JP2007257942A - Nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve cycle efficiency of a nonaqueous electrolyte secondary battery. <P>SOLUTION: The nonaqueous electrolyte secondary battery housing a cathode, an anode, and nonaqueous electrolyte in an outer package is provided with an additional liquid injection hole capable of injecting additional electrolyte into a battery after being assembled with its airtightness kept. The additional injection hole is provided with a through-hole fitted at a sealing plate sealing the outer package and sealing resin endowed with selective gas permeability for sealing the through-hole. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to improvement of cycle characteristics of a non-aqueous electrolyte secondary battery.

  Today, mobile information terminals such as mobile phones, notebook computers, PDAs, and the like are rapidly increasing in functionality, size, and weight. As a driving power source for these terminals, non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries having high energy density and high capacity are widely used.

  Such a lithium ion secondary battery has a problem that cycle deterioration due to a decrease in nonaqueous electrolytic mass occurs because the nonaqueous electrolyte is decomposed by charging and discharging. In addition, there is a problem that the gas generated by the decomposition of the nonaqueous electrolyte stays between the positive and negative electrodes, worsens the facing state of the positive and negative electrodes, thereby inhibiting the smooth charge / discharge reaction and further reducing the cycle characteristics. .

  As a technique concerning such a nonaqueous electrolyte secondary battery, the techniques described in Patent Documents 1 to 4 below are listed.

JP 2000-123875 A (abstract) JP 2000-353547 A (abstract) Japanese Patent Laid-Open No. 2001-210309 (Abstract) JP2003-68276 (abstract)

  Patent Document 1 proposes a technique for attaching a screw-type lid for sealing a hole and a hole that can be sealed by a screw-type lid to a sealing part of a battery can. According to this technique, it can be said that the effects of gas generation and swelling of the battery can associated with charging and discharging can be effectively eliminated.

  However, in the battery according to Patent Document 1, when the non-aqueous electrolyte mass is reduced by the charge / discharge cycle, it is necessary to open the lid and inject the non-aqueous electrolyte. If the work is not performed in an atmosphere, oxygen or water vapor enters the battery from the outside air, which causes a problem that the battery characteristics are deteriorated. In addition, in order to work in a vacuum atmosphere or an inert gas atmosphere, specialized knowledge and facilities are required, and there is a problem that not only the nonaqueous electrolyte can be easily injected, but also the cost is increased.

  In Patent Document 2, initial charging is performed in a state where a rubber stopper that seals the liquid injection port is attached, and the tip of a hollow needle communicated with a syringe after the initial charging is inserted from above the rubber stopper into a battery can. Has proposed a technique for recovering gas in a battery can into a syringe. According to this technique, the gas generated in the battery can during the initial charging can be reliably recovered without being released into the atmosphere and without scattering the nonaqueous electrolyte.

  However, since the battery according to Patent Document 2 collects the gas in the syringe and then removes the rubber stopper and then seals the liquid injection port with a safety valve, when the nonaqueous electrolytic mass is reduced by the charge / discharge cycle, The nonaqueous electrolyte cannot be injected into the battery again.

  Patent Document 3 proposes a technique that includes a liquid plug that can be opened and closed in a battery container. According to this technology, when the non-aqueous electrolyte mass is reduced, a non-aqueous electrolyte secondary battery with a small decrease in capacity can be realized even if it is used repeatedly by performing a non-aqueous electrolyte replenisher from the liquid stopper. Is done.

  However, the battery according to Patent Document 3 needs to open a liquid stopper and inject a nonaqueous electrolyte, and has the same problem as that of Patent Document 1.

  Patent Document 4 proposes a technique for welding a peripheral portion of a liquid injection hole of a battery case lid and a liquid injection stopper. According to this technique, it is said that the sealing property of the liquid injection hole used for injecting the nonaqueous electrolyte can be maintained.

  However, the battery according to Patent Document 4 cannot reinject the nonaqueous electrolyte into the battery when the nonaqueous electrolytic mass is reduced by the charge / discharge cycle.

  The present invention has been made in view of the above, and provides a non-aqueous electrolyte secondary battery capable of injecting a non-aqueous electrolyte again without adversely affecting the battery when the non-aqueous electrolytic mass is reduced by a charge / discharge cycle. The purpose is to provide.

  The present invention for solving the above-mentioned problems is a non-aqueous electrolyte secondary battery in which a positive electrode, a negative electrode, and a non-aqueous electrolyte are housed in an outer package, wherein the non-aqueous electrolyte secondary battery is in an assembled battery. Are provided with an additional liquid injection hole through which the nonaqueous electrolyte can be additionally injected while maintaining hermeticity.

  According to this configuration, it is equipped with an additional injection hole that can inject nonaqueous electrolyte while maintaining hermeticity, so the nonaqueous electrolyte can be added without adversely affecting the battery even if it is not in a vacuum atmosphere or inert gas atmosphere. Injection is possible. Therefore, the nonaqueous electrolytic mass reduced by the charge / discharge cycle can be easily recovered by the additional injection, and thereby the discharge capacity after the additional injection can be greatly increased. Therefore, the nonaqueous electrolyte secondary battery excellent in cycle characteristics can be provided.

  Here, “while maintaining hermeticity” means that water or gas does not enter the battery from outside air, and the gas generated inside the battery does not allow gas or the like to enter the battery from outside air. Even if the structure is discharged to the outside of the battery, it is included in the meaning of “maintaining hermeticity”.

  The said structure WHEREIN: The said nonaqueous electrolyte secondary battery is provided with the sealing board for sealing the opening part of the said exterior body, The said additional liquid injection hole is the through-hole provided in the said sealing board, and the said through-hole The sealing resin is configured to have selective gas permeability such that water does not easily pass through and the permeability of carbon dioxide gas is greater than the permeability of oxygen gas. it can.

  When water or oxygen gas enters the inside of the battery, it reacts with lithium and deteriorates the battery characteristics. Therefore, it is preferable that the sealing resin does not easily cause water and does not allow oxygen gas to pass therethrough. On the other hand, carbon dioxide gas is generated by decomposition of the nonaqueous electrolyte, and when these gases remain in the battery, the battery is expanded and the cycle characteristics are deteriorated. Therefore, it is preferable that the sealing resin allows carbon dioxide gas to smoothly pass through the outside of the battery and be released. Therefore, it is preferable to employ the above configuration.

  Here, a gas permeability coefficient can be used as an index of gas permeability, and the gas permeability coefficient can be obtained by the following formula 1 with reference to FIG.

(Equation 1) Permeation flux [kmol / (s · m ² )] = (Gas permeability coefficient) [kmol · m / (s · m ² · kPa)] x (permeation thrust = pressure difference) [kPa] ÷ (Film thickness) [m]

  Moreover, it is preferable from the surface of a design and preparation that such an additional liquid injection hole is set as the structure which provides a through-hole in a sealing board and seals this through-hole with sealing resin.

  Here, as gas generated in the battery, there are hydrogen gas, methane gas, ethane gas and the like in addition to carbon dioxide gas. Since these gases also cause the battery to swell and deteriorate the cycle characteristics, it is preferable that the sealing resin easily permeates these gases. More preferably, the permeability of these gases is larger than that of oxygen gas.

  On the other hand, the water vapor existing outside the battery, like oxygen gas, enters the battery and reacts with lithium to deteriorate the battery characteristics. Therefore, it is preferable that the sealing resin is difficult to transmit water vapor. More preferably, the water vapor permeability is smaller than that of carbon dioxide.

  In the above configuration, a female screw thread is engraved on the inner periphery of the through hole, and a male screw thread that is opposed to the female screw thread is engraved on the outer periphery of the through resin. An axial hollow holding screw is fitted, and the sealing resin is pressed by the holding screw so that the through hole is sealed.

  In order to seal the through hole with the sealing resin, it is preferable in terms of design to adopt the above configuration. This will be described with reference to FIG. As shown in FIG. 1C, the holding screw 11 is hollow in the center (having a hollow portion 12), and the upper end of the sealing resin 13 and the outside air are in contact with each other. Therefore, when a hollow needle such as a syringe is pierced from the hollow portion 12 into the sealing resin 13 and a non-aqueous electrolyte is additionally injected, the battery remains sealed without using an inert gas atmosphere or the like. Additional water electrolyte can be injected.

  Further, in the above configuration, the cylindrical portion 16 is continuous with the through-hole and protrudes outward from the battery upper surface of the sealing plate, and a male thread is engraved on the outer periphery of the cylindrical portion 16. A holding screw that is hollow inside and has a female screw thread that opposes the male screw thread on the inner periphery of the hollow part is fitted with the sealing resin sandwiched between the upper surface of the cylindrical part. Thus, the sealing resin is pressed by the holding screw, and the through hole is sealed.

  As another configuration for sealing the through hole with the sealing resin, it is preferable in terms of design to employ the above configuration. This will be described with reference to FIG. As shown in FIG. 5C, the holding screw 11 is hollow in the center (having a hollow portion 12), and the upper end of the sealing resin 13 and the outside air are in contact with each other. Therefore, when a hollow needle such as a syringe is pierced from the hollow portion 12 into the sealing resin 13 and a non-aqueous electrolyte is additionally injected, the battery remains sealed without using an inert gas atmosphere or the like. Additional water electrolyte can be injected.

  In the above configuration, the sealing resin is a chloroprene rubber, butadiene rubber, styrene butadiene rubber, chlorosulfonated polyethylene rubber, nitrile butadiene rubber, urethane rubber, natural rubber, or silicone rubber. be able to.

  Since the resin of the above material has the selective gas permeability described above and is a general-purpose resin, it can be manufactured at a relatively low cost. Therefore, it is preferable to use the above material as a sealing resin.

  As described above, according to the present invention, a nonaqueous electrolyte secondary battery having excellent cycle characteristics can be realized.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

(Embodiment)
FIG. 1 is a schematic view showing the structure of an additional liquid injection hole (gas vent hole) of the battery of the present invention, FIG. 1 (a) is a plan view of a sealing plate, and FIG. 1 (b) is a disassembly of the additional liquid injection hole. FIG. 1C is a cross-sectional view of an additional liquid injection hole.

  As shown in FIG. 1A, the sealing plate 1 includes an electrode terminal 2, a liquid injection hole 3, and an additional liquid injection hole (gas vent hole) 4. The periphery of the liquid injection hole 3 is fixed and sealed with a sealing plate by laser welding.

  FIG. 1B shows a disassembled perspective view of the additional liquid injection hole. In this figure, the electrode terminal and the liquid injection hole are omitted. A through hole 14 is formed in the sealing plate 1, and an internal thread is engraved on the inner periphery of the through hole. A septum (sealing resin) 13 is fitted into the through hole 14. In addition, a presser screw 11 having a hollow axial center (having a hollow portion 12) in which a male screw thread opposite to the female screw thread is carved on the outer periphery is fitted and fixed to the upper portion of the septum 13. As shown in FIG. 1 (c), a resin stopper 15 is formed in the lower portion of the through-hole 14, and the septum 13 is fixed to the stopper screw 11 and the resin stopper by tightening the stopper screw 11 with screws. The through hole 14 is sealed by the compression repulsive force.

  As shown in FIG. 1C, the septum 13 is in contact with the outside air at the hollow portion 12 of the holding screw 11. For this reason, it is preferable that the septum 13 has a function which prevents the penetration | invasion of the component which has a bad influence on the battery in external air, for example, oxygen gas and water vapor | steam. On the other hand, if the gas (for example, carbon dioxide gas, methane gas, hydrogen gas, ethane gas, etc.) generated by the side reaction accompanying the charge / discharge reaction inside the battery stays between the positive and negative electrodes, the facing state of the positive and negative electrodes is deteriorated and the cycle characteristics are deteriorated. Therefore, it is preferable to have a function of releasing these gases into the outside air.

  For this reason, it is preferable that the septum (sealing resin) 13 has a selective gas permeability having a carbon dioxide gas permeability higher than an oxygen gas permeability. Examples of the resin having such selective gas permeability include chloroprene rubber, butadiene rubber, styrene butadiene rubber, chlorosulfonated polyethylene rubber, nitrile butadiene rubber, urethane rubber, natural rubber, and silicone rubber. For these resins, hydrogen gas is a gas with small molecules and high permeability. Carbon dioxide gas, methane gas, and ethane gas have large molecular weights, but the molecules easily aggregate on the resin surface and have high permeability because they have high permeability to the resin. On the other hand, oxygen gas and water vapor are less permeable because the molecules hardly aggregate on the resin surface.

  Next, a method for additionally injecting a nonaqueous electrolyte will be described.

  The non-aqueous electrolyte reacts with the positive and negative electrodes during the charge / discharge cycle to generate gas, and the amount thereof decreases as the charge / discharge cycle proceeds. As a result, when the non-aqueous electrolytic mass is too small, the smooth charge / discharge reaction is inhibited, and the discharge capacity is significantly reduced. To prevent this, when the non-aqueous electrolysis mass is reduced, the needle of the syringe having a hollow needle is inserted into the septum 13 from the hollow portion 12 of the axial center holding screw 11 and the needle tip is inserted into the battery. In this state, additional nonaqueous electrolyte is injected. In order to use this injection method, it is preferable that the material of the septum 13 is a material that automatically closes the puncture hole when the needle is removed. Further, since the septum 13 may come into contact with the non-aqueous electrolyte, the septum 13 is preferably a material having resistance to the non-aqueous electrolyte (organic solvent). As such a material, it is preferable to use the resin exemplified above.

  In order to prevent the non-aqueous electrolyte from overflowing from the battery outer body during this additional injection, a graph showing the relationship between the number of charge / discharge cycles and the non-aqueous electrolytic mass is prepared in advance. It is preferable to determine the nonaqueous electrolytic mass to be additionally injected.

  In this embodiment, the additional liquid injection hole 4 also functions as a gas vent hole for releasing the gas generated inside the battery to the outside of the battery when no additional liquid injection is performed.

  In addition, the sealing method of the through-hole using a septum is not limited to the said method.

Example 1
[Production of positive electrode]
90 parts by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material and 10 parts by mass of graphite as a conductive agent were mixed. 95 parts by mass of this mixture and 5 parts by mass of polyvinylidene fluoride (PVDF) as a binder were dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode active material slurry.

Next, this positive electrode active material slurry was applied to both surfaces of a positive electrode core made of an aluminum foil having a thickness of 20 μm with a uniform thickness of 500 g / m ² . This electrode plate was passed through a dryer to remove the organic solvent. Then, it rolled so that the packing density might be 3.3 g / cm < ³ > using the roll press machine, and produced the positive electrode.

(Production of negative electrode)
100 parts by mass of flake graphite (d ₀₀₂ : 3.356 mm, Lc: 1000 mm, average particle size 20 μm) as a negative electrode active material, 3 parts by mass of styrene butadiene rubber (SBR) as a binder, and a thickener As a negative electrode active material slurry, 2 parts by mass of carboxymethylcellulose (CMC) was dispersed in water.

Next, the negative electrode active material slurry was applied at a uniform thickness of 200 g / m ^{2 on} both surfaces of a negative electrode core made of a copper foil having a thickness of 8 μm. The electrode plate was passed through a dryer to remove moisture. Then, it rolled by using the roll press machine so that a packing density might be 1.7 g / cm < ³ >, and produced the negative electrode.

(Production of electrode body)
The positive electrode, the negative electrode, and a microporous membrane separator made of an olefin resin were wound by a winder, and an insulating anti-winding tape was attached and pressed to complete a flat electrode body.

[Nonaqueous electrolyte adjustment]
LiPF ₆ as an electrolyte salt is dissolved at a rate of 1.0 M (mol / liter) in a non-aqueous solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 50:50 (1 atm, at 25 ° C.). Thus, a non-aqueous electrolyte was obtained.

(Preparation of sealing plate)
As shown in FIG. 1, a through hole 14 having a female screw thread and having a diameter of 2.5 mm is formed at a position opposite to the liquid injection hole 3 of the electrode terminal 2 of the sealing plate 1. A female screw thread is carved in the upper part, and a resin stopper 15 is formed in the lower part of the inner periphery. A sealing resin 13 processed to a diameter of 2.5 mm and a membrane pressure of 2.0 mm using a silicone rubber septum (Shimadzu gas chromatograph inlet septum, model number: 3007-16101) was fitted into the through-hole 14. Thereafter, a holding screw 11 having a hollow axial center (having a hollow portion 12 having a diameter of 1.75 mm) and having a male screw thread that is opposed to the female screw thread is fitted into the through hole 14 in the outer peripheral portion, By stopping, the septum 13 was pressed, the through hole 14 was sealed, and a sealing plate 1 having an additional liquid injection hole 4 that also functions as a gas vent hole was produced.

[Production of battery]
The flat electrode body was inserted into a rectangular outer can, the sealing plate was fitted into the opening of the outer can, and 2.15 g of the nonaqueous electrolyte was injected from the injection hole of the sealing plate. Thereafter, the electrode body was allowed to stand for 30 minutes under reduced pressure to fully impregnate the electrode body with a nonaqueous electrolyte. Thereafter, the fitting portion and the liquid injection hole were laser welded to produce a lithium ion secondary battery according to Example 1 having a height of 50 mm, a width of 34 mm, and a thickness of 4.6 mm.

(Comparative example)
The nonaqueous electrolyte according to Comparative Example 1 is the same as the above example except that the septum is not attached and the through hole of the sealing plate is sealed by tightening with a holding screw having no hollow part (not hollow in the center). A secondary battery was produced.

<Measurement of cycle characteristics>
One battery according to the above example and two batteries according to the comparative example were subjected to charge / discharge cycles under the following conditions, and the discharge capacity for each cycle was measured. The results are shown as a graph in FIG.

  In the battery according to Example 1, when the discharge capacity reached 79% of the initial discharge capacity (704 cycles), the needle of the syringe having the hollow needle from the hollow portion 12 was pierced into the septum 13, and the needle tip Was inserted into the battery, 0.678 g of nonaqueous electrolyte was additionally injected, and then the charge / discharge cycle was repeated again.

  For one of the batteries according to the comparative example, the charge / discharge cycle was repeated without performing additional injection. Since the discharge capacity reached 55% (470 mA) of the initial discharge capacity when 750 cycles were performed, the charge / discharge cycle was stopped at this time. This was designated as Comparative Example 1.

  Regarding another battery according to the comparative example, when the discharge capacity reached 78% of the initial discharge capacity (600 cycles), the non-aqueous electrolyte was removed by removing the holding screw in an inert gas (argon gas) atmosphere. 678 g was added, and the holding screw was tightened again under an inert gas atmosphere. Thereafter, the charge / discharge cycle was repeated again. This was designated as Comparative Example 2.

Charging conditions: Up to 4.2 V at a constant current of 1 It (850 mA), and then up to 10 mA at a constant voltage. Discharging conditions: Up to 2.75 V at a constant current of 1 It (850 mA) From FIG. 3, in Example 1, the initial capacity after 590 cycles It can be seen that, while maintaining about 90%, the comparative examples 1 and 2 are greatly degraded to about 75 to 77%.

  This is considered as follows. In Example 1, silicone rubber having selective gas permeability is used, and gas generated inside the battery permeates the rubber and is released to the outside of the battery. Therefore, gas does not collect between the electrodes. On the other hand, in Comparative Examples 1 and 2, the gas generated inside the battery accumulates between the electrodes, and the positive electrode and the negative electrode are bent to make the opposing state of both electrodes worse. Therefore, the progress of the smooth charge / discharge reaction is inhibited, and the cycle characteristics are deteriorated. In addition, reaction by-products accompanying the gas generation are deposited on the bent portion, the progress of the smooth charge / discharge reaction is further inhibited, and the cycle characteristics are further deteriorated.

  In Example 1, when the additional injection was performed, the initial volume was recovered to 89%, whereas in Comparative Example 2, the additional volume was recovered only to 87% of the initial volume. I understand that. Moreover, in Example 1, it turns out that the discharge capacity after 1000 cycles is 757 mAh of 86% of initial stage, and 743 mAh of the comparative example 2.

  This is considered to be due to the same reason as the above consideration.

  Next, the relationship between the ratio of the oxygen gas permeability and the carbon dioxide permeability of the resin used for the septum and the cycle characteristics was examined.

(Example 2)
Example 1 except that a septum made of ethylene propylene rubber (EPDM) having a carbon dioxide gas permeability / oxygen gas permeability value of 0.77 was used instead of the silicone rubber (SR) septum. In the same manner, a lithium ion secondary battery according to Example 2 was produced.

(Example 3)
In place of the septum made of silicone rubber, a septum made of chloroprene rubber (CR) having a carbon dioxide gas permeability / oxygen gas permeability value of 1.11. A lithium ion secondary battery according to Example 3 was produced.

Example 4
Instead of a silicone rubber septum, a butadiene rubber (BR) septum having a carbon dioxide gas permeability / oxygen gas permeability value of 1.28 was used. A lithium ion secondary battery according to Example 4 was produced.

(Example 5)
The same as Example 1 except that a septum made of styrene butadiene butadiene rubber (SBR) having a carbon dioxide gas permeability / oxygen gas permeability value of 1.29 was used in place of the silicone rubber septum. Thus, a lithium ion secondary battery according to Example 5 was produced.

(Example 6)
Example 1 except that a septum made of chlorosulfonated polyethylene rubber (CSM) having a carbon dioxide gas permeability / oxygen gas permeability value of 1.33 was used instead of the silicone rubber septum. Similarly, a lithium ion secondary battery according to Example 6 was produced.

(Example 7)
A nitrile butadiene rubber (NBR) septum having a carbon dioxide gas permeability / oxygen gas permeability value of 1.37 was used in place of the silicone rubber septum. Thus, a lithium ion secondary battery according to Example 7 was produced.

(Example 8)
In place of the septum made of silicone rubber, a septum made of urethane rubber (U) having a carbon dioxide gas permeability / oxygen gas permeability value of 2.00 was used in the same manner as in Example 1 above. A lithium ion secondary battery according to Example 8 was produced.

Example 9
Instead of the silicone rubber septum, a natural rubber (NR) septum having a carbon dioxide gas permeability / oxygen gas permeability value of 5.57 was used. A lithium ion secondary battery according to Example 9 was produced.

  About the battery concerning Examples 1-9 produced above and the comparative example 1, the charging / discharging cycle was performed 700 times on the said conditions. The results are shown in Table 1 below and FIG.

Cycle characteristics (%) = 700th cycle discharge capacity / first cycle discharge capacity × 100
The gas permeability coefficient was determined according to JIS standard K7126-1987.

  From Table 1 and FIG. 4, the cycle characteristics of Examples 1 to 9 having gas vent holes are 70.3 to 81.1%, which is superior to 62.9% of Comparative Example 1 having no gas vent holes. You can see that

  This is considered as follows. In Examples 1 to 9, the sealing plate is provided with a through hole, and the through hole is sealed with a sealing resin. The gas generated by the charge / discharge cycle is a gas vent. Permeated and discharged outside the battery. Therefore, gas does not collect between the electrodes. On the other hand, in Comparative Example 1, the gas generated inside the battery accumulates between the electrodes, and the positive electrode and the negative electrode are bent to make the opposing state of both electrodes worse. Therefore, the progress of the smooth charge / discharge reaction is inhibited, and the cycle characteristics are deteriorated. In addition, reaction by-products accompanying the gas generation are deposited on the bent portion, the progress of the smooth charge / discharge reaction is further inhibited, and the cycle characteristics are further deteriorated.

  The septum material has a carbon dioxide permeability / oxygen gas permeability of 1.0 or less (the oxygen gas permeability is less than the carbon dioxide permeability). Carbon dioxide gas permeability / oxygen gas permeability of material is larger than 1.0 (carbon dioxide permeability is larger than oxygen gas permeability) Inferior to 77.3-81.1% of Examples 1 and 3-9 You can see that

  This is considered as follows. In Example 2, since the oxygen gas permeability of the septum is equal to or higher than the carbon dioxide permeability, a part of the carbon dioxide gas generated in the battery is accumulated between the electrodes, and the positive electrode and the negative electrode are bent to form both electrodes. This makes the facing state slightly worse than the other embodiments. Therefore, the progress of the smooth charge / discharge reaction is hindered, so that the cycle characteristics are slightly deteriorated. In Examples 1 and 3 to 9, in which the carbon dioxide permeability is higher than the oxygen gas permeability, the carbon dioxide gas and the like are smoothly released to the outside of the battery through the septum. Therefore, it is preferable that the material of the septum (sealing resin) has selective gas permeability having a carbon dioxide gas permeability higher than the oxygen gas permeability.

  In addition, although the square battery was used in the said Example, it can apply also to the large sized battery used for the cylindrical battery and the vehicle for a battery drive or a battery drive. Moreover, you may form an additional liquid injection hole (gas vent hole) in parts other than a sealing board.

  Further, the positive electrode active material, the negative electrode active material, the binder, the thickener, the non-aqueous solvent, and the electrolyte salt are not limited to the above examples, and known materials can be used.

  As described above, according to the present invention, the cycle characteristics of the non-aqueous electrolyte secondary battery can be drastically improved.

FIG. 1 is a schematic view showing the structure of an additional liquid injection hole (gas vent hole) of the battery of the present invention, FIG. 1 (a) is a plan view of a sealing plate, and FIG. 1 (b) is a disassembly of the additional liquid injection hole. FIG. 1C is a cross-sectional view of an additional liquid injection hole. FIG. 2 is a schematic diagram for explaining an equation for obtaining the gas permeability coefficient of the resin. FIG. 3 is a graph showing the discharge capacity for each cycle of Example 1 and Comparative Examples 1 and 2. FIG. 4 is a graph showing the relationship between the carbon dioxide gas permeability / oxygen gas permeability of the sealing resin and the cycle characteristics. FIG. 5 is a schematic view showing a modified example of the structure of the additional liquid injection hole (gas vent hole) of the battery of the present invention, FIG. 5 (a) is a plan view of the sealing plate, and FIG. 5 (b) is the additional liquid injection. It is a disassembled perspective view of a hole, and FIG.5 (c) is sectional drawing of an additional liquid injection hole.

Explanation of symbols

1 Sealing plate 2 Electrode terminal 3 Injection hole 4 Additional injection hole (gas vent hole)
11 Holding screw 12 Hollow part 13 Septum (resin for sealing)
14 Through hole 15 Resin stopper 16 Cylindrical part

Claims (5)

In the non-aqueous electrolyte secondary battery in which the positive electrode, the negative electrode, and the non-aqueous electrolyte are accommodated in the exterior body,
The non-aqueous electrolyte secondary battery includes an additional injection hole that can additionally inject the non-aqueous electrolyte while maintaining hermeticity in the assembled battery.
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 1,
The non-aqueous electrolyte secondary battery includes a sealing plate for sealing the opening of the exterior body,
The additional liquid injection hole has a through hole provided in the sealing plate and a sealing resin for sealing the through hole,
The sealing resin does not pass water and has a selective gas permeability in which the permeability of carbon dioxide gas is larger than the permeability of oxygen gas.
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 2,
An internal thread is engraved on the inner periphery of the through hole,
The through hole is fitted with the sealing resin and a hollow holding screw having a male screw thread opposite to the female screw thread on the outer periphery, and the sealing resin is pressed by the pressing screw. The through hole is sealed,
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 2,
Continuing with the through hole, and having a cylindrical portion protruding outward from the top surface of the sealing plate,
A male thread is engraved on the outer periphery of the cylindrical portion,
A holding screw having a hollow axial center and a female screw thread that opposes the male screw thread on the inner periphery of the hollow portion sandwiches the sealing resin between the upper surface of the cylindrical part. Fitted, and the sealing resin is pressed by the holding screw to seal the through hole,
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 2, 3 or 4,
The sealing resin is made of one or more resins selected from chloroprene rubber, butadiene rubber, styrene butadiene rubber, chlorosulfonated polyethylene rubber, nitrile butadiene rubber, urethane rubber, natural rubber, and silicone rubber.
A non-aqueous electrolyte secondary battery.

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