JP2015084343A - Nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery arranged so that little influence is exerted on a discharge characteristic even in the case of forming a flame-retardant layer on a surface of an electrode or the like.SOLUTION: A nonaqueous electrolyte battery 1 comprises: a positive electrode plate 3; a negative electrode plate 5; a separator 7; and a porous layer having an ion permeability, which is formed on a surface of the positive electrode plate 3 by use of a flame-retardant material. The porous layer is formed by applying, to the surface of the positive electrode plate 3, a hot melt produced by melting the flame-retardant material consisting of a thermoplastic resin.

Description

  The present invention relates to a non-aqueous electrolyte battery provided with a non-aqueous electrolyte.

Non-aqueous electrolyte batteries using non-aqueous electrolytes such as lithium ion secondary batteries have high voltage, high energy density, and can be reduced in size and weight, so power supplies for information terminals such as personal computers and mobile phones It is widely spread around the world. As a non-aqueous electrolyte used in a non-aqueous electrolyte battery, a solution in which a supporting salt such as LiPF ₆ is dissolved in an aprotic organic solvent such as an ester compound and an ether compound is generally used. However, since aprotic organic solvents are flammable, there are problems in terms of safety, such as ignition when liquid leaks from a battery or abnormal heat is generated.

  Recently, studies are being made to expand non-aqueous electrolyte batteries to power supply applications for large equipment such as power storage power supplies and electric vehicle power supplies. Therefore, it is an important problem to increase the safety of the nonaqueous electrolyte battery for increasing the size of the battery. As a technique for improving the safety of a non-aqueous electrolyte battery, for example, in Japanese Patent Laid-Open No. 2000-173619 (Patent Document 1), the negative electrode surface is coated with a phosphazene monomer that is a flame-retardant material, and the ignition and burst of the battery A technique for suppressing the above is disclosed.

JP 2000-173619 A (paragraph [0042], Table 1)

  As described above, when the electrode surface is coated with a flame retardant material, battery ignition due to an increase in the internal temperature of the non-aqueous electrolyte battery and expansion of the battery due to an increase in internal pressure can be suppressed. However, the presence of the flame retardant layer formed on the electrode surface hinders ion conductivity between the electrode and the electrolytic solution, resulting in a problem in that the original performance of the battery such as discharge characteristics is deteriorated.

  An object of the present invention is to provide a nonaqueous electrolyte battery that hardly affects battery performance such as discharge characteristics even when a flame retardant layer is formed on the surface of an electrode or the like.

  Another object of the present invention is to provide a non-aqueous electrolyte battery capable of suppressing ignition and rupture of a battery even when a sudden discharge due to an internal short circuit occurs while maintaining discharge characteristics. .

  This invention makes the object of improvement the non-aqueous electrolyte battery provided with the non-aqueous electrolyte as the battery electrolyte. In the nonaqueous electrolyte battery of the present invention, a porous layer using a flame retardant material is formed on at least one surface of a positive electrode plate, a negative electrode plate, and a separator. The at least one surface of the positive electrode plate, the negative electrode plate, and the separator means, for example, a surface facing the separator of the positive electrode plate, a surface facing the separator of the negative electrode plate, or a surface of the separator. The porous layer is formed by applying a hot melt obtained by melting a flame retardant material to the surface of a positive electrode or the like. In the specification of the present application, the flame retardant material is a thermoplastic resin that is solid at normal temperature but plasticizes or fluidizes when heated and has a property of preventing ignition of the non-aqueous electrolyte solution and insoluble in the non-aqueous electrolyte solution. Hot melt is obtained by melting a flame-retardant material made of such a thermoplastic resin. When applying the hot melt to the surface of the positive electrode plate or the like, the hot melt is sprayed from the nozzle toward the surface of the positive electrode plate or the like. As a result, the coating layer of the flame retardant material formed by applying hot melt to the surface of the positive electrode plate or the like becomes a porous layer having a plurality of pores communicating in the thickness direction like a so-called nonwoven fabric, and has excellent ions Shows permeability. Ion permeability means that ions can pass through the pores of the porous layer. In other words, in the present specification, the porous layer can be expressed as a non-woven coating layer in which a large number of pores communicating with each other in the thickness direction are formed.

  As in the present invention, when a flame retardant layer comprising a porous layer formed by applying a hot melt obtained by melting a flame retardant material is formed on the surface of a positive electrode plate or the like, the surface of the positive electrode plate or the like has ion permeability. In addition, it is possible to form a flame retardant layer exhibiting the property of suppressing the ignition of the electrolyte (this property is expressed as flame retardant in the present specification). The porous layer formed in this way does not affect battery performance during normal battery operation due to ion permeability. However, when a sudden discharge occurs due to an internal short circuit and the temperature inside the battery rises, the flame retardant material melts and demonstrates the function of suppressing the ignition of the non-aqueous electrolyte, increasing the internal temperature and internal pressure of the battery. Can be suppressed. Therefore, according to the present invention, it is possible to reduce the risk of battery ignition, ignition or battery expansion, rupture, etc. without degrading battery performance, and to obtain a highly safe non-aqueous electrolyte battery. Can do.

  Since the hot melt exhibits adhesiveness and cures when the temperature decreases, the hot melt made of a flame retardant material applied to the surface of the positive electrode plate or the like is held as it is attached to the surface of the positive electrode plate or the like. . Therefore, when the battery is assembled, dropping of the porous layer does not cause a problem. Moreover, since the porous layer used by this invention has ion permeability, it can suppress that the ionic conductivity between the surfaces, such as the positive electrode plate in which the porous layer was formed, and electrolyte solution falls. Therefore, according to the present invention, a highly safe non-aqueous electrolyte battery is provided without deteriorating the discharge characteristics required for the non-aqueous electrolyte battery such as high voltage performance, high discharge capacity, and large current discharge performance. can do.

  In the non-aqueous electrolyte battery, the porosity of the porous layer is preferably 30 to 70% from the viewpoint of maintaining discharge characteristics such as high discharge capacity and large current discharge performance. The porosity (P) can be defined as a percentage (P = V2 / V1 × 100) representing the volume V2 of the pores in the volume V1 of the porous layer. The porosity (P) is P = [1-d2 / d1] × 100, where d1 is the specific gravity (true specific gravity) of the flame retardant material and d2 is the specific gravity (apparent specific gravity) of the porous layer. What was computed from the formula can also be used.

  In the present invention, a porous layer having a porosity of 30 to 70% can be formed on the surface of a positive electrode plate or the like by applying hot melt as described above. In addition, when the porosity is less than 30%, the ion permeability or ion conductivity is lowered, so that the discharge characteristics are lowered. On the other hand, when the porosity exceeds 70%, the bonding area between the porous layer and the surface of the positive electrode plate or the like decreases, so that the bonding strength of the porous layer decreases and the porous layer easily falls off. . Furthermore, if the porosity exceeds 80%, the porous layer can easily fall off from the surface of the positive electrode plate, etc., making it impossible to exert the function of the flame retardant material and ensuring the safety of the nonaqueous electrolyte battery. Can not do it.

  The method of applying the hot melt by melting the flame retardant material is arbitrary. However, in order to form a porous layer having the above-described porosity, it is preferable to use a non-contact coating method as a method of applying hot melt to the surface of a positive electrode plate or the like. The non-contact coating method is a known method for applying hot melt, and is a method in which hot melt is sprayed and applied to the surface of the application object without bringing the nozzle of the application device into contact with the application object. In the present invention, a hot melt obtained by heating and melting a flame-retardant material that is solid at room temperature at a temperature of 90 ° C. or higher is applied to a positive electrode plate at a predetermined coating speed using a commercially available hot melt coating apparatus (control coat gun). The linear hot melt sprayed on the surface of the film is applied by swinging at least one of the nozzle and the positive electrode plate so that they overlap irregularly in the thickness direction. If it does in this way, the nonwoven fabric-like porous layer which has the porosity which shows the required ion permeability on the surface of a positive electrode plate etc. by a simple method can be formed. The non-woven fabric means a state having a random fibrous three-dimensional network structure and no directionality in mechanical strength.

  From the viewpoint of applying the flame retardant material in a hot melt state to the surface of the positive electrode plate or the like, it is preferable to use a flame retardant material having a melting point of 90 ° C. or higher. A flame-retardant material having a melting point of 90 ° C. or higher is solid at room temperature, but is plasticized or fluidized at 90 ° C. or higher. Since the ignition temperature of the electrolyte is often higher than 90 ° C., using such a flame retardant material, the flame retardant material softens when the temperature in the battery approaches the ignition temperature of the electrolyte, Until then, since it does not soften, safety can be improved without affecting the battery performance. From the viewpoint of ensuring the porosity of the porous layer formed on the surface of the positive electrode plate or the like, it is preferable to use a flame-retardant material having a viscosity at the time of melting of 1000 to 3500 mPa · s. If the viscosity at the time of melting is less than 1000 mPa · s, the viscosity of the hot melt is too low to form a porous layer having ion permeability. Therefore, the ionic conductivity of the electrode is hindered and the high rate discharge characteristics are deteriorated. If the viscosity at the time of melting exceeds 3500 mPa · s, the viscosity of the hot melt is too high and the hot melt is discharged from the nozzle in a discontinuous state, so it is difficult to form a non-woven fabric layer. . As a result, the high rate discharge characteristics are degraded.

  In other words, the porous layer is preferably configured so that the content of the flame retardant material is in the range of 3.5 to 7.5% by weight with respect to the positive electrode active material of the positive electrode plate. The content of the flame retardant material is expressed by the weight percent of the flame retardant material with respect to 100% by weight of the positive electrode active material because the flame retardant material captures (traps) oxygen radicals generated at the positive electrode during abnormal heat generation of the battery. In consideration of the fact that a flame retardant effect can be obtained, the amount of the flame retardant material used is determined based on the positive electrode active material from which oxygen radicals are generated. In addition, in the range where the content of the flame retardant material is less than 3.5% by weight with respect to the positive electrode active material of the positive electrode plate, although there is a certain effect, the amount of the flame retardant material is small, so the flame retardant material There is a possibility that the effect of disposing the battery in the battery cannot be fully exhibited. In addition, in the range where the content of the flame retardant material exceeds 7.5% by weight with respect to the positive electrode active material, since the ion conductivity is inhibited by increasing the volume of the porous layer, the battery characteristics are deteriorated. . Even if the battery characteristics deteriorate, the content of the flame retardant material may be in a range exceeding 7.5% by weight for the purpose of improving safety. However, in order to sufficiently secure the safety of the nonaqueous electrolyte battery and maintain the battery performance, the content of the flame retardant material with respect to the positive electrode active material is in the range of 5.0 to 7.5% by weight. It is preferable to do this.

  As the flame retardant material, for example, a phosphazene compound that is solid at room temperature but melts and becomes hot melt when heated can be used. By applying such a phosphazene compound as a hot melt, a porous layer as a flame retardant layer is firmly attached to the surface of a positive electrode plate or the like without any other components such as a binder. Can do. The phosphazene compound has a property of capturing (trapping) oxygen in the non-aqueous electrolyte (for example, oxygen radicals generated at the positive electrode when the battery is abnormally heated) due to its structure. By utilizing this property and forming the phosphazene compound on the surface of the positive electrode plate, the thermal runaway reaction of the battery can be efficiently suppressed.

  As such a phosphazene compound, in particular, a cyclic phosphazene compound represented by the general formula (I) can be used.

In the above formula, R1 to R6 are organic groups having 1 to 10 carbon atoms, and R1 to R6 may all have the same carbon number or different carbon numbers. Examples of usable organic groups for R1 to R6 include methyl groups, ethyl groups, propyl groups, butyl groups, pentyl groups, hexyl groups, heptyl groups, octyl groups, nonyl groups, decyl groups and other alkyl groups; methoxy groups , Alkoxy groups such as ethoxy group, propoxy group, butoxy group, pentoxy group, hexyloxy group, heptyloxy group, octyloxy group; methoxymethyl group, ethoxymethyl group, propoxymethyl group, butoxymethyl group, methoxyethyl group, ethoxy Alkoxy group such as ethyl group, propoxyethyl group, methoxypropyl group, ethoxypropyl group, propoxypropyl group; vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 1-pentenyl group, 3-butenyl Group, 3-pentenyl group, 2-fluoroethenyl group, , 2-difluoroethenyl group, 1,2,2-trifluoroethenyl group, 4,4-difluoro-3-butenyl group, 3,3-difluoro-2-propenyl group, 5,5-difluoro-4-pentenyl Alkenyl groups such as groups; aryl groups such as phenyl groups; aryloxy groups such as phenoxy groups; and the like. Among these, a methyl group, an ethyl group, and a 1,2,2-trifluoroethenyl group are preferable.

  In addition, the hydrogen atom in R1-R3 may be substituted with a fluorine atom. When the hydrogen atoms in R1 to R3 are replaced with fluorine atoms, chemical stability is easily improved.

(A) is the schematic shown in the state which looked through the inside of the lithium ion secondary battery used as a nonaqueous electrolyte battery of this invention, (B) is the IB-IB sectional view taken on the line of (A). In the non-aqueous electrolyte battery of this invention, it is the photograph which expanded and image | photographed the surface of the porous layer formed in the surface of a positive electrode plate 150 times with the optical microscope. It is a figure which shows the relationship between the porosity of the porous layer formed by apply | coating the hot melt which melted the flame-retardant material (phosphazene compound) on the surface of the positive electrode plate, and high-rate discharge capacity. It is a figure which shows the relationship between the viscosity at the time of the fusion | melting of the flame-retardant material (phosphazene compound) used by this invention, and a high rate discharge capacity.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 (A) is a schematic diagram showing the inside of a lithium ion secondary battery as an embodiment of the nonaqueous electrolyte battery of the present invention in a transparent state, and FIG. IB is a cross-sectional view of IB-IB. The lithium ion secondary battery 1 includes a positive electrode plate 3 provided with a positive electrode lead terminal 3a, a negative electrode plate 5 provided with a negative electrode lead terminal 5a, and a separator 7 disposed between the positive electrode plate 3 and the negative electrode plate 5. . The positive electrode plate 3, the negative electrode plate 5, and the separator 7 are stacked to form a stacked body 9. The lithium ion secondary battery 1 has a structure in which the laminate 9 is disposed in the case 11 in a state where the positive electrode lead terminal 3a and the negative electrode lead terminal 5a can be connected to the outside.

The lithium ion secondary battery 1 was produced as follows. First, a nonaqueous electrolytic solution is prepared. The non-aqueous electrolyte was prepared as a solution in which LiPF ₆ was dissolved at 1 mol / L in a mixed solvent composed of 50% by volume of ethylene carbonate and 50% by volume of dimethyl carbonate.

Next, a positive electrode plate is produced. Lithium cobalt composite oxide (LiCoO ₂ ) is used as the positive electrode active material of the positive electrode plate. First, this lithium cobalt oxide, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder are mixed at a mass ratio of 90: 5: 5, and this is dispersed in a solvent of N-methylpyrrolidone. A slurry was prepared. The slurry was applied to an aluminum foil as a positive electrode current collector and dried, followed by press working to produce a positive electrode sheet.

  Furthermore, a hot melt obtained by melting a flame retardant material was applied to the surface of the positive electrode sheet. As the flame retardant material, a cyclic phosphazene compound (hereinafter referred to as phosphazene compound A) in which two of all Rs are phenoxy groups, two are phenyl groups, and two are dimethylamino groups in the general formula (I) is used. . This cyclic phosphazene compound is solid at room temperature, but when heated, it melts into a hot melt. By applying such a phosphazene compound as a hot melt, a porous layer as a flame retardant layer can be reliably adhered to the surface of a positive electrode plate or the like without any other components such as a binder. Can do.

  The flame-retardant material was applied by a non-contact coating method. Specifically, using a control gun CC200 (trademark) manufactured by Nordson as a coating device, a hot melt of phosphazene compound A melted at 160 ° C. is applied onto the surface of the positive electrode sheet at a coating speed of 45 m / min. The coating layer was formed on the surface of the positive electrode sheet so that the sprayed hot melt in the striated state was in a non-woven fabric state that irregularly overlapped in the thickness direction. FIG. 2 is a photograph taken by enlarging the surface of the coating layer formed on the surface of the positive electrode sheet 150 times with an optical microscope. As this micrograph shows, the coating layer formed on the surface of the positive electrode sheet is a non-woven porous layer. The positive electrode sheet on which such a coating layer was formed was cut into 10 cm × 20 cm, and a current collector tab of aluminum foil was welded to produce a positive electrode plate.

  Next, a negative electrode plate is produced. Artificial graphite is used as the negative electrode active material. This artificial graphite and polyvinylidene fluoride as a binder were mixed at a mass ratio of 90:10, and this was dispersed in a solvent of N-methylpyrrolidone to prepare a slurry. The slurry was applied to a copper foil negative electrode current collector and dried, followed by pressing to prepare a negative electrode sheet. The negative electrode sheet was cut to 10 cm × 20 cm, and a nickel foil current collecting tab was welded to the cut sheet to prepare a negative electrode plate.

  A positive electrode plate, a negative electrode plate, and a separator sheet made of polyethylene were sandwiched between the positive electrode plate and the negative electrode plate thus prepared, and the positive electrode plate, the negative electrode plate, and the separator sheet were stacked to prepare a laminated group so that the battery capacity was 8 Ah. The laminated group was inserted into an exterior material (case 11) made of a heat-sealing film (aluminum laminate film) and opened at one end, and the prepared non-aqueous electrolyte was poured into the exterior material. Thereafter, the exterior material was evacuated, and the opening of the exterior material was quickly heat-sealed to produce a non-aqueous electrolyte battery (lithium ion secondary battery 1) having a flat laminated battery structure.

  The flame retardancy of the thus produced nonaqueous electrolyte battery was evaluated by the method shown in (1) below. Specifically, the flame retardancy of Experimental Examples 1 to 7 in which the coating amount of the flame retardant material (phosphazene compound A) was changed was evaluated. In addition, the application quantity of a flame-retardant material (phosphazene compound A) is shown by weight% with respect to a positive electrode active material. The evaluation results of flame retardancy are as shown in Table 1.

(1) Nail penetration safety test The manufactured laminate battery was subjected to a safety test by nail penetration. In the nail penetration test method, a charge / discharge cycle with a current density of 0.1 mA / cm ² was repeated twice in a voltage range of 4.2 to 3.0 V in an environment of 25 ° C., and then 4.2 V. Until the battery was charged. After that, under the same temperature condition of 25 ° C., a stainless steel nail with a shaft diameter of 3 mm was pierced perpendicularly to the center of the side of the battery at a speed of 0.5 cm / s, and the battery was ignited or smoked. In addition, it was confirmed whether the battery was ruptured or expanded.

As shown in Table 1, in the example in which the flame retardant material (phosphazene compound A) was not applied (Experimental Example 1) and in the example in which 1.0% by weight was applied (Experimental Example 2), the smoke of the battery was confirmed, and the flame retardancy was confirmed. In the case where the material (phosphazene compound A) was not applied (Experimental Example 1), the example where 1.0% by weight was applied (Experimental Example 2) and the example where 2.5% by weight was applied (Experimental Example 3), the expansion of the battery was confirmed. It was. From these results, non-aqueous electrolyte batteries (Experimental Examples 4 to 7) containing 3.5 to 10.0% by weight of a flame retardant material (phosphazene compound A) were ignited and smoked due to thermal runaway during an internal short circuit. It was found that the battery can be prevented from bursting and expanding, and the safety of the non-aqueous electrolyte battery is increased. That is, when the application amount of the flame retardant material (phosphazene compound A) is less than 3.5% by weight, the effect of suppressing the thermal runaway of the battery is insufficient, and the application amount (weight) of the flame retardant material is at least the positive electrode. It turned out that it is preferable that it is 3.5 weight% or more with respect to the weight of an active material.

  In addition, the relationship between the state of the porous layer and the discharge characteristics was examined for the manufactured laminated battery. The discharge characteristics were confirmed by the method shown in (2) below. Specifically, when the porosity of the porous layer formed with the flame retardant material (phosphazene compound A) applied as 3.5% by weight with respect to the weight of the positive electrode active material was changed (Experimental Example 8) The high rate discharge capacity of -18) was confirmed. The porosity is calculated from the equation P = [1-d2 / d1] × 100, where d1 is the specific gravity (true specific gravity) of the flame retardant material and d2 is the specific gravity (apparent specific gravity) of the porous layer. did. The results are as shown in Table 2 and FIG.

(2) High-rate discharge test A high-rate discharge test was performed on the produced nonaqueous electrolyte battery (laminated battery). After charging at 25 ° C. under the same conditions as the nail penetration safety test of (1) above (same conditions as in the initial charge / discharge process), a constant current discharge with a current of 24 A and a final voltage of 3.0 V was performed. The obtained discharge capacity was defined as a high rate discharge capacity.

As shown in Table 2 and FIG. 3, when the high rate discharge capacity of an example (experimental example 8) in which the flame retardant material (phosphazene compound A) is not applied is 100%, the porosity is 10% to 25% (experimental example) In 9 to 11), the high rate discharge capacity was less than 95%. This indicates that the ion permeability or the ion conductivity is lowered and the discharge characteristics are lowered. On the other hand, when the porosity was 30% to 70% (Experimental Examples 12 to 16), the high rate discharge capacity was over 95%. In addition, when the porosity is 80% (Experimental Example 17), it is confirmed that the porous layer easily falls off, and when the porosity is 90% (Experimental Example 18), the porous layer easily falls off from the surface of the positive electrode plate. It was done. These tendencies are thought to be due to a decrease in the bonding area between the porous layer and the surface of the positive electrode plate or the like, resulting in a decrease in the bonding strength of the porous layer. From these results, it was found that the porosity of the porous layer formed on the surface of the positive electrode plate is preferably in the range of 30 to 70%. That is, by applying a flame retardant material (phosphazene compound A) so that the porosity of the porous layer is 30 to 70% on the surface of the positive electrode plate, the discharge rate is higher than that of the uncoated phosphazene compound. It was found that there was little decrease in capacity and little effect on battery performance.

  Furthermore, the relationship between the coating amount of the flame retardant material (phosphazene compound A) and the discharge characteristics was examined for the manufactured laminated battery. The discharge characteristics were confirmed by the method shown in (2) as in the case of examining the relationship between the porosity and the discharge characteristics. Specifically, in Examples 19 to 25 in which the coating amount of the flame retardant material (phosphazene compound A) (% by weight with respect to the weight of the positive electrode active material) was changed so that the porosity of the porous layer was 50%. A high rate discharge capacity was confirmed. The results are as shown in Table 3.

As shown in Table 3, when the high rate discharge capacity of the example (Experimental Example 19) in which the flame retardant material (phosphazene compound A) is not applied is 100%, the coating amount of the flame retardant material (phosphazene compound A) is 3 In the case of 5 wt% to 7.5 wt% (Experimental Examples 20 to 22), the high rate discharge capacity exceeded 95%. On the other hand, when the coating amount was 10% to 15% (Experimental Examples 23 to 25), the high rate discharge capacity was less than 95%. From these results, it was found that the application amount of the flame retardant material (phosphazene compound A) applied to the surface of the positive electrode plate is preferably in the range of 3.5 to 7.5%. That is, by applying 3.5 to 7.5% by weight of the flame retardant material (phosphazene compound A), the reduction in the high-rate discharge capacity is less than that without applying the flame retardant material (phosphazene compound A). It was found that the influence on the battery performance is reduced. When the content of the flame retardant material is less than 3.5% by weight, the amount of the flame retardant material is small, so that the effect of arranging the flame retardant material in the battery as described above is sufficiently exerted. I can't. When the coating amount of the flame retardant material (phosphazene compound A) exceeds 7.5% by weight, the battery characteristics deteriorate because the thickness of the flame retardant layer (the volume of the porous layer remains unchanged) with the porosity remaining at 50%. ) Increased, the lithium ion movement (ion conductivity) was impeded.

  Moreover, the relationship between the viscosity at the time of application | coating of a flame retardant material (phosphazene compound A) and the discharge characteristic was investigated about the produced laminated battery. The discharge characteristics were confirmed by the method shown in (2) as in the case of examining the relationship between the porosity and the discharge characteristics. Specifically, the coating amount of the flame retardant material (phosphazene compound A) is set to 3.5% by weight with respect to the weight of the positive electrode active material, and the viscosity at the time of melting of the flame retardant material (phosphazene compound A) is changed. The high rate discharge capacity of the experimental examples 26 to 39 was confirmed. The results are as shown in Table 4 and FIG.

As shown in Table 4 and FIG. 4, when the high rate discharge capacity of the example (Experimental Example 26) in which the flame retardant material (phosphazene compound A) is not applied is 100%, the flame retardant material (phosphazene compound A) melts. When the hourly viscosity was less than 1000 mPa · s (Experimental Examples 27 to 29) and 4000 to 6000 mPa · s (Experimental Examples 36 to 38), the high rate discharge capacity was less than 95%. Moreover, when the viscosity at the time of melting was 7000 mPa · s (Experimental Example 39), it was difficult to apply the flame retardant material (phosphazene compound A), and a porous layer could not be formed on the surface of the positive electrode plate. On the other hand, when the viscosity of the flame-retardant material (phosphazene compound A) was 1000 to 3500 mPa · s (Experimental Examples 30 to 35), the high rate discharge capacity exceeded 95%. From these results, it was found that the viscosity of the flame-retardant material (phosphazene compound A) when melted is preferably in the range of 1000 to 3500 mPa · s. Note that the high rate discharge characteristics decreased when the flame-retardant material (phosphazene compound A) had a viscosity of less than 1000 mPa · s because the viscosity of the hot melt was too low and the porous layer having ion permeability was used. Since it cannot be formed, it is considered that the ionic conductivity of the electrode was inhibited. In addition, when the viscosity at the time of melting exceeds 3500 mPa · s, the high rate discharge characteristic is lowered because the viscosity of the hot melt is too high and the hot melt is discharged from the nozzle in a discontinuous state. It is considered that it is difficult to form a nonwoven fabric layer, and the porosity of the porous layer cannot be ensured.

  Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to these embodiments and examples, and modifications based on the technical idea of the present invention are possible. Of course.

  According to the present invention, a flame retardant layer composed of a porous layer formed by applying a hot melt obtained by melting a flame retardant material is formed on the surface of a positive electrode plate or the like. It is possible to form a flame retardant layer having flame retardancy. For this reason, when a rapid discharge occurs due to an internal short circuit and the temperature inside the battery rises, the flame retardant material melts and functions to suppress ignition of the nonaqueous electrolyte, increasing the internal temperature and internal pressure of the battery Can be suppressed. As a result, according to the present invention, it is possible to reduce the risk of battery ignition, ignition, battery expansion, rupture, etc. without degrading battery performance, and to obtain a highly safe non-aqueous electrolyte battery. be able to.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 3 Positive electrode plate 5 Negative electrode plate 7 Separator 9 Laminate 11 Case

Claims (10)

A positive plate, a negative plate and a separator;
A non-aqueous electrolyte battery characterized in that a porous layer having ion permeability formed by applying a hot melt obtained by melting a flame retardant material is formed on the surface of the positive electrode plate.   The non-aqueous electrolyte battery according to claim 1, wherein the porous layer has a porosity of 30 to 70%.   The non-aqueous electrolyte battery according to claim 1, wherein the flame retardant material has a melting point of 90 ° C. or higher and a melt viscosity of 1000 to 3500 mPa · s.   4. The nonaqueous electrolyte battery according to claim 1, wherein the porous layer contains 3.5 to 7.5 wt% of the flame retardant material with respect to the positive electrode active material of the positive electrode plate. .   5. The non-aqueous electrolyte battery according to claim 1, wherein the flame retardant material is a phosphazene compound that is solid at room temperature but melts to become hot melt when heated.   The non-aqueous electrolyte battery according to claim 5, wherein the phosphazene compound is a cyclic phosphazene compound. The non-aqueous electrolyte battery according to claim 6, wherein the cyclic phosphazene compound is a phosphazene compound represented by the general formula (I).
(R1 to R6 in the above formula are the same or different alkyl groups having 1 to 10 carbon atoms, alkoxy groups, alkoxyalkyl groups, alkenyl groups, aryl groups or aryloxy groups. The hydrogen atoms in R1 to R3 are (It may be substituted with a fluorine atom.)   The nonaqueous electrolyte battery according to claim 1, wherein the porous layer is formed on the surface of the positive electrode plate facing the separator.   The non-aqueous electrolyte battery according to claim 1, wherein the porous layer is formed by a non-contact coating method in which the hot melt is sprayed and applied without bringing a nozzle into contact with the surface.   The non-aqueous electrolyte battery according to claim 9, wherein the non-contact coating method is a method in which the hot melt is sprayed from the nozzle in a linear state to form a non-woven coating layer on the surface.