JP2012190729A - Coin-type nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical cell excellent in electric characteristics such as charge efficiency and discharge capacity, and resistant to reflow heating.SOLUTION: A coin-type nonaqueous electrolyte secondary battery in accordance with an embodiment of the present invention comprises a positive electrode 201, a negative electrode 206, electrolytic solution 209 composed of a supporting electrolyte and a nonaqueous solvent, a gasket 208, and a separator 207. The Klemm water absorbency of the separator 207 is greater than or equal to 20 mm.

Description

  The present invention relates to a coin-type non-aqueous electrolyte secondary battery that can be reflow soldered.

  Coin-type non-aqueous electrolyte secondary batteries are conventionally used as backup power sources for clock functions, backup power sources for semiconductor memories, standby power sources for electronic devices such as microcomputers and IC memories, solar watch batteries, and power sources for driving motors. In recent years, it has been studied as a power storage unit for electric vehicles and an auxiliary power storage unit for energy conversion / storage systems.

  In recent years, the necessity for large capacity and current has been reduced due to the non-volatile semiconductor memory and the low power consumption of the timepiece functional element. Rather, there is an increasing demand for thin and reflow solderable products.

  As the separator of the coin-type non-aqueous electrolyte secondary battery, a polyolefin microporous film typified by polyethylene, polypropylene or the like is generally used. However, the heat softening temperature of polypropylene is 100 ° C. to 120 ° C., and when exposed to a temperature significantly higher than the heat softening temperature when passing through the reflow furnace, the separator is damaged by heat.

  Therefore, reflow solderable coin-type non-aqueous electrolyte secondary batteries have heat resistance (heat melting, heat shrinkage, etc.), permeability (ion permeability, air permeability, etc.), mechanical characteristics (tensile strength, etc.) It has been reported that polyphenylene sulfide (PPS) and glass fiber having the above are used. (For example, see Patent Document 1 and Patent Document 2)

JP 2004-087229 A JP 2002-063942 A

  In the reflow soldering process, the coin-type non-aqueous electrolyte secondary battery is exposed to a high temperature of 200 to 260 ° C. In particular, in recent years, lead-free solder has been adopted due to environmental problems, and the melting point of solder has risen, so that a reflow furnace at 260 ° C. is generally used.

  In the reflow coin-type non-aqueous electrolyte secondary battery, a material having a heat resistance of 260 ° C. is used for all parts, but it is practically difficult to completely suppress deterioration of characteristics due to heat. In the reflow coin-type non-aqueous electrolyte secondary battery, the chemical reaction during reflow heating between the electrolytic solution and the active material or the conductive agent cannot be completely suppressed, so that gas is generated in the battery. Moreover, in the negative electrode of a lithium battery, a lithium ion battery, or a lithium ion capacitor, a reaction occurs between the active material and the electrolytic solution, and an SEI (Solid Electrolyte Interface) film is generated in the active material, and this SEI film contributes to the stability of the battery. is doing. However, since the same reaction is further promoted by reflow heating, gas is generated and stays in the battery.

  On the other hand, a separator that prevents a short circuit between the positive electrode and the negative electrode is generally present between the positive electrode and the negative electrode. When the residence place of the gas which generate | occur | produced in the battery by reflow heating exists between a positive electrode and a negative electrode, it will be in the dry state by it. As a result, the internal resistance value, which is an electrical characteristic of the coin-type non-aqueous electrolyte secondary battery, is increased, and there is a problem that the charging efficiency is lowered and the discharge capacity is reduced.

The present invention for solving the above problems employs the following configuration.
The invention according to claim 1 is a coin-type non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, an electrolytic solution comprising a supporting salt and a non-aqueous solvent, a gasket and a separator, wherein The gist of the invention is a coin-type non-aqueous electrolyte secondary battery having a water absorption of 20 mm or more.
According to the coin-type non-aqueous electrolyte secondary battery according to claim 1, by using a separator having a Krem water absorption of 20 mm or more, a sufficient electrolytic solution can be retained in the positive electrode and the negative electrode without drying the separator. Can do. Therefore, it is possible to provide a coin-type nonaqueous electrolyte secondary battery having high reflow heat resistance.

The invention according to claim 2 is characterized in that the non-aqueous solvent is at least one of lactone, glyme, cyclic carbonate, chain carbonate and chain ether. The gist is that it is a water electrolyte secondary battery.
According to the coin-type non-aqueous electrolyte secondary battery of claim 2, it is possible to suppress the generation of gas due to reflow heating and to make the viscosity capable of absorbing water by the separator. Therefore, it is possible to provide a coin-type nonaqueous electrolyte secondary battery having high reflow heat resistance.

The gist of the invention described in claim 3 is the coin-type non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the negative electrode is an alloy-based negative electrode.
According to the coin-type non-aqueous electrolyte secondary battery according to claim 3, a coin-type non-aqueous electrolyte secondary battery having high reflow heat resistance is provided by using an alloy-based negative electrode and a separator having a Krem water absorption of 20 mm or more. Is possible.

The invention according to claim 4 is characterized in that the active material of the negative electrode is at least one active material selected from SiO and Li-Al alloys. The coin-type non-aqueous electrolyte according to claim 1 or 2 The gist is that it is a secondary battery.
According to the coin-type non-aqueous electrolyte secondary battery according to claim 4, by using one or more active materials selected from SiO and Li-Al alloy as a negative electrode active material, and a separator having a Krem water absorption of 20 mm or more. Thus, it is possible to provide a coin-type non-aqueous electrolyte secondary battery having high reflow resistance.

The coin-type non-aqueous electrolyte according to any one of claims 1 to 4, wherein the separator is made of at least one selected from glass fiber, cellulose, and polyphenylene sulfide. The gist is that it is a secondary battery.
According to the coin-type non-aqueous electrolyte secondary battery according to claim 5, by using glass fiber, cellulose, polyphenylene sulfide as a separator, it is possible to provide a coin-type non-aqueous electrolyte secondary battery having high reflow resistance. ing.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the electrochemical cell with high reflow heat resistance excellent in electrical characteristics, such as a small internal resistance value, charging efficiency, and discharge capacity.

It is a schematic sectional drawing which shows the example of the coin type nonaqueous electrolyte secondary battery of this invention. It is a schematic sectional drawing which shows another example of the coin type non-aqueous electrolyte secondary battery of this invention. It is the schematic which shows the Krem method which is a water absorption test method based on JISP8141.

  The present invention will be described in detail with reference to FIGS. 1 and 2, which are schematic cross-sectional views of a coin-type non-aqueous electrolyte secondary battery according to the present invention.

  In FIG. 1, a coin-type nonaqueous electrolyte secondary battery is sandwiched between a positive electrode case 203 formed in a bottomed cylindrical shape, a negative electrode case 205 formed in a hat shape, and the positive electrode case 203 and the negative electrode case 205. Gasket 208 is provided. The negative electrode case 205 also serves as a negative electrode current collector. However, as shown in FIG. 2, a negative electrode current collector 305 may be provided separately from the negative electrode case 306. The positive electrode case 203 is caulked and sealed to the negative electrode case 205 via the gasket 208 to form a sealed storage chamber S between the positive electrode case 203 and the negative electrode case 205.

  In the storage chamber S, a positive electrode current collector 202, a positive electrode 201, a separator 207, and a negative electrode 206 are arranged in this order from the bottom surface side of the positive electrode case 203 and filled with an electrolyte solution 209.

  The positive electrode 201 has a suitable binding to a conventionally known active material such as lithium-containing manganese oxide, lithium-containing cobalt oxide, lithium-containing nickel oxide, lithium-containing titanium oxide, molybdenum trioxide, and niobium pentoxide. A mixture of an adhering agent and graphite or the like as a conductive agent can be used.

  The negative electrode 206 is made of an alloy-based negative electrode such as carbon or lithium-aluminum, or a mixture of a conventionally known active material such as silicon or silicon oxide with a suitable binder and graphite as a conductive aid. be able to. In particular, an alloy-based negative electrode is preferably used as the negative electrode. It is also preferable to use at least one active material selected from SiO and Li—Al alloys. By using these, it is possible to provide a coin-type non-aqueous electrolyte secondary battery having higher reflow heat resistance.

  The separator 207 of the present invention is characterized in that the Krem water absorption is 20 mm or more. More preferably, it is 30 mm or more. By using a separator having a Krem water absorption of 20 mm or more, a sufficient electrolyte can be held in the positive electrode and the negative electrode without drying the separator. Therefore, it is possible to provide a coin-type nonaqueous electrolyte secondary battery having high reflow heat resistance.

  Clem water absorption can be tested using the Krem method, which is a water absorption test method based on JISP8141.

  Hereinafter, the Krem method, which is a water absorption test method based on JISP8141, will be described in detail with reference to FIG.

  The separator test piece 101 has a width of 15 ± 1 mm and a length of 200 mm or more. If necessary, the separator test piece 101 is collected in the vertical and horizontal directions. When collecting, it is necessary to secure an extra length necessary for hanging. A marked line 102 is drawn with a pencil in parallel at a distance of 15 mm from the short side of each separator test piece 101, and a weight 103 for immersing in the electrolytic solution 105 is attached between the marked line 102 and the short side.

  The apparatus is adjusted horizontally, and the separator test piece 101 is suspended from the hanging tool 104. When a plurality of tests are performed once, it is necessary that the marked lines of the separator test pieces 101 are in a horizontal straight line.

  Next, the electrolyte solution 105 is quickly put to the marked line 102 and the timer is started. The height at which the electrolyte solution 105 is raised in 10 minutes ± 10 seconds is read in mm. This test is performed at 23 ° C. ± 1 ° C. This height was defined as the Krem water absorption.

  In JISP8141, water is used as a test solution, but in the present invention, an electrolytic solution used in a coin-type nonaqueous electrolyte secondary battery is used. This is because a correct evaluation can be obtained as an evaluation of the coin-type non-aqueous electrolyte secondary battery. However, some electrolyte solutions for coin-type non-aqueous electrolyte secondary batteries contain components that volatilize at a measurement temperature of 23 ° C. In this case, it is necessary to pay attention to the use of a new electrolytic solution for each test, the temperature around the test, and the air volume so that the composition of the electrolytic solution is the same in each test.

  The separator 207 is desirably tested in a state where it is used. That is, if the separator is dried or heat-treated for other purposes in the manufacture of a coin-type non-aqueous electrolyte secondary battery, a more meaningful Krem water absorption can be obtained by performing the heat treatment before this test.

  The main characteristics required for separators used in reflow solderable coin-type non-aqueous electrolyte secondary batteries are generally required mechanical characteristics (such as tensile strength) and transmission characteristics (ion permeability, In addition to thermal properties such as air permeability, thermal properties (melting, thermal shrinkage, etc.) can be mentioned. As a separator that can satisfy this characteristic, glass fiber, cellulose, polyphenylene sulfide, polyethylene terephthalate, polyamide, aramid, fluororesin, ceramics, and the like can be used.

  However, the characteristics of actual separators vary greatly depending on the physical shape such as fiber diameter and particle size and distribution, porosity, thickness and number of layers of these materials.

  The present invention is not limited to a material as long as the material has sufficient heat resistance at 260 ° C. It is characterized in that the separator can be selected based on the water absorption of the clem that will be determined by the surface properties of the material and the physical shape of the separator.

  The electrolytic solution 209 is composed of a mixed solution of a solute and a solvent, and a known electrolytic solution such as lithium perfluoromethylsulfonylimide can be used as the solute.

  The solvent of the electrolytic solution 209 is selected from those having a dielectric constant, a dipole moment, a donor number, and an acceptor number that can sufficiently dissolve lithium ions or quaternary ammonium salts and obtain a sufficient ion migration rate. It is. Furthermore, the viscosity in actual use has a great influence on the moving speed of ions. In addition, it is required to be stable without being decomposed at the working voltage, and to be chemically stable in combination with the reflow temperature and the electrode. An ester compound having a carbocarbonyl group has a high relative dielectric constant, and an ether having an ether bond tends to have a low viscosity. For this reason, the solvent is preferably composed of at least one of lactone, glyme, chain ether, sulfone compound, cyclic carbonate, and chain carbonate.

  More preferably, the lactone is γ-butyllactone, glyme, the chain ether is dimethoxyethane, methoxyethoxyethane, diethoxyethane, ethylene glycol diethyl ether, dimethyl carbonate, tetraethylene glycol dimethyl ether, the sulfone compound is sulfolane, methyl. As sulfolane, ethyl methyl sulfone, and cyclic carbonate, propylene carbonate, ethylene carbonate, butylene carbonate, and chain carbonate are preferably two or more mixed solvents selected from methyl propionate, dimethyl carbonate, and methyl ethyl carbonate.

  By using these solvents, the generation of gas due to reflow heating can be suppressed, and the viscosity can be absorbed by the separator. Therefore, it is possible to provide a coin-type nonaqueous electrolyte secondary battery having high reflow heat resistance.

  The gasket 208 is formed in an annular shape along the inner peripheral surface of the positive electrode case 203. As the gasket, a hard engineering plastic having high heat resistance such as polyether ether ketone resin (PEEK), polyphenylene sulfide resin (PPS), liquid crystal polymer (LCP), polyether nitrile resin (PEN) can be used. Further, a sealing agent may be applied to the inner surface of the annular groove of the gasket 208. As the sealant, asphalt, epoxy resin, polyamide resin, butyl rubber adhesive, or the like can be used. This sealant is used after being applied to the inside of the annular groove and then dried.

  The details of the mechanism by which the present invention solves the problem are unknown, but the following model is conceivable.

  The assembled electrolyte is present in the positive electrode, the negative electrode, the separator, and the gap in the case. In a normal electrochemical cell, the entire space in the case is not filled with solid or liquid. This is not a limitation in assembling, but it is necessary to absorb the deformation due to the external pressure and the change in the internal pressure due to the temperature change at the time of assembling and after assembling by using the gas as a damper. The position of the electrolytic solution in the case is determined by the ease of water absorption of the positive electrode, the negative electrode, and the separator, and the surface tension due to the void shape in the case.

  When reflow heating a coin-type non-aqueous electrolyte secondary battery, that is, a cell case containing a chemically active electrode and a non-aqueous electrolyte, the electrolyte is decomposed by the chemical reaction between the electrode and the non-aqueous electrolyte. Will occur. For this reason, the electrolyte solution which has determined the presence position in the assembled electrochemical cell is moved to the presence position by generation of a new gas. Comparing the ease of water absorption between the electrode and the separator, the electrode having higher density and higher activity has higher water absorption. Therefore, in the coin-type non-aqueous electrolyte secondary battery after reflow heating, it is considered that the gap between the case whose position has been determined by the surface tension and the electrolyte solution are in contact with each other.

  A separator having a high Clem water absorption rate can easily take in the electrolyte in the gap in the case, and can stably hold the electrolyte in the separator. For this reason, it is thought that the coin-type nonaqueous electrolyte secondary battery using the separator of the present invention is excellent in reflow heat resistance.

When the negative electrode is an alloy-based negative electrode, the effect of the present invention is greater than when the negative electrode is a powder pellet or an electrode sheet. This is because the negative electrode is an alloy-based negative electrode, and therefore, the negative electrode is less likely to absorb water than the separator as compared with the case where the negative electrode is a powder pellet or an electrode sheet. Therefore, it is considered that the electrolyte is likely to be present in the separator, and the effect of the present invention is more manifested.
Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
A coin-type non-aqueous electrolyte secondary battery having the structure shown in FIG. The produced coin-type non-aqueous electrolyte secondary battery has an outer shape of 4.8 mm and a thickness of 1.4 mm.

  First, a positive electrode case 203 made of stainless steel and a negative electrode case 205 made of stainless steel and hard aluminum were obtained. The negative electrode case 205 has a two-layer structure of a stainless steel layer 2051 and a hard aluminum layer 2052. More specifically, the negative electrode case 205 is formed by bonding stainless steel and hard aluminum by rolling, and is formed so that the stainless steel layer 2051 is on the outside and the hard aluminum layer 2052 is on the inside. A lithium foil punched out as a negative electrode 206 to a diameter of 2 mm and a thickness of 0.22 mm is pressure-bonded to the negative electrode case 205 thus formed on the hard aluminum layer 2052 side. In this way, a negative electrode unit was produced.

  Next, lithium-containing manganese oxide, graphite as a conductive agent, and polyacrylic acid resin as a binder have a weight ratio of lithium-containing manganese oxide: graphite: polyacrylic resin = 90: 7: 3, respectively. A positive electrode mixture was prepared by mixing at a ratio. Thereafter, 7.5 mg of the positive electrode mixture was pressurized at 2 ton / cm 2 to form a pellet having a diameter of 2.2 mm, and the positive electrode 201 was obtained.

  The positive electrode 201 is bonded to the positive electrode case 203 by using a positive electrode current collector 202 made of a conductive resin adhesive containing carbon as a conductive filler, and the positive electrode 201 and the positive electrode case 203 are integrated (unit). ). In this way, a positive electrode unit was produced. Thereafter, the positive electrode unit was heat-dried under reduced pressure at 280 ° C. for 8 hours.

  A nonwoven fabric made of glass fiber having a Krem water absorption of 38 mm was dried and then punched out to 3 mm to obtain a separator 207.

In the electrolyte solution 209, tetraethylene glycol dimethyl ether (TEG) and diethoxyethane (DEE) were mixed in a volume ratio of TEG: DEE = 60: 40, and lithium perfluoromethylsulfonylimide was 1.5 mol / l. A dissolved one was prepared.
The gasket 208 made of polyether ether ketone was used.

Next, a butyl rubber adhesive (butyl rubber 30% by weight, toluene 70% by weight) and blown asphalt were dissolved in toluene to obtain a sealant. A sealant was applied to the inner edge of the positive electrode case 203 and dried by heating in a 120 ° C. dry room. Further, the gasket 208 was fitted into the inner edge of the positive electrode case 203 to which the sealing agent was applied, and the sealing agent was applied to the inner side of the annular groove of the gasket 208 and dried by heating in a 120 ° C. dry room.

A separator 207 is disposed between the positive electrode 201 and the negative electrode 206, and 5 μl of the electrolyte 209 is injected into the storage chamber S. Then, the negative electrode case 205 is inserted into the annular groove of the gasket 208, and the positive electrode unit and the negative electrode unit are stacked. Caulked and sealed.
Thus, a coin-type non-aqueous electrolyte secondary battery of Example 1 was produced.

(Example 2)
A cellulose separator having a fiber diameter and thickness different from those of Example 1 was prepared. It was 32 mm when the water absorption of Klem was measured. A coin-type non-aqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 1.

(Example 3)
A cellulose separator having a fiber diameter and thickness different from those of Example 1 was prepared. It was 25 mm when the water absorption of Klem was measured. A coin-type non-aqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 1.

(Comparative Example 1)
A cellulose separator having a fiber diameter and thickness different from those of Example 1 was prepared. It was 19 mm when the water absorption of Klem was measured. A coin-type non-aqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 1.

(Comparative Example 2)
A cellulose separator having a fiber diameter and thickness different from those of Example 1 was prepared. It was 18 mm when the water absorption of Klem was measured. A coin-type non-aqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 1.

Example 4
A coin-type non-aqueous electrolyte secondary battery having the structure shown in FIG. The produced coin-type non-aqueous electrolyte secondary battery has an outer shape of 4.8 mm and a thickness of 1.4 mm.
First, a positive electrode case 303 made of stainless steel and a negative electrode case 306 made of stainless steel were obtained.

  Next, commercially available SiO was pulverized as an active material, and graphite as a conductive agent and polyacrylic acid as a binder were mixed at a weight ratio of 45:40:15, respectively, to obtain a negative electrode mixture. Thereafter, 2.6 mg of a negative electrode mixture was pressure-molded at 2 ton / cm 2 to form a pellet having a diameter of 2.4 mm. The pellets were then bonded and integrated (unitized) to the negative electrode case 306 using a negative electrode current collector 305 made of a conductive resin adhesive containing carbon as a conductive filler. Thereafter, it was dried by heating under reduced pressure at 250 ° C. for 8 hours. Further, a lithium foil 307 punched out to a diameter of 2 mm and a thickness of 0.22 mm was pressed onto the pellet. This lithium-negative electrode pellet laminated electrode was used as the negative electrode 304. In this way, a negative electrode unit was produced.

  Next, the lithium-containing manganese oxide, the graphite as the conductive agent, and the polyacrylic acid as the binder have a weight ratio of lithium-containing manganese oxide: graphite: polyacrylic resin = 90: 7: 3, respectively. To obtain a positive electrode mixture. Thereafter, 5 mg of the positive electrode mixture was pressurized at 2 ton / cm 2 to form a pellet having a diameter of 2.4 mm, whereby a positive electrode 301 was obtained.

  The positive electrode 301 is bonded to the positive electrode case 303 by using a positive electrode current collector 302 made of a conductive resin adhesive containing carbon as a conductive filler, and the positive electrode 302 and the positive electrode case 303 are integrated (units). ). Thereafter, drying under reduced pressure was performed under the condition of 250 ° C. for 8 hours. In this way, a positive electrode unit was produced.

  A nonwoven fabric made of cellulose having a Krem water absorption of 28 mm was dried and then punched out to 3 mm to obtain a separator 308.

The electrolyte solution 310 was prepared by dissolving 1 mol / l of lithium tetrafluoroborate in a mixed solvent of γ-butyl lactone and ethylene carbonate (EC) in a volume ratio of γ-butyl lactone: EC = 50: 50.
The gasket 309 was made of polyetheretherketone.

Next, a butyl rubber adhesive (butyl rubber 30% by weight, toluene 70% by weight) and blown asphalt were dissolved in toluene to obtain a sealant. The sealing agent was applied to the inner edge of the positive electrode case 303 and dried by heating in a 120 ° C. dry room. In addition, a gasket 309 was fitted into the inner edge of the positive electrode case 303 to which the sealing agent was applied, and the sealing agent was applied to the inner side of the annular groove of the gasket 309 and dried by heating in a 120 ° C. dry room.

A separator 308 is disposed between the positive electrode 301 and the negative electrode 304, and 5 μl of the electrolyte solution 310 is injected into the storage chamber S. Then, the negative electrode case 306 is inserted into the annular groove of the gasket 309, and the positive electrode unit and the negative electrode unit are stacked. Caulked and sealed.
Thus, a coin-type nonaqueous electrolyte secondary battery of Example 4 was produced.

(Example 5)
A polyphenylene sulfide (PPS) separator having a fiber diameter and thickness different from those of Example 4 was prepared. It was 25 mm when the water absorption of Klem was measured. A coin-type nonaqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 4.

(Example 6)
A polyphenylene sulfide (PPS) separator having a fiber diameter and thickness different from those of Example 4 was prepared. It was 20 mm when the water absorption of Klem was measured. A coin-type nonaqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 4.

(Comparative Example 3)
A polyphenylene sulfide (PPS) separator having a fiber diameter and thickness different from those of Example 4 was prepared. It was 16 mm when the water absorption of Klem was measured. A coin-type nonaqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 4.

(Comparative Example 4)
A polyphenylene sulfide (PPS) separator having a fiber diameter and thickness different from those of Example 4 was prepared. It was 14 mm when the water absorption of Klem was measured. A coin-type nonaqueous electrolyte secondary battery was produced using this separator in the same manner as in Example 4.

  The 30 coin-type nonaqueous electrolyte secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 4 manufactured as described above were stored at room temperature for 10 days, and after confirming that the battery voltage was stable, reflow was performed. The previous internal resistance and capacitance values were obtained. On the other hand, 30 pieces each of Examples 1 to 6 and Comparative Examples 1 to 4 were subjected to heat treatment three times in a reflow furnace under conditions of preheating 180 ° C. for 10 minutes and maximum heating temperature 260 ° C. for 20 seconds. The coin-type non-aqueous electrolyte secondary battery after the heat treatment was cooled to room temperature, and then the internal resistance value and the capacity value after reflow were obtained. When the resistance value and the capacitance value before reflowing were set to 100%, the resistance value and the capacitance value after reflowing were obtained, and the resistance change rate before and after reflowing and the capacity retention rate before and after reflowing were obtained, respectively. The larger the resistance change rate before and after reflow, the higher the internal resistance after reflow, and the smaller the value of capacity retention before and after reflow, the greater the capacity degradation.

  The results shown in Table 1 are the results of Examples 1 to 3 and Comparative Examples 1 and 2 using an alloy-based negative electrode. It can be seen that the resistance change rate before and after the reflow increases and the capacity retention rate decreases as the value of the Klem water absorption decreases. The increase in the rate of change in resistance and the decrease in the capacity retention rate indicate deterioration of the characteristics of the nonaqueous electrolyte secondary battery due to reflow. As can be seen from Table 1, in Examples 1 to 3 of the present invention where the Krem water absorption is greater than 20 mm, the increase in resistance is suppressed and at the same time the deterioration of the capacity is suppressed. In this case, the resistance doubles and the capacity deterioration reaches 70%.

  The results shown in Table 2 are the results of a coin-type nonaqueous electrolyte secondary battery in which the negative electrode, the electrolytic solution, and the separator are different from those in Table 1. Also in this result, it can be understood that the resistance change rate before and after the reflow increases and the capacity retention rate decreases as the value of the Klemm water absorption decreases. As can be seen from Table 2, Examples 4 to 6 of the present invention having a Klem water absorption of 20 mm or more, which suppresses an increase in resistance and at the same time, suppresses deterioration of the capacity, In No. 4, the internal resistance after reflow increases, resulting in large capacity degradation.

  As can be seen from Tables 1 and 2, when a separator having a Krem water absorption of 20 mm or more was used, the same good results were obtained regardless of the positive electrode, the negative electrode, the electrolytic solution, and the separator. In other words, it is not limited to the types of negative electrode, electrolytic solution, and separator. On the other hand, Examples 3 and 5 and Comparative Examples 1 and 6 show the same Krem water absorption, but the increase in internal resistance before and after the capacity and the deterioration of the capacity are larger in Example 3 and Comparative Example 1. I understand. This shows that the effect of the present invention is greater when the alloy-based negative electrode is used in a coin-type non-aqueous electrolyte secondary battery than the negative electrode formed by compressing powder.

  Further, in the examples, only the effect of the separator in the coin-type non-aqueous electrolyte secondary battery is shown, but the present invention is not limited to this. For example, the present invention can be applied to a chip-type nonaqueous electrolyte secondary battery that is sealed by welding.

101 Separator test piece 102 Mark 103 Weight 104 Suspension tool 105 Electrolytic solution 201, 301 Positive electrode 202, 302 Positive electrode current collector 203, 303 Positive electrode case 205, 306 Negative electrode case 2051 Stainless steel layer 2052 Hard aluminum layer 206, 304 Negative electrode 207, 308 Separator 208, 309 Gasket 209, 310 Electrolyte 305 Negative electrode current collector S Storage chamber

Claims (5)

A coin-type non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, an electrolyte composed of a supporting salt and a non-aqueous solvent, a gasket and a separator,
A coin-type non-aqueous electrolyte secondary battery, wherein the separator has a Krem water absorption of 20 mm or more.   2. The coin-type non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous solvent is at least one of lactone, glyme, cyclic carbonate, chain carbonate, and chain ether.   The coin-type non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the negative electrode is an alloy-based negative electrode.   3. The coin-type non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material is at least one active material selected from SiO and Li—Al alloys.   5. The coin-type non-aqueous electrolyte secondary battery according to claim 1, wherein the separator is made of at least one selected from glass fiber, cellulose, and polyphenylene sulfide.

Images