JP5949485B2 - Power storage device having electrolytic solution, secondary battery, and method for manufacturing electrode of power storage device having electrolytic solution - Google Patents

Description

The present invention relates to a power storage device having an electrolytic solution, a secondary battery, and a method for manufacturing an electrode of a power storage device having an electrolytic solution .

  Power storage devices such as secondary batteries and capacitors are widely used as power sources because they can be recharged and can be used repeatedly. The power storage device includes a sheet-like positive electrode and a sheet-like negative electrode each having an active material layer formed by applying a slurry-like or paste-like active material mixture containing an active material to a metal foil. The electrode assembly is laminated or wound so as to form a layer in the presence of the.

Observing the cross section of the electrode so far, in general, the abundance ratio of the active material in the active material layer was the same in all regions of the active material layer.
In general, in the production process of a sheet-like positive electrode and a sheet-like negative electrode, an active material mixture containing an active material is applied to a band-shaped metal foil and dried to form an active material layer. Roll press is performed to increase the density. However, in a secondary battery using an organic radical compound as an active material, the mechanical strength of the organic radical compound is smaller than that of an inorganic active material, and compaction with deformation is likely to occur. Therefore, the electrode is pressed. There wasn't.

  However, Patent Document 1 proposes a high-capacity secondary battery electrode and a secondary battery that enable pressing of an electrode using an organic radical compound as an active material. The electrode for a secondary battery includes an electrode current collector, an electrode active material containing an organic radical compound, and a particulate conductive additive, and an electrode active material formed on one main surface of the electrode current collector. And the density of the electrode active material layer on the side of the electrode current collector is lower than the density on the side opposite to the electrode current collector side. Moreover, in the manufacturing method of the electrode for secondary batteries, an electrode active material slurry is apply | coated to one main surface of an electrode electrical power collector, an electrode active material layer is formed, and an electrode active material layer is lower than 120 degreeC And a step of pressing at a temperature.

  In recent years, there has been a demand for reducing the use of fossil fuels (restriction of carbon dioxide emissions). As in electric vehicles and hybrid vehicles, power storage devices can be used as a main power source or auxiliary power source to reduce the amount of fossil fuel used or not used. The number of vehicles used for is increasing. And in the electrical storage apparatus used for a vehicle, high output is requested | required.

JP 2011-29135 A

  Patent Document 1 aims to increase the capacity density of a secondary battery by pressing an electrode even in an electrode using an organic radical compound as an active material, as in the case of an electrode using a non-organic radical compound as an active material. It is said. Therefore, there is no description regarding improvement of an electrode using a non-organic radical compound as an active material. Further, Patent Document 1 does not describe anything about high output.

  The present invention has been made in view of the above-mentioned problems, and its object is to use a conventional non-organic radical compound as an active material without using an organic radical compound as an active material. Another object is to provide a power storage device and a secondary battery that can improve output characteristics. Moreover, it is providing the manufacturing method of the electrode.

In order to achieve the above object, the invention according to claim 1 is characterized in that an electrode for a positive electrode and an electrode for a negative electrode each having an active material layer coated with an active material composed of a non-organic radical compound on at least one surface of a metal foil. A power storage device having an electrolyte solution including an electrode assembly laminated with a separator between them, wherein at least one of the positive electrode and the negative electrode is the active material layer The volume of the active material on the side farther from the metal foil than the center in the thickness direction is larger than the volume of the active material on the side closer to the metal foil than the center, and the volume of the active material on the far side the ratio of the volume of the active material in the near side is Ri der 95% or less, the density of the active material layer in the far side is 3.0~3.4g / cm ^3, active in the near side with respect to The density of the material layer is 2.8 to 3.2 g / cm ³ , and the active material layer has the same layer where the volume of the active material layer is large and the volume of the active material layer is small that it has been formed on the inner.

  In the present invention, the volume of the active material constituting the electrode is larger on the side farther from the metal foil than on the side closer to the metal foil. Therefore, the volume of the entire active material is the same, and the output is increased without changing the capacity as compared with an electrode (conventional electrode) in which the volume of the active material is substantially constant. The reason why the output becomes high is that when the volume of the active material is small, the amount of the electrolytic solution entering the active material layer increases. That is, on the side close to the metal foil, it is easy to hold the electrolyte in the active material layer, the discharge reaction proceeds smoothly, and it is close to the metal foil, so that the electricity generated by the discharge reaction easily flows to the metal foil. As a result, the discharge reaction is likely to proceed in a short time, and the output is considered to increase. Therefore, when an electrode using a conventional non-organic radical compound as an active material is provided without using an organic radical compound as an active material, output characteristics can be improved.

In here, the term "formed in the same layer" means that the whole is not mean uniform boundary between the regions (boundary) is not clear. That is, the region where the volume of active material is large and the region where the volume of active material is small are not necessarily uniform in volume as a whole, and regions of different volume exist continuously. May be.

  There are two regions that form a region where the volume of active material is large on the side farther from the metal foil than the center in the thickness direction of the active material layer and a region where the volume of active material is small on the side closer to the metal foil than the center. An active material layer composed of two layers instead of a single layer is obtained by roll-pressing an active material layer formed by applying active material mixtures having different active material volume amounts to a metal foil in two portions. It is formed. On the other hand, in this invention, since the two regions forming the region having a large volume of the active material and the region having a small volume of the active material are formed in the same layer, the volume of the active material is different. Without adjusting the type of active material mixture, after applying one type of active material mixture to the metal foil once, it can be handled in a later step.

According to a second aspect of the present invention, in the first aspect of the present invention, the electrodes having different volume amounts of the active material in the thickness direction of the active material layer are positive electrodes in which the active material is made of a lithium compound. In the present invention, the effect of the invention according to claim 1 can be obtained in a power storage device such as a lithium ion secondary battery or a lithium ion capacitor.

According to a third aspect of the invention, a secondary battery having the configuration of a power storage device according to claim 1 or claim 2. Therefore, the secondary battery of the present invention has the effects of the invention described in claim 1 or claim 2 .

Invention of Claim 4 is a manufacturing method of the electrode of the electrical storage apparatus which has an electrolyte solution which has an active material layer by which the active material which consists of a non-organic radical compound was apply | coated to at least one surface of metal foil, Comprising: An application step of applying the slurry-like or paste-like active material mixture containing the active material to at least one surface of the foil, and after the application in the application step, the active material mixture is dried and the active material A press step of roll pressing the metal foil on which the layer is formed. In the pressing step, the roll press is performed a plurality of times, the gap between the press rolls at the first roll press is set larger than the gap between the press rolls at the last roll press, and The first roll press is performed at a lower pressure than the second and subsequent roll presses.

  In this invention, until it forms an active material layer in metal foil, it carries out similarly to the past, a press process differs from the past, and a multiple times of roll press is performed. The gap between the press rolls in the first roll press among the multiple roll presses is set larger than the gap between the press rolls in the last roll press. The first roll press is performed at a lower pressure than the second and subsequent roll presses. Therefore, in this manufacturing method, the conventional electrode can be used to manufacture the target electrode by performing the roll press in the press process a plurality of times, and can be carried out with an existing apparatus.

The invention according to claim 5 is the invention according to claim 4 , wherein the roll press is performed twice, and the pressurizing force during the first roll press is the pressurizing force during the second roll press. Of 45 to 55%. In this invention, the electrode which has the target performance can be manufactured without changing another manufacturing process by performing a roll press twice in a press process.

The invention according to claim 6 is the invention according to claim 5 , wherein the linear pressure range of the press roll in the pressing step is 10 to 15 kN / cm at the time of the second roll press, At the time of roll press, the value is half that of the second roll press. Therefore, in the present invention, an electrode having a target performance can be easily manufactured.

According to the first to third aspects of the invention, when an electrode using a conventional non-organic radical compound as an active material is provided without using an organic radical compound as an active material, the output characteristics are improved. A power storage device or a secondary battery including an electrolytic solution that can be used can be provided. Moreover, according to invention of Claim 4 -Claim 6 , the manufacturing method of the electrode of the electrical storage apparatus which has the electrolyte solution can be provided.

The partially broken schematic perspective view of the secondary battery of one Embodiment. (A) is a disassembled perspective view which shows typically the positive electrode, negative electrode, and separator which comprise an electrode assembly, (b) is a typical fragmentary sectional view of a positive electrode and a negative electrode. (A) is a schematic cross section of the positive electrode of an Example, (b) is a schematic cross section of the positive electrode of a comparative example. Schematic diagram of a roll press.

Hereinafter, an embodiment in which the present invention is embodied in a secondary battery as a power storage device having an electrolytic solution will be described with reference to FIGS.
As shown in FIG. 1, a secondary battery 10 as a power storage device includes a stacked electrode assembly 12 housed in a case 11 constituted by a case body 11 a and a lid body 11 b. In addition, although not illustrated in the case 11, the electrolyte solution is also accommodated. The secondary battery 10 is embodied as a lithium ion secondary battery.

  As shown in FIG. 2A, the electrode assembly 12 includes a sheet-like positive electrode 13 as a plurality of positive electrodes and a sheet-like negative electrode 14 as a plurality of negative electrodes. The sheet-like separator 15 is laminated between the two. In the positive electrode 13 and the negative electrode 14, portions having active material layers 13 a and 14 a coated with an active material on a metal foil 16 (shown in FIG. 2B) are formed in a rectangular shape, and the active material layers 13 a and 14 a are formed. Tab portions 13c and 14c are formed so as to protrude from the uncoated active material non-applied portions 13b and 14b. As the active material, a general active material made of a non-organic radical compound is used.

  As shown in FIG. 1, the laminated group 17p in which the tab portion 13c is laminated is welded to the positive electrode conductive member 18, and the laminated group 17n in which the tab portion 14c is laminated is welded to the negative electrode conductive member 19. . A positive electrode terminal 20 and a negative electrode terminal 21 are fixed to the lid 11b. The electrode assembly 12 is electrically connected to the positive electrode terminal 20 via the positive electrode conductive member 18 and is electrically connected to the negative electrode terminal 21 via the negative electrode conductive member 19. In addition, each conductive member 18 and 19 is being fixed to the lower surface (inner surface) of the cover body 11b in the state insulated from the case 11 (case main body 11a and the cover body 11b).

Next, the positive electrode 13 will be described in detail.
As shown in FIG. 3A, the positive electrode 13 has an active material 22 on the side where the volume of the active material 22 on the side farther from the metal foil 16 than the center in the thickness direction of the active material layer 13a is closer to the metal foil 16 than the center. The ratio of the volume of the active material 22 on the near side to the volume of the active material 22 on the far side is greater than the volume of the material 22 and is 95% or less. The active material layer 13a has a thickness of 80 μm or more, for example, 95 μm. The density of the active material layer 13a is such that the density on the side close to the metal foil 16 is about 2.8 to 3.2 g / cm ³ , and the density on the side far from the metal foil 16 is 3.0 to 3.4 g / cm ^3. It is about cm ³ . That is, the density of the active material layer 13a on the side farther from the metal foil 16 than the center in the thickness direction of the active material layer 13a is higher than the density of the active material layer 13a on the side closer to the metal foil 16 than the center. The ratio of the amount of the active material 22 on the near side to the amount of the material 22 is 95% or less.

  In FIG. 3 (a), the active material layer 13a has a region far from the metal foil 16 and a region near the metal foil 16 with the center in the thickness direction as a boundary. Although the existence ratio is illustrated equally, the boundary between both areas is not clear. That is, in the active material layer 13a, a region where the volume of the active material 22 is large and a region where the volume of the active material 22 is small are formed in the same layer. In the region far from the metal foil 16, the active material is present in a large proportion near the surface of the active material layer 13a.

FIG. 3B is a schematic diagram in the case where the active material 22 has an active material layer 13a in which the active material 22 exists uniformly. In addition, the density of the active material layer 13a before pressing is about 2.6 g / cm ³ . The active material layer 13a is formed on both surfaces of the metal foil 16, but the illustration of one surface is omitted in FIGS. 3 (a) and 3 (b).

  In addition, the active material existence ratio indicating the ratio of the amount of the active material 22 in the low density region of the active material layer 13a to the amount of the active material 22 in the high region is about 0.9. The abundance ratio of the active material was determined by a binarization method using an electron microscope image of the cross section of the positive electrode 13. Specifically, in an electron microscope image of a cross section obtained by cutting the positive electrode 13 in the thickness direction, the active material layer 13a is divided into a plurality of regions, and the area of the region where the active material 22 exists in each region, and the active material The area of the region where the active material 22 is present is calculated by multiplying the area of the region where the active material 22 is present by 1 and the area of the region where the active material 22 is not present is multiplied by 0 to obtain the total value. And the existence ratio of the active material 22 is represented by the ratio of the total value of both. For example, if the total value in the low density region is S1 and the total value in the high density region is S2, the existence ratio Ra is defined as Ra = S1 / S2. Therefore, the presence ratio of about 0.9 means that the percentage of the active material 22 in the low-density region of the active material layer 13a is about 90% of the amount of the active material 22 in the high region. Represent.

Note that the negative electrode 14 is configured in the same manner as the conventional one, and the density of the active material layer 14a is constant in the thickness direction.
Next , a method for manufacturing the electrode (positive electrode 13) of the power storage device having the electrolytic solution will be described.

  The electrode manufacturing method includes applying a slurry-like or paste-like active material mixture containing an active material to the metal foil 16, and applying the active material mixture in the application step, followed by drying the active material mixture A pressing step of roll-pressing the metal foil 16 on which the layer 13a is formed. Aluminum foil (aluminum sheet) is used as the metal foil 16, and a mixture containing a positive electrode active material made of a non-organic radical compound is used as the active material mixture. In the pressing step, the metal foil 16 on which the active material mixture is applied and dried in the application step to form the active material layer 13a is roll-pressed (roll-pressed).

  As shown in FIG. 4, the roll press is performed when a metal foil 16 having an active material layer 13 a passes between two press rolls 23 and 24. In the pressing step, the roll press is performed twice, and the gap G between the press rolls 23 and 24 at the first roll press is set larger than the gap G between the press rolls 23 and 24 at the second roll press. Then, the first roll press is performed with a lower pressing force than the second roll press.

  In the pressing step, the linear pressure range of the press rolls 23 and 24 is 10 to 15 kN / cm at the time of the second roll press, and at the time of the second roll press at the time of the first roll press (pre-press). Half of the value. The difference between the conditions of the first roll press and the second roll press is that the pressurizing force by the press rolls 23 and 24 is different, but the time and temperature are the same.

  An active material mixture was applied to both sides of an aluminum foil having a thickness of 15 μm, dried, and an electrode intermediate before receiving a roll press in which an active material layer 13a was formed on both sides of a strip-shaped metal foil 16 was prepared. In this state, the thickness of the active material layer 13a was about 115 μm. Next, the belt-shaped electrode intermediate was roll-pressed twice. In the first roll press, the linear pressure of the press rolls 23 and 24 was 6.25 kN / cm, and in the second roll press, the linear pressure of the press rolls 23 and 24 was 12.5 kN / cm. The linear pressure of the press rolls 23 and 24 at the time of the second roll press is the same as that in the manufacturing method in which the conventional roll press is performed once.

  The gap G between the press rolls 23 and 24 at the first roll press was 180 μm, and the gap G between the press rolls 23 and 24 at the second roll press was 130 μm. Using the electron microscopic image of the cross section of the obtained strip-shaped positive electrode 13, the abundance ratio of the active material 22 (active material ratio) was determined by a binarization method. The results are shown in Table 1.

  In addition, when the thickness of the active material layer 13a of the positive electrode 13 obtained by the first roll press and the thickness of the positive electrode 13 obtained by the second roll press were measured, both values were hardly changed. Further, when an electron microscopic image of the cross section of the positive electrode 13 obtained by the first roll press was observed, the presence ratio of the active material 22 in the region closer to the surface of the active material layer 13a, that is, the region far from the metal foil 16, was large. As a whole, the state was almost the same as that of the positive electrode 13 after receiving the second roll press. The reason for this is that pressing of the electrode intermediate is not performed by moving the pressing plate in the thickness direction of the positive electrode 13 but by roll pressing, so that the side far from the metal foil 16, that is, the press rolls 23 and 24. This is probably because a lot of pressure is applied to the side in contact with the surface.

  Moreover, when the surface of the positive electrode 13 which received the 1st roll press and the surface of the positive electrode 13 which received the 2nd roll press were observed, the surface in the case of receiving the 2nd roll press was shining. It was. This is presumably because the active material layer 13a far from the metal foil 16 received more pressure due to the second roll press, and the ratio of the active material 22 in the active material layer 13a increased. .

Further, the obtained strip-shaped positive electrode 13 and the strip-shaped negative electrode 14 configured in the same manner as in the prior art are cut into a predetermined size to form a laminated electrode assembly 12 together with the separator 15, and the electrode assembly The secondary battery 10 was configured using 12. And the capacity | capacitance and output of the secondary battery 10 were measured. The output was measured for 10 seconds. The capacity ratio and output ratio were determined from the measurement results of capacity and output. The capacity ratio was obtained as a ratio to the measured capacity of the first test. The output ratio was determined as a ratio to the measured output of the first test. The measurement test was performed twice under the same conditions. The results of the two tests are shown in Table 1.
(Comparative Example 1)

  As Comparative Example 1, an electrode intermediate body in which an active material layer 13a was formed under the same conditions as in the example was prepared, and the roll press was performed under the same conditions as the second roll press in the example, that is, the lines of the press rolls 23 and 24. The pressure was 1 time at 12.5 kN / cm. Comparative Example 1 corresponds to a normal manufacturing method. Using the electron microscopic image of the cross section of the obtained strip-shaped positive electrode 13, the abundance ratio of the active material 22 (active material ratio) was determined by a binarization method. The results are shown in Table 1.

Further, the obtained strip-shaped positive electrode 13 and the strip-shaped negative electrode 14 configured in the same manner as in the prior art are cut into a predetermined size to form a laminated electrode assembly 12 together with the separator 15, and the electrode assembly The secondary battery 10 was configured using 12. And the capacity | capacitance and output of the secondary battery 10 were measured like the Example, and the capacity | capacitance ratio and the output ratio were calculated | required. The capacity ratio was determined as a ratio to the measured capacity of the first test in the example, and the output ratio was determined as a ratio to the measured output of the first test in the example. The measurement test was performed twice under the same conditions. The results of the two tests are shown in Table 1.
(Comparative Example 2)

  As Comparative Example 2, an electrode intermediate body in which an active material layer 13a was formed under the same conditions as in the example was prepared, and the roll press was performed under the same conditions as the second roll press in the example, that is, the lines of the press rolls 23 and 24. The pressure was applied twice at 12.5 kN / cm. Using the electron microscopic image of the cross section of the obtained strip-shaped positive electrode 13, the abundance ratio of the active material 22 (active material ratio) was determined by a binarization method. The results are shown in Table 1.

  Further, the obtained strip-shaped positive electrode 13 and the strip-shaped negative electrode 14 configured in the same manner as in the prior art are cut into a predetermined size to form a laminated electrode assembly 12 together with the separator 15, and the electrode assembly The secondary battery 10 was configured using 12. And the capacity | capacitance and output of the secondary battery 10 were measured like the Example, and the capacity | capacitance ratio and the output ratio were calculated | required. The capacity ratio was determined as a ratio to the measured capacity of the first test in the example, and the output ratio was determined as a ratio to the measured output of the first test in the example. The results are shown in Table 1.

It can be seen from Table 1 that the active material ratio and the capacity ratio have a variation of about 1% even when the test is performed under the same conditions, and the output ratio is about 1 to 3%.

  From Table 1, the active material ratio is 1.01 and 1.02 in Comparative Example 1 and Comparative Example 2, and the active material layer 13a on the side farther from the metal foil 16 than the center in the thickness direction of the active material layer 13a, It can be seen that the existence ratio of the active material 22 does not change between the active material layer 13a on the side closer to the metal foil 16 than the center. On the other hand, in the examples, the active material ratios are 0.91 and 0.92, and the active material 22 is present on the side closer to the metal foil 16 than the center in the thickness direction of the active material layer 13a. It can be seen that the ratio of the active material 22 on the side close to 16 is as small as 91 to 92%. Therefore, even if the roll pressing is performed twice with normal pressure, the active material 22 in the active material layer 13a on the side farther from the metal foil 16 than the center in the thickness direction of the active material layer 13a is increased. It is confirmed that it is necessary to perform the first roll press with a lower pressure than the second roll press.

  From Table 1, the capacity ratios of the secondary batteries are consistent with each other in Examples, Comparative Example 1 and Comparative Example 2 within the range of variation. Therefore, the active material 22 is 10% of the active material layer 13a on the side farther from the metal foil 16 than the center in the thickness direction of the active material layer 13a and the active material layer 13a on the side closer to the metal foil 16 than the center. It can be seen that the capacity of the secondary battery does not change even if the degree is changed.

  From Table 1, when comparing the output ratio of the secondary battery between Comparative Example 1 and Example, the average value of two times is 0.985 in Example, and 0.795 in Comparative Example 1, and Example Then, it was confirmed that {(0.985-0.975) /0.975} × 100 = 24% with respect to Comparative Example 1, and the output was increased by 24%.

  On the other hand, in Comparative Example 2, the average value of the output ratio twice was 0.69, and compared with Comparative Example 1, {(0.795−0.69) /0.795} × 100 = 13.2. It was confirmed that the output decreased by about 13%. That is, it was confirmed that even when the roll press was performed twice with the same pressure as the conventional one, the capacity of the secondary battery was not changed and the output was reduced. The reason for this is thought to be that although the total amount of the active material 22 does not change, the voids in the active material layer 13a are crushed by two roll presses, and the penetration of the electrolytic solution is deteriorated.

Next, the operation of the secondary battery 10 configured as described above will be described.
Although the secondary battery 10 is used alone, it is generally used as an assembled battery in which a plurality of secondary batteries 10 are connected in series or in parallel. The secondary battery 10 is used for various applications. For example, the secondary battery 10 is mounted on a vehicle and used as a power source for a traveling motor or a power source for other electrical devices.

  When the output specification of the secondary battery 10 is examined, since the density of the active material layer near the metal foil 16 in the active material layer 13a is low, that is, the volume of the active material is small, the active material layer 13a is entered in that region. The amount of electrolyte increases. Therefore, on the side close to the metal foil 16, it is easy to hold the electrolytic solution in the active material layer 13 a, the discharge reaction proceeds smoothly, and it is close to the metal foil 16, so electricity generated by the discharge reaction flows to the metal foil 16. Therefore, it is considered that the discharge reaction easily proceeds in a short time and the output is increased.

According to this embodiment, the following effects can be obtained.
(1) The secondary battery 10 has a state in which the separator 15 exists between the positive electrode 13 and the negative electrode 14 having the active material layers 13a and 14a coated with the active material made of a non-organic radical compound on at least one surface of the metal foil 16. The electrode assembly 12 is laminated. At least one of the positive electrode 13 and the negative electrode 14 (the positive electrode 13 in this embodiment) has a volume amount of the active material 22 on the side farther from the metal foil 16 than the center in the thickness direction in the active material layer 13a. The ratio of the volume of the active material 22 on the near side to the volume of the active material 22 on the far side is larger than the volume of the active material 22 on the side close to the metal foil 16, and is 95% or less. For this reason, the output is increased without changing the capacity, as compared with the case where an electrode in which the entire amount of the active material is the same and the volume of the active material 22 is configured to be substantially constant is provided. Therefore, when an electrode using a conventional non-organic radical compound as an active material is used without using an organic radical compound as an active material, the output characteristics are increased compared to the conventional one without increasing the size of the secondary battery. Can handle large cases. Therefore, it is preferable as a power source for vehicles.

  (2) In the active material layer 13a, a region where the volume of the active material 22 is large and a region where the volume of the active material 22 is small are formed in the same layer. A region where the volume of the active material 22 is larger on the side farther from the metal foil 16 than the center in the thickness direction of the active material layer 13a and a region where the volume of the active material 22 is smaller on the side closer to the metal foil 16 than the center are configured. The active material layer 13a in which the two regions to be formed are formed in two layers instead of one layer is an active material mixture formed by applying the active material mixture having different volume amounts of the active material 22 to the metal foil 16 in two portions. It is formed by roll pressing the material layer 13a. On the other hand, in this embodiment, since the two regions constituting the region where the volume of the active material 22 is large and the region where the volume of the active material 22 is small are formed in the same layer, the volume of the active material 22 After applying one type of active material mixture to the metal foil 16 once without adjusting two types of active material mixes having different amounts, it is possible to cope with it in a subsequent process.

  (3) The electrode in which the volume of the active material 22 in the thickness direction of the active material layer 13a is different is the positive electrode 13 in which the active material 22 is made of a lithium compound. Therefore, the effects (1) and (2) described above can be obtained in a power storage device such as a lithium ion secondary battery or a lithium ion capacitor.

  (4) The manufacturing method of the positive electrode 13 includes applying a slurry-like or paste-like active material mixture having the active material 22 on at least one surface of the metal foil 16, and applying the active material in the applying step. A pressing step of roll-pressing the metal foil 16 on which the mixture is dried and the active material layer 13a is formed. In the pressing step, the roll press is performed twice, and the gap G between the press rolls 23 and 24 at the first roll press is made larger than the gap G between the press rolls 23 and 24 at the second roll press. In addition, the first roll press is performed at a lower pressure than the second roll press. Therefore, in this manufacturing method, the target electrode can be manufactured by performing the roll press twice in the pressing process using conventional equipment, and can be carried out with an existing apparatus.

  (5) In the pressing step, the linear pressure of the press rolls 23 and 24 is 10 to 15 kN / cm at the time of the second roll press, and at the time of the second roll press at the time of the first roll press. Half the value. Therefore, the positive electrode 13 having the desired performance can be easily manufactured.

The embodiment is not limited to the above, and may be embodied as follows, for example.
○ In the secondary battery 10, at least one of the positive electrode 13 and the negative electrode 14 has a metal foil from the side where the volume of the active material 22 in the thickness direction of the active material layers 13 a and 14 a is closer to the metal foil 16. Any configuration may be used as long as the side far from 16 is larger. Therefore, in the negative electrode 14 instead of the positive electrode 13, the volume of the active material 22 in the thickness direction of the active material layer 14 a may be larger on the side farther from the metal foil 16 than on the side closer to the metal foil 16. Also in this case, the output characteristics of both the positive electrode 13 and the negative electrode 14 are improved as compared with the case where the volume of the active material is the same on the side close to the metal foil 16 and the side far from the metal foil 16. Further, in both the positive electrode 13 and the negative electrode 14, the volume of the active material 22 in the thickness direction of the active material layers 13 a and 14 a is larger on the side farther from the metal foil 16 than on the side closer to the metal foil 16. Also good. In this case, the output characteristics are further improved. In the configuration in which the volume of the active material 22 in the thickness direction of the active material layers 13a and 14a is larger on the side farther from the metal foil 16 than on the side closer to the metal foil 16, the density of the active material layers 13a and 14a is higher. The side farther from the metal foil 16 is higher than the side closer to the metal foil 16 in the thickness direction of the active material layers 13a and 14a.

  In the pressing process in the electrode manufacturing method, the roll press may be performed a plurality of times, and may be performed not only twice but also three times or more. When performing the roll press three times or more, the gap between the press rolls 23 and 24 at the first roll press is set larger than the gap between the press rolls 23 and 24 at the last roll press, In addition, the first roll press is performed at a lower pressure than the second and subsequent roll presses. However, the first roll press is performed at a lower pressure than the first roll press when the roll press is performed twice.

  In the case of a manufacturing method in which roll pressing is performed twice, the pressing force at the first roll pressing is not limited to half of the pressing force at the second roll pressing. For example, you may carry out by the magnitude | size of 45 to 55% of the applied pressure in the case of the 2nd roll press.

  The appropriate value of the linear pressure of the press rolls 23 and 24 in the pressing process varies depending on the thickness and density of the active material layers 13a and 14a of the electrode intermediate body before pressing. Therefore, depending on the thickness and density of the active material layers 13a and 14a of the electrode intermediate before pressing, the linear pressure of the press rolls 23 and 24 at the second roll press is made smaller or larger than 10 to 15 kN / cm. Or you may.

  As a roll press apparatus used in the pressing process, an apparatus having two sets of press rolls 23 and 24 may be used, and the second roll press may be performed following the first roll press. In this case, the roll press is more efficient than the case where the electrode that has undergone the first roll press is once wound on the take-up roll and then the taken-up electrode is taken out from the take-up roll and the second roll press is performed. Can be done well.

  ○ The electrode manufacturing method is limited to a method of manufacturing the active material layer formed by applying a single layer of the active material mixture on the metal foil 16 in the coating process by performing a plurality of roll presses in the pressing process. Absent. For example, two types of active material mixtures having different active material contents are prepared, and in the coating step, first, an active material mixture having a low active material content is applied to the metal foil 16 to form a first active material layer. After that, an active material mixture containing a large amount of active material is applied onto the first active material layer, and then the electrode intermediate formed with the second active material layer is roll pressed. Also good. However, the number of man-hours is reduced in the manufacturing method in which the electrode intermediate having an active material layer formed by applying the active material mixture once is subjected to roll pressing a plurality of times (preferably twice).

  The electrodes, that is, the positive electrode 13 and the negative electrode 14 only need to have active material layers 13a and 14a made of a non-organic radical compound on at least one side of the metal foil 16, and have active material layers 13a and 14a on one side instead of both sides. It may be a configuration.

  ○ In the stacked electrode assembly 12, the separator 15 exists between the positive electrode 13 and the negative electrode 14. For example, one of the positive electrode 13 and the negative electrode 14 is formed in a bag shape without using the sheet-like separator 15. The separators and the electrodes that are not accommodated in the bag-shaped separator may be alternately stacked.

(Circle) the secondary battery 10 does not necessarily require electrolyte solution, for example, the separator 15 may be formed with the polymer electrolyte.
The present invention may be applied not only to the stacked electrode assembly 12 but also to the secondary battery 10 including the wound electrode assembly 12.

The secondary battery 10 is not limited to a lithium ion secondary battery, and may be another secondary battery such as a nickel hydrogen secondary battery or a nickel cadmium secondary battery.
The power storage device is not limited to the secondary battery 10 and may be a capacitor such as an electric double layer capacitor or a lithium ion capacitor.

  G ... Gap, 10 ... Secondary battery as power storage device, 12 ... Electrode assembly, 13 ... Positive electrode as positive electrode, 13a, 14a ... Active material layer, 14 ... Negative electrode as negative electrode, 15 ... Separator, 16 ... metal foil, 22 ... active material, 23, 24 ... press roll.

Claims (6)

A positive electrode having an active material layer coated with an active material composed of a non-organic radical compound on at least one surface of a metal foil, and an electrode assembly in which a negative electrode is laminated with a separator therebetween A power storage device having an electrolyte solution ,
In at least one of the positive electrode and the negative electrode, the volume of the active material on the side farther from the metal foil than the center in the thickness direction of the active material layer is greater than the metal foil from the center. greater than the volume of the active material in the side closer to the ratio of the volume of active material Ri der 95% or less, the active material layer in the far side in the side close to the volume of the active material in the far side the density of 3.0~3.4g / cm ^3, density of the active material layer in the side closer is 2.8~3.2g / cm ^3, the active material layer of the active material layer power storage device has a volume large amount region, an electrolytic solution and the volume amount is small region of the active material layer is characterized that you have been formed in the same layer. The active volume amount is different electrode materials in the thickness direction of the active material layer, a power storage device having an electrolytic solution of claim 1 wherein the active material is a positive electrode comprising a lithium compound. The secondary battery provided with the structure of the electrical storage apparatus which has the electrolyte solution of Claim 1 or Claim 2 . A method for producing an electrode of a power storage device having an electrolytic solution, having an active material layer coated with an active material composed of a non-organic radical compound on at least one surface of a metal foil,
An application step of applying a slurry-like or paste-like active material mixture containing the active material to at least one surface of the metal foil;
A press step of roll-pressing the metal foil on which the active material mixture is dried and the active material layer is formed after being applied in the application step;
In the pressing step, the roll press is performed a plurality of times, the gap between the press rolls at the first roll press is set larger than the gap between the press rolls at the last roll press, and A method for producing an electrode of an electricity storage device having an electrolytic solution , wherein the first roll press is performed with a lower pressure than the second and subsequent roll presses. 5. The electrolytic solution according to claim 4 , wherein the roll press is performed twice, and the applied pressure at the first roll press is 45 to 55% of the applied pressure at the second roll press. 6. Manufacturing method of electrode of power storage device having The linear pressure range of the press roll in the pressing step is 10 to 15 kN / cm at the time of the second roll press, and is half the value at the time of the second roll press at the time of the first roll press. The manufacturing method of the electrode of the electrical storage apparatus which has an electrolyte solution of a certain 5 .