JP2017022005A - Manufacturing method of lithium ion battery, and manufacturing device for lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of a lithium ion battery and improve a performance by reducing thickness of a mixed layer that is formed on an interface between an electrode layer and an insulation layer.SOLUTION: A manufacturing method of a lithium ion battery includes: a first coating film forming step for forming a first coating film by applying a slurry-state electrode material 11 to a first surface of a current collector foil 1; a second coating film forming step for forming a second coating film by applying a slurry-state insulation material to a surface of the first coating film; a solidification step for solidifying a contact surface of the first coating film with the second coating film or a contact surface of the second coating film with the first coating film by containing a pH gelatinizer in any one of the electrode material and the insulation material and gelatinizing a part of the first coating film or the second coating film containing the pH gelatinizer through pH adjustment; and a drying step for drying the first coating film and the second coating film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lithium ion battery manufacturing method and a lithium ion battery manufacturing apparatus.

  Lithium ion secondary battery is, for example, a positive electrode plate coated with a positive electrode active material on the surface of the current collector foil, a negative electrode plate coated with a negative electrode active material on the surface of the current collector foil, and the contact between the positive electrode plate and the negative electrode plate The electrode winding body which wound the plate-shaped separator which prevents this is provided.

  Here, it is conceivable to prepare each of the positive electrode plate, the negative electrode plate, and the separator as separate parts, that is, separately. However, in this case, there is a problem that, for example, metal foreign matter generated by cutting the positive electrode plate or the negative electrode plate enters between the positive electrode plate and the separator or between the negative electrode plate and the separator, and the positive electrode and the negative electrode are short-circuited. Arise.

  In contrast, for example, in Patent Document 1, a positive electrode plate formed by sequentially coating a surface of a current collector foil with a positive electrode active material and a separator, and a negative electrode active material and a separator are sequentially coated on the surface of another current collector foil. A lithium ion secondary battery formed by winding a negative electrode plate formed by processing is described. If it is such a lithium ion secondary battery, it can prevent that the metal foreign material produced by the cutting | disconnection of a positive electrode plate or a negative electrode plate penetrate | invades between a positive electrode plate or a negative electrode plate, and a separator.

JP 2003-054991 A

  In the technique of Patent Document 1, a slurry-like insulating material that is continuously applied as a separator is applied to the surface of a slurry-like electrode material containing a positive electrode active material or a negative electrode active material, which is applied to the surface of a current collector foil. Then, a mixed layer of the electrode material and the insulating material is formed at the interface between the electrode layer and the insulating layer. When the mixed layer is formed, the insulating layer functioning as a separator is thinned accordingly. In this case, a short circuit between the positive electrode and the negative electrode is likely to occur, and the reliability of the lithium ion secondary battery is lowered. In order to prevent the short circuit, it is conceivable to increase the thickness of the separator. However, in this case, it is difficult to reduce the size and increase the capacity of the lithium ion secondary battery.

  Accordingly, the present invention provides a lithium ion battery that can reduce the thickness of the mixed layer formed at the interface between the electrode layer and the insulating layer, improve the reliability of the lithium ion battery, and improve the performance. An object is to provide a manufacturing method and a manufacturing apparatus.

  As a preferred embodiment of the method for producing a lithium ion battery according to the present invention, a first coating film forming step of forming a first coating film by applying a slurry-like electrode material on the first surface of the current collector foil; A second coating film forming step of forming a second coating film by applying a slurry-like insulating material on the surface of the first coating film, and the electrode material or the insulating material, either of which is pH gelled A part of the first coating film or the second coating film containing the agent and the pH gelling agent is gelled by pH adjustment, or the contact surface of the first coating film with the second coating film or The method includes a fixing step of fixing a contact surface of the second coating film with the first coating film, and a drying step of drying the first coating film and the second coating film.

  In addition, as a preferable embodiment of the lithium ion battery manufacturing apparatus according to the present invention, the lithium ion battery manufacturing apparatus includes a transport unit that transports the current collector foil, and a first tank that houses the slurry-like electrode material, and is transported by the transport unit. A first coating portion for coating the electrode material to form a first coating film on the first surface of the current collector foil; and a second tank for accommodating a slurry-like insulating material. A second coating section for coating the surface of the coating film with the insulating material to form a second coating film; a drying section for drying the first coating film and the second coating film; and the electrode material or the insulating film. A pH adjusting unit that adjusts the pH of the first coating film formed on the first surface of the material or the current collector foil, and either one of the first tank or the second tank is And a pH gelling agent.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and manufacturing apparatus of a lithium ion battery which can improve the reliability of a lithium ion battery and can aim at a performance are realizable.

1 is a schematic diagram showing a schematic configuration of a lithium ion secondary battery manufacturing apparatus according to Example 1. FIG. 6 is a process diagram of a specific manufacturing process of the lithium ion secondary battery according to Example 1. FIG. 3 is a cross-sectional view illustrating a state of an interface between an electrode layer and an insulating layer according to Example 1. FIG. 6 is a schematic diagram showing a lithium ion secondary battery manufacturing apparatus according to Example 2. FIG. It is a schematic diagram which shows the manufacturing apparatus of the lithium ion secondary battery which concerns on Example 3 or Example 4 mentioned later. It is a schematic diagram of the manufacturing apparatus of a lithium ion secondary battery based on a comparative example. It is sectional drawing which expands and shows the die-coater 104 (slit die-coater) provided in the 1st coating part of the manufacturing apparatus of the lithium ion secondary battery which concerns on a comparative example. It is sectional drawing which shows the state of the interface of the electrode layer of an electrode plate formed with the manufacturing apparatus of the lithium ion secondary battery which concerns on a comparative example, and an insulating layer.

  In all the drawings for explaining the following embodiments, parts having the same function are denoted by the same reference numerals, and repeated explanation thereof is omitted. Hereinafter, embodiments will be described in detail with reference to the drawings.

  In the following description, the positive electrode plate and the negative electrode plate are collectively referred to as “electrode plate”, and the positive electrode material and the negative electrode material are collectively referred to as “electrode material”. In the following description, the positive electrode material, the negative electrode material, and the insulating material before the drying process using the drying furnace are substances having fluidity including a binder solution and a liquid such as an organic solvent or water. In the following description, a film made of a positive electrode material may be described as a positive electrode film, a film made of a negative electrode material as a negative electrode film, and a film made of an electrode material in some cases. In the following description, the term “surface of the electrode plate (including the positive electrode plate and the negative electrode plate)” refers to only the front side surface, not the entire surface including the front side surface and the back side surface of the electrode plate. To do.

  In this embodiment, a lithium ion battery is illustrated as a secondary battery that is an electricity storage device, and a manufacturing method and a manufacturing apparatus thereof will be described, but the present invention is not limited to this.

  First, for convenience of description of a method for manufacturing a lithium ion secondary battery according to the embodiment, a conventional method for manufacturing a lithium ion secondary battery will be described as a comparative example.

  FIG. 6 is a schematic diagram of a lithium ion secondary battery manufacturing apparatus according to a comparative example. In the lithium ion secondary battery manufacturing apparatus according to the comparative example, the current collector foil 101 is sent from the current collector metal foil roll 102. The current collector foil 101 is an aluminum foil having a thickness of 20 μm and a width of 200 mm, for example.

  Next, the electrode material 11 supplied from the die coater 104 provided in the first coating portion facing the back roller 105 is applied on the surface of the current collector foil 101 to form a first coating film made of the electrode material 11. (First coating process). Here, the electrode material 11 is supplied from the tank 108 to the die coater 104. The first coating film has a thickness of, for example, 100 μm and a width of, for example, 150 mm.

  Next, the insulating material 12 supplied from the die coater 106 provided in the second coating portion facing the back roller 107 is directly applied on the surface of the first coating film, and the second coating film made of the insulating material 12 is formed. It is formed (second coating process). Here, the insulating material 12 is supplied from the tank 109 to the die coater 106. The thickness of the second coating film is, for example, 20 μm, and the width thereof is, for example, 160 mm.

  Next, the first coating film and the second coating film on the surface of the current collector foil 1 are dried by passing through the drying chamber 113 (drying process), and an electrode layer and an insulating layer are formed, respectively. Thereby, an electrode plate is manufactured. In this drying step, drying is performed at 120 ° C. for 10 minutes. Thereafter, the electrode plate is wound around the winding roll 103.

  As described above, the electrode plate manufacturing apparatus according to the comparative example includes the second coating unit, and the die coater 106 provided in the second coating unit forms an insulating layer on the surface of the first coating film serving as the electrode layer. The second coating film is directly formed.

  For example, a slit die coater is used as the die coater 104 provided in the first coating unit. The slit die coater is a coating device used for applications such as thick film coating or high viscosity material coating.

FIG. 7 is an enlarged cross-sectional view of the die coater 104 (slit die coater) provided in the first coating part of the lithium ion secondary battery manufacturing apparatus according to the comparative example.
As shown in FIG. 7, in the die coating method, the electrode material 11 is supplied from the tank storing the slurry-like electrode material 11 to the manifold 93 of the base 91 by a metering pump. Here, after the pressure distribution of the electrode material 11 is made uniform in the manifold 93, the electrode material 11 is supplied from the manifold 93 to the slit 94 provided continuously and discharged. The discharged electrode material 11 forms an electrode material reservoir 95 called a bead between the base 91 and the current collector foil 101 that travels relatively at a constant interval h1, and in this state the current collector foil 1 With the traveling, the electrode material 11 is pulled out to form a coating film.

  In the first coating step, the coating film is continuously formed by supplying from the slit 94 the same amount of electrode material 11 that is consumed by the formation of the coating film. At this time, in order to stably apply the thin film, it is important to stabilize the formation of the downstream meniscus 99 that is the bending of the liquid surface of the electrode material reservoir 95. Therefore, the pressure for supplying the electrode material 11 to the manifold 93 is the slit 94 pressure loss + the downstream lip 98 pressure loss of the base 91 + the downstream meniscus 99 pressure. That is, in order to stably apply the electrode material 11 to the current collector foil 1, it is necessary to apply a certain amount of pressure from the electrode material 11 to the current collector foil 1.

  For the die coater 106 provided in the second coating unit, for example, a slit die coater similar to the die coater 104 provided in the first coating unit is used. In the second coating process, the insulating material 12 is applied in the same manner as in the first coating process, for example.

  As described above, in the method of manufacturing the electrode plate according to the comparative example, after the first coating film made of the electrode material 11 and the second coating film made of the insulating material 12 are applied in layers, the first coating film is formed in the drying chamber 113. In addition, the electrode layer and the insulating layer are formed by drying and fixing the second coating film at the same time. Thereby, since processing, such as cutting and welding of an electrode plate, can be performed in a state where there is no gap between the electrode layer and the insulating layer, an internal short circuit due to intrusion of a metal foreign object can be prevented.

  However, in the electrode plate manufacturing method according to the comparative example, the slurry-like electrode material 11 and the slurry-like insulating material 12 are continuously applied on the surface of the current collector foil 101. There is a tendency that the thickness of the mixed layer of the electrode material 11 and the insulating material 12 formed at the interface is increased.

FIG. 8 is a cross-sectional view showing a state of an interface between an electrode layer and an insulating layer of an electrode plate formed by a lithium ion secondary battery manufacturing apparatus according to a comparative example.
As shown in FIG. 8, a mixed layer 53 that has lost its insulating function is formed at the interface between the electrode layer 51 and the insulating layer 52 formed on the surface of the current collector foil 101. The present inventors have found that the mixed layer 53 is a layer generated due to the coating pressure of the slit die coater shown in FIG.

  The thickness of the mixed layer 53 varies depending on the conveyance speed of the current collector foil 101. That is, the slower the conveying speed of the current collector foil 101, the longer the time during which the coating pressure applied by the slit die coater is applied to the coating film at a specific location, so the thickness of the mixed layer 53 also increases. Even if the conveying speed of the current collector foil 101 is set to a relatively high speed of 100 m / min, the thickness of the mixed layer 53 is 10 μm or more.

  When the mixed layer 53 is formed to be relatively thick, the substantial thickness L2 ′ of the insulating layer 52 having an insulating function is thinner than the originally intended thickness L2 (hereinafter sometimes referred to as the initial thickness L2). In addition, when the insulating layer 52 is thinned, there is a problem that an electrode material component constituting the mixed layer 53 may be exposed above the insulating layer 52.

  In the following description, the thicknesses of the electrode layer 51 and the insulating layer 52 before the formation of the mixed layer are respectively indicated as an initial thickness L1 and an initial thickness L2, and the electrode layer 51 and the insulating layer after the formation of the mixed layer are shown. The thicknesses 52 are indicated as a substantial thickness L1 ′ and a substantial thickness L2 ′, respectively.

  Specifically, when the thickness L3 of the mixed layer 53 is larger than 20% of the thickness L2 (initial thickness L2) of the insulating layer 52, the total film thickness of the insulating layer 52 between the positive electrode and the negative electrode. Among them, the region where the insulating function is lost becomes excessive, the insulating property of the insulating layer 52 is lowered, and a short circuit between the positive electrode and the negative electrode becomes remarkable.

  That is, the thickness L3 of the mixed layer 53 is desirably 20% or less of the thickness L2 (initial thickness L2) of the insulating layer 52. Therefore, when the thickness L2 (initial thickness L2) of the insulating layer 52 is 40 μm, the thickness L3 of the mixed layer 53 is desirably 8 μm or less. In the electrode plate formed by the manufacturing apparatus according to the comparative example, the mixed layer 53 is likely to be thick. Therefore, in order to prevent the above-described problem from occurring and to ensure the reliability of the insulating layer 52, the insulating layer 52 is, for example, It is necessary to form a thick film of 50 μm or more.

  As described above, in the method of manufacturing a lithium ion secondary battery according to the comparative example, the electrode layer 51 and the insulating layer 52 are formed without a gap, so that prevention of internal short circuit and improvement in productivity are achieved. Since the mixed layer 53 formed at the interface between the electrode layer 51 and the insulating layer 52 tends to be thick, it is difficult to reduce the thickness of the insulating layer 52. That is, in the lithium ion secondary battery according to the comparative example, it has been difficult to simultaneously realize high capacity and small size while maintaining the reliability of the lithium ion secondary battery.

  The method for producing a lithium ion secondary battery according to Example 1 uses a material containing a component that gels the electrode material at a pH value in a predetermined range (hereinafter simply referred to as a pH gelling agent) as the electrode material. It is a feature.

  That is, in Example 1, the electrode material containing the pH gelling agent was applied on the surface of the current collector foil as the first coating film of the first layer to be the electrode layer, and then on the surface of the first coating film. In addition, an insulating material adjusted to a pH value (gelation pH value) at which the electrode material is gelled by a pH gelling agent is applied as a second coating film as a second layer serving as an insulating layer. Yes.

  In the following description, a component that gels the base material at a pH value in a predetermined range is referred to as a “pH gelling agent”. Here, the base material is “electrode material” when the pH gelling agent is contained in the electrode material, and “insulating material” when the pH gelling agent is contained in the insulating material. It is.

  In the following description, the pH value at which the base material is gelled by the pH gelling agent is referred to as “gelling pH value”.

(Lithium ion secondary battery manufacturing equipment)
An apparatus for manufacturing a lithium ion secondary battery according to Example 1 will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a schematic configuration of a lithium ion secondary battery manufacturing apparatus according to a first embodiment.

  As shown in FIG. 1, the lithium ion secondary battery manufacturing apparatus according to Example 1 includes a current collecting metal foil roll 2 that sends out a current collector foil 1 and a winding roll 3 that winds up the current collector foil 1. Have. The current collector foil 1, which is a thin plate-like metal foil, is conveyed between the current collector metal foil roll 2 and the take-up roll 3 while being supported by a plurality of rollers. Here, a plurality of rollers for transporting the current collector foil 1 at a constant speed is referred to as a roller transport system, that is, a transport unit.

  A die coater 4, a die coater 6, and a drying chamber 13 are arranged in order from the current collecting metal foil roll 2 side to the take-up roll 3 side in the conveyance path of the current collecting foil 1. Further, a back roller 5 is disposed facing the die coater 4, and a back roller 7 is disposed facing the die coater 6. The current collector foil 1 to be conveyed passes between the die coater 4 and the back roller 5, between the die coater 6 and the back roller 7, and inside the drying chamber 13.

  The electrode material 11 is supplied from the tank 8 to the die coater 4, and the insulating material 12 is supplied from the tank 9 to the die coater 6. The tank 9 is provided with a pH controller 10 that monitors and controls the pH value in the tank 9. Here, the first coating unit 31 is configured by the die coater 4 and the tank 8, and the second coating unit 32 is configured by the die coater 6, the tank 9, and the pH controller 10.

  In FIG. 1, an electrode material 11 used for forming an electrode layer constituting a positive electrode or a negative electrode of a lithium ion secondary battery is made of an active material and a conductive auxiliary powder capable of releasing and occluding lithium ions by charging and discharging. A high-viscosity slurry-like liquid kneaded and prepared with a binder and a solvent for binding these powders.

(Method for producing lithium ion secondary battery)
Below, the manufacturing method of a lithium ion secondary battery is demonstrated concretely using FIG.1 and FIG.2. FIG. 2 is a process diagram of a specific manufacturing process of the lithium ion secondary battery according to the first embodiment.

  Each of the positive electrode and the negative electrode constituting the lithium ion secondary battery is manufactured by basically the same process, although there are differences in the material of the current collector foil 1 and the material of the film applied to the current collector foil 1. Therefore, in the following, description will be made without dividing the manufacturing steps of the positive electrode and the negative electrode.

  For example, an electrode material, which is a coating material described later, includes a case where it is a positive electrode material and a case where it is a negative electrode material. In each case, the electrode material is composed of different materials. Here, it goes without saying that, in the positive electrode manufacturing process, a current collector foil and a coating material made of a positive electrode material are used, and a material used only for the negative electrode manufacturing process is not used. Similarly, in the negative electrode manufacturing process, a material used only for the positive electrode manufacturing process is not used.

[1. Production of electrode plates (positive and negative plates)]
<Kneading and blending process>
In the manufacturing process of the lithium ion secondary battery according to Example 1, first, the electrode material 11 for forming the positive electrode or the negative electrode of the lithium ion secondary battery is kneaded and prepared.

  Specifically, a powder of an active material and a conductive additive is kneaded together with a binder for binding these powders, a thickener for viscosity adjustment, a pH gelling agent, and a solvent, and a lithium ion secondary battery An electrode material 11 for forming a positive electrode or a negative electrode is prepared. The electrode material 11 is a high-viscosity slurry liquid.

  Furthermore, in the kneading / mixing step, the insulating material 12 is prepared by mixing the inorganic oxide with a binder, a thickener, and a solvent. In Example 1, the pH value of the insulating material 12 is adjusted to a pH value (gelation pH value) at which the surface of the first coating film (electrode material 11) gels with a pH gelling agent.

<First coating process (electrode material)>
Next, the surface of the current collector foil 1 supplied from the metal foil roll 2 for current collection using the die coater 4 provided in the first coating unit 31 with the slurry-like electrode material 11 obtained in the kneading / mixing step. Apply thinly and uniformly on top (first coating process). Here, the electrode material 11 is supplied from the tank 8 to the die coater 4. Below, the film | membrane which consists of the electrode material 11 apply | coated on the surface of the current collection foil 1 by the 1st coating process is called a 1st coating film.

  For example, a slit die coater having the same configuration as shown in FIG. 7 can be used as the die coater 4 in the first coating unit 31, but other devices can be used as the device for applying the electrode material 11. Good.

<Second coating process (insulating material) and pH adjustment (solidification) process>
Next, in the kneading / preparing step, the slurry-like insulating material 12 whose pH is adjusted to the pH value (gelation pH) at which the first coating film is gelled by the pH gelling agent is applied to the second coating part 32. Using the die coater 6 provided, a thin and uniform coating is performed on the surface of the first coating film (second coating process).

  Here, the insulating material 12 is supplied from the tank 9 to the die coater 6. The internal pH of the tank 9 is monitored and controlled by the pH controller 10, and the pH is adjusted when the pH value of the insulating material 12 deviates from the gelation pH of the surface of the first coating film.

  Below, the film | membrane which consists of the insulating material 12 apply | coated on the surface of the 1st coating film by the 2nd coating process is called a 2nd coating film. For example, a slit die coater having a configuration similar to that shown in FIG. 7 can be used as the die coater 6 in the second coating unit 32, but other apparatuses may be used as the apparatus for applying the insulating material 12. Good.

  Here, in Example 1, as described above, the electrode material 11 contains a pH gelling agent, and this is one of the features of Example 1.

  That is, in the second coating process, as described above, the pH-adjusted insulating material 12 is brought into contact with the surface of the first coating film formed of the electrode material 11 containing the pH gelling agent. A second coating film is formed. When the pH-adjusted insulating material 12 contacts the surface of the first coating film, the solvent of the insulating material 12 and the solvent in the first coating film penetrate each other. In the first embodiment, the application of the pH-adjusted insulating material 12 on the surface of the first coating film is also one of the feature points.

  Here, the process in which the solvent of the insulating material 12 and the solvent in the first coating film permeate each other to change the pH of the surface of the first coating film containing the pH gelling agent is referred to as a pH adjustment (solidification) process. That is, in Example 1, the coating process of the insulating material 12 and the pH adjustment (solidification) process of the first coating film proceed simultaneously.

  Here, when the solvent of the insulating material 12 and the solvent in the first coating film permeate each other on the surface of the first coating film and the pH changes, the pH at which the surface of the first coating film gels is maintained. Therefore, it is desirable that the insulating material 12 includes a buffer such as phosphate and sodium acetate.

  In the following embodiments including Example 1, the step of adjusting the pH value of the material containing the pH gelling agent is referred to as “pH adjustment (solidification) step”, and the pH value of the material not containing the pH gelling agent is described. The process of adjusting is simply referred to as “pH adjustment process” to distinguish them.

  In the pH adjustment (solidification) step, when the pH changes in the surface layer of the first coating film to become a gelled pH, the surface gel layer (second coating) of the first coating film is formed by the pH gelling agent in the first coating film. The contact surface with the membrane is gelled and immobilized. That is, the active material particles constituting the first coating film are fixed (solidified) by gelation of the surface layer of the first coating film by the pH gelling agent.

  As described above, the solidification of the surface layer of the first coating film prevents the active material particles constituting the first coating film from being mixed into the second coating film formed on the surface of the first coating film. be able to. The surface layer of the first coating film means the first coating film in the vicinity of the surface including the surface of the first coating film.

<Drying process>
Next, the current collector foil 1 coated with the second coating film in the second coating step is conveyed into a drying chamber 13 which is a hot air drying furnace. In the drying chamber 13, the solvent component in the first coating film and the second coating film is heated and evaporated to dry and solidify the first coating film and the second coating film, and the electrode layer and the insulating layer are formed. Form in a lump. That is, the first coating film becomes an electrode layer by a drying process, and the second coating film becomes an insulating layer, that is, a separator, by a drying process. Thereby, the electrode plate which consists of the current collection foil 1 and the electrode layer and insulating layer which were laminated | stacked in order on the single side | surface of the current collection foil 1, ie, a positive electrode plate or a negative electrode plate, is formed. Thereafter, the electrode plate is wound around the winding roll 3.

<Processing process>
Next, the current collector foil 1 is subjected to processing such as compression and cutting.
[2. Battery cell assembly]
<Winding process>
Next, a positive electrode and a negative electrode having a size necessary for the battery cell are cut out from the positive electrode plate and the negative electrode plate. At this time, the insulating layer which is a separator for separating the positive electrode and the negative electrode is cut out together with the positive electrode or the negative electrode. Subsequently, the positive electrode and the negative electrode having the separator laminated on the surface thereof are superposed so that the respective separators are brought into contact with each other, and then the laminate including the positive electrode and the negative electrode is combined.

<Welding and assembly process>
Next, a group of positive electrode and negative electrode pairs that are combined together is assembled and welded. In this welding / assembly process, for example, an aluminum ribbon is wound around the positive electrode current collecting tab, and the positive electrode current collecting tab is connected to the aluminum ribbon by ultrasonic welding.

<Liquid extraction process>
Next, the welded electrode pair group is placed in the battery can, and then an electrolytic solution is injected.

<Sealing process>
Next, the battery can of a lithium ion secondary battery is produced by completely sealing the battery can.

<Charging / discharging process>
Next, the battery cell of the produced lithium ion secondary battery is repeatedly charged and discharged.

<Single cell inspection>
Next, the battery cell performance and reliability are inspected (for example, the capacity and voltage of the battery cell, and the current and voltage during charging or discharging). Thereby, the battery cell of a lithium ion secondary battery, ie, a single battery, is completed.

(Each material of lithium ion battery)
Next, each material used in order to manufacture the lithium ion secondary battery by Example 1 is demonstrated.
The positive electrode active material used in the electrode material 11 of Example 1 includes a lithium-containing composite oxide having a spinel structure containing lithium cobaltate or Mn (manganese), or Ni (nickel), Co (cobalt), or Mn ( A composite oxide containing manganese) can be used.

  Moreover, olivine type compounds, such as olivine type iron phosphate, can also be used for a positive electrode active material. However, the positive electrode active material is not limited to these materials, and other materials may be used. Since the lithium-containing composite oxide having a spinel structure containing Mn (manganese) is excellent in thermal stability, for example, a highly safe battery can be configured.

Further, as the positive electrode active material, only a lithium-containing composite oxide having a spinel structure containing Mn (manganese) may be used, but other positive electrode active materials may be used in combination. Examples of other positive electrode active materials include olivine type compounds represented by Li ₁ + xMO ₂ (−0.1 <x <0.1). Examples of the metal M in this formula include Co (cobalt), Ni (nickel), Mn (manganese), Al (aluminum), Mg (magnesium), Zr (zirconium), or Ti (titanium).

Further, a lithium-containing transition metal oxide having a layered structure can be used for the positive electrode active material. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO ₂ or LiNi ₁ -xCo _x -yAl _y O ₂ (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0.2). Can be used.

For the lithium-containing transition metal oxide having a layered structure, an oxide containing at least Co (cobalt), Ni (nickel), and Mn (manganese) can be used. Examples of the oxide containing Co (cobalt), Ni (nickel), and Mn (manganese) include LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6. O ₂ , LiNi _3/5 Mn _1/5 Co _1/5 O ₂ or the like can be given.

  As the negative electrode active material used in the electrode material 11 of Example 1, for example, a graphite material such as natural graphite (flaky graphite), artificial graphite, or expanded graphite can be used. Also, as the negative electrode active material, an easily graphitizable carbonaceous material such as coke obtained by firing pitch can be used. In addition, as the negative electrode active material, amorphous carbon obtained by low-temperature firing of furfuryl alcohol resin (PFA: Poly Furyl Alcohol) or polyparaphenylene (PPP: Poly-Para-Phenylene) and a phenol resin, etc. The non-graphitizable carbonaceous material can be used.

  In addition to the above carbon material, Li (lithium) or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include a lithium alloy such as Li—Al, or an alloy containing an element that can be alloyed with Li (lithium) such as Si (silicon) or Sn (tin). Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used for the negative electrode active material. This oxide-based material may not contain Li (lithium).

  The conductive auxiliary agent used in the electrode material 11 of Example 1 is used as an electronic conductive auxiliary agent contained in the positive electrode film, and is a carbon material such as carbon black, acetylene black, graphite, carbon fiber, or carbon nanotube. It is preferable. Among the carbon materials, acetylene black is particularly preferable from the viewpoints of the amount of addition and conductivity, and the productivity of the positive electrode mixture slurry for coating. This conductive auxiliary agent can also be contained in the negative electrode film.

  The binder used for the electrode material 11 of Example 1 preferably contains a polymer for binding the active material and the conductive additive to each other. As the binder material, for example, polyvinylidene fluoride-based polymers, water-soluble polymers such as polyvinyl alcohol and derivatives thereof, or rubber-based polymers are preferably used. The polyvinylidene fluoride polymer is a polymer of a fluorine-containing monomer group containing, for example, 80% by mass or more of vinylidene fluoride whose main component is a monomer. Two or more polymers may be used in combination. Further, the binder can be preferably used in a form dissolved in a solvent or an emulsion in which polymer particles are dispersed in a solvent.

  Examples of the fluorine-containing monomer group for synthesizing the polyvinylidene fluoride-based polymer include vinylidene fluoride or a mixture of vinylidene fluoride and another monomer, and a monomer mixture containing 80% by mass or more of vinylidene fluoride. It is done.

  Examples of other monomers include vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, and fluoroalkyl vinyl ether.

  Examples of the rubber-based polymer include styrene butadiene rubber (SBR), ethylene propylene diene rubber, or fluorine rubber.

(Content)
The binder content in the electrode layer, that is, the first coating film is preferably 0.1% by mass or more and 10% by mass or less based on the electrode layer after drying. More preferably, the binder content is 0.3% by mass or more and 5% by mass or less. If the binder content is too small, the mechanical strength of the electrode film after drying is insufficient, and the electrode layer is peeled off from the current collector foil. Moreover, when there is too much content of a binder, there exists a possibility that the amount of active materials in an electrode layer may reduce and battery capacity may become low.

  In addition to the binder, a thickener for adjusting the viscosity of the electrode material may be used. The thickener is preferably used with a binder provided in the form of an emulsion. Examples of the thickener include ethyl cellulose, hydroxyl ethyl cellulose, carboxymethyl cellulose, or sodium carboxymethyl cellulose (CMC-NA) polyacrylate.

  The pH gelling agent used for the electrode material 11 of Example 1 is preferably dissolved in a neutral region and gelled acidic or alkaline from the viewpoint of handling at the time of slurry preparation. Examples of pH gelling agents include algin, alginic algin polymers, chitosan and derivatives thereof, natural polysaccharides such as carrageenan and xanthan gum, and complexes thereof, or polyacrylic acid, cross-linked polyacrylic acid and derivatives thereof. At least one selected from the group consisting of zwitterionic polymers such as poly (N-isopropylacrylamide) (PNIPAM) or a derivative thereof is preferably used. The pH gelling agent may be used as a binder for binding the active material and the conductive additive to each other, or as a thickener for adjusting the viscosity of the electrode material.

As the insulating material 12 of Example 1, an inorganic oxide such as alumina (Al ₂ O ₃ ) or silica (SiO ₂ ) can be used. In addition, by using a slurry in which fine particles of polypropylene or polyethylene are mixed with these inorganic oxides, the insulating layer can be provided with a shutdown property.

  That is, the insulating layer is a porous film, and in the completed lithium ion secondary battery, the electrolytic solution is held in the pores of the insulating layer. And the electrolyte solution hold | maintained in the void | hole comprises the path | route of lithium ion conduction between electrodes. The shutdown property here refers to a function of melting the insulating layer and closing the hole when the lithium ion secondary battery generates abnormal heat. By shutting off permeation of lithium ions in the insulating layer by this shutdown function, the reaction in the battery is stopped, and further increase in battery temperature can be prevented.

  In the insulating material, a resin is used as a binder for binding the inorganic oxide particles. As the binder, the same binder as that used in the electrode material can be used. For example, a polyvinylidene fluoride polymer or a rubber polymer is preferably used. Moreover, you may use thickeners, such as carboxymethylcellulose.

  The current collector foil used in Example 1 is not limited to a sheet-like foil, and the base is a pure metal such as aluminum (Al), copper (Cu), stainless steel, or titanium (Ti). Alternatively, an alloy conductive material can be used. For the current collector foil 1, for example, a net, a punched metal, a foam metal, a foil processed into a plate shape, or the like is used. The thickness of the conductive substrate constituting the current collector foil is, for example, 5 μm to 30 μm, and more preferably 8 μm to 16 μm.

<Specific example>
(Detailed description of the negative electrode manufacturing process)
Next, a specific example of the manufacturing process of the lithium ion secondary battery according to Example 1 will be described in detail with reference to FIGS. 1 and 2 taking the manufacturing process of the negative electrode as an example.

[1. Negative electrode manufacturing]
<Kneading and blending process>
First, the kneading / mixing step of the electrode material 11 is performed.
Artificial graphite is used for the negative electrode active material constituting the electrode material 11. In the kneading / preparing step of the electrode material 11, a negative active material, a styrene butadiene rubber (hereinafter simply referred to as SBR) as a binder, sodium alginate as a pH gelling agent, and water as a solvent are kneaded with a planetary mixer. The electrode material 11 is adjusted.

  Here, the negative electrode active material (active material), SBR (binder), and sodium alginate (pH gelling agent) are mixed at a ratio of, for example, 100: 1: 1. Sodium alginate also functions as a thickener, and the electrode material 11 is a highly viscous liquid. The viscosity of the electrode material 11 measured with a rotational viscometer is, for example, about 3 Pa · s.

<First coating process (electrode material)>
Next, a first coating process (electrode material) is performed. Here, a copper (Cu) foil having a thickness of 20 μm and a width of 200 mm, for example, is used for the current collector foil 1 that is an object to be coated in the first coating process. In the first application step, the electrode material 11 is applied onto the surface of the current collector foil 1 using the die coater 4 which is a slit die coater. Thereby, a first coating film made of the electrode material 11 is formed on the surface of the current collector foil 1. The first coating film has a thickness of, for example, 100 μm and a width of, for example, 150 mm. In addition, the width | variety of the current collection foil 1 here and a 1st coating film is a direction orthogonal to the advancing direction of the current collection foil 1 conveyed, respectively, Comprising: Each in the direction along the surface of the current collection foil 1 Refers to the length of the structure.

<Second coating process (insulating material) and pH adjustment (solidification) process>
Next, a second coating process (insulating material) and a pH adjustment (solidification) process are performed. Silica (SiO ₂ ) powder is used as the inorganic oxide of the insulating material 12. Silica (SiO ₂ ) powder as an inorganic oxide, SBR as a binder, methylcellulose (hereinafter simply referred to as MC) as a thickener, and water as a solvent are mixed and kneaded with a planetary mixer to form a slurry. The insulating material 12 is adjusted.

  Here, the inorganic oxide, SBR, and MC are mixed at a ratio of, for example, 100: 1: 1. A phosphate buffer solution is added to these mixtures to adjust the pH value of the mixture (insulating material 12) to pH 3 or less. The insulating material 12 is a high-viscosity liquid, and the viscosity of the insulating material 12 measured with a rotational viscometer is, for example, about 2 Pa · s.

  The insulating material 12 whose pH has been adjusted is applied onto the surface of the first coating film using the die coater 6. A slit die coater is used as the die coater 6.

  Simultaneously with the application of the insulating material 12, the solvent of the insulating material 12 and the solvent in the first coating film permeate each other, and the pH of the surface layer changes to gel. As a result, a second coating film made of the insulating material 12 is formed on the surface of the first coating film. The thickness of the second coating film is, for example, 80 μm, and the width is, for example, 160 mm.

<Drying process>
Next, a drying process is performed. Here, in the drying chamber 13 which is a hot air drying furnace, the first coating film and the second coating film are dried by heating at 120 ° C. for 10 minutes. Thereby, the solvent contained in the first coating film and the second coating film is evaporated and removed, and the entire first coating film and the second coating film are completely solidified. Through these steps, a negative electrode plate for a lithium ion secondary battery is manufactured. That is, the obtained negative electrode plate dries and solidifies the current collector foil 1, the negative electrode layer formed by drying and solidifying the first coating film made of the electrode material 11, and the second coating film made of the insulating material 12. And an insulating layer formed.

<Processing process>
Next, the current collector foil 1 is subjected to processing such as compression and cutting to produce a negative electrode plate having a desired size.

(Interface state between electrode layer and insulating layer)
Here, the state of the interface between the electrode layer and the insulating layer in the electrode plate of the lithium ion secondary battery obtained by the method for manufacturing the lithium ion secondary battery according to Example 1 will be described with reference to FIG. FIG. 3 is a cross-sectional view illustrating the state of the interface between the electrode layer and the insulating layer according to the first embodiment.

  As shown in FIG. 3, an electrode layer 21 having a thickness L1 and an insulating layer 22 serving as a separator having a thickness L2 are sequentially stacked on the current collector foil 1. The electrode layer 21 is a layer formed by drying the first coating film, and the insulating layer 22 is a layer formed by drying the second coating film.

  At the interface between the electrode layer 21 and the insulating layer 22, there is a mixed layer 23 having a thickness L3 formed by mixing the constituent material (electrode material) of the electrode layer 21 and the constituent material (insulating material) of the insulating layer 22. Is formed. In FIG. 3, the upper end and the lower end of the mixed layer 23 are indicated by broken lines, respectively.

  The mixed layer 23 is a region including the interface between the electrode layer 21 and the insulating layer 22, and is formed from the inside of the electrode layer 21 to the inside of the insulating layer 22. In the case of the electrode plate of the lithium ion secondary battery obtained in Example 1, the substantial thickness L1 ′ of the electrode layer 21 after the drying step is, for example, 30 μm to 500 μm, and the substantial thickness L2 ′ of the insulating layer 22 is For example, the thickness is 10 μm to 30 μm.

  The thickness L3 of the mixed layer 23 is calculated based on the cross-sectional view shown in FIG. 3 from an image observed by SEM (Scanning Electron Microscope) by cutting a cross section of the completed electrode plate.

  In the lithium ion secondary battery according to Example 1, the thickness L3 of the mixed layer 23 was 5 μm or less, and it was confirmed that the possibility of occurrence of a short circuit is low even if the insulating layer 22 is thinned.

  In the first embodiment, the electrode plate 11 is manufactured by applying the electrode material 11 and the insulating material 12 in this order to one surface of the current collector foil 1. When the electrode material 11 and the insulating material 12 are applied to both surfaces of the current collector foil 1, <kneading / mixing step>, <first coating step (electrode material) on the surface of the current collector foil 1 >, <Second coating step (insulating material) and pH adjustment (solidification) step>, and <Drying step>, and after <Processing step>, it was wound around the winding roll 3. A method of applying the electrode material 11 and the insulating material 12 by inverting the electrode plate and performing the same process again on the back surface is conceivable.

  The lithium ion secondary battery obtained by the method for manufacturing a lithium ion secondary battery according to Example 1 is the structure of the container (battery can), the size, or the structure of the electrode body having the positive electrode and the negative electrode as main components. There is no particular limitation. The same applies to Examples 2 to 4 below.

(Technical features and effects in Example 1)
As mentioned above, the manufacturing method of the lithium ion secondary battery according to Example 1 includes the first coating step of applying the electrode material 11 containing the pH gelling agent as the first coating film of the first layer, and the pH gel. A second coating step of applying the insulating material 12 adjusted to a pH at which the electrode material 11 is gelled by the agent as a second coating film of the second layer, and the second coating step. PH adjustment (solidification) step of adjusting pH of the contact surface of the first coating film with the second coating film. Furthermore, it has a drying process which dries the 1st coating film and the 2nd coating film.

Moreover, the manufacturing apparatus of the lithium ion secondary battery according to Example 1 includes the first coating unit 31 that applies the electrode material 11 containing the pH gelling agent as the first coating film of the first layer, and the pH gelling agent. A second coating portion 32 for applying the insulating material 12 adjusted to a pH at which the electrode material 11 is gelled (gelation pH) as the second coating film of the second layer, and the first coating film and the second coating film And a drying unit 13 for drying.
The first coating film applied by the first coating unit 31 is formed so that the second coating film is in contact with the first coating film, whereby the pH of the contact surface with the second coating film changes. The second coating unit 32 includes a pH controller 10 that controls the pH of the insulating material 12 to the gelation pH of the pH gelling agent contained in the electrode material 11.

Below, the effect of Example 1 is demonstrated.
The manufacturing method of the electrode plate which comprises the lithium ion secondary battery by Example 1 is, after apply | coating the electrode material 11 containing a pH gelatinizer as a 1st coating film of the 1st layer used as an electrode layer, 1st application | coating On the surface of the first coating film, the insulating material 12 whose pH is adjusted to a pH value (gelation pH value) at which the film is gelled by the pH gelling agent is used as the second coating film of the second layer to be the insulating layer. It is characterized by applying.

  In the above-described comparative example (FIG. 8), the thickness L3 of the mixed layer 53 is 10 μm or more (for example, about 15 μm to 40 μm) even at a practical conveying speed of the current collector foil 1. If the thickness L2 (the initial thickness L2 of the insulating layer 52) is reduced, it is difficult to ensure the substantial thickness L2 ′ of the insulating layer 52 in the finally obtained electrode plate. For this reason, in the laminated body of a positive electrode plate and a negative electrode plate, the possibility of the occurrence of a short circuit between the positive electrode and the negative electrode increases.

  On the other hand, in Example 1, the surface pH of the first coating film is changed by applying the insulating material 12 adjusted to the gelation pH on the surface of the first coating film containing the pH gelling agent. The surface layer of the first coating film is gelled by the pH gelling agent, and the active material particles are fixed in the gelled region. As a result, the thickness L3 of the mixed layer 23 can be reduced as compared with the comparative example. Specifically, in the above-described specific example, the thickness L3 of the mixed layer 23 can be set to 5 μm or less.

  Therefore, in Example 1, even if the insulating layer which is a separator is thinned, it is possible to prevent the occurrence of a short circuit between the positive electrode and the negative electrode in the laminate of the positive electrode plate and the negative electrode plate. Furthermore, since the insulating layer that is a separator can be thinned, the lithium ion secondary battery can be reduced in size and capacity. From the above points, it is possible to improve the reliability and performance of the lithium ion secondary battery.

  Moreover, according to Example 1, since it is not necessary to provide a pH adjustment part separately between a 1st coating part and a 2nd coating part like Examples 3-4 mentioned later, the structure of the whole apparatus. Can be simplified.

  The method for manufacturing a lithium ion secondary battery according to Example 2 is characterized in that an insulating material containing a component (pH gelling agent) that gels the insulating material at a pH value within a predetermined range is used.

  That is, in Example 2, an electrode material whose pH is adjusted to a pH value (gelation pH) at which the second coating film (insulating material) gels with a pH gelling agent is applied as the first coating film of the first layer. After the processing, an insulating material containing a pH gelling agent is applied as a second coating film as a second layer on the surface of the first coating film whose pH has been adjusted.

(Method for producing lithium ion secondary battery)
A method of manufacturing a lithium ion secondary battery according to Example 2 will be described with reference to FIG. FIG. 4 is a schematic diagram illustrating a lithium ion secondary battery manufacturing apparatus according to the second embodiment.

  In the lithium ion secondary battery manufacturing apparatus shown in FIG. 4, the pH controller 14 is provided in the tank 8 of the first coating unit 31, and the pH controller 10 is provided in the tank 9 of the second coating unit 32. Except for the points not described, the configuration is the same as that of the lithium ion secondary battery manufacturing apparatus of Example 1, and the details are omitted.

<Kneading and blending process>
First, the electrode material 11 for forming the positive electrode or negative electrode of a lithium ion secondary battery is kneaded and prepared. The electrode material 11 includes the same active material and conductive additive powder as in Example 1 above, a binder for binding these powders, a thickener for viscosity adjustment, and a solvent. The agent is not included.

  The electrode material 11 is a high-viscosity slurry-like liquid, and in Example 2, the pH value of the electrode material 11 is gelled by the pH gelling agent blended with the insulating material 12 (gel PH).

  The electrode material 11 is, for example, a material in which the weight ratio of the negative electrode active material (active material), SBR (binder), and MC (thickener) is, for example, 100: 1: 1, and water as a solvent. These are kneaded with a planetary mixer and adjusted. Moreover, the electrode material 11 is adjusted to pH 3 or less using, for example, a phosphate buffer.

  Further, in the kneading / mixing step, the insulating material 12 is prepared by mixing the same inorganic oxide, binder, thickener, and solvent as in Example 1 described above. The insulating material 12 is a high-viscosity slurry-like liquid. In the embodiment, the insulating material 12 further includes a pH gelling agent (for example, alginic acid). As in the first embodiment, the insulating material 12 may be mixed with fine particles of polypropylene or polyethylene.

The insulating material 12 is, for example, a material in which the weight ratio of silica (SiO ₂ ) powder (inorganic oxide), SBR (binder), and alginic acid (pH gelling agent) is, for example, 100: 1: 1. Further, water is added as a solvent, and these are kneaded and adjusted with a planetary mixer.

<First coating process (electrode material)>
Next, the surface of the current collector foil 1 supplied from the metal foil roll 2 for current collection using the die coater 4 provided in the first coating unit 31 with the slurry-like electrode material 11 obtained in the kneading / mixing step. A thin and uniform coating is formed thereon to form a first coating film (first coating process).

  As described above, the electrode material 11 is adjusted to a pH value (gelation pH) at which the insulating material 12 is gelled by the pH gelling agent in the kneading / preparation step.

  The electrode material 11 is supplied from the tank 8 to the die coater 4. The internal pH of the tank 8 is monitored and controlled by the pH controller 14, and pH adjustment is performed when the pH value of the electrode material 11 deviates from the pH at which the insulating material 12 gels due to the pH gelling agent in the insulating material 12. Is called. The thickness and width of each of the current collector foil 1 and the first coating film are the same as those in the first embodiment.

<Second coating process (insulating material) and pH adjustment (solidification) process>
Next, the slurry-like insulating material 12 containing the pH gelling agent is thinly and uniformly applied on the surface of the first coating film using the die coater 6 provided in the second coating part 32, and the second coating is performed. A film is formed (second coating process). The thickness and width of the second coating film are the same as those in Example 1 described above.

  That is, in the second coating process of Example 2, as described above, the insulating material 12 containing the pH gelling agent is brought into contact with the surface of the first coating film formed of the pH-adjusted electrode material 11. Thus, the second coating film is formed.

  When the insulating material 12 containing the pH gelling agent comes into contact with the surface of the first coating film made of the pH-adjusted electrode material 11, the solvent of the insulating material 12 and the solvent in the first coating film penetrate each other. Thereby, simultaneously with application | coating of the insulating material 12, pH of a contact surface with the 1st application surface of the insulating material 12 changes, and it becomes gelling pH, and the insulating material 12 is gelatinized by a pH gelling agent ( pH adjustment (solidification step)).

  That is, in Example 2, the coating process of the insulating material 12 and the pH adjustment (solidification) process of the insulating material 12 proceed simultaneously. Thereby, the second coating film made of the insulating material 12 is formed on the surface of the first coating film. The thickness of the second coating film is, for example, 80 μm, and the width is, for example, 160 mm.

  Thus, the inorganic gel particles constituting the second coating film are fixed (solidified) by the gelation of the pH gelling agent on the contact surface of the second coating film with the first coating film. When the contact surface of the second coating film with the first coating film is solidified, the active material particles constituting the first coating film are mixed in the second coating film on the surface in contact with the surface of the first coating film. Can be prevented.

  Here, on the surface of the first coating film, the pH at which the insulating material 12 gels is maintained when the solvent of the insulating material 12 and the solvent in the first coating film penetrate each other and the pH changes. Therefore, the electrode material 11 desirably contains a buffer.

  By using the pH buffer material, the contact surface of the insulating material 12 with the first coating film is maintained at the gelled pH, and the contact surface of the second coating film with the first coating film is solidified. It is possible to prevent the active material particles constituting the first coating film from being mixed into the second coating film formed in contact with the surface.

<Drying process>
Next, the current collector foil 1 coated with the first coating film and the second coating film is conveyed into the drying chamber 13. Then, in the drying chamber 13, the solvent component in the first coating film and the second coating film is heated and evaporated to dry and solidify the first coating film and the second coating film, so that the electrode layer and the insulating layer are insulated. Layers are formed together. Thereby, an electrode plate (positive electrode plate or negative electrode plate) in which the electrode layer and the insulating layer are laminated in this order is formed on one surface of the current collector foil 1. Thereafter, the electrode plate is wound around the winding roll 3.

<Processing process>
Next, processing such as compression and cutting is performed on the current collector foil 1 to manufacture an electrode plate having a desired size.

(Technical features and effects in Example 2)
As described above, in the method of manufacturing the lithium ion secondary battery according to Example 2, the electrode material 11 adjusted to a pH at which the insulating material 12 is gelled by the pH gelling agent is applied as the first coating film of the first layer. The first coating step, the second coating step of applying the insulating material 12 containing the pH gelling agent as the second coating film of the second layer, and the second coating step are performed simultaneously. PH adjustment (solidification) step of adjusting pH of the contact surface of the two coating films with the first coating film. Furthermore, it has a drying process which dries the 1st coating film and the 2nd coating film.

  Moreover, the manufacturing apparatus of the lithium ion secondary battery according to Example 2 uses the electrode material 11 adjusted to a pH (gelation pH) at which the insulating material 12 is gelled by the pH gelling agent as the first coating film of the first layer. First coating unit 31 to be applied, second coating unit 32 to apply insulating material 12 containing a pH gelling agent as a second coating film for the second layer, first coating film and second coating film And a drying unit 13 for drying. The 2nd coating part 32 changes the pH value of the contact surface with the 1st coating film of the said 2nd coating film by forming a 2nd coating film so that it may contact the surface of a 1st coating film. Let The first coating unit 31 includes a pH controller 14 that controls the pH of the electrode material 11 to the gelation pH of the pH gelling agent contained in the insulating material 12.

  The feature of the manufacturing method of the lithium ion secondary battery according to Example 2 is that the insulating material 12 contains a pH gelling agent, and this insulating material 12 is used as the surface of the first coating film made of the electrode material 11 whose pH is adjusted. At the same time, the pH of the contact surface with the first application surface of the insulating material 12 changes and gelation occurs.

  According to the second embodiment, the first coating film having a gelled pH is formed, and the insulating material 12 containing the pH gelling agent is applied on the surface of the first coating film, whereby the first coating of the insulating material 12 is performed. The contact surface with the coating film is gelled by the pH gelling agent, and the inorganic oxide particles are fixed. As a result, the movement of the inorganic oxide particles of the insulating material 12 to the first coating film side and the movement of the active material particles to the second coating film side are prevented, and as shown in FIG. For example, the thickness can be reduced to 5 μm or less as compared with the comparative example (FIG. 8).

  Therefore, in the second embodiment, substantially the same effect as in the first embodiment can be obtained. That is, it is possible to reduce the thickness of the insulating layer as a separator while preventing the occurrence of a short circuit between the positive electrode and the negative electrode, while maintaining the reliability of the lithium ion secondary battery, and reducing the size of the lithium ion secondary battery. And capacity increase.

  In Example 2, since a pH gelling agent is added to the insulating material 12, a conventionally used material can be used for the electrode material 11.

  In the method of manufacturing a lithium ion secondary battery according to Example 3, an electrode material containing a pH gelling agent was applied as a first coating film on the surface of the current collector foil, and the surface side of the current collector foil was After spraying a pH adjusting liquid onto the surface of the first coating film, an insulating material is applied as a second coating film on the surface of the first coating film whose pH has been adjusted.

(Method for producing lithium ion secondary battery)
A method of manufacturing a lithium ion secondary battery according to Example 3 will be described with reference to FIG. FIG. 5 is a schematic diagram showing a lithium ion secondary battery manufacturing apparatus according to Example 3 or Example 4 described later.

  In addition, the manufacturing apparatus of the lithium ion secondary battery shown in FIG. 5 is between the 1st coating part 31 and the 2nd coating part 32 of the surface side (surface side of a 1st coating film) of the current collection foil 1, That is, the lithium ion of Example 1 shown in FIG. 1 except that the sprayer 15 is provided between the die coater 4 and the die coater 6 and that neither the tank 8 nor the tank 9 is equipped with a pH controller. The configuration is the same as that of the secondary battery manufacturing apparatus and the lithium ion secondary battery manufacturing apparatus of Example 2 shown in FIG.

<Kneading and blending process>
First, the electrode material 11 containing a pH gelling agent is adjusted in the same manner as in Example 1 described above. Further, the insulating material 12 is prepared as a slurry-like liquid as in the first embodiment. However, in Example 3, the pH of the insulating material 12 is not adjusted in the kneading / mixing step.

<First coating process (electrode material)>
Next, the slurry-like electrode material 11 obtained in the kneading / mixing step is used for the current collector foil 1 supplied from the current collector metal foil roll 2 using the die coater 4 provided in the first coating unit 31. A thin and uniform coating is formed on the surface to form a first coating film (first coating process).

  The electrode material 11 is supplied from the tank 8 to the die coater 4. The thickness and width of each of the current collector foil 1 and the first coating film are the same as those in the first embodiment.

<PH adjustment (solidification) step>
Next, the pH adjusting liquid is sprayed on the surface of the first coating film using the sprayer 15 installed on the surface side of the current collector foil 1 (the surface side of the first coating film). The surface of the first coating film is gelled by the pH gelling agent contained in the first coating film by changing the pH of the surface of the first coating film to the gelation pH by the sprayed pH adjusting liquid, The surface of the first coating film is solidified.

  Since the surface of the first coating film is solidified, in the second coating step to be described later, the activity that constitutes the first coating film into the second coating film formed in contact with the surface of the first coating film. Mixing of material particles can be prevented.

  Although it does not specifically limit as a pH adjustment liquid, For example, the liquid mixture of phosphoric acid and sodium phosphate can be used.

  At this time, it is important to appropriately select and use the amount of the pH adjusting liquid sprayed from the sprayer 15 and the spray particle diameter. As the type of the spray nozzle, a one-fluid nozzle that ejects only a liquid or a two-fluid nozzle that ejects mixed liquid and gas can be used.

  From the viewpoint of reducing the impact when the spray liquid contacts the first coating film by spraying, it is desirable to use a two-fluid nozzle that can spray finer droplets. Moreover, the average particle diameter D50 of the sprayed particles sprayed from the nozzle is 20 μm or less, more preferably 10 μm or less, so that damage such as a coating film defect can be prevented.

  Moreover, in Example 3, it is possible to control the gelation depth of a 1st coating film with the quantity of the pH adjustment liquid to spray. As the spray amount is increased, the amount of the pH adjusting liquid penetrating into the first coating film is increased, so that the gelation depth becomes deeper.

  When the gelation depth is equal to the first coating film thickness, the active material particles constituting the first coating film are prevented from being mixed into the second coating film formed on the surface of the first coating film. In addition to the effect, the mass transfer during drying is eliminated, and the effect of enabling high-speed drying is exhibited. This is because the active material particles in the first coating film are fixed by gelation, thereby restricting the material transfer accompanying the solvent transfer during drying.

<Second coating process (insulating material)>
Next, the slurry-like insulating material 12 is thinly and uniformly applied on the surface of the first coating film using the die coater 6 provided in the second coating unit 32 to form the second coating film ( Second coating process). The thickness and width of the second coating film are the same as those in Example 1 described above. Here, the insulating material 12 is supplied from the tank 9 to the die coater 6.

<Drying process>
Next, the current collector foil 1 coated with the first coating film and the second coating film is conveyed into the drying chamber 13. Then, in the drying chamber 13, the solvent component in the first coating film and the second coating film is heated and evaporated to dry and solidify the first coating film and the second coating film, so that the electrode layer and the insulating layer are insulated. Layers are formed together.
Thereby, an electrode plate (positive electrode plate or negative electrode plate) in which the electrode layer and the insulating layer are laminated in this order is formed on one surface of the current collector foil 1. Thereafter, the electrode plate is wound around the winding roll 3.

<Processing process>
Next, an electrode plate having a desired size is manufactured by processing the current collector foil 1 such as compression and cutting.

(Technical features and effects in Example 3)
As described above, the method of manufacturing the lithium ion secondary battery according to Example 3 includes the first application step of applying the electrode material 11 containing the pH gelling agent as the first application film of the first layer, and the current collection. From the surface side of the foil 1, using a sprayer 15, a pH adjustment (solidification) step of spraying a pH adjusting liquid onto the surface of the first coating film, and the insulating material 12 are applied as the second coating film of the second layer. It has a 2nd coating process and the drying process which dries a 1st coating film and a 2nd coating film.

  Moreover, the manufacturing apparatus of the lithium ion secondary battery by Example 3 has the 1st coating part 31 which apply | coats the electrode material 11 containing a pH gelling agent as a 1st coating film of 1st layer, and current collection foil 1. A pH adjusting unit that sprays the pH adjusting liquid using the sprayer 15 on the first coating film from the surface side, and a second coating unit 32 that applies the insulating material 12 as the second coating film of the second layer. And a drying unit 13 for drying the first coating film and the second coating film. Furthermore, it is desirable that the pH adjusting unit includes a spray mechanism that can spray the pH adjusting liquid so that the average particle diameter D50 of the spray particles is 20 μm or less.

  According to Example 3, the surface of the first coating film is gelled by the pH gelling agent in the pH adjustment (solidification) step, and the active material particles are immobilized in the gelled region. As a result, as shown in FIG. 3, the thickness of the mixed layer 23 can be reduced to, for example, 5 μm or less, compared with the comparative example (FIG. 8).

  Therefore, the third embodiment can obtain substantially the same effect as the first embodiment. That is, it is possible to reduce the thickness of the insulating layer as a separator while preventing the occurrence of a short circuit between the positive electrode and the negative electrode, while maintaining the reliability of the lithium ion secondary battery, and reducing the size of the lithium ion secondary battery. And capacity increase.

  Moreover, in Example 3, since pH adjustment is performed after a 1st coating process, pH adjustment of an insulating material becomes unnecessary. Furthermore, in Example 3, the gelation depth can be controlled. Therefore, when the gelation depth is the first coating film thickness, mass transfer during drying is eliminated, and high-speed drying is possible.

  Furthermore, it is possible to speed up the drying process as compared with Examples 1 and 2 described above.

  In the method of manufacturing a lithium ion secondary battery according to Example 4, the electrode material is applied as the first coating film on the surface of the current collector foil, and the pH adjusting liquid is sprayed from the surface side of the first coating film. Then, after adjusting the pH of the first coating film surface, an insulating material containing a pH gelling agent is applied as a second coating film on the surface of the pH-adjusted first coating film. It is a feature.

(Method for producing lithium ion secondary battery)
A method of manufacturing a lithium ion secondary battery according to Example 4 will be described with reference to FIG.

<Kneading and blending process>
First, the electrode material 11 is adjusted in the same manner as in Example 2 described above. Moreover, the insulating material 12 containing a pH gelling agent is adjusted as a slurry-like liquid as in Example 2 described above. However, in Example 4, the pH adjustment of the electrode material 11 is not performed in the kneading / mixing step.

<First coating process (electrode material)>
Next, the slurry-like electrode material 11 obtained in the kneading / mixing step is used for the current collector foil 1 supplied from the current collector metal foil roll 2 using the die coater 4 provided in the first coating unit 31. A first coating film is formed on the surface by thin and uniform coating (first coating process).

  The electrode material 11 is supplied from the tank 8 to the die coater 4. The thickness and width of each of the current collector foil 1 and the first coating film are the same as those in the first embodiment.

<PH adjustment step>
Next, using the sprayer 15 installed on the surface side of the current collector foil 1 (the surface side of the first coating film), a pH adjusting liquid is sprayed on the surface of the first coating film, and the pH of the surface of the first coating film is set. To change.

  In the second coating process described later, the pH of the contact surface of the insulating material 12 coated so as to be in contact with the surface of the first coating film is adjusted by the pH-adjusted first coating film. Change. For this reason, in this step, the pH of the surface of the first coating film is adjusted to a pH (gelation pH) at which the insulating material 12 is gelled by the pH gelling agent.

  That is, in the second coating process described later, the pH changes on the contact surface of the insulating material 12 with the first coating film, and the contact surface of the second coating film with the first coating film gels and solidifies. For this reason, it can prevent that the active material particle which comprises a 1st coating film mixes in the 2nd coating film which contacts the surface of a 1st coating film.

  At this time, it is important to appropriately select and use the amount of the pH adjusting liquid sprayed from the sprayer 15 and the spray particle diameter. As the type of the spray nozzle, a one-fluid nozzle that ejects only a liquid or a two-fluid nozzle that mixes and ejects a liquid and a gas can be used. It is desirable to use a two-fluid nozzle that can spray finer droplets from the viewpoint of reducing the impact when the spray liquid water contacts the first coating film by spraying. Moreover, the average particle diameter D50 of the sprayed particles sprayed from the nozzle is 20 μm or less, more preferably 10 μm or less, so that damage such as a coating film defect can be prevented.

<Second coating process (insulating material) and pH (solidification) process>
Next, the insulating material 12 containing the pH gelling agent is thinly and uniformly applied on the surface of the first coating film using the die coater 6 provided in the second coating unit 32, and the second coating film is formed. Form (second coating process). Further, at the same time as the second coating film is formed on the surface of the first coating film, the pH adjusting liquid in the surface of the first coating film penetrates into the second coating film, and the first coating film, the second coating film, The pH of the contact surface changes, and the contact surface of the second coating film with the first coating film gels.

  The thickness and width of the second coating film are the same as those in Example 1 described above. The insulating material 12 is an adjusted slurry-like liquid as in the second embodiment.

<Drying process>
Next, the current collector foil 1 coated with the first coating film and the second coating film is conveyed into the drying chamber 13. Then, in the drying chamber 13, the solvent component in the first coating film and the second coating film is heated and evaporated to dry and solidify the first coating film and the second coating film, so that the electrode layer and the insulating layer are insulated. Layers are formed together. Thereby, an electrode plate (positive electrode plate or negative electrode plate) in which the electrode layer and the insulating layer are laminated in this order is formed on one surface of the current collector foil 1. Thereafter, the electrode plate is wound around the winding roll 3.

<Processing process>
Next, an electrode plate having a desired size is manufactured by processing the current collector foil 1 such as compression and cutting.

(Technical features and effects according to Example 4)
As described above, the manufacturing method of the lithium ion secondary battery according to Example 4 includes the first coating step of applying the electrode material 11 as the first coating film of the first layer, and the surface side of the current collector foil 1. The pH adjusting step of spraying the pH adjusting liquid onto the surface of the first coating film using the sprayer 15 is provided. Further, a second coating step of applying the insulating material 12 containing the pH gelling agent as the second coating film of the second layer, and the first of the second coating film, which is performed simultaneously with the second coating step. A pH adjustment (solidification) step of adjusting the pH of the contact surface with the coating film; and a drying step of drying the first coating film and the second coating film.

  Moreover, the manufacturing apparatus of the lithium ion secondary battery according to Example 4 has the first coating part 31 that applies the electrode material 11 as the first coating film of the first layer, and the first side from the surface side of the current collector foil 1. A spraying device 15 is used to spray a pH adjusting liquid on the first coating film, and a second coating section that coats the insulating material 12 containing the pH gelling agent as the second coating film of the second layer. 32 and a drying unit 13 for drying the first coating film and the second coating film. The second coating film is coated by the second coating unit 32, and at the same time, the contact surface with the first coating film is gelled and solidified. Furthermore, it is preferable that the pH adjusting unit includes a spray mechanism that can spray the pH adjusting liquid so that the average particle diameter D50 of the spray particles is 20 μm or less.

  According to Example 4, contact of the insulating material 12 with the first coating film is performed by applying the insulating material 12 containing the pH gelling agent on the surface of the first coating film whose pH is adjusted by the pH adjusting unit. The surface gels and the inorganic oxide particles are fixed. As a result, as shown in FIG. 3, the thickness of the mixed layer 23 can be reduced to, for example, 5 μm or less, compared with the comparative example (FIG. 8).

  Therefore, the fourth embodiment can obtain substantially the same effect as the first embodiment. That is, it is possible to reduce the thickness of the insulating layer as a separator while preventing the occurrence of a short circuit between the positive electrode and the negative electrode, while maintaining the reliability of the lithium ion secondary battery, and reducing the size of the lithium ion secondary battery. And capacity increase.

  Moreover, in Example 4, since pH adjustment is performed after a 1st coating process, pH adjustment of an electrode material becomes unnecessary.

  As mentioned above, although several embodiment was described concretely, it cannot be overemphasized that this invention can be variously changed in the range which is not limited to the said embodiment and does not deviate from the summary.

  Moreover, the said embodiment is not limited to a lithium ion secondary battery, For example, it can apply widely to an electrical storage device provided with the separator which electrically isolate | separates a positive electrode, a negative electrode, and a positive electrode and a negative electrode. Examples of the electricity storage device include other types of batteries or capacitors.

Current collecting foil ... 1, 101, current collecting metal foil roll ... 2, 102, winding roll ... 3, 103, die coater ... 4, 6, 104, 106, back roller ... 5, 7, 105, 107, tank ... 8, 9, 108, 109, pH controller ... 10, electrode material ... 11, insulating material ... 12, drying chamber ... 13, 113, pH controller ... 14, sprayer ... 15, first coating part ... 31, second Coating part ... 32, electrode layer ... 21, 51, insulating layer ... 22, 52, mixed layer ... 23, 53, substantial thickness of electrode layer 51 ... L1 ', initial thickness of electrode layer 51 ... L1, insulating layer L2 ', initial thickness of insulating layer 52 ... L2, thickness of mixed layer 53 ... L3, base ... 91, manifold ... 93, slit ... 94, electrode material reservoir ... 95, downstream lip ... 98, downstream meniscus ... 99, interval ... h1

Claims (13)

A first coating film forming step of forming a first coating film by applying a slurry-like electrode material on the first surface of the current collector foil;
A second coating film forming step of forming a second coating film by applying a slurry-like insulating material on the surface of the first coating film;
As the electrode material or the insulating material, either one of them includes a pH gelling agent, and a part of the first coating film or the second coating film containing the pH gelling agent is gelled by pH adjustment. An immobilization step of immobilizing a contact surface of the first coating film with the second coating film or a contact surface of the second coating film with the first coating film;
And a drying step of drying the first coating film and the second coating film. Use the electrode material containing the pH gelling agent,
In the second coating film forming step, the insulating material whose pH has been adjusted is applied to the surface of the first coating film, or between the first coating film forming step and the second coating film forming step. By adjusting the pH of the surface of the first coating film,
The method for producing a lithium ion battery according to claim 1, wherein the immobilization step is performed. As the insulating material, use one containing the pH gelling agent,
In the first coating film forming step, the electrode material whose pH is adjusted is applied to the first surface of the current collector foil, or the first coating film forming step and the second coating film forming step After adjusting the pH of the surface of the first coating film,
The method of manufacturing a lithium ion battery according to claim 1, wherein the fixing step is performed by forming the second coating film on a surface of the first coating film.   The pH gelling agent includes algin, algin-based algin polymer, chitosan and derivatives thereof, natural polysaccharides such as carrageenan and xanthan gum and complexes thereof, or polyacrylic acid, cross-linked polyacrylic acid and derivatives thereof, 2. The method for producing a lithium ion battery according to claim 1, wherein the method is at least one selected from the group consisting of zwitterionic polymers of poly (N-isopropylacrylamide) and poly (N-isopropylacrylamide) derivatives. A transport unit for transporting the current collector foil;
A first coating that has a first tank that contains a slurry-like electrode material and forms a first coating film by applying the electrode material to a first surface of the current collector foil transported by the transport unit And
A second coating part that has a second tank for containing a slurry-like insulating material, and that forms the second coating film by coating the insulating material on the surface of the first coating film;
A drying unit for drying the first coating film and the second coating film;
A pH adjusting unit that adjusts the pH of the first coating film formed on the first surface of the electrode material or the insulating material or the current collector foil, and
Either the said 1st tank or the said 2nd tank accommodates a pH gelatinizer, The manufacturing apparatus of the lithium ion battery characterized by the above-mentioned.   The lithium ion battery manufacturing apparatus according to claim 5, wherein any one of the first tank and the second tank includes the pH adjusting unit that adjusts the pH of the electrode material or the insulating material. The first tank contains the electrode material containing the pH gelling agent;
The second tank includes the pH adjusting unit that adjusts the pH of the insulating material, and the second coating unit applies the first application of the insulating material whose pH is adjusted in the second tank. The lithium ion battery manufacturing apparatus according to claim 6, wherein the apparatus is applied to the surface of the film. The first tank includes the pH adjusting unit that adjusts the pH of the electrode material,
The second tank contains the insulating material containing the pH gelling agent;
The said 1st coating part is a manufacturing apparatus of the lithium ion battery of Claim 6 which apply | coats the said electrode material pH-adjusted in the said 1st tank to the 1st surface of the said current collection foil.   The pH adjusting unit that adjusts the pH of the first coating film formed on the first surface of the current collector foil by the first coating unit includes the first coating unit and the second coating unit. The lithium ion battery manufacturing apparatus according to claim 5, which is provided between the two. The first tank contains the electrode material containing the pH gelling agent,
The said pH adjustment part is a manufacturing apparatus of the lithium ion battery of Claim 9 which adjusts the pH of the said 1st coating film surface formed with the said electrode material to the gelation pH of the said pH gelatinizer. The second tank contains the insulating material containing the pH gelling agent,
The pH adjusting unit adjusts the pH of the first coating film surface to the gelation pH of the pH gelling agent, and the second coating unit is brought into contact with the pH-adjusted first coating film surface. The apparatus for manufacturing a lithium ion battery according to claim 9, wherein the insulating material is applied.   The pH adjusting unit includes, as the pH gelling agent, algin, alginic algin polymer, chitosan and derivatives thereof, natural polysaccharides such as carrageenan and xanthan gum, and complexes thereof, or polyacrylic acid, cross-linked poly The lithium ion according to claim 5, which contains at least one selected from the group consisting of zwitterionic polymers such as acrylic acid and derivatives thereof, poly (N-isopropylacrylamide), poly (N-isopropylacrylamide) derivatives, and the like. Battery manufacturing equipment.   The said pH adjustment part is a manufacturing apparatus of the lithium ion battery of Claim 9 which is a pH adjustment liquid sprayer arrange | positioned at the said 1st surface side of the said current collection foil.

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