JP2017004824A - Secondary battery and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for enhancing charge/discharge characteristics of a secondary battery without short-circuiting between a positive electrode layer and a negative electrode layer.SOLUTION: The secondary battery includes on a substrate a collector, a positive electrode layer, an electrolyte layer and a negative electrode layer, sequentially laminated. The positive electrode layer contains positive electrode active materials. An average particle size of the positive electrode active materials included in the entire area of the positive electrode layer or in a partial area of the positive electrode layer positioned on a side of the electrolyte is less than or equal to 2 μm, preferably less than or equal to 0.2 μm.SELECTED DRAWING: Figure 1

Description

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

  For example, Patent Document 1 states that “when the discharge characteristics of a solid electrolyte battery are improved and the battery is used as a secondary battery, charging / discharging with a large current can be performed and the electrode material gradually deteriorates due to charging / discharging. "Solid electrolyte battery and solid electrolyte battery" aiming to obtain a solid electrolyte battery excellent in charge / discharge cycle characteristics without reducing the charge / discharge capacity "(paragraph 0005 of the same document) An invention of “a manufacturing method of” is disclosed.

  The invention described in this document states that “the powders used for the positive electrode and negative electrode materials include those having various particle diameters. Thus, the positive electrode and the negative electrode were prepared using electrode materials having various particle diameters. Thereafter, when a fluid monomer material constituting a polymer electrolyte is applied on the positive electrode or the negative electrode, the monomer material does not sufficiently penetrate into the inside of the electrode, and the monomer material is cured in this state. When a polymer solid electrolyte is produced, the contact between the polymer solid electrolyte and the electrode is poor, which results in poor discharge characteristics, and deterioration of the electrode material due to charge and discharge "(paragraph 0006 of the same document) Based on the knowledge, "in a solid electrolyte battery in which a polymer solid electrolyte is provided between the positive electrode and the negative electrode, the particle size of the electrode material in the positive electrode and / or the negative electrode is large on the interface side with the polymer solid electrolyte. Anti It is to be able to achieve the above object by reducing "(claim 1 of the document) on the side.

  In this document, “the particle diameter of the electrode material is 10 μm or more on the interface side with the polymer solid electrolyte, while the particle diameter on the surface opposite to the interface is 1 μm or less” (claim in the same document). The technical matter with item 2) is disclosed.

Japanese Patent No. 3363676

  As described in Patent Document 1, it is always a challenge to improve the charge / discharge characteristics of the secondary battery. Further, although the charge / discharge characteristics are expected to be improved by making the electrolyte layer thin, the thinning of the electrolyte layer involves a risk of short-circuiting the positive electrode layer and the negative electrode layer. The objective of this invention is providing the technique which improves the charging / discharging characteristic of a secondary battery, without short-circuiting a positive electrode layer and a negative electrode layer.

  In order to solve the above problems, in the first aspect of the present invention, a secondary battery in which a current collector, a positive electrode layer, an electrolyte layer, and a negative electrode layer are sequentially laminated on a substrate, A secondary battery including a positive electrode active material and having an average particle diameter of 2 μm or less of the positive electrode active material included in the entire region of the positive electrode layer or in a partial region located on the electrolyte layer side of the positive electrode layer. provide.

  The average particle size is preferably 0.2 μm or less. The average particle diameter of the positive electrode active material included in the partial area may be smaller than the average particle diameter of the positive electrode active material included in another area of the positive electrode layer other than the partial area. The positive electrode layer may include a first positive electrode layer located on the electrolyte layer side and a second positive electrode layer located on the current collector side. In this case, the positive electrode active material contained in the first positive electrode layer May be smaller than the average particle diameter of the positive electrode active material contained in the second positive electrode layer. The positive electrode layer may be formed by a printing method and then hot pressed.

  In the second aspect of the present invention, a step of forming a current collector on a substrate, a step of forming a positive electrode layer on the current collector, a step of forming an electrolyte layer on the positive electrode layer, And a step of laminating and forming a negative electrode layer on the electrolyte layer, wherein the positive electrode layer contains a positive electrode active material and the entire region of the positive electrode layer or the electrolyte of the positive electrode layer Provided is a secondary battery manufacturing method in which an average particle diameter of the positive electrode active material contained in a partial region located on the layer side is 2 μm or less.

  The average particle size is preferably 0.2 μm or less. The average particle diameter of the positive electrode active material included in the partial area may be smaller than the average particle diameter of the positive electrode active material included in another area of the positive electrode layer other than the partial area. The step of forming the positive electrode layer may include a first step of forming a first positive electrode layer on the current collector and a second step of forming a second positive electrode layer on the first positive electrode layer. In this case, the average particle diameter of the positive electrode active material included in the first positive electrode layer may be smaller than the average particle diameter of the positive electrode active material included in the second positive electrode layer. You may further have the process of hot-pressing the said positive electrode layer between the process of forming the said positive electrode layer, and the process of forming the said electrolyte layer.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is sectional drawing which shows the secondary battery 100 of embodiment. 2 is a cross-sectional view showing a secondary battery 101 which is a modification of the secondary battery 100. FIG. FIG. 6 is a cross-sectional view showing a method for manufacturing secondary battery 100 in the order of steps. FIG. 6 is a cross-sectional view showing a method for manufacturing secondary battery 100 in the order of steps. It is a graph which shows the change of the average particle diameter with respect to the grinding time of lithium manganate. It is a graph which shows the change of the particle size variation with respect to the grinding time of lithium manganate. FIG. 6 is a cross-sectional view showing a method for manufacturing secondary battery 100 in the order of steps. 4 is a graph showing the roughness of the surface of the positive electrode layer in Experimental Example 1. 7 is a graph showing the roughness of the surface of the positive electrode layer in Experimental Example 2. 10 is a graph showing the roughness of the surface of the positive electrode layer in Experimental Example 4. It is a graph which shows the roughness of the surface of the positive electrode layer in a comparative example. 4 is a graph showing the surface roughness when the surface of the positive electrode layer of Experimental Example 1 is hot pressed.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a cross-sectional view illustrating a secondary battery 100 according to an embodiment. In the secondary battery 100, a current collector 104, a positive electrode layer 106, an electrolyte layer 108, and a negative electrode layer 110 are sequentially stacked on a substrate 102.

  The substrate 102 supports the constituent members of the secondary battery 100 such as the current collector 104. As long as the structural member has a mechanical strength that can be supported, the substrate 102 is not limited in material, size, shape, and the like. However, since heat treatment such as firing is performed in the manufacturing process of the secondary battery 100 described later, it is preferable that the battery has heat resistance enough to withstand the heat treatment. Moreover, it is preferable to have chemical stability with respect to the organic solvent, lithium salt, etc. which are used in the manufacturing process of the secondary battery 100. Examples of the substrate 102 include a glass substrate, a metal foil, and a film such as PET (polyethylene terephthalate).

  The current collector 104 is connected to the positive electrode layer 106 and the negative electrode layer 110, and collects and supplies charges from the positive electrode layer 106 and the negative electrode layer 110. The current collector 104 is preferably made of a conductor such as a metal that is chemically stable with respect to the polymer electrolyte contained in the electrolyte layer 108. Examples of the current collector 104 include aluminum, copper, and stainless steel. Note that aluminum and stainless steel are preferable for the current collector 104 connected to the positive electrode layer 106, and copper and stainless steel are preferable for the current collector 104 connected to the negative electrode layer 110.

The positive electrode layer 106 functions as the positive electrode of the secondary battery 100. The positive electrode layer 106 includes a positive electrode active material and a conductive material, and is fixed with a binder. The positive electrode active material is a particulate material, and can be exemplified by lithium-containing composite oxides such as lithium manganate (LiMn ₂ O ₄ ). An example of the conductive material is acetylene black. Examples of the binder include polyethylene oxide (PEO) resin, ethylene / propylene oxide copolymer, and polyvinylidene fluoride (PVdF) resin. When a polyethylene oxide (PEO) resin or ethylene / propylene oxide copolymer is used for the binder, a lithium salt such as lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) may be added to the positive electrode layer 106.

  The positive electrode active material may be included with the same particle diameter over the entire region of the positive electrode layer 106. In this case, the average particle diameter of the positive electrode active material over the entire region of the positive electrode layer 106 is 2 μm or less, preferably 0.2 μm or less. Alternatively, the particle diameter of the positive electrode active material may change in the thickness direction of the positive electrode layer 106. In this case, the average particle diameter of the positive electrode active material included in a partial region located on the electrolyte layer 108 side of the positive electrode layer 106 is 2 μm or less, preferably 0.2 μm or less.

  The average particle diameter of the positive electrode active material contained in the positive electrode layer 106 is set to 2 μm or less, preferably 0.2 μm or less over the entire region of the positive electrode layer 106 or in a partial region located on the electrolyte layer 108 side of the positive electrode layer 106. By setting it to 2 μm or less, the charge / discharge characteristics of the secondary battery 100 can be improved. Moreover, even when the surface roughness of the positive electrode layer 106 is reduced and the electrolyte layer 108 is thin, occurrence of a short circuit between the positive electrode layer 106 and the negative electrode layer 110 can be suppressed.

  When the average particle size of the positive electrode active material is 2 μm or less, preferably 0.2 μm or less in a partial region located on the electrolyte layer 108 side of the positive electrode layer 106, the average particle size of the positive electrode active material contained in the partial region The diameter can be made smaller than the average particle diameter of the positive electrode active material in other regions of the positive electrode layer 106 other than the partial region. That is, in the thickness direction of the positive electrode layer 106, the average particle diameter of the positive electrode active material can be reduced as the distance from the electrolyte layer 108 (side closer to the current collector 104) approaches the electrolyte layer 108.

  Alternatively, as in a secondary battery 101 that is a modification of the secondary battery 100 illustrated in FIG. 2, the positive electrode layer 106 is positioned on the first positive electrode layer 106 a located on the electrolyte layer 108 side and on the current collector 104 side. The average particle diameter of the positive electrode active material contained in the first positive electrode layer 106a can be made smaller than the average particle diameter of the positive electrode active material contained in the second positive electrode layer 106b. In this case, the first positive electrode layer 106a corresponds to the partial region described above, and the average particle diameter of the positive electrode active material contained therein is 2 μm or less, preferably 0.2 μm or less.

  By using a positive electrode active material having a large particle size for the region near the current collector 104 or the second positive electrode layer 106b located on the current collector 104 side, a commercially available positive electrode active material having a large particle size is used as it is. Cost can be reduced. Alternatively, a positive electrode active material having a large particle size can be used, and the degree of freedom in designing the positive electrode layer 106 can be increased.

  The positive electrode layer 106 may be formed by a printing method and then hot pressed. By forming the positive electrode layer 106 by a printing method and hot pressing, the flatness of the positive electrode layer 106 is improved, and the possibility of a short circuit between the positive electrode layer 106 and the negative electrode layer 110 can be further reduced.

The electrolyte layer 108 functions as an electrolyte for the secondary battery 100. The electrolyte layer 108 includes a glass ceramic having a Li ion conductivity and a binder. As a glass ceramics having a Li ion _{conductivity, Li 4-2x Zn x GeO 4 (} LISICON) based solid _{electrolyte, Li-Al-Ti-PO} 4 (LATP) based solid _{electrolyte, Li 1 + X Ge 2-} y Al y P 3 An O ₁₂ (LAGP) -based solid electrolyte can be exemplified. As the binder, a copolymer of ethylene oxide and propylene oxide can be exemplified. A support electrolyte that improves Li ion conductivity may be added to the binder, and examples of the support electrolyte include lithium bis (trifluoromethanesulfonyl) imide (LiTFSI).

  The negative electrode layer 110 functions as the negative electrode of the secondary battery 100. The negative electrode layer 110 is a layer in which a negative electrode active material is fixed with a binder, and may include a carbon-based material. An example of the negative electrode active material is hard carbon. Examples of the binder include polyethylene oxide (PEO) resin, ethylene / propylene oxide copolymer, and polyvinylidene fluoride (PVdF) resin. When a polyethylene oxide (PEO) resin or an ethylene / propylene oxide copolymer is used for the binder, a lithium salt such as lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) may be added to the negative electrode layer 110.

  Hereinafter, a method for manufacturing the secondary battery 100 will be described. 3, 4, and 7 are cross-sectional views illustrating a method for manufacturing the secondary battery 100 in the order of steps.

  First, as shown in FIG. 3, the current collector 104 is formed on the substrate 102. For forming the current collector 104, a plating method, a sputtering method, or the like can be used. For the patterning of the film to be the current collector 104, for example, an etching method such as a metal layer using a photomask or a lift-off method can be used.

  Next, as illustrated in FIG. 4, the positive electrode layer 106 is formed on the current collector 104. The positive electrode layer 106 can be formed by printing and baking. That is, as a paste for printing the positive electrode layer 106, a binder in which a viscosity is adjusted with an appropriate solvent and a positive electrode active material and a conductive material are kneaded is prepared and printed on the pattern of the positive electrode layer 106 by screen printing, for example. The printed pattern is baked, for example, at 120 ° C. for 60 minutes to form the positive electrode layer 106. Printing and baking can be performed in an air atmosphere. In addition, after forming the positive electrode layer 106, the positive electrode layer 106 can be hot-pressed, for example on the conditions of 150 degreeC and 1 minute.

  As described above, a positive electrode active material having an average particle diameter of 2 μm or less, preferably 0.2 μm or less (hereinafter simply referred to as “2 μm or less”) is used. To obtain an average particle size of 2 μm or less, etc., a commercially available positive electrode active material having an average particle size of 2 μm or less is obtained, and a large average particle size of, for example, about 10 μm is obtained and pulverized. Thus, the average particle size may be 2 μm or less.

FIG. 5 is a graph showing the change in average particle size with respect to the pulverization time of lithium manganate (LiMn ₂ O ₄ ) that can be used as the positive electrode active material, and FIG. 6 shows the change in particle size variation with respect to the pulverization time. It is a graph. The pulverization in FIGS. 5 and 6 is ball mill pulverization, and lithium manganate having an average particle diameter of 10 μm, yttria-stable zirconia balls and heptane were charged into an alumina pod, and the alumina pod was rotated at 180 rpm to pulverize the lithium manganate. Is. As shown in FIGS. 5 and 6, lithium manganate having an average particle diameter of 10 μm by ball milling for 12 hours or more is pulverized to an average particle diameter of 0.2 μm or less with a variation of about ± 0.01 μm. be able to. Using the pulverized lithium manganate as the positive electrode active material, the positive electrode layer 106 can be formed.

  Next, as shown in FIG. 7, an electrolyte layer 108 is formed on the positive electrode layer 106. The electrolyte layer 108 can be formed by printing and baking. That is, as a paste for printing the electrolyte layer 108, a binder prepared by kneading glass ceramics as an electrolyte with a binder whose viscosity is adjusted with an appropriate solvent is prepared, and printed on the pattern of the electrolyte layer 108 by, for example, screen printing. Examples of the binder include a copolymer of ethylene oxide and propylene oxide, and a supporting electrolyte that improves Li ion conductivity may be added. As the supporting electrolyte, lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) ). The printed pattern is baked, for example, at 100 ° C. for 10 minutes to form the electrolyte layer 108.

  Finally, the secondary battery 100 shown in FIG. 1 can be manufactured by stacking the negative electrode layer 110 on the electrolyte layer 108. The negative electrode layer 110 can be formed by printing and baking. That is, as a paste for printing the negative electrode layer 110, a negative electrode active material is kneaded into a binder (for example, polyvinylidene fluoride (PVdF) resin) whose viscosity is adjusted with an appropriate solvent (for example, N-methyl-2-pyrrolidinone). This is prepared and printed on the pattern of the negative electrode layer 110 by, for example, screen printing. The printed pattern is baked, for example, at 120 ° C. for 60 minutes to form the negative electrode layer 110. As described above, the secondary battery 100 shown in FIG. 1 is manufactured. The manufactured secondary battery 100 may be further subjected to vacuum heat drying treatment at 100 ° C. for about 24 hours.

  Note that the secondary battery 101 can be manufactured in the same manner as the secondary battery 100, and the first positive electrode layer 106a and the second positive electrode layer 106b in the secondary battery 101 are manufactured in the same manner as the positive electrode layer 106 described above. Can do.

  According to the secondary battery 100, the secondary battery 101, and the manufacturing method thereof of the present embodiment, the average particle diameter of the positive electrode active material contained in the positive electrode layer 106 is set over the entire region of the positive electrode layer 106 or the positive electrode. In a partial region of the layer 106 located on the electrolyte layer 108 side, the charge / discharge characteristics of the secondary battery 100 can be improved by setting it to 2 μm or less, preferably 0.2 μm or less. Moreover, even when the surface roughness of the positive electrode layer 106 is reduced and the electrolyte layer 108 is thin, occurrence of a short circuit between the positive electrode layer 106 and the negative electrode layer 110 can be suppressed. Further, by using a positive electrode active material having a large particle size for the region near the current collector 104 or the second positive electrode layer 106b located on the current collector 104 side, a commercially available positive electrode active material having a large particle size is used as it is. Manufacturing costs can be reduced. Alternatively, a positive electrode active material having a large particle size can be used, and the degree of freedom in designing the positive electrode layer 106 can be increased. Furthermore, by forming the positive electrode layer 106 by a printing method and hot pressing, the flatness of the positive electrode layer 106 is improved, and the possibility of a short circuit between the positive electrode layer 106 and the negative electrode layer 110 can be further reduced.

(Example)
A commercially available lithium manganate (A) having an average particle diameter of 10 μm and a commercially available lithium manganate (B) having an average particle diameter of 0.1 μm were obtained, and a ball mill for 0.5 hours was added to the commercially available lithium manganate (A). A pulverized product (A) having an average particle diameter of 1 μm by pulverization and a pulverized product (B) having an average particle diameter of 0.2 μm by subjecting lithium manganate (A) to ball milling for 12 hours. It was.

  In the preparation of the paste for printing the positive electrode layer 106 in the method for manufacturing the secondary battery 100 described above, a pulverized product (B) having an average particle size of 0.2 μm was used as the positive electrode active material. A secondary battery 100 was fabricated using Experimental Example 2 using 1 μm of commercially available lithium manganate (B) and Experimental Example 3 using a pulverized product (A) having an average particle diameter of 1 μm. In addition, a pulverized product (B) having an average particle size of 0.2 μm is used as the positive electrode active material of the first positive electrode layer 106a in the secondary battery 101, and a commercially available manganic acid having an average particle size of 10 μm is used as the positive electrode active material of the second positive electrode layer 106b. A secondary battery 101 using lithium (A) was produced and was experimental example 4. A secondary battery using a commercially available lithium manganate (A) having an average particle size of 10 μm as a positive electrode active material was prepared as a comparative example.

  In order to evaluate the charge / discharge characteristics of the secondary batteries produced as Examples 1 to 4 and the comparative example, the charge end time and the discharge end time in the initial state (second charge / discharge number) were measured. The charging end time was a time required for the charging current to reach a constant current of 0.1 mA after the discharge was completed and the voltage reached 4.1V. The discharge end time was defined as the time required for the discharge current to reach a constant current of 0.1 mA after the completion of charging and the voltage reached 1.0V. Further, a plurality of secondary batteries of Examples 1 to 4 and Comparative Example were manufactured, and those that initially operated were regarded as non-defective products, those that did not initially operate were regarded as defective products, and the non-defective product ratio = number of non-defective products / number of products manufactured was determined.

Table 1 shows the charge end time, the discharge end time, and the non-defective rate in Examples 1 to 4 and the comparative example.

  In the comparative example, the non-defective product rate is low, and the charging end time and the discharging end time cannot be measured normally, whereas in the experimental examples 1 to 4, the non-defective product rate is 100%, which indicates that there is no problem in the initial operation. From the results of Experimental Examples 1 to 3, it can be seen that the smaller the average particle diameter of the positive electrode active material, the longer the charge end time and the discharge end time, and the better the charge / discharge characteristics. From comparison between Experimental Examples 1 and 3 and Experimental Example 2, it can be said that the pulverized material is superior in charge / discharge characteristics than the positive electrode active material purchased as a product as it is. From the results of Experimental Example 4 and Comparative Example, the positive electrode active material having a large average particle size of 10 μm does not operate normally. It can also be seen that it is improved.

  8, FIG. 9, FIG. 10, and FIG. 11 are graphs showing the roughness of the surface of the positive electrode layer in Experimental Example 1, Experimental Example 2, Experimental Example 4, and Comparative Example, respectively. The surface roughness of Comparative Example is ± 10 μm, whereas the surface roughness in Experimental Example 1, Experimental Example 2 and Experimental Example 4 is ± 3 μm, ± 2 μm and ± 3 μm, respectively. It is considered that the low surface roughness contributes to the suppression of short circuit between the positive electrode layer 106 and the negative electrode layer 110, leading to an improvement in the defect rate. FIG. 12 is a graph showing the surface roughness when the positive electrode layer surface of Experimental Example 1 is hot-pressed. By hot pressing, the surface roughness is reduced to ± 2 μm, and the possibility of a short circuit between the positive electrode layer 106 and the negative electrode layer 110 is considered to be lower.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100,101 ... Secondary battery 102 ... Board | substrate 104 ... Current collector 106 ... Positive electrode layer 106a ... 1st positive electrode layer 106b ... 2nd positive electrode layer 108 ... Electrolyte layer 110 ... Negative electrode layer

Claims (10)

A secondary battery in which a current collector, a positive electrode layer, an electrolyte layer, and a negative electrode layer are sequentially laminated on a substrate,
The positive electrode layer includes a positive electrode active material,
The secondary battery in which an average particle diameter of the positive electrode active material contained in the entire region of the positive electrode layer or in a partial region located on the electrolyte layer side of the positive electrode layer is 2 μm or less. The secondary battery according to claim 1, wherein the average particle size is 0.2 μm or less. The average particle size of the positive electrode active material included in the partial region is smaller than the average particle size of the positive electrode active material included in another region of the positive electrode layer other than the partial region. Secondary battery described in 1. The positive electrode layer has a first positive electrode layer located on the electrolyte layer side and a second positive electrode layer located on the current collector side;
The secondary battery according to claim 1, wherein an average particle diameter of the positive electrode active material included in the first positive electrode layer is smaller than an average particle diameter of the positive electrode active material included in the second positive electrode layer. The secondary battery according to any one of claims 1 to 4, wherein the positive electrode layer is formed by a printing method and then hot-pressed. Forming a current collector on the substrate; forming a positive electrode layer on the current collector; forming an electrolyte layer on the positive electrode layer; and laminating a negative electrode layer on the electrolyte layer. A process for producing a secondary battery comprising:
The positive electrode layer includes a positive electrode active material,
The method for producing a secondary battery, wherein an average particle diameter of the positive electrode active material contained in the entire region of the positive electrode layer or a partial region located on the electrolyte layer side of the positive electrode layer is 2 μm or less. The method for manufacturing a secondary battery according to claim 6, wherein the average particle size is 0.2 μm or less. The average particle diameter of the positive electrode active material included in the partial area is smaller than the average particle diameter of the positive electrode active material included in another area of the positive electrode layer other than the partial area. The manufacturing method of the secondary battery as described in any one of. The step of forming the positive electrode layer includes a first step of forming a first positive electrode layer on the current collector, and a second step of forming a second positive electrode layer on the first positive electrode layer;
The secondary battery according to claim 6 or 7, wherein an average particle diameter of the positive electrode active material included in the first positive electrode layer is smaller than an average particle diameter of the positive electrode active material included in the second positive electrode layer. Production method. The secondary battery according to claim 6, further comprising a step of hot pressing the positive electrode layer between the step of forming the positive electrode layer and the step of forming the electrolyte layer. Manufacturing method.