JP2013084525A - Manufacturing method for secondary battery electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a secondary battery electrode, with the method a preparation of a composition for forming an electrode active material layer being able to be performed simply by properly managing a conductive material.SOLUTION: A paste-like carbon composition for forming an electrode active material layer is to be used in accordance with the following determination processing. (1) A particle size distribution of the composition shows a bimodal distribution with a first peak composed of particles having relatively small diameter and a second peak composed of particles having relatively greater diameter. The ratio of an abundance ratio H1(%) at the first peak to an abundance ratio H2(%) at the second peak satisfies (H1/H2)>1. (2) A viscosity coefficient η of the composition for forming the electrode active material layer corresponding to a standard deviation σ of the particle size distribution is to be included in a predetermined acceptable viscosity range, the viscosity coefficient η is calculated, according to the standard deviation σ of the particle size distribution, by a correlation equation between a measured standard deviation of the particle size distribution of a plurality of paste-like carbon compositions from different manufacturing lots and a viscosity coefficient of compositions for forming the electrode active material layer in a same kind, the compositions being made beforehand by each using the paste-like carbon composition in advance.

Description

  The present invention relates to a method for manufacturing a secondary battery electrode. In detail, it is related with preparation of the composition for electrode active material layer forming containing a electrically conductive material.

In recent years, lithium secondary batteries (typically lithium ion batteries) that are lightweight and have a high energy density have become increasingly important as high-output power supplies for vehicles.
In one typical configuration of this type of secondary battery, an electrode material (electrode active material layer) containing an electrode active material capable of reversibly occluding and releasing lithium ions serving as charge carriers is used as a conductive member (electrode assembly). The electrode is held on the electric body. This electrode typically has a paste form (slurry form) by first dispersing an electrode active material, a highly conductive conductive material, and a solid material such as a binder (binder) in an appropriate solvent. A composition for forming an electrode active material layer including the ink form, the same applies hereinafter) is prepared, and this composition is applied in a layer form on the surface of the electrode current collector. Next, the applied composition is dried to remove the solvent, and the electrode active material layer containing the electrode active material and the conductive material is formed on the electrode current collector (application method).

  In the production of such an electrode for a secondary battery, carbon black is frequently used as the conductive material because of its conductive characteristics and good handleability. Such carbon black may be handled as a pasty carbon composition (so-called carbon paste) in which a granular carbon material is dispersed in a solvent together with a binder and a dispersant. Originally, this pasty carbon composition has been widely used in the fields of paints and inks, but in recent years, it has been re-prepared for battery applications.

By the way, various proposals have been made regarding the management method of electrode materials such as electrode active materials and conductive materials. For example, Patent Document 1 discloses that, in the production of a primary alkaline battery, the oxidation-resistant graphite as a conductive material is managed by the total ash content, the BET specific surface area, the average particle size by laser diffraction, and the crystal structure. .
In Patent Document 2, the variation in the composition of the transition metal composite oxide containing lithium and nickel as the electrode active material is used as an index of the ratio of the third root of the light emission voltage caused by each element of lithium and nickel. The management using the standard deviation σ is disclosed.
In Patent Document 3, in the management of the crystal structure of the composite carbonaceous material as the negative electrode active material, the half-value width in the X-ray diffraction diagram is ± 3σ of the half-value width in the X-ray diffraction diagram of the graphitic carbonaceous material used for the nucleus. It is disclosed that σ is within a standard deviation).
Patent Document 4 discloses that the crystal structure of graphite particles as a negative electrode active material is managed by the interlayer distance in the thickness direction of crystals and the size of crystallites in the thickness direction in X-ray wide angle diffraction.
Patent Document 5 discloses that a carbon microsphere powder as a negative electrode active material has an arithmetic average primary particle diameter dn measured by an electron microscope and a half-value width ΔDst relative to a Stokes mode diameter Dst measured by a disk centrifuging device (DCF). And management based on the crystallite lattice spacing d (002) measured by the ratio, X-ray diffraction method, and the like.

Special table 2008-502121 gazette JP 2008-243447 A Japanese Patent No. 3712288 Japanese Patent Application No. 11-011919 JP 2009-176603 A

All of the above electrode material management methods are implemented for the purpose of improving the electrode performance, and are not managed from the viewpoint of increasing the efficiency of electrode production.
Regarding the manufacture of such an electrode, the manufacturing method may become complicated due to variations in the electrode material used as a product. Specifically, for example, in the preparation of the composition for forming an electrode active material layer, the viscosity of the resulting composition may vary greatly even if the same electrode material is used and the composition is the same. It was. Therefore, in the process of preparing the composition for forming an electrode active material layer, the viscosity of the kneaded product is measured while the electrode material is dispersed and kneaded in a solvent, and the viscosity is adjusted to be within the target viscosity range. Was often accompanied. Further, since the viscosity of the composition directly affects the coating property, it is considered that the coating property (typically, coating width stability) is affected by a slight difference in viscosity of the composition.

  The present invention was created in view of the conventional situation, and the object of the present invention is to easily prepare a composition for forming an electrode active material layer containing a conductive material with stable quality. It is providing the manufacturing method of the electrode for secondary batteries which can be performed.

  As a result of intensive studies on the cause of variation in viscosity of the composition for forming an electrode active material layer, the present inventors have found that this is due to variation in the quality of the pasty carbon composition used as the conductive material. I found it. For example, FIG. 12 shows the viscosity of an electrode active material layer forming composition prepared with the same composition using electrode materials of the same standard for each batch (prepared once). The vertical dotted line in FIG. 12 indicates the timing when the production lot of the pasty carbon composition (product) used as the material is switched. As shown in FIG. 12, the viscosity of the electrode active material layer forming composition may greatly depend on the quality variation of each production lot of the pasty carbon composition, although there is some variation for each batch. It is clear.

  Therefore, the present inventors investigated which factor of the paste-like carbon composition contributes to the quality variation of the paste-like carbon composition that affects the viscosity of the electrode active material layer forming composition. For example, a pasty carbon composition as a product is managed based on a conventional management method for paint applications. The management items are viscosity and moisture. Therefore, the relationship between the physical properties of the pasty carbon composition and the viscosity of the electrode active material layer forming composition obtained using the pasty carbon composition has been organized focusing on the viscosity and moisture of the pasty carbon composition. FIG. 13 shows the relationship between the viscosity of the paste-like carbon composition and the viscosity of the electrode active material layer forming composition (positive electrode paste) obtained using the paste-like carbon composition. FIG. 14 shows the relationship between the moisture content of the pasty carbon composition and the viscosity of the electrode active material layer forming composition (positive electrode paste) obtained using the paste. From FIG. 13 and FIG. 14, there is a correlation between the viscosity or water content of the pasty carbon composition and the variation in the viscosity of the composition for forming an electrode active material layer obtained by using this. Absent.

  As a result of further research, the present inventors found that the dispersion in the quality of the paste-like carbon composition that affects the viscosity of the composition for forming an electrode active material layer is caused by the carbon particles in the paste-like carbon composition. It came to the conclusion that it originated from the dispersion | variation in the dispersion state. The present invention stabilizes the viscosity of the composition for forming an electrode active material layer by accurately managing the paste-like carbon composition based on these findings, and can easily produce a high-quality secondary battery electrode. A method of manufacturing is realized.

That is, the present invention is a method for producing an electrode for a secondary battery in which an electrode active material layer mainly composed of an electrode active material is formed on an electrode current collector,
(A) a step of preparing a pasty carbon composition containing a granular carbon material as a conductive material, a binder, and a solvent;
(B) a step of preparing a paste-like electrode active material layer forming composition containing the paste-like carbon composition, an electrode active material, a binder, and a solvent; and
(C) supplying the electrode active material layer forming composition onto an electrode current collector, and forming an electrode active material layer on the current collector;
Is included.

Here, the paste-like carbon composition used to prepare the composition for forming an electrode active material layer in the step (B) has a laser particle size distribution of the composition prepared in the step (A). It measures based on the diffraction method, and comprises all the following determination processes (1)-(2) performed based on the measured result.
(1) The particle size distribution indicates a bimodal distribution having a first peak (P1) having a relatively small particle size and a second peak (P2) having a relatively large particle size in the particle size distribution. The ratio of the volume-based abundance ratio H1 (%) in the first peak and the volume-based abundance ratio H2 (%) in the second peak satisfies (H1 / H2)> 1.

  (2) Based on the standard deviation σ in the measured particle size distribution, the standard deviation in the particle size distribution measured for the plurality of paste-like carbon compositions in different production lots, and the paste-like carbon composition were used in advance. From the correlation equation with the viscosity measured for the same kind of electrode active material layer forming composition, the viscosity of the electrode active material layer forming composition corresponding to the standard deviation σ of the paste-like carbon composition to be judged is calculated. The calculated viscosity is included in a predetermined acceptable viscosity range.

  This makes it possible to reliably prepare an electrode active material layer forming composition having a viscosity in the acceptable viscosity range. As a result, preparation and management of the composition for forming an electrode active material layer are facilitated, and an electrode with high yield and quality can be produced.

  In a preferred embodiment of the method for producing an electrode for a secondary battery disclosed herein, the granular carbon material contained in the pasty carbon composition has an average secondary particle diameter in the range of 200 nm to 10 μm. It is characterized by being. Thereby, the quality of the paste-like carbon composition becomes more stable, and it becomes possible to manufacture the electrode more easily.

  In a preferred embodiment of the method for producing an electrode for a secondary battery disclosed herein, the pasty carbon composition used for preparing the electrode active material layer forming composition in the step (B), The first peak (P1) in the particle size distribution is at a particle size of less than 1 μm, and the second peak (P2) is at a particle size of 1 μm or more. A composition for forming an electrode active material layer is obtained by combining the particle size of the particle group forming the first peak (P1) and the particle size of the particle group forming the second peak (P2) in such a combination. The quality of the object is stabilized, and the resistance of the obtained electrode can be reduced.

  In a preferred aspect of the method for producing an electrode for a secondary battery disclosed herein, the granular carbon material is carbon black having an average particle diameter based on a laser diffraction method of primary particles of 100 nm or less. This also stabilizes the quality of the composition for forming an electrode active material layer and enables accurate management of the paste-like carbon composition.

  The manufacturing method of the electrode for secondary batteries disclosed here is implemented in order to manufacture the positive electrode of a lithium ion secondary battery using the material which comprises the positive electrode active material of a lithium ion secondary battery as said electrode active material. Preferably it is done. Thereby, it becomes possible to manufacture the positive electrode of a lithium ion secondary battery with simpler and more stable quality.

  In the method for producing an electrode for a secondary battery disclosed herein, as described above, since the quality of the composition for forming an electrode active material layer is prepared in a stable state, the quality of the electrode naturally obtained is also stable. obtain. Therefore, the secondary battery provided with this electrode can also have high quality and stable battery characteristics.

It is a particle size distribution figure which shows an example of the particle size distribution of the carbon material contained in a paste-form carbon composition. It is a particle size distribution figure which shows another example of the particle size distribution of the carbon material contained in a paste-form carbon composition. It is a figure which shows an example of the relationship between the standard deviation regarding the particle size distribution of a carbon material, and the viscosity of the composition for electrode active material layer formation (positive electrode paste) prepared using this carbon material. It is a flowchart which shows a part of manufacturing process of the electrode which concerns on one Embodiment. It is a flowchart which shows another part of manufacturing process of the electrode which concerns on one Embodiment. It is a perspective view which shows the lithium secondary battery provided with the electrode which concerns on one Embodiment. It is a longitudinal cross-sectional view which follows the VII-VII line in FIG. It is a side view showing typically a vehicle provided with an electrode concerning one embodiment. It is a particle size distribution figure which shows the particle size distribution of the carbon material contained in the paste-form carbon composition of a different manufacturing batch. It is a figure which shows the viscosity of the composition for positive electrode active material layer formation (positive electrode paste) using the paste-form carbon composition of a different manufacturing batch. It is a figure which shows the relationship between the standard deviation regarding the particle size distribution of a carbon material, and the viscosity of the composition for positive electrode active material layer formation (positive electrode paste). It is the figure which showed the viscosity of the composition for positive electrode active material layer formation (positive electrode paste) for every batch. It is a figure which shows the relationship between the viscosity of a paste-form carbon composition (carbon paste), and the viscosity of the composition for electrode active material layer formation (positive electrode paste) obtained using this. It is a figure which shows the relationship between the moisture content of a paste-like carbon composition (carbon paste), and the viscosity of the composition for electrode active material layer formation (positive electrode paste) obtained using this.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

In the present specification, the “secondary battery” refers to general power storage devices that can be repeatedly charged, such as a lithium secondary battery and a nickel-metal hydride battery. In the present specification, the “lithium secondary battery” means a general battery that can be repeatedly charged using lithium ions as a charge carrier, and typically includes a lithium ion battery, a lithium polymer battery, a lithium capacitor, and the like.
Further, in this specification, the “active material” can reversibly occlude and release (typically insertion and removal) chemical species (for example, lithium ions in a lithium ion battery) that become charge carriers in a secondary battery. A substance.

The method for manufacturing a secondary battery electrode disclosed herein is a method for manufacturing a secondary battery electrode in which an electrode active material layer mainly composed of an electrode active material is formed on an electrode current collector. The following steps (A) to (C) are included.
(A) The process of preparing the paste-form carbon composition containing the granular carbon material which is a electrically conductive material, a binder, and a solvent.
(B) The process of preparing the paste-form electrode active material layer forming composition containing the said paste-form carbon composition, an electrode active material, a binder, and a solvent.
(C) The process of supplying the said electrode active material layer formation composition on an electrode electrical power collector, and forming an electrode active material layer on this electrical power collector.

  The pasty carbon composition prepared in the step (A) may be prepared by dispersing a granular carbon material and a binder in a solvent, or a pasty carbon composition (so-called carbon paste) prepared in advance. ) May be used as generally provided (sold). Then, using this pasty carbon composition, a paste-like electrode active material layer forming composition is prepared in step (B), and in step (C), an electrode active material layer is formed on the current collector.

≪Determination of pasty carbon composition≫
In such a manufacturing method, it is determined whether or not the paste-like carbon composition prepared in the step (A) is suitable for use in preparing the electrode active material layer forming composition in the step (B). . In this determination, the particle size distribution of the pasty carbon composition prepared in the step (A) is measured based on the laser diffraction method, and based on the result, the following determination processes (1) to (2) are all included. In this case, it is determined that the pasty carbon composition is suitable for use in the preparation of the electrode active material layer forming composition. If any one of the determination processes (1) to (2) is not satisfied, it is determined that the pasty carbon composition is not suitable for use in the preparation of the electrode active material layer forming composition.

Determination process (1): The particle size distribution is a bimodal distribution having a first peak (P1) having a relatively small particle diameter and a second peak (P2) having a relatively large particle diameter. The ratio of the volume-based abundance ratio H1 (%) in the first peak and the volume-based abundance ratio H2 (%) in the second peak satisfies (H1 / H2)> 1.
Judgment process (2): Based on the standard deviation σ in the measured particle size distribution, the standard deviation in the particle size distribution measured for a plurality of pasty carbon compositions in different production lots, and the pasty carbon composition in advance. From the correlation equation with the viscosity measured for the same kind of composition for forming an electrode active material layer, the viscosity of the composition for electrode active material layer formation corresponding to the standard deviation σ of the pasty carbon composition to be judged And the calculated viscosity is included in a predetermined acceptable viscosity range.

  The particle size distribution can be measured using various particle size distribution measuring devices based on the principle of the laser diffraction method. In addition, the value calculated based on a volume standard shall be employ | adopted for the particle size and abundance ratio (%) (or frequency) in a particle size distribution.

<< Judgment process (1) >>
This determination process (1) focuses on the particle size distribution of the pasty carbon composition to be determined (that is, the particle size distribution of the carbon material contained in the pasty carbon composition). That is, the measured particle size distribution is assumed to exhibit a bimodal distribution having a first peak (P1) having a relatively small particle size and a second peak (P2) having a relatively large particle size. This is typically a mixture of a first carbon particle (particle group) having a relatively small particle size and a second carbon particle (particle group) having a relatively large particle size. I can understand.

  FIG. 1 shows an example of a bimodal particle size distribution. For example, for the sake of easy understanding, the average particle diameter of the first carbon particles is defined as a first particle diameter value D1, and the average particle diameter of the second carbon particles is defined as a second particle diameter value D2. The first carbon particles and the second carbon particles may have substantially the same particle size (that is, substantially monodisperse), but usually exist as a particle group having a certain distribution width. Therefore, the particle size distribution of such a carbon material is typically a bimodal particle size distribution. That is, for example, the particle size distribution formed by the first carbon particles having the peak P1 at the first particle size value D1 and the particle size distribution formed by the second carbon particles having the peak P2 at the second particle size value D2. It is confirmed. The frequency (existence ratio) at the peak P1 of the particle size distribution is H1, and the frequency (existence ratio) at the peak P2 is H2. Depending on the value of the first particle size value D1 and the second particle size value D2 and the form of the particle size distributions P1 and P2, for example, as shown in FIG. 2, the particle size distribution related to the first carbon particles and the second carbon There may be a case where the particle size distribution relating to the particles partially overlaps.

  In such a bimodal particle size distribution, the abundance ratio H1 (%) related to the particle size distribution of the first carbon particles is compared with the abundance ratio H2 (%) related to the second carbon particles, and the ratio (H1 / H2) of both is compared. ) Is greater than 1. That is, it is confirmed whether the frequency H1 at the peak P1 of the first carbon particle having a relatively small particle diameter is higher than the frequency H2 at the peak P2 of the second carbon particle having a relatively large particle diameter.

<Judgment>
When the ratio is (H1 / H2)> 1, it is determined that the determination process (1) is satisfied. That is, the determination process (1) is satisfied when the volume of the first carbon particles at the peak P1 is larger than the volume of the second carbon particles at the peak P2.
If the abundance ratio H1 is higher than the abundance ratio H2, the number of first carbon particles having a relatively small particle size increases, and therefore, a conductive path (conducting property) is preferably filled by filling the gap between the second carbon particles having a relatively large particle size. Pass), and the resistance of the electrode can be kept small, which is preferable. On the other hand, if the abundance ratio H1 is equal to or less than the abundance ratio H2, the number of second carbon particles having a relatively large particle size increases, making it difficult to ensure a sufficient conduction path (conduction path). This is not preferable because the conductivity of the electrode tends to decrease. In addition, the effect of mixing the first carbon particles having a relatively small particle size and the second carbon particles having a relatively large particle size is not sufficiently exhibited. Therefore, the ratio of the abundance ratio H1 at the peak P1 of the particle size distribution to the abundance ratio H2 at the peak P2 is defined as (H1 / H2)> 1.
In addition, when the particle size distribution of the paste-like carbon composition to be determined is not a bimodal distribution, that is, when a unimodal distribution or a multimodal distribution of three or more peaks is exhibited, the determination process (1) is not satisfied. to decide.

<< Determination process (2) >>
In the determination process (2), first, the standard deviation σ is calculated from the particle size distribution of the pasty carbon composition to be determined. Next, from this standard deviation σ, the viscosity η of the electrode active material layer forming composition prepared using the paste-like carbon composition is calculated and predicted, and the calculated viscosity η is determined in advance. Judgment is made as to whether it falls within the viscosity range.

  As the standard deviation σ in the particle size distribution, a statistical standard deviation defined by the following equation can be used. However, in the production method disclosed herein, the standard deviation is not limited to this statistical standard deviation, and the particle diameter of the particles (secondary particles) constituting the carbon material contained in the paste-like carbon composition. As long as the degree of variation can be accurately expressed, a separately defined standard deviation may be used as appropriate.

  The standard deviation defined separately may be, for example, a standard deviation appropriately defined according to the measurement principle (processing content) of the particle size distribution measuring apparatus used for measuring the particle size distribution. That is, it can be said to be a standard deviation in a broad sense. Specifically, for example, standard deviations represented by the following formulas are exemplified.

  For the calculation of the viscosity η, the standard deviation (a) in the particle size distribution of the pasty carbon composition obtained in advance and the same kind of composition for forming an electrode active material layer prepared using this pasty carbon composition The correlation equation with the viscosity (b) measured for is used. That is, the correlation between the two is obtained in advance.

<Standard deviation (a)>
The standard deviation (a) is obtained by measuring in advance the particle size distribution of a paste-like carbon composition of the same type as the paste-like carbon composition to be judged (that is, the particle size distribution of the carbon material contained in the paste-like carbon composition). The particle size distribution can be obtained by calculation. A plurality of paste-like carbon compositions having different production lots (one unit of production) are prepared. This is because the standard deviation of the particle size distribution of the carbon material contained in the paste-like carbon composition is not so large in the same production lot, but may vary between different production lots. is there. Note that “plurality” means two or more, but is preferably four or more in order to increase the accuracy of the determination process. More preferably, it is 5 or more. In addition, when the number of pasty carbon compositions manufactured in one production lot is large (for example, 1000 or more), two or more pasty carbon compositions from the same lot are used by using a statistical method. You may make it extract a thing. Also in this case, a pasty carbon composition is prepared from a plurality of different production lots. The standard deviation can be calculated in the same manner as the standard deviation σ. The standard deviation (a) is a value based on the same definition formula as the standard deviation σ.

<Viscosity (b)>
The viscosity (b) of the electrode active material layer forming composition was measured for each of the electrode active material layer forming compositions prepared using the plurality of pasty carbon compositions for which the standard deviation (a) was calculated. I do. First, a viscosity is measured about the composition for electrode active material layer formation prepared by the predetermined | prescribed mixing | blending using the paste-form carbon composition with which the particle size distribution was measured. The viscosity can be measured using various known viscometers. As the viscometer, there are no particular limitations on the measurement principle and measuring instrument as long as the viscosity of the desired composition for forming an electrode active material layer and the viscosity range in the vicinity thereof can be measured correctly. For example, using a general-purpose viscoelasticity measuring device (rheometer), measuring the viscosity at 25 ° C. and a shear rate of 40 s ⁻¹ is exemplified. In addition, this viscosity can be accurately measured by using, for example, a rotary rheometer (MCR301 or the like) manufactured by Anton Paar.

<Determination of correlation equation>
Next, the correlation between the standard deviation (a) and the viscosity (b) determined above is determined. Here, if an electrode active material layer forming composition is prepared with a predetermined composition using an electrode active material of the same type, an electrode material such as a granular carbon material and a binder, and a solvent, the standard deviation is usually used. There is a linear correlation between (a) and viscosity (b). FIG. 3 shows an example of the relationship between the standard deviation (a) regarding the particle size distribution of the carbon material contained in the pasty carbon composition and the viscosity (b) of the electrode active material layer forming composition (positive electrode paste). In the example shown in FIG. 3, it can be seen that there is a clear linear relationship represented by a linear expression with a high contribution rate. Therefore, by using this correlation equation, an electrode active material prepared using the standard deviation value regarding the particle size distribution of the pasty carbon composition prepared for use in preparing the composition for forming an electrode active material layer is used. The viscosity of the layer forming composition can be predicted.
In addition, when various conditions change, for example, when using paste carbon having different specifications (physical properties of materials used), or when changing the composition of the electrode active material layer forming composition, the standard is used. A correlation (correlation formula) between the deviation (a) and the viscosity (b) can be obtained separately.

<Judgment>
In the determination process (2), first, the viscosity η of the electrode active material layer forming composition to be prepared is calculated from the standard deviation σ in the particle size distribution of the pasty carbon composition to be determined using the above correlation equation. To do. When the calculated viscosity η is included in the predetermined acceptable viscosity range, it is determined that the determination process (2) is satisfied. The acceptable viscosity range can be determined as appropriate according to the performance of the target electrode. In a normal electrode manufacturing process, within a certain range, even if there is a deviation in the viscosity of the electrode active material layer forming composition, it is acceptable. The acceptable viscosity range of the composition for forming an electrode active material layer can be determined including the allowable range of deviation.

  This determination process (2) can be programmed in advance in, for example, analysis means connected to the particle size distribution measuring apparatus. Specifically, for example, the particle size distribution measurement of a plurality of pasty carbon compositions is performed in advance with a particle size distribution measuring device, and the results are sent to the analysis means to calculate and accumulate standard deviation (a) data. To do. Then, by inputting the viscosity (b) data of the composition for forming an electrode active material layer corresponding to the standard deviation (a) data into the analyzer, both the data of the standard deviation (a) and the data of the viscosity (b) The correlation (correlation formula) can be determined. Next, the particle size distribution of the paste-like carbon composition to be judged is measured with a particle size distribution measuring device, and the measurement data is sent to the analysis device. In addition to calculating the standard deviation σ, the viscosity η of the electrode active material layer forming composition prepared by automatically performing a calculation process from the standard deviation σ and the correlation equation is calculated. If this viscosity η is included in the predetermined acceptable viscosity range, a result indicating that the determination process (2) is satisfied is displayed.

Moreover, the value of standard deviation (sigma) of the particle size distribution of the paste-like carbon composition which can prepare the composition for electrode active material layer formation which has desired viscosity (eta) can also be determined. Further, the acceptable standard deviation range may be determined as the range of the standard deviation σ that can achieve the target viscosity.
By using the pasty carbon satisfying the determination process (1) and the determination process (2), in this manufacturing method, the viscosity η of the electrode active material layer forming composition after preparation is within a desired acceptable viscosity range. It controls to become. Therefore, the preparation of the electrode active material layer forming composition in the step (B) is facilitated, the work of adjusting the viscosity is unnecessary, or the work of adjusting the viscosity can be simplified. Moreover, the bad influence on the coating property (typically coating width stability) by the dispersion | variation in the viscosity of the composition for electrode active material layer formation can be suppressed.

  In addition, selection of the pasty carbon based on such judgment processing (1) and judgment processing (2) is not necessarily the case of manufacturing all the pasty carbon compositions prepared in the step (A) when manufacturing a normal electrode. There is no need to do it one by one. For example, when the pasty carbon composition prepared in step (A) is a product, one or two or more samples may be extracted and evaluated per production lot. Moreover, when preparing and preparing a paste-like carbon composition at (A) process, what is necessary is just to extract and evaluate one or two or more samples per manufacturing batch. Note that the number of samples to be extracted can be determined statistically by, for example, a sample extraction method.

  Therefore, in the step (A), when preparing a paste-like carbon composition, a granular carbon material having a particle size distribution satisfying the determination processes (1) to (2) is used, and this dispersed state is maintained. It is important to disperse the particulate carbon material and the binder in the solvent. Moreover, when using the paste-like carbon composition for electrodes provided as a product, it can be said that it is only necessary to confirm whether the particle size distribution of the carbon material satisfies the determination processes (1) to (2).

Hereinafter, as an embodiment of a method for producing an electrode for a secondary battery, the present invention will be described by taking the production of a positive electrode for a lithium secondary battery as an example. Hereinafter, after describing a typical configuration of the positive electrode, a manufacturing method will be described in detail.
≪Positive electrode structure≫
Here, as an embodiment of the secondary battery electrode manufactured by the manufacturing method disclosed herein, a positive electrode for a lithium secondary battery will be described as an example. Such a positive electrode usually has a configuration in which a positive electrode active material layer mainly composed of a positive electrode active material is formed on an electrode current collector. Below, the material etc. which are used for manufacture of a positive electrode are demonstrated.

<Positive electrode current collector>
As the positive electrode current collector, a conductive member made of a metal having good conductivity is used as in the case of the electrode current collector used for the positive electrode of a conventional non-aqueous electrolyte secondary battery (typically a lithium secondary battery). be able to. For example, a metal containing aluminum, nickel, titanium, iron, or the like as a main component or an alloy thereof can be used. More preferably, it is aluminum or an aluminum alloy. There is no restriction | limiting in particular about the shape of a positive electrode electrical power collector, Various things can be considered according to the shape etc. of a desired secondary battery. For example, it may be in various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape. Typically, a sheet-like aluminum positive electrode current collector is used.

<Positive electrode active material layer>
The positive electrode active material layer is formed on the surface of the positive electrode current collector. The positive electrode active material layer usually includes a granular positive electrode active material as a main component, and also includes a granular carbon material for enhancing conductivity, and these are solidified by a binder and fixed on the positive electrode current collector. .

<Positive electrode active material>
As the positive electrode active material, a material capable of inserting and extracting lithium is used, and one or more of various materials conventionally used in lithium secondary batteries can be used without particular limitation. As such a positive electrode active material, a lithium transition metal oxide (typically in particulate form) is preferably used. Typically, a layered structure oxide or a spinel structure oxide is appropriately selected and used. can do. For example, selected from a lithium nickel oxide (typically LiNiO ₂ ), a lithium cobalt oxide (typically LiCoO ₂ ), and a lithium manganese oxide (typically LiMn ₂ O ₄ ). The use of one or more lithium transition metal oxides is preferred.

  Here, the “lithium nickel oxide” refers to an oxide having Li and Ni as constituent metal elements, and one or more metal elements other than Li and Ni (that is, other than Li and Ni). The ratio of transition metal element and / or typical metal element) to the same level as Ni or less than Ni (in terms of the number of atoms. When two or more kinds of metal elements other than Li and Ni are included, both of them are less than Ni. It is also meant to include composite oxides contained in a ratio). The metal element is selected from the group consisting of, for example, Co, Al, Mn, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, copper, Zn, Ga, In, Sn, La, and Ce. Or one or more elements.

Other general formulas:
_{Li (Li a Mn x Co y} Ni z) O 2
(A, x, y, z in the previous equation are real numbers satisfying a + x + y + z = 1)
A so-called ternary lithium-excess transition metal oxide containing three kinds of transition metal elements as represented by the general formula:
xLi [Li _1/3 Mn _2/3 ] O _2. (1-x) LiMeO ₂
(In the above formula, Me is one or more transition metals, and x satisfies 0 <x ≦ 1)
It may be a so-called solid solution type lithium-excess transition metal oxide or the like.

Further, the positive electrode active material has a general formula of LiMAO ₄ (where M is at least one metal element selected from the group consisting of Fe, Co, Ni and Mn, and A is P, Si, S and And an anion selected from the group consisting of V.).

  The compound which comprises such a positive electrode active material can be prepared and prepared by a well-known method, for example. For example, some raw material compounds appropriately selected according to the composition of the target positive electrode active material are mixed at a predetermined ratio, and the mixture is fired by an appropriate means. Thereby, the oxide as a compound which comprises a positive electrode active material can be prepared. In addition, the preparation method of a positive electrode active material (typically lithium transition metal oxide) itself does not characterize this invention at all.

  Moreover, although there is no strict restriction | limiting about the shape of a positive electrode active material, the positive electrode active material prepared as mentioned above can be grind | pulverized, granulated, and classified by an appropriate means. For example, a lithium transition metal oxide powder substantially composed of secondary particles having an average particle size in the range of about 1 μm to 25 μm (typically about 2 μm to 15 μm) is used as the positive electrode in the technology disclosed herein. It can preferably be employed as an active material. Thereby, the granular positive electrode active material powder substantially comprised by the secondary particle which has a desired average particle diameter and / or particle size distribution can be obtained.

<Carbon material>
In the manufacturing method disclosed herein, a carbon material can be used as a conductive additive. In the step (A), the carbon material is prepared in the form of a pasty carbon composition containing a granular carbon material, a binder, and a solvent. Here, it is preferable to prepare a pasty carbon composition that can be expected to satisfy the determination process (1) and the determination process (2) as described above. For example, in the particle size distribution of the carbon material, a bimodal distribution having a first peak (P1) having a relatively small particle size and a second peak (P2) having a relatively large particle size is shown, and Prepare a sample that includes a volume-based abundance ratio H1 (%) in the first peak and a volume-based abundance ratio H2 (%) in the second peak that satisfies (H1 / H2)> 1. be able to.
The particulate carbon material contained in the pasty carbon composition is not particularly limited as long as it exhibits conductivity that can function as a conductive material. For example, various carbon blacks (for example, acetylene black, furnace black, ketjen black), and carbon powders such as graphite powders can be used. These may use together 1 type, or 2 or more types.

  The average particle diameter of the carbon material particles (secondary particles) may be about 1/500 to 1/20 of the average particle diameter of the electrode active material. Furthermore, in the manufacturing method disclosed herein, the carbon material preferably has an average particle size of secondary particles of 20 μm or less, and more preferably in the range of 200 nm to 10 μm. If the average particle size of the secondary particles is larger than 20 μm, it is difficult to fit in the gap between the positive electrode active materials, and the density of the positive electrode active material in the negative electrode active material layer may be lowered, which is not preferable. Regarding the lower limit of the average particle size of the secondary particles, too fine particles are not preferable because they tend to be biased toward the upper layer portion in the formation of the positive electrode active material layer. From the viewpoint of ease of handling, for example, the average particle size is preferably 50 nm or more, more preferably 100 nm or more, and more specifically 200 nm or more. For example, when the average particle size of the secondary particles is in the range of 200 nm to 10 μm, the quality of the pasty carbon composition becomes more stable with respect to the production method disclosed herein. The viscosity of the positive electrode active material layer forming composition can be easily controlled.

  Further, in the production method disclosed herein, the particle size distribution of the carbon material has a bimodal distribution as described above, and the diameter at the peak of the peak on the smaller particle size side is less than 1 μm, The diameter at the peak of the peak on the larger particle diameter side is preferably 1 μm or more. The carbon material is preferably carbon black having an average particle diameter based on a laser diffraction method of primary particles of 100 nm or less. By using a pasty carbon composition containing a carbon material having such particle size characteristics, a high-quality composition for forming a positive electrode active material layer can be stably prepared.

<Binder>
The binder has a function of binding each particle of the positive electrode active material and the carbon material contained in the positive electrode active material layer, or binding these particles and the positive electrode current collector. As such a binder, a polymer that can be dissolved or dispersed in a solvent used when forming the positive electrode active material layer can be used.
For example, when an aqueous solvent is used as this solvent, carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC) are used as water-soluble (water-soluble) polymer materials. ) And the like; polyvinyl alcohol (PVA); and the like. Examples of polymer materials that are dispersed in water (water-dispersible) include vinyl polymers such as polyethylene (PE) and polypropylene (PP); polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), and tetrafluoroethylene. -Fluororesin such as hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA); vinyl acetate copolymer; styrene butadiene rubber (SBR), acrylic acid modified SBR resin Examples thereof include rubbers such as (SBR latex).

When a non-aqueous solvent is used as a solvent, a polymer (polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyacrylonitrile (PAN), etc.) can be preferably used.
In addition to the function as a binder, the polymer material exemplified as the binder is a thickener for a positive electrode active material layer forming paste (hereinafter sometimes simply referred to as a paste) prepared to form a positive electrode active material layer. It may be used for the purpose of exhibiting the function as another additive.
<Solvent>
As the solvent, any of an aqueous solvent and a non-aqueous solvent can be used. Examples of the aqueous solvent include water and a composition using a mixed solvent mainly composed of water (aqueous solvent). As a solvent other than water constituting the mixed solvent, one or two or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used. A suitable example of the non-aqueous solvent is N-methyl-2-pyrrolidone (NMP).

≪Manufacture of secondary battery electrode≫
FIG. 4 is a flowchart showing a part of the steps of the method for manufacturing a secondary battery electrode as one embodiment. Note that, due to the space relationship, “paste-like carbon composition” is abbreviated as “paste-like carbon” in FIG. 4 and FIG. 5 described later. The process shown in FIG. 4 shows an example of a process for obtaining the correlation required in the determination process (2) of the pasty carbon composition, and is performed in advance prior to the actual production of the electrode. It is preferable to do.
<Preliminary steps>
First, in step S100, for example, from a pasty carbon composition delivered as a product, a plurality of pasty carbon compositions having different production lots are extracted as samples (specimens). For example, samples can be extracted from four or more lots. When a lot of products are manufactured per lot, for example, based on statistical methods, a plurality of pasty carbon compositions are extracted from the same lot according to the number of products manufactured in one lot. May be.

  Next, in Step S111, an appropriate amount of the extracted paste-like carbon composition is selected, and using this as a sample, the particle size distribution of the carbon material contained in the composition is measured using a laser diffraction particle size distribution measuring device. And from this measurement result, in step S113, the standard deviation (a) regarding the particle size distribution of the carbon material is calculated. Depending on the particle size distribution measuring apparatus to be used, there may be provided an analyzing means for analyzing the measured particle size distribution data, and the standard deviation (a) may be obtained using these analyzing means.

  On the other hand, using the remaining pasty carbon composition subjected to the particle size distribution, a positive electrode active material layer forming composition is prepared in step S121. Here, materials and blends other than the paste-like carbon composition are specified (that is, standard blends). In addition, preparation of this composition for positive electrode active material layer formation can be performed in accordance with a well-known method. The step of preparing the positive electrode active material layer forming composition will be described later. In step S123, the viscosity (b) of the prepared positive electrode active material layer forming composition is measured. Measuring equipment and strict measurement conditions can be determined as appropriate. For example, the viscosity measured using a rheometer under certain conditions such as 25 ° C. and 600 mPa · s can be employed.

In the next step 130, a correlation equation between the standard deviation (a) obtained in step S113 and the viscosity (b) obtained in step S123 is obtained. Usually, these standard deviation (a) and viscosity (b) have a linear relationship. If the coefficient of determination R ² is low, it may be such as increasing the number of specimens. Moreover, the acceptable viscosity range of the composition for positive electrode active material layer formation is determined according to the characteristic of a desired electrode, etc. In addition, you may make it determine the acceptable standard deviation range which achieves this acceptable viscosity range from the said correlation.

Note that the method of the present invention does not necessarily have to be performed in the order shown in the flowchart of FIG. For example, in the example of FIG. 4, the particle size distribution measurement of step S111 is performed after the sample extraction of step S100, but the active material forming composition of step S121 is prepared before step S111. Alternatively, these steps may be performed simultaneously.
<< Preparation of Pasty Carbon Composition (A) Process >>
And in the manufacturing method disclosed here, the paste-like carbon composition containing the granular carbon material which is a electrically conductive material, a binder, and a solvent in (A) process is prepared. The pasty carbon composition may be prepared and prepared using each material at the time of manufacture, or may be prepared as a product.

<Determination of pasty carbon composition>
Next, it is determined whether the pasty carbon composition prepared in the step (A) includes determination processes (1) to (2). FIG. 5 is an example of a flowchart showing a method for performing the determination processes (1) to (2).
First, in the determination processes (1) to (2), as shown in step S200, it is confirmed whether or not the pasty carbon to be used has been switched to a product of a new lot. When the lot is not switched, as shown in step S300, the electrode can be manufactured using the pasty carbon as it is. On the other hand, when the lot is switched, the process proceeds to the determination as to whether the pasty carbon of the lot satisfies the determination processes (1) to (2).

First, in step S211, the particle size distribution is measured for the carbon material contained in the pasty carbon to be used. In step S213, the standard deviation σ relating to the particle size distribution and the viscosity η of the positive electrode active material layer forming composition corresponding to the standard deviation σ are calculated from the measurement result. The calculation of the standard deviation σ can be performed in the same manner as Step S111 and Step S113. Further, the viscosity η can be calculated from the relational expression between the standard deviation (a) and the viscosity (b) obtained in advance in step S130.
Next, in step S220, it is determined whether or not this viscosity η is included in the acceptable viscosity range obtained previously. When the viscosity η is included in the acceptable viscosity range, it is determined in step S221 that the condition for the determination process (2) is satisfied. Moreover, it can be determined that the pasty carbon composition manufactured (delivered) in the same lot as the pasty carbon composition also satisfies the determination process (2). On the other hand, when the viscosity η is not included in the acceptable viscosity range, since the conditions for the determination process (2) are not satisfied, in Step S240, the pasty carbon composition is used for preparing the positive electrode active material layer forming composition. Judge that it is not suitable. In addition, the paste-like carbon composition manufactured (delivered) in the same lot as the paste-like carbon composition to be treated is also determined to be unsuitable. In this case, the same determination is started for the pasty carbon composition of the next production lot.

  If it is determined that the condition of the determination process (2) is satisfied, a determination based on the determination process (1) is performed in step S230. That is, when a bimodal distribution having a relatively small particle size peak (P1) and a relatively large particle size second peak (P2) is shown, the abundance ratio H1 (%) in the peak P1 is It is determined whether or not the ratio of the existence ratio H2 at the peak P2 is (H1 / H2)> 1. When (H1 / H2)> 1 is satisfied, the process proceeds to step S231, and it is determined that the determination process (1) is satisfied. It can be determined that the pasty carbon composition manufactured (delivered) in the same lot as the pasty carbon composition also satisfies the determination process (1). On the other hand, when (H1 / H2)> 1 is not satisfied, or when the particle size distribution of the carbon material measured in step S211 is a unimodal distribution, or a multimodal distribution of three or more peaks In step S240, the paste-like carbon composition is determined not to be suitable for the preparation of the positive electrode active material layer forming composition because the conditions for the determination process (1) are not satisfied. It is also determined that the pasty carbon composition manufactured (delivered) in the same lot as the pasty carbon composition cannot be used. In this case, it is determined whether or not the pasty carbon composition of the next production lot can be used.

  The pasty carbon determined to satisfy the conditions of the determination process (1) and the determination process (2) is determined to be suitable for use in manufacturing the secondary battery electrode in step S300. In this manufacturing method, it is not always necessary to perform each step in the order shown in the flowchart of FIG. For example, in the example of FIG. 5, the determination regarding the determination process (1) is performed after the determination regarding the determination process (2), but the determination regarding the determination process (1) precedes the determination regarding the determination process (2). These may be performed at the same time, or these may be performed simultaneously.

<< Step (B) for Preparing Electrode Active Material Layer Forming Composition >>
In the step (B), a composition for forming an electrode active material layer is prepared using the pasty carbon composition determined to have the determination processes (1) to (2). In preparing the composition for forming an electrode active material layer, a conventional lithium ion battery is used except that the carbon material is pasty carbon that is determined to have the determination processes (1) to (2) as described above. It may be the same as that of the electrode body, and there are no particular limitations on the materials and members constituting the other electrodes and the manufacturing procedure itself. That is, for example, a composition for forming an electrode active material layer containing the above-described granular positive electrode active material, pasty carbon determined above, a binder, and a solvent is prepared. Since the binder is blended in the pasty carbon, it can be blended when necessary. Specifically, the dispersion of the positive electrode active material in the solvent is, for example, a positive electrode active material such as the above-described positive electrode active material, conductive material, binder, and various kinds of dispersants, thickeners, and the like as necessary. An additive and a solvent are put into a mixer and kneaded.

Ratio of the positive electrode active material in the solid material (ie, material other than the solvent) of the positive electrode active material layer forming composition (typically substantially the same as the ratio of the positive electrode active material in the solid content of the positive electrode active material composition) Is preferably about 50% by mass or more (typically 50 to 95% by mass), more preferably about 75 to 90% by mass. The pasty carbon is preferably set so that the proportion of the carbon material in the solid material is about 3 to 25% by mass, more preferably about 3 to 15% by mass. Although the usage-amount of a binder is not specifically limited, For example, it can be set as 0.5-10 mass parts with respect to 100 mass parts of positive electrode active materials.
As a mixer for kneading, a general kneader used for preparation of the composition for forming an active material layer can be used. For example, an apparatus capable of preparing the composition, such as a kneader, a stirrer, a disperser, or a mixer, can be used.

<< Step (C) for Forming Electrode Active Material Layer >>
In the step (C), the prepared composition for forming an electrode active material layer is supplied by, for example, coating on an electrode current collector and dried by removing the solvent, and the electrode active material layer is formed on the current collector. Form.
About application | coating of the composition for positive electrode active material layer forming, it can carry out using well-known various coating apparatuses. For example, it can be suitably performed by using an appropriate coating apparatus such as a slit coater, a die coater, a comma coater, or a gravure coater. The application amount of the composition for forming an active material layer is not particularly limited, and can be arbitrarily set depending on the use of a secondary battery including a target electrode, for example. For example, it can be appropriately set within a range of about 3 to 50 mg / cm ² .
And the positive electrode active material layer is formed on an electrode electrical power collector by drying the apply | coated composition for positive electrode active material layer formation. This drying is not particularly limited as long as it is a technique capable of removing excess volatile components (that is, a solvent), and an appropriate means can be adopted as necessary. At this time, an appropriate drying accelerating means (such as a heater) may be used as necessary.

  The entire composition for forming a positive electrode active material layer after application or after drying can be pressed as needed or cut into a desired size, thereby achieving a desired thickness. And get an electrode of size. As a pressing (compression) method, conventionally known compression methods such as a roll pressing method and a flat plate pressing method can be employed. In adjusting the thickness of the positive electrode active material layer, the thickness may be measured with a film thickness measuring instrument, and the press pressure may be adjusted and compressed several times until the desired thickness is obtained. Thereby, the positive electrode is completed.

  Hereinafter, an embodiment of a method for producing a lithium secondary battery including a positive electrode (positive electrode sheet) produced by the method for producing an electrode for a secondary battery disclosed herein as a constituent member will be described with reference to the drawings. It is not intended that the invention be limited to such embodiments. That is, as long as the electrode manufactured by the secondary battery electrode manufacturing method disclosed herein is employed, the composition and form of the electrode active material to be used, the shape of the lithium secondary battery to be constructed (outer shape and The size is not particularly limited. The battery outer case may have a square shape, a cylindrical shape, or a small button shape. Moreover, the thin sheet | seat type comprised by a laminated film etc. may be sufficient as an exterior. In the following embodiment, a rectangular battery will be described.

  In addition, in the following drawings, the same code | symbol is attached | subjected to the member and site | part which show the same effect | action, and the overlapping description may be abbreviate | omitted. Moreover, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship.

  FIG. 6 is a perspective view schematically showing the lithium secondary battery according to the present embodiment. FIG. 7 is a longitudinal sectional view taken along line VII-VII in FIG. As shown in FIGS. 6 and 7, the lithium secondary battery 10 according to this embodiment includes the above-described constituent materials (active material for each positive and negative electrode, current collector for each positive and negative electrode, separator, etc.). And a battery case 15 having a rectangular shape (typically a flat rectangular parallelepiped shape) that accommodates the electrode body 50 and a suitable non-aqueous electrolyte (typically, an electrolyte).

  The case 15 includes a box-shaped case main body 30 in which one of the narrow surfaces in the flat rectangular parallelepiped shape is an opening 20, and the opening 20 is attached (for example, welded) to the opening 20. And a lid 25 for closing. As a material constituting the case 15, the same material as that used in a general lithium secondary battery can be used as appropriate, and there is no particular limitation. For example, a metal (for example, aluminum, steel, etc.) container, a synthetic resin (for example, a polyolefin resin, a high melting point resin such as a polyamide resin, etc.), or the like can be preferably used. The case 15 according to the present embodiment is made of, for example, aluminum.

  The lid body 25 is formed in a rectangular shape that matches the shape of the opening 20 of the case body 30. Further, the lid body 25 is provided with a positive electrode terminal 60 and a negative electrode terminal 70 for external connection, respectively, and a part of these terminals 60, 70 protrudes from the lid body 25 toward the outside of the case 15. It is formed to do. Similarly to the case of the conventional lithium secondary battery, the lid 25 is provided with a safety valve (not shown) for discharging the gas generated inside the case 15 to the outside of the case 15 when the battery is abnormal. It has been. The safety valve can be used without any limitation as long as it has a mechanism that opens and discharges gas to the outside of the case 15 when the pressure inside the case 15 exceeds a predetermined level.

  In the present embodiment, as shown in FIG. 7, the lithium secondary battery 10 includes a wound electrode body 50. The electrode body 50 is accommodated in the case main body 30 in a posture in which the winding axis is laid down (that is, in the direction in which the opening 20 is positioned in the lateral direction with respect to the winding axis). The electrode body 50 includes a positive electrode sheet (positive electrode) 66 having a positive electrode active material layer 64 formed on the surface of a long sheet-like positive electrode current collector 62 and a long sheet-like negative electrode current collector (electrode current collector). A negative electrode sheet (negative electrode) 76 having a negative electrode active material layer (electrode active material layer) 74 formed on the surface of 72 is overlapped with two long separator sheets 80 and wound, and the obtained electrode body 50 is wound. It is formed into a flat shape by crushing it from the side direction and causing it to be ablated.

  Further, in the wound positive electrode sheet 66, the positive electrode current collector 62 is exposed without forming the positive electrode active material layer 64 at one end portion along the longitudinal direction. On the other hand, the wound negative electrode Also in the sheet 76, the negative electrode current collector 72 is exposed at one end portion along the longitudinal direction without forming the negative electrode active material layer 74. A positive electrode terminal 60 is joined to the exposed end of the positive electrode current collector 62, and is electrically connected to the positive electrode sheet 66 of the wound electrode body 50 formed in the flat shape. Similarly, the negative electrode terminal 70 is joined to the exposed end portion of the negative electrode current collector 72 and is electrically connected to the negative electrode sheet 76. The positive and negative electrode terminals 60 and 70 and the positive and negative electrode current collectors 62 and 72 can be joined by, for example, ultrasonic welding, resistance welding, or the like.

  The material and the member itself constituting the wound electrode body 50 having the above-described configuration are the positive electrode or the negative electrode, except that an electrode manufactured according to the electrode manufacturing method disclosed herein (here, the positive electrode sheet 66) is employed. It may be the same as the electrode body of a conventional lithium secondary battery and is not particularly limited.

In the present embodiment, the produced positive electrode sheet 66 and negative electrode sheet 76 are stacked and wound together with two separators (for example, porous polyolefin resin) 80. Thereby, the wound electrode body 50 is accommodated in the case main body 30 so that the winding axis of the obtained wound electrode body 50 lies sideways. Then, a nonaqueous electrolytic solution such as a mixed solvent of EC and DMC (for example, a mass ratio of 1: 1) containing an appropriate amount (for example, a concentration of 1 M) of an appropriate supporting salt (for example, a lithium salt such as LiPF ₆ ) is injected. Then, the lithium secondary battery 10 of this embodiment can be constructed by attaching and sealing the lid body 25 to the opening 20 of the case body 30. For sealing the opening 20 of the case body 30, for example, the lid body 25 may be welded to the case body 30. In this case, welding is preferably performed by laser welding, for example.

  In the embodiment described above, the method for manufacturing an electrode for a lithium secondary battery disclosed herein is applied when manufacturing the positive electrode sheet 66. Such a form is not limited to the positive electrode, and can be applied to the production of a negative electrode for a lithium secondary battery, for example. Moreover, although lithium secondary battery 10 was illustrated in embodiment mentioned above, this invention is not restricted to a lithium secondary battery, It is with respect to the electrodes (positive electrode and negative electrode) of secondary batteries, such as a nickel metal hydride battery and a lithium capacitor. Even can be applied.

  Such a lithium secondary battery 10 can be used as a secondary battery for various applications. For example, as shown in FIG. 8, it can be suitably used as a positive electrode of a lithium secondary battery as a power source of a vehicle driving motor (electric motor) mounted on a vehicle 1 such as an automobile. Although the kind of vehicle 1 is not specifically limited, Typically, they are a hybrid vehicle, an electric vehicle, a fuel cell vehicle, etc. Such lithium secondary batteries may be used singly or may be used in the form of an assembled battery that is connected in series and / or in parallel.

Hereinafter, the present invention will be further described with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to these examples.
≪Size distribution of carbon particles in carbon paste≫
A paste-like carbon composition (hereinafter simply referred to as carbon paste) as a product prepared by the following formulation was extracted one by one from four different product lots to obtain carbon pastes A to D.
Acetylene black (AB): polyvinylidene fluoride (PVdF): dispersant = 8: 2: 0.2
The particle size distribution of the carbon particles (AB) contained in these carbon pastes A to D was measured under the following conditions using a particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., Microtrac MT3300) by a laser diffraction scattering method.

Measurement time: 10 sec
Calculation mode: MT3000II
Particle permeability: absorption The results are shown in FIG. FIG. 9 confirms that there is a great difference in the form of the particle size distribution of the carbon particles contained in the carbon paste of the same standard. The carbon pastes A to D can be considered to have substantially the same particle size width indicating the range of the particle size from the smallest particle to the largest particle of the carbon particles contained therein. However, the particle size distribution regarding the carbon pastes A and B has a clear bimodal distribution, and the peak of the first peak is low compared to the particle size distributions of the carbon pastes C and D, and the whole is broad. Recognize. On the other hand, it can be seen that the carbon pastes C and D have a bimodal distribution in which the second peak is very small. The peak of the first peak is sharper than the carbon pastes A and B. Thus, from FIG. 9, these carbon pastes A to D are prepared by blending two types of carbon particles having different average particle diameters, and the frequency at the peak of the distribution of carbon particles having smaller average particle diameters. However, it is assumed that the frequency at the peak of the distribution of carbon particles having a larger average particle diameter is controlled to be higher. Therefore, it can be confirmed that the peak diameter of the first peak in the particle size distribution of the carbon particles contained in the carbon paste corresponds to the mode diameter of the carbon particles. All of the carbon particles of the carbon pastes A to D have a particle size at the peak of the distribution of carbon particles having a smaller average particle size of 0.45 μm, and particles at the peak of the distribution of carbon particles having a larger average particle size. The diameter was about 3.9 μm and was almost the same (common).

≪Viscosity of positive electrode paste≫
A positive electrode paste having a predetermined composition shown below was prepared by adding a positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) to the above carbon pastes A to D and mixing and kneading them. The prepared positive electrode paste was used as positive electrode pastes A to D according to the type of carbon paste used.
Positive electrode active material: acetylene black (AB): polyvinylidene fluoride (PVdF): dispersant = 89.8: 8: 2: 0.2
The viscosity of these positive electrode pastes A to D was measured using a B-type viscometer under the conditions of 25 ° C. and 2S- ¹ . The results are shown in FIG. Although the positive electrode pastes A to D were prepared using the same standard carbon paste with the same composition, it was confirmed that the viscosities greatly differed only by different product lots of the carbon paste. As a general trend, the viscosity of the positive electrode paste using the carbon paste having a low first peak in the particle size distribution is higher, and the viscosity of the positive electrode paste using the carbon paste having the higher first peak in the particle size distribution is lower. I understand that.

≪Relationship between standard deviation of particle size distribution and viscosity of positive electrode paste≫
The standard deviation of the particle size distribution of each paste was determined from the measurement results of the particle size distributions of the carbon pastes A to D described above. Then, the correlation between the standard deviation and the viscosity of the positive electrode pastes A to D was examined and shown in FIG.
As can be seen from FIG. 11, the standard deviation of the particle size distribution of the carbon particles contained in the carbon pastes A to D and the viscosity of the positive electrode pastes A to D prepared using these carbon pastes A to D are almost linear. It can be seen that there is a correlation. For example, in the example shown in FIG. 11, when the standard deviation of the particle size distribution of the carbon pastes A to D is taken on the X axis and the viscosity of the positive electrode paste is taken on the Y axis, the determination coefficient R ² = 0.8821 and a high contribution rate. Both have a linear relationship represented by the following approximate expression (1).

y = 6269.9x-3188.5 ... (1)
From this, it can be said that whether a positive electrode paste having a predetermined composition and a viscosity that falls within the target viscosity range can be prepared depends on the standard deviation of the particle size distribution of the carbon particles contained in the carbon paste used for preparing the positive electrode paste. .
Therefore, the standard deviation is examined in advance from the particle size distribution of the carbon particles contained in the carbon paste used for the preparation of the positive electrode paste, and the viscosity of the positive electrode paste prepared with a predetermined composition using the carbon paste is measured. If the relationship between the standard deviation and the viscosity is examined for a plurality of carbon pastes having different production lots, a linear format indicating the correlation between the two can be obtained. Then, in the actual electrode manufacturing process, the standard deviation of the positive electrode paste is calculated by the above formula (1) only by examining the standard deviation from the particle size distribution of the carbon particles contained in the carbon paste to be used, using the obtained linear form as a calibration curve. The viscosity is calculated, and it is possible to determine whether or not the viscosity of the obtained positive electrode paste is within the target acceptable viscosity range. Alternatively, since the range of the standard deviation of the particle size distribution of the carbon particles that achieves the acceptable viscosity range of the target positive electrode paste is obtained by the above formula (1), the standard deviation of the particle size distribution of the carbon particles contained in the carbon paste to be used Is within the range (acceptable standard deviation range).

More specifically, in the example shown in FIG. 11, the acceptable viscosity range of the positive electrode paste is set to 2000 to 4500 mPa · s, and the target is to prepare a positive electrode paste having a viscosity that falls within this viscosity range. . In this case, a carbon paste having a standard deviation of the particle size distribution of the carbon particles contained therein calculated from the above approximate expression (1) within the range of about 0.83 to about 1.22 (μm) is used. It can be seen that a positive electrode paste having a viscosity in the range of 2000 to 4500 mPa · s can be obtained by preparing a positive electrode paste with a predetermined composition.
By managing the quality of the carbon paste in this way, the viscosity can be predicted before the positive electrode paste is actually prepared in the manufacturing process. Therefore, it is possible to purchase only a high-quality carbon paste in the manufacture of the electrode, and it is possible to suppress extra costs. Further, when preparing the positive electrode paste (typically during kneading), it is not necessary to adjust the viscosity in-situ, and a stable positive electrode paste can be prepared. In addition, since the viscosity of the positive electrode paste can be predicted, it can be considered to appropriately prepare the positive electrode paste in advance according to the standard deviation of the particle size distribution of the carbon particles in the carbon paste.

≪Production of positive electrode≫
Using the above-obtained 0.83 to 1.22 μm as the range of acceptable standard deviation, the carbon bases of other production lots were used, and the production method disclosed herein and thus the positive electrode was produced. First, when the particle size distribution of the carbon particles in the carbon base used was measured, it was confirmed that it was a bimodal distribution, and the particle diameter at a smaller peak was the mode diameter. Moreover, it confirmed that the standard deviation regarding the particle size was 1.15 which is within the allowable standard deviation. Next, a positive electrode active material layer forming composition was prepared with a predetermined composition. Then, the viscosity at 25 ° C. and 2S ⁻¹ of the obtained composition was about 4007 mPa · s, and a composition having a desired viscosity could be obtained without adjusting the viscosity. When a positive electrode was produced using this composition, it was possible to successfully apply and dry the positive electrode active material layer forming composition, and to obtain a positive electrode with good coating properties.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

  According to the technology disclosed herein, the composition for forming an electrode active material layer can be obtained by accurately managing the quality of the paste-like carbon composition (typically, the particle size distribution characteristics of the carbon material contained in the composition). Provided is a method for producing an electrode for a secondary battery, which can easily prepare a product with high quality. According to this manufacturing method, when preparing the positive electrode paste (typically at the time of kneading), it is not necessary to adjust the viscosity in-situ, and a stable positive electrode paste can be prepared. Therefore, the manufacturing effort can be saved, and the manufacturing time and cost can be reduced.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Lithium secondary battery 15 Battery case 20 Opening part 25 Cover body 30 Case main body 50 Winding electrode body 60 Positive electrode terminal 62 Positive electrode current collector (electrode current collector)
64 Positive electrode active material layer (electrode active material layer)
66 Positive electrode sheet (positive electrode)
70 Negative electrode terminal 72 Negative electrode current collector (electrode current collector)
74 Negative electrode active material layer (electrode active material layer)
76 Negative electrode sheet (negative electrode)
80 separator

Claims (6)

A method for producing an electrode for a secondary battery in which an electrode active material layer mainly composed of an electrode active material is formed on an electrode current collector,
(A) a step of preparing a pasty carbon composition containing a granular carbon material as a conductive material, a binder, and a solvent;
(B) preparing a paste-like electrode active material layer forming composition containing the paste-like carbon composition, an electrode active material, a binder, and a solvent; and
(C) supplying the electrode active material layer forming composition onto an electrode current collector, and forming an electrode active material layer on the current collector;
Including
Here, the paste-like carbon composition used for preparing the electrode active material layer forming composition in the step (B) has a laser particle size distribution of the composition prepared in the step (A). The following determination processes (1) to (2) are performed based on the diffraction method and performed based on the measurement results:
(1) The particle size distribution shows a bimodal distribution having a first peak (P1) having a relatively small particle size and a second peak (P2) having a relatively large particle size in the particle size distribution. And the ratio of the volume-based abundance ratio H1 (%) in the first peak and the volume-based abundance ratio H2 (%) in the second peak satisfies (H1 / H2)>1;
(2) Based on the standard deviation σ in the measured particle size distribution,
Standard deviation in particle size distribution measured for a plurality of pasty carbon compositions of different production lots, and viscosity measured for the same kind of electrode active material layer forming composition prepared in advance using each of the pasty carbon compositions From the correlation equation of
The viscosity of the electrode active material layer forming composition corresponding to the standard deviation σ of the paste-like carbon composition to be judged is calculated, and the calculated viscosity is included in a predetermined acceptable viscosity range;
A method for producing an electrode for a secondary battery, characterized in that both are provided.   2. The production of a secondary battery electrode according to claim 1, wherein the granular carbon material contained in the pasty carbon composition has an average secondary particle diameter in the range of 200 nm to 10 μm. Method.   The paste-like carbon composition used for preparing the electrode active material layer forming composition in the step (B) is such that the first peak (P1) in the particle size distribution has a particle size of less than 1 μm. The method for producing an electrode for a secondary battery according to claim 1, wherein the second peak (P2) is at a particle size of 1 μm or more.   The said granular carbon material is carbon black whose average particle diameter based on the laser diffraction method of a primary particle is 100 nm or less, The manufacturing of the electrode for secondary batteries as described in any one of Claims 1-3 characterized by the above-mentioned. Method.   It implements in order to manufacture the positive electrode of a lithium ion secondary battery using the material which comprises the positive electrode active material of a lithium ion secondary battery as the said electrode active material. The manufacturing method of the electrode for secondary batteries of.   A secondary battery provided with the electrode manufactured by the manufacturing method as described in any one of Claims 1-5.

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