JP2013229248A - Method for manufacturing battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a battery capable of improving filter permeability of an electrode paste and battery productivity.SOLUTION: A method for manufacturing a battery 100 comprises: a step S1 of granulating an active material particle 125 including a 1.0 to 15.0 wt% fine particle having a grain diameter of 0.1 to 3.0 μm; a step S2 of creating a paste; a step S3 of making a filter permeable; and a step S4 of forming an active material layer. A ratio of fine particles after granulation having a grain diameter of 0.1 to 3.0 μm in the granulation particle formed in the step S1 is lower than a ratio of fine particles in the active material particle 125. The ratio of fine particles after granulation in the granulation particle is not more than 10.0 wt%, and an occupation ratio of granulation particles having a grain diameter of 90 μm or lower is not less than 99.8 wt%.

Description

  The present invention relates to a method for manufacturing a battery including an electrode plate having an active material layer formed on an electrode foil.

  Conventionally, a battery including an electrode plate in which an active material layer is formed on an electrode foil is known. This active material layer is formed by applying an electrode paste prepared using active material particles or the like on an electrode foil and drying it. If the electrode paste contains large foreign matter or the like, problems such as streaking may occur when it is applied to the electrode foil. For this reason, prior to coating on the electrode foil, it is preferable to pass a filter through the electrode paste to remove large foreign matters. In addition, patent document 1 is mentioned as a related prior art.

JP 2010-111384 A

  However, regarding clogging of the filter, in addition to the case where particles larger than the opening of the filter become a problem, clogging may be caused by fine particles. That is, when the electrode paste passes through the filter, if the active material particles contain many fine particles having a particle size of 0.1 to 3.0 μm, a large number of fine particles adhere to the fiber portion of the filter. In some cases, the active material particles further adhere to the attached fine particles and accumulate in a bridge shape on the filter (fiber portion), and the filter opening is reduced, so that the filter is easily clogged.

  The present invention has been made in view of the current situation, and provides a battery manufacturing method in which the filter permeability of an electrode paste is good.

  One embodiment of the present invention for solving the above-described problem is a method for manufacturing a battery including an electrode plate having an active material layer formed on an electrode foil, wherein fine particles having a particle diameter of 0.1 to 3.0 μm are formed. A granulation step of granulating active material particles containing 1.0 to 15.0 wt% to form granulated particles, wherein the granulated particles have a particle size of 0.1 to 3. The proportion of fine particles after granulation of 0 μm is lower than the proportion of fine particles in the active material particles, the proportion of fine particles after granulation in the granulated particles is 10.0 wt% or less, and the particle size The granulation step in which the proportion of the granulated particles of 90 μm or less is 99.8 wt% or more, the paste creation step of creating an electrode paste using the granulated particles, and the electrode paste with an opening of 90 to A filter transmission process for transmitting a 110 μm filter , The electrode paste after the filter transmission step, coating was dried on the electrode foil, and the active material layer forming step of forming the active material layer, a method for producing a battery comprising a.

  In this battery manufacturing method, active material particles are granulated to form granulated particles satisfying the above requirements, and an electrode paste is prepared using the granulated particles. As a result, the electrode paste apparently has fewer fine particles with a particle size of 0.1 to 3.0 μm (fine particles after granulation) than before granulation. The filter permeability can be improved. In addition, since there are almost no large granulated particles having a particle size of more than 90 μm in the electrode paste, large foreign matters can be easily removed from the electrode paste without causing clogging of the filter by the large particles.

  Furthermore, it is a manufacturing method of said battery, Comprising: After the said active material layer formation process, the said active material layer is pressed, The pressing process which compresses the said active material layer while crushing the said granulated particle is provided. A battery manufacturing method is preferable.

In an electrode plate used in a battery, in order to increase the density of the active material layer, the active material layer coated with electrode paste and dried may be pressed and compressed. At that time, if the pressing pressure is too high, the electrode plate after pressing is likely to be deformed such as warpage. Among electrode foils, the pressure applied during compression differs greatly between the part where the active material layer is formed and the part where it is not formed. .
On the other hand, the active material layer formed by the electrode paste using the granulated particles described above requires a small pressing pressure for increasing the density of the active material layer. Accordingly, it is possible to suppress deformation such as warpage in the electrode plate after pressing.

The reason is considered as follows. For example, an active material particle having only a relatively large particle does not have fine particles having a particle size of 0.1 to 3.0 μm, and an electrode paste is prepared without granulation and applied. When the active material layer is formed by drying, there are no fine particles that can enter the gaps between the large particles in the active material layer. For this reason, unless the press pressure is increased, the active material layer cannot be densified.
On the other hand, active material particles that also contain fine particles are used, but when an electrode paste is prepared without granulation, and this is applied and dried to form an active material layer, the active material particles themselves are granulated particles. Since the hardness is higher than the pressure, the pressure applied to the electrode foil during pressing tends to increase. For this reason, the electrode plate after pressing is likely to be deformed such as warpage.

  In contrast, in the present manufacturing method, the active material particles before granulation contain 1.0 to 15.0 wt% of fine particles having a particle size of 0.1 to 3.0 μm. When crushed, the fine particles that have formed this enter the gaps between the large particles, so that the density can be easily increased. Moreover, since the granulated particles have a lower hardness than the active material particles, the pressure applied to the electrode foil is reduced by acting like a cushion during pressing. For this reason, even if it does not make press pressure high, an active material layer can be densified and the deformation | transformation of the electrode plate resulting from high press pressure can be suppressed.

  Furthermore, in the battery manufacturing method, the granulation step is a self-supporting granulation step in which the active material particles are aggregated and granulated without applying external force to form the granulated particles. It is good to use the manufacturing method of the battery which is.

The granulated particles formed by forced granulation (compression granulation, extrusion granulation, etc.) that granulate by applying an external force to the active material particles may require a large force to crush. For this reason, it may be necessary to increase the press pressure in the press process.
In contrast, in the battery manufacturing method described above, the granulated particles are formed by self-supporting granulation in which active material particles are aggregated and granulated without applying external force. Since the granulated particles formed by self-supporting granulation can be easily crushed with a small force, the pressing pressure in the pressing process can be particularly lowered. Therefore, deformation of the electrode plate after pressing can be particularly effectively suppressed.
Specific examples of the “self-supporting granulation” include rolling granulation, fluidized bed granulation (spouted bed granulation), stirring and mixing granulation, and the like.

1 is a perspective view of a lithium ion secondary battery according to an embodiment. It is a longitudinal cross-sectional view of the lithium ion secondary battery which concerns on embodiment. It is an expanded view of an electrode body which concerns on embodiment and shows the state which mutually accumulated the positive electrode plate and the negative electrode plate through the separator. It is explanatory drawing which concerns on embodiment and shows the manufacturing process of a positive electrode plate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a lithium ion secondary battery 100 (hereinafter also simply referred to as a battery 100) according to the present embodiment. FIG. 3 shows a state where the wound electrode body 120 constituting the battery 100 is developed. In the following description, the thickness direction BH, the width direction CH, and the height direction DH of the battery 100 are defined as the directions shown in FIGS. 1 and 2 will be described as the upper side of the battery 100, and the lower side will be described as the lower side of the battery 100.

  The battery 100 is a rectangular sealed battery that is mounted on a vehicle such as a hybrid vehicle or an electric vehicle, or a battery-powered device such as a hammer drill. The battery 100 includes a rectangular parallelepiped battery case 110, a flat wound electrode body 120 accommodated in the battery case 110, a positive terminal 150 and a negative terminal 160 supported by the battery case 110, and the like. (See FIGS. 1 and 2). In addition, a non-aqueous electrolyte solution 117 is held in the battery case 110.

  The battery case 110 is made of metal (specifically, aluminum). The battery case 110 includes a box-shaped case main body member 111 that is open only on the upper side, and a case lid member 113 that is welded so as to close the opening 111h of the case main body member 111 (see FIG. 1 and FIG. 1). (See FIG. 2). A non-returnable safety valve 113v is provided in the case lid member 113 in the vicinity of the center in the longitudinal direction (the width direction CH of the battery 100). Further, in the vicinity of the safety valve 113v, a liquid injection hole 113h used for injecting the electrolytic solution 117 into the battery case 110 is provided. The liquid injection hole 113h is hermetically sealed with a sealing member 115.

  Further, in the case lid member 113, in the vicinity of both ends in the longitudinal direction (the width direction CH of the battery 100), a positive terminal (positive terminal member) 150 and a negative terminal that extend from the inside of the battery case 110 to the outside. (Negative electrode terminal member) 160 is fixed. Specifically, these terminals 150 and 160 are connected to the case lid via insulating members 155 and 165 made of resin together with bolts 153 and 163 for fastening connection terminals outside the battery, such as bus bars and crimp terminals. It is fixed to the member 113.

  Next, the electrode body 120 will be described (see FIGS. 2 and 3). The electrode body 120 is housed in the battery case 110 in a state where the electrode body 120 is laid down so that its axis (winding axis) is parallel to the width direction CH of the battery 100 (see FIG. 2). In this electrode body 120, a belt-like positive electrode plate 121 and a belt-like negative electrode plate 131 are overlapped with each other via two belt-like separators 141 and 141 made of a resin porous film (see FIG. 3). It is wound around and compressed into a flat shape. A part of an exposed portion 122m, which will be described later, of the positive electrode plate 121 protrudes from the separators 141 and 141 in a spiral shape to one side AC in the axial direction (upward in FIG. 3, left in FIG. 2). The positive electrode terminal (positive electrode terminal member) 150 is connected (welded). In addition, a part of an exposed portion 132m, which will be described later, of the negative electrode plate 131 protrudes in a spiral shape from the separators 141 and 141 to the other side AD in the axial direction (downward in FIG. 3, rightward in FIG. 2). The negative electrode terminal (negative electrode terminal member) 160 described above is connected (welded).

  The positive electrode plate 121 has a strip-shaped positive electrode foil (electrode foil) 122 made of aluminum as a core material. A part (upward in FIG. 3) of one side FC in the width direction FH of the positive electrode foil 122 is an exposed portion 122m extending in a strip shape in the longitudinal direction EH (left-right direction in FIG. 3). On the other hand, positive electrode active material layers (positive electrode mixture layer, active material layer) 123 extending in a strip shape in the longitudinal direction ET are formed on both main surfaces of the other side FD portion (lower side in FIG. 3) other than the exposed portion 122m. , 123 are formed.

These positive electrode active material layers 123 and 123 are formed of positive electrode active material particles (active material particles) 125, a conductive material 126, and a binder 127. In the present embodiment, the positive electrode active material particles 125 are particles of a lithium / cobalt / nickel / manganese composite oxide (specifically, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ ). The positive electrode active material particles 125 have an average particle diameter of 5.0 to 10.0 μm, and 1.0 to 15.0 wt% of fine particles having a particle diameter of 0.1 to 3.0 μm (specifically, 15. 0 wt%). In this embodiment, carbon black (specifically acetylene black) is used as the conductive material 126, and polyvinylidene fluoride (PVDF) is used as the binder 127. The mixing ratio of the positive electrode active material particles 125, the conductive material 126, and the binder 127 is 90: 5: 5 by weight.

  The negative electrode plate 131 has a strip-shaped negative electrode foil 132 made of copper as a core material. A part of the negative electrode foil 132 in the width direction (downward in FIG. 3) is an exposed portion 132m extending in a strip shape in the longitudinal direction (left-right direction in FIG. 3). On the other hand, negative electrode active material layers (negative electrode mixture layers) 133 and 133 are formed on both main surfaces of the portions other than the exposed portion 132m (upper in FIG. 3) extending in a band shape in the longitudinal direction. These negative electrode active material layers 133 and 133 are made of negative electrode active material particles and a binder. In this embodiment, graphite is used as the negative electrode active material, and PVDF is used as the binder. The mixing ratio of the negative electrode active material particles and the binder is 100: 7 by weight.

Next, a method for manufacturing the battery 100 will be described.
First, manufacture of the positive electrode plate 121 will be described (see FIG. 4). That is, first, positive electrode active material particles 125 are prepared. In the present embodiment, the positive electrode active material particles 125 are lithium / cobalt / nickel / manganese composite oxide particles as described above, and have an average particle diameter of 5.0 to 10.0 μm and a particle diameter of 0.1 to 0.1 μm. It contains 1.0 to 15.0 wt% (specifically 15.0 wt%) of 3.0 μm fine particles.

  In addition, the ratio of the fine particles in the positive electrode active material particles 125 is obtained by the following method. That is, 1.0 g of the positive electrode active material particles 125 is put into water and slowly stirred. Then, this is filtered with a filter (Pall Corporation, PTFE membrane Zeflo 3 μm). After each of the permeate and the residue is dried, the weight after drying is measured, the weight ratio of the permeate in the positive electrode active material particles 125 is determined, and this is used as the ratio of fine particles.

  Next, in the granulation step (self-supporting granulation step) S1, the positive electrode active material particles 125 are granulated to form granulated particles. Specifically, the proportion of fine particles after granulation having a particle size of 0.1 to 3.0 μm in the granulated particles is more than the proportion of fine particles in the positive electrode active material particles 125 (specifically, 15.0 wt%). Low, the proportion of fine particles after granulation in the granulated particles is 10.0 wt% or less (specifically 10.0 wt%), and the proportion of granulated particles having a particle size of 90 μm or less is 99.8 wt% or more. (Specifically, 99.9 wt%) granulated particles are formed.

  The granulated particles are formed by self-supporting granulation in which the positive electrode active material particles 125 are aggregated and granulated without applying an external force, more specifically, rolling granulation. That is, the positive electrode active material particles 125 are supplied onto the rotating plate at a constant supply speed, and N-methyl-2-pyrrolidone containing 10.0 wt% of a binder (specifically PVDF) on the rotating plate ( NMP) suspension is fed (sprayed) at a constant feed rate. As a result, the positive electrode active material particles 125 move radially outward on the rotating plate by the centrifugal force, and the positive electrode active material particles 125 are bonded to each other in a snowball manner and granulated to form granulated particles. . The size / distribution of the granulated particles is adjusted by changing the granulation time or the rotation speed.

The proportion of fine particles after granulation having a particle size of 0.1 to 3.0 μm in the granulated particles is obtained in the same manner as the proportion of fine particles in the positive electrode active material particles 125 described above. However, the value excluding the weight of the binder (PVDF).
The proportion of granulated particles having a particle size of 90 μm or less is obtained using a filter having a mesh size of 90 μm instead of the filter having a mesh size of 3 μm. Alternatively, it can be determined by measuring the particle size distribution of the granulated particles.

  Next, in the positive electrode paste preparation step (paste preparation step) S2, the above-described granulated particles of the positive electrode active material 125, the conductive material 126, and the binder 127 are dispersed in a solvent to prepare a positive electrode paste (electrode paste). To do. Specifically, the granulated particles of the positive electrode active material particles 125, acetylene black (conductive material) 126, and PVDF (binder) 127 are mixed at a weight ratio of 90: 5: 5, and the viscosity is increased with NMP (solvent). A slurry (positive electrode paste) is prepared while adjusting the above. In this embodiment, the viscosity of the positive electrode paste is set to 3000 to 20000 mPa · s.

  Next, in the filter permeation step S3, the positive electrode paste is made of stainless steel (specifically, SUS316) mesh and has a mesh opening of 90 μm to allow natural permeation, thereby removing foreign matters and the like. In this embodiment, the filter permeability of the positive electrode paste at that time was good. In the positive electrode paste prepared using the above-mentioned granulated particles, the number of fine particles (fine particles after granulation) apparently decreases, so the fine particles adhere to the fiber part (steel wire) of the filter. This is because it is possible to suppress the opening of the filter from being reduced and each granulated particle can easily pass through the filter.

  Separately, a strip-like positive electrode foil 122 made of aluminum is prepared. In the coating step in the positive electrode active material layer forming step (active material layer forming step) S4, the positive electrode paste is applied to one main surface of the positive electrode foil 122 by a die coating method, A positive electrode paste layer is formed. Thereafter, in the heating and drying step of the positive electrode active material layer forming step S4, the positive electrode paste layer is heated and dried with hot air while passing through the drying furnace to form the positive electrode active material layer 123. Next, the positive electrode paste is similarly applied to the main surface on the opposite side of the positive electrode foil 122 to form a positive electrode paste layer, which is heated and dried, and is applied to both surfaces of the positive electrode plate 122 (before compression). ) The positive electrode active material layers 123 and 123 are formed (positive electrode active material layer forming step S4).

  Next, in the pressing step S5, the positive electrode active material layers 123 and 123 are pressed with a pressure roll to crush the granulated particles in the positive electrode active material layer 123, and the positive electrode active material layer 123 is compressed. The density is increased to a predetermined density (set to a predetermined thickness). Specifically, the thickness of each of the positive electrode active material layers 123 and 123 was 170 μm. At this time, the granulated particles, particularly the granulated particles formed by self-supporting granulation such as the above-described method, are easily crushed with a small force, and the fine particles generated by the pulverization are relatively large between the positive electrode active material particles. Since it enters the gap, the positive electrode active material layer 123 can be densified with a small pressing pressure. In addition, since the granulated particles have a lower hardness than the positive electrode active material particles 125, the pressure applied to the positive electrode foil 122 is reduced by acting like a cushion during pressing. Therefore, it is possible to suppress deformation such as warping in the positive electrode plate 121 after pressing while having the high-density (compressed) positive electrode active material layers 123 and 123. Thereby, the positive electrode plate 121 is formed (see FIG. 3).

  Separately, the negative electrode plate 131 is manufactured. That is, a strip-shaped negative electrode foil 132 made of copper is prepared. Then, a negative electrode paste containing graphite (negative electrode active material) and PVDF (binder) is applied to one main surface of the negative electrode foil 132 and dried to form a negative electrode active material layer 133. Similarly, the negative electrode paste is applied to the main surface opposite to the negative electrode foil 132 and dried to form the negative electrode active material layer 133. Thereafter, the negative electrode active material layers 133 and 133 are compressed by a pressure roll to increase the density. Thereby, the negative electrode plate 131 is formed (see FIG. 3).

Next, two strip-shaped separators 141 and 141 are prepared, and the above-described positive electrode plate 121 and negative electrode plate 131 are overlapped with each other through the separators 141 and 141 (see FIG. 3). Turn. Thereafter, the electrode body 120 is formed by compressing it into a flat shape.
Separately, a case lid member 113, a positive electrode terminal member 150, a negative electrode terminal member 160, and bolts 153 and 163 are prepared, and these are set in a mold for injection molding. Then, the insulating members 155 and 165 are integrally formed by injection molding, and the positive terminal member (positive terminal) 150 and the negative terminal member (negative terminal) 160 are fixed to the case lid member 113.

Next, the positive electrode terminal 150 and the negative electrode terminal 160 are connected (welded) to the electrode body 120, respectively. Thereafter, the case body member 111 is prepared, the electrode body 120 is accommodated in the case body member 111, and the opening 111 h of the case body member 111 is closed with the case lid member 113. Then, the case main body member 111 and the case lid member 113 are laser-welded (see FIGS. 1 and 2).
Next, the electrolytic solution 117 is injected into the battery case 110 through the injection hole 113h, and the injection hole 113h is hermetically sealed with the sealing member 115. Thereafter, the battery 100 is subjected to initial charging, aging, and various inspections. Thus, the battery 100 is completed.

(Examples and Comparative Examples)
Next, the results of tests performed to verify the effects of the positive electrode plate 121 and the battery 100 manufacturing method according to the embodiment will be described. As Example 1, the positive electrode plate 121 was manufactured by the manufacturing method according to the embodiment. In this manufacturing method, as described above, the proportion of fine particles (particle size 0.1 to 3.0 μm) in the positive electrode active material particles 125 before granulation is 15.0 wt%, and the positive electrode active material after granulation The ratio of the fine particles after granulation (particle size 0.1 to 3.0 μm) in the particles (granulated particles) is 10.0 wt%. Further, the ratio of particles having a particle size of 90 μm or less in the granulated particles is 99.8 wt% or more.

In Example 2, by adjusting the granulation time in the granulation step, the proportion of fine particles after granulation is 0.01 wt%, and the proportion of particles having a particle size of 90 μm or less is 99.8 wt% or more. (See Table 1). Other than that was the same as Example 1 (embodiment).
In Example 3, positive electrode active material particles having a fine particle ratio of 1.0 wt% were used as the positive electrode active material. Then, granulated particles having a proportion of fine particles after granulation of 0.01 wt% and a proportion of particles having a particle size of 90 μm or less were formed to 99.8 wt% or more. Other than that was the same as Example 1.

On the other hand, in Comparative Example 1, positive electrode active material particles having a fine particle ratio of 20.0 wt% were used as the positive electrode active material. Then, granulated particles having a proportion of fine particles after granulation of 10.0 wt% and a proportion of particles having a particle size of 90 μm or less were 99.8 wt% or more. Other than that was the same as Example 1.
In Comparative Example 2, positive electrode active material particles having a fine particle ratio of 0.5 wt% were used as the positive electrode active material. Then, granulated particles having a proportion of fine particles after granulation of 0.01 wt% and a proportion of particles having a particle size of 90 μm or less being 99.8 wt% or more were formed. Other than that was the same as Example 1.
In Comparative Example 3, by adjusting the granulation time, granulated particles having a ratio of fine particles after granulation of 11.0 wt% and a ratio of particles having a particle size of 90 μm or less of 99.8 wt% or more were formed. Other than that was the same as Example 1.

In Comparative Example 5, the positive electrode active material particles 125 similar to those in Example 1 were used, and instead of performing the granulation step, classification treatment was performed to reduce fine particles from the positive electrode active material particles, and the proportion of fine particles after classification treatment Was 0.01 wt%. Specifically, using the above-described classifier, classification was performed under general air conditioning, with the apparatus setting at the time of classification set to a density of 4.9 g / cc, and the classification conditions to 3 μm or less. Other than that was the same as Example 1.
In Comparative Example 4, a part of fine particles of 3 μm or less obtained by classification treatment was mixed with positive active material particles of 3 μm or more obtained by performing the classification treatment of Comparative Example 5, and the proportion of fine particles was reduced to 0. Increased from 0.01 wt% to 10.0 wt%. Other than that was the same as Example 1.

In Comparative Example 6, the same positive electrode active material particles 125 as in Example 1 were used, but a positive electrode paste was prepared without performing granulation and classification. Other than that was the same as Example 1.
In Comparative Example 7, positive electrode active material particles similar to those in Example 3 were used, but a positive electrode paste was prepared without performing granulation and classification. Otherwise, it was the same as Example 3.

  In addition, the viscosity of each positive electrode paste according to Examples 2 and 3 and Comparative Examples 1 to 7 was adjusted to be the same value as the viscosity of the positive electrode paste according to Example 1 (specifically, 3000 mPa · s). . Further, in each pressing step according to Examples 2 and 3 and Comparative Examples 1 to 7, as in the pressing step according to Example 1, the positive electrode active material layer was compressed to a predetermined density (specifically, a thickness of 170 μm). did.

  About each positive electrode paste which concerns on these Examples 1-3 and Comparative Examples 1-7, the filter permeability test was done and filter permeability (L / h) was measured, respectively. Specifically, a filter having a diameter of 200 mm, a depth of 45 mm, and an opening of 90 μm and having a mesh made of stainless steel (SUS316) (sieve, manufactured by ASONE Co., Ltd.) is prepared. ) And allowed to rest for 1 minute. During this time, the volume (L) of the positive electrode paste that passed through the mesh was measured, and the filter permeation amount (L / h) per unit time (h) was calculated. The results are shown in Table 1.

  Further, the amount of warpage (mm / m) was measured for each positive electrode plate after the pressing step according to Examples 1 to 3 and Comparative Examples 1 to 7 (positive electrode plate having an exposed portion 122m extending in a strip shape in the longitudinal direction EH). did. Specifically, the positive electrode plate after the pressing step was cut so that the dimension in the longitudinal direction ET was 1.0 m, and the flat plate was placed on a table. And the curvature amount (bending amount) (mm) of the width direction FH was measured, respectively.

Moreover, the battery for evaluation (18650 type cylindrical battery) was each produced using the positive electrode plate which concerns on Examples 1-3 and Comparative Examples 1-7, the above-mentioned negative electrode plate, etc., About each battery, the following (1) Battery resistance (Ω) was measured by the method described in (5).
(1) First, each battery is placed in an environment of 25 ° C. and charged to a battery voltage value of 4.1 V with a constant current of 1 C by a constant current-constant voltage method, and further charged while maintaining this battery voltage value. Charging was performed until the current value decreased to 0.1C. Thereafter, the battery was discharged to a battery voltage value of 3.0 V with a constant current of 1C. This charge / discharge was repeated three times, and then charged with a constant current of 1 C for 12 minutes to obtain a SOC of 20%.
(2) Each battery was allowed to stand for 30 minutes in an SOC of 20%, and then the battery voltage V1 at this point was measured. Thereafter, each battery was discharged at a constant current of 4 C for 10 seconds, and the reached battery voltage V2 at that time was measured. And voltage change (DELTA) V (4C) = V2-V1 was calculated | required, respectively.

(3) Next, (1) was performed again, and each battery was allowed to stand for 30 minutes in an SOC of 20%, and then the battery voltage V3 at this point was measured. Thereafter, each battery was discharged at a constant current of 3 C for 10 seconds, and the reached battery voltage V4 at that time was measured. And voltage change (DELTA) V (3C) = V4-V3 was calculated | required, respectively.
(4) Next, (1) was performed again, and each battery was allowed to stand for 30 minutes in an SOC of 20%, and then the battery voltage V5 at this point was measured. Thereafter, each battery was discharged at a constant current of 2 C for 10 seconds, and the reached battery voltage V6 at that time was measured. And voltage change (DELTA) V (2C) = V6-V5 was calculated | required, respectively.
(5) Next, based on the results of (2) to (4), a graph is drawn with the horizontal axis representing the current value I during discharge and the vertical axis representing the voltage change ΔV. The slope of the graph is the battery resistance R ( Ω).

  First, as for filter permeability of the positive electrode paste, as can be seen from Table 1, Comparative Examples 1, 3, 4, 6, and 7 had low filter permeability (0.7 to 2.3 L / h). The reason why the filter permeability of the positive electrode paste of Comparative Example 6 was low was that the positive electrode active material particles were neither granulated nor classified, so the positive electrode active material particles contained a large amount of fine particles (15.0 wt%). The positive electrode paste contains a very large amount of fine particles. For this reason, it is considered that the fine particles adhere to the fiber portion of the filter during filter permeation, causing clogging, and the permeability of the filter is lowered.

  Further, the reason why the filter permeability was low in the positive electrode paste of Comparative Example 7 was that the positive electrode active material particles before treatment did not contain so much fine particles of 0.1 to 3.0 μm (1.0 wt%) Since the positive electrode active material particles are not granulated or classified, a large number of particles having a particularly small particle size (close to 0.1 μm) are present in the positive electrode active material particles and the positive electrode paste. For this reason, it is considered that when the filter permeates, particles having a particularly small particle size adhere to the fiber portion of the filter, causing clogging, and the permeability of the filter is lowered.

  Further, the reason why the filter permeability was low in the positive electrode paste of Comparative Example 1 was that the positive electrode active material particles before the treatment contained very many (20.0 wt%) fine particles exceeding 15.0 wt%. For this reason, granulation was carried out to reduce the proportion of fine particles to 10.0 wt%, but there were still many particles with a particularly small particle size (close to 0.1 μm) after granulation. As a result, it is considered that the particles having a particularly small particle size adhere to the fiber portion of the filter and cause clogging, and the permeability of the filter is lowered.

  Further, the reason why the filter permeability of the positive electrode paste of Comparative Example 3 was lowered is that the granulated particles contain very many (11.0 wt%) fine particles after granulation exceeding 10.0 wt%. For this reason, it is considered that the fine particles after granulation adhere to the fiber part of the filter and cause clogging, and the permeability of the filter is lowered.

  Moreover, the reason why the filter permeability was low in the positive electrode paste of Comparative Example 4 was that the proportion of fine particles was reduced to 10.0 wt% by the classification treatment, but the particle size was particularly large compared to the case where the granulation step was performed. Many small particles (close to 0.1 μm) remain. As a result, it is considered that the particles having a particularly small particle size adhere to the fiber portion of the filter and cause clogging, and the permeability of the filter is lowered.

  In contrast, each of the positive electrode pastes of Examples 1 to 3 and Comparative Examples 2 and 5 had good filter permeability and was good (3.0 to 3.4 L / h). The reason why the filter properties of the positive electrode pastes of Examples 1 to 3 and Comparative Example 2 were good was that the proportion of fine particles contained in the positive electrode active material particles before granulation was 15.0 wt% or less, and Fine particles are reduced by granules, and the proportion of fine particles after granulation is 10.0 wt% or less. For this reason, since there are few post-granulation fine particles contained in a positive electrode paste, it was prevented that the fine particles after granulation adhere to the fiber part of a filter and cause clogging. Further, the ratio of particles having a particle size of 90 μm or less after granulation is set to 99.8 wt% or more. For this reason, since most of the granulated particles are smaller than the opening of the filter (90 μm), a decrease in filter permeability due to large particles was also prevented. As a result, it is considered that the filter permeability is improved.

  Moreover, the reason why the filter permeability of the positive electrode paste of Comparative Example 5 was good was that the fine particles contained in the positive electrode active material particles were almost removed by the classification treatment, and was 0.01 wt%. As described above, since the fine particles contained in the positive electrode paste are few, it is considered that the fine particles are prevented from adhering to the fiber portion of the filter and causing clogging, and the filter has improved permeability.

  Next, the amount of warpage of the positive electrode plate after the pressing process will be examined. As can be seen from Table 1, each positive electrode plate of Comparative Examples 2 and 4 to 7 had a large amount of warpage (1.6 to 2.4 mm / m). Among these, the reason for the large amount of warpage in the positive electrode plate of Comparative Example 2 is that the fine particles contained in the original positive electrode active material particles are less than 1.0 wt% (0.5 wt%). For this reason, in a positive electrode active material layer, there are few fine particles which can enter in the clearance gap between large particles. Therefore, unless the press pressure is increased, the positive electrode active material layer cannot be compressed to a predetermined density. As a result, it is considered that the portion of the positive electrode foil 122 where the positive electrode active material layer was formed was rolled stronger than the exposed portion 122m, and the amount of warpage of the positive electrode plate was increased.

  Further, the reason why the amount of warpage was increased in the positive electrode plate of Comparative Example 5 was that the proportion of fine particles contained in the positive electrode active material particles was significantly reduced by classification (0.01 wt%). The number of fine particles that can enter the gaps between them has decreased. For this reason, it is considered that the press pressure for compressing the positive electrode active material layer to a predetermined density has increased, and the amount of warpage of the positive electrode plate has increased.

  In addition, the reason why the amount of warpage of the positive electrode plate in Comparative Examples 4, 6, and 7 is large is that the positive electrode active material particles themselves have higher hardness than the granulated particles. The pressure applied to the positive electrode foil 122 (the portion where the positive electrode active material layer is formed) increases. For this reason, it is considered that the amount of warping of the positive electrode plate after pressing has increased.

  In contrast, each of the positive plates of Examples 1 to 3 and Comparative Examples 1 and 3 had a small amount of warpage (0.15 to 0.3 mm / m). The reason is that the amount of fine particles contained in the positive electrode active material particles before treatment is larger than 1.0 wt%, and after the granulated particles are crushed by the press, the fine particles enter the gaps between the large particles. The density can be easily increased. In addition, since the granulated particles have a lower hardness than the positive electrode active material particles, the pressure applied to the positive electrode foil 122 (the portion where the positive electrode active material layer is formed) is reduced by acting like a cushion during pressing. For this reason, it is considered that the positive electrode active material layer could be compressed to a predetermined density without increasing the press pressure, and the amount of warpage of the positive electrode plate was small.

Next, battery resistance will be examined. As can be seen from Table 1, the batteries according to Comparative Examples 2 and 4 to 7 in which the amount of warpage of the positive electrode plate after pressing was large also had a large battery resistance (150 to 176Ω). The reason is considered to be that the positive electrode active material particles themselves were cracked by the press due to the high press pressure, and the battery resistance was increased.
In contrast, the batteries according to Examples 1 to 3 and Comparative Examples 1 and 3 in which the amount of warpage of the positive electrode plate after pressing was small also had a small battery resistance (120 to 124Ω). The reason for this is that since the pressing pressure was low, even if the granulated particles were crushed by the press, the positive electrode active material particles themselves were rarely cracked. For this reason, it is thought that battery resistance was small.

  As described above, the positive electrode active material particles 125 containing 1.0 to 15.0 wt% of fine particles having a particle size of 0.1 to 3.0 μm are used as the positive electrode active material. In the granulation step, the proportion of fine particles after granulation having a particle size of 0.1 to 3.0 μm in the granulated particles is lower than the proportion of fine particles in the positive electrode active material particles 125, and granulation in the granulated particles. A granulated particle is formed in which the proportion of the post-fine particles is 10.0 wt% or less and the proportion of the granulated particles having a particle size of 90 μm or less is 99.8 wt% or more. In the positive electrode paste prepared using the granulated particles, there are apparently fewer fine particles (fine particles after granulation) than before granulation. Can be good. In addition, since there are almost no large granulated particles having a particle size of more than 90 μm in the electrode paste, large foreign matters can be easily removed from the electrode paste without causing clogging of the filter by the large particles.

  Further, the positive electrode active material layer 123 formed of the positive electrode paste using the granulated particles described above requires a small pressing pressure to increase the density of the positive electrode active material layer 123 in the pressing step, and the positive electrode foil 122 The pressure applied to can be reduced. Therefore, it is possible to suppress deformation such as warpage in the positive electrode plate 121 after pressing. In addition, by reducing the pressing pressure, the positive electrode active material particles 125 themselves are difficult to break during pressing, and thus an increase in battery resistance due to cracking of the positive electrode active material particles 125 can be prevented. In particular, in this embodiment, the granulated particles are formed by self-supporting granulation in which the positive electrode active material particles 125 are aggregated and granulated without applying external force. For this reason, since the granulated particles can be easily crushed with a small force, the pressing pressure in the pressing step can be particularly lowered.

In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, in the embodiment, the present invention is applied to the formation of the positive electrode plate 121, but the present invention may be applied to the formation of the negative electrode plate 131.
In the embodiment, a filter made of a metal mesh is used as a filter used in the filter process, but the present invention is not limited to this. For example, a filter made of a resin mesh such as nylon or a nonwoven fabric may be used.

100 Lithium ion secondary battery (battery)
120 Electrode body 121 Positive electrode plate (electrode plate)
122 Positive electrode foil (electrode foil)
123 Positive electrode active material layer (positive electrode mixture layer, active material layer)
125 Positive electrode active material particles (active material particles)
126 Conductive Material 127 Binder 131 Negative Electrode Plate 141 Separator

Claims (3)

A method for producing a battery comprising an electrode plate having an active material layer formed on an electrode foil,
A granulation step of granulating active material particles containing 1.0 to 15.0 wt% of fine particles having a particle size of 0.1 to 3.0 μm to form granulated particles,
The granulated particles are
The proportion of fine particles after granulation having a particle size of 0.1 to 3.0 μm in the granulated particles is lower than the proportion of the fine particles in the active material particles,
The proportion of fine particles after granulation in the granulated particles is 10.0 wt% or less, and
A proportion of the granulated particles having a particle size of 90 μm or less is 99.8 wt% or more;
Using the granulated particles, a paste creating step for creating an electrode paste,
About the electrode paste, a filter permeation step for allowing a filter having an opening of 90 to 110 μm to pass through,
An active material layer forming step of forming the active material layer by applying the electrode paste after the filter permeation step onto the electrode foil and drying it. A battery manufacturing method according to claim 1, comprising:
After the said active material layer formation process, the said active material layer is pressed, The manufacturing method of a battery provided with the press process of compressing the said active material layer while crushing the said granulated particle. A method of manufacturing a battery according to claim 2,
The granulation step includes
A battery manufacturing method, which is a self-supporting granulation step of forming the granulated particles by self-supporting granulation in which the active material particles are aggregated and granulated without applying external force.

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