JP2007324074A - Non-aqueous secondary battery electrode plate, manufacturing method thereof, and non-aqueous secondary battery using the same - Google Patents

Abstract

Kind Code: A1 A portion having a different active material density is formed on at least one of a positive electrode plate and a negative electrode plate compressed to a specified thickness, and when forming an electrode group, this portion is a portion having the smallest curvature. Thus, it is possible to provide a non-aqueous secondary battery that suppresses breakage of the electrode plate and dropping of the mixture, has little battery capacity variation, and exhibits good life characteristics.
A first step of applying and forming a positive electrode mixture paint 2 or a negative electrode mixture paint 2 at a location 3 where the thickness of the current collector 1 is reduced, and a positive electrode mixture paint. 2 or the negative electrode mixture paint 2 is dried and then pressed to a predetermined thickness, and at least one of the positive electrode plate 11 and the negative electrode plate 12 is formed with a portion 5 having different active material densities, When forming a group, this part is characterized by making the part having the smallest curvature.
[Selection] Figure 1

Description

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

In recent years, lithium secondary batteries, which are widely used as power sources for portable electronic devices, use a carbonaceous material capable of occluding and releasing lithium for the negative electrode and a composite oxidation of transition metal such as LiCoO ₂ and lithium for the positive electrode. Thus, a lithium secondary battery with a high potential and a high discharge capacity is realized. However, with the recent increase in functionality of electronic devices and communication devices, it is desired to further increase the capacity of lithium secondary batteries.

  Here, as an electrode plate that is a power generation element for realizing a high-capacity lithium secondary battery, a mixture paint in which each constituent material is made into a paint is applied to the current collector on both the positive electrode plate and the negative electrode plate and then dried. Thereafter, a method of compressing to a specified thickness by a press or the like is used. At this time, the active material density is increased by filling and pressing a larger amount of the active material, and the capacity can be further increased.

  However, when the active material density of the electrode plate is increased, the flexibility of the electrode plate is insufficient, and there is a problem that the electrode plate is cut when the electrode plate is processed into a sheet shape and when the electrode plate is wound. . Therefore, in order to improve the flexibility of the electrode plate, for example, as shown in FIG. 3, the positive electrode active material layer 22 provided on one surface of the positive electrode current collector 21 is provided with a plurality of active portions at a predetermined interval by a plurality of recesses 23. A method of configuring the positive electrode plate 20 so as to be divided into material layer units 22U has been proposed (see, for example, Patent Document 1).

Further, in order to eliminate the winding stress applied when the electrode plate is wound and to prevent the electrode plate from cracking and the separator from being cut, an electrode mixture 32 is formed on the current collector 33 as shown in FIG. 4, for example. There has been proposed a method of forming streak grooves on both surfaces of the front surface side 34 and the back surface side 35 on the surface of the electrode plate 31 in a direction perpendicular to the winding direction (see, for example, Patent Document 2).
JP 2002-343340 A JP-A-10-154506

  However, in the prior art in which a recess or streak is provided on the surface of the electrode plate, a reduction in the amount of electrode active material contained in the electrode plate is unavoidable, and the amount of electrode active material necessary for high capacity is secured. In addition, there is a problem that it is difficult to impart sufficient flexibility to the electrode plate, and in particular, to prevent the electrode plate from being cut due to bending stress applied to the electrode plate when forming the electrode group. More specifically, in the prior art of Patent Document 1 described above, the flexibility of the electrode plate is obtained, but by providing a plurality of recesses on the electrode plate, the amount of active material on the current collector is reduced, and high It is difficult to realize a lithium secondary battery with a capacity.

  Moreover, in the prior art of patent document 2, when the thickness of an electrode plate like an alkaline secondary battery is thick, forming a streak is useful in order to prevent a crack of an electrode plate or a separator cut. However, in a lithium secondary battery having a thin electrode plate, the shape and depth of the groove to be formed and the forming method thereof may cause problems such as the electrode plate being easily cut off.

  In the present invention, by forming a portion having a different density of the active material in a portion corresponding to a portion where the curvature of the electrode group constituted by winding at least one of the positive electrode plate and the negative electrode plate is the smallest, An object of the present invention is to provide a non-aqueous secondary battery that suppresses dropping of the mixture, has little battery capacity variation, and exhibits good life characteristics.

  In order to solve the above-described conventional problems, the electrode plate for a non-aqueous secondary battery according to the present invention includes at least an active material composed of a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder using a dispersion medium. A positive electrode plate obtained by applying a kneaded and dispersed positive electrode mixture paint onto a positive electrode current collector, or an active material made of a material capable of holding at least lithium and a water-insoluble polymer binder in a dispersion medium A negative electrode plate obtained by applying a kneaded and dispersed negative electrode mixture paint on a negative electrode current collector, and the curvature of an electrode group formed by winding at least one of the positive electrode plate and the negative electrode plate is the smallest. A portion having a different density of the active material is formed in a portion corresponding to the portion.

  According to the electrode plate for a non-aqueous secondary battery of the present invention, a positive electrode plate or a negative electrode plate in which a portion having a different density of the active material is formed in a portion corresponding to a portion where the curvature of the electrode group formed by winding the electrode plate is the smallest. Since the active material layer for imparting flexibility to the electrode plate is not removed, the active material is not reduced and the battery capacity is reduced. Can be suppressed. In addition, since the flexibility of the electrode plate is improved and the electrode plate can be prevented from being cut when the electrode plate is processed into a sheet shape and when the electrode plate is wound, a highly reliable non-aqueous secondary battery Can be obtained.

  In the first invention of the present invention, a positive electrode mixture paint obtained by kneading and dispersing an active material composed of at least a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder in a dispersion medium is collected. A positive electrode plate coated on an electric conductor, or a negative electrode mixture paint prepared by kneading and dispersing an active material made of a material capable of holding at least lithium and a water-insoluble polymer binder in a dispersion medium. A negative electrode plate coated on an electric body, where the density of the active material differs in a portion corresponding to a portion where the curvature of the electrode group formed by winding at least one of the positive electrode plate and the negative electrode plate is the smallest By forming the electrode plate, the bending stress to the electrode plate at this portion can be relaxed and the electrode plate can be prevented from being cut, and a highly reliable electrode plate for a non-aqueous secondary battery can be provided.

  In the second aspect of the present invention, the active material formed on the positive electrode plate or the negative electrode plate has a density different from that of the entire active material density of the positive electrode plate or the negative electrode plate. By forming the electrode plate, it is possible to obtain an electrode plate for a non-aqueous secondary battery to which flexibility is imparted at the low density portion.

  In the third aspect of the present invention, the portion where the density of the active material formed on the positive electrode plate or the negative electrode plate is different is the concave portion formed on the positive electrode plate or the negative electrode plate. In addition, an electrode plate for a non-aqueous secondary battery can be obtained.

In the fourth aspect of the present invention, a positive electrode mixture paint obtained by kneading and dispersing at least an active material comprising a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder in a dispersion medium is used. A negative electrode current collector comprising a positive electrode plate coated on a body, an active material made of a material capable of holding at least lithium, and a water-insoluble polymer binder mixed and dispersed in a dispersion medium A method for producing a non-aqueous secondary battery comprising: a negative electrode plate applied on top; an electrode group formed by compressing a separator after being wound in a spiral; and an electrolyte comprising a non-aqueous solvent. A first step of applying and forming a portion where the thickness of the positive electrode mixture paint or negative electrode mixture paint is thinned at a portion where the curvature of at least the electrode group of the current collector is the smallest, and the positive electrode mixture paint or negative electrode mixture After the paint has dried, Through the second step, the electrode group is configured so that a portion where the density of the active material is different is formed in one or more of at least one of the positive electrode plate and the negative electrode plate, and then the density is different. It is possible to provide a manufacturing method for obtaining a highly reliable non-aqueous secondary battery by suppressing breakage of the electrode plate when the electrode plate is processed into a sheet shape and when the electrode plate is wound. it can.

  In the fifth aspect of the present invention, a positive electrode current coating material obtained by kneading and dispersing an active material comprising at least a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder in a dispersion medium is used. A negative electrode current collector comprising a positive electrode plate coated on a body, an active material made of a material capable of holding at least lithium, and a water-insoluble polymer binder mixed and dispersed in a dispersion medium A non-aqueous secondary battery comprising a negative electrode plate coated thereon, an electrode group formed by compressing a separator after being wound in a spiral shape, and an electrolyte comprising a non-aqueous solvent, the positive electrode By providing a location where the density of the active material is different at one or more of at least one of the plate and the negative electrode plate, and configuring the electrode group so that the location where the curvature of the electrode group is the smallest is the location where the density is different, the battery There is little capacity variation, One can provide a nonaqueous secondary battery having good life characteristics.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 2, the prismatic lithium secondary battery includes a positive electrode plate 11 using a composite lithium oxide as an active material and a negative electrode plate 12 using a material capable of holding lithium as an active material via a separator 13. Then, the spiral electrode group 14 is housed in a bottomed rectangular battery case (not shown), and then an electrolytic solution (not shown) made of a predetermined amount of nonaqueous solvent is placed in the battery case. Then, a sealing plate (not shown) with a gasket (not shown) attached to the periphery is inserted into the opening of the battery case to seal the opening of the battery case.

  In the electrode plate for a non-aqueous secondary battery of the present invention, as shown in FIG. 2, when the spiral electrode group 14 is configured, the portion 11A where the curvature of the positive electrode plate 11 is the smallest and the curvature of the negative electrode plate 12 are the smallest. A portion having a different density of the active material is formed in the portion 12A.

  In order to form portions with different active material densities in the electrode plate for a non-aqueous secondary battery as described above, first, the positive electrode plate 11 or the negative electrode plate 12 is made of the current collector 1 as shown in FIG. It is produced through a first step of applying and forming a portion 3 where the thickness of the mixture paint 2 is reduced at least at one place. In this first step, as a method of applying and forming the portion 3 where the thickness of the mixture paint 2 is reduced, the current collector is exposed in a direction perpendicular to the longitudinal direction of the electrode plates 11 and 12 using a die coater or the like. An intermittent application system for intermittently forming the part can be used. In this intermittent system, the mixture paint 2 discharged from the tip of the die is stopped by adjusting the pressure inside the die manifold to a negative pressure, but the mixture as shown in FIG. In order to apply and form the portion 3 where the thickness of the paint 2 becomes thin, the timing when releasing the pressure after releasing the pressure inside the manifold of the die and re-ejecting the mixture paint 2 is important. By adjusting, it is possible to form the portion 3 where the thickness of the mixture paint 2 is reduced.

Next, after the mixture paint 2 is dried, it is subjected to a second step in which the mixture paint 2 is pressed to a predetermined thickness, and at least one of the positive electrode plate 11 and the negative electrode plate 12 has a different active material density. As shown in FIG. 1A, when the thickness of the portion 3 where the thickness of the mixture paint 2 is reduced is T, as shown in FIG. 1A, the thickness T is equal to or less than the thickness T as shown in FIG. The method of forming the portion 5 where the active material density of the active material layer is lowered by pressing to a thickness and the active material density is applied by pressing to a thickness equal to or greater than the thickness T as shown in FIG. 5 where the density of the active material is different between the electrode plates 11 and 12 by the method of forming the recess 6 on the electrode plate after drying
, 6 can be formed, but is not limited thereto.

  Hereinafter, an example of a method for producing an electrode plate according to the present invention will be described. When the electrode plate applied to the present invention is wound to form an electrode group, it is necessary to have toughness that prevents the active material layer from cracking or falling off. The prescription of the electrode plate is not limited to the following method as long as the toughness can be exhibited.

  First, the positive electrode active material, conductive material, and binder are placed in an appropriate dispersion medium, mixed and dispersed by a disperser such as a planetary mixer, and adjusted to an optimum viscosity for application to the current collector. The positive electrode mixture paint was prepared.

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

  As the conductive material type 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 for the positive electrode 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. At this time, an acrylate monomer or an acrylate oligomer into which a reactive functional group is introduced can be mixed in the binder.

  Applying the positive electrode mixture paint prepared as described above onto the aluminum foil by adjusting the pressure inside the die manifold to a negative pressure using a die coater. After forming and then drying, it was compressed to a predetermined thickness with a press.

  Next, the negative electrode active material and the binder are put in an appropriate dispersion medium, mixed and dispersed by a disperser such as a planetary mixer, and adjusted to an optimum viscosity for application to the current collector and kneaded. A negative electrode mixture paint was prepared.

  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 modified products thereof are used. In addition, it can be said that it is more preferable to use a cellulosic resin including carboxymethyl cellulose (CMC) or the like in combination or to add a small amount.

For the electrolytic solution, 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 is not particularly limited as long as it has a composition that can withstand the range of use of the lithium ion secondary battery. However, it is common to use a microporous film of an olefin-based resin such as polyethylene or polypropylene as a single or composite. Also preferred as an embodiment. The thickness of the separator is not particularly limited, but may be 10 to 25 μm.

  An embodiment of the present invention will be described with reference to the drawings and tables. First, 100 parts by weight of lithium cobaltate as an active material, 2 parts by weight of acetylene black as a conductive agent 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 2.

  Next, as shown in FIG. 1 (a), this positive electrode mixture paint 2 is applied to a current collector 1 made of aluminum foil having a thickness of 15 μm with a portion 3 where the thickness is reduced, and the mixture on one side after drying is applied. A positive electrode plate 11 having a thickness of 100 μm and a thickness T of a portion 3 where the mixture thickness is reduced to 75 μm was produced. Further, as shown in FIG. 1B, the positive electrode plate 11 is pressed so that the total thickness becomes 165 μm, whereby the active material of the positive electrode active material layer 4 whose mixture thickness on one side becomes 75 μm. A portion 5 where the density was lowered was formed. Thereafter, the positive electrode plate 11 was produced by slitting to a prescribed width of the square 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 the 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 are stirred in a double-arm kneader, Agent paint 2 was prepared.

  Next, the negative electrode mixture paint 2 was applied to a copper foil current collector 1 having a thickness of 10 μm, and after drying, a negative electrode plate 12 having a mixture thickness of 110 μm on one side was prepared. Furthermore, after this negative electrode plate 12 was pressed to a total thickness of 180 μm, it was slitted to a width defined by the rectangular battery, thereby preparing the negative electrode plate 12.

These positive electrode plate 11 and negative electrode plate 12 are formed by winding a polyethylene microporous film having a thickness of 20 μm as a separator, cut to a predetermined length, inserted into a battery case, and mixed with EC, DMC, MEC mixed solvent with LiPF _6. An electrolyte solution in which 3 parts by weight of 1M and VC were dissolved was added and sealed to prepare a square lithium ion secondary battery. Example 1 is a lithium secondary battery in which a portion 5 where the active material density of the active material layer 4 is reduced only in the positive electrode plate 11 is provided in 11A shown in FIG.

  First, using the same positive electrode mixture paint 2 as in Example 1, this positive electrode mixture paint 2 was applied to a current collector 1 made of aluminum foil having a thickness of 15 μm, and after drying, the mixture thickness on one side became 100 μm. A positive electrode plate 11 was produced. Next, this positive electrode plate 11 was pressed to a total thickness of 165 μm, and then slitted to the width defined by the rectangular battery, to produce the positive electrode plate 11. On the other hand, as the negative electrode plate 12, the negative electrode mixture paint 2 similar to that of Example 1 was used, and as shown in FIG. 1A, the negative electrode mixture paint 2 was made of a copper foil current collector having a thickness of 10 μm. 1 was provided with a portion 3 where the thickness was reduced, and applied, and after drying, a negative electrode plate 12 was prepared in which the thickness of the mixture on one side was 110 μm and the thickness T of the portion 3 where the thickness of the mixture was reduced was 85 μm. Further, as shown in FIG. 1B, the negative electrode plate 12 is pressed so that the total thickness becomes 180 μm, whereby the active material of the negative electrode active material layer 4 having a mixture thickness on one side of 85 μm. After forming the portion 5 where the density was lowered, the negative electrode plate 12 was produced by slitting to a prescribed width of the rectangular prismatic battery.

These positive electrode plate 11 and negative electrode plate 12 were made in the same manner as in Example 1 to produce a square lithium secondary battery. Example 2 is a lithium secondary battery in which a portion 5 where the active material density of the active material layer 4 is reduced only in the negative electrode plate 12 is provided in 12A shown in FIG.

  First, as the positive electrode plate 11, the same positive electrode mixture paint 2 as in Example 1 was used, and as shown in FIG. 1A, the positive electrode mixture paint 2 was made of an aluminum foil current collector 1 having a thickness of 15 μm. A portion 3 where the thickness is reduced is provided and coated, and after drying, a positive electrode plate 12 is produced in which the thickness of the mixture on one side is 100 μm and the thickness T of the portion 3 where the thickness of the mixture is reduced is 75 μm. As shown in FIG. 1 (b), by pressing this positive electrode plate 11 so that the total thickness becomes 165 μm, the active material density of the active material layer 4 of the positive electrode in which the mixture thickness on one side becomes 75 μm is low. After forming the portion 5 to be formed, the positive electrode plate 12 was produced by slitting to a prescribed width of the rectangular battery.

  On the other hand, as the negative electrode plate 12, a negative electrode mixture paint 2 similar to that of Example 1 was used, and as shown in FIG. 1A, the negative electrode mixture paint 2 was collected from a 10 μm thick copper foil. The electric conductor 1 is provided with a portion 3 where the thickness is reduced and applied, and after drying, a negative electrode plate 12 is prepared in which the thickness of the mixture on one side is 110 μm and the thickness T of the portion 3 where the thickness of the mixture is reduced is 85 μm. Then, as shown in FIG. 1B, the negative electrode plate 12 is pressed so that the total thickness becomes 180 μm, so that the active material layer 2 of the negative electrode whose mixture thickness on one side becomes 85 μm is obtained. After forming the portion 5 where the density was lowered, the negative electrode plate 12 was produced by slitting to a width defined by the rectangular battery.

  These positive electrode plate 11 and negative electrode plate 12 were made in the same manner as in Example 1 to produce a square lithium secondary battery. Example 3 was a lithium secondary battery in which the active material density in both the positive electrode plate 11 and the negative electrode plate 12 in the rectangular battery was provided in 11A and 12A shown in FIG.

(Comparative Example 1)
First, as the positive electrode plate 11, the positive electrode mixture paint 2 similar to that of Example 1 was used, and this positive electrode mixture paint 2 was applied to a current collector 1 made of aluminum foil having a thickness of 15 μm. A positive electrode plate 12 having a mixture thickness of 100 μm was prepared, and the positive electrode plate 12 was pressed to a total thickness of 165 μm, and then slitted to a prescribed width of the prismatic battery to prepare a positive electrode plate 11. .

  On the other hand, as the negative electrode plate 12, the negative electrode mixture paint 2 similar to that of Example 1 was used, and this negative electrode mixture paint 2 was applied to a copper foil current collector 1 having a thickness of 10 μm, and was dried on one side. The negative electrode plate 12 having a mixture thickness of 110 μm was prepared, and the negative electrode plate 12 was pressed to a total thickness of 180 μm, and then slitted to the prescribed width of the rectangular battery to produce the negative electrode plate 12. did.

  These positive electrode plate 11 and negative electrode plate 12 were made in the same manner as in Example 1 to produce a square lithium secondary battery. Comparative Example 1 was a lithium secondary battery in which the portion 5 where the active material density is low in both the positive electrode plate 11 and the negative electrode plate 12 was not formed.

  As shown in FIG. 2, the lithium secondary battery manufactured under the above conditions is wound with the positive electrode plate 11, the negative electrode plate 12, and the separator 13 to form the electrode group 14, and then the electrode group 14 is disassembled and the electrode Table 1 shows the results of the evaluation on the presence or absence of electrode plate breakage of the plates 11 and 12 and the mixture dropping off.

  As shown in (Table 1), compared with the electrode plate of Comparative Example 1 in which the part where the active material density is low is not formed on the electrode plate, the parts of Examples 1 to 3 in which the part where the active material density is low are formed. It can be seen that the electrode plate can suppress the electrode plate breakage and the mixture drop-off during the electrode group configuration.

  In the electrode plate of Comparative Example 1, when the electrode group was disassembled after the configuration, the electrode plate breakage occurred mostly in the positive electrode plate, and the portion with the smallest curvature when the electrode group was formed (FIG. 2). The fracture in the vicinity of 11A) shown in FIG. On the other hand, the mixture drop occurred mostly in the negative electrode plate, and the mixture drop in the vicinity of the portion with the smallest curvature (12A shown in FIG. 2) was confirmed when the electrode group was formed. .

  Next, the lithium secondary battery manufactured under the above conditions was evaluated according to the following contents. First, as battery capacity variation, the battery after it was stored and stored in a 45 ° C environment for 7 days after charging and discharging twice for a completed battery (a non-defective product without breakage of the electrode plate due to winding and removal of the active material). Twenty battery capacities were measured, and the battery capacity variation in 20 was measured.

  Moreover, as a 300-cycle capacity maintenance rate, after accustoming charge / discharge twice about the completed battery after sealing and preserve | saving for 7 days in a 45 degreeC environment, the following charge / discharge cycles were repeated 300 times. For charging, charging is performed at a constant voltage of 4.2 V and 1400 mA. When charging current is reduced to 100 mA, charging is terminated, and discharging is performed at a constant current of 2000 mA and discharging to a final voltage of 3 V as one cycle. The discharge capacity ratio at the 300th cycle relative to the eye was measured as a 300 cycle capacity retention rate. The contents evaluated for the above items are shown in (Table 2).

As shown in (Table 2), the batteries of Examples 1 to 3 in which the places where the active material density is lowered are formed compared to the battery of Comparative Example 1 where the places where the active material density is lowered are not formed on the electrode plate. It can be seen that the battery capacity variation is small and the capacity retention rate after 300 cycles of charge / discharge is improved. The reason for this is not clear, but by forming a portion where the active material density is low in the electrode plate, it is possible to prevent the electrode plate mixture from dropping (particularly in the negative electrode plate) as described above. Therefore, it is considered that a stable battery capacity can be maintained because the mixture does not easily fall out of the current collector even when charging and discharging are repeated.

  Another embodiment of the present invention will be described with reference to the drawings and tables.

  First, a positive electrode mixture paint 2 was prepared in the same manner as in Example 1. Next, as shown in FIG. 1 (a), this positive electrode mixture paint 2 is applied to a 15 μm thick aluminum foil current collector 1 with a portion 3 where the thickness is reduced, and after drying, the mixture on one side is coated. A positive electrode plate 11 in which the thickness of the agent 3 was 100 μm and the thickness T of the portion 3 where the thickness of the mixture became thin was 75 μm was produced.

  Furthermore, as shown in FIG.1 (c), the positive electrode plate 11 was pressed so that total thickness might be 175 micrometers, and the recessed part 6 with a depth of 5 micrometers was formed in the surface of the positive mix of both surfaces. After that, slitting was performed to a prescribed width of the rectangular prismatic battery to produce the positive electrode plate 11.

  On the other hand, a negative electrode mixture paint 2 was prepared in the same manner as in Example 1. Next, the negative electrode mixture paint 2 was applied to a copper foil current collector 1 having a thickness of 10 μm, and after drying, a negative electrode plate 12 having a mixture thickness of 110 μm on one side was prepared. Further, the negative electrode plate 12 was pressed to a total thickness of 190 μm, and then slitted to a width defined by the rectangular battery, thereby producing the negative electrode plate 12.

These positive electrode plate 11 and negative electrode plate 12 are formed by winding a 20 μm thick polyethylene microporous film as a separator, cut into a predetermined length, inserted into a battery case, and mixed with EC, DMC, and MEC in a mixed solvent of LiPF _6. An electrolyte solution in which 3 parts by weight of 1M and VC were dissolved was added and sealed to prepare a square lithium ion secondary battery. A lithium secondary battery in which the concave portion 6 is provided only on the positive electrode plate 11 in 11A shown in FIG.

  First, using the same positive electrode mixture paint 2 as in Example 1, this positive electrode mixture paint 2 was applied to an aluminum foil current collector 1 having a thickness of 15 μm, and after drying, the mixture thickness on one side was 100 μm. A positive electrode plate 11 was produced. Next, this positive electrode plate 11 was pressed to a total thickness of 175 μm, and then slitted to the width defined by the rectangular battery, to produce the positive electrode plate 11.

  On the other hand, using the same negative electrode mixture paint 2 as in Example 1, as shown in FIG. 1A, the negative electrode mixture paint 2 was formed on a copper foil current collector 1 having a thickness of 10 μm. A thinned portion 3 was provided and applied, and a negative electrode plate 12 having a mixture thickness of 110 μm on one side after drying and a thickness T of the portion 3 where the mixture thickness was reduced to 85 μm was prepared.

  Next, as shown in FIG. 1 (c), the negative electrode plate 12 was pressed to a total thickness of 195 μm, thereby forming a recess 6 having a depth of 5 μm on the surface of the positive electrode mixture on both sides. Then, the negative electrode plate 12 was produced by slitting to a prescribed width of the square battery. These positive electrode plate 11 and negative electrode plate 12 were formed in the same manner as in Example 4 to produce a square lithium secondary battery. Example 5 is a lithium secondary battery in which a concave portion is provided in 12A shown in FIG.

First, as the positive electrode plate 11, the positive electrode mixture paint 2 similar to that of Example 1 was used, and as shown in FIG. 1A, the positive electrode mixture paint 2 was collected from an aluminum foil having a thickness of 15 μm. A portion 3 where the thickness is reduced is provided and applied to the electric body 1, and after drying, a positive electrode plate 11 is produced in which the mixture thickness on one side is 100 μm and the thickness T of the portion 3 where the mixture thickness is reduced is 75 μm. Then, as shown in FIG. 1 (c), after the positive electrode plate 11 is pressed to a total thickness of 175 μm, a recess 6 having a depth of 5 μm is formed on the surface of the positive electrode mixture on both sides. Then, the positive electrode plate 11 was produced by slitting to a prescribed width of the square battery.

  On the other hand, as the negative electrode plate 12, a negative electrode mixture paint 2 similar to that of Example 1 was used, and as shown in FIG. 1A, the negative electrode mixture paint 2 was collected from a 10 μm thick copper foil. The electric conductor 1 is provided with a portion 3 where the thickness is reduced and applied, and after drying, a negative electrode plate 12 is prepared in which the thickness of the mixture on one side is 110 μm and the thickness T of the portion 3 where the thickness of the mixture is reduced is 85 μm. Then, as shown in FIG. 1 (c), the negative electrode plate 12 was pressed so that the total thickness was 195 μm, thereby forming a recess 6 having a depth of 5 μm on the surface of the positive electrode mixture on both sides. The negative electrode plate 12 was manufactured by slitting to a prescribed width of the square battery.

  These positive electrode plate 11 and negative electrode plate 12 were formed in the same manner as in Example 4 to produce a square lithium secondary battery. Example 6 is a lithium secondary battery in which the concave portion 6 is provided in both the positive electrode plate 11 and the negative electrode plate 12 in 11A and 12A shown in FIG.

(Comparative Example 2)
First, as the positive electrode plate 11, the positive electrode mixture paint 2 similar to that of Example 1 was used, and this positive electrode mixture paint 2 was applied to a current collector 1 made of aluminum foil having a thickness of 15 μm. A positive electrode plate 11 having a mixture thickness of 100 μm was prepared, and the positive electrode plate 11 was pressed to a total thickness of 175 μm, and then slitted to a width defined by the rectangular battery, thereby preparing the positive electrode plate 11. .

  On the other hand, as the negative electrode plate 12, the negative electrode mixture paint 12 similar to that of Example 1 was used. The negative electrode mixture paint 2 was applied to the copper foil current collector 1 having a thickness of 10 μm, and was dried on one side. A negative electrode plate 12 having a mixture thickness of 110 μm was prepared, and the negative electrode plate 12 was pressed to a total thickness of 190 μm, and then slitted to a prescribed width of the prismatic battery to prepare the negative electrode plate 12. .

  These positive electrode plate 11 and negative electrode plate 12 were formed in the same manner as in Example 4 to produce a rectangular lithium secondary battery. A lithium secondary battery in which the concave plate 6 is not formed on both the positive electrode plate 11 and the negative electrode plate 12 in the above square battery is referred to as Comparative Example 2. About the lithium secondary battery manufactured under the above conditions, as shown in FIG. 2, after the positive electrode plate 11, the negative electrode plate 12, and the separator 13 are wound to form the electrode group 14, the electrode group 14 is disassembled, Table 3 shows the results of evaluating the electrode plates 11 and 12 for electrode plate breakage and the presence or absence of a mixture drop.

As shown in Table 3, compared with the electrode plate of Comparative Example 2 in which no recess was formed in the electrode plate, the electrode plates of Examples 1 to 3 in which the recesses were formed were broken during the electrode group configuration. It can be seen that the dropping of the mixture can be suppressed. In any of the electrode plates of Example and Comparative Example 2, when the electrode group was disassembled after the construction, the electrode plate breakage occurred mostly in the positive electrode plate, and the most curved when the electrode group was formed. The fracture | rupture in the small part (11A shown in FIG. 2) vicinity was confirmed. On the other hand, the mixture drop occurred mostly in the negative electrode plate, and the mixture drop in the vicinity of the portion with the smallest curvature (12A shown in FIG. 2) was confirmed when the electrode group was formed. .

  In Example 6 in which the concave portions 6 were formed on both the positive electrode plate and the negative electrode plate, even when the electrode plate was bent with a small curvature, the positive electrode plate was cut off and the negative electrode plate joined due to the relaxation effect of the concave portion 6. It is thought that agent dropout can be suppressed.

  Next, the lithium secondary battery manufactured under the above conditions was evaluated according to the following contents. First, as battery capacity variation, the battery after it was stored for 7 days in a 45 ° C environment after being charged and discharged twice for a finished battery after sealing (good product without electrode plate breakage and active material removal). Twenty battery capacities were measured, and the battery capacity variation in 20 was measured.

  Moreover, as a 300-cycle capacity maintenance rate, after accustoming charge / discharge twice about the completed battery after sealing and preserve | saving for 7 days in a 45 degreeC environment, the following charge / discharge cycles were repeated 300 times. For charging, charging is performed at a constant voltage of 4.2 V and 1400 mA. When charging current is reduced to 100 mA, charging is terminated, and discharging is performed at a constant current of 2000 mA and discharging to a final voltage of 3 V as one cycle. The discharge capacity ratio at the 300th cycle relative to the eye was measured as a 300 cycle capacity retention rate. The contents evaluated for the above items are shown in (Table 4).

  As shown in Table 4, the batteries of Examples 1 to 3 in which the recesses were formed compared to the battery of Comparative Example 2 in which no recesses were formed on the electrode plate had less battery capacity variation, and 300 cycles of charge / discharge. It can be seen that the capacity maintenance rate later improves. The reason for this is not clear, but by forming a portion where the active material density is low in the electrode plate, it is possible to prevent the electrode plate mixture from dropping (particularly in the negative electrode plate) as described above. Therefore, it is considered that a stable battery capacity can be maintained because the mixture does not easily fall out of the current collector even when charging and discharging are repeated.

  From the above results, by using the present invention, it is possible to suppress the breakage of the electrode plate when configuring the electrode group, and it is possible to realize a non-aqueous secondary battery with little battery capacity variation and excellent cycle characteristics. It is.

  When the non-aqueous secondary battery according to the present invention forms a portion having different active material densities on at least one of the positive electrode plate and the negative electrode plate compressed to a specified thickness, By making the curvature the smallest, there is less battery capacity variation and better charge / discharge cycle characteristics than conventional non-aqueous secondary batteries, resulting in higher capacity as electronic and communication devices become more multifunctional. It is useful as a portable power source that is desired to be made.

(A) Schematic cross-sectional view showing a state after applying and drying the electrode mixture paint on the electrode plate according to one embodiment of the present invention, (b) after pressing the electrode plate according to the same embodiment Cross-sectional schematic diagram showing the state, (c) cross-sectional schematic diagram showing the state after pressing an electrode plate according to another embodiment of the present invention Sectional drawing which shows the winding state of the electrode group which concerns on one embodiment of this invention Partial sectional view of the electrode plate in the conventional example Partial sectional view of the electrode plate in the conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current collector 2 Mixture paint 3 Place where thickness of mixture paint becomes thin 4 Active material layer 5 Place where active material density of active material layer becomes low 6 Recess 11 Positive electrode plate 11A Place where curvature of positive electrode plate is smallest 12 Negative electrode plate 12A Where the positive electrode plate has the smallest curvature 13 Separator 14 Electrode group

Claims (5)

  A positive electrode plate obtained by applying 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 water-insoluble polymer binder in a dispersion medium onto a positive electrode current collector Or a negative electrode plate obtained by applying a negative electrode mixture paint obtained by kneading and dispersing an active material made of a material capable of holding at least lithium and a water-insoluble polymer binder in a dispersion medium onto a negative electrode current collector In the electrode group formed by winding at least one of the positive electrode plate and the negative electrode plate, a portion having a different density of the active material is formed in a portion corresponding to a portion having the smallest curvature. Electrode plate for non-aqueous secondary battery.   The portion where the density of the active material formed on the positive electrode plate or the negative electrode plate is different is formed so that the density of the active material is smaller than the whole active material density of the positive electrode plate or the negative electrode plate. The electrode plate for non-aqueous secondary batteries according to claim 1.   2. The electrode plate for a non-aqueous secondary battery according to claim 1, wherein the portion having a different density of the active material formed on the positive electrode plate or the negative electrode plate is a recess formed on the positive electrode plate or the negative electrode plate. .   A positive electrode plate formed by applying a positive electrode mixture paint obtained by kneading and dispersing an active material composed of at least a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder in a dispersion medium onto a positive electrode collector; A negative electrode plate obtained by applying a negative electrode mixture coating material obtained by kneading and dispersing an active material made of a material capable of holding lithium at least and a water-insoluble polymer binder in a dispersion medium; An electrode group formed by compressing a separator after being wound in a spiral shape, and a method for producing a non-aqueous secondary battery comprising an electrolyte solution comprising a non-aqueous solvent, wherein at least the electrode of the current collector The first step of applying and forming a portion where the thickness of the positive electrode mixture paint or the negative electrode mixture paint is thinned at a portion having the smallest group curvature, and the positive electrode mixture paint or the negative electrode mixture paint was dried. After that, it is pressed to a predetermined thickness. Through the second step, at least one of the positive electrode plate and the negative electrode plate is formed with a portion where the density of the active material is different, and then the portion where the curvature of the electrode group is the smallest is the density. A method of manufacturing a non-aqueous secondary battery, wherein the electrode group is configured to be at different locations. A positive electrode plate formed by applying a positive electrode mixture paint obtained by kneading and dispersing an active material composed of at least a lithium-containing composite oxide, a conductive material, and a water-insoluble polymer binder in a dispersion medium onto a positive electrode collector; A negative electrode plate obtained by applying a negative electrode mixture coating material obtained by kneading and dispersing an active material made of a material capable of holding lithium at least and a water-insoluble polymer binder in a dispersion medium; A non-aqueous secondary battery comprising an electrode group formed by winding a separator in a spiral shape and then compressed, and an electrolyte solution comprising a non-aqueous solvent, wherein at least one of the positive electrode plate and the negative electrode plate A non-aqueous secondary, wherein the electrode group is configured such that a portion having a different density of the active material is provided at one or more locations, and a portion having the smallest curvature of the electrode group is a portion having a different density. battery.

Images