JP2010033869A - Electrode plate for nonaqueous secondary battery and nonaqueous secondary battery using the same - Google Patents

Abstract

When a non-aqueous secondary battery is subjected to an external physical impact or charged by an excessive current, a separator inside the battery is damaged, and a positive electrode plate and a negative electrode plate are contacted to cause an internal short circuit. It is an object of the present invention to provide an electrode plate that can suppress the generation of gas due to the decomposition of the materials of the positive and negative electrode plates and the boiling and decomposition of the electrolytic solution, which are generated with a large calorific value.
A positive electrode plate 3 or a negative electrode mixture paint on which a positive electrode mixture paint is applied on a positive electrode current collector 1 to form a positive electrode mixture layer 2 is applied on a negative electrode current collector 4 to form a negative electrode mixture. After forming the agent layer 5, the porous insulating layer 7 containing tetrapotted whiskers was formed on the outer surface of the positive electrode mixture layer 2 or the negative electrode mixture layer 5.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to an electrode plate for a non-aqueous secondary battery represented by a lithium ion battery and a non-aqueous secondary battery using the same, and particularly to a non-aqueous secondary battery excellent in safety.

Conventionally, lithium secondary batteries, which are widely used as power sources for portable electronic devices, use a carbonaceous material capable of occluding and releasing lithium as a negative electrode, and a metal such as lithium cobalt oxide (LiCoO ₂ ) as a positive electrode. Lithium composite oxide is used as the active material, and this realizes a secondary battery with a high potential and a high discharge capacity. However, with the recent multifunctionalization of electronic and communication devices, more and more The demand for battery safety is increasing as capacity increases.

  Therefore, in general, a separator is formed using an olefin polymer such as polyethylene (PE) or polypropylene (PP), and this is interposed between the positive electrode plate and the negative electrode plate, so that the secondary battery has Safety is ensured by closing the micropores of the separator (shutdown function) by heat generated by excessive current flow.

  However, if the rechargeable secondary battery is accidentally subjected to an external physical shock for some reason or is charged by an excessive current, the separator inside the battery may be damaged. May contact and cause an internal short circuit. When such an internal short-circuit occurs, current concentrates on that part, and as a result, heat is generated. If the heat is large, gas generation due to decomposition of the materials of the positive electrode plate and the negative electrode plate and boiling and decomposition of the electrolyte solution occurs. It had the problem that it might happen.

  Accordingly, in order to prevent the active material from dropping and reattaching and to improve the safety of the nonaqueous secondary battery, a positive electrode plate 23 in which a positive electrode mixture layer 22 is formed on a positive electrode current collector 21 as shown in FIG. In the non-aqueous secondary battery having the negative electrode plate 26 in which the negative electrode mixture layer 25 is formed on the negative electrode current collector 24, a thickness of 0.1 is formed on the surface of either the positive electrode mixture layer 22 or the negative electrode mixture layer 25. It has been proposed to form a porous protective film 27 having a thickness of ˜200 μm (see, for example, Patent Document 1).

Although the battery configuration is different, in order to obtain a lithium secondary battery having excellent charge / discharge cycle life, high electromotive force, and high energy density, it faces the positive electrode plate 32 via a separator 31 as shown in FIG. It has been proposed to form a porous insulating film 34 having a thickness of 5 to 100 nm on the surface of the negative electrode plate 33 by sputtering (see, for example, Patent Document 2).
Japanese Patent No. 3371301 JP-A-6-36800

  However, the prior art of Patent Document 1 is intended to prevent the electrode active material from dropping and reattaching before the electrode plate is housed in the battery case. There was a problem that the safety of the secondary battery could not be guaranteed.

In the prior art of Patent Document 2, a porous insulating film is formed by sputtering on the surface of the negative electrode plate, and the film thickness is desirably 5 to 100 nm. The negative electrode active material has an average particle size of about 20 μm, and the surface of the negative electrode mixture layer has irregularities of about several μm, so the surface of the negative electrode plate is covered with the above thin film There is a problem that it is difficult to ensure the safety of the non-aqueous secondary battery due to an internal short circuit.

  The present invention has been made in view of the above-described conventional problems, and by forming a porous insulating layer containing tetrapotted whiskers on the surface of at least one of the positive electrode mixture layer or the negative electrode mixture layer, An object of the present invention is to provide a non-aqueous secondary battery that can suppress an internal short circuit even when a physical impact is applied from the outside and is excellent in safety.

  In order to achieve the above object, the electrode plate for a non-aqueous secondary battery of the present invention comprises a positive electrode composite in which an active material comprising at least a lithium-containing composite oxide, a conductive material, and a binder are kneaded and dispersed in a dispersion medium. A positive electrode plate in which a positive electrode mixture layer is formed by adhering an agent paint on a positive electrode current collector, or a negative electrode mixture paint in which an active material and a binder made of a material capable of holding at least lithium are kneaded and dispersed in a dispersion medium Is an electrode plate for a non-aqueous secondary battery comprising a negative electrode plate in which a negative electrode mixture layer is formed by adhering to a negative electrode current collector, wherein at least one of a positive electrode mixture layer or a negative electrode mixture layer A porous insulating layer containing tetrapot-shaped whiskers is formed on the outer surface.

  According to the electrode plate for a non-aqueous secondary battery of the present invention, by forming a porous insulating layer containing a tetrapot-shaped whisker on the outer surface of at least one of the positive electrode mixture layer or the negative electrode mixture layer, The binding force between the porous insulating layer and the positive electrode mixture layer or negative electrode mixture layer is large, preventing the positive electrode mixture layer or negative electrode mixture layer from falling off and preventing internal short circuit even when a physical impact is applied from the outside. It is possible to provide a non-aqueous secondary battery that can be suppressed and is excellent in safety.

  In the first aspect of the present invention, a positive electrode mixture paint obtained by kneading and dispersing at least an active material composed of a lithium-containing composite oxide, a conductive material, and a binder with a dispersion medium is adhered onto a positive electrode current collector. A negative electrode mixture is prepared by adhering a negative electrode mixture paint obtained by kneading and dispersing an active material and a binder made of a material capable of holding lithium at least in a dispersion medium on a negative electrode current collector. An electrode plate for a non-aqueous secondary battery comprising a negative electrode plate on which a material layer is formed, comprising a tetrapotted whisker on the outer surface of at least one of a positive electrode mixture layer and a negative electrode mixture layer By forming the insulating layer, the outer surface of the positive electrode mixture layer or the negative electrode mixture layer is protected by the porous insulating layer, thereby preventing the positive electrode mixture layer or the negative electrode mixture layer from falling off and suppressing the internal short circuit. It becomes possible.

  In the second invention of the present invention, the positive electrode mixture layer or the negative electrode mixture layer and the porous material are formed by biting the tip of the tetrapot-shaped whisker into the outer surface of the positive electrode mixture layer or the negative electrode mixture layer. The binding force with the insulating layer can be increased, and the dropping of the positive electrode mixture layer or the negative electrode mixture layer can be effectively suppressed.

  In the third invention of the present invention, the thickness of the porous insulating layer is made thinner than the thickness of the separator interposed between the electrode plates, so that the porous insulating layer does not hinder ion conductivity and the electrode mixture layer. Thus, it is possible to provide a high-capacity non-aqueous secondary battery excellent in safety while suppressing an internal short circuit.

  In the fourth invention of the present invention, the porous non-aqueous electrolyte necessary for fully exhibiting the function of charge / discharge characteristics is obtained by setting the porosity of the porous insulating layer to 30% to 70%. It can be held in the insulating layer.

  In the fifth aspect of the present invention, the amount of whisker contained in the porous insulating layer is set to 50 wt% or more and 97 wt% or less, so that a porous insulating layer having excellent mechanical strength even when it is thinned is obtained. Can be obtained.

  In the sixth invention of the present invention, the whisker is constituted by a core part and a fibrous part extending in a different four-axis direction from the core part, and the fibrous part has a length of 0.1 to 10 μm and 3 to 70. By having a configuration having an aspect ratio, the porous insulating layer exhibits an isotropic reinforcement effect in all directions to prevent warping of the porous insulating layer and to obtain a porous insulating layer having excellent flatness It becomes possible.

  In the seventh invention of the present invention, a whisker having a tetrapot shape necessary for exerting an isotropic reinforcing effect in all directions in the porous insulating layer is obtained by constituting the whisker with zinc oxide whisker. It can be easily obtained.

In the eighth invention of the present invention, the zinc oxide whisker has a specific resistance of 10 ⁸ to 10 ¹² Ω · cm, so that the porous insulation having a large specific resistance required to suppress internal short circuit is provided. It becomes possible to obtain a layer.

  In the ninth aspect of the present invention, a positive electrode mixture paint obtained by kneading and dispersing at least an active material composed of a lithium-containing composite oxide, a conductive material, and a binder with a dispersion medium is adhered onto a positive electrode current collector. A negative electrode mixture coating material prepared by kneading and dispersing an active material and a binder made of a material capable of holding lithium at least in a dispersion medium is adhered onto the negative electrode current collector by forming a positive electrode plate on which the positive electrode mixture layer is formed. A nonaqueous secondary battery in which a separator is interposed between a negative electrode plate on which an agent layer is formed and wound or laminated in a spiral shape to enclose a battery case together with a nonaqueous electrolyte solution in a battery case, the positive electrode plate Alternatively, by using the electrode plate for a non-aqueous secondary battery according to any one of the first to eighth aspects of the present invention for at least one of the negative electrode plates, the outer surface of the positive electrode mixture layer or the negative electrode mixture layer is Internal short by protecting with porous insulation layer It is possible to provide a nonaqueous secondary battery having excellent safety can be suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing components of an electrode group 9 before winding in a non-aqueous secondary battery according to an embodiment of the present invention. In the figure, an electrode plate for a non-aqueous secondary battery of the present invention comprises a positive electrode plate 3 in which a positive electrode mixture paint is applied on a positive electrode current collector 1 to form a positive electrode mixture layer 2, and a negative electrode mixture paint. After coating on the negative electrode current collector 4 to form the negative electrode mixture layer 5, the negative electrode plate 6 in which the porous insulating layer 7 containing tetrapot-like whiskers is formed on the outer surface of the negative electrode mixture layer 5. It is configured. An electrode group 9 is configured by winding a separator 8 between the positive electrode plate 3 and the negative electrode plate 6 in a spiral shape in the arrow direction A.

  FIG. 2 is a model diagram showing the main part of the porous insulating layer 7 formed on the outer surface of the electrode mixture layer in the electrode plate for a non-aqueous secondary battery according to one embodiment of the present invention. In the figure, the porous insulating layer 7 is composed of a tetrapot-shaped whisker 10 and a binder 11, and the binder 11 is a rubber-based material for imparting flexibility to the porous insulating layer 7. The binder 11 is preferably used.

  FIG. 3 is a model diagram showing the state of the interface between the electrode mixture layer and the porous insulating layer 7 in the electrode plate for a non-aqueous secondary battery according to one embodiment of the present invention. Here, after forming the porous insulating layer 7 on the outer surface of the positive electrode mixture layer 2 or the negative electrode mixture layer 5, the positive electrode plate 3 or the negative electrode plate 6 is pressed to form a tetrapot as shown in FIG. The tip of the whisker 10 is bitten into the outer surface of the positive electrode mixture layer 2 or the negative electrode mixture layer 5, and the binding force between the porous insulating layer 7 and the positive electrode mixture layer 2 or the negative electrode mixture layer 5 is caused by the anchor effect. By raising, it is possible to effectively suppress the dropping of the positive electrode mixture layer 2 or the negative electrode mixture layer 5.

  FIG. 4 is a cross-sectional view showing components of the electrode group 9 before winding in a non-aqueous secondary battery according to another embodiment of the present invention. In the figure, the electrode plate for a non-aqueous secondary battery of the present invention is formed by applying a positive electrode mixture paint on the positive electrode current collector 1 to form the positive electrode mixture layer 2, and then the outer surface of the positive electrode mixture layer 2. And a negative electrode plate 6 in which a negative electrode mixture layer 5 is formed by applying a positive electrode plate 3 on which a porous insulating layer 7 containing tetrapot-like whiskers is formed and a negative electrode mixture paint on a negative electrode current collector 4. Has been. An electrode group 9 is configured by winding a separator 8 between the positive electrode plate 3 and the negative electrode plate 6 in a spiral shape in the arrow direction A.

  FIG. 5 is a cross-sectional view showing components of the electrode group 9 before winding in a non-aqueous secondary battery according to another embodiment of the present invention. In the figure, the electrode plate for a non-aqueous secondary battery of the present invention is formed by applying a positive electrode mixture paint on the positive electrode current collector 1 to form the positive electrode mixture layer 2, and then the outer surface of the positive electrode mixture layer 2. After forming the negative electrode mixture layer 5 by coating the negative electrode current collector 4 with the positive electrode plate 3 and the negative electrode mixture paint on which the porous insulating layer 7 containing tetrapot-like whiskers is formed on the negative electrode mixture, The negative electrode plate 6 has a porous insulating layer 7 containing tetrapotted whiskers formed on the outer surface of the layer 5. An electrode group 9 is configured by winding a separator 8 between the positive electrode plate 3 and the negative electrode plate 6 in a spiral shape in the arrow direction A.

  First, the thickness of the porous insulating layer 7 is preferably thinner from the viewpoint of, for example, not inhibiting the ionic conductivity of the lithium ion secondary battery and keeping the internal resistance of the battery small. From the standpoint of ensuring the insulation of the outer surface, a thicker one is preferable. However, in the present invention, the thickness of the porous insulating layer 7 is preferably thinner than the thickness of the separator 8 shown in FIG.

  More specifically, the thickness of the porous insulating layer 7 formed on the negative electrode plate 6 shown in FIG. 1 is set to be thicker than the unevenness of the outer surface of the negative electrode mixture layer 5 and less than half the thickness of the separator 8. preferable. For example, when the unevenness of the outer surface of the negative electrode mixture layer 5 is 2 μm and the thickness of the separator 8 is 20 μm, it can be said that the thickness of the porous insulating layer 7 is preferably 2 μm or more and 10 μm or less.

  Further, when the porosity of the porous insulating layer 7 is 30% or less, the voids through which lithium ions pass through the porous insulating layer 7 are reduced, and the amount of the nonaqueous electrolytic solution that can be held in the porous insulating layer 7 is small. As a result, there is a concern that the cycle life at high temperatures may be reduced.

  On the other hand, in the case of 70% or more, the pore diameter of the porous insulating layer 7 is increased, and the nonaqueous electrolyte is not pushed out by the pumping action from the porous insulating layer 7 having a large pore diameter due to expansion / contraction of the electrode plate accompanying charging / discharging. There is a concern that the cycle life at high temperatures may be reduced due to a decrease in the amount of the water electrolyte. Therefore, the porosity of the porous insulating layer 7 is preferably in the range of 30% to 70%, and more preferably in the range of 35% to 65%.

  When the amount of whisker contained in the porous insulating layer 7 is 50% or less, the mechanical strength of the porous insulating layer 7 is insufficient and a porous structure necessary for holding a sufficient non-aqueous electrolyte is obtained. There are concerns that it will be difficult to maintain. On the other hand, in the case of 97% or more, there is a concern that it is difficult to maintain the porous structure because the amount of the binder necessary for bonding the whiskers is insufficient.

  Therefore, the amount of whisker contained in the porous insulating layer 7 is preferably in the range of 50% by weight to 97% by weight, and more preferably in the range of 70% by weight to 97% by weight.

The tetrapot-shaped whisker 10 shown in FIG. 2 includes a core portion 10a and a fibrous portion 10b extending from the core portion 10a in different four-axis directions. The fibrous portion 10b has a length of 0.1 to 10 μm. It is preferable that the aspect ratio is 3 to 70, and this shape effect has an isotropic reinforcement effect in all directions in the porous insulating layer 7, thereby preventing warping of the porous insulating layer 7 and excellent flatness. A porous insulating layer 7 can be obtained.

As the tetrapot-shaped whisker 10 having the above specific structure, for example, zinc oxide whisker obtained by subjecting metallic zinc to an oxidation heat treatment in a special atmosphere is preferable. The specific resistance of this zinc oxide whisker varies greatly depending on its generation conditions and impurity doping conditions, and is in the range of 10 ⁻² to 10 ¹² Ω · cm. However, when used as a filler for the porous insulating layer 7, ^{8 ~10Ω 12} · range of cm is ^preferred, further preferably ¹⁰ 9 ~10 ¹¹ Ω · cm.

  Next, the positive electrode plate 3 puts a positive electrode active material, a conductive material, and a binder in an appropriate dispersion medium, and mixes and disperses them with a disperser such as a planetary mixer, and is applied to the positive electrode current collector 1 such as an aluminum foil. A positive electrode mixture paint is prepared by kneading while adjusting to an optimum viscosity.

  Here, as the positive electrode active material, for example, lithium cobaltate and modified products thereof (such as lithium cobaltate in which aluminum or magnesium is dissolved), lithium nickelate and modified products thereof (partially nickel is substituted with cobalt) Composite oxides such as lithium manganate and modified products thereof.

  As the conductive material at this time, for example, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, and various graphites may be used alone or in combination.

  As the binder at this time, for example, polyvinylidene fluoride (PVdF), a modified polyvinylidene fluoride, polytetrafluoroethylene (PTFE), a rubber particle binder having an acrylate unit, and the like can be used. It is also possible to mix an acrylate monomer or an acrylate oligomer having a reactive functional group introduced into the binder.

  The positive electrode mixture paint prepared as described above is applied onto the positive electrode current collector 1 made of, for example, an aluminum foil using a die coater, dried, pressed to a predetermined thickness, and then stipulated. By slitting into a width and a length, a long belt-like positive electrode plate 3 is obtained.

  On the other hand, the negative electrode plate 6 is suitable for application to the negative electrode current collector 4 such as a copper foil by putting a negative electrode active material and a binder in an appropriate dispersion medium and mixing and dispersing the mixture using a dispersing machine such as a planetary mixer. A negative electrode mixture paint is prepared by kneading while adjusting the viscosity.

  Here, as the negative electrode active material, for example, various natural graphites and artificial graphites, silicon-based composite materials such as silicide, and various alloy composition materials can be used. As the binder at this time, polyvinylidene fluoride and modified products thereof can be used. However, from the viewpoint of improving the acceptability of lithium ions, styrene-butadiene copolymer rubber particles (SBR) or a modified product thereof and a cellulose resin such as carboxymethyl cellulose (CMC) are used in combination. It is preferable to use a styrene-butadiene copolymer rubber particle or a modified product thereof added with a small amount of the above cellulose resin.

  After applying the negative electrode mixture paint prepared as described above onto a negative electrode current collector 4 made of, for example, copper foil using a die coater, drying, pressing to compress to a predetermined thickness, By slitting into a width and a length, a long strip-like negative electrode plate 6 is obtained.

  Hereinafter, the nonaqueous secondary battery of the present invention using the electrode plate for a nonaqueous secondary battery in which the porous insulating layer 7 is formed on the outer surface of at least one of the positive electrode plate 3 and the negative electrode plate 6 described above will be described. . FIG. 6 is a perspective view of a cylindrical lithium secondary battery 18 as an example of a non-aqueous secondary battery cut vertically.

  In the cylindrical lithium secondary battery 18 of FIG. 6, the outer surface of at least one of the positive electrode plate 3 using a composite lithium oxide as an active material or the negative electrode plate 4 using a material capable of holding lithium as an active material is provided. The electrode group 9 is produced by winding the separator 8 between the electrode plates for the non-aqueous secondary battery on which the porous insulating layer 7 is formed, and winding it in a spiral shape.

  The electrode group 9 is housed inside the bottomed cylindrical battery case 12 while being insulated from the battery case 12 by the insulating plate 13, while the negative electrode lead 14 led out from the lower part of the electrode group 9 is connected to the battery case 12. The positive electrode lead 15 led out from the upper part of the electrode group 9 is connected to the sealing plate 16 while being connected to the bottom.

  The battery case 12 is filled with a sealing plate 16 having a sealing gasket 17 attached to the periphery thereof after the non-aqueous electrolyte solution (not shown) made of a predetermined amount of a non-aqueous solvent is injected. The opening of the case 12 is bent inward and crimped.

  Here, the separator 8 may have any composition that can withstand the use range of the non-aqueous secondary battery, but it is preferable to use a microporous film of an olefin resin such as polyethylene or polypropylene, in particular, in a single or composite manner. . The thickness of the separator 8 is preferably 10 to 25 μm.

In the electrolytic solution at this time, various lithium compounds such as LiPF ₆ and LiBF ₄ can be used as an electrolyte salt. Further, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (MEC) can be used alone or in combination as a solvent. Further, in order to form a good film on the positive electrode plate 3 or the negative electrode plate 6 and to ensure stability during overcharge, vinylene carbonate (VC), cyclohexylbenzene (CHB), and modified products thereof are used. Is preferred.

  Hereinafter, an embodiment of the present invention in a specific embodiment will be described in more detail with reference to the drawings. First, 100 parts by weight of lithium cobaltate as an active material, 2 parts by weight of acetylene black as a conductive material with respect to 100 parts by weight of the active material, and 2 parts by weight of polyvinylidene fluoride as a binder with respect to 100 parts by weight of the active material Was mixed with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader to prepare a positive electrode mixture paint.

  Next, as shown in FIG. 1, this positive electrode mixture paint was applied to a positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm, dried, and then pressed to make the thickness of the positive electrode mixture layer 2 on one side 75 μm. did. Thereafter, the positive electrode plate 3 was produced by slitting to a specified width of the cylindrical lithium ion secondary battery 18.

  On the other hand, 100 parts by weight of artificial graphite as the active material of the negative electrode, and 2.5 parts by weight of styrene-butadiene copolymer rubber particle dispersion (solid content 40% by weight) as the binder with respect to 100 parts by weight of the active material ( 1 part by weight in terms of solid content of the binder), 1 part by weight of carboxymethyl cellulose as a thickener with respect to 100 parts by weight of the active material, and an appropriate amount of water, and agitation in a double-arm kneader. An agent paint was prepared.

  Next, as shown in FIG. 1, this negative electrode mixture paint was applied to a negative electrode current collector 4 made of a tough pitch copper foil having a thickness of 10 μm, dried and then pressed to make the thickness of the negative electrode mixture layer 5 on one side of 85 μm. did.

  Further, 100 parts by weight of zinc oxide whisker (Panatetra) manufactured by Matsushita Amtech Co., Ltd. and 100 parts by weight of polyacrylonitrile modified rubber (BM-720H) manufactured by Nippon Zeon Co., Ltd. as binders are used. 4 parts by weight in terms of solid content was mixed with an appropriate amount of N-methyl-2-pyrrolidone with a double-arm kneader to prepare a coating material for the porous insulating layer 7.

  As shown in FIG. 1, the coating material for the porous insulating layer 7 is applied to the outer surface of the negative electrode mixture layer 5 as shown in FIG. 1, dried, and then pressed to form a porous insulating layer having a porosity of 53% and a thickness of 5 μm. 7 was formed. Thereafter, the negative electrode plate 6 was produced by slitting to a specified width of the cylindrical lithium ion secondary battery 18.

  Using the positive electrode plate 3 and the negative electrode plate 6 produced as described above, a polyethylene microporous film having a thickness of 20 μm is wound as a separator 8 in the arrow direction A as shown in FIG. 9 was configured. The electrode group 9 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 14 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12.

Next, the positive electrode lead 15 led out from the upper part of the electrode group 9 is connected to the sealing plate 16, and 1 part of LiPF ₆ and 3 parts by weight of VC are dissolved in a predetermined amount of EC, DMC, and MEC mixed solvent in the battery case 12. A water electrolyte (not shown) was injected. Thereafter, a sealing plate 16 having a sealing gasket 17 attached to the periphery thereof is inserted into the opening of the battery case 12, the opening of the battery case 12 is bent inward, and caulked to seal the cylindrical lithium ion two. The secondary battery 18 was taken as Example 1.

  An embodiment of the present invention will be described with reference to the drawings. First, 100 parts by weight of lithium cobaltate as an active material, 2 parts by weight of acetylene black as a conductive material with respect to 100 parts by weight of the active material, and 2 parts by weight of polyvinylidene fluoride as a binder with respect to 100 parts by weight of the active material Was mixed with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader to prepare a positive electrode mixture paint.

  Next, as shown in FIG. 4, this positive electrode mixture paint was applied to a positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm, dried and then pressed to make the thickness of the positive electrode mixture layer 2 on one side 75 μm. .

  Further, 100 parts by weight of zinc oxide whisker (Panatetra) manufactured by Matsushita Amtech Co., Ltd. and 100 parts by weight of polyacrylonitrile modified rubber (BM-720H) manufactured by Nippon Zeon Co., Ltd. as binders are used. An appropriate amount of N-methyl-2-pyrrolidone in terms of solid content was mixed with a double-arm kneader to prepare a coating material for the porous insulating layer 7.

  As shown in FIG. 4, the coating material for the porous insulating layer 7 is applied onto the outer surface of the positive electrode mixture layer 2 as shown in FIG. 4 and dried and then pressed to form a porous insulating layer having a porosity of 47% and a thickness of 4 μm. 7 was formed. Thereafter, the positive electrode plate 3 was produced by slitting to a specified width of the cylindrical lithium ion secondary battery 18.

On the other hand, 100 parts by weight of artificial graphite as the active material of the negative electrode, and 2.5 parts by weight of styrene-butadiene copolymer rubber particle dispersion (solid content 40% by weight) as the binder with respect to 100 parts by weight of the active material ( 1 part by weight in terms of solid content of the binder), 1 part by weight of carboxymethyl cellulose as a thickener with respect to 100 parts by weight of the active material, and an appropriate amount of water, and agitation in a double-arm kneader. An agent paint was prepared.

  Next, as shown in FIG. 4, this negative electrode mixture paint was applied to a negative electrode current collector 4 made of a tough pitch copper foil having a thickness of 10 μm, dried and then pressed to make the thickness of the negative electrode mixture layer 5 on one side of 85 μm. did. Thereafter, the negative electrode plate 6 was produced by slitting to a specified width of the cylindrical lithium ion secondary battery 18.

  Using the positive electrode plate 3 and the negative electrode plate 6 produced as described above, a 20 μm-thick polyethylene microporous film is wound as a separator 8 in the arrow direction A as shown in FIG. Configured. The electrode group 9 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 14 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12.

Next, the positive electrode lead 15 led out from the upper part of the electrode group 9 is connected to the sealing plate 16, and 1 part of LiPF ₆ and 3 parts by weight of VC are dissolved in a predetermined amount of EC, DMC, and MEC mixed solvent in the battery case 12. A water electrolyte (not shown) was injected. Thereafter, a sealing plate 16 having a sealing gasket 17 attached to the periphery thereof is inserted into the opening of the battery case 12, the opening of the battery case 12 is bent inward, and caulked to seal the cylindrical lithium ion two. The secondary battery 18 was taken as Example 2.

  An embodiment of the present invention will be described with reference to the drawings. First, 100 parts by weight of lithium cobaltate as an active material, 2 parts by weight of acetylene black as a conductive material with respect to 100 parts by weight of the active material, and 2 parts by weight of polyvinylidene fluoride as a binder with respect to 100 parts by weight of the active material Was mixed with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader to prepare a positive electrode mixture paint.

  Next, as shown in FIG. 4, this positive electrode mixture paint was applied to a positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm, dried and then pressed to make the thickness of the positive electrode mixture layer 2 on one side 75 μm. .

  Further, 100 parts by weight of zinc oxide whisker (Panatetra) manufactured by Matsushita Amtech Co., Ltd. and 100 parts by weight of polyacrylonitrile modified rubber (BM-720H) manufactured by Nippon Zeon Co., Ltd. as binders are used. An appropriate amount of N-methyl-2-pyrrolidone in terms of solid content was mixed with a double-arm kneader to prepare a coating material for the porous insulating layer 7.

  As shown in FIG. 4, the coating material for the porous insulating layer 7 is applied to the outer surface of the positive electrode mixture layer 2 as shown in FIG. 4 and dried and then pressed to form a porous insulating layer having a porosity of 47% and a thickness of 3 μm. 7 was formed. Thereafter, the positive electrode plate 3 was produced by slitting to a specified width of the cylindrical lithium ion secondary battery 18.

  On the other hand, 100 parts by weight of artificial graphite as the active material of the negative electrode, and 2.5 parts by weight of styrene-butadiene copolymer rubber particle dispersion (solid content 40% by weight) as the binder with respect to 100 parts by weight of the active material ( 1 part by weight in terms of solid content of the binder), 1 part by weight of carboxymethyl cellulose as a thickener with respect to 100 parts by weight of the active material, and an appropriate amount of water, and agitation in a double-arm kneader. An agent paint was prepared.

Next, as shown in FIG. 1, this negative electrode mixture paint was applied to a negative electrode current collector 4 made of a tough pitch copper foil having a thickness of 10 μm, dried and then pressed to make the thickness of the negative electrode mixture layer 5 on one side of 85 μm. did.

  Further, 100 parts by weight of zinc oxide whisker (Panatetra) manufactured by Matsushita Amtech Co., Ltd. and 100 parts by weight of polyacrylonitrile modified rubber (BM-720H) manufactured by Nippon Zeon Co., Ltd. as binders are used. 4 parts by weight in terms of solid content was mixed with an appropriate amount of N-methyl-2-pyrrolidone with a double-arm kneader to prepare a coating material for the porous insulating layer 7.

  As shown in FIG. 4, the coating material for the porous insulating layer 7 is applied to the outer surface of the negative electrode mixture layer 5 by gravure coating, dried and then pressed to form a porous insulating layer having a porosity of 53% and a thickness of 4 μm. 7 was formed. Thereafter, the negative electrode plate 6 was produced by slitting to a specified width of the cylindrical lithium ion secondary battery 18.

  Using the positive electrode plate 3 and the negative electrode plate 6 manufactured as described above, a polyethylene microporous film having a thickness of 15 μm is wound as a separator 8 in the arrow direction A as shown in FIG. Configured. The electrode group 9 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 14 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12.

Next, the positive electrode lead 15 led out from the upper part of the electrode group 9 is connected to the sealing plate 16, and 1 part of LiPF ₆ and 3 parts by weight of VC are dissolved in a predetermined amount of EC, DMC, and MEC mixed solvent in the battery case 12. A water electrolyte (not shown) was injected. Thereafter, a sealing plate 16 having a sealing gasket 17 attached to the periphery thereof is inserted into the opening of the battery case 12, the opening of the battery case 12 is bent inward, and caulked to seal the cylindrical lithium ion two. The secondary battery 18 was taken as Example 3.

(Comparative Example 1)
Comparative Example 1 will be described with reference to the drawings. First, 100 parts by weight of lithium cobaltate as an active material, 2 parts by weight of acetylene black as a conductive material with respect to 100 parts by weight of the active material, and 2 parts by weight of polyvinylidene fluoride as a binder with respect to 100 parts by weight of the active material Was mixed with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader to prepare a positive electrode mixture paint.

  Next, as shown in FIG. 7, this positive electrode mixture paint was applied to a positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm, dried and then pressed to make the thickness of the positive electrode mixture layer 2 on one side 75 μm. . Then, the positive electrode plate 3 was produced by slitting to a specified width of the cylindrical battery.

  On the other hand, 100 parts by weight of artificial graphite as the active material of the negative electrode, and 2.5 parts by weight of styrene-butadiene copolymer rubber particle dispersion (solid content 40% by weight) as the binder with respect to 100 parts by weight of the active material ( 1 part by weight in terms of solid content of the binder), 1 part by weight of carboxymethyl cellulose as a thickener with respect to 100 parts by weight of the active material, and an appropriate amount of water, and agitation in a double-arm kneader. An agent paint was prepared.

  Next, as shown in FIG. 7, this negative electrode mixture paint was applied to a negative electrode current collector 4 made of a tough pitch copper foil having a thickness of 10 μm, dried and then pressed to make the thickness of the negative electrode mixture layer 5 on one side of 85 μm. did. Then, the negative electrode plate 6 was produced by slitting to a specified width of the cylindrical battery.

Using the positive electrode plate 3 and the negative electrode plate 6 produced as described above, as shown in FIG.
A spiral microelectrode group 9 was formed by winding an m-thick polyethylene microporous film as a separator 8 in the arrow direction A. The electrode group 9 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 14 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12.

Next, the positive electrode lead 15 led out from the upper part of the electrode group 9 is connected to the sealing plate 16, and 1 part of LiPF ₆ and 3 parts by weight of VC are dissolved in a predetermined amount of EC, DMC, and MEC mixed solvent in the battery case 12. A water electrolyte (not shown) was injected. Thereafter, a sealing plate 16 having a sealing gasket 17 attached to the periphery thereof is inserted into the opening of the battery case 12, the opening of the battery case 12 is bent inward, and caulked to seal the cylindrical lithium ion two. The secondary battery 18 was set as Comparative Example 1.

  The lithium ion secondary batteries produced in Examples 1 to 3 and Comparative Example 1 were evaluated with the following contents. In the evaluated lithium-ion secondary battery, in order to further improve the reliability, the internal resistance was tested by applying an applied voltage of 250 V between the positive electrode terminal and the negative electrode terminal for all the secondary batteries after sealing. The secondary battery of 100 MΩ or less was omitted as a poorly insulated battery.

  For the drop test, the secondary battery subjected to the above insulation resistance test was charged for 2 hours under the conditions of an upper limit voltage of 4.2 V and a current of 2 A, and then the secondary battery was placed on the concrete surface from a height of 1.5 m. A drop test was performed 10 times on each of the three surfaces of the battery, and the exothermic temperature of 10 secondary batteries was measured at room temperature (25 ° C.). Indicated. Moreover, the result of having confirmed the presence or absence of an internal short circuit about 1000 lithium ion secondary batteries after a drop test was shown in (Table 1).

  For the round bar crushing test, the lithium ion secondary battery subjected to the above insulation resistance test was charged for 2 hours under the conditions of an upper limit voltage of 4.2 V and a current of 2 A, and then in the longitudinal direction of the lithium ion secondary battery. On the other hand, in the vertical direction, a crush test was carried out with a round bar having a diameter of 10 mm, the heat generation temperature of 10 secondary batteries was measured at room temperature (25 ° C.), and the average value of 10 cells was obtained (Table Shown in 1).

  For the 150 ° C. heating test, the lithium ion secondary battery subjected to the above insulation resistance test was charged for 2 hours under the conditions of an upper limit voltage of 4.2 V and a current of 2 A, and then the lithium ion secondary battery was placed in a thermostatic bath. The temperature of the thermostatic chamber was raised to 150 ° C. under the condition that the temperature was raised by 5 ° C. per minute from room temperature, and the battery heat generation temperature at that time was measured. Shown in 1).

  As shown in Table 1, on the outer surface of the negative electrode mixture layer 5, the outer surface of the positive electrode mixture layer 2, the outer surfaces of the positive electrode mixture layer 2 and the negative electrode mixture layer 5, which were performed in Examples 1 to 3 In the lithium ion secondary battery 18 having the porous insulating layer 7 formed, the outer surfaces of the positive electrode mixture layer 2 and the negative electrode mixture layer 5 are protected by the porous insulating layer 7 even when a physical impact is applied from the outside. Therefore, contact between the positive electrode plate 3 and the negative electrode plate 6 does not occur, so that an internal short circuit does not occur and safety is good.

  On the other hand, the lithium ion secondary battery 18 of Comparative Example 1 in which the porous insulating layer 7 is not formed has a high battery temperature in any of the tests of dropping, round bar crushing, and heating at 150 ° C. It is considered that the contact of the plate 6 has occurred, and it has been found that providing the porous insulating layer 7 so that the positive electrode plate 3 and the negative electrode plate 6 do not contact each other has a great effect of preventing the occurrence of a micro short circuit or an internal short circuit. It was.

  In Examples 1 to 3, the positive electrode plate 3 and the negative electrode plate 6 have different compositions as the coating material for the porous insulating layer 7, and the porosity of the porous insulating layer 7 is different. It is not limited to these, The same effect is acquired by adjusting the thickness and porosity of the porous insulating layer 7 using the same coating material for the porous insulating layers 7 for the positive electrode plate 3 and the negative electrode plate 6. Needless to say.

  The nonaqueous secondary battery according to the present invention has a positive electrode mixture by forming a porous insulating layer containing tetrapotted whiskers on the outer surface of at least one of the positive electrode mixture layer and the negative electrode mixture layer. Since it is possible to provide a non-aqueous secondary battery excellent in safety that can prevent the falling of the layer or the negative electrode mixture layer and suppress internal short circuit even when a physical impact is applied from the outside. It is useful as a portable power source or the like for which a high capacity is desired as electronic devices and communication devices become multifunctional.

Sectional drawing which shows the component of the electrode group before winding in the non-aqueous secondary battery which concerns on one Example of this invention. The model figure which shows the principal part of the porous insulating layer formed in the outer surface of the electrode mixture layer in the electrode plate for non-aqueous secondary batteries which concerns on one Example of this invention. The model figure which showed the state of the interface of the electrode mixture layer and the porous insulating layer 7 in the electrode plate for non-aqueous secondary batteries which concerns on one Example of this invention. Sectional drawing which shows the component of the electrode group before winding in the non-aqueous secondary battery which concerns on another Example of this invention. Sectional drawing which shows the component of the electrode group before winding in the non-aqueous secondary battery which concerns on another Example of this invention. 1 is a partially cutaway perspective view of a cylindrical secondary battery according to an embodiment of the present invention. Sectional drawing which shows the component of the electrode group before winding in the non-aqueous secondary battery which concerns on the comparative example of this invention Cross-sectional view of a non-aqueous secondary battery in a conventional example Cross-sectional view of a non-aqueous secondary battery in a conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode mixture layer 3 Positive electrode plate 4 Negative electrode collector 5 Negative electrode mixture layer 6 Negative electrode plate 7 Porous insulating layer 8 Separator 9 Electrode group 10 Tetrapot-shaped whisker 10a Core part 10b Fibrous part 11 Binder 12 Battery case 13 Insulating plate 14 Negative electrode lead 15 Positive electrode lead 16 Sealing plate 17 Sealing gasket 18 Non-aqueous secondary battery A Winding direction of electrode group

Claims (9)

  A positive electrode plate in which a positive electrode mixture layer is formed by adhering a positive electrode mixture coating material obtained by kneading and dispersing an active material composed of at least a lithium-containing composite oxide, a conductive material, and a binder in a dispersion medium onto a positive electrode current collector, or A non-electrode plate comprising a negative electrode mixture layer formed by adhering a negative electrode mixture coating material obtained by kneading and dispersing an active material and a binder made of a material capable of holding lithium at least on a negative electrode current collector. An electrode plate for an aqueous secondary battery, characterized in that a porous insulating layer containing tetrapotted whiskers is formed on the outer surface of at least one of the positive electrode mixture layer and the negative electrode mixture layer. An electrode plate for a non-aqueous secondary battery.   2. The electrode plate for a non-aqueous secondary battery according to claim 1, wherein a tip portion of the tetrapot-shaped whisker is bitten into an outer surface of the positive electrode mixture layer or the negative electrode mixture layer.   2. The electrode plate for a non-aqueous secondary battery according to claim 1, wherein the porous insulating layer is configured to be thinner than a separator interposed between the electrode plates.   2. The electrode plate for a non-aqueous secondary battery according to claim 1, wherein the porosity of the porous insulating layer is 30% or more and 70% or less.   2. The electrode plate for a non-aqueous secondary battery according to claim 1, wherein the amount of whisker contained in the porous insulating layer is 50 wt% or more and 97 wt% or less.   The whisker is composed of a core part and a fibrous part extending from the core part in different four-axis directions, and the fibrous part has a length of 0.1 to 10 μm and an aspect ratio of 3 to 70. The electrode plate for non-aqueous secondary batteries according to claim 1.   The electrode plate for a non-aqueous secondary battery according to claim 1, wherein the whisker is composed of zinc oxide whisker. The electrode plate for a non-aqueous secondary battery according to claim 1, wherein the zinc oxide whisker has a specific resistance of 10 ⁸ to 10 ¹² Ω · cm.   A positive electrode plate having a positive electrode mixture layer formed by adhering a positive electrode mixture paint obtained by kneading and dispersing an active material comprising at least a lithium-containing composite oxide, a conductive material, and a binder in a dispersion medium onto a positive electrode current collector; Between a negative electrode plate in which a negative electrode mixture layer is formed by adhering a negative electrode mixture paint obtained by kneading and dispersing an active material and a binder made of a material capable of holding lithium at least on a negative electrode current collector A non-aqueous secondary battery in which a separator is interposed and wound or laminated in a battery case together with a non-aqueous electrolyte solution, and is attached to at least one of the positive electrode plate and the negative electrode plate A non-aqueous secondary battery using the electrode plate for a non-aqueous secondary battery according to claim 1.

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