JP6048161B2 - Manufacturing method of secondary battery - Google Patents

Description

  The present invention relates to a method for manufacturing a secondary battery using an electrode plate having an active material layer. More specifically, the present invention relates to a method of appropriately manufacturing an electrode mixture paste for forming an active material layer in an electrode plate and manufacturing a secondary battery using the electrode mixture paste.

  A secondary battery usually has a configuration in which positive and negative electrode plates are wound together with a separator and housed in a case. The electrode plate is a current collector foil coated with an active material layer. Therefore, an electrode plate is manufactured by coating the metal foil used as current collection foil with the paste containing an active material component, and drying it. Naturally, the paste is manufactured by kneading a powdery active material component and a liquid solvent component. As the prior art relating to the manufacture of the paste, the one described in Patent Document 1 can be cited. In the technique of Patent Document 1, a reagent liquid is dropped on the electrode active material powder, and the kneading torque is measured. The properties of the electrode active material are evaluated based on the relationship between the amount of reagent liquid dropped and the kneading torque. This is because various conditions at the time of manufacturing the paste are determined based on the properties thus evaluated.

JP 2005-285606 A

  However, the conventional techniques described above have the following problems. That is, what is evaluated by the technique of Patent Document 1 is the properties of pure electrode active material powder. On the other hand, the powder component when actually producing a paste by kneading is not limited to the electrode active material. Additives such as thickeners may be included. For this reason, the actual properties of the paste are different from the properties evaluated by the technique of Patent Document 1. For this reason, the technique of Patent Document 1 has a problem that the properties of the actual paste cannot be appropriately evaluated.

In addition, an electrode active material having a tap density of 1.0 g / cm ³ or more may be used as a powder component when producing a paste. Such a high tap density electrode active material (see FIG. 6) is more likely to clog particles compared to a low tap density electrode active material with a tap density of less than 1.0 g / cm ³ (see FIG. 7). The gap between the particles 50 tends to narrow. Therefore, it is difficult for the solvent to enter between the particles 50 in the preliminary kneading for determining the optimum amount of the solvent for the powder component (mixing ratio between the powder component and the solvent component). On the other hand, in the actual kneading for producing an actual electrode mixture paste, the clogging of the electrode active material particles is dispersed by kneading, so that the solvent is more likely to enter between the particles of the electrode active material than during preliminary kneading. . Therefore, even if the optimum mixing ratio is determined in the preliminary kneading, the optimum mixing ratio in the main kneading may not be achieved.

The present invention has been made for the purpose of solving the problems of the prior art described above. That is, the subject is a method for manufacturing a secondary battery capable of manufacturing an electrode mixture paste having good properties even when an electrode active material having a tap density of 1.0 g / cm ³ or more is used. Was to provide.

In order to solve this problem, the method for manufacturing a secondary battery according to the present invention is to manufacture an electrode mixture paste by kneading the powder component and the solvent component of the electrode mixture layer of the secondary battery, In a secondary battery manufacturing method for manufacturing a secondary battery using an electrode plate having an electrode mixture layer formed on the basis of a material paste, an electrode active material and an additional component among powder components used at the time of electrode mixture paste preparation. To the powder of the same component as the adhesive, inject the solvent of the same component as the solvent component used when making the electrode mixture paste while measuring the liquid absorption amount and the powder and the injected solvent while measuring the kneading torque. A mixing ratio equal to the ratio of the amount of the powder component at the start of the pre-kneading step and the cumulative amount of solvent supply when the kneading torque shows the maximum value during the pre-kneading step. , Electrode mixture paste powder Min and a coarse paste kneading step of kneading a mixture of solvent components, in accordance with the required specifications from the lower step to be performed later compounding ratio with the addition of a binder to the crude paste kneading step after the composite electrode material paste In addition, when the tap density of the electrode active material contained in the powder component used when preparing the electrode mixture paste is 1.0 g / cm ³ or more, before the preliminary kneading step, The electrode active material used in the preliminary kneading step is mixed with a solvent having the same component as the solvent component used at the time of preparing the electrode mixture paste for a predetermined time according to the tap density. An electrode mixture paste is manufactured by performing a wetting step to be included. Here, the cumulative supply amount of the solvent when the kneading torque shows the maximum value in the preliminary kneading step includes not only the solvent injected in the preliminary kneading step but also the solvent mixed in the wet step.

In this secondary battery manufacturing method, preliminary kneading is performed. The purpose of the pre-kneading, the mixing ratio of the powder component and the solvent component in the crude paste kneading, is to determine prior to rough kneading kneading. Therefore, the same powder component and solvent component as those used during rough kneading are used. Then, the blending ratio is determined by the amount of solvent when the kneading torque becomes maximum.
Here, in the method for producing a secondary battery of the present invention, when the tap density of the electrode active material contained in the powder component used at the time of preparing the electrode mixture paste is 1.0 g / cm ³ or more, a preliminary kneading step Before wetting, a wetting process is performed. In the wetting step, the electrode active material used in the pre-kneading step is mixed with a solvent having the same component as the solvent component used when preparing the electrode mixture paste for a predetermined time according to the tap density. This includes a predetermined amount of solvent. That is, the solvent is impregnated in advance with respect to the electrode active material having a tap density of 1.0 g / cm ³ or more which is difficult to absorb the solvent. In other words, the electrode active material is supplemented in advance with a solvent that is not absorbed in the preliminary kneading step because the tap density is as high as 1.0 g / cm ³ or more.
Then, preliminary kneading is performed using the powder containing the electrode active material that has undergone such a wetting process. Therefore, in the preliminary kneading step, the mixing ratio between the powder component and the solvent component during the rough kneading can be accurately determined. Therefore, by performing rough kneading with the mixing ratio determined in this way, an electrode mixture paste having good properties can be obtained with a mixing ratio that matches the characteristics of the raw materials used.

According to the method for manufacturing a secondary battery of the present invention, an electrode mixture paste having good properties can be manufactured even when an electrode active material having a tap density of 1.0 g / cm ³ or more is used.

It is a graph which shows the wetting time required for an electrode active material in relation to the tap density of an electrode active material. It is sectional drawing which shows the structure of the oil absorption amount measuring machine used by this form. It is a graph which shows the typical example of the fluctuation | variation of the kneading | mixing torque of a stirrer when the quantity of a powder is made constant and the amount of solvents is increased gradually. It is a graph which shows the result of the torque measurement in the preliminary kneading | mixing of the sample for negative electrodes. It is a graph which shows the final viscosity of the paste for negative electrodes. It is a figure which shows typically the particle | grains of an electrode active material with a high tap density. It is a figure which shows typically the particle | grains of an electrode active material with a low tap density.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. First, the negative electrode of the secondary battery manufactured by the method of this embodiment uses an active material having a tap density of 1.0 g / cm ³ or more. The average particle diameter (D50) of this active material is 15 μm or more and 25 μm or less. This active material is obtained by coating the surface of graphite particles with an amorphous film.

  Here, the graphite particles in the present embodiment are artificial graphite obtained from pitch as a precursor, natural graphite, and the like. When such graphite particles are exposed, there is a risk that a deteriorated film is formed by contact with the electrolytic solution. That is, when graphite particles are used as an active material as they are, there is a risk that the battery characteristics of the secondary battery will deteriorate. The main purpose of preventing this is to cover the surface of the graphite particles with an amorphous film. The amorphous film in this embodiment is a film made of amorphous carbon.

In this embodiment, a secondary battery using the active material as described above is manufactured by the following procedure.
1. Wetting process ↓
2. Pre-kneading process (determining the compounding ratio of electrode mixture paste (hereinafter simply referred to as paste))
↓
3. Main kneading process (paste production)
↓
4). Lower process (application, winding, storage, etc.)

  Among these, “4. Downstream process” has no particular difference. The features of this embodiment are “1. Wetting step”, “2. Pre-kneading step” and “3. Main kneading step”. Among these, “1. Wetting process” and “2. Pre-kneading process” are the core parts of the present invention. Hereinafter, the description will be focused on “1. Wetting step” and “2. Preliminary kneading step”.

<Wetting step> In this embodiment, the wetting step is performed prior to the preliminary kneading step. In the wetting process, a predetermined amount of a solvent (water in this embodiment) having the same component as the solvent used in the actual paste production is included in the active material having a tap density of 1.0 g / cm ³ used in the preliminary kneading process.

Specifically, the active material and the solvent are mixed for a time determined according to the tap density of the active material. FIG. 1 is a graph showing the wet time required for the active material in relation to the tap density of the active material. The wetting time is the time during which the active material and the solvent are mixed. As shown in FIG. 1, for example, if the active material has a tap density of 1.0 g / cm ³ , it is mixed with a solvent for about 1 minute. Thereby, a predetermined amount of solvent (water) is included in the active material (graphite). In this embodiment, about 10 cm ^{3 of the} solvent is included with respect to about 30 g of the active material. Even if the tap density of the active material changes, the amount of solvent contained in the active material does not change. The equation of the graph shown in FIG. 1 is y = 0.014exp (6.5424x). In this formula, x is the tap density (g / cm ³ ) of the active material, and y is the wet time (minutes).

  <Preliminary kneading step> In this embodiment, a preliminary kneading step is performed following the wetting step. In the preliminary kneading step, the blending ratio is determined prior to the paste production. The compounding ratio here is the compounding ratio of the powder component and the solvent component. The powder component is mainly an active material powder, but it is not the only one. It is a mixed powder containing powders of additives such as thickeners. The blending ratio of each synthetic powder in this mixed powder is the same as the blending ratio when the actual paste is manufactured. In other words, the powder component is the same as the powder at the time of actual production. However, as the active material powder in the mixed powder, the active material that has been subjected to the above-described wetting step is used. Of course, the solvent component is the same as the solvent used in the actual production. When a mixture of two or more liquids is used as the solvent, the mixing ratio is the same as in actual production.

  Determination of the compounding ratio of the powder component and the solvent component in this embodiment is performed by performing preliminary kneading. Here, the preliminary kneading is to find the optimum blending ratio by kneading the powder and the solvent while changing the blending ratio. For this preliminary kneading, an oil absorption measuring device according to JIS-K101-13 is used. For this purpose, for example, an oil absorption measuring device 1 having a structure as shown in FIG. 2 can be used.

  The oil absorption amount measuring machine 1 shown in FIG. 2 includes a stirring container 2, a stirring bar 3, a liquid injection nozzle 4, and a funnel 5. The stirring container 2 is a container for pre-kneading the powder 6 and the solvent 7. A stirring bar 3 is provided in the stirring vessel 2. The stirrer 3 is, of course, for stirring the powder 6 and the solvent 7 in the stirring vessel 2 for preliminary kneading. The stirrer 3 in this embodiment can measure torque during stirring (referred to as kneading torque in the present application). The liquid injection nozzle 4 supplies a solvent to the stirring vessel 2. The liquid injection nozzle 4 in this embodiment can grasp the supply amount of the solvent. The funnel 5 is attached to the inlet of the stirring vessel 2 and guides the solvent supplied from the liquid injection nozzle 4 into the stirring vessel 2 without leakage.

  The preliminary kneading using the oil absorption measuring device 1 having the above-described configuration is performed as follows. First, only the powder 6 out of the powder 6 and the solvent 7 is stored in the stirring vessel 2. Of course, the amount P of the contained powder 6 is recorded. Then, the solvent 7 is dropped from the liquid injection nozzle 4 while the stirrer 3 is driven. Thereby, the amount of the solvent 7 is gradually increased while the amount of the powder 6 in the stirring vessel 2 is kept constant. In this process, the fluctuation of the kneading torque is recorded while keeping the rotation speed of the stirring bar 3 constant.

  Then, generally, a graph as shown in FIG. 3 is obtained. That is, the kneading torque is small at the beginning, and the kneading torque increases as the amount of the solvent 7 increases. This is presumably because the amount of paste in which the powder 6 and the solvent 7 are mixed gradually increases by adding the solvent 7 to the powder 6. In addition, it is considered that the effect of the thickener contained in the powder 6 appears as the amount of the solvent 7 increases. However, the kneading torque shows a peak T at a certain solvent amount S, and conversely, the kneading torque decreases as the amount of the solvent 7 increases. This is considered to be because when the amount of the solvent 7 becomes excessive, the paste becomes diluted and the viscosity decreases. Therefore, the ratio P: S between the amount of powder P and the amount of solvent S when the kneading torque shows a peak T in the process of FIG. 3 is determined as the blending ratio of the paste. Here, the solvent amount S is the amount of solvent supplied from the beginning of the supply of the solvent 7 from the injection nozzle 4 to the peak of the kneading torque, and the amount of solvent supplied in the wetting step (the solvent included in the wetting step). It is the cumulative value.

<Main kneading step> In the subsequent "3. main kneading step", a paste is manufactured in accordance with the blending ratio P: S determined in "2. Preliminary kneading step". That is, the ratio between the amount of the powder 6 and the amount of the solvent 7 used in the actual manufacturing process is made equal to the above-described blending ratio P: S. This actual manufacturing process itself may be performed by a conventional method. As a result, even when an active material with a tap density of 1.0 g / cm ³ is used, the blending ratio appropriately matches the characteristics of the raw materials currently used, so a paste with good properties is manufactured. it can. As a result, the subsequent lower processes are performed well, and a secondary battery is manufactured.

  The application range of the blending ratio P: S determined as described above is limited to the manufacture of pastes using the same powder and solvent as the powder and solvent used for pre-kneading. It cannot be applied when the components of the powder and solvent are different, and the powder and solvent in that case need to be determined again by preliminary kneading. Furthermore, it is preferable to re-determine the mixing ratio of the raw material powder and solvent, even if they have the same specifications by the same manufacturer, if the raw material production lot changes.

  Next, examples of the present invention will be described together with comparative examples. In Examples and Comparative Examples, preliminary kneading for determining the blending ratio and subsequent main kneading were performed under the following conditions. In the following, items that do not distinguish between the embodiment and the comparative example are common to both.

[Preliminary kneading]
Kneading machine: Oil absorption amount measuring machine used in FIG. 1 Solvent: Water powder component Active material: Natural graphite Average particle size 15-25 μm Tap density 1.0 g / cm ³ or more (with wet process) “Example”
Natural graphite average particle size 15-25 μm Tap density 1.0 g / cm ³ or more (no wetting process) “Comparative Example”
Thickener: Carboxymethylcellulose sodium (CMC-Na)
Mixing ratio: 99% by weight of active material component + 1% by weight of thickener
Sample weight: 30 g
Measurement temperature: Room temperature 20 ° C. Expected solvent dropping speed: 3 cm ³ / min Stirrer rotation speed: 220 rpm

  Here, the “result” of the measured temperature means that the sample is not specially treated for the purpose of heating or cooling. However, there may be some temperature fluctuation due to frictional heat of stirring or heat of vaporization of the solvent.

  As a result of preliminary kneading under the above conditions, the results shown in FIG. 4 were obtained. In the graph of FIG. 4, the vertical axis represents the kneading torque and the horizontal axis represents the solid content. First, in an example using an active material without a wetting process (an active material that has not undergone a wetting process) as a comparative example, a peak value T1 of the kneading torque is obtained when the solid content is 66.5% by weight. . In contrast, in the example using an active material with a wetting process (an active material that has undergone a wetting process) as an example, a peak value T2 of the kneading torque is obtained when the solid content is 68.0% by weight. ing.

  Thereby, when the active material which has not passed through the wetting process is used, the blending ratio is determined so that the solid content is 66.5% by weight. On the other hand, when an active material that has undergone a wetting process is used, the mixing ratio is determined so that the solid content is 68.0% by weight.

[Main kneading]
Kneading machine: Planetary mixer (capacity 1 liter)
Solvent used: Water powder component Active material: Natural graphite Average particle size 15-25 μm Tap density 1.0 g / cm ³ or more Thickener: As described in the column of pre-kneading Binder: Styrene butadiene rubber (SBR)
Mixing ratio: active material 98% by weight + thickener 1% by weight + binder 1% by weight
Sample weight: 300 g (weight of active material and thickener)
Measurement temperature: Room temperature 20 ° C. Rough kneading Kneading Solid content: 68.0% by weight “Example”
66.5% by weight “Comparative Example”
Rotation speed: 50rpm
Kneading time: 30 minutes dilution and kneading Kneading speed: 50 rpm
Kneading time: 10 minutes Final solid content: 54% by weight

  That is, in this kneading, in both the examples and the comparative examples, first, rough kneading was performed at a blending ratio that resulted in the solid content determined in the preliminary kneading. The components of the powder used for rough kneading are only the active material and the thickener among those shown in the mixing ratio of the powder components in the main kneading column. Moreover, a little solvent was added to the paste after rough kneading, and dilution kneading was performed. Furthermore, the binder was added to the paste after the dilution kneading and final kneading was performed. The dilution kneading and final kneading are adjustment kneading for adjusting the final solid content and properties of the paste in accordance with the required specifications from the lower process. That is, in this kneading, adjustment kneading is carried out to adjust the blending ratio of the electrode mixture paste in accordance with the required specifications from the following step, following kneading in which the powder component and solvent component of the electrode mixture paste are mixed. The mixing ratio in the main kneading column is the one after addition of the binder, but the mixing ratio when looking at the active material and the thickener is the mixing ratio shown in the preliminary kneading column. Same as ratio.

  Here, the final viscosity of the paste completed by all the above-mentioned kneading steps is shown in the graph of FIG. In FIG. 5, the vertical axis represents the final viscosity of the paste, and the horizontal axis represents the solid content ratio during rough kneading. The graph of FIG. 5 shows that the paste is completed using a plurality of powder components and solvent components having different blending ratios, and the relationship between the solid content ratio during rough kneading and the final viscosity of the paste is approximated by a curve. It is a representation. The relationship includes the above-described examples and comparative examples. As can be seen from the graph of FIG. 5, the most preferable solid content ratio at the time of rough kneading is about 67.7 wt%. If this is set to the target solid content ratio and the powder component and solvent component at the time of rough kneading are blended, the final viscosity of the finished paste will be within the proper range even if some deviation occurs in the blending. It is easy.

  Here, the solid content rate determined by the preliminary kneading using the active material not subjected to the wetting step is 66.5% by weight. That is, the difference from the optimum solid content of 67.7% by weight is as large as 1.2% by weight. Furthermore, as shown in FIG. 5, since the final viscosity of the paste completed with the solid content ratio at the time of rough kneading being 66.5% by weight is too high, it is not within the proper range. This is the reason why an example using an active material that has not been subjected to a wetting step in the preliminary kneading was used as a comparative example.

  On the other hand, the solid content ratio determined by the preliminary kneading using the active material that has undergone the wet process is 68.0% by weight. That is, the difference from the optimum solid content of 67.7% by weight is as small as 0.3% by weight. Moreover, the final viscosity of the paste completed by the solid content rate is in an appropriate range. Therefore, in the examples, since the paste viscosity is low and an appropriate dispersion torque is applied, a good paste in which water as a solvent is uniformly dispersed in the powder component can be obtained. This is the reason why an example using an active material that has undergone a wetting process in pre-kneading was used as an example.

As described above, the reason why the paste having the proper viscosity is not manufactured in the comparative example and the paste having the proper viscosity is manufactured in the example is considered as follows. That is, a high tap density active material having a tap density of 1.0 g / cm ³ or more (see FIG. 6) is compared with a low tap density active material having a tap density of less than 1.0 g / cm ³ (see FIG. 7). Particles are easily clogged and the gap between particles 50 is narrow. Therefore, it is difficult for the solvent to enter between the active material particles 50 in the preliminary kneading. However, in the main kneading for producing an actual electrode mixture paste, the clogging of the active material particles is somewhat dispersed by kneading. Therefore, it becomes easier for the solvent to enter between the particles of the active material than during pre-kneading. Therefore, even if the optimum mixing ratio is determined in the preliminary kneading process without going through the wetting process for the active material having a high tap density, the mixing ratio is not suitable for the main kneading. Therefore, in the examples, when pre-kneading using an active material having a high tap density, a solvent is soaked in the active material in advance by a wetting process. That is, the solvent that cannot be absorbed by the preliminary kneading is supplemented in advance. Therefore, in the examples, since the mixing ratio is determined by performing preliminary kneading using the active material prepared in this way, the optimum mixing ratio is determined without greatly deviating from the optimum mixing ratio in the main kneading. It can be done.

  Then, using the final paste for the negative electrode obtained in the example, a secondary battery is manufactured by “4. Lower steps (coating, winding, storing, etc.)”. That is, the negative electrode paste is prepared by applying and drying the negative electrode paste onto the negative electrode current collector foil. In this application / drying stage, the quality of the paste has a great influence on the process, but this embodiment is good. This is because a paste having good properties is obtained as described above. A negative electrode mixture layer is formed on the negative electrode plate. Further, the obtained negative electrode plate and the positive electrode plate are stacked together by winding or flat stacking with a separator sandwiched therebetween to form an electrode body, and a secondary battery is manufactured by storing this electrode body in a battery case. Is done. As the positive electrode plate and the separator, those conventionally used may be used.

As described above in detail, according to the present embodiment, when the electrode mixture paste is manufactured by kneading the powder component and the solvent component, the blending ratio is determined by preliminary kneading with the same raw material. And this kneading | mixing is performed by this determined mixture ratio. In addition, when the tap density of the active material is 1.0 g / cm ³ , a predetermined amount of solvent is previously contained in the active material used for preliminary kneading . That is, the solvent is previously impregnated into the electrode active material having a tap density of 1.0 g / cm ³ or more which hardly absorbs the solvent. In other words, the electrode active material is previously filled with a solvent that is not absorbed in the preliminary kneading step because the tap density is as high as 1.0 g / cm ³ or more. Therefore, in the preliminary kneading step, an appropriate blending ratio at the time of the main kneading can be determined, and a paste having good properties can be obtained in the main kneading step. For this reason, the lower process is satisfactorily performed and a high-quality secondary battery is obtained.

The electrode active material of this embodiment has an average particle diameter (D50) of 15 μm or more and 25 μm or less. An active material having an average particle size of 15 μm or more and 25 μm or less and a tap density of 1.0 g / cm ³ or more has particularly low solvent permeability during preliminary kneading. However, if a predetermined amount of solvent is previously contained in the electrode active material by the wetting step before the preliminary kneading, a blending ratio suitable for the main kneading can be found even with an active material having such a particle size. That is, the present invention is particularly significant when the average particle diameter (D50) of the active material used is 15 μm or more and 25 μm or less.

In addition, the electrode active material of the present embodiment is formed by coating graphite particles as the core and the surface with amorphous carbon. An active material made of graphite particles coated with amorphous carbon and having a tap density of 1.0 g / cm ³ or more has particularly low solvent permeability during pre-kneading. However, if a predetermined amount of solvent is previously contained in the electrode active material by the wetting step before the preliminary kneading, a blending ratio suitable for the main kneading can be found even with an active material having such a particle size. That is, the present invention is particularly significant when the active material to be used is a material in which graphite particles are used as nuclei and the surface thereof is coated with amorphous carbon.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the kneading machine itself is not limited to the above-mentioned one, and another type may be used. In addition, various materials such as active materials are merely examples. In the wetting step, the solvent may be included in the mixed powder used in the preliminary kneading step, instead of including the solvent only in the active material used in the preliminary kneading step.

Moreover, when the tap density of the electrode active material contained in the powder component used at the time of preparing the electrode mixture paste is less than 1.0 g / cm ³ , it is not necessary to perform the wetting step. In other words, by performing “2. Pre-kneading step”, “3. Main kneading step”, and “4. Lower step” without performing the above-mentioned “1. Wetting step”, it matches the characteristics of the raw materials used. Therefore, it is possible to obtain an electrode mixture paste with good properties at a high blending ratio and to obtain a high-quality secondary battery.

  Further, in the preliminary kneading step, a powder of graphite particles (a powder of graphite particles before coating of the amorphous film) may be used as an active material component instead of the powder of the completed active material. That is, in the preliminary kneading step, the graphite particle powder before being coated with amorphous carbon is contained in the same proportion as the proportion of the electrode active material powder in the powder component used when preparing the electrode mixture paste. Ingredients were injected into the powder of the same component as the powder component used at the time of electrode mixture paste preparation while injecting a solvent of the same component as the solvent component used at the time of electrode mixture paste measurement while measuring the liquid absorption amount, and kneading torque was adjusted. You may knead | mix the powder and the inject | poured solvent, measuring. However, the final active material powder is used in this kneading process.

  The lump formed by the particles of the active material adhering to each other during the formation of the amorphous film may not be unraveled even after subsequent crushing treatment. Lumps that have not been loosened cannot be loosened by pre-kneading, but can be loosened by main kneading. Therefore, there is a possibility that the blending ratio obtained by the preliminary kneading may deviate from the proper value in the main kneading. If preliminary kneading is performed using the powder of graphite particles before the coating of the amorphous film, such problems can be prevented. The particle size distribution of the graphite particles before coating with the amorphous film and the particle size distribution of the active material after the main kneading are substantially the same. As described above, when preliminary kneading is performed using the powder of graphite particles before coating of the amorphous film, the wet process is naturally performed using the graphite particles before coating of the amorphous film. In this wetting step, the amount of the solvent contained in the graphite particles before coating with the amorphous film may be the same as the amount of the solvent contained in the graphite particles coated with the amorphous film.

2 ... Stirrer 3 ... Stirrer 4 ... Injection nozzle 6 ... Powder 7 ... Solvent

Claims (1)

A powder component and a solvent component of an electrode mixture layer of a secondary battery are kneaded to produce an electrode mixture paste, and an electrode plate having an electrode mixture layer formed on the basis of the electrode mixture paste is used. In a secondary battery manufacturing method for manufacturing a secondary battery,
While measuring the liquid absorption of the same component as the electrode active material and thickener among the powder components used when creating the electrode mixture paste, the solvent of the same component as the solvent component used when creating the electrode mixture paste A preliminary kneading step of kneading the powder and the injected solvent while measuring the kneading torque,
The electrode mixture paste was mixed at a mixing ratio equal to the ratio of the amount of the powder component at the start of the pre-kneading step and the cumulative amount of solvent supply when the kneading torque showed the maximum value during the pre-kneading step. A rough kneading step of mixing and kneading the powder component and the solvent component ;
Performing an adjustment kneading step of adjusting the blending ratio according to the required specifications from the subsequent step and adding a binder to the electrode mixture paste after the rough kneading step ,
When the tap density of the electrode active material contained in the powder component used when preparing the electrode mixture paste is 1.0 g / cm ³ or more, the electrode active material used in the pre-kneading step before the pre-kneading step In addition, by mixing a solvent having the same component as the solvent component used at the time of preparing the electrode mixture paste for a predetermined time according to the tap density, performing a wetting step including a predetermined amount of solvent, A method for producing a secondary battery, comprising producing an electrode mixture paste.

Images