JP2007172879A - Battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of obtaining a sufficiently high capacity (improved in high-rate discharge characteristics) even when discharge by large current is carried out. <P>SOLUTION: The non-aqueous electrolyte secondary battery 10 is provided with a positive electrode plate 20 and a negative electrode plate 30 in which mixture layers 22, 32 containing active material are formed on belt-shape current collectors 21, 31. Exposed portions 24, 34 on which the mixture layers 2, 32 are not formed are provided at one side edge part of the current collectors 21, 31, and lead terminals 23, 33 are connected to the expose portions 24, 34. The amount of active material at the starting end parts 21A, 31A on the lead terminal side in width direction is larger than the amount of active material at the terminal parts 21B, 31B on the opposite side in cross-section parallel to short sides 25, 35 of the current collectors 21, 31 in at least one mixture layers 22, 32 out of the mixture layers 22, 32 of the positive electrode plate 20 and the negative electrode plate 30, thereby, high-rate discharge characteristics can be improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery and a manufacturing method thereof.

  For example, nonaqueous electrolyte secondary batteries are widely used as small power sources for mobile phones, digital cameras, notebook personal computers, and the like as secondary batteries that have a high energy density and can be reduced in size and weight. Further, in recent years, taking advantage of the property of high energy density, an increase in size has been actively studied for use as a power source for electric vehicles, hybrid electric vehicles and the like.

Among the above uses, in order to apply a non-aqueous electrolyte secondary battery to a power source for an electric vehicle or a hybrid electric vehicle in particular, a capacity maintenance rate during a large current discharge (hereinafter, referred to as a power source for a portable device) A high-rate discharge characteristic is required. Conventionally, as a nonaqueous electrolyte secondary battery used for such an application, a battery described in Patent Document 1 is known.
JP-A-10-208730

  In the nonaqueous electrolyte secondary battery described in Patent Document 1, a mixture layer containing an active material is formed on the current collector, and a lead terminal is connected to an exposed portion where the mixture layer is not formed. A positive electrode plate and a negative electrode plate. The positive electrode plate and the negative electrode plate are produced by uniformly applying a mixture containing an active material on both sides of the current collector, followed by drying and pressing, so that a mixture layer with a uniform amount of active material is formed. ing.

  Generally, the resistance of the current collector of the electrode plate of the battery increases as the distance from the portion where the lead terminal is connected (hereinafter referred to as the lead terminal connecting portion) increases. On the other hand, the resistance of the mixture layer formed on the current collector is affected by factors such as the distance between the active material in the mixture layer and the current collector, but the mixture layer can be made of a very thin layer. Therefore, it is more susceptible to the above-described resistance in the current collector than the distance between the active material and the current collector. Therefore, under the influence of the resistance in the current collector, a potential difference is generated in which the potential is low in the mixture layer near the lead terminal connection portion and the potential increases as the distance from the lead terminal connection portion increases. This potential difference increases. And in a mixture layer, in a place where electric potential is low, battery reaction preferentially occurs compared with a place where electric potential is high, and the utilization factor of an active material becomes high.

  By the way, when a large current is discharged to the non-aqueous electrolyte secondary battery described in Patent Document 1, the amount of the active material is uniform regardless of the distance from the lead terminal connection portion. In the portion where the rate is high, the active material required for the battery reaction is insufficient, and a sufficient discharge capacity cannot be obtained.

  The present invention has been completed based on the above circumstances, and provides a battery that has a sufficiently high capacity (improved high-rate discharge characteristics) even when discharged by a large current. Objective.

  As a result of intensive studies to achieve the above object, the present inventors have formed a mixture layer that matches the utilization ratio of the active material on at least one of the current collectors of the positive electrode plate and the negative electrode plate. It was found that high capacity can be obtained even during large current discharge.

  As means for achieving the above object, the invention of claim 1 is formed by forming a mixture layer containing an active material on a current collector having a band shape surrounded by a pair of long sides and short sides. In a battery in which a power generation element configured by stacking and winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween is housed in a battery case, the current collector has the mixture on the side edge on one long side thereof An exposed portion in which no layer is formed is provided, a lead terminal is connected to the exposed portion, and at least one of the mixture layers of the positive electrode plate and the negative electrode plate includes the current collector In the cross section parallel to the winding axis of the body, the amount of active material on the lead terminal side in the width direction is larger than the amount of active material on the opposite side.

  According to a second aspect of the present invention, in the mixture layer of both the positive electrode plate and the negative electrode plate according to the first aspect, the lead in the width direction in a cross section parallel to the winding axis of the current collector It is characterized in that the amount of active material on the terminal side is larger than the amount of active material on the opposite side.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the amount of active material in the mixture layer on the lead terminal side is 3% to 20% more than the amount of active material on the opposite side. However, it has characteristics.

  In the invention of claim 4, a mixture layer containing an active material is formed on a current collector having a band shape surrounded by a pair of long sides and short sides, and an exposed portion in which the mixture layer is not formed In the method of manufacturing a non-aqueous electrolyte secondary battery in which a power generation element configured by stacking and winding a positive electrode plate and a negative electrode plate, each having a lead terminal connected thereto, with a separator interposed therebetween, is housed in a battery case. The side edge of one of the long sides is the exposed portion, and at least one mixture layer of the positive electrode plate and the negative electrode plate is on the lead terminal side in the width direction in a cross section parallel to the winding axis. After the mixture is applied to the current collector so that the amount of the active material is larger than the amount of the active material on the opposite side, the density of the active material on the lead terminal side of the mixture layer is the active material on the opposite side. Formed to be higher than the density of the material A method for producing a battery, characterized in that Kigo agent layer is manufactured through a press process of pressing to have a uniform thickness on the current collector.

<Invention of Claim 1>
According to the first aspect of the present invention, in at least one of the mixture layers of the positive electrode plate and the negative electrode plate, the amount of active material on the lead terminal side in the width direction in the cross section parallel to the short side of the current collector is Since the amount of the active material is larger than that on the opposite side, a mixture layer that matches the utilization rate of the active material is formed. Therefore, there is no shortage of active material even during large current discharge. As a result, a sufficient discharge capacity can be obtained.

<Invention of Claim 2>
According to the second aspect of the present invention, since the mixture layer matching the utilization ratio of the active material is formed on both the positive electrode plate and the negative electrode plate, a more preferable discharge capacity can be obtained.

<Invention of Claim 3>
According to the third aspect of the invention, the amount of the active material in the mixture layer on the lead terminal side is 3% to 20% more than the amount of the active material on the opposite side. A mixture layer is formed.

<Invention of Claim 4>
According to the invention described in claim 4, at least one of the positive electrode plate and the negative electrode plate has a cross section parallel to the winding axis, and the active material amount on the side of the lead terminal in the width direction is on the opposite side. After the mixture is applied to the current collector so as to exceed the amount of the active material, the density of the active material on the lead terminal side of the mixture layer is formed to be higher than the density of the active material on the opposite side Since the mixture layer is manufactured through a pressing process in which the mixture layer is pressed so as to have a uniform thickness on the current collector, the battery of the present invention can be easily manufactured.

  <Embodiment 1>

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

  FIG. 1 shows a nonaqueous electrolyte secondary battery 10 (hereinafter referred to as a battery 10) in a completed form in a broken state. The battery 10 includes a battery case 11 formed in a cylindrical shape and a power generation element 15 accommodated therein.

  The battery case 11 includes a metal battery case 11 formed in a cylindrical shape with a bottom and a metal cap 12 formed in a substantially disk shape and sealing the opening of the battery case 11. ing. In the battery case 11, a power generation element 15 configured in a spiral shape is accommodated in a state in which disk-shaped insulating plates 13 are arranged above and below the power generation element 15. A cap 12 is caulked to the opening of the battery case 11 via a sealing gasket 14. In addition, a non-aqueous electrolyte is injected into the battery case 11.

  The non-aqueous electrolyte solution is obtained by dissolving an electrolyte salt in a non-aqueous solvent. Use polar solvents such as formamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, methyl acetate, vinylene carbonate alone or in admixture of two or more. be able to.

The electrolyte salts that dissolve in the non-aqueous solvent are LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ CO ₂ , LiCF ₃ (CF ₃ ) ₃ , LiCF ₃ (C ₂ F ₅ ) ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ , LiN (COCF ₂ CF ₃ ) ₂ , LiPF ₃ (CF ₂ CF ₃ ) _{3 and the} like alone Or a mixture of two or more.

  The power generation element 15 accommodated in the battery case 11 is configured by winding a positive electrode plate 20 and a negative electrode plate 30 with a separator 16 interposed therebetween.

  As the separator 16, a woven fabric, a nonwoven fabric, a synthetic resin microporous membrane, or the like can be used, and a synthetic resin microporous membrane can be particularly preferably used. Among these, polyolefin microporous membranes such as polyethylene and polypropylene microporous membranes, or microporous membranes composed of these can be suitably used in terms of thickness, membrane strength, membrane resistance, and the like.

  The positive electrode plate 20 includes a positive electrode mixture layer 22 (described later) containing a positive electrode active material capable of occluding and releasing lithium ions on both surfaces of a positive electrode current collector 21 having a thickness of 10 to 20 μm formed of a metal such as aluminum. It has. Further, as shown in FIG. 2, the positive electrode current collector 21 has a belt shape, specifically, a shape surrounded by a pair of short sides 25 of 10 to 20 cm and long sides 26A and 26B of 1 to 5 m. There is no. A predetermined belt-like region including the long side 26 </ b> A (the side edge portion on the long side in the present invention) is an exposed portion 24 where the positive electrode mixture layer 22 is not formed. A large number of positive electrode lead terminals 23 are connected to the exposed portion 24 at intervals of about 10 cm so as to intersect the long side 26A. The positive electrode lead terminals 23 are gathered together after being wound, and their tip portions protrude upward from the positive electrode plate 20 and are connected to the cap 12 serving as a positive electrode terminal. As a material of the positive electrode lead terminal 23, a metal such as aluminum, nickel, or titanium can be used.

  As shown in FIG. 4, the positive electrode mixture layer 22 has a substantially uniform thickness with the long side 26 </ b> B from the start end 21 </ b> A adjacent to the exposed portion 24 to the end 21 </ b> A (opposite to the lead terminal 23). And formed substantially symmetrically with respect to the positive electrode current collector 21 so that the thickness of one side thereof is about 100 μm. The positive electrode mixture layer 22 is formed so that the density of the mixture layer decreases as it approaches the end portion 21B from the start end portion 21A. As a result, the amount of active material increases as it approaches the end portion 21B from the start end portion 21A. It is running low. Considering the utilization factor of the active material, the active material amount in the start end portion 21A on the lead terminal 23 side with the highest density in the positive electrode mixture layer 22 is the active material amount on the end portion 21B on the opposite side to the lead terminal 23 with the lowest density. The amount is preferably 3% to 20% more than the amount of the substance (the invention according to claim 3). If the difference in the amount of active material is less than 3%, a mixture layer that matches the utilization rate of the active material is not formed. If the amount exceeds 20%, the difference in the amount of active material between the start end portion 21A and the end portion 21B increases. Thus, the terminal portion 21B is in a state where the active material is insufficient.

The positive electrode active material contained in the positive electrode mixture layer 22 includes a composition formula of Li _x MO ₂ , Li _y M ₂ O ₄ , and Na _x MO ₂ (where M is one or more transition metals, 0 ≦ x ≦ 1 , 0 ≦ y ≦ 2), a metal chalcogenide having a tunnel structure or a layered structure, or a transition metal oxide that occludes and releases lithium such as a metal oxide can be used. Specific examples thereof include LiCoO ₂ , LiNiO ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiCo _x Ni _1-x O ₂ , LiMn ₂ O. ₄ , Li ₂ Mn ₂ O ₄ , MnO ₂ , FeO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ or TiS ₂ .

  A conductive agent, a binder, or the like can be added to the positive electrode active material. As the conductive agent, an inorganic compound or an organic compound can be used. As the inorganic compound, carbon black, graphite and the like can be used, and as the organic compound, for example, a conductive polymer such as polyaniline can be used. As the binder, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylonitrile and the like can be used alone or in combination.

  The negative electrode plate 30 includes a negative electrode mixture layer 32 containing a negative electrode active material capable of occluding and releasing lithium ions on both surfaces of a negative electrode current collector 31 formed of a copper foil having a thickness of 10 to 20 μm formed of a metal such as copper. (To be described later). As shown in FIG. 2, the negative electrode current collector 31 has a band shape, specifically, a shape surrounded by a pair of short sides 35 of 10 to 20 cm and long sides 36A and 36B of 1 to 5 m. Yes. A predetermined belt-like region including the long side 36 </ b> A (long side side edge portion in the present invention) is an exposed portion 34 where the negative electrode mixture layer 32 is not formed. A large number of negative electrode lead terminals 33 are connected to the exposed portion 34 at intervals of about 10 cm so as to intersect the long side 36A. The negative electrode lead terminals 33 are gathered together after being wound, and their tip portions protrude downward from the negative electrode plate 30 and are connected to the bottom of the battery case 11 serving as a negative electrode terminal. As a material of the negative electrode lead terminal 33, a metal such as copper or nickel can be used, and a copper foil plated with nickel is preferable.

  As shown in FIG. 4, the negative electrode mixture layer 32 has a substantially uniform thickness from the start end portion 31A adjacent to the exposed portion 34 to the end portion 31B, and the negative electrode current collector so that the thickness of one side thereof is about 100 μm. It is formed substantially symmetrical with respect to the body 31. The negative electrode mixture layer 32 is formed so as to decrease in density as it approaches the end portion 31B from the start end portion 31A, and as a result, the amount of active material decreases as it approaches the end portion 31B side from the start end portion 31A. Yes. Considering the utilization factor of the active material, the active material amount in the start end portion 31A on the lead terminal 33 side having the highest density in the negative electrode mixture layer 32 is 3 with respect to the active material amount in the end portion 31B having the lowest density. % To 20% is preferable (the invention according to claim 3). If the difference in the amount of active material is less than 3%, a mixture layer that matches the utilization rate of the active material is not formed. If the amount exceeds 20%, the difference in the amount of active material between the start end portion 31A and the end portion 31B increases. Thus, the terminal portion 31B is in a state where the active material is insufficient.

Examples of the negative electrode active material contained in the negative electrode mixture layer 32 include alloys of lithium, such as Al, Si, Pb, Sn, Zn, and Cd, and metals such as LiFe ₂ O ₃ , WO ₂ , MoO ₂ , SiO, and CuO. A carbonaceous material such as oxide, graphite, or carbon, lithium nitride such as Li ₅ (Li ₃ N), metallic lithium, or a mixture thereof can be used.

  In the present embodiment, from the viewpoint of improving the high rate discharge characteristics, the active material amounts of the start end portions 21A and 31A are the end portions 21B and 31B for both the positive electrode mixture layer 22 and the negative electrode mixture layer 32. (The inventions of claims 2 and 5) are included in the present invention, but only one mixture layer is formed in this way.

  In the present embodiment, the positive electrode mixture layer 22 and the negative electrode mixture layer 32 are formed so that the thicknesses thereof are substantially uniform from the start end portions 21A and 31A to the end end portions 21B and 31B, and the density of the mixture is the start end portion. It is formed so that the density decreases as it approaches the terminal portions 21B and 31B from 21A and 31A, but it is formed so that the amount of active material of the starting end portions 21A and 31A is larger than that of the terminal portions 21B and 31B. For example, as shown in FIG. 3, the present invention includes those having a difference in thickness between the start end portions 21A and 31A and the end end portions 21B and 31B.

Next, a method for manufacturing the battery 10 of this embodiment will be described.
First, the positive electrode plate 20 and the negative electrode on which the mixture layers 22 and 32 are formed by applying the mixture composition corresponding to both surfaces of the current collectors 21 and 31, drying and rolling with a roll press machine. A plate 30 is manufactured. In the present invention, as a result, at least one of the mixture layer 22 of the positive electrode plate 20 and the mixture layer 32 of the negative electrode plate 30, the start end portion 21 </ b> A on the lead terminal side 23, 33 side of the current collectors 21, 31, The active material amount of 31A may be formed so as to be larger than that of the terminal portions 21B and 31B on the opposite side to the lead terminals 23 and 33.

  Specifically, as shown in FIG. 3, when the mixture is applied onto the current collectors 21 and 31, the amount of the mixture applied as it approaches the end portions 21B and 31B from the start end portions 21A and 31A side. Is applied so that the active material amount of the start end portions 21A, 31A on the lead terminals 23, 33 side is larger than that of the end portions 21B, 31B (hereinafter referred to as application step), as shown in FIG. By pressing the mixture layers 22 and 32 so that the thicknesses of the mixture layers 22 and 32 are substantially uniform from the start end portions 21A and 31A to the end portions 21B and 31B, the density of the start end portions 21A and 31A becomes higher than that of the end portions 21B and 31B. The positive electrode plate 20 and the negative electrode plate 30 are manufactured through a process (hereinafter referred to as a pressing process) (the invention according to claim 4). In the present embodiment, preferably, the positive electrode plate 20 and the negative electrode plate 30 in which the density of the start end portions 21A and 31A of the mixture layers 22 and 32 is higher than the end portions 21B and 31B can be easily manufactured. It is manufactured by the method.

  In the present invention, the positive electrode plate 20 and the negative electrode plate 30 are manufactured by pressing the mixture layers 22 and 32 so that the thicknesses of the mixture layers 22 and 32 are not uniform after the application step. Alternatively, after the mixture is applied to the current collectors 21 and 31 without adjusting the application amount, pressing is performed so that the amount of active material at the start end portions 21A and 31A is larger than that at the end portions 21B and 31B. May be manufactured.

  When applying the mixture, common application methods such as reverse roll method, direct roll method, blade method, knife method, die nozzle method, and dip method can be used, but the application amount is controlled mechanically. Since it is easy, it is preferable to carry out by a die nozzle method.

  When pressing the mixture layer, the right and left forces of the rolls may be changed and roll pressing may be performed, or the distance between the rolls may be changed and roll pressing may be performed.

  A winding step in which the long side 21A side of the positive electrode plate 20 obtained by the above method and the long side 31B side of the negative electrode plate 30 are made to correspond with the separator 16 interposed therebetween, and winding is performed around one short side 25, 35. After that, the power generation element 15 is manufactured. The lead terminals 23 and 33 connected to the positive electrode plate 20 and the negative electrode plate 30 are attached to the ends of the exposed portions 24 and 34 of the positive electrode plate 20 and the negative electrode plate 30 using means such as ultrasonic welding during the winding process.

  Next, the power generation element 15 manufactured after finishing the winding process is accommodated in the battery case 11, impregnated with the non-aqueous electrolyte, and then sealed in the container to manufacture the battery 10 of the present embodiment.

  According to the present embodiment, for both the positive electrode mixture layer 22 and the negative electrode mixture layer 32, the active material amount of the start end portions 21A and 31A of the mixture layers 22 and 32 is larger than the end portions 21B and 31B. The amount of the active material is large in the portion where the utilization factor of the active material is high, and the amount of the active material is small in the portion where the utilization factor of the active material is low. Therefore, even when discharging with a large current is performed, a sufficiently high discharge capacity can be obtained because the active material required for the battery reaction is not insufficient even in a portion where the active material utilization rate is high.

<Examples 1 to 5 and Comparative Example 1>
Examples of the present invention and comparative examples are shown below, but the present invention is not limited thereto.
1. Battery fabrication
In Examples 1 to 5 and Comparative Example 1, a battery 10 according to Embodiment 1 shown in FIG.
(1) Preparation of positive electrode plate 91 parts by weight of LiCoO ₂ , 3 parts by weight of acetylene black as a conductive agent, and 6 parts by weight of polyvinylidene fluoride as a binder were mixed, and N-methyl-2-pyrrolidone was appropriately added. A composition containing a positive electrode active material (hereinafter referred to as a positive electrode mixture composition) was prepared in the form of a paste.

  This positive electrode mixture composition was applied to both surfaces of an aluminum positive electrode current collector 21 having a thickness of 20 μm by a die nozzle method while adjusting the discharge amount. At this time, for Examples 1 to 4, the positive electrode mixture composition was applied so that the amount of application gradually decreased as it approached the end portion 21B from the start end portion 21A of the positive electrode mixture layer 22 as shown in FIG. In Example 5 and Comparative Example 1, the positive electrode mixture composition was uniformly applied from the start end 21A to the end end 21B.

  After the positive electrode plate 20 that has undergone the coating process is dried, it is compression molded by a roll press so that the thickness is uniform, and as shown in FIG. 3, the positive electrode mixture layer 22 and the exposed portion 24 having a predetermined thickness are formed. In the positive electrode mixture layer 22, the value obtained by dividing the mixture application weight per unit volume of the start end portion 21A by the mixture application weight per unit volume of the end portion 21B is shown in Table 1 (hereinafter referred to as the positive electrode mixture layer). A positive electrode plate 20 having a mixture weight ratio) was obtained. Here, when the weight ratio of the positive electrode mixture is 1.1, for example, it indicates that the amount of the active material at the start end portion 21A is 10% larger than the amount of the active material at the end portion 21B.

(2) Preparation of negative electrode plate Composition containing 92 parts by weight of graphite and 8 parts by weight of polyvinylidene fluoride as a binder, and appropriately adding N-methyl-2-pyrrolidone to contain a paste-like negative electrode active material (Hereinafter referred to as a negative electrode mixture composition) was prepared.

  This negative electrode mixture composition was applied to both surfaces of a copper negative electrode current collector 31 having a thickness of 14 μm by a die nozzle method while adjusting the discharge amount. At this time, for Examples 1, 2, and 5, as shown in FIG. 2, the negative electrode mixture composition was formed so that the coating amount gradually decreased as the negative electrode mixture layer 32 approached the end portion 31B from the start end portion 31A. It applied and about Example 3, 4 and the comparative example 1, the negative mix composition was apply | coated uniformly from the end part 31A to the terminal part 31B.

  After drying the negative electrode plate 30 that has undergone the coating process, the negative electrode plate 30 is compression-molded by a roll press, and includes a negative electrode mixture layer 32 and an exposed portion 34 of a predetermined thickness. A negative electrode plate 30 was obtained in which the value obtained by dividing the mixture coating weight per unit volume by the mixture coating weight per unit volume of the terminal portion 31B was the value shown in Table 1 (hereinafter referred to as the negative electrode mixture weight ratio). . Here, when the weight ratio of the negative electrode mixture is 1.1, for example, it indicates that the active material amount of the start end portion 31A is 10% larger than the active material amount of the end portion 31B.

(3) Fabrication of battery The positive electrode plate 20 obtained in (1), the separator 16 made of a microporous polyethylene film having a thickness of 25 μm, and the negative electrode plate 30 obtained in (2) were sequentially stacked. Was wound around an oblong spiral core made of polyethylene into an ellipse to form a power generation element 15. At this time, the winding center axis of the power generation element 15 was made parallel to the long side of the core. During the winding process, the lead terminal 23 made of aluminum was ultrasonically welded to the exposed portion 24 of the positive electrode plate 20, and the lead terminal 33 made of copper was ultrasonically welded to the exposed portion 34 of the negative electrode plate 30. The power generation element 15 obtained in this way was housed in the battery case 11 and an electrolyte was injected. At this time, the winding central axis of the power generation element 15 was set to be perpendicular to the opening surface of the battery case 11. The nominal capacity was 5 Ah.

2. Battery performance test The batteries of Examples 1 to 5 and Comparative Example 1 obtained by the above method were subjected to the following performance tests, and the results are shown in Table 1.
(1) Capacity retention during 40 A discharge (high rate discharge characteristics)
The batteries 10 of Examples 1 to 5 and Comparative Example 1 were charged at a constant current of 5 A to 4.2 V at 25 ° C., then charged at a constant voltage of 4.2 V for a total of 3 hours, and then at a current of 5 A. It discharged to 2.7V and measured the discharge capacity at the time of 5A discharge. Next, the discharge capacity at 40 A discharge was measured in the same manner except that the discharge voltage was 40 A. And the ratio (percentage display) of the capacity | capacitance at the time of 40A discharge with respect to the capacity | capacitance at the time of 5A discharge is made into the capacity | capacitance retention at the time of 40A discharge, and it shows that a high rate discharge characteristic is so high that this value is large.
The test results, the positive electrode mixture density ratio, and the negative electrode mixture density ratio are shown in Table 1 in correspondence.

3. Test Results and Discussion The batteries of the present invention (Examples 1 to 5) had higher high rate discharge characteristics than the battery of Comparative Example 1. Considering this result, in the batteries of Examples 1 to 5, at least one of the positive electrode mixture layer 22 and the negative electrode plate mixture layer 32 has an active material amount on the side opposite to the lead terminals 23 and 33 side. It is formed to be larger than the amount of substance. That is, in the mixture layers 22 and 32, the amount of the active material is large in the portion where the utilization factor of the active material is high, and the amount of the active material is small in the portion where the utilization factor of the active material is low. It is considered that a sufficiently high discharge capacity was obtained without a shortage of active material required for the reaction.

  In particular, the high-rate discharge characteristics were high for the positive electrode mixture layer 22 and the negative electrode mixture layer 32 in which the densities of the start end portions 21A and 31A were increased (Examples 1 and 2). This is considered to be because a higher discharge capacity could be obtained by providing the mixture layers 22 and 32 in accordance with the active material utilization rate for both the electrode plates 20 and 30.

  Further, the density of the starting end portion 21A only for the positive electrode mixture layer 22 (Examples 3 and 4) and the density of the starting end portion 31A for only the negative electrode mixture layer 32 (Example 5) are compared. As a result, the former had higher high-rate discharge characteristics. This is because when the positive electrode mixture layer 22 and the negative electrode mixture layer 32 are compared, the positive electrode mixture layer 22 has a higher electrical resistance in consideration of the properties of the active material and the like used. It is considered that the effect of forming the mixture layer in accordance with was more prominent.

4). Summary As described above, according to the present invention, a nonaqueous electrolyte secondary battery having high high rate discharge characteristics can be provided.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.

  (1) In the present invention, not only a nonaqueous electrolytic solution but also a solid electrolyte may be used, or both may be used in combination. As the solid electrolyte, a known solid electrolyte can be used. For example, an inorganic solid electrolyte or a polymer solid electrolyte can be used. When a gel polymer solid electrolyte is used, the electrolyte constituting the gel may be different from the electrolyte contained in the pores of the active material of the electrode plate. A synthetic resin microporous membrane and a polymer solid electrolyte can also be used in combination.

  (2) Although a cylindrical battery case is used in the first embodiment, the battery case may be oval or bag-shaped, and the material may be a metal laminate resin film.

Overall view of the battery of Embodiment 1 Plan view of positive and negative plates Cross-sectional view in the short side direction of the positive electrode plate and negative electrode plate before the pressing process Cross-sectional view in the short side direction of the positive electrode plate and negative electrode plate after the pressing process

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Battery 20 ... Positive electrode plate 21 ... Positive electrode collector 21A ... Start part 21B ... Termination part 22 ... Positive electrode mixture layer 23 ... Positive electrode lead terminal 24 ... Exposed part 30 ... Negative electrode plate 31 ... Negative electrode collector 31A ... Start end part 31B ... Terminal part 32 ... Negative electrode mixture layer 33 ... Negative electrode lead terminal 34 ... Exposed part

Claims (4)

A structure in which a positive electrode plate and a negative electrode plate formed by forming a mixture layer containing an active material on a current collector having a band shape surrounded by a pair of long sides and short sides are overlapped and wound with a separator interposed therebetween. In the battery that houses the generated power generation element in the battery case,
The current collector is provided with an exposed portion where the mixture layer is not formed on the side edge portion on one long side thereof, and a lead terminal is connected to the exposed portion,
In at least one of the mixture layers of the positive electrode plate and the negative electrode plate, the amount of active material on the lead terminal side in the width direction in a cross section parallel to the winding axis of the current collector, A battery characterized by having a larger amount of active material on the opposite side. In the mixture layer of both the positive electrode plate and the negative electrode plate, the active material amount on the lead terminal side in the width direction in the cross section parallel to the winding axis of the current collector is the active material amount on the opposite side. The battery according to claim 1, wherein the battery is more than. 3. The battery according to claim 1, wherein the active material amount of the mixture layer on the lead terminal side is 3% to 20% more than the active material amount on the opposite side. A mixture layer containing an active material is formed on a current collector having a strip shape surrounded by a pair of long sides and short sides, and lead terminals are connected to exposed portions where the mixture layer is not formed. In the method of manufacturing a battery in which a power generation element configured by stacking and winding a positive electrode plate and a negative electrode plate sandwiched between separators in a battery case,
A side edge portion on one long side of the current collector is the exposed portion,
In at least one of the positive electrode plate and the negative electrode plate, the amount of the active material on the lead terminal side in the width direction is larger than the amount of the active material on the opposite side in the cross section parallel to the winding axis. After applying the mixture to the current collector,
It is formed so that the density of the active material on the lead terminal side of the mixture layer is higher than the density of the active material on the opposite side, and the mixture layer has a uniform thickness on the current collector A battery manufacturing method, wherein the battery is manufactured through a pressing step.

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