JP2012114046A - Manufacturing method of electrode for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of electrode for secondary battery, capable of easily microfabricating an electrode active material.SOLUTION: The manufacturing method of an electrode for a secondary battery includes: a calcination step of removing a fiber and manufacturing a porous electrolyte (50) by calcinating a hollow part (21) of the fiber (20) of a fiber bundle (30) including the fibers having a hollow structure, and an electrolyte material (40) arranged on the external surface of the fiber; a conduction processing step of arranging a conductive material (60) on the surface of a hole (51) included in the electrolyte after the calcination step; and an electrode active material arrangement step of arranging an electrode active material (70) on the hole of the electrolyte after the conduction processing step.

Description

  The present invention relates to a method for manufacturing a secondary battery electrode.

  With the rapid spread of communication devices and the like, development of secondary batteries as power sources is being promoted. In addition to communication devices, secondary batteries are being developed as power sources for electric vehicles, hybrid vehicles, and the like as low-emission vehicles.

  The electrode of the secondary battery includes an electrode mixture layer disposed on one surface of the electrolyte layer and an electrode current collector foil disposed on the surface of the electrode mixture layer opposite to the electrolyte layer. The electrode mixture layer includes an electrolyte and an electrode active material (a positive electrode active material or a negative electrode active material). Conventionally, an electrode mixture layer has been manufactured by creating a porous electrolyte material by coating such as screen printing and applying a solution of an electrode active material to the electrolyte material (for example, Patent Document 1). . According to this method, it is possible to produce an electrode mixture layer in which an electrode active material is disposed in a porous electrolyte hole.

JP 2009-238576 A

  In view of the performance of the secondary battery, the electrode active material of the electrode of the secondary battery is preferably fine. In order to make the electrode active material fine, it is effective to make the pore diameter of the porous electrolyte material fine. However, in the conventional electrode manufacturing method, it is not easy to make the pore diameter of the porous electrolyte material fine. Moreover, even if the pore diameter of the porous electrolyte material is made fine, it is not easy to fill the fine pores with the electrode active material solution by coating. Thus, it has been difficult to miniaturize the electrode active material by the conventional electrode manufacturing method.

  An object of this invention is to provide the manufacturing method of the electrode for secondary batteries which can refine | miniaturize an electrode active material easily.

  The method for manufacturing an electrode for a secondary battery according to the present invention removes a fiber by firing a hollow part of a fiber bundle having a plurality of hollow fibers and an electrolyte material disposed on the outer surface of the fiber. A firing step for producing a porous electrolyte, a conductive treatment step for placing a conductive material on the surface of the pores of the electrolyte after the firing step, and an electrode active material in the pores of the electrolyte after the conductive treatment step And an electrode active material disposing step to dispose.

  According to the production method of the present invention, the portion of the fiber removed in the firing step becomes an electrolyte hole, and the electrode active material can be disposed in this hole. Therefore, the outer diameter of the electrolyte hole is equal to or smaller than the outer diameter of the fiber, and the outer diameter of the electrode active material is equal to or smaller than the outer diameter of the fiber. Therefore, since the electrode active material can be miniaturized by using a fiber having a fine outer diameter, the electrode active material can be easily miniaturized.

  In the above method, the outer diameter of the fiber may be 10 μm or less. According to this method, an electrode in which an electrode active material is disposed in an electrolyte hole having a diameter of 10 μm or less can be manufactured. In the above method, the outer diameter of the fiber may be 1 μm or less. According to this method, an electrode in which an electrode active material is disposed in an electrolyte hole having a diameter of 1 μm or less can be manufactured.

  In the above method, the electrode active material arranging step may include a step of arranging the electrode active material in a dispersed state in the holes. According to this method, the contact property between the electrode active material and the conductive material can be improved.

  The method may further include an electrolyte material disposing step of disposing the electrolyte material on the hollow portion of the fiber and the outer surface of the fiber by impregnating the fiber bundle with the electrolyte material before the firing step. According to this method, the electrolyte material can be easily disposed in the hollow portion and the outer surface of the fiber.

  In the above method, the material of the fiber may be cellulose, polyimide or polyamide. When the material of the fiber is any of these materials, a fiber having a diameter of 1 μm or less can be easily produced or obtained. Further, the fiber bundle can be easily removed in the firing step.

  In the above method, the conductive material may be carbon. In the above method, the secondary battery may be a lithium ion secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode for secondary batteries which can refine | miniaturize an electrode active material easily can be provided.

It is typical sectional drawing of a secondary battery. FIG. 2A is a schematic perspective view of a fiber bundle. FIG.2 (b) is a typical perspective view of the fiber bundle after a thickness adjustment process. FIG. 3A is a schematic perspective view for explaining the electrolyte material arranging step. FIG. 3B is a schematic cross-sectional view of the fiber bundle after the electrolyte material arranging step when viewed from a direction perpendicular to the fiber axial direction. FIG. 3C is a schematic cross-sectional view of the fiber bundle after the electrolyte material arranging step when viewed from the axial direction of the fiber. FIG. 4 (a) is a schematic cross-sectional view of the electrolyte after the firing step as seen from the same direction as FIG. 3 (c). FIG. 4B is a schematic cross-sectional view of the electrolyte after the conductive treatment process as seen from the same direction as FIG. It is the typical sectional view which looked at the electrolyte after an electrode active material arrangement process from the same direction as Drawing 4 (b).

  Hereinafter, modes for carrying out the present invention will be described.

  The manufacturing method of the electrode for secondary batteries which concerns on Example 1 is demonstrated. First, the overall configuration of the secondary battery 5 in which the electrode is used will be described, and then the electrode manufacturing method will be described. FIG. 1 is a schematic cross-sectional view of the secondary battery 5. In this embodiment, a solid lithium secondary battery is used as an example of the secondary battery 5.

  The secondary battery 5 includes a solid electrolyte layer 10, a positive electrode mixture layer 11, a positive electrode current collector foil 12, a negative electrode mixture layer 13, and a negative electrode current collector foil 14. The secondary battery 5 has a structure in which a positive electrode current collector foil 12, a positive electrode material mixture layer 11, a solid electrolyte layer 10, a negative electrode material mixture layer 13, and a negative electrode current collector foil 14 are laminated in this order. The positive electrode current collector foil 12 and the positive electrode mixture layer 11 have a function as a positive electrode, and the negative electrode mixture layer 13 and the negative electrode current collector foil 14 have a function as a negative electrode. In the following description, the positive electrode current collector foil 12 and the negative electrode current collector foil 14 may be collectively referred to as a current collector foil, and the positive electrode mixture layer 11 and the negative electrode mixture layer 13 may be collectively referred to as a mixture layer.

  The positive electrode current collector foil 12 is not particularly limited, but is made of a metal foil such as aluminum. The positive electrode mixture layer 11 mainly includes a positive electrode active material, a lithium ion conductive solid electrolyte, and the like. The solid electrolyte layer 10 mainly contains a lithium ion conductive solid electrolyte. The negative electrode mixture layer 13 mainly includes a negative electrode active material, a lithium ion conductive solid electrolyte, and the like. The negative electrode current collector foil 14 is not particularly limited, and is made of a metal foil such as copper or stainless steel.

The positive electrode active material used for the positive electrode mixture layer 11 is not particularly limited as long as it has a function as a positive electrode active material. As the positive electrode active material, the same materials as those used in general solid lithium secondary batteries can be used. For example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMn _2−x Ni _x O ₄ , LiMn _2−x Co _x O ₄ , LiMn _2−xy Ni _x Co _y O ₄ , LiFePO ₄ , LiMnPO ₄ , _{LiNiPO 4, LiM 1-x-} y a x B y O 2 or the like can be used. Here, “M” in the general formula LiM _1-xy A _x B _y O ₂ is at least one selected from the group consisting of Co, Ni, Mn, and the like. “B” is “M” or “A”. Among the above, LiCoO ₂ and LiNiO ₂ are preferable, and LiCoO ₂ is particularly preferable. This is because LiCoO ₂ generally has good characteristics as an active material for a positive electrode and is widely used.

  The negative electrode active material used for the negative electrode mixture layer 13 is not particularly limited as long as it has a function as a negative electrode active material. As the negative electrode active material, the same materials as those used for general solid lithium secondary batteries can be used. For example, metal In, metal Li, Si—Li alloy, Sn—Li alloy, SnO—Li-based material, graphite, or the like can be used.

  The solid electrolyte used for the solid electrolyte layer 10 is not particularly limited as long as it has a function as a solid electrolyte. As the solid electrolyte, the same one as that used for a general solid lithium secondary battery can be used. For example, a sulfide-based solid electrolyte, thiosilicone, an oxide-based solid electrolyte, or the like can be used. Among the above, it is preferable to use a sulfide-based solid electrolyte and thiolithicone, and it is preferable to use a sulfide-based solid electrolyte material. This is because the sulfide-based solid electrolyte has high ionic conductivity, so that the output of the secondary battery 5 can be increased. The positive electrode mixture layer 11 and the negative electrode mixture layer 13 also contain the same solid electrolyte. The thickness of the current collector foil is not particularly limited, but is about 15 μm, for example. Although the thickness of the composite material layer is not particularly limited, it is, for example, about 50 μm.

  Then, the manufacturing method of the electrode which concerns on a present Example is demonstrated using FIGS. First, a fiber bundle 30 in which fibers 20 having a hollow structure are gathered in a bundle is prepared. FIG. 2A is a schematic perspective view of the fiber bundle 30. In the present embodiment, as an example, the fiber 20 of the fiber bundle 30 has a cylindrical shape. A cylindrical hollow portion 21 is formed at the center of the cylindrical shape.

  The manufacturing method of the fiber bundle 30 is not specifically limited. For example, the fiber bundle 30 can be manufactured by integrating a plurality of fibers 20 by an adhesion method such as heat fusion.

  Moreover, the manufacturing method of each fiber 20 is not specifically limited. For example, the fiber 20 can be manufactured by an electrospinning method. Specifically, the fiber 20 can be produced by an electrospinning method using two types of liquids that are not compatible. According to this method, a fiber 20 having an outer diameter (d) of 1 μm or less (hereinafter sometimes referred to as submicron) can be easily manufactured. Alternatively, the fiber 20 can also be produced by selectively dissolving and removing a core material of a two-layer structure fiber having a core material and a skin material covering the outer surface of the core material with an organic solvent or the like. Also by this method, the fiber 20 having an outer diameter of submicron can be manufactured.

  The material of the fiber 20 is not particularly limited. As a material of the fiber 20, for example, cellulose, polyimide, polyamide, or the like can be used. When the material of the fiber 20 is these, the submicron fiber 20 can be easily manufactured or obtained. Moreover, the fiber bundle 30 can be easily removed in a firing step described later.

  Then, the thickness adjustment process which adjusts the thickness of the fiber bundle 30 to predetermined thickness is performed. FIG. 2B is a schematic perspective view of the fiber bundle 30 after the thickness adjusting step. For example, the fiber bundle 30 shown in FIG. 2A is sliced in a direction perpendicular to the axial direction of the fiber 20, so that the thickness of the fiber bundle 30 is set to a predetermined thickness (h) as shown in FIG. In this embodiment, the thickness (h) of the fiber bundle 30 is set to about 50 μm, which is the thickness of the composite layer.

  Subsequently, an electrolyte material arranging step of arranging an electrolyte material (hereinafter referred to as an electrolyte material) in the hollow portion 21 and the outer surface of the fiber 20 is performed. FIG. 3A is a schematic perspective view for explaining the electrolyte material arranging step. The electrolyte material arranging step is not particularly limited as long as the electrolyte material can be arranged on the hollow portion 21 and the outer surface of the fiber 20. In this embodiment, as an example of the electrolyte material arranging step, the step of arranging the electrolyte material on the hollow portion 21 and the outer surface of the fiber 20 by impregnating the fiber bundle 30 with the electrolyte material is performed. In this case, for example, the electrolyte material can be easily disposed on the hollow portion 21 and the outer surface of the fiber 20 as compared with the case where the electrolyte material is disposed on the hollow portion 21 and the outer surface by coating.

  Specifically, in the electrolyte material arranging step, a solution containing an electrolyte material (for example, an oxide electrolyte such as a lithium ion conductive solid electrolyte) crushed into submicrons is applied to the fiber bundle 30 while applying pressure. Pressure impregnation is performed. As a result, the electrolyte material is disposed on the hollow portion 21 and the outer surface of the fiber 20.

  FIG. 3B is a schematic cross-sectional view of the fiber bundle 30 after the electrolyte material arranging step when viewed from a direction perpendicular to the axial direction of the fibers 20. Due to the pressure impregnation, the electrolyte material 40 is disposed in the portion of the fiber 20 that was once the hollow portion 21. FIG. 3C is a schematic cross-sectional view of the fiber bundle 30 after the electrolyte material arranging step when viewed from the axial direction of the fiber 20. Due to the pressure impregnation, the electrolyte material 40 is also disposed on the outer surface of the fiber 20. In the present embodiment, the entire gap between the adjacent fibers 20 is filled with the electrolyte material 40, and the packing density of the electrolyte material 40 is high. By performing pressure impregnation in this way, the packing density of the electrolyte material 40 can be easily increased.

  Subsequently, the fiber bundle 30 after the electrolyte material placement step is fired to perform a firing step in which the fibers 20 are removed to produce a porous electrolyte. FIG. 4 (a) is a schematic cross-sectional view of the electrolyte after the firing step as seen from the same direction as FIG. 3 (c). By firing the fiber 20 after the electrolyte material arranging step, the fiber 20 is burned and disappears. Thereby, the fiber 20 is removed. By removing the fiber 20, the portion that was once the fiber 20 remains as the hole 51. Further, the electrolyte material 40 is baked and densified to become the electrolyte 50. As a result, an electrolyte 50 having a plurality of holes 51 is manufactured. The inner diameter of the hole 51 of the electrolyte 50 is equal to or smaller than the outer diameter of the fiber 20. More specifically, the inner diameter of the hole 51 of the electrolyte 50 is equal to the thickness of the fiber 20 (the difference between the outer diameter and the inner diameter).

  Subsequently, a conductive treatment process is performed in which a conductive material is disposed on the surface of the hole 51 of the electrolyte 50. FIG. 4B is a schematic cross-sectional view of the electrolyte after the conductive treatment process as seen from the same direction as FIG. The conductive material 60 is disposed in order to ensure conduction between the electrolyte 50 and an electrode active material described later, and is not particularly limited as long as it has conductivity. In this embodiment, carbon is used as an example of the conductive material 60. In this case, in the conductive treatment process, the electrolyte 50 is coated with a water-soluble material containing carbon such as ascorbic acid (that is, a water-soluble carbon source), and carbonization is performed. Thereby, the surface of the hole 51 of the electrolyte 50 can be coated with carbon.

  Subsequently, an electrode active material arranging step of arranging an electrode active material in the hole 51 of the electrolyte 50 is performed. FIG. 5 is a schematic cross-sectional view of the electrolyte after the electrode active material arranging step when viewed from the same direction as FIG. In the electrode active material arranging step according to the present embodiment, the electrode active material 70 is arranged in a dispersed state in the holes 51 of the electrolyte 50 as an example. In order to arrange the electrode active material 70 in a dispersed state, in the electrode active material arrangement process according to the present embodiment, the electrode active material 70 is deposited in the holes 51 by a chemical reaction as an example.

Specifically, when the electrode active material 70 is a negative electrode active material, an organic metal material such as Si or Sn that can operate as the negative electrode active material is chemically reacted in a supercritical gas (for example, CO ₂ ). As a result, fine particles as a negative electrode active material are deposited inside the holes 51 of the electrolyte 50. At this time, the precipitated fine particles are not densified and are precipitated in an appropriately dispersed state. In this way, the negative electrode active material can be arranged in a dispersed state in the holes 51.

  Thus, by arranging the electrode active material 70 in the hole 51 in a dispersed state, the contact properties of the electrode active material 70, the conductive material 60, and the electrolyte 50 can be improved.

  In addition, since the inner diameter of the hole 51 is equal to or smaller than the outer diameter of the fiber 20, the outer diameter of the fine particles deposited in this step is equal to or smaller than the outer diameter of the fiber 20. Through the above steps, an electrode (a composite layer) in which the electrode active material 70 is disposed in a dispersed state in the holes 51 of the porous electrolyte 50 can be manufactured.

  Subsequently, while comparing the effect of the electrode manufacturing method using the hollow fiber 20 according to the present embodiment with the electrode manufacturing method that does not use the fiber 20 (hereinafter referred to as the electrode manufacturing method according to the comparative example). explain. The electrode manufacturing method according to the comparative example includes a step of manufacturing a porous electrolyte by coating such as screen printing and a step of arranging an electrode active material on the porous electrolyte by coating. Thus, when producing a porous electrolyte by coating, it is not easy to make the pore diameter of the electrolyte fine. Moreover, even if the pore diameter of the electrolyte is made fine, it is not easy to dispose the electrode active material by coating in this fine hole. For example, when the pore diameter of the electrolyte is submicron, it is extremely difficult to dispose the electrode active material in the electrolyte holes by coating. Therefore, it is difficult to make the electrode active material fine by the electrode manufacturing method according to the comparative example. Further, in the manufacturing method according to the comparative example, it is difficult to secure a space for the electrode active material to expand and contract when the manufactured electrode is used.

  On the other hand, according to the electrode manufacturing method according to the present embodiment, the fiber 20 is removed in the firing step, so that the portion that was once the fiber 20 becomes a plurality of holes 51 of the electrolyte 50. An electrode active material 70 can be disposed. Therefore, the outer diameter of the hole 51 is equal to or smaller than the outer diameter of the fiber 20, and the outer diameter of the electrode active material 70 is equal to or smaller than the outer diameter of the fiber 20. Therefore, according to the electrode manufacturing method according to the present embodiment, the electrode active material 70 can be miniaturized by using the fibers 20 having a fine outer diameter, and therefore the electrode active material 70 can be easily miniaturized. be able to. In addition, since the electrode active material 70 can be easily miniaturized, the capacity of the secondary battery 5 can be easily improved. In addition, since the electrode active material 70 is disposed in the hole 51 in a dispersed state, a space is provided for the electrode active material 70 to expand and contract when the secondary battery 5 is used.

  The outer diameter of the fiber 20 is not particularly limited, but a smaller one is preferable in that the diameter of the electrode active material 70 can be reduced. For example, the outer diameter of the fiber 20 is preferably 10 μm or less, and more preferably submicron. When the outer diameter of the fiber 20 is 10 μm or less, an electrode in which the electrode active material 70 is disposed in the hole 51 of the electrolyte 50 having a diameter of 10 μm or less can be manufactured. When the outer diameter of the fiber 20 is submicron, an electrode in which the electrode active material 70 is disposed in the hole 51 of the electrolyte 50 having a submicron diameter can be manufactured.

  In addition, in the case of the method for manufacturing an electrode according to the comparative example, there is a possibility that a phenomenon that the performance of the manufactured electrode deteriorates with the passage of time of use (hereinafter referred to as deterioration with time). The mechanism of this aging deterioration is as follows. First, the electrode of the secondary battery repeatedly expands and contracts as the secondary battery is charged and discharged. When the electrode repeatedly expands and contracts, the electrode active material may be destroyed. When the electrode active material is destroyed, the electrode active material is further refined. In the electrode manufacturing method according to the comparative example, since the hold property of the electrode active material by the electrolyte is not sufficient, the electrode active material is detached from the electrolyte hole when the electrode active material is refined by charging / discharging of the secondary battery. There is a fear. In this case, the disconnection of the electron conduction and Li ion conduction occurs, and the performance of the electrode deteriorates.

  On the other hand, according to the method for manufacturing an electrode according to the present example, the periphery of the electrode active material 70 is surrounded by the electrolyte 50 having the conductive material 60 on the surface (FIG. 5). Thereby, the electrode active material 70 is firmly held by the electrode. Accordingly, the electrode active material 70 is difficult to be removed from the hole 51 of the electrolyte 50 even if the electrode active material 70 is miniaturized due to the expansion / contraction of the electrode during charge / discharge. Even if the electrode active material 70 is further refined and moved inside the hole 51, the conductivity between the electrolyte 50 and the electrode active material 70 is ensured by the conductive material 60. As described above, according to the electrode produced by the manufacturing method according to the present example, the function as the electrode can be maintained for a long time even if the electrode active material 70 is miniaturized by charging and discharging. That is, according to the manufacturing method of the electrode according to the present embodiment, it is possible to suppress deterioration of the electrode with time.

  The secondary battery 5 to which the electrode manufacturing method according to the present embodiment is applied is not limited to a solid lithium secondary battery. The electrode manufacturing method according to the present embodiment can also be applied to electrodes such as liquid lithium secondary batteries and capacitors provided with a separator instead of the solid electrolyte layer 10.

DESCRIPTION OF SYMBOLS 5 Secondary battery 10 Solid electrolyte layer 11 Positive electrode compound layer 12 Positive electrode current collector foil 13 Negative electrode compound material layer 14 Negative electrode current collector foil 20 Fiber 21 Hollow part 30 Fiber bundle 40 Electrolyte material 50 Electrolyte 51 Hole 60 Conductive material 70 Electrode activity material

Claims (8)

A firing step of producing a porous electrolyte by removing the fiber by firing the hollow portion of the fiber bundle having a plurality of hollow structure fibers and the outer surface of the fiber having an electrolyte material disposed thereon When,
A conductive treatment step of disposing a conductive material on the surface of the hole of the electrolyte after the firing step;
An electrode active material disposing step of disposing an electrode active material in the hole of the electrolyte after the conductive treatment step.   2. The method for producing an electrode for a secondary battery according to claim 1, wherein the outer diameter of the fiber is 10 [mu] m or less.   The method for producing an electrode for a secondary battery according to claim 2, wherein the outer diameter of the fiber is 1 µm or less.   The method for manufacturing an electrode for a secondary battery according to any one of claims 1 to 3, wherein the electrode active material arranging step includes a step of arranging the electrode active material in a dispersed state in the hole.   The electrolyte material disposing step of disposing the electrolyte material on the hollow portion of the fiber and on the outer surface of the fiber by impregnating the fiber bundle with the electrolyte material before the firing step. Item 5. A method for producing an electrode for a secondary battery according to any one of Items 1 to 4.   The method for producing an electrode for a secondary battery according to any one of claims 1 to 5, wherein the material of the fiber is cellulose, polyimide or polyamide.   The method for manufacturing an electrode for a secondary battery according to claim 1, wherein the conductive material is carbon.   The said secondary battery is a lithium ion secondary battery, The manufacturing method of the electrode for secondary batteries in any one of Claims 1-7 characterized by the above-mentioned.

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