Non-aqueous electrolyte secondary battery and method for manufacturing the same

Abstract

To provide a nonaqueous electrolyte secondary battery having excellent heat resistance to withstand heating such as reflow soldering.SOLUTION: In a nonaqueous electrolyte secondary battery of the present invention, a positive electrode body, a negative electrode body, an electrolytic solution including a supporting salt and a solvent, and a separator are housed in a housing container comprising a positive electrode can and a negative electrode can. The positive electrode body is housed on one side of the housing container via the separator, and the negative electrode is housed on the other side of the housing container. The supporting salt concentration of the electrolytic solution in the housing container on a positive electrode body housing side is different from the supporting salt concentration of the electrolytic solution in the housing container on a negative electrode body housing side, and the supporting salt concentration on the positive electrode body housing side is higher than the supporting salt concentration on the negative electrode body housing side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the same. [Background technology]

[0002] In recent years, small non-aqueous electrolyte secondary batteries have required reflow soldering to improve the efficiency of soldering when mounted on circuit boards. Conventionally, various configurations have been provided for small non-aqueous electrolyte secondary batteries that use a combination of a positive electrode active material such as lithium manganese oxide and a negative electrode active material such as a lithium alloy, allowing for reflow soldering. For example, in the non-aqueous electrolyte secondary battery described in Patent Document 1, the problem is solved by adjusting the solute concentration of the electrolytic solution to a specific range, thereby suppressing the reactivity between the metal oxide and the electrolyte at high temperatures during reflow soldering. Furthermore, the non-aqueous electrolyte secondary battery described in Patent Document 2 below employs a configuration in which two types of electrolytes that do not mix with each other are used, with a highly oxidation-resistant electrolytic solution as the electrolyte on the positive electrode side and a highly reduction-resistant electrolyte as the electrolyte on the negative electrode side, thereby suppressing oxidation or reduction decomposition and thus suppressing battery degradation. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2004-327282 [Patent Document 2] Japanese Patent Publication No. 2020-177890 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, in the non-aqueous electrolyte secondary battery described in Patent Document 1 above, the lithium salt concentration of the electrolyte is specified to 1.5 to 2.5 mol / L, and the reflow soldering problem is solved by increasing the amount of lithium ions or anions in the electrolyte. According to the technology described in Patent Document 1, the reactivity between the metal oxide used as the positive electrode active material and the electrolyte can be reduced in the high-temperature environment during reflow soldering, which is believed to suppress the degradation of battery performance. However, increasing the salt concentration of the electrolyte can lead to increased conductivity of the electrolyte, which in turn increases the internal resistance of the battery and may cause deterioration of the battery's characteristics.

[0005] In view of the above-mentioned problems, the present invention aims to provide a non-aqueous electrolyte secondary battery and a method for manufacturing the same that can prevent deterioration of battery characteristics associated with reflow soldering and prevent deterioration of battery characteristics due to increased battery resistance resulting from a higher concentration of the electrolyte. [Means for solving the problem]

[0006] "1" In order to solve the above problem, a non-aqueous electrolyte secondary battery according to one embodiment of the present invention is a non-aqueous electrolyte secondary battery in which a positive electrode, a negative electrode, an electrolyte containing a support salt and a solvent, and a separator are housed in a housing container composed of a positive electrode container and a negative electrode container, wherein the positive electrode is housed on one side of the housing container via the separator, and the negative electrode is housed on the other side of the housing container, and the support salt concentration of the electrolyte on the side of the housing container where the positive electrode is housed is different from the support salt concentration of the electrolyte on the side of the housing container where the negative electrode is housed, and the support salt concentration on the side where the positive electrode is housed is higher than the support salt concentration on the side where the negative electrode is housed The support salt concentration on the positive electrode housing side is 2 to 3 mol / L, the support salt concentration on the negative electrode housing side is 0.5 to 1 mol / L, and the separator is a separator that allows mutual diffusion between the components of the electrolyte on the positive electrode housing side and the components of the electrolyte on the negative electrode housing side. It is characterized by the following:

[0007] When the concentration of supporting salts in the electrolyte is high on the side containing the positive electrode and low on the side containing the negative electrode, the amount of ions or anions in the electrolyte surrounding the positive electrode increases. This allows for a chemical equilibrium-based reduction in the amount of ions released from the positive electrode into the electrolyte, even in the high-temperature environment created by heating during reflow soldering. This prevents battery performance degradation due to heating during reflow soldering. In non-aqueous electrolyte secondary batteries for reflow applications, the reflow process is performed within a certain period after battery assembly. If the support salt concentration on the positive electrode side is high and the support salt concentration on the negative electrode side is low during the reflow process, then, as described above, degradation of battery performance can be prevented. Even if there is a difference in the support salt concentration between the positive electrode housing and the negative electrode housing during the assembly of a non-aqueous electrolyte secondary battery, the difference in support salt concentration will eventually be eliminated due to the heat generated during reflow and the passage of time, resulting in a uniform support salt concentration. This allows for a uniform support salt concentration after reflow or after a period of time, thereby sufficiently lowering the electrolyte resistance and preventing degradation of battery characteristics.

[0008] "2" In the above-mentioned non-aqueous electrolyte secondary battery, The separator is an ion-permeable separator with a thickness of 5 to 300 μm, and after joining the positive electrode can and the negative electrode can, the separator has the function of adjusting the support salt concentration of the electrolyte on the positive electrode side to a range of 0.7 to 1.5 mol / L, and the support salt concentration of the electrolyte on the negative electrode side to a range of 0.7 to 1.5 mol / L. It is preferable.

[0009] In this embodiment, by setting the support salt concentration on the positive electrode side to 2-3 mol / L and the support salt concentration on the negative electrode side to 0.5-1 mol / L, it is possible to reliably prevent battery performance degradation during reflow, and after reflow or after a sufficient amount of time has elapsed, the desired support salt concentration is reached, resulting in excellent battery performance.

[0010] "3" In the above-described embodiment of the non-aqueous electrolyte secondary battery, it is preferable that the positive electrode can is a bottomed cylindrical shape, the negative electrode can is fixed to the inside of the opening of the positive electrode can with a gasket interposed therebetween, and the housing container is sealed by providing a crimped portion on the negative electrode can side of the opening of the positive electrode can.

[0011] In this embodiment, a button-type non-aqueous electrolyte secondary battery with a sealed structure is provided, in which a crimped portion is provided between the negative electrode can and the positive electrode can via a gasket. Furthermore, this non-aqueous electrolyte secondary battery exhibits minimal capacity reduction after reflow soldering, excellent capacity retention, and low electrolyte resistance, making it less susceptible to degradation of battery characteristics.

[0012] "4" A method for manufacturing a non-aqueous electrolyte secondary battery according to one embodiment of the present invention is a method for manufacturing a non-aqueous electrolyte secondary battery in which a positive electrode, a negative electrode, an electrolyte containing a support salt and a solvent, and a separator are housed in a housing container formed by joining a positive electrode container and a negative electrode container, wherein when housing the positive electrode, the negative electrode, the electrolyte, and the separator in the housing container, the support salt concentration of the electrolyte on the positive electrode side is set higher than the support salt concentration of the electrolyte on the negative electrode side. The support salt concentration on the positive electrode housing side is set to 2-3 mol / L, and the support salt concentration on the negative electrode housing side is set to 0.5-1 mol / L. The separator used is one that allows the components of the electrolyte on the positive electrode housing side and the components of the electrolyte on the negative electrode housing side to mutually diffuse through the separator. It is characterized by the following:

[0013] By making the support salt concentration in the electrolyte on the positive electrode side higher than that on the negative electrode side, the amount of ions or anions in the electrolyte surrounding the positive electrode increases. This reduces the amount of ions released from the positive electrode into the electrolyte, even in the high-temperature environment caused by heating during reflow soldering, according to chemical equilibrium theory. This makes it possible to provide a non-aqueous electrolyte secondary battery that can prevent battery performance degradation due to heating during reflow soldering. In non-aqueous electrolyte secondary batteries for reflow applications, the reflow process is performed within a certain period after battery assembly. If the support salt concentration on the positive electrode housing side is high and the support salt concentration on the negative electrode housing side is low during the reflow process, a non-aqueous electrolyte secondary battery can be provided that prevents battery performance degradation as described above. Even if there is a difference in the support salt concentration between the positive electrode housing side and the negative electrode housing side during the assembly of a non-aqueous electrolyte secondary battery, the difference in support salt concentration will eventually be eliminated due to the heat generated during reflow and the passage of time, resulting in a uniform support salt concentration. This makes it possible to uniformize the support salt concentration after reflow or after a period of time, and to provide a non-aqueous electrolyte secondary battery with sufficiently low electrolyte resistance to prevent deterioration of battery characteristics.

[0014] "5" In a method for manufacturing a non-aqueous electrolyte secondary battery according to one embodiment of the present invention, Preferably, the separator used is an ion-permeable separator with a thickness of 5 to 300 μm, which, after the positive electrode can and the negative electrode can are joined together, has the function of adjusting the support salt concentration of the electrolyte on the positive electrode housing side to a range of 0.7 to 1.5 mol / L, and the support salt concentration of the electrolyte on the negative electrode housing side to a range of 0.7 to 1.5 mol / L.

[0015] In this embodiment, by setting the supporting salt concentration on the positive electrode body accommodating side to 2 to 3 mol / L and the supporting salt concentration on the negative electrode body accommodating side to 0.5 to 1 mol / L, it is possible to reliably prevent deterioration of battery performance during reflow, and to provide a non-aqueous electrolyte secondary battery that can achieve a desirable supporting salt concentration after reflow or after a sufficient period of time has elapsed and exhibit excellent battery performance.

[0016] "6" In the method for manufacturing a non-aqueous electrolyte secondary battery according to an embodiment of the present invention, the positive electrode can is bottomed cylindrical, the negative electrode can is fixed inside the opening of the positive electrode can with a gasket interposed therebetween, and it is preferable to seal the housing container by providing a caulked portion obtained by caulking the opening of the positive electrode can toward the negative electrode can side.

[0017] In this embodiment, it is possible to provide a button-type non-aqueous electrolyte secondary battery having a sealed structure with a caulked portion provided between the negative electrode can and the positive electrode can via a gasket. Further, it is possible to provide a non-aqueous electrolyte secondary battery with little capacity decrease after reflow soldering, excellent capacity retention rate, low resistance of the electrolyte solution, and little deterioration of battery characteristics.

Effect of the Invention

[0018] According to this embodiment, it is possible to provide a non-aqueous electrolyte secondary battery that can cope with reflow soldering and prevent deterioration of battery characteristics.

Brief Description of the Drawings

[0019] [Figure 1] It is a cross-sectional view showing a non-aqueous electrolyte secondary battery according to the first embodiment.

Modes for Carrying Out the Invention

[0020] Hereinafter, an example of a non-aqueous electrolyte secondary battery which is an embodiment of the present invention will be given, and its configuration will be described in detail while referring to FIG. 1. Note that the non-aqueous electrolyte secondary battery described in the present invention is a secondary battery in which an active material used as a positive electrode or a negative electrode and a separator are housed in a housing container. Further, in the drawings used in the following description, the scale of each member is appropriately changed and shown in order to make each member recognizable in size.

[0021] [First Embodiment of a Non-Aqueous Electrolyte Secondary Battery] The non-aqueous electrolyte secondary battery 1 of this embodiment shown in Figure 1 is a so-called coin (button) type battery. This non-aqueous electrolyte secondary battery 1 comprises a bottomed cylindrical metal positive electrode can 12, a lidded cylindrical metal negative electrode can 22 that closes the opening of the positive electrode can 12, and a gasket 40 provided along the inner circumferential surface of the positive electrode can 12. The non-aqueous electrolyte secondary battery 1 includes a thin (flat) housing container 2, which is constructed by placing a positive electrode container 12 on the outside of a negative electrode container 22 via a gasket 40, and crimping the inner peripheral edge of the opening of the positive electrode container 12 inward. Inside the housing container 2, a housing space is formed surrounded by the positive electrode container 12 and the negative electrode container 22, and a positive electrode body 10 and a negative electrode body 20 are placed facing each other in this housing space via a separator 30, and the housing is further filled with electrolyte 50.

[0022] Conventional known materials can be used as the material for the positive electrode can 12, such as stainless steel like SUS316L or SUS329J4L. The material of the negative electrode canister 22 is the same as the material of the positive electrode canister 12, and includes conventionally known stainless steels such as SUS316L, SUS329J4L, or SUS304-BA. Alternatively, a clad material made by crimping copper or nickel onto stainless steel can also be used for the negative electrode canister. The outer diameter of the containment container 2 is typically around 4 to 12 mm.

[0023] (Positive pole) In this embodiment, the positive electrode body 10 is electrically connected to the inner surface of the positive electrode can 12 (the upper surface of the bottom wall of the housing container 2 in Figure 1) via the positive electrode current collector 14, and the negative electrode body 20 is electrically connected to the inner surface of the negative electrode can 22 (the lower surface of the ceiling wall of the housing container 2 in Figure 1) via the negative electrode current collector 24. Alternatively, the positive electrode current collector 14 and the negative electrode current collector 24 may be omitted, and the positive electrode body 10 may be directly connected to the positive electrode can 12 to give the positive electrode can 12 the function of a current collector, or the negative electrode body 20 may be directly connected to the negative electrode can 22 to give the negative electrode can 22 the function of a current collector. The gasket 40 is connected to the outer edge of the separator 30 inside the containment container 2, and the gasket 40 holds the separator 30 in place. The positive electrode 10, the negative electrode 20, and the separator 30 are impregnated with the electrolyte 50 filled inside the containment container 2.

[0024] In the positive electrode body 10, the type of positive electrode active material is not particularly limited, but for example, it is preferable to use one that contains spinel-type lithium manganese oxide as the positive electrode active material. The content of the positive electrode active material in the positive electrode body 10 is determined considering the required discharge capacity of the non-aqueous electrolyte secondary battery 1, and can be in the range of 50 to 95% by mass. If the content of the positive electrode active material is above the lower limit of the above preferred range, a sufficient discharge capacity is easily obtained, and if it is below the preferred upper limit, the positive electrode body 10 is easy to mold. The positive electrode body 10 may contain a binder (hereinafter, the binder used in the positive electrode body 10 may be referred to as the "positive electrode binder").

[0025] Conventionally known materials can be used as the positive electrode binder, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethylcellulose (CMC), and polyvinyl alcohol (PVA). Binders composed of combinations of these materials can also be used. Furthermore, the positive electrode binder may be one of the above types used alone, or two or more types may be used in combination. The content of the positive electrode binder in the positive electrode body 10 can be, for example, 1 to 20% by mass. In this specification, when "~" is used to indicate an upper and lower limit for a numerical range, it refers to the range including both the upper and lower limits unless otherwise specified. Therefore, for example, when it says 1~20 mass%, it means 1 mass% or more and 20 mass or less. The positive electrode current collector 14 can be a conventionally known type, and examples include conductive resin adhesives using carbon as a conductive filler.

[0026] Furthermore, in this embodiment, in addition to the lithium manganese oxide described above, the positive electrode active material may also contain other positive electrode active materials. For example, it may contain one or more other metal oxides such as molybdenum oxide, lithium iron phosphate compounds, lithium cobalt oxide, lithium nickel oxide, vanadium oxide, etc.

[0027] (Negative electrode) In the negative electrode body 20, the type of negative electrode active material is not particularly limited, but it is preferable, for example, to include silicon oxide as the negative electrode active material. In the negative electrode body 20, the negative electrode active material is carbon-coated SiO X For example, SiO X It is preferable that the material consists of a silicon oxide represented by (0 ≤ x < 2) coated with carbon.

[0028] Furthermore, the negative electrode 20 uses the above-mentioned SiO as the negative electrode active material. X In addition to (0≦x<2), other negative electrode active materials may be included, such as Si, C, etc. Granular SiO2 is used as the negative electrode active material. X When using (0≦x<2), these particle sizes (D50) are 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. SiO X If the particle size (D50) is below the lower limit of the above range, for example, if the non-aqueous electrolyte secondary battery 1 is stored and used in a harsh high-temperature and high-humidity environment, or if reflow soldering is performed, the reactivity may increase and the battery characteristics may be impaired. If it exceeds the upper limit, the discharge rate may decrease.

[0029] The negative electrode active material in the negative electrode body 20 is, i.e., SiO X The content of (0≦x<2) is determined considering the required discharge capacity of the non-aqueous electrolyte secondary battery 1, and a range of 50% by mass or more can be selected, with a range of 60-70% by mass being preferable. In the negative electrode body 20, if the content of the negative electrode active material consisting of the above elements is above the lower limit of the above range, a sufficient discharge capacity can be easily obtained, and if it is below the upper limit, the negative electrode body 20 can be easily molded.

[0030] The negative electrode 20 may contain a conductive additive (hereinafter, the conductive additive used in the negative electrode 20 may be referred to as the "negative electrode conductive additive"). The negative electrode conductive additive is the same as the positive electrode conductive additive. The negative electrode 20 may contain a binder (hereinafter, the binder used in the negative electrode 20 may be referred to as the "negative electrode binder"). As the negative electrode binder, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethylcellulose (CMC), polyimide (PI), polyamide-imide (PAI), etc., can be selected.

[0031] Furthermore, the negative electrode binder may be one of the above types used alone, or two or more types may be used in combination. When using polyacrylic acid as the negative electrode binder, the polyacrylic acid can be pre-adjusted to a pH of approximately 3 to 10. In this case, alkali metal hydroxides such as lithium hydroxide or alkaline earth metal hydroxides such as magnesium hydroxide can be used to adjust the pH. The content of the negative electrode binder in the negative electrode body 20 is, for example, in the range of 1 to 20 mass%.

[0032] In this embodiment, the size and thickness of the negative electrode 20 can be formed in the same way as the size and thickness of the positive electrode 10. Furthermore, in the non-aqueous electrolyte secondary battery 1 shown in Figure 1, although not shown in the illustration, a configuration can be adopted in which a lithium material 60, such as lithium foil, is provided on the surface of the negative electrode 20, that is, between the negative electrode 20 and the separator 30 described later.

[0033] "Electrolyte" The electrolyte 50 is typically a liquid obtained by dissolving a support salt in a non-aqueous solvent. The conductivity of the electrolyte affects the internal resistance of the battery. Therefore, in order to reduce the internal resistance of the battery, it is generally preferable to use a support salt concentration of 0.5 to 1.0 mol / L that maximizes conductivity. The inventors investigated various solvents and solutes and discovered that by increasing the support salt concentration above the normally used concentration, the reaction between the electrolyte and lithium-containing manganese oxide during reflow soldering is suppressed, resulting in good reflow heat resistance.

[0034] In the structure of this embodiment, when the battery is assembled, the electrolyte 50 filled in the housing container 2 has a support salt concentration of 2 to 3 mol / L in the electrolyte 50A on the positive electrode housing side and a support salt concentration of 0.5 to 1 mol / L in the electrolyte 50B on the negative electrode housing side. The support salt concentrations of electrolyte 50A and electrolyte 50B mentioned above are the support salt concentrations when the non-aqueous electrolyte secondary battery 1 is assembled. However, after a considerable amount of time has passed since the assembly of the non-aqueous electrolyte secondary battery 1, the components of electrolyte 50A and electrolyte 50B, which are separated by the separator 30, gradually become homogenized by diffusion, and the entire electrolyte 50 becomes homogenized. The support salt concentration of the electrolyte after this homogenization is preferably around 1.0 mol / L, for example, in the range of 0.7 to 1.5 mol / L.

[0035] The mechanism by which the reaction between the electrolyte and lithium-containing manganese oxide or molybdenum oxide during reflow soldering is suppressed when the concentration of supporting salts in the electrolyte is high is unknown. However, it is thought that increasing the concentration of supporting salts increases the amount of lithium ions or anions in the electrolyte, which in turn reduces the amount of lithium ions or oxygen ions released from lithium manganese oxide into the electrolyte in the high-temperature environment of reflow soldering, according to chemical equilibrium theory. However, as mentioned above, increasing the concentration of supporting salts in the electrolyte increases the conductivity of the electrolyte and thus the internal resistance of the battery, which may lead to deterioration of battery characteristics. Therefore, in the non-aqueous electrolyte secondary battery 1 of this embodiment, the support salt concentration of the electrolyte 50A is set to a range of 2 to 3 mol / l. In order to achieve a non-aqueous electrolyte secondary battery that can be reflow soldered, it is preferable to use the above-mentioned electrolyte 50A which has low reactivity with the positive electrode active material at the reflow temperature.

[0036] For reflow soldering, it is considered that using a non-aqueous solvent with a boiling point of 200°C or higher at atmospheric pressure as the electrolyte ensures stability at the reflow temperature. Although the reflow temperature can rise to around 260°C, no battery rupture occurred even when using γ-butyrolactone (γBL), which has a boiling point of 204°C at atmospheric pressure, possibly due to the increased internal pressure at that temperature. In combination with the positive and negative electrodes, it is considered best to use either ethylene carbonate (EC) or γ-butyrolactone (γBL) individually or in combination.

[0037] In addition to the organic solvents mentioned above, polymers can also be used. Commonly used polymers can be used, and for example, polyethylene oxide (PEO), polypropylene oxide, polyethylene glycol diacrylate crosslinked polymer, polyvinylidene fluoride, polyphosphozene crosslinked polymer, polypropylene glycol diacrylate crosslinked polymer, polyethylene glycol methyl ether acrylate crosslinked polymer, and polypropylene glycol methyl ether acrylate crosslinked polymer are preferably used. For example, a mixed solvent of ethylene carbonate (EC) and γ-butyrolactone (γBL) can be used as the organic solvent, and lithium hexafluoride phosphate (LiPF6) or lithium borofluoride (LiBF4) can be used as the supporting salt.

[0038] The supporting salt can be a known Li compound used as a supporting salt in the electrolyte of a non-aqueous electrolyte secondary battery. Examples include lithium organic acid salts such as LiCH3SO3, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiN(CF3SO3)2, and LiN(FSO2)2; and lithium inorganic acid lithium salts such as LiPF6, LiBF4, LiB(C6H5)4, LiCl, and LiBr. Among these, lithium salts that are lithium ion conductive compounds are preferred, with LiN(CF3SO2)2, LiN(FSO2)2, and LiBF4 being more preferred. LiN(CF3SO2)2 can be used because it has low heat resistance and reactivity with moisture, and can fully exhibit storage characteristics. The supporting salt may be one of the above types used alone, or two or more types may be used in combination.

[0039] (Separator) The separator 30 is interposed between the positive electrode 10 and the negative electrode 20, and is made of an insulating film that has high ion permeability and mechanical strength. The separator 30 can be any material conventionally used as a separator in non-aqueous electrolyte secondary batteries, without any limitations. Examples include nonwoven fabrics made of glass such as alkali glass, borosilicate glass, quartz glass, and lead glass, and resins such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyamide-imide (PAI), polyamide, and polyimide (PI). Among these, glass nonwoven fabrics are preferred, and borosilicate glass nonwoven fabrics are more preferred. Glass nonwoven fabrics have excellent mechanical strength and high ion permeability, which reduces internal resistance and improves discharge capacity. The thickness of the separator 30 is determined considering the size of the non-aqueous electrolyte secondary battery 1 and the material of the separator 30, and can be, for example, 5 to 300 μm.

[0040] (gasket) The gasket 40 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 for the gasket 40 is 230°C or higher, the gasket will not deform significantly due to reflow soldering or heating during use of the non-aqueous electrolyte secondary battery 1, thus preventing leakage of the electrolyte 50. As shown in Figure 1, the gasket 40 is formed in an annular shape along the inner circumferential surface of the positive electrode can 12, and the outer circumferential end 22a of the negative electrode can 22 is positioned inside the annular groove 41 of the gasket 40. The gasket 40 has a ring-shaped outer edge portion 40A with an outer diameter that is inserted without gap into the inner circumference of the opening of the positive electrode can 12. The gasket 40 has a ring-shaped inner edge portion 40B with an outer diameter that is inserted without gap into the inner circumference of the negative electrode can 22. The gasket 40 also has a bottom wall portion 40C that connects the lower ends of the outer edge portion 40A and the inner edge portion 40B. Therefore, an annular groove 41 is formed on the upper side of the outer edge of the gasket 40, into which the outer end portion 22a of the negative electrode can 22 can be inserted. By crimping the peripheral edge 12b of the opening 12a of the positive electrode can 12 shown in Figure 1 inward, i.e., toward the negative electrode can 22, the gasket 40 can be sandwiched together with the negative electrode can 22, thereby forming a storage container 2 with a sealed storage space.

[0041] Examples of materials for the gasket 40 include polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyamide, liquid crystal polymer (LCP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), polyetherether ketone resin (PEEK), polyethernitrile resin (PEN), polyether ketone resin (PEK), polyarylate resin, polybutylene terephthalate resin (PBT), polycyclohexanedimethylene terephthalate resin, polyethersulfone resin (PES), polyaminobismaleimide resin, polyetherimide resin, and fluororesin. Furthermore, materials to which glass fibers, mica whiskers, ceramic fine powder, etc., are added in an amount of 30% by mass or less can be suitably used. By using such materials, it is possible to prevent the gasket from deforming significantly due to heating and leaking the electrolyte 50.

[0042] According to the non-aqueous electrolyte secondary battery 1 of this embodiment described above, the support salt concentration of the electrolyte 50A on the positive electrode side after battery assembly is set to 2 to 3 mol / L, and the support salt concentration of the electrolyte 50B on the negative electrode side is set to 0.5 to 1 mol / L. In a non-aqueous electrolyte secondary battery 1 for reflow applications, the reflow process is performed within a certain period after battery manufacturing (after battery assembly). At the time of the reflow process, the support salt concentration of the electrolyte 50A on the positive electrode side is set to 2-3 mol / L, and the support salt concentration of the electrolyte 50B on the negative electrode side is set to 0.5-1 mol / L. Even when heat acts on the non-aqueous electrolyte secondary battery 1 during the reflow process, increasing the support salt concentration increases the amount of lithium ions or anions in the electrolyte, and the amount of lithium ions or oxygen ions released from the positive electrode active material such as lithium manganese oxide into the electrolyte in the high-temperature environment of reflow soldering decreases according to chemical equilibrium theory. As a result, the degradation of the battery performance of the non-aqueous electrolyte secondary battery 1 can be suppressed.

[0043] Next, after the non-aqueous electrolyte secondary battery 1 is mounted on the circuit board, etc., by the reflow process, the end user will only use the product, such as a mobile phone, PDA, game console, or digital camera, that has the circuit board mounted on it, after a considerable amount of time has elapsed since the reflow process. As mentioned above, the supporting salt concentrations of electrolyte 50A and electrolyte 50B are different, but after a considerable amount of time, due to the diffusion of components in the electrolyte, the supporting salt concentrations of electrolytes 50A and 50B tend to approach the same value. As mentioned above, if the supporting salt concentration of electrolyte 50A is set to 2-3 mol / L and the supporting salt concentration of electrolyte 50B is set to 0.5-1 mol / L, then after a considerable amount of time, the supporting salt concentrations of electrolytes 50A and 50B will be in the range of 0.7-1.5 mol / L or approach this range.

[0044] If the supporting salt concentrations of electrolytes 50A and 50B are in the range of 0.7 to 1.5 mol / L, then, in the case of a non-aqueous electrolyte secondary battery 1 being a lithium-ion battery, it can be said that the lithium-ion conductivity is in a good state. It is generally known that lithium-ion conductivity is maximized when the electrolyte concentration is around 1 mol / L. Therefore, if the above-described non-aqueous electrolyte secondary battery 1 is used, there is no degradation in battery performance even after the reflow process, and the non-aqueous electrolyte secondary battery 1 can be used with ideal lithium-ion conductivity when used by end users. [Examples]

[0045] A non-aqueous electrolyte secondary battery with the configuration shown in Figure 1 was fabricated, and evaluation tests described later were conducted. Li4Mn5O, which was heat-treated using lithium chloride as a flux, was used as a raw material for the positive electrode active material. 12 This case uses SiO as the negative electrode active material. The positive electrode, negative electrode, and electrolyte prepared as described below were used. The dimensions of the battery are an outer diameter of 4.8 mm and a thickness of 1.4 mm. As an example, the positive electrode active material was prepared as follows: First, the raw material, lithium-containing manganese oxide (Li4Mn5O 12 ) was created as follows.

[0046] MnO2(CMD) and LiOH·H2O were mixed at a molar ratio of 5:4 using zirconia balls in a ball mill for 20 hours. Next, this mixture was calcined at 500 °C for 24 hours in an atmosphere with an oxygen concentration of about 30 - 35%. The calcined product was pulverized to an average particle size of about 10 μm. The lithium-containing manganese oxide (Li4Mn5O 12 ) prepared in this way was used as a starting material, mixed with 20 g of commercially available lithium chloride, placed in a 30 ml crucible, and heated at 400 °C for 72 hours. After heating, the precipitate was recovered while dissolving the contents with pure water. The precipitate was dried at 60 °C.

[0047] The positive electrode mixture was prepared as follows. Graphite as a conductive agent and polyacrylic acid as a binder were mixed with the pulverized precipitate in a weight ratio of precipitate:graphite:polyacrylic acid = 90:7:3 to form a positive electrode mixture. Next, 5 mg of this positive electrode mixture was pressure-molded into a pellet with a diameter of 2.4 mm at 2 ton / cm 2 . Then, the positive electrode pellet thus obtained was adhered to and integrated into a positive electrode can using an electrode current collector made of a conductive resin adhesive containing carbon (positive electrode unitization), and then dried under reduced pressure at 250 °C for 8 hours.

[0048] The negative electrode was prepared as follows. Commercially available SiO pulverized was used as the active material of the working electrode. Graphite as a conductive agent and polyacrylic acid as a binder were mixed with this active material in weight ratios of 45:40:15, respectively, to form a negative electrode mixture. A pellet obtained by pressure-molding 2.6 mg of the mixture into a pellet with a diameter of 2.4 mm at 2 ton / cm 2 was used. After that, using the negative electrode pellet thus obtained, it was adhered to and integrated into a negative electrode can using electrode current collector 2 made of a conductive resin adhesive with carbon as a conductive filler (negative electrode unitization), and then dried under reduced pressure at 250 °C for 8 hours. Furthermore, a lithium foil 106 punched out to a diameter of 2 mm and a thickness of 0.22 mm was pressure-bonded onto the pellet to form a lithium-negative electrode pellet laminated electrode. A non-woven fabric made of glass fiber with a thickness of 0.2 mm was punched out to φ3 mm after drying to be used as a separator. A gasket made of PEEK was used.

[0049] For the electrolytes, a positive electrode electrolyte and a negative electrode electrolyte were prepared by adding lithium borofluoride (LiBF4) or lithium hexafluoride phosphate (LiPF6) to a 1:1 volume ratio mixed solvent of ethylene carbonate (EC) and γ-butyrolactone (γBL:GBL) at the concentrations shown in Table 1 below. When manufacturing a housing container consisting of a positive electrode can and a negative electrode can by crimping, the positive electrode body is placed in the positive electrode can, and then the electrolyte for the positive electrode is injected. After that, the negative electrode body is placed on the upper side of the positive electrode can via a separator, and the electrolyte for the negative electrode is injected around the negative electrode body. Then, the opening of the positive electrode can is sealed with the negative electrode can, and the peripheral edge of the opening of the positive electrode can is crimped as shown in Figure 1 to produce a non-aqueous electrolyte secondary battery.

[0050] Non-aqueous electrolyte secondary batteries were fabricated by applying the positive electrode active material, negative electrode active material, lithium salt, and solvent shown in Examples 1-8 and Comparative Examples 1-9 in Table 1, and setting the support salt concentration of the electrolyte on the positive electrode side (referred to as positive electrode concentration) and the support salt concentration of the electrolyte on the negative electrode side (referred to as negative electrode concentration) as shown in Examples 1-8 and Comparative Examples 1-9.

[0051] [Table 1]

[0052] [Table 2]

[0053] The non-aqueous electrolyte secondary batteries shown in Examples 1-8 and Comparative Examples 1-9 were subjected to a reflow process heated to 260°C. The battery height (bulging of the battery case) was measured and evaluated before and after the reflow process. If the difference between (thickness of the container after reflow) and (thickness of the container before reflow) was 0.03 mm or less, it was judged to be acceptable and received a rating of ◎. In Table 2, the circles (○) indicate a range of 0.02mm to 0.025mm, and the triangles (△) indicate a range of 0.025mm to 0.03mm. The comparative examples 1, 2, and 3 shown in the table correspond to the examples 1, 2, and 3 described in Japanese Patent Application Publication No. 2004-327282. The non-aqueous electrolyte secondary batteries shown in Examples 1-8 and Comparative Examples 1-9 were subjected to a reflow process heated to 260°C, and the resistance increase rate of the non-aqueous electrolyte secondary batteries before and after the reflow process was measured. A value of (resistance after reflow / resistance before reflow) of 95-110% was judged as ◎, 110-115% as ○, 115-120% as △, and 120% or more as ×.

[0054] The non-aqueous electrolyte secondary batteries shown in Examples 1-8 and Comparative Examples 1-9 were subjected to a reflow process heated to 260°C, and the capacity change in the non-aqueous electrolyte secondary batteries before and after the reflow process was measured. If the value of (capacity of non-aqueous electrolyte secondary battery without reflow / capacity of non-aqueous electrolyte secondary battery with reflow) was 95-105%, it was judged as ◎; if it was 85-90%, it was judged as ○; if it was 80-95%, it was judged as △; and if it was 80% or less, it was judged as ×.

[0055] For the non-aqueous electrolyte secondary batteries shown in Examples 1-8 and Comparative Examples 1-9, the 1.8V cutoff voltage, which represents the end-of-cycle characteristics after reflow soldering, was determined. If the percentage was greater than 75%, it was judged as ◎; if it was between 70% and 75%, it was judged as ○; if it was between 65% and 70%, it was judged as △; and if it was 65% or less, it was judged as ×.

[0056] The over-discharge characteristics were determined for the non-aqueous electrolyte secondary batteries shown in Examples 1-8 and Comparative Examples 1-9. Over-discharge characteristics correspond to the recycling characteristics up to over-discharge (0V), and less capacity degradation is considered desirable. This can be judged to be a more stringent test than the 1.8V cutoff mentioned above. If the percentage was greater than 50%, it was judged as ◎; if it was between 45% and 50%, it was judged as ○; if it was between 40% and 45%, it was judged as △; and if it was 40% or less, it was judged as ×.

[0057] For the non-aqueous electrolyte secondary batteries shown in Examples 1-8 and Comparative Examples 1-9, the internal resistance was measured to understand the high-temperature, high-humidity storage characteristics. This is a substitute test for lifespan, and no increase in resistance is preferable. The internal resistance was judged as follows: (resistance after high-temperature, high-humidity storage after reflow / resistance before high-temperature, high-humidity storage after reflow) value of 95-120% was judged as ◎, 120-125% as ○, 125-130% as △, and 130% or more as ×.

[0058] The capacity of the non-aqueous electrolyte secondary batteries shown in Examples 1-8 and Comparative Examples 1-9 was measured. This serves as a substitute test for lifespan, and a battery with less capacity degradation is considered superior. The capacity was judged as follows: (Capacity after high temperature and humidity storage after reflow / Capacity before high temperature and humidity storage after reflow) was judged as ◎ if it was 85% or more, ○ if it was between 80% and 85%, △ if it was between 75% and 80%, and × if it was 75% or less.

[0059] As shown in Tables 1 and 2, Examples 1 to 9, in which the support salt concentration on the positive electrode side was 2-3 mol / L and the support salt concentration on the negative electrode side was 0.5-1 mol / L, showed excellent results in all measurement parameters. The non-aqueous electrolyte secondary batteries of Examples 1 to 9 did not swell before and after reflow soldering, showed little increase in resistance, little change in capacity, excellent cycle characteristics, and excellent storage characteristics. In contrast to these, Comparative Examples 1-3 and 8-9 are examples where the support salt concentration on the positive electrode side and the support salt concentration on the negative electrode side are equal, but they are inferior to the characteristics shown in Examples 1-9 in at least one of the characteristics.

[0060] Comparative Examples 4 and 6 were samples in which no supporting salt was added to the electrolyte on the negative electrode side, but they were inferior to Examples 1 to 9 in all characteristics except swelling. Comparative Examples 5 and 7 were samples in which the difference between the support salt concentration on the positive electrode side and the support salt concentration on the negative electrode side was reduced, but all characteristics except for swelling and resistance increase rate were inferior to those of Examples 1 to 9.

[0061] Furthermore, comparing Examples 1 and 2 with Comparative Examples 2 and 3, the positive electrode electrolyte concentration in Examples 1 and 2 is 2 mol / l, while that of Comparative Example 2 is also 2 mol / l, and that of Comparative Example 3 is even more concentrated at 2.5 ml / l. However, the swelling, resistance increase, and capacity after reflow are superior in Examples 1 and 2. This seems to contradict the content of Patent Document 1 (Japanese Patent Publication No. 2004-327282), which states that a higher electrolyte concentration can suppress degradation of the lithium metal oxide, which is the positive electrode active material, due to oxygen release or lithium release. This is thought to be related to the fact that the negative electrode electrolyte concentration in Examples 1 and 2 of the present invention is lower than that in Comparative Examples 2 and 3.

[0062] Although battery components are dried before assembly and assembly is carried out in a dry room with a dew point of -40°C or lower, the moisture (H2O) inside the assembled battery is not zero. Furthermore, although assembled non-aqueous electrolyte secondary batteries are exposed to the atmosphere, as shown in Figure 1, non-aqueous electrolyte secondary batteries with a "crimp-sealed" structure allow a small amount of moisture (H2O) to enter the battery from the atmosphere. In the reflow process of non-aqueous electrolyte secondary batteries, the lithium salt in the electrolyte solute is decomposed by the trace amounts of H2O contained in the battery, and this decomposition reaction is thought to occur on the negative electrode side.

[0063] In Comparative Examples 2 and 3, the salt concentration of the electrolyte at the negative electrode is low, which is thought to suppress the decomposition reaction of the lithium salt in the electrolyte solute near the negative electrode. In other words, the causes of battery degradation due to reflow are, in order of degree of influence (greatest reflow degradation): (1) decomposition of the positive electrode active material, and (2) decomposition of the solute (lithium salt) by the negative electrode active material. Therefore, although the positive electrode electrolyte concentration in Examples 1 and 2 is lower than that in Comparative Examples 2 and 3, the negative electrode electrolyte concentration is lower, so it is thought that the reflow characteristics are slightly better.

[0064] Comparing Examples 1, 2, 3, and 4, Examples 3 and 4, which have higher positive electrode electrolyte concentrations, exhibit superior reflow characteristics. Furthermore, comparing Examples 1, 2, 3, and 4 with Comparative Examples 1, 2, and 3, Examples 4 show superior post-reflow cycle characteristics and high-temperature, high-humidity storage characteristics.

[0065] Comparative Example 4, Example 1, Example 2, and Comparative Example 5 all had a positive electrode electrolyte concentration of 2 mol / l, while the negative electrode electrolyte concentrations were 0 mol / l, 0.5 mol / l, 1 mol / l, and 1.5 mol / l. Comparative Example 4 showed suppressed swelling in the reflow characteristics, but other characteristics were poor. This is thought to be due to the low concentration of solute (lithium salt) in the battery. Furthermore, while the swelling and resistance increase in reflow characteristics were suppressed in Comparative Example 5, other characteristics were poor. This is thought to be due to the excessively high concentration of solute (lithium salt) in the battery.

[0066] Comparative Example 6, Example 3, Example 4, and Comparative Example 7 all have a positive electrode electrolyte concentration of 3 mol / l and negative electrode electrolyte concentrations of 0 mol / l, 0.5 mol / l, 1 mol / l, and 1.5 mol / l, respectively. Comparative Example 6 shows suppressed swelling in reflow characteristics, but other characteristics are poor. This is likely due to a low concentration of solute (lithium salt) in the battery. Furthermore, while the swelling and resistance increase in Comparative Example 7 are suppressed, other characteristics are poor. This is likely due to an excessively high concentration of solute (lithium salt) in the battery. Based on these results, it was determined that it is preferable for the support salt concentration (positive electrode concentration) on the positive electrode side to be 2-3 mol / L, and the support salt concentration (negative electrode concentration) on the negative electrode side to be 0.5-1 mol / L.

[0067] By the way, when manufacturing the non-aqueous electrolyte secondary battery described in the previous embodiment, various manufacturing procedures described below can be employed. Step 1 Before crimping, the positive electrode body 10 is attached to the inner bottom surface of the positive electrode can via an adhesive layer such as conductive paste. After drying, the electrolyte 50A from the positive electrode housing side is supplied (dropped) onto the positive electrode body 10. With the gasket assembled before crimping, the negative electrode can is oriented upside down compared to Figure 1. The negative electrode body 20 is attached to the inner bottom surface of the negative electrode can via an adhesive layer such as conductive paste. After drying, the separator 30 is placed on the negative electrode body 20, and the electrolyte 50B from the negative electrode housing side is supplied (dropped). Subsequently, the openings of the positive electrode can and the negative electrode can are fitted together and crimped to obtain a non-aqueous electrolyte secondary battery 1 in which the positive electrode can 12 and negative electrode can 22 shown in Figure 1 are joined together.

[0068] Step 2 Before crimping, the positive electrode body 10 is attached to the inner bottom surface of the positive electrode can via an adhesive layer such as conductive paste. After drying, the electrolyte 50A from the positive electrode housing side is supplied (dropped) onto the positive electrode body 10. With the gasket assembled before crimping, the negative electrode can is oriented upside down compared to Figure 1. The negative electrode body 20 is attached to the inner bottom surface of the negative electrode can via an adhesive layer such as conductive paste. After drying, the electrolyte 50B from the negative electrode housing side is supplied (dropped) onto the negative electrode body 20, and then the separator 30 is placed on top of the negative electrode body 20. After that, the openings of the positive electrode can and the negative electrode can are fitted together and crimped to obtain a non-aqueous electrolyte secondary battery 1 in which the positive electrode can 12 and negative electrode can 22 shown in Figure 1 are joined together.

[0069] Step 3 Before crimping, the positive electrode body 10 is attached to the inner bottom surface of the positive electrode can via an adhesive layer such as conductive paste. After drying, the electrolyte 50A from the positive electrode housing side is supplied (dropped), and the separator 30 is placed on top of the positive electrode body 10. With the gasket assembled before crimping, the negative electrode can before crimping is oriented upside down compared to Figure 1. The negative electrode body 20 is attached to the inner bottom surface of the negative electrode can via an adhesive layer such as conductive paste. After drying, the electrolyte 50B from the negative electrode housing side is supplied (dropped) onto the negative electrode body 20. Then, the openings of the positive electrode can and the negative electrode can are fitted together and crimped to obtain a non-aqueous electrolyte secondary battery 1 in which the positive electrode can 12 and negative electrode can 22 shown in Figure 1 are joined together.

[0070] The steps 1 to 3 described above can be explained as a method for manufacturing a non-aqueous electrolyte secondary battery 1 as shown in Figure 1, by filling the positive electrode body 10 or a positive electrode can containing the positive electrode body 10 and a separator 30 with the electrolyte 50A on the positive electrode side, filling the negative electrode body 20 and a separator 30 or a negative electrode body 20 with the electrolyte 50B on the negative electrode side, which is equipped with a gasket before crimping, and then joining the negative electrode can to the positive electrode can by crimping.

[0071] Step 4 With the gasket assembled before crimping, the negative electrode can is oriented upside down compared to Figure 1. The negative electrode body 20 is attached to the inner bottom surface of the negative electrode can via an adhesive layer such as conductive paste. After drying, the separator 30 is placed on the negative electrode body 20, and the electrolyte 50B on the negative electrode housing side is supplied (dropped) to the separator 30. The electrolyte 50B is also impregnated into the negative electrode body 20 via the separator 30. The positive electrode body 10 is placed on the separator 30, and the electrolyte 50A on the positive electrode housing side is supplied (dropped). An adhesive layer such as conductive paste is applied to the inner bottom surface of the positive electrode can before crimping, which is oriented upside down compared to Figure 1. After drying, this positive electrode can before crimping is fitted into the aforementioned negative electrode can and crimped. By doing so, a non-aqueous electrolyte secondary battery 1 with the configuration shown in Figure 1 can be manufactured.

[0072] Step 5 With the gasket assembled before crimping, the negative electrode can is placed upside down compared to Figure 1, and the negative electrode body 20 is attached to the inner bottom surface of the negative electrode can via an adhesive layer such as conductive paste, and then dried. After drying, the electrolyte 50B on the negative electrode housing side is dripped (supplied) onto the negative electrode body 20. After this, the separator 30 is placed on the negative electrode body 20. Next, the positive electrode body 10 is placed on the separator 30, and the electrolyte 50A on the positive electrode housing side is dripped (supplied). An adhesive layer such as conductive paste is applied to the inner bottom surface of the positive electrode can before crimping, which is placed upside down compared to Figure 1, and after drying, this positive electrode can before crimping is fitted into the aforementioned negative electrode can and crimped. By doing so, a non-aqueous electrolyte secondary battery 1 with the configuration shown in Figure 1 can be manufactured.

[0073] Steps 4 and 5 described above can be explained as a method of joining the positive electrode can to the negative electrode can by crimping, with the gasket before crimping, supplying the electrolyte 50B from the negative electrode can side to the negative electrode body 20 or the negative electrode body 20 and separator 30 housed in the negative electrode can, placing the separator 30 and then placing the positive electrode body 10 on top of it if the negative electrode body 20 and separator 30 are housed in the negative electrode can, placing the positive electrode body 10 on top of the separator 30, supplying the electrolyte 50A from the positive electrode side to the positive electrode body 10, and then joining the positive electrode can to the negative electrode can by crimping.

[0074] Step 6 The positive electrode body 10 is attached to the inner bottom surface of the positive electrode can, which has a gasket assembled before crimping, via an adhesive layer such as conductive paste. After drying, the electrolyte 50A on the positive electrode housing side is supplied (dropped), and the separator 30 is placed on the positive electrode body 10. The negative electrode body 20 is placed on the separator 30, and the electrolyte 50B on the negative electrode can side is dripped (supplied). The negative electrode can 22, which has an adhesive layer such as conductive paste applied to its inner bottom surface and has been dried, is placed over the positive electrode can, and the positive electrode can and negative electrode can are joined by crimping. This crimping process allows for the manufacture of a non-aqueous electrolyte secondary battery 1 with the configuration shown in Figure 1.

[0075] Step 7 Before crimping, the positive electrode body 10 is attached to the inner bottom surface of the positive electrode can, which has a gasket assembled before crimping, via an adhesive layer such as conductive paste. After drying, the separator 30 is placed on the positive electrode body 10, and the electrolyte 50A from the positive electrode housing side is dripped (supplied) from above the separator 30. The electrolyte 50A is also impregnated into the positive electrode body 10 via the separator 30. The negative electrode body 20 is placed on the separator 30, and the electrolyte 50B from the negative electrode can side is dripped (supplied) onto the negative electrode body 20. The negative electrode can 22, which has an adhesive layer such as conductive paste applied to its inner bottom surface and has been dried, is placed over the positive electrode can, and the positive electrode can and negative electrode can are joined by crimping. This crimping process allows for the manufacture of a non-aqueous electrolyte secondary battery 1 with the configuration shown in Figure 1.

[0076] Steps 6 and 7 described above can be explained as a method of joining the negative electrode can to the positive electrode can, which is equipped with a gasket before crimping and contains either the positive electrode body 10 or the positive electrode body 10 and separator 30 before crimping; containing the electrolyte 50A on the positive electrode can side; if the positive electrode body 10 is contained in the positive electrode can, placing the separator 30 and then placing the negative electrode body 20 on top of it; if the positive electrode body 10 and separator 30 are contained in the positive electrode can, placing the negative electrode body 20 on the separator 30; dripping (supplying) the electrolyte 50B on the negative electrode side to the negative electrode body 20 directly or via the separator 30; and finally joining the negative electrode can to the positive electrode can.

[0077] Step 8 An adhesive layer such as conductive paste is applied to the center of the inner bottom surface of the pre-crimping positive electrode can, which is equipped with a gasket before crimping, and allowed to dry. Then, electrolyte 50A from the positive electrode can is dropped onto the center of the positive electrode can, and the positive electrode body 10 is placed on top. Next, the separator 30 and the negative electrode body 20 are placed on top of the positive electrode body 10, and electrolyte 50B from the negative electrode body is dropped (supplied) onto the negative electrode body 20. After this, the pre-crimping negative electrode can, which has had an adhesive layer such as conductive paste applied to the center of its inner bottom surface and allowed to dry, is placed over the aforementioned positive electrode can, and the positive electrode can and negative electrode can are joined by crimping. This crimping process allows for the manufacture of a non-aqueous electrolyte secondary battery 1 with the configuration shown in Figure 1.

[0078] The procedure described above, step 8, can be explained as a method of joining the positive electrode can to the positive electrode can before crimping, which is equipped with a gasket before crimping, by filling the positive electrode can side with the electrolyte, the positive electrode body 10, the separator 30, and the negative electrode body 20 into the positive electrode can before crimping, supplying the electrolyte to the negative electrode body 20, and then crimping the negative electrode can to the positive electrode can. As explained above, various procedures can be used to manufacture the non-aqueous electrolyte secondary battery 1. Any procedure that can achieve the configuration shown in Figure 1, other than the procedure described here, may be used. [Explanation of Symbols]

[0079] 1...Non-aqueous electrolyte secondary battery, 2...Housing container, 10...Positive electrode, 12...Positive electrode can, 12a...Opening, 12b...Peripheral part, 14...Positive electrode current collector, 20...Negative electrode, 22...Negative electrode can, 22a...Outer peripheral end, 24...Negative electrode current collector, 30...Separator, 40...Gasket, 41...Annular groove, 50A...Electrolyte, 50B...Electrolyte.

Claims

1. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, an electrolyte containing a support salt and a solvent, and a separator, housed in a container formed by a positive electrode container and a negative electrode container, The positive electrode is housed on one side of the housing container via the separator, and the negative electrode is housed on the other side of the housing container, A non-aqueous electrolyte secondary battery characterized in that the support salt concentration of the electrolyte on the positive electrode side of the containment container and the support salt concentration of the electrolyte on the negative electrode side of the containment container are different, the support salt concentration on the positive electrode side is higher than the support salt concentration on the negative electrode side, the support salt concentration on the positive electrode side is 2 to 3 mol / L, and the support salt concentration on the negative electrode side is 0.5 to 1 mol / L, and the separator is a separator that allows mutual diffusion between the components of the electrolyte on the positive electrode side and the components of the electrolyte on the negative electrode side.

2. The non-aqueous electrolyte secondary battery according to Claim 1, wherein the separator is an ion-permeable separator with a thickness of 5 to 300 μm, and the separator has the function of adjusting the support salt concentration of the electrolyte on the positive electrode housing side to a range of 0.7 to 1.5 mol / L and the support salt concentration of the electrolyte on the negative electrode housing side to a range of 0.7 to 1.5 mol / L after the positive electrode housing and the negative electrode housing are joined together.

3. The positive electrode container is cylindrical with a bottom, The negative electrode can is fixed to the inside of the opening of the positive electrode can with a gasket in between. The non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the housing container is sealed by providing a crimped portion on the negative electrode side of the opening of the positive electrode can.

4. A method for manufacturing a non-aqueous electrolyte secondary battery, wherein a positive electrode, a negative electrode, an electrolyte containing a support salt and a solvent, and a separator are housed in a housing container formed by joining a positive electrode container and a negative electrode container, wherein when housing the positive electrode, the negative electrode, the electrolyte, and the separator in the housing container, A method for manufacturing a non-aqueous electrolyte secondary battery, characterized in that the support salt concentration of the electrolyte on the positive electrode housing side is higher than the support salt concentration of the electrolyte on the negative electrode housing side, the support salt concentration on the positive electrode housing side being 2 to 3 mol / L, and the support salt concentration on the negative electrode housing side being 0.5 to 1 mol / L, and the separator used is one that allows the components of the electrolyte on the positive electrode housing side and the components of the electrolyte on the negative electrode housing side to mutually diffuse through the separator.

5. The method for manufacturing a non-aqueous electrolyte secondary battery according to Claim 4, characterized in that the separator is an ion-permeable separator with a thickness of 5 to 300 μm, wherein the separator has the function of adjusting the support salt concentration of the electrolyte on the positive electrode housing side to a range of 0.7 to 1.5 mol / L and the support salt concentration of the electrolyte on the negative electrode housing side to a range of 0.7 to 1.5 mol / L after the positive electrode housing and the negative electrode housing are joined together.

6. The positive electrode container is cylindrical with a bottom, The negative electrode can is fixed to the inside of the opening of the positive electrode can with a gasket in between. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 4 or 5, characterized in that the housing container is sealed by providing a crimped portion on the negative electrode side of the opening of the positive electrode can.

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