JP6730201B2 - Wet powder film formation method - Google Patents

Description

The present invention also relates to the wet powder deposition how. More specifically, about the wet powder deposition how the formation of the wet powder into a sheet.

Electrode plates used in batteries such as lithium ion secondary batteries are generally manufactured by forming an electrode mixture layer on a current collector foil. Further, in forming the electrode mixture layer, a wet granulated product obtained by adding a solvent to a powder such as an active material which is a material forming the electrode mixture layer may be used. That is, there is a method in which the electrode mixture layer is formed by pressing a wet granulated material through a gap between a pair of rolls to form the wet particle into a sheet.

As a prior art relating to the film formation of such a wet powder, for example, the one described in Patent Document 1 can be cited. In Patent Document 1, a mixture coating material is passed through a gap between opposing roll pairs to form a film on one roll of the roll pair, and then the film mixture coating material on the roll is coated. Techniques for transferring onto a coating are disclosed. Further, in Patent Document 1, a uniform coating material can be obtained on the coating object by adjusting the contact angle between the solvent contained in the mixture coating material and the roll surface or the surface of the coating object. It is said to be possible.

JP, 2005-178093, A

However, even by the above-mentioned conventional technique, there are cases where the electrode mixture layer formed on the surface of the current collector foil has a nonuniform thickness portion. That is, it could not be said that the electrode mixture layer having a sufficiently uniform thickness could be formed on the collector foil.

The present invention has been made for the purpose of solving the above-mentioned problems of the conventional technique. That it is an object thereof is to provide a wet powder deposition how capable thickness on the current collector foil to form a uniform electrode mixture layer.

In order to solve this problem, the wet powder film forming method of the present invention comprises passing a wet granulated product formed by mixing a solvent with at least an active material and a binder through a gap between roll pairs. A wet powder film-forming method of forming an electrode mixture layer on a current collector foil by forming it into a sheet shape while adhering it to a current collector foil, wherein a wet granulation product is used as an active material and a binder. Is formed by a first stirring step of mixing with a solvent by stirring to obtain these mixtures and a second stirring step of mixing the mixture with a solvent and a surfactant by stirring, and The weight ratio of the solvent and the surfactant is set such that the contact angle of the active material with respect to the mixed liquid obtained by mixing the solvent and the surfactant is within the range of 10° or more and 80° or less. The wet powder film forming method is characterized in that the ratio of the weight of the solid content to the total weight is within the range of 63% or more and 92% or less.

In the wet powder film forming method according to the present invention, the wet granulation body is formed by adding a surfactant in the second stirring step. Further, the wet granulation body is formed with the contact angle of the active material to the mixed liquid of the solvent and the surfactant and the ratio of the weight of the solid content to the total weight within a predetermined range. Then, the wet granulation body can form an electrode mixture layer having a uniform thickness on the collector foil.

According to the present invention, it is wet powder deposition how capable thickness on the current collector foil to form a uniform electrode mixture layer is provided.

It is sectional drawing of an electrode plate. It is a schematic block diagram of a wet powder film-forming apparatus. It is a figure for demonstrating the formation method of a wet granulated material. It is a figure for demonstrating the measuring method of a contact angle.

Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the drawings.

First, the electrode plate 100 manufactured by the method of the present embodiment will be described with reference to FIG. The electrode plate 100 has a collector foil 110 and an electrode mixture layer 120, as shown in the sectional view of FIG. 1. The electrode plate 100 is long in the left-right direction in FIG. In the electrode plate 100 of this embodiment, the electrode mixture layer 120 is formed only on the first surface 111 of the current collector foil 110. The electrode plate 100 of this embodiment is used as, for example, a positive electrode plate or a negative electrode plate of a lithium ion secondary battery.

The collector foil 110 is, for example, a metal foil. For example, when the electrode plate 100 is a positive electrode plate of a lithium ion secondary battery, an aluminum foil can be used as the collector foil 110. Further, for example, when the electrode plate 100 is a negative electrode plate of a lithium ion secondary battery, a copper foil can be used as the collector foil 110.

The electrode mixture layer 120 contains at least an active material 121 and a binder 122. For example, in a lithium ion secondary battery, the active material 121 contributes to charge and discharge by inserting and extracting lithium ions. Further, the binder 122 binds the materials forming the electrode mixture layer 120 to each other to form the electrode mixture layer 120, and the electrode mixture layer 120 is formed on the first surface 111 of the current collector foil 110. It is for binding.

Furthermore, the electrode mixture layer 120 of the present embodiment contains a surfactant 124. The action and the like of the surfactant 124 will be described later in detail.

When the electrode plate 100 is a positive electrode plate of a lithium ion secondary battery, for example, NMC (LiNi _1/3 Co _1/3 Mn _1/3 O ₂₎ which is a ternary positive electrode active material is used as the active material 121. ) And polyvinylidene fluoride (PVdF) as the binder 122. When the electrode plate 100 is a negative electrode plate of a lithium ion secondary battery, for example, graphite can be used as the active material 121 and carboxymethyl cellulose (CMC) or sodium polyacrylate can be used as the binder 122.

Next, a method for manufacturing the electrode plate 100 in this embodiment will be described. In this embodiment, the electrode plate 100 is manufactured using the wet powder film forming apparatus 1 shown in FIG. As shown in FIG. 2, the wet powder film forming apparatus 1 has a first roll 10, a second roll 20, and a third roll 30. In FIG. 2, the vertical direction is the vertical direction, and gravity acts downward.

In the wet powder film forming apparatus 1 of this embodiment, all of the first roll 10, the second roll 20, and the third roll 30 are arranged in a state where the axial direction is horizontal. The first roll 10, the second roll 20, and the third roll 30 are made of a material such as metal. Further, the first roll 10 and the second roll 20 are arranged in parallel with their outer peripheral surfaces 11 and 21 facing each other at the first facing position A. The third roll 30 is arranged in parallel with the second roll 20 with the outer peripheral surface 31 facing the outer peripheral surface 21 of the second roll 20 at the second facing position B.

The first roll 10 and the second roll 20 are held so that the distance between the axes is constant. A gap GA is provided between the outer peripheral surface 11 of the first roll 10 and the outer peripheral surface 21 of the second roll 20 at the first facing position A. Further, the third roll 30 is held so that the axial distance from the second roll 20 is constant. A gap GB is provided between the outer peripheral surface 21 of the second roll 20 and the outer peripheral surface 31 of the third roll 30 at the second facing position B.

The first roll 10, the second roll 20, and the third roll 30 are each rotated when the electrode plate 100 is manufactured. In FIG. 2, the rotation directions of the first roll 10, the second roll 20, and the third roll 30 are indicated by arrows. That is, in FIG. 2, the rotation directions of the first roll 10 and the third roll 30 are clockwise, and the rotation direction of the second roll 20 is counterclockwise.

The rotation directions of the first roll 10 and the second roll 20 are such that the movement directions of the outer peripheral surfaces 11 and 21 at the first facing position A are the same. Specifically, the rotation directions of the first roll 10 and the second roll 20 are such that the movement directions of the outer peripheral surfaces 11 and 21 at the first facing position A are both downward in the vertical direction. The rotation direction of the third roll 30 is such that the movement direction of the outer peripheral surface 31 at the second facing position B is the same as the movement direction of the outer peripheral surface 21 of the second roll 20.

In addition, in the present embodiment, the second roll 20 rotates at a peripheral speed higher than the peripheral speed of the first roll 10. Further, the third roll 30 rotates at a peripheral speed higher than that of the second roll 20. That is, the first roll 10, the second roll 20, and the third roll 30 have a high peripheral speed of rotation in this order.

Further, a partition 90 is provided above the first facing position A. The partition part 90 is an enclosure for preventing the wet granulated material 130 from spilling from the upper surfaces of the first roll 10 and the second roll 20. The wet granulated material 130 is accumulated inside the partition part 90. The wet granulated material 130 is supplied from the inside of the partition part 90 to the first facing position A by the rotation of the first roll 10 and the second roll 20.

Further, as shown in FIG. 2, a current collector foil 110 is wound around the outer peripheral surface 31 of the third roll 30. The current collector foil 110 is wound around the second facing position B of the third roll 30 with the second surface 112 side facing the outer peripheral surface 31 of the third roll 30. Therefore, the collector foil 110 is conveyed by the rotation of the third roll 30.

The first surface 111 of the current collector foil 110 faces the outer peripheral surface 21 of the second roll 20 at the second facing position B. The third roll 30 rotates at a peripheral speed higher than that of the second roll 20, as described above. Therefore, the moving speed of the first surface 111 of the current collector foil 110 at the second facing position B is faster than the moving speed of the outer peripheral surface 21 of the second roll 20 at the second facing position B.

The collector foil 110 is supplied into the wet powder film forming apparatus 1 from the lower right of the third roll 30 in FIG. 2, passes through the second facing position B, and is discharged toward the upper right of the third roll 30. Is transported as described above. When the current collector foil 110 is supplied to the wet powder film forming apparatus 1, nothing is formed on the first surface 111 thereof. Then, the wet powder film forming apparatus 1 can manufacture the electrode plate 100 by forming the electrode mixture layer 120 on the first surface 111 of the current collector foil 110 at the second facing position B. ..

Next, a process of manufacturing the electrode plate 100 by the wet powder film forming apparatus 1 will be described. First, the wet granulated material 130 supplied to the inside of the partition part 90 is sent to the first facing position A by the rotation of the first roll 10 and the second roll 20 in order from below.

The wet granulated material 130 that has reached the first facing position A passes through the gap GA by the rotation of the first roll 10 and the second roll 20, and at the time of passing through the gap GA, the wet granulated product 130 and the outer peripheral surface 11 of the first roll 10 The pressure is applied between the outer surface 21 of the two rolls 20. By this pressurization, the wet granulated material 130 is rolled, and the particles in the wet granulated material 130 are bound together by the action of the binder 122. As a result, the wet granulation product 130 that has passed the first facing position A is formed into a sheet shape, and becomes a film-forming sheet 131.

Further, the film-forming sheet 131 is attached to one of the outer peripheral surface 11 of the first roll 10 and the outer peripheral surface 21 of the second roll 20 that has a faster moving speed at the first facing position A. As described above, in the wet powder film forming apparatus 1, the second roll 20 has a higher peripheral speed than the first roll 10. That is, the film formation sheet 131 formed at the first facing position A adheres to the outer peripheral surface 21 of the second roll 20 after passing through the first facing position A. The film forming sheet 131 attached to the outer peripheral surface 21 of the second roll 20 is conveyed by the rotation of the second roll 20 and reaches the second facing position B.

The current collector foil 110 is passed through the second facing position B. Therefore, the film formation sheet 131 that has reached the second facing position B by the rotation of the second roll 20 passes through the gap GB at the second facing position B together with the collector foil 110. When passing through the gap GB, the collector foil 110 and the film-forming sheet 131 are pressed by the second roll 20 and the third roll 30 in the thickness direction.

Even at the second facing position B, the pressed film forming sheet 131 has the faster moving speed at the second facing position B, of the outer peripheral surface 21 of the second roll 20 and the first surface 111 of the current collector foil 110. Adhere to. As described above, in the third roll 30 of the wet powder film forming apparatus 1, the moving speed of the first surface 111 of the current collector foil 110 at the second facing position B is higher than the peripheral speed of the second roll 20. It is rotating at a faster peripheral speed. Therefore, the film-forming sheet 131 that has passed the second facing position B is transferred from the outer peripheral surface 21 of the second roll 20 onto the first surface 111 of the current collector foil 110.

Therefore, as shown in FIG. 2, the electrode mixture layer 120 is formed on the first surface 111 of the current collector foil 110 after passing through the second facing position B. Then, in the wet powder film forming apparatus 1, by continuously rotating the first roll 10, the second roll 20, and the third roll 30, the film forming sheet 131 is formed and the film forming sheet 131 is collected. Transfer to the foil 110 is continuously performed. Therefore, the electrode plate 100 having a long length in the transport direction of the collector foil 110 is manufactured. The electrode plate 100 is appropriately cut into an appropriate size when it is used for manufacturing a battery.

Here, the wet granulated material 130 of this embodiment will be described with reference to FIG. The wet granulated material 130 is a material for forming the electrode mixture layer 120, as described above. Therefore, the active material 121, the binder 122, and the surfactant 124 contained in the electrode mixture layer 120 are used for manufacturing the wet granulated product 130. Then, in the present embodiment, as shown in FIG. 3, the wet granulated material 130 is obtained by performing the first stirring step and the second stirring step of stirring these materials together with the solvent 123.

Further, in the present embodiment, before the first stirring step, the mixing step of mixing the active material 121 and the binder 122 is performed in advance. This mixing step is performed dry without adding the solvent 123 or the like. That is, in the mixing step, the powder of the active material 121 and the powder of the binder 122 are mixed to obtain these mixed powders. In this way, by performing the dry mixing process in advance, it is possible to finally obtain the wet granulated product 130 in which the particles of the active material 121 and the particles of the binder 122 are better distributed.

Next, in the first stirring step after the mixing step, the solvent 123 is added to the mixed powder of the active material 121 and the binder 122, and the mixture is stirred. Further, the amount of the solvent 123 added in the first stirring step is not the entire amount of the solvent 123 in the final wet granulated product 130, but a part thereof. Then, by the first stirring step, a mixture in which the solvent 123 is mixed with the mixed powder of the active material 121 and the binder 122 is obtained.

Subsequently, in the second stirring step, the solvent 123 and the surfactant 124 are added to the mixture obtained in the first stirring step and the mixture is stirred. The final amount of the solvent 123 of the wet granulated product 130 is adjusted by the amount of the solvent 123 added in the second stirring step. That is, by adding the amount of the solvent 123 added in the second stirring process to the amount of the solvent 123 already added in the first stirring process, the final amount of the solvent 123 in the wet granulated product 130 is obtained.

In addition, in the second stirring step of this embodiment, the surfactant 124 is added together with the solvent 123. In this embodiment, the surfactant 124 is added in a state of being dissolved in the solvent 123. However, for example, the surfactant 124 may be added as a powder different from the solvent 123. Moreover, in this embodiment, specifically, polyvinyl alcohol (PVA) is used as the surfactant 124.

Then, in the second stirring step, the rotation speed of the stirring blade that stirs the mixture is slower than in the first stirring step, and stirring is performed. Then, by the second stirring step, the particles of each material such as the active material 121 are adhered to each other by the solvent 123 to form a larger mass than the original particles. As a result, the wet granulated product 130 is formed.

As described above, in this embodiment, the wet granulation product 130 is formed by adding the surfactant 124. In this embodiment, the surfactant 124 is added to adjust the contact angle of the active material 121 with respect to the solvent 123.

In general, the active material 121 is a main component that constitutes the electrode mixture layer 120, and is a material that occupies most of it. When the contact angle of the active material 121 with respect to the solvent 123 is too small, the solvent 123 exists only on the surface of the particles of the active material 121, and the material forming the electrode mixture layer 120 (mainly the active material 121 The amount of the solvent 123 existing between the particles of 1) will be insufficient. On the other hand, if the contact angle of the active material 121 with respect to the solvent 123 is too large, the contact area between the active material 121 and the solvent 123 will be small.

That is, even if the contact angle of the active material 121 with respect to the solvent 123 is too small or too large, the liquid crosslinking force of the solvent 123 for adhering the particles of the material forming the electrode mixture layer 120 to each other will be insufficient. Becomes That is, for example, the film forming sheet 131 formed at the first facing position A of the wet powder film forming apparatus 1 may become brittle. Therefore, for example, a film-forming sheet 131 formed at the first facing position A and having one surface attached to the outer peripheral surface 11 of the first roll 10 and the other surface attached to the outer peripheral surface 21 of the second roll 20. However, there is a risk that the first roll 10 may not be properly peeled off and may be torn at an intermediate position in the thickness direction. As a result, a part of the film forming sheet 131 to be formed on the outer peripheral surface 21 of the second roll 20 may remain on the outer peripheral surface 11 of the first roll 10.

On the other hand, in the present embodiment, by adding the surfactant 124, the solvent that acts on the contact angle between the solvent 123 and the active material 121 between the particles of the material forming the electrode mixture layer 120 The liquid crosslinking force of 123 can be made sufficient. Specifically, in the present embodiment, the weight ratio of the solvent 123 and the surfactant 124 in the wet granulated material 130 is set so that the contact angle of the active material 121 with respect to the mixed liquid in which the solvent 123 and the surfactant 124 are mixed. , 10° or more and 80° or less. The weight of the solvent 123 in the wet granulated product 130 is the total weight of the weight of the solvent 123 added in the first stirring step and the weight of the solvent 123 added in the second stirring step.

By adding the surfactant 124 in such a ratio, in this embodiment, the liquid crosslinking force of the solvent 123 can be made sufficient. Thereby, the film forming sheet 131 can be appropriately formed on the outer peripheral surface 21 of the second roll 20. Further, also at the second facing position B of the wet powder film forming apparatus 1, the film forming sheet 131 is not left on the outer peripheral surface 21 of the second roll 20 and is appropriately placed on the first surface 111 of the collector foil 110. Can be transferred to.

The active material 121 is powder. Therefore, in the present embodiment, the contact angle of the active material 121 with respect to the mixed liquid obtained by mixing the solvent 123 and the surfactant 124 was measured as follows. FIG. 4 is a diagram showing a method of measuring the contact angle in this embodiment. FIG. 4 shows the pellet 140 and the mixed liquid 141 dropped on the surface of the pellet 140. The mixed liquid 141 is a mixture of the solvent 123 and the surfactant 124 as described above. The contact angle θ is shown by the angle between the mixed liquid 141 and the surface of the pellet 140, as shown in FIG.

The pellet 140 is formed of the active material 121. Specifically, the pellet 140 is formed by applying a compressive load to the powder of the active material 121 to solidify it. In the present embodiment, the powder of the active material 121, which is hardened by applying a load of 12 kN, is used as the pellet 140, and the mixed liquid 141 is dropped on the surface thereof to measure the contact angle θ.

Further, in this embodiment, the surfactant 124 is added in the second stirring step. If the surfactant 124 is added in the first stirring step, that is, before the binder 122 is sufficiently dissolved in the solvent 123, the solubility of the binder 122 may decrease. When the surfactant 124 is added in the first stirring step, the solvent 123 tends to wet the active material 121 at that time. Therefore, a large amount of the solvent 123 is present on the surface of the active material 121, and the solvent 123 that dissolves the binder 122 is insufficient. For this reason, the wet granulated material 130 in which the binder 122 is appropriately distributed may not be formed.

To solve such a problem, in the present embodiment, the binder 122 is appropriately dissolved in the solvent 123 in the first stirring step, and the surfactant 124 is added in the subsequent second stirring step. Therefore, in this embodiment, the wet granulated material 130 in which the binder 122 is favorably distributed can be formed.

Further, in the present embodiment, the wet granulation product 130 is formed so that the weight ratio of the solid content to the total weight is within the range of 63% or more and 92% or less. The total weight is the weight obtained by adding the weight of the solvent 123 to the weight of the solid content of the active material 121 and the like. If the ratio of the weight of the solid content to the total weight is too low, the amount of the solvent 123 is too large, so that the wet granulation product 130 cannot be properly formed by stirring. On the other hand, if the ratio of the weight of the solid content to the total weight is too high, a solid particle group that does not contain the solvent 123 is formed, and a part of the particles remains as a powder.

That is, if the ratio of the weight of the solid content to the total weight is too low or too high, the wet granulation product 130 cannot be properly formed. On the other hand, in the present embodiment, since the weight ratio of the solid content to the total weight is formed within the above range, the wet granulated product 130 can be appropriately formed.

As described above, in this embodiment, the wet granulation product 130 is formed by adding the surfactant 124 in the second stirring step. Further, the wet granulation product 130 is formed such that the contact angle of the mixed liquid 141 of the solvent 123 and the surfactant 124 with respect to the active material 121 and the weight ratio of the solid content to the total weight are within the above ranges. .. Then, by using the wet granulated material 130 formed in this way, the electrode mixture layer 120 having a uniform thickness can be formed. Thereby, a high quality electrode plate 100 can be manufactured.

Further, in the present embodiment, the liquid crosslinking force of the solvent 123 acting between the particles of the material forming the electrode mixture layer 120 can be made sufficient. Therefore, even if the rotation speed of each roll of the wet powder film formation apparatus 1 is increased, the film formation sheet 131 on the second roll 20 and the electrode mixture layer 120 on the current collector foil 110 are appropriately formed. .. That is, in this embodiment, the high quality electrode plate 100 can be manufactured in a shorter time.

Next, examples of this embodiment will be described together with comparative examples. In each of the examples and the comparative examples, electrode plates were produced using the wet powder film forming apparatus shown in FIG. In each of the examples and the comparative examples, wet granulation products were formed using the same ingredients as the active material, the binder, the solvent, and the surfactant, using a stirring granulator manufactured by Rix Co. did. Further, in each of the examples and comparative examples, the ratio of the active material, the binder and the surfactant was set to 98.6:1:0.4. That is, in Examples and Comparative Examples, the ratio of the active material in the electrode mixture layer is higher than that of the other materials.

However, in each of the examples and the comparative examples, the step of adding the surfactant, the contact angle of the active material with respect to the mixed solution of the solvent and the surfactant, and the ratio of the weight of the solid content to the total weight are set as different conditions. A granulate was formed. The forming conditions are summarized in Table 1 below.

As shown in Table 1, all of Examples 1 to 9 according to the present embodiment include a step of adding a surfactant, a contact angle of an active material with respect to a mixed solution of a solvent and a surfactant, and a solid content in the total weight. The wet granulated product is used in which the weight ratio of each minute (solid content) is as in the present embodiment. On the other hand, in Comparative Examples 1 to 5, at least one condition among the step of adding the surfactant, the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant, and the solid content ratio is the present embodiment. Different from the conditions.

Specifically, in Comparative Example 1, the surfactant is added in the first stirring step. In Comparative Example 2, the surfactant was added in the first stirring step, and the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant was 5°, which was less than 10°. In Comparative Example 3, the surfactant was added in the first stirring step, and the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant was 85°, which exceeded 80°. In Comparative Example 4, the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant is 5°, which is less than 10°. In Comparative Example 5, the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant is 85°, which exceeds 80°.

Table 1 shows the evaluation items for Examples 1-9 and Comparative Examples 1-5. This evaluation is an evaluation regarding the quality of the electrode mixture layer of the electrode plates produced in Examples 1 to 9 and Comparative Examples 1 to 5, respectively. Specifically, the electrode mixture layer formed on the surface of the current collector foil was observed, and those having a uniform thickness and high quality electrode mixture layer were evaluated as "○". .. On the other hand, when the thickness of the electrode mixture layer is not uniform and, for example, there is a defective portion such that the current collector foil is exposed in the range where the electrode mixture layer is to be formed, the evaluation is “ “X” is shown. In addition, although there is no obvious defect such as the one evaluated as "x", the evaluation is made for the one in which the thickness of the electrode mixture layer is inferior to the one evaluated as "○". It is shown as “Δ”.

As shown in Table 1, all of Examples 1 to 9 were evaluated as “◯” or “Δ”, and Comparative Examples 1 to 5 were evaluated as “x”. That is, in Examples 1 to 9, the electrode mixture layer of sufficient quality was formed. On the other hand, in each of Comparative Examples 1 to 5, an electrode mixture layer having a defective portion and having an insufficient quality was formed.

First, in Comparative Examples 1 to 3 in which the surfactant was added in the first stirring step, the wet granulation product in which the binder was appropriately distributed could not be formed, and therefore the film formation in the wet powder film forming apparatus was good. Has not been done to. Further, in Comparative Examples 2 and 4 in which the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant is small, the amount of the solvent existing between the particles of the material forming the electrode mixture layer is insufficient. .. Further, in Comparative Examples 3 and 5 in which the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant is large, the contact area between the particles of the active material and the solvent is insufficient. That is, in each of Comparative Examples 2 to 5, the liquid crosslinking force of the solvent acting between the particles of the material forming the electrode mixture layer is insufficient.

That is, in each of Comparative Examples 1 to 5, at least one of the step of adding the surfactant, the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant, and the solid content ratio is the same as the present embodiment. Since the conditions were different, it was not possible to form an electrode mixture layer with a uniform thickness. On the other hand, in Examples 1 to 9 in which the step of adding the surfactant, the contact angle of the active material with respect to the mixed liquid of the solvent and the surfactant, and the solid content are all satisfied with the conditions of the present embodiment, the thickness is uniform. It was confirmed that a different electrode mixture layer could be formed.

In addition, among Examples 1 to 9, the evaluation was “Δ” in Example 6 in which the solid content ratio was 63%, whereas the evaluation was “◯” in Example 7 in which the solid content ratio was 65%. Is. Further, in Example 9 in which the solid content ratio is 92%, the evaluation is “Δ”, whereas in Example 8 in which the solid content ratio is 90%, the evaluation is “◯”. That is, it was confirmed that it is more preferable to regulate the wet granulated product by setting the solid content ratio to 65% or more and 90% or less.

As described above in detail, in the present embodiment, the wet granulation product is formed into a sheet-shaped film-forming sheet by passing through the gap between the first roll and the second roll, and this is used as a collector foil. It is attached to the first surface by transfer. Thereby, the electrode mixture layer is formed on the current collector foil to manufacture the electrode plate. The wet granulation product includes a first stirring step of mixing an active material and a binder with a solvent by stirring to obtain a mixture thereof, and a second stirring step of mixing the mixture with a solvent and a surfactant by stirring. It is formed by and. In that case, the weight ratio of the solvent and the surfactant in the wet granulation is such that the contact angle of the active material with respect to the mixed solution of the solvent and the surfactant is in the range of 10° or more and 80° or less. The ratio is Further, the wet granulation product is formed such that the ratio of the weight of the solid content to the total weight is within the range of 63% or more and 92% or less. As a result, a wet powder film forming method capable of forming an electrode mixture layer having a uniform thickness on the collector foil by the wet granulation product is realized.

In addition, the wet granulation product, which is an intermediate formed by the wet powder film forming method of the present embodiment, contains a surfactant. Further, the weight ratio of the solvent and the surfactant is such that the contact angle of the active material with respect to the mixed liquid in which the solvent and the surfactant are mixed is within the range of 10° or more and 80° or less. Furthermore, the ratio of the weight of the solid content excluding the solvent to the total weight is within the range of 63% or more and 92% or less. Further, in the above wet powder film forming method, by using this wet granulated product, it is possible to form the electrode mixture layer having a uniform thickness on the current collector foil.

The present embodiment is merely an example and does not limit the present invention. Therefore, naturally, the present invention can be variously improved and modified without departing from the scope of the invention. For example, in the above embodiment, the case where the electrode mixture layer is formed only on the first surface of the current collector foil has been described, but the electrode mixture layer can be formed on the second surface of the current collector foil. The formation of the electrode mixture layer on the second surface of the current collector foil can be performed in the same manner as in the case of forming it on the first surface described in the above embodiment.

Further, for example, the electrode mixture layer may contain a material such as a conductive material in addition to the active material and the binder. Even in this case, the ratio of the active material in the electrode mixture layer is higher than that of the other materials. Therefore, for example, even when the electrode mixture layer contains a conductive material such as acetylene black (AB), the present invention can be applied. In this case, the conductive material may be added before the second stirring step (for example, a dry mixing step).

Further, the specific materials shown in the above embodiments are merely examples, and naturally, other materials can be used. That is, for example, the active material 121 is replaced by NMC (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) which is a ternary positive electrode active material, and other materials such as spinel type LiMn ₂ O ₄ are used. It is also possible to use one. Further, for example, the present invention can be applied not only to the electrode plate of the lithium ion secondary battery but also to the electrode plates of other batteries.

Further, for example, in the above, an example in which PVA is used as a surfactant has been described. However, it is also possible to use other surfactants.

1 Wet Powder Film Forming Apparatus 10 First Roll 20 Second Roll 30 Third Roll 100 Electrode Plate 110 Current Collecting Foil 120 Electrode Mixture Layer 121 Active Material 122 Binder 123 Solvent 124 Surfactant 130 Wet Granulated Material A First facing position B Second facing position

Claims (1)

The wet granulation product formed by mixing the solvent with at least the active material and the binder is passed through the gap of the roll pair to be formed into a sheet and adhered on the current collection foil. In a wet powder film forming method for forming an electrode mixture layer on
The wet granulation product is
A first stirring step of mixing the active material and the binder with the solvent by stirring to obtain a mixture thereof;
Forming the mixture by a second stirring step of mixing the solvent and surfactant with stirring, and
The weight ratio of the solvent and the surfactant in the wet granulated product is such that the contact angle of the active material with respect to the mixed liquid obtained by mixing the solvent and the surfactant is in the range of 10° or more and 80° or less. And the ratio is
A method for forming a wet powder film, characterized in that the ratio of the weight of the solid content to the total weight of the wet granulation product is within the range of 63% or more and 92% or less.

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