[0186] The results of these measured leakage rates and bulging deformation rates are shown in Table 2 and... Figure 4 middle.

[0187] As shown in Table 1 and Figure 3 As shown, in the case of the sample batteries of Examples 1 to 5 where the radius of curvature R of the slit portion 12b is within the range of the present invention (0.7 mm to 1.1 mm), it can be confirmed that not only did no leakage occur, but the capacity retention rate after storage under high temperature and high humidity conditions exceeded 50%. Therefore, it can be confirmed that the sample batteries of Examples 1 to 5 are non-aqueous electrolyte secondary batteries with excellent leakage resistance, excellent cycle characteristics, and excellent long-term storage performance.

[0188] In particular, in the case of the sample batteries of Examples 2 to 4, where the radius of curvature R is within the range of 0.8 mm to 1.0 mm, it can be confirmed that the capacity retention rate after storage under high temperature and high humidity conditions exceeds 60%. Thus, it can be practically confirmed that these are non-aqueous electrolyte secondary batteries that can further maintain battery capacity.

[0189] In contrast, in the case of the sample batteries of Comparative Examples 1 and 2, where the radius of curvature R of the slit portion 12b is outside the scope of the present invention (0.7 mm to 1.1 mm), it can be confirmed that not only does leakage occur, but the capacity retention rate also tends to be less than 50%.

[0190] In addition, as shown in Table 2 and Figure 4 As shown, in the case of the sample batteries of Examples 6-8, where the shoulder height (H2 / H1) ratio is within the range of the present invention (74%~79%), it can be confirmed that not only did no leakage occur, but no bulging deformation also occurred. Therefore, it can be practically confirmed that the sample batteries of Examples 6-8 are non-aqueous electrolyte secondary batteries with excellent leakage resistance, excellent cycle characteristics, and excellent long-term storage properties.

[0191] In contrast, in the case of the sample batteries of Examples 3 and 4, where the shoulder height (H2 / H1) ratio is outside the scope of the present invention (74%~79%), it can be confirmed that leakage and bulging deformation actually occurred.

[0192] The embodiments of the present invention have been described above, but these embodiments are shown as examples and are not intended to limit the scope of the invention. Embodiments may be implemented in various other ways, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Embodiments or variations thereof may include, for example, embodiments readily conceived by those skilled in the art, substantially the same embodiments, embodiments of equivalent scope, etc.

[0193] Industrial availability

[0194] According to the present invention, a small non-aqueous electrolyte secondary battery exhibiting excellent leakage resistance even when exposed to high-temperature environments, as well as excellent cycle characteristics and long-term storage properties, can be obtained. Therefore, it has industrial applicability.

[0195] Symbol Explanation

[0196] D…Diameter of non-aqueous electrolyte secondary battery

[0197] R…radius of curvature of the suture section

[0198] H1… Height of non-aqueous electrolyte secondary battery

[0199] H2… Height of the positive electrode container

[0200] 1…Non-aqueous electrolyte secondary battery

[0201] 2… Storage Containers

[0202] 3…Power generation components

[0203] 10… Positive electrode container

[0204] 11...Bottom wall part

[0205] 12…Outer wall section

[0206] 12b… Seam gathering section

[0207] 20… Negative electrode container

[0208] 21…top wall part

[0209] 22…Inner wall part

[0210] 30… Washer

[0211] 60…diaphragm

[0212] 70… Electrolyte.

Claims

1. A non-aqueous electrolyte secondary battery with reflux mounting, possessing: The storage container has a positive electrode can and a negative electrode can fixed to the positive electrode can via a gasket seam. A power generation element containing an electrolyte is housed inside the housing container. The non-aqueous electrolyte secondary battery is characterized in that... The positive electrode can is formed into a bottomed cylindrical shape, having a bottom wall portion and an outer wall portion formed along the outer periphery of the bottom wall portion. The negative electrode can is formed into a top cylindrical shape, having a top wall portion and an inner wall portion formed along the outer periphery of the top wall portion and disposed on the inner side of the outer wall portion. The portion of the outer wall located on the top wall side is a converging section, which bends with a radius of curvature R from the opening edge of the bottom wall towards the inner wall side. The diameter D of the non-aqueous electrolyte secondary battery is 4.8 mm. The height H1 of the non-aqueous electrolyte secondary battery is 2.1 mm. The height H2 of the positive electrode container is in the range of 74% to 76% relative to the height H1 of the non-aqueous electrolyte secondary battery. The radius of curvature R of the converging slit is 0.9 mm. Under the heating condition of heating the non-aqueous electrolyte secondary battery at 260°C for 10 seconds, the top wall of the negative electrode tank does not bulge upwards, and the storage container does not change its sealed structure due to the increase in internal pressure.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The power generation element includes: The positive electrode, disposed on the side of the positive electrode can, contains spinel-type lithium manganese oxide as the positive electrode active material. The negative electrode, disposed on the side of the negative electrode can, contains carbon-coated SiOx as the negative electrode active material, where 0 < x < 2, and A diaphragm is disposed between the positive electrode and the negative electrode; The electrolyte contains a mixed solvent, which is a glycol dimethyl ether solvent containing ethylene glycol ester (EC) and vinylene carbonate (VC).

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