JP2014041698A - Positive electrode plate for nonaqueous secondary battery, and nonaqueous secondary batter using the same - Google Patents

Abstract

In order to realize a battery having a high potential and a high discharge capacity by controlling the arrangement of a conductive material of a positive electrode mixture layer formed on a positive electrode current collector, additives such as a conductive material and a binder are limited. It is an object of the present invention to suppress an increase in sheet resistance even when reduced to a low level and to reduce short-circuit defects that occur in a mode in which the positive electrode mixture layer and the negative electrode mixture layer are in direct contact due to defects or the like.
A positive electrode mixture layer is formed by applying a positive electrode mixture paint obtained by kneading and dispersing a positive electrode active material, a conductive material, and a binder in a dispersion medium onto a positive electrode current collector. A positive electrode plate for a non-aqueous secondary battery, wherein a plurality of conductive materials 3a that are in conductive contact with a connection point between the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of connection points between the positive electrode active materials 2 are connected to each other. The conductive material 3b is in conductive contact, and the number of conductive materials 3a between the positive electrode active material 2 and the positive electrode current collector 1 is further reduced.
[Selection] Figure 1

Description

  The present invention relates to a non-aqueous secondary battery represented by a lithium ion battery, and more particularly to a positive electrode plate for a non-aqueous secondary battery and a non-aqueous secondary battery using the same.

In recent years, lithium ion secondary batteries as non-aqueous secondary batteries, which are widely used as power sources for portable electronic devices, use a carbonaceous material that can occlude and release lithium as a negative electrode, LiCoO _{2 as} a positive electrode, etc. Thus, a lithium-ion secondary battery having a high potential and a high discharge capacity is realized.

  This non-aqueous secondary battery generally has a negative electrode plate in which the above negative electrode material is held by a negative electrode current collector as a support, and reversibly electrochemically reacts with lithium ions like a lithium cobalt composite oxide. The positive electrode active material that performs the reaction holds the positive electrode plate held by the positive electrode current collector as the support and the non-aqueous electrolyte, and is interposed between the negative electrode plate and the positive electrode plate, It consists of the porous insulator which prevents that a short circuit arises between.

  Further, the positive electrode plate and the negative electrode plate formed in a sheet shape or a foil shape are spirally wound via a porous insulator to form an electrode group as a power generation element. Further, the power generation element is housed in a battery case made of metal such as stainless steel, nickel-plated iron, or aluminum. And after pouring nonaqueous electrolyte in a battery case, a cover plate is sealed and fixed to the opening edge part of a battery case, and a nonaqueous secondary battery is comprised.

  By the way, since non-aqueous secondary batteries need to be repeatedly charged and discharged over a long period of time, the deterioration of the charge / discharge cycle characteristics of the battery (which indicates the battery capacity change characteristics due to repeated charge / discharge) can be suppressed to a minimum and the battery life can be reduced. It is an important issue to make it possible to prolong life.

  The charge / discharge cycle characteristics of the non-aqueous secondary battery are largely governed by the configuration of the power generation element, and are particularly greatly affected by the positive electrode mixture layer and the negative electrode mixture layer whose electron conductivity is small compared to other members.

  Therefore, how to form the positive electrode mixture layer and the negative electrode mixture layer applied to the positive electrode current collector and the negative electrode current collector with low resistance and suppressing variation in resistance is the key to realizing a high sustainability battery.

  However, when the positive electrode plate in which the positive electrode mixture layer is formed on the positive electrode current collector and the negative electrode plate in which the negative electrode mixture layer is formed on the negative electrode current collector have low resistance, the positive electrode mixture layer and the negative electrode mixture layer It is known that a short-circuit current is likely to flow in a mode in which the battery is in direct contact, and the battery becomes hot due to Joule heat generation, resulting in an unsafe state.

  Therefore, providing a lithium ion secondary battery with excellent output characteristics with low internal resistance by keeping the volume resistance of the positive electrode mixture layer below 500 Ω · cm, and so that the internal resistance does not vary from battery to battery. A manufacturing method for managing the electrode plate manufacturing process has been proposed (see, for example, Patent Document 1).

  Moreover, the safety which is excellent also in the short circuit prevention performance by keeping the volume resistance of the mixture of the positive electrode active material, the conductive material and the binder forming the positive electrode mixture layer in the range of 0.1 to 1.0 Ω · cm. A high-capacity lithium-ion secondary battery has been proposed (see, for example, Patent Document 2).

JP 2004-214212 A JP 2006-324118 A

  However, in order to realize a battery with a high potential and a high discharge capacity, it is necessary to increase the active material density of the electrode plate, and for that purpose, it is necessary to reduce additives such as a conductive material and a binder to the limit. . However, it has been found that simply reducing the addition amount of the conductive material and the binder deteriorates the degree of dispersion of the paint, and increases the volume resistance of the mixture layer formed on the current collector. In addition, since segregation of the binder is likely to occur, the adhesion between the current collector and the electrode mixture layer also decreases, and the area resistance including the interface resistance between the current collector and the electrode mixture layer also increases.

  In particular, when the present inventors investigated the causal relationship between the state of the positive electrode mixture layer applied to the positive electrode current collector and the battery characteristics, the volume resistance of the positive electrode mixture layer alone can improve the charge / discharge cycle characteristics. It was found that charge / discharge cycle characteristics cannot be improved unless the sheet resistance is reduced.

  For this reason, in the prior art shown in Patent Documents 1 and 2 described above, only the volume resistance of the positive electrode mixture layer of the positive electrode plate is mentioned, which is insufficient to improve the charge / discharge cycle characteristics. In addition, in the range of 0.1 to 1.0 Ω · cm, which is the specified volume resistance range of only the positive electrode mixture layer disclosed in Patent Document 2, the positive electrode mixture layer and the negative electrode mixture layer are in direct contact due to defects or the like. In this mode, it is insufficient to suppress the short-circuit current, and it has been found that the battery becomes high temperature due to Joule heat generation and becomes unsafe.

  The present invention has been made in view of the above-described conventional problems, and realizes a battery having a high potential and a high discharge capacity by controlling the arrangement of the conductive material of the positive electrode mixture layer formed on the positive electrode current collector. Therefore, even if the additives such as the conductive material and the binder are reduced to the utmost limit, the increase in sheet resistance is suppressed, and the short-circuit failure occurs in the mode in which the positive electrode mixture layer and the negative electrode mixture layer are in direct contact due to a defect or the like. The purpose is to reduce.

  In order to solve the above-described conventional problems, the positive electrode plate for a non-aqueous secondary battery according to the present invention uses a positive electrode mixture paint obtained by kneading and dispersing a positive electrode active material, a conductive material, and a binder in a dispersion medium. A positive electrode plate for a non-aqueous secondary battery that is coated on top of each other to form a positive electrode mixture layer, and a plurality of mutual conduction is established between a connection point between the positive electrode active material and the positive electrode current collector and a connection point between the positive electrode active materials. Increased sheet resistance even if the additive such as conductive material and binder is reduced to the limit by arranging the conductive material in contact and arranging few conductive materials between the positive electrode active material and the positive electrode current collector. And short circuit failure occurring in a mode in which the positive electrode mixture layer and the negative electrode mixture layer are in direct contact with each other due to defects or the like can be reduced.

  According to the present invention, a non-aqueous two-layer coating in which a positive electrode mixture layer is formed by applying a positive electrode mixture paint obtained by kneading and dispersing a positive electrode active material, a conductive material, and a binder with a dispersion medium onto a positive electrode current collector. A positive electrode plate for a secondary battery, comprising a plurality of conductive materials in conductive contact with each other at a connection point between a positive electrode active material and a positive electrode current collector and at a connection point between the positive electrode active materials, and the positive electrode active material and the positive electrode current collector. By disposing a small amount of conductive material between the electric bodies, it is possible to provide a positive electrode plate for a non-aqueous secondary battery that can have high discharge capacity, high charge / discharge cycle characteristics, and high safety at a high potential.

The principal part expanded sectional view which shows the positive electrode plate for non-aqueous secondary batteries of Example 1 and 2 of this invention The principal part expanded sectional view which shows the positive electrode plate for non-aqueous secondary batteries of Example 3 of this invention. The principal part expanded sectional view which shows the positive electrode plate for non-aqueous secondary batteries of Example 4 of this invention The principal part expanded sectional view which shows the positive electrode plate for non-aqueous secondary batteries of the comparative example 1 of this invention. The principal part expanded sectional view which shows the positive electrode plate for non-aqueous secondary batteries of the comparative example 2 of this invention. The partially cutaway perspective view showing the configuration of the nonaqueous secondary battery of the present invention Schematic diagram illustrating a method for measuring sheet resistance according to the present invention. (A) Perspective view of nickel plate used for foreign matter mixing test according to the present invention, (b) Perspective view explaining processing of nickel plate used for foreign matter mixing test according to the present invention.

  In the first aspect of the present invention, a positive electrode mixture layer is formed by applying a positive electrode mixture paint obtained by kneading and dispersing a positive electrode active material, a conductive material and a binder in a dispersion medium onto a positive electrode current collector. A positive electrode plate for a non-aqueous secondary battery comprising a plurality of conductive materials in electrical contact with a connection point between a positive electrode active material and a positive electrode current collector and a connection point between positive electrode active materials, and a positive electrode active material By arranging a small amount of conductive material between the positive electrode current collector and the positive electrode current collector, even if the additives such as the conductive material and the binder are reduced to the utmost limit, the increase in sheet resistance is suppressed, and the positive electrode mixture layer due to defects etc. Positive electrode plate for non-aqueous secondary batteries that can reduce short-circuit failure that occurs in the mode in which the negative electrode mixture layer and the negative electrode mixture layer are in direct contact, and can have high discharge capacity, high charge / discharge cycle characteristics and high safety at a high potential Can be provided.

In the second invention of the present invention, the area resistance of the positive electrode plate for a non-aqueous secondary battery according to the first invention is set to 0.20 to 1.50 Ω · cm ² , thereby further increasing the potential at a higher potential. The discharge capacity can be combined with high charge / discharge cycle characteristics and high safety.

  In the third aspect of the present invention, a positive electrode mixture paint obtained by kneading and dispersing at least a positive electrode active material comprising a lithium-containing composite oxide, a conductive material, and a binder with a dispersion medium is applied onto the positive electrode current collector. A negative electrode mixture coating material in which a positive electrode plate having a positive electrode mixture layer formed thereon, a negative electrode active material made of a material capable of holding at least lithium, and a binder are kneaded and dispersed in a dispersion medium is coated on the negative electrode current collector. A non-aqueous secondary in which a porous insulator is interposed between a negative electrode plate formed with a negative electrode mixture layer and wound or laminated in a spiral shape with a non-aqueous electrolyte enclosed in a battery case A positive electrode plate for a non-aqueous secondary battery according to any one of the first to second inventions is used as a positive electrode plate, so that a high potential, high discharge capacity, high charge / discharge cycle characteristics, and It is possible to provide a non-aqueous secondary battery that can have high safety.

  Hereinafter, an embodiment of the present invention will be described by taking a cylindrical lithium ion secondary battery as an example with reference to the drawings. However, the present invention is not limited to this, and may be a square battery or a coin-type battery. It doesn't matter.

  FIG. 6 is a partially cutaway perspective view showing the configuration of the non-aqueous secondary battery according to the embodiment of the present invention.

  As the nonaqueous secondary battery of the present invention, for example, as shown in FIG. 6, a positive electrode plate 6 using a composite lithium oxide as a positive electrode active material and a negative electrode plate 7 using a material capable of holding lithium as a negative electrode active material. An electrode group 11 is formed by spirally winding the separator 8 as a porous insulator. The electrode group 11 is accommodated in the bottomed cylindrical battery case 12 together with the insulating plate 13, the negative electrode lead 9 led out from the lower part of the electrode group 11 is connected to the bottom part of the battery case 12, and then the upper part of the electrode group 11 The positive electrode lead 10 led out is connected to the sealing plate 14, and a non-aqueous electrolyte solution (not shown) made of a non-aqueous solvent is poured into the battery case 12, and then a sealing gasket is formed in the opening of the battery case 12. A sealing plate 14 with 15 attached to the periphery can be inserted, and the opening of the battery case 12 can be bent inward and caulked and sealed.

  Below, the structure of the positive electrode plate 6 which comprises the non-aqueous secondary battery concerning one embodiment of this invention is demonstrated, referring FIG. FIG. 1 is an enlarged cross-sectional view of a main part showing the vicinity of a positive electrode current collector 1 of a positive electrode plate 6 according to an embodiment of the present invention.

  First, the configuration of the desirable positive electrode plate 6 of the present invention is not particularly limited, but a metal foil made of aluminum, aluminum alloy, nickel or nickel alloy having a thickness of 5 μm to 30 μm can be used as the positive electrode current collector 1. As the positive electrode mixture paint applied on the positive electrode current collector 1, the positive electrode active material 2, the conductive material 3, and the binder 4 are mixed and dispersed in a dispersion medium by a dispersing machine such as a planetary mixer. An agent paint is produced.

  First, the positive electrode active material 2, the conductive material 3, and the binder 4 are put in an appropriate dispersion medium, and mixed and dispersed by a dispersing machine such as a planetary mixer to obtain an optimum viscosity for application to the positive electrode current collector 1. A positive electrode mixture paint can be produced by adjusting and kneading.

  Examples of the positive electrode active material 2 include lithium cobaltate and modified products thereof (such as lithium cobaltate in which aluminum or magnesium is dissolved), lithium nickelate and modified products thereof (partly nickel-substituted cobalt, etc.) ), And complex oxides such as lithium manganate and modified products thereof.

  As the conductive material 3 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 4 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. In this case, an acrylate monomer or an acrylate oligomer into which a reactive functional group is introduced may be mixed in the binder.

  Further, the positive electrode mixture paint prepared as described above using a die coater is applied onto the positive electrode current collector 1 made of aluminum foil, dried, and then compressed to a predetermined thickness by a press. A positive electrode plate 6 on which the agent layer 5 is formed is obtained.

  Here, a configuration having a plurality of conductive materials 3a in conductive contact with each other at a connection point between the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of conductive materials 3b in conductive contact with each other at a connection point between the positive electrode active materials 2 And the number of conductive materials 3a disposed at the connection point between the positive electrode active material 2 and the positive electrode current collector 1 is smaller than the number of conductive materials 3b disposed at the connection point between the positive electrode active materials 2. By being formed on the electric body 1, it is possible to combine a high discharge capacity, a high charge / discharge cycle characteristic, and a high safety at a high potential.

  On the other hand, although it does not specifically limit about the negative electrode plate 7, The metal foil made from copper or a copper alloy which has thickness of 5 micrometers-25 micrometers can be used as a negative electrode collector. As the negative electrode mixture paint applied on the negative electrode current collector, the negative electrode active material, the binder, and if necessary, the conductive material and the thickener are mixed and dispersed in a dispersion medium such as a planetary mixer. Thus, a negative electrode mixture paint is produced.

  First, the negative electrode active material and the binder are placed in an appropriate dispersion medium, mixed and dispersed by a dispersing machine such as a planetary mixer, and adjusted to the optimum viscosity for application to the current collector and then kneaded. A negative electrode mixture paint can be produced.

  As the negative electrode active material, various natural graphites and artificial graphites, silicon-based composite materials such as silicide, and various alloy composition materials can be used.

  Various binders such as PVDF and modified products thereof can be used as the negative electrode binder at this time. From the viewpoint of improving lithium ion acceptability, styrene-butadiene copolymer rubber particles (SBR) and the binders thereof are used. It can be said that it is more preferable to use a cellulose resin such as carboxymethyl cellulose (CMC) in combination with the modified body or to add a small amount.

  Further, the negative electrode mixture paint prepared as described above using a die coater is applied onto a negative electrode current collector made of copper foil, dried, and then compressed to a predetermined thickness with a press to form the negative electrode plate 7. Is obtained.

For the non-aqueous electrolyte, various lithium compounds such as LiPF ₆ and LIBF ₄ can be used as the 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. It is also preferable to use vinylene carbonate (VC), cyclohexylbenzene (CHB), and modified products thereof in order to form a good film on the positive and negative electrodes and to ensure stability during overcharge.

  The separator 8 is not particularly limited as long as it has a composition that can withstand the range of use of the lithium ion secondary battery, but it is common to use a microporous film of an olefin-based resin such as polyethylene or polypropylene as a single or a composite. And preferred as an embodiment. Although the thickness of this separator 8 is not specifically limited, What is necessary is just to be 10-25 micrometers.

  FIG. 2 is an enlarged cross-sectional view of the main part showing the vicinity of the positive electrode current collector 1 of the positive electrode plate according to another embodiment of the present invention.

  FIG. 2 shows a plurality of conductive materials 3 a that are in conductive contact with each other at the connection point between the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of conductive materials 3 b that are in conductive contact with each other at a connection point between the positive electrode active materials 2. In the structure, the positive electrode current collector 1 is formed so that the number of conductive materials 3a is extremely smaller than the number of conductive materials 3b.

  FIG. 3 is an enlarged cross-sectional view of the main part showing the vicinity of the positive electrode current collector 1 of the positive electrode plate according to another embodiment of the present invention.

  FIG. 3 shows that the positive electrode active material 2 having two different particle diameters is used, so that the positive electrode active material 2 in contact with the positive electrode current collector 1 has a small amount of conductive material 3 present at the connection point due to the difference in surface area. By forming the mixture layer 5, a plurality of conductive materials 3a that are in conductive contact with each other at the connection point between the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of connection points between the positive electrode active material 2 are in conductive contact with each other. A structure having a conductive material 3b and formed in the positive electrode current collector 1 so that the number of conductive materials 3a is extremely smaller than the number of conductive materials 3b is shown.

  FIG. 4 is an enlarged cross-sectional view of the main part showing the vicinity of the positive electrode current collector 1 of the positive electrode plate prepared for the purpose of comparison with the present invention.

  FIG. 4 shows that the conductive material 3 cannot be aggregated or conductively contacted by using the positive electrode mixture paint in which the addition amount of the conductive material 3 and the binder 4 is reduced without taking measures for improving dispersibility. The conductive material 3 has a large amount.

  FIG. 5 is an enlarged cross-sectional view of the main part showing the vicinity of the positive electrode current collector 1 of the positive electrode plate prepared for the purpose of comparison with the present invention.

  FIG. 5 shows that the positive electrode material mixture paint in which the addition amount of the conductive material 3 and the binder 4 is increased without taking a measure for improving dispersibility, and the conductive material 3 cannot be aggregated or conductively contacted. It has a configuration in which there are many single conductive materials 3. Moreover, since there are many conductive materials 3 and binders 4, the space | interval of the positive electrode active materials 2 is wide, and the active material density cannot be raised.

  FIG. 7 shows a schematic diagram of an apparatus for measuring the sheet resistance of the positive electrode plate 6.

  Here, 16 in FIG. 7 is a pressing device, 17 and 18 are positive plates, 19 and 20 are 2 mm thick Cu plates, and 21 is a resistance measuring device.

  Lead wires 17 b and 18 b are connected to the positive electrode current collectors 17 a and 18 a of the positive electrode plates 17 and 18, and the lead wires 17 b and 19 b are connected to terminals 21 b and 21 c of the resistance measuring device 21. Further, lead wires 19b and 20b are connected to the Cu plates 19 and 20 sandwiching the positive electrode plates 17 and 18, and the lead wires 19b and 20b are connected to terminals 21a and 21d of the resistance measuring device 21, respectively. ing.

As the positive electrode plates 17 and 18 measured at this time, a positive electrode plate taken out from a battery charged in advance is cut out to a predetermined size, for example, 20 × 20 mm. Then, the sheet resistance when the positive plates 17 and 18 are pressed at 50 kg / cm ² by the pressing device 16 is measured by the direct current four-terminal method using the resistance measuring device 21.

  FIG. 8 is a perspective view for explaining a nickel plate used for a foreign matter mixing test of a non-aqueous secondary battery.

  Here, the nickel plate of FIG. 8B shows a shape obtained by processing the nickel plate of FIG. 8A so that the cross-sectional shape is an L shape.

  Hereinafter, specific examples will be described in more detail.

  An embodiment of the present invention will be described with reference to the drawings. First, acetylene black as a conductive material 3 and an appropriate amount of N-methyl-2-pyrrolidone and polyvinyl pyrrolidone as a dispersant were both stirred and kneaded in a double-arm kneader to prepare a conductive material paste. Next, as the positive electrode active material 2, a conductive material paste and binder 4 in an amount of 1 part by weight with respect to 100 parts by weight of lithium nickelate having a particle size of 10 μm and 100 parts by weight of acetylene black as the positive electrode active material 2. As a positive electrode mixture paint, polyvinylidene fluoride is stirred and kneaded in a double-arm kneader with 1 part by weight of 100 parts by weight of the positive electrode active material 2 together with an appropriate amount of N-methyl-2-pyrrolidone. Was made.

  Next, the above positive electrode mixture paint is intermittently applied to the positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm, dried on both sides, and then pressed to form a positive electrode plate 6 having a mixture thickness of 70 μm on one side. Was made. Then, the positive electrode plate 6 was produced by slitting to the width | variety prescribed | regulated of the cylindrical lithium ion secondary battery.

Further, a positive electrode lead 10 was connected to a portion of the positive electrode plate 6 where the positive electrode current collector 1 was exposed, and a positive electrode protective tape was applied so as to cover the positive electrode lead 10 to constitute the positive electrode plate 6.
As shown in FIG. 1, the positive electrode plate 6 has a plurality of conductive materials 3 a electrically connected to the connection points of the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of connection points to the connection points of the positive electrode active materials 2. It was possible to form the positive electrode current collector 1 so that the number of the conductive materials 3a was smaller than the number of the conductive materials 3b.

  On the other hand, 100 parts by weight of artificial graphite as the negative electrode active material, 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 negative electrode 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 negative electrode active material, and an appropriate amount of water, and agitation in a double arm kneader. A mixture paint was prepared.

  Next, the above negative electrode mixture paint is intermittently applied to a negative electrode current collector made of a copper foil having a thickness of 10 μm, dried on both sides, and then pressed to form a negative electrode plate 7 having a mixture thickness of 80 μm on one side. Was made. Thereafter, the negative electrode plate 7 was produced by slitting to a specified width of the cylindrical lithium ion secondary battery.

  Further, a negative electrode lead 9 was connected to a portion of the negative electrode plate 7 where the negative electrode current collector was exposed, and a negative electrode protective tape was applied so as to cover the negative electrode lead 9 to constitute the negative electrode plate 7.

Using the positive electrode plate 6 and the negative electrode plate 7 produced as described above, a 20 μm-thick polyethylene microporous film was wound as a separator 8 as shown in FIG. 6 to form a spiral electrode group 11. The electrode group 11 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 9 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12. Subsequently, the positive electrode lead 10 led out from the upper part of the electrode group 9 is connected to the sealing plate 14, 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 14 having a sealing gasket 15 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 and sealed. The secondary battery was designated as Example 1.

  An embodiment of the present invention will be described with reference to the drawings. First, 100 parts by weight of lithium nickelate having a particle size of 10 μm as the positive electrode active material 2 and 1 part by weight of acetylene black as the conductive agent 3 are coated beforehand in 100 parts by weight of the positive electrode active material 2. went. Next, a positive electrode active material 2 of lithium nickelate coated with acetylene black and polyvinylidene fluoride as the binder 4 are added in an appropriate amount of N-methyl-2 with 1 part by weight per 100 parts by weight of the positive electrode active material 2. -A positive electrode mixture paint was prepared by stirring and kneading with a pyrrolidone in a double-arm kneader.

  Next, the above positive electrode mixture paint is intermittently applied to the positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm, dried on both sides, and then pressed to form a positive electrode plate 6 having a mixture thickness of 70 μm on one side. Was made. Then, the positive electrode plate 6 was produced by slitting to the width | variety prescribed | regulated of the cylindrical lithium ion secondary battery. As shown in FIG. 1, the positive electrode plate 6 has a plurality of conductive materials 3 a electrically connected to the connection points of the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of connection points to the connection points of the positive electrode active materials 2. It was possible to form the positive electrode current collector 1 so that the number of the conductive materials 3a was smaller than the number of the conductive materials 3b.

  Further, a positive electrode lead 10 was connected to a portion of the positive electrode plate 6 where the positive electrode current collector 1 was exposed, and a positive electrode protective tape was applied so as to cover the positive electrode lead 10 to constitute the positive electrode plate 6.

  The negative electrode plate 7 was prepared in the same manner as in Example 1.

Using the positive electrode plate 6 and the negative electrode plate 7 produced as described above, a 20 μm-thick polyethylene microporous film was wound as a separator 8 as shown in FIG. 6 to form a spiral electrode group 11. The electrode group 11 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 9 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12. Subsequently, the positive electrode lead 10 led out from the upper part of the electrode group 9 is connected to the sealing plate 14, 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 14 having a sealing gasket 15 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 and sealed. The secondary battery was designated as Example 2.

  An embodiment of the present invention will be described with reference to the drawings. First, acetylene black as a conductive material 3 and an appropriate amount of N-methyl-2-pyrrolidone and polyvinyl pyrrolidone as a dispersant were both stirred and kneaded in a double-arm kneader to prepare a conductive material paste. Next, as the positive electrode active material 2, 100 parts by weight of lithium nickelate having a particle size of 10 μm and acetylene black, a conductive material paste in an amount of 0.4 parts by weight with respect to 100 parts by weight of the positive electrode active material 2, The material 4 was prepared by mixing polyvinylidene fluoride as a material 4 and 1 part by weight of the positive electrode active material 2 with 100 parts by weight of an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader. A positive electrode mixture paint was prepared.

  Further, 100 parts by weight of lithium nickelate as the positive electrode active material 2, 100 parts by weight of the conductive material paste with respect to 100 parts by weight of the positive electrode active material 2 as acetylene black, and polyvinylidene fluoride as the binder 4 as the positive electrode A second positive electrode mixture paint was prepared by stirring and kneading 1 part by weight with 100 parts by weight of the active material together with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader.

  Next, the first positive electrode mixture paint described above was applied on both sides of the positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm so that the thickness after pressing intermittently became 10 μm. Then, the above-described second positive electrode mixture paint was applied to a predetermined thickness on the second electrode, dried on both sides, and then pressed to produce a positive electrode plate 6 having a mixture thickness of 70 μm on one side. The drying condition of the first positive electrode mixture paint is carried out at a temperature higher than the drying condition of the second positive electrode mixture paint applied thereon, so that the positive electrode mixture layer 5 is dried as shown in FIG. The number of the conductive materials 3a that are in conductive contact with each other at the connection point between the positive electrode active material 2 and the positive electrode current collector 1 by positively segregating the conductive material and the binder on the surface is determined between the positive electrode active materials 2. The number of the conductive materials 3b that are in conductive contact with each other at the connection point can be extremely small. Then, the positive electrode plate 6 was produced by slitting to the width | variety prescribed | regulated of the cylindrical lithium ion secondary battery.

  Further, a positive electrode lead 10 was connected to a portion of the positive electrode plate 6 where the positive electrode current collector 1 was exposed, and a positive electrode protective tape was applied so as to cover the positive electrode lead 10 to constitute the positive electrode plate 6.

  The negative electrode plate 7 was prepared in the same manner as in Example 1.

Using the positive electrode plate 6 and the negative electrode plate 7 produced as described above, a 20 μm-thick polyethylene microporous film was wound as a separator 8 as shown in FIG. 6 to form a spiral electrode group 11. The electrode group 11 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 9 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12. Subsequently, the positive electrode lead 10 led out from the upper part of the electrode group 9 is connected to the sealing plate 14, 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 14 having a sealing gasket 15 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 and sealed. The next battery was designated as Example 3.

  An embodiment of the present invention will be described with reference to the drawings. First, acetylene black as a conductive material 3 and an appropriate amount of N-methyl-2-pyrrolidone and polyvinylpyrrolidone as a dispersant are both stirred and kneaded in a double-arm kneader to prepare a conductive material paste. Next, as the positive electrode active material 2, a conductive material paste in an amount of 0.4 parts by weight with respect to 100 parts by weight of lithium nickelate having a particle diameter of 20 μm and 100 parts by weight of acetylene black, and binding The material 4 was prepared by mixing polyvinylidene fluoride as a material 4 and 1 part by weight of the positive electrode active material 2 with 100 parts by weight of an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader. A positive electrode mixture paint was prepared.

  Further, as the positive electrode active material 2, a conductive material paste and binder 4 having an amount of 100 parts by weight of lithium nickelate having a particle size of 10 μm and 1 part by weight of acetylene black with respect to 100 parts by weight of the positive electrode active material 2. By stirring and kneading polyvinylidene fluoride in an amount of 1 part by weight with respect to 100 parts by weight of the positive electrode active material 2 together with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader. An agent paint was prepared.

  Next, the above-mentioned first positive electrode mixture paint was applied to both sides of the positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm so that the thickness after pressing intermittently became 20 μm. Then, the above-described second positive electrode mixture paint was applied to a predetermined thickness on the second electrode, dried on both sides, and then pressed to produce a positive electrode plate 6 having a mixture thickness of 70 μm on one side. Then, the positive electrode plate 6 was produced by slitting to the width | variety prescribed | regulated of the cylindrical lithium ion secondary battery. As shown in FIG. 3, the positive electrode plate 6 has a large particle size of the positive electrode active material 2 in contact with the positive electrode current collector 1, so that an area in contact with the positive electrode plate 6 is reduced. As a result, the positive electrode active material 2 and the positive electrode current collector 1 The number of the conductive materials 3a that are in conductive contact with each other at the connection point can be arranged to be extremely smaller than the number of the conductive materials 3b that are in conductive contact with each other at the connection point between the positive electrode active materials 2.

  Further, a positive electrode lead 10 was connected to a portion of the positive electrode plate 6 where the positive electrode current collector 1 was exposed, and a positive electrode protective tape was applied so as to cover the positive electrode lead 10 to constitute the positive electrode plate 6.

  The negative electrode plate 7 was prepared in the same manner as in Example 1.

Using the positive electrode plate 6 and the negative electrode plate 7 produced as described above, a 20 μm-thick polyethylene microporous film was wound as a separator 8 as shown in FIG. 6 to form a spiral electrode group 11. The electrode group 11 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 9 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12. Subsequently, the positive electrode lead 10 led out from the upper part of the electrode group 9 is connected to the sealing plate 14, 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 14 having a sealing gasket 15 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 and sealed. A secondary battery was referred to as Example 4.

(Comparative Example 1)
Next, a comparative example will be described with reference to the drawings. First, 100 parts by weight of lithium nickelate having a particle size of 10 μm as the positive electrode active material 2, acetylene black as the conductive agent 3, 1 part by weight with respect to 100 parts by weight of the positive electrode active material 2, and polyvinylidene fluoride as the binder 4 The positive electrode active material 2 was stirred and kneaded in an amount of 1 part by weight with 100 parts by weight of N-methyl-2-pyrrolidone in a double-arm kneader to prepare a positive electrode mixture paint.

  Then, the positive electrode mixture 6 is applied to the positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm intermittently, dried on both sides, and then pressed to form a positive electrode plate 6 having a mixture thickness of 70 μm on one side. Was made. Then, the positive electrode plate 6 was produced by slitting to the width | variety prescribed | regulated of the cylindrical lithium ion secondary battery.

  Further, a positive electrode lead 10 was connected to a portion of the positive electrode plate 6 where the positive electrode current collector 1 was exposed, and a positive electrode protective tape was applied so as to cover the positive electrode lead 10 to constitute the positive electrode plate 6. As shown in FIG. 4, the positive electrode plate 6 has no means for improving the dispersibility of the conductive material, so that the dispersion state of the positive electrode mixture paint is poor, and there is no single conductive material that is not capable of coagulation or conductive contact of the conductive material. Since there are many, the structure which has the some electrically conductive material 3a which carries out the mutually conductive contact in the connection point of the positive electrode active material 2 and the positive electrode collector 1, and the several electrically conductive material 3b which carries out the mutually conductive contact in the connection point of the positive electrode active material 2 In addition, the positive electrode current collector 1 cannot be formed so that the number of the conductive materials 3a is smaller than the number of the conductive materials 3b.

  The negative electrode plate 7 was prepared in the same manner as in Example 1.

Using the positive electrode plate 6 and the negative electrode plate 7 produced as described above, a 20 μm-thick polyethylene microporous film was wound as a separator 8 as shown in FIG. 6 to form a spiral electrode group 11. The electrode group 11 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 9 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12. Subsequently, the positive electrode lead 10 led out from the upper part of the electrode group 9 is connected to the sealing plate 14, 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 14 having a sealing gasket 15 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 and sealed. The secondary battery was designated as Comparative Example 1.

(Comparative Example 2)
Next, a comparative example will be described with reference to the drawings. First, 100 parts by weight of lithium nickelate having a particle diameter of 10 μm as the positive electrode active material 2, 3 parts by weight of acetylene black as the conductive agent 3 with respect to 100 parts by weight of the positive electrode active material 2, and polyvinylidene fluoride as the binder 4 Was mixed with 3 parts by weight of 100 parts by weight of the positive electrode active material 2 together with an appropriate amount of N-methyl-2-pyrrolidone in a double-arm kneader to prepare a positive electrode mixture paint.

  Then, the positive electrode mixture 6 is applied to the positive electrode current collector 1 made of an aluminum foil having a thickness of 15 μm intermittently, dried on both sides, and then pressed to form a positive electrode plate 6 having a mixture thickness of 70 μm on one side. Was made. Then, the positive electrode plate 6 was produced by slitting to the width | variety prescribed | regulated of the cylindrical lithium ion secondary battery.

  Further, a positive electrode lead 10 was connected to a portion of the positive electrode plate 6 where the positive electrode current collector 1 was exposed, and a positive electrode protective tape was applied so as to cover the positive electrode lead 10 to constitute the positive electrode plate 6. As shown in FIG. 5, since the positive electrode plate 6 does not perform the pre-dispersion of the conductive material, the dispersion state of the positive electrode mixture paint is bad, and there are many single conductive materials that are not able to agglomerate or contact the conductive material. A configuration having a plurality of conductive materials 3a that are in conductive contact with each other at a connection point between the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of conductive materials 3b that are in conductive contact with each other at a connection point between the positive electrode active materials 2; The positive electrode current collector 1 cannot be formed so that the number of the conductive materials 3a is smaller than the number of the conductive materials 3b. Moreover, since there are many conductive materials and binders, the space | interval of positive electrode active materials was wide, and the active material density was not able to be raised.

  The negative electrode plate 7 was prepared in the same manner as in Example 1.

Using the positive electrode plate 6 and the negative electrode plate 7 produced as described above, a 20 μm-thick polyethylene microporous film was wound as a separator 8 as shown in FIG. 6 to form a spiral electrode group 11. The electrode group 11 was housed in the bottomed cylindrical battery case 12 shown in FIG. 6 together with the insulating plate 13, and the negative electrode lead 9 led out from the lower part of the electrode group 9 was connected to the bottom of the battery case 12. Subsequently, the positive electrode lead 10 led out from the upper part of the electrode group 9 is connected to the sealing plate 14, 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 14 having a sealing gasket 15 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 and sealed. The secondary battery was designated as Comparative Example 2.

  The positive electrode plate 6 and the cylindrical lithium ion secondary battery prepared under the above conditions are evaluated for sheet resistance, active material density, battery capacity, battery capacity maintenance rate after 500 cycles of charge / discharge, and short circuit due to contamination. The results of performing are shown in (Table 1).

Here, as a foreign substance mixing test, 100 cells of each cylindrical lithium ion secondary battery were prepared. Each cylindrical lithium ion secondary battery is charged at a constant current of 1.45 A until the voltage reaches 4.25 V, and charged at a constant voltage until the current reaches 50 mA, and then the battery case 12 is charged. The electrode group 11 was taken out from the inside. Nickel having a thickness of 0.1 mm (see FIG. 8A: a), a length of 2 mm (see FIG. 8A: b), and a width of 0.2 mm (see FIG. 8A: c) The plate 22 is bent at an arbitrary point of 2 mm in length and has a thickness of 0.1 mm (see FIG. 8B: A) and a height of 0.2 mm (see FIG. 8B: C). A nickel plate 23 having an L-shaped cross section was obtained. The nickel plate 23 is placed between the positive electrode plate 6 located on the outermost periphery of the electrode group 11 and the separator 8 so that the height direction of the nickel plate 23 is perpendicular to the surfaces of the positive electrode plate 6 and the separator 8 ( In other words, the nickel plate 23 was interposed so that the thickness direction thereof was parallel to the surfaces of the positive electrode plate 6 and the separator 8. Then, the electrode group 11 with the nickel plate 23 interposed was stored again in the battery case 12. Each cylindrical lithium ion secondary battery was pressed with a pressure of 800 N / cm ² . And in each cylindrical lithium ion secondary battery, the number of cells short-circuited among 100 cells (the number of short-circuited cells / 100 cells) was confirmed.

As is clear from Table 1, a plurality of conductive materials 3a that are in conductive contact with each other at the connection point between the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of conductive contacts at each connection point between the positive electrode active materials 2 are in contact with each other. In Examples 1-4 in which the positive electrode current collector 1 can be formed so that the number of the conductive materials 3a is smaller than the number of the conductive materials 3b, the area resistance is 0. It was found that the battery capacity was high by being able to be set to 0.2 to 1.5 Ω · cm ^2, and 70% or more could be secured as the capacity retention rate after 500 cycles of charge and discharge.

  Further, the number of conductive materials 3 a that are in contact with each other at the connection point between the positive electrode active material 2 and the positive electrode current collector 1 is the number of conductive materials 3 b that are in contact with each other at the connection point between the positive electrode active materials 2. In Examples 3 and 4, which can be arranged extremely less than that, a short circuit does not occur even when foreign matter is mixed, and a lithium ion secondary battery with extremely high safety can be realized.

Conversely, a configuration having a plurality of conductive materials 3 a in conductive contact with each other at a connection point between the positive electrode active material 2 and the positive electrode current collector 1 and a plurality of conductive materials 3 b in conductive contact with each other at a connection point between the positive electrode active materials 2. In Comparative Examples 1 and 2, which cannot be formed on the positive electrode current collector 1 so that the number of conductive materials 3a is smaller than the number of conductive materials 3b, the sheet resistance is 0.2 to 1.5Ω. · cm ² and not able to, battery capacity for Comparative example 1 is made up high to some extent, the capacity maintenance rate after 500 cycles of charge and discharge was greater deterioration of about 60%.

  Moreover, about the comparative example 2, since the active material density was not made high, battery capacity was also low, and the capacity maintenance rate after implementing 500 cycles of charging / discharging was about 62%, and deterioration was large.

  Furthermore, it was found that both Comparative Examples 1 and 2 are prone to short-circuiting when foreign matter is mixed because there are many conductive materials at the connection point between the positive electrode active material 2 and the positive electrode current collector 1.

  The present invention relates to a non-aqueous secondary battery in which a positive electrode mixture layer is formed by applying a positive electrode mixture paint obtained by kneading and dispersing a positive electrode active material, a conductive material and a binder with a dispersion medium onto a positive electrode current collector. A positive electrode plate, comprising: a connection point between the positive electrode active material and the positive electrode current collector; and a connection point between the positive electrode active materials and a plurality of conductive materials that are in conductive contact with each other; and the positive electrode active material and the positive electrode current collector By disposing a small amount of conductive material between the body and the body, it is possible to provide a non-aqueous secondary battery that can have high discharge capacity, high charge / discharge cycle characteristics, and high safety at a high potential.

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode active material 3, 3a, 3b Conductive material 4 Binder 5 Positive electrode mixture layer 6 Positive electrode plate 7 Negative electrode plate 8 Separator 9 Negative electrode lead 10 Positive electrode lead 11 Electrode group 12 Battery case 13 Insulating plate 14 Sealing Plate 15 Sealing gasket 16 Press device 17, 18 Positive electrode plate 17a, 18a Positive electrode current collector 17b, 18b, 19b, 20b Area resistance measurement lead wire 19, 20 Cu plate 21 Resistance measurement device 21a, 21b, 21c, 21d Area Resistance measurement terminal 22 Nickel plate 23 Nickel plate

Claims (3)

A positive electrode plate for a non-aqueous secondary battery having a positive electrode mixture layer formed by coating a positive electrode mixture coating material obtained by kneading and dispersing a positive electrode active material, a conductive material and a binder with a dispersion medium on a positive electrode current collector. A positive electrode active material and a positive electrode current collector, and a connection point between the positive electrode active materials and a plurality of conductive materials in electrical contact with each other, and between the positive electrode active material and the positive electrode current collector. A positive electrode plate for a non-aqueous secondary battery, wherein a small amount of the conductive material is disposed. The positive electrode plate for a non-aqueous secondary battery according to claim 1, wherein the positive electrode plate has an area resistance of 0.20 to 1.50 Ω · cm ² . A positive electrode in which a positive electrode active material comprising at least a lithium-containing composite oxide, a conductive material, and a binder are kneaded and dispersed in a dispersion medium are applied onto a positive electrode current collector to form a positive electrode mixture layer A negative electrode mixture layer is formed by coating a negative electrode active material comprising a plate and a material capable of holding at least lithium and a binder mixed with and dispersed in a dispersion medium on a negative electrode current collector. A nonaqueous secondary battery in which a porous insulator is interposed between plates and wound or laminated in a battery case together with a nonaqueous electrolyte solution, the electrode group being constituted by winding or laminating the electrode group. Item 3. A nonaqueous secondary battery using the positive electrode plate for a nonaqueous secondary battery according to any one of Items 1 to 2.

Images