JP2013004355A - Method for manufacturing battery - Google Patents

Abstract

A battery manufacturing method capable of manufacturing a battery provided with a high-quality electrode is provided.
[Solution]
In the battery manufacturing method according to the present invention, a paste raw material containing an active material, a binder, and a solvent is placed in a stirring tank 12, and the contents of the stirring tank 12 are stirred to prepare an active material layer forming paste. A step of applying an active material layer forming paste to a current collector to obtain an electrode having an active material layer formed on the current collector, and a step of constructing a battery using the obtained electrode; Is included. In the stirring step, a partial stirring member 14 that partially stirs the contents of the stirring tank in a part of the stirring tank 12 is used, and the contents in the vicinity of the surface of the partial stirring member 14 are stirred while being locally heated. .
[Selection] Figure 2

Description

  The present invention relates to a battery manufacturing method, and more particularly to a battery manufacturing method including a step of preparing an active material layer forming paste.

  In recent years, lithium secondary batteries, nickel hydride batteries, and other secondary batteries have been used as power sources for mounting on vehicles or as power sources for personal computers and portable terminals. In particular, a lithium secondary battery that is lightweight and has a high energy density is gaining importance as a high-output power supply for vehicles.

  One typical configuration of a lithium secondary battery includes an electrode having a configuration in which a material (electrode active material) capable of reversibly occluding and releasing lithium ions is held by a conductive member (electrode current collector). As a typical example of an electrode active material (positive electrode active material) used for the positive electrode, an oxide containing lithium and one or more transition metal elements as constituent metal elements (hereinafter also referred to as “lithium transition metal oxide”). .). A typical example of an electrode current collector (positive electrode current collector) used for the positive electrode is a sheet-like or foil-like member mainly composed of aluminum or an aluminum alloy. Such a positive electrode for a battery is, for example, a paste-like or ink-like composition containing a positive electrode active material, a binder, and a solvent (hereinafter, such a suspension-like composition is simply referred to as “paste”). An active material layer forming paste is prepared, applied to a current collector, and dried. The active material layer forming paste is prepared, for example, by stirring the positive electrode active material, the binder, and the solvent with a stirrer having a high shearing force. Moreover, as a solvent of the active material layer forming paste, for example, an organic solvent such as N-methylpyrrolidone (NMP) can be used. Patent document 1 is mentioned as a prior art regarding manufacture of this kind of electrode.

JP 2010-1114030 A

  When using an organic solvent such as NMP as the solvent for the active material layer forming paste, it is desired to reduce the amount of the organic solvent used (in other words, increase the solid content concentration of the paste) from the viewpoint of reducing the environmental burden. Has been. Even when using an aqueous solvent instead of an organic solvent as the solvent, the aqueous solvent is inferior in terms of drying compared to the organic solvent, so the solid content concentration of the paste must be increased in order to increase the drying speed. Is required. However, when the solid content concentration of the paste is increased, the viscosity of the paste increases. Therefore, when the paste is stirred using a stirring device, the viscosity is too high to cause mixing and dispersion. For example, depending on the stirring device, there may be a configuration in which the stirring member is partially disposed in the stirring tank. When such a stirring device is used, shear energy is not transmitted to the paste existing in a region away from the stirring member due to an increase in paste viscosity, and there is a possibility that sufficient share is not applied to the stirring target. The present invention solves the above problems.

  The battery manufacturing method according to the present invention comprises a stirring step of preparing a paste for forming an active material layer by storing a paste raw material containing an active material, a binder, and a solvent in a stirring tank and stirring the contents of the stirring tank. Include. In addition, the method includes a step of applying the active material layer forming paste to a current collector to obtain an electrode having an active material layer formed on the current collector. Furthermore, a step of constructing a battery using the obtained electrode is included. In the stirring step, a partial stirring member that partially stirs the contents of the stirring tank in a part of the stirring tank is used, while locally heating the contents in the vicinity of the surface of the partial stirring member. It is characterized by stirring.

  According to the battery manufacturing method of the present invention, a partial stirring member that partially stirs the contents of the stirring tank in a part of the stirring tank is used, and the contents near the surface of the partial stirring member are locally heated. Since stirring is performed while the paste raw material in the vicinity of the surface of the partial stirring member is locally warmed, the viscosity is lowered and the fluidity during stirring is increased. Therefore, the stirred paste raw material actively flows to a part away from the partial stirring member without staying around the partial stirring member. This makes it possible to apply a share (for example, shearing force) to the paste raw material existing in a region away from the partial stirring means, and improve the dispersion efficiency.

  In a preferable aspect of the battery manufacturing method disclosed herein, the heating is performed so that the temperature of the content in contact with the partial stirring member is 40 ° C to 60 ° C. If the temperature range is too low, the above-described dispersion efficiency improvement effect due to local heating tends to be low. On the other hand, if the temperature range is too high, volatilization of the solvent in the paste raw material proceeds, and the binder May easily precipitate.

  In a preferred embodiment of the battery manufacturing method disclosed herein, a heating wire attached to the partial stirring member is used as the heating means. According to this configuration, the contents near the surface of the partial stirring member can be efficiently warmed by heat transfer from the partial stirring member heated by the heating wire. Alternatively, as the means for heating, a method of irradiating and heating the contents with infrared rays may be used. By irradiating and heating infrared rays, the contents near the surface of the partial stirring member can be heated uniformly. Alternatively, as the means for heating, a method of irradiating and heating the contents with ultrasonic waves may be used. By irradiating and heating ultrasonic waves, the contents near the surface of the partial stirring member can be easily warmed.

  In a preferable embodiment of the battery manufacturing method disclosed herein, when the paste raw material is stored in the stirring tank, first, the binder and the solvent are stored before the active material. And after starting the local heating of the content of the surface vicinity of the said partial stirring member, the said active material is accommodated. According to such a configuration, the heating is performed in a state where the active material having a large heat capacity and hardly warms is removed, so that the contents near the surface of the partial stirring member can be efficiently heated.

  In a preferable embodiment of the battery manufacturing method disclosed herein, the solid content concentration of the paste raw material is 50% by mass or more. In the case where the solid content concentration of the paste raw material is 50% by mass or more, there is an advantageous effect that the drying speed is increased, while the viscosity tends to increase and the dispersion efficiency during stirring tends to decrease. It is particularly useful to apply

In a preferred embodiment of the battery manufacturing method disclosed herein, the electrode is a positive electrode, and the paste material includes carbon as a conductive material. When carbon as a conductive material is included in the paste raw material, the lack of electrical conductivity of the active material is resolved and the battery performance is improved, while the viscosity tends to increase and the dispersion efficiency during stirring tends to decrease. It is particularly useful to apply the present invention.
In a preferred embodiment of the battery manufacturing method disclosed herein, a polyvinylidene fluoride resin is used as the binder.

  The battery constructed using the active material layer forming paste thus obtained is suitable as a battery mounted on a vehicle such as an automobile. Therefore, according to the present invention, there is provided a vehicle including any of the batteries disclosed herein (which may be in the form of an assembled battery in which a plurality of batteries are connected). In particular, since the light weight and high output can be obtained, the battery is a lithium secondary battery (typically a lithium ion secondary battery), and the lithium secondary battery is used as a power source (typically a hybrid vehicle). A vehicle (for example, an automobile) provided as a power source of an electric vehicle is preferable.

It is a figure which shows the manufacture flow of the electrode which concerns on one Embodiment of this invention. It is a figure which shows typically the stirring apparatus used for one Embodiment of this invention. It is a figure which shows typically the stirring apparatus used for one Embodiment of this invention. It is a figure which shows typically the stirring apparatus used for one Embodiment of this invention. It is a figure which shows typically the example of 1 structure of a lithium secondary battery. It is a graph which shows the relationship between the temperature of the heating part which concerns on one test example, and paste viscosity. It is a graph which shows the relationship between the temperature of the heating part which concerns on one test example, and a particle size. It is a figure which shows typically the laminate cell which concerns on one test example. It is a graph which shows IV resistance and paste viscosity which concern on one test example. It is a side view which shows the vehicle carrying a battery.

  Embodiments according to the present invention will be described below with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, matters other than those particularly mentioned in the present specification and matters necessary for the implementation of the present invention (for example, general methods related to the manufacturing method of electrode active materials, the configuration and manufacturing method of separators and electrolytes, and the construction of batteries) Technical technology etc.) can be understood as a design matter of those skilled in the art based on the prior art in the field.

  An electrode according to an embodiment of the present invention and a battery manufacturing method including the electrode will be described with reference to FIG. FIG. 1 is a flowchart showing the overall flow of an electrode manufacturing process included in the battery manufacturing process.

The battery manufacturing method disclosed herein includes a stirring process (step S10) and a coating process (step S20). The stirring step includes preparing a paste for forming an active material layer by stirring a paste material containing an active material, a binder, and a solvent with a stirring member in a stirring tank. Further, the coating step includes applying an active material layer forming paste to a current collector to obtain an electrode having an active material layer formed on the current collector.
Although not intended to be particularly limited, in the following, each step will be described in detail, taking as an example a positive electrode (positive electrode sheet) for a lithium secondary battery mainly having an aluminum foil-shaped positive electrode current collector (Al foil). explain.

  The stirring process of step S10 is a process of preparing a paste for forming a positive electrode active material layer by storing a paste raw material containing at least a positive electrode active material, a binder, and a solvent in a stirring tank and stirring the paste raw material in the stirring tank. is there.

As a positive electrode active material used for the paste raw material of the battery manufacturing method disclosed here, one or more kinds of materials conventionally used for lithium secondary batteries can be used without particular limitation. As a preferable application object of the technology disclosed herein, lithium and one kind of lithium nickel oxide (for example, LiNiO ₂ ), lithium cobalt oxide (for example, LiCoO ₂ ), lithium manganese oxide (for example, LiMn ₂ O ₄ ) or the like A positive electrode active material mainly containing an oxide (lithium transition metal oxide) containing two or more transition metal elements as constituent metal elements can be given. Preferably, the lithium transition metal oxide contains at least one metal element of nickel, cobalt, and manganese. Among them, a positive electrode active material (typically substantially, mainly composed of lithium nickel cobalt manganese oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) containing nickel, cobalt, and manganese) Application to a positive electrode active material made of lithium nickel cobalt manganese oxide is preferable.

  Here, the lithium nickel cobalt manganese oxide is an oxide having Li, Ni, Co, and Mn as constituent metal elements, and at least one other metal element in addition to Li, Ni, Co, and Mn (that is, Li , Ni, Co, and transition metal elements other than Mn and / or oxides containing typical metal elements). The metal element is, for example, one or two selected from the group consisting of Al, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. It can be more than a seed element. The same applies to lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide.

  As such a lithium transition metal oxide (typically in particulate form), for example, a lithium transition metal oxide powder prepared by a conventionally known method can be used as it is. For example, the volume-based average particle diameter (D50) based on the laser diffraction / scattering method is substantially constituted by secondary particles in the range of about 1 μm to 25 μm (preferably 1 μm to 10 μm, more preferably 4 μm to 6 μm). Lithium transition metal oxide powder can be preferably used as the positive electrode active material.

  The material itself constituting the binder used in the battery manufacturing method disclosed herein may be the same material as that used for a conventionally known positive electrode for a lithium secondary battery. For example, when the positive electrode active material layer forming paste is an organic solvent-based composition (a composition in which the binder dispersion medium is mainly an organic solvent), a polymer that is dispersed or dissolved in the solvent-based solvent may be used. it can. Examples of the polymer that is dispersed or dissolved in the organic solvent include polyvinylidene fluoride (PVdF) resin. As the polyvinylidene fluoride resin, a homopolymer of vinylidene fluoride is preferably used. Furthermore, as the polyvinylidene fluoride resin, a copolymer of a vinyl monomer copolymerizable with vinylidene fluoride is also preferably used. Examples of vinyl monomers copolymerizable with vinylidene fluoride include hexafluoropropylene, tetrafluoroethylene, and ethylene trichloride fluoride. Alternatively, polytetrafluoroethylene (PTFE), polyacrylonitrile, polymethyl methacrylate, or the like is preferably used as a polymer that is dispersed or dissolved in an organic solvent. Further, when the positive electrode active material layer forming paste is an aqueous composition (a composition using water or a mixed solvent containing water as a main component as a binder dispersion medium), the binder is dispersed in water or Soluble polymers can be preferably employed. Examples of the polymer dispersed or dissolved in water include styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), polyethylene (PE), polyacrylic acid (PAA), and the like. .

  The solvent used for the paste raw material of the battery manufacturing method disclosed herein can be used without particular limitation as long as it can disperse the above-described positive electrode active material and binder. Examples thereof include organic solvents such as N-methylpyrrolidone (NMP), pyrrolidone, methyl ethyl ketone, methyl isobutyl ketone, ixahexanone, toluene, dimethylformamide, dimethylacetamide, and combinations of two or more thereof. Alternatively, water or a mixed solvent mainly composed of water may be used. As a solvent other than water constituting such a mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used.

  In addition to the positive electrode active material, binder and solvent described above, the paste raw material optionally contains one or more materials that can be used as a component of the positive electrode active material layer in a general lithium secondary battery. can do. An example of such a material is a conductive material. As the conductive material, a carbon material such as carbon powder or carbon fiber is preferably used. Alternatively, conductive metal powder such as nickel powder may be used. In this embodiment, the paste raw material contains, for example, acetylene black (AB) powder having a volume-based average particle diameter (D50) based on a laser diffraction / scattering method of 1 μm to 3 μm. The content ratio of the conductive material is not particularly limited, but from the viewpoint of achieving high output that can also be used for vehicle power sources and the like, 5% by mass to 20% by mass with respect to the total solid content of the paste raw material, Is preferably 10% by mass to 20% by mass. In addition, examples of the material that can be used as a component of the positive electrode active material layer include various materials that can function as a dispersant for the constituent material in the active material layer forming paste. Examples of the dispersant include polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA).

  The ratio of the solid content in the paste raw material (solid content concentration of the positive electrode active material layer forming paste) is not particularly limited, but is approximately 50% by mass or more, preferably 50 to 70% by mass, More preferably, it is 52-70 mass%, More preferably, it is 54-70 mass%, Most preferably, it is 58-70 mass%. The paste raw material is stirred with a stirring device shown in FIG. 2 to prepare a positive electrode active material layer forming paste.

  An example of a stirring device used in the battery manufacturing method disclosed herein is shown in FIG. As shown in FIG. 2, the stirring device 10 includes a stirring tank 12, a partial stirring member 14, and a heating means 18. The agitation tank 12 is a container for containing a paste raw material. The shape of the stirring tank 12 is not particularly limited. For example, it may be substantially cylindrical with a bottom.

  The partial stirring member 14 is configured to partially stir the contents of the stirring tank 12. Here, as shown in FIG. 2, an example is shown in which a rotary stirring blade 14 is employed as the partial stirring member 14. As the stirring blade 14, it is preferable to use a stirring blade capable of giving a strong shearing force, such as a disper blade or a turbine blade. In this embodiment, it is a disper blade 14. In addition, this structure is applicable not only to the stirring blade 14 but all the stirring members which can partially stir the contents of the stirring tank 12 in a part of the stirring tank 12, It doesn't matter. For example, a vibration type stirring member (for example, an ultrasonic vibrator) may be employed.

  The heating means 18 is configured to locally heat the contents near the surface of the partial stirring member (disper blade) 14. In this embodiment, the heating means 18 is a heating wire 18 </ b> A attached to the disper blade 14. As shown in FIG. 2, the heating wire 18 </ b> A may be wound around the outer surface of the disper blade 14, or may be disposed at a distance (so as to surround the disper blade 14) so as not to contact the disper blade 14. Good. In this embodiment, the heating wire 18A is spirally wound around the disper blade 14.

  In the stirring apparatus 10 having such a partial stirring member 14 and the heating means 18, the paste raw material in the vicinity of the surface of the partial stirring member 14 is stirred by the heating means 18 while being locally heated. By stirring the paste raw material in the vicinity of the surface of the partial stirring member 14 while locally heating, the paste raw material in the vicinity of the surface of the partial stirring member 14 is locally warmed to reduce the viscosity and increase the fluidity during stirring. . Therefore, the stirred paste raw material does not stay around the partial stirring member 14 and actively flows to a part away from the partial stirring member 14 (for example, near the inner wall surface of the stirring tank 12). This makes it possible to give a share (for example, shearing force) to the raw material paste present in a region away from the partial stirring means 14. As a result, the entire contents of the agitation tank 12 can be efficiently shared, and the dispersion efficiency is improved.

  Since the paste raw material containing the positive electrode active material, the binder, the conductive material, and the solvent used in the battery manufacturing method disclosed herein has a high viscosity when the solid content concentration is increased, the conventional stirring device has a high viscosity. Thus, there is a problem that mixing and dispersion does not proceed (the stirred paste raw material does not flow, and the paste raw material separated from the partial stirring member does not have a sufficient share). On the other hand, in the stirring device 10 according to the present embodiment, a strong shearing force is applied even to the paste raw material separated from the partial stirring member 14, so that the positive electrode active material and the binder are reliably dispersed in the solvent and the partial stirring is performed. Even in the paste raw material away from the member 14, the solid particles (aggregates) are further refined. Therefore, a positive electrode active material layer forming paste having a small solid particle size and good dispersibility can be prepared.

  The partial stirring member 14 used for the battery manufacturing method disclosed here is, for example, a disper blade. Here, the disper blade means a blade having a disk-shaped rotary blade with a saw-shaped blade standing above and / or below the outer periphery of the disk. The disper blade 14 includes a shaft portion 14A connected to a rotation driving means such as a motor (not shown), and a rotating blade 14B rotatably supported by the shaft portion 14A. The diameter of the rotary blade 14 </ b> B preferably occupies 10% to 30% with respect to the inner diameter of the stirring tank 12. The disperse blade 14 has a rotational speed higher than that of the anchor blade 16 described later, and the positive electrode active material and the binder are mixed and dispersed in the solvent by the shearing force generated by the high-speed rotation, and the solid particles in the paste raw material (Typically, the positive electrode active material and the binder agglomerates) are refined.

  The stirring device 10 used in the battery manufacturing method disclosed herein includes an overall stirring member 16 in addition to a disper blade (partial stirring member) 14. The entire stirring member 16 is configured to stir the contents of the stirring tank 12 throughout. The whole stirring member 16 may be any stirring member as long as it can stir the entire contents of the stirring tank 12 and does not come into contact with the disper blade 14. In this embodiment, it is an anchor wing 16. The anchor blade 16 includes a shaft portion 16A provided on the central axis of the stirring tank 12, and a rotary blade 16B that is rotatably supported by the shaft portion 16A. The rotary blade 16 </ b> B is provided along the inner wall of the stirring tank 12. The anchor blade 16 has a rotational speed lower than that of the disper blade 14 and agitates the entire contents of the agitation tank 12 by the swirling flow generated by the low-speed rotation. Note that the entire stirring member 16 is not limited to the above-described anchor blade. For example, it is good also as a structure which moves stirring tank 12 itself (for example, stirring tank 12 itself rotates) without using a wing | blade.

  The rotational direction of the disperse blade 14 and the anchor blade 16 may be the same direction or the opposite direction, but from the viewpoint of reducing the load on the disper blade 14, the same direction is preferable. In a preferred embodiment, the disper blade 14 is disposed at a position displaced from the central axis of the stirring tank 12. In this embodiment, the disper blade 14 is displaced from the central axis of the stirring tank 12 and is disposed between the shaft portion 16A of the anchor blade 16 and the rotary blade 16B. By disposing the disper blade 14 at a position displaced from the central axis of the stirring tank 12 in this way, a shearing force can be efficiently applied to the contents of the stirring tank 12. The insertion position of the disperse blade 14 with respect to the liquid surface of the rotary blade 14B is not particularly limited. However, if it is too close to the liquid surface, there is a possibility that bubbles may be mixed in, and if it is too far from the liquid surface, it may interfere with the rotation of the anchor blade 16. possible. Therefore, it is preferable that the insertion position of the disperse blade 14 with respect to the liquid surface of the rotary blade 14 </ b> B is approximately between the liquid surface and the rotary blade 16 </ b> B of the anchor blade 16.

  Although the rotational speed of the disper blade 14 is not particularly limited, it is usually appropriate to set it to about 3000 rpm or more, for example, 4000 rpm or more (for example, 4000 rpm to 6000 rpm), for example, about 5000 rpm is preferable. Although the rotation speed of the anchor blade 16 is not particularly limited, it is usually smaller than the rotation speed of the disperse blade 14 and 30 rpm or more (for example, 30 rpm to 100 rpm), preferably 40 rpm to 60 rpm.

  In the preferred technique disclosed here, after the paste raw material is stored in the stirring tank 12, only the anchor blade 16 is first rotated at a low speed (for example, 50 rpm) to gently stir the entire paste raw material. The paste raw material is partially vigorously stirred by rotating the blade 14 at a high speed (for example, 5000 rpm). Thus, by gently stirring only with the anchor blade 16 at first, there is an advantage that the powder such as the positive electrode active material and the solvent can be sufficiently blended, and the subsequent intense stirring can be stably performed.

  The heating means 18 used in the battery manufacturing method disclosed here is a heating wire 18 </ b> A attached to the disper blade 14. The heating wire 18 </ b> A is preferably wound around the outer surface of the disper blade 14. In this case, by causing current to flow through the heating wire 18A to generate heat, the paste raw material near the surface of the disper blade 14 is heated, and at the same time, the disper blade 14 itself is heated. Therefore, the paste raw material in the vicinity of the surface of the disper blade 14 can be warmed more efficiently by utilizing the heat transfer from the heated disper blade 14. The heating wire 18 </ b> A may be arranged at a distance (so as to surround the disper blade 14) so as not to contact the disper blade 14. According to this configuration, since the heating wire 18A and the disper blade 14 do not contact, the disper blade 14 can be rotated without being obstructed by the heating wire 18A.

  The heating temperature by the heating wire 18A is not particularly limited, but the heating is preferably performed so that the temperature of the paste raw material (content) in contact with the disper blade 14 is 40 ° C to 60 ° C. If the temperature of the paste raw material in contact with the disper blade 14 is too low, the effect of improving the dispersion efficiency by local heating around the disper blade 14 tends to be low. From the viewpoint of improving the dispersion efficiency, the temperature of the paste raw material in contact with the disper blade 14 is suitably 40 ° C. or higher, preferably 45 ° C. or higher, and particularly preferably 50 ° C. or higher. However, if the temperature becomes too high, the solvent in the paste material evaporates and the binder may be easily deposited. From the viewpoint of suppressing the volatilization of the solvent, approximately 60 ° C. or less (eg, 40 ° C. to 60 ° C.) is appropriate, preferably 55 ° C. (eg, 40 ° C. to 55 ° C.) or less, and particularly preferably 50 ° C. or less (eg, 40 ° C. to 50 ° C.).

  In the above-described embodiment, the case where the heating wire 18A is used as the heating unit 18 is illustrated, but the heating unit 18 is not limited thereto. For example, as shown in FIG. 3, a method of heating by applying ultrasonic waves may be used. In the illustrated example, an ultrasonic wave generator 18B is provided around the shaft portion 14A of the disper blade 14. The ultrasonic generator 18B irradiates ultrasonic waves toward the shaft portion 14A, and ultrasonically vibrates the paste material near the surface of the shaft portion 14A. The paste raw material can be warmed by the heat of internal friction generated during the ultrasonic vibration. The frequency of the ultrasonic wave to be irradiated is not particularly limited, but is typically about 10 kHz to 100 kHz, and preferably about 10 kHz to 30 kHz.

  Or as shown in FIG. 4, the system which irradiates and heats infrared rays from the exterior of the stirring tank 12 can also be used. In the illustrated example, an infrared ray generator 18 </ b> C is provided outside the stirring tank 12 and above the disper blade 12. The infrared ray generator 18C locally heats the paste material in the vicinity of the surface of the disper blade 14 by irradiating infrared rays toward the disper blade 14. As an infrared ray irradiated, any of near infrared rays, middle infrared rays, and far infrared rays may be sufficient. The heating means described above may be used alone or in combination of two or more.

  A positive electrode active material supply port 11 </ b> A and a binder solution supply port 11 </ b> B are provided in the upper part of the stirring tank 12 used in the battery manufacturing method disclosed herein. The positive electrode active material supply port 11A is a portion to which a positive electrode active material is supplied, and is connected to a positive electrode active material supply device (not shown). The binder solution supply port 11B is a portion to which the binder solution is supplied and is connected to a binder solution supply device (not shown). Here, the binder solution is obtained by mixing and dispersing a binder and a solvent, and may contain a positive electrode active material layer forming component other than the positive electrode active material (for example, a conductive material such as AB) as necessary.

  When the paste raw material is accommodated in the agitation tank 12, first, the binder solution is supplied from the binder solution supply port 11B while locally heating the vicinity of the disper blade 14 by the heating means 18. At this time, the binder solution is preferably supplied so as to pass through a portion heated by the heating means 18 (here, along the shaft portion 14A of the disper blade 14). When a predetermined amount of the binder solution is accommodated in the stirring tank 12, the anchor blade 16 is rotated by rotating the shaft portion 16A by a rotation driving means such as a motor, and the positive electrode active material is supplied from the positive electrode active material supply port 11A. Supply. That is, in this embodiment, the binder and the solvent are accommodated before the positive electrode active material, and after the local heating in the vicinity of the surface of the disper blade 14 by the heating means 18 is started, the positive electrode active material is accommodated. . Thus, by starting local heating before accommodating a positive electrode active material, the said heating is performed in the state except the positive electrode active material with a large heat capacity which is hard to warm. Therefore, the contents (here, the binder solution) in the vicinity of the surface of the disper blade 14 can be efficiently warmed. When a predetermined amount of the positive electrode active material is accommodated in the stirring vessel 12, the disperse blade 14 is rotated by rotating the shaft portion 14A by a rotation driving means such as a motor while continuing to rotate the anchor blade 16. In this way, the stirring process according to the present embodiment is started.

  In the stirring step according to the present embodiment, the paste raw material containing the positive electrode active material, the binder, and the solvent is partially heated by the heating means 18 in the stirring tank 12 provided in the stirring device 10 having the partial stirring means 14 and the heating means 18. The paste raw material near the surface of the stirring means 14 is stirred while locally heating. Therefore, the dispersion efficiency is improved as compared with the conventional case, and a positive electrode active material layer forming paste in which the positive electrode active material and the binder are uniformly dispersed in the solvent can be obtained efficiently. Such a paste for forming a positive electrode active material layer does not increase the viscosity so much even if the solid content concentration is increased. Therefore, it can have a high solid content and a low viscosity. For example, using a commercially available E-type viscometer, the viscosity of the positive electrode active material layer forming paste when the liquid temperature is adjusted to 25 ° C. and measured by rotating the rotor at 1 rpm is approximately 7000 mPa · s or less. Yes, preferably 5000 mPa · s or less, more preferably 4000 mPa · s or less, and particularly preferably 3000 mPa · s or less. The lower limit of the viscosity of the paste is not particularly limited, but if the viscosity is too low, the paste may sag when applied to the current collector. From the viewpoint of making the viscosity suitable for coating, it is generally 2000 mPa · s or more. The positive electrode active material layer forming paste having such a viscosity range has good handleability and good coating property when the paste is applied to a positive electrode current collector to form an electrode.

  As a suitable example of the positive electrode active material layer forming paste disclosed here, the viscosity of the paste is 2000 mPa · s to 7000 mPa · s and the solid content is in the range of 50 to 70 mass%, the viscosity of the paste Is 2000 mPa · s to 5000 mPa · s or less and the solid content is in the range of 52 to 70% by mass, the paste has a viscosity of 2000 mPa · s to 4000 mPa · s and the solid content is 54 to 70% by mass. Examples thereof include those in the range of 70% by mass, those in which the viscosity of the paste is 2000 mPa · s to 3000 mPa · s and the solid content is in the range of 58 to 70% by mass. By having both the viscosity and the solid content ratio within the predetermined range, a positive electrode active material layer forming paste satisfying both good coatability and high drying efficiency that could not be obtained conventionally. be able to.

  After the positive electrode active material layer forming paste is formed in this way, the positive electrode active material layer forming paste is then applied on the positive electrode current collector and dried (the coating step in step S20 in FIG. 1).

  The operation of applying the positive electrode active material layer forming paste to the positive electrode current collector can be performed in the same manner as in the case of producing a conventional positive electrode for a lithium secondary battery. For example, by using a suitable coating apparatus (die coater, slit coater, comma coater, etc.), a predetermined amount of the positive electrode active material layer forming paste is applied to the positive electrode current collector to a uniform thickness. Done. After coating, the coated material is dried by a suitable drying means (typically heated to 70 ° C. to 200 ° C. and dried) to remove the solvent from the positive electrode active material layer forming paste, thereby including the positive electrode active material. A positive electrode active material layer is formed.

  Thus, the positive electrode (positive electrode sheet) in which the positive electrode active material layer is formed on the positive electrode current collector can be obtained (step S30 in FIG. 1). In addition, after drying, the thickness and density of a positive electrode active material layer can be suitably adjusted by performing an appropriate press process (for example, roll press process) as needed.

  As described above, the positive electrode obtained in this way is free from aggregation of the positive electrode active material as described above, and is excellent in quality. Therefore, the battery component of various forms or the component of the electrode body incorporated in the battery is used. Can be preferably used. For example, a positive electrode manufactured by any of the methods disclosed herein, a negative electrode (which may be a negative electrode manufactured by applying the present invention), an electrolyte disposed between the positive and negative electrodes, Can be preferably used as a component of a lithium secondary battery including a separator that separates the positive and negative electrodes (can be omitted in a battery using a solid or gel electrolyte). Structure (for example, metal casing or laminate film structure) and size of an outer container constituting such a battery, or structure of an electrode body (for example, a wound structure or a laminated structure) having a positive / negative electrode current collector as a main component There is no particular restriction on the etc.

Hereinafter, an embodiment of a lithium secondary battery constructed using a sheet-like positive electrode (positive electrode sheet) manufactured by applying the method of the present invention will be described with reference to a schematic diagram shown in FIG.
In this lithium secondary battery 100, the positive electrode (positive electrode sheet) 20 manufactured using the positive electrode active material layer forming paste prepared by the manufacturing method disclosed herein is used as the positive electrode (positive electrode sheet) 20. .

  As shown in the drawing, the lithium secondary battery 100 according to the present embodiment includes a case 82 made of metal (a resin or a laminate film is also suitable). The case (outer container) 82 includes a flat cuboid case main body 84 having an open upper end, and a lid 86 that closes the opening. On the upper surface of the case 82 (that is, the lid body 86), a positive electrode terminal 74 that is electrically connected to the positive electrode 20 of the electrode body 80 and a negative electrode terminal 72 that is electrically connected to the negative electrode 30 of the electrode body are provided. In the case 82, for example, a long sheet-like positive electrode (positive electrode sheet) 20 and a long sheet-like negative electrode (negative electrode sheet) 30 are laminated together with a total of two long sheet-like separators (separator sheets) 40. A flat wound electrode body 80 produced by winding and then crushing the resulting wound body from the side direction and kidnapping is housed.

  The positive electrode sheet 20 has a configuration in which a positive electrode active material layer mainly composed of a positive electrode active material is provided on both surfaces of a long sheet-like positive electrode current collector. As the positive electrode current collector, an aluminum foil or other metal foil suitable for the positive electrode is preferably used. Since the positive electrode active material layer is the same as that described above, a detailed description thereof will be omitted.

  Similarly to the positive electrode sheet, the negative electrode sheet 30 has a configuration in which a negative electrode active material layer mainly composed of a negative electrode active material is provided on both surfaces of a long sheet-like negative electrode current collector. For the negative electrode current collector, a copper foil or other metal foil suitable for the negative electrode is preferably used. As the negative electrode active material, one or more of materials conventionally used in lithium secondary batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides (such as lithium titanium oxide), and lithium transition metal nitrides. In addition, the manufacturing method disclosed here can be applied to manufacturing both the positive electrode and the negative electrode. Similarly to the positive electrode sheet 20, the negative electrode sheet 30 may be the negative electrode sheet 30 manufactured using the negative electrode active material layer forming paste prepared by the manufacturing method disclosed herein. At one end in the width direction of these electrode sheets 20, 30, an electrode active material layer non-formation part in which the electrode active material layer is not provided on any surface is formed.

  Moreover, as a suitable example of the separator sheet 40 used between the positive / negative electrode sheets 20 and 30, what was comprised with porous polyolefin resin is mentioned.

  In the above lamination, the positive electrode sheet 20 and the negative electrode active material layer non-formed portion of the negative electrode sheet 20 and the negative electrode active material layer non-formed portion of the negative electrode sheet 30 protrude from both sides of the separator sheet 40 in the width direction. The negative electrode sheet 30 is overlaid with a slight shift in the width direction. As a result, in the lateral direction with respect to the winding direction of the wound electrode body 80, the electrode active material layer non-formation portions of the positive electrode sheet 20 and the negative electrode sheet 30 are respectively wound core portions (that is, the positive electrode active material layer formation portion of the positive electrode sheet 20). And the negative electrode active material layer forming portion of the negative electrode sheet 30 and the two separator sheets 40 are closely wound). The positive electrode side protruding portion 20A and the negative electrode side protruding portion 30A are respectively provided with a positive electrode lead terminal 79 and a negative electrode lead terminal 78, and are electrically connected to the positive electrode terminal 74 and the negative electrode terminal 72, respectively.

Then, the wound electrode body 80 is accommodated in the main body 84 from the upper end opening of the case main body 84, and an electrolyte containing an appropriate supporting salt is disposed (injected) in the case main body 84. Supporting salt is a lithium salt such as LiPF _6, for example. For example, a non-aqueous electrolyte (typically in the form of a solution) prepared by dissolving an appropriate amount (for example, concentration 1M) of a lithium salt such as LiPF _{6 in} a mixed solvent of diethyl carbonate and ethylene carbonate (for example, a volume ratio of 1: 1). A non-aqueous electrolyte (ie, a non-aqueous electrolyte) can be used.

  Thereafter, the opening is sealed by welding or the like with the lid 86, and the assembly of the lithium secondary battery 100 according to the present embodiment is completed. The sealing process of the case 82 and the arrangement (injection) process of the electrolyte may be the same as the technique used in the production of the conventional lithium secondary battery, and do not characterize the present invention. In this way, the construction of the lithium secondary battery 100 according to this embodiment is completed.

  Hereinafter, although the test example regarding this invention is demonstrated, it is not intending to limit this invention to what is shown to the following test examples.

[Positive electrode active material forming paste]
<Example 1>
89.8 parts by mass of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material, ₂ parts by mass of PVdF as a binder, 7.98 parts by mass of AB as a conductive material, and polyvinyl as a dispersant After the paste raw material (solid content concentration: about 54 mass%) containing 0.2 parts by mass of pyrrolidone (PVP) and NMP as a solvent is accommodated in the stirring vessel 12 shown in FIG. And stirred for 5 minutes at a rotation speed of 50 rpm. Next, the paste raw material in the vicinity of the surface of the disper blade 14 was locally heated by a heating wire 18A wound around the disper blade 14 and stirred at a rotation speed of 50 rpm of the anchor blade 16 and a rotation speed of 5000 rpm of the disper blade 14 for 40 minutes. At this time, the temperature of the paste raw material in contact with the disperse blade 14 (that is, the temperature of the portion that has undergone local heating; hereinafter referred to as “the temperature of the heating portion”) was adjusted to about 50 ° C. . Thus, the positive electrode active material layer forming paste according to Example 1 was obtained.

<Example 2>
A positive electrode active material layer forming paste was obtained in the same manner as in Example 1 except that the temperature of the heating part was changed to about 60 ° C.

<Example 3>
A positive electrode active material layer forming paste was obtained in the same manner as in Example 1 except that the temperature of the heating part was changed to about 70 ° C.

<Example 4>
A positive electrode active material layer forming paste was obtained in the same manner as in Example 1 except that the temperature of the heating part was changed to about 80 ° C.

<Comparative example>
A paste for forming a positive electrode active material layer was obtained in the same manner as in Example 1 except that the paste raw material in the vicinity of the surface of the disper blade 14 was stirred without being heated.

  The viscosity of the positive electrode active material layer forming paste obtained in each of the above examples (hereinafter referred to as “paste viscosity”) was adjusted to a liquid temperature of 25 ° C. using a commercially available E-type viscometer, and then the rotor was rotated at 1 rpm. Rotated and measured. The results are shown in FIG. In the graph of FIG. 6, the horizontal axis indicates the temperature of the heating part, and the vertical axis indicates the paste viscosity. Moreover, the particle size of the solid particles (aggregates) in the positive electrode active material layer forming paste obtained in each example was measured by a dispersity measuring method according to JIS K 5600-2-5. The results are shown in FIG. In the graph of FIG. 7, the horizontal axis indicates the temperature of the heating unit, and the vertical axis indicates the particle size of the solid particles.

  As shown in FIGS. 6 and 7, the paste for forming the positive electrode active material layer according to the comparative example in which the paste raw material in the vicinity of the surface of the disper blade 14 is stirred without heating is not sufficiently mixed and dispersed. The particle size of the solid particles was increased. On the other hand, the paste for forming a positive electrode active material layer according to Examples 1 to 4 in which the paste raw material in the vicinity of the surface of the disper blade 14 is stirred while being locally heated is the entire contents of the stirring tank by the local heating. As a result, the paste viscosity was significantly reduced and the particle size of the solid particles was also small compared to the comparative example. From the above results, it is confirmed that a paste for forming a positive electrode active material layer with a small dispersibility and good dispersibility can be obtained by locally heating and stirring the paste raw material near the surface of the disper blade 14 did it.

  In the case of the positive electrode active material layer forming paste used here, as shown in FIG. 7, the particle size of the solid particles tended to decrease as the temperature of the heating part increased. From the viewpoint of reducing the diameter of the solid particles, the temperature of the heating part is generally about 40 ° C or higher, preferably 50 ° C or higher, more preferably 60 ° C or higher, more preferably 70 ° C or higher, Especially preferably, it is 80 degreeC or more. However, when the temperature of the heating part exceeded 70 ° C., the paste viscosity was below 2000 mPa · s, as shown in FIG. From the viewpoint of achieving a viscosity suitable for coating, the paste raw material temperature during stirring is suitably 60 ° C. or less, preferably 50 ° C. or less.

  Furthermore, the positive electrode and the lithium secondary battery provided with this positive electrode were constructed using the positive electrode active material layer forming paste according to Example 1 and the comparative example, and the performance was evaluated. The lithium secondary battery was constructed as follows.

[Positive electrode plate]
The positive electrode active material layer forming paste according to Example 1 and the comparative example was applied to both sides of an aluminum foil having a thickness of 15 μm and dried, whereby the positive electrode active material layers were provided on both sides of the positive electrode current collector. A positive electrode plate was produced.

[Negative electrode plate]
Graphite powder as the negative electrode active material, styrene butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener are added to water so that the mass ratio of these materials is 98: 1: 1. A paste for forming a negative electrode active material layer was prepared by dispersing. This negative electrode active material layer forming paste was applied to one side of a copper foil (negative electrode current collector) to produce a negative electrode plate having a negative electrode active material layer provided on one side of the negative electrode current collector.

[Lithium secondary battery]
The positive electrode active material layer of the positive electrode plate is 3 cm × 4 cm, the negative electrode active material layer of the negative electrode plate is 3.2 cm × 4.2 cm, and an aluminum lead is attached to the positive electrode plate for current collection. Then, nickel leads are attached to the negative electrode plate, they are arranged opposite to each other via a separator (a porous polypropylene sheet is used), and inserted into a laminate bag together with a non-aqueous electrolyte to construct a laminate cell 60 shown in FIG. did. In FIG. 8, reference numeral 61 denotes a positive electrode plate, reference numeral 62 denotes a negative electrode plate, reference numeral 63 denotes a separator impregnated with an electrolytic solution, and reference numeral 64 denotes a laminated bag. In addition, as a non-aqueous electrolytic solution, LiPF ₆ as a supporting salt is approximately mixed with a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 3: 4: 3. The one contained at a concentration of 1 mol / liter was used. Thereafter, an initial charge / discharge treatment (conditioning) was performed by a conventional method to obtain a test lithium secondary battery.

[IV resistance]
For each of the lithium secondary batteries constructed using the positive electrode active material layer forming paste according to Example 1 and the comparative example, a constant current constant voltage (CC-CV) in a room temperature (about 25 ° C.) environment atmosphere. Each battery was adjusted to 60% SOC (State of Charge) by charging. Thereafter, discharging was performed at 25 ° C. with a current value of 10 C for 10 seconds, and IV resistance (mΩ) was calculated from the amount of voltage drop 10 seconds after the start of discharge. The result is shown in FIG.

  As shown in FIG. 9, the battery according to Example 1 was constructed using a positive electrode active material layer forming paste having a small particle size and a good dispersibility, and therefore, the IV resistance compared to the battery according to the comparative example. Decreased significantly. From this result, it was confirmed that the battery characteristics can be improved by constructing the battery using the positive electrode active material layer forming paste with a small dispersibility and a large particle size.

  As mentioned above, although this invention was demonstrated by suitable embodiment and an Example, such description is not a limitation matter and of course, various modifications are possible. For example, the type of the battery is not limited to the above-described lithium secondary battery, but may be a battery having various contents with different electrode body constituent materials and electrolytes, such as a nickel metal hydride battery and a nickel cadmium battery.

  Note that any one of the batteries 100 disclosed herein may have a performance suitable as a battery mounted on a vehicle. Therefore, according to the present invention, as shown in FIG. 10, a vehicle 1 including any of the batteries 100 disclosed herein is provided. In particular, a vehicle (for example, an automobile) 1 including the battery 100 as a power source (typically a power source of a hybrid vehicle or an electric vehicle) is provided.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Stirring apparatus 11A Positive electrode active material supply part 11B Binder solution supply part 12 Stirrer tank 14 Disper blade (partial stirring member)
14A Shaft 14B Rotating blade 16 Anchor blade (whole stirring member)
16A Shaft 16B Rotating blade 18 Heating means 18A Heating wire 18B Ultrasonic generator 18C Infrared generator 20 Positive electrode sheet 30 Negative electrode sheet 40 Separator sheet 72 Negative electrode terminal 74 Positive electrode terminal 78 Negative electrode lead terminal 79 Positive electrode lead terminal 80 Winding electrode body 82 Battery case 84 Case body 86 Lid 100 Lithium secondary battery (battery)

Claims (9)

An agitation step in which a paste raw material containing an active material, a binder, and a solvent is contained in an agitation tank, and the contents of the agitation tank are agitated to prepare an active material layer forming paste;
Applying the active material layer forming paste to a current collector to obtain an electrode having an active material layer formed on the current collector;
Using the obtained electrode to construct a battery,
In the stirring step, a partial stirring member that partially stirs the contents of the stirring tank in a part of the stirring tank is used, and the contents in the vicinity of the surface of the partial stirring member are stirred while being locally heated. A method for producing a battery.   The battery manufacturing method according to claim 1, wherein the heating is performed such that a temperature of the content in contact with the partial stirring member is 40 ° C. to 60 ° C.   The battery manufacturing method according to claim 1 or 2, wherein a heating wire attached to the partial stirring member is used as the heating means.   The battery manufacturing method according to claim 1 or 2, wherein a heating method is used as the heating means.   The battery manufacturing method according to claim 1 or 2, wherein a method of heating by irradiating infrared rays is used as the heating means. When storing the paste raw material in a stirring tank,
First, the binder and the solvent are accommodated before the active material, and the active material is accommodated after starting the local heating of the contents near the surface of the partial stirring member. The battery manufacturing method as described in any one of 1-5.   The battery manufacturing method as described in any one of Claims 1-6 whose solid content concentration of the said paste for active material layer formation is 50 mass% or more. The electrode is a positive electrode;
The battery manufacturing method according to claim 1, wherein the paste material includes carbon as a conductive material. The battery manufacturing method according to claim 1, wherein a polyvinylidene fluoride resin is used as the binder.

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