Battery and method of manufacturing the same

Abstract

The present disclosure provides a battery including a first electrode, a second electrode, and a separator. The first electrode includes a first main surface and a second main surface. A plurality of through-holes are formed in the first electrode. The through-holes pass through the first electrode from the first main surface to the second main surface. The separator covers inner walls of the through-holes. The second electrode is disposed in the through-holes. The separator includes a first layer and a second layer. The first layer is disposed between the inner walls and the second layer. The first layer includes a first inorganic particle group having a first average particle diameter. The second layer includes a second inorganic particle group having a second average particle diameter. The second average particle diameter is smaller than the first average particle diameter. The purpose of the present disclosure is to reduce voids in the coated separator formed on the inner walls of the through-holes.

Description

Technical Field

[0001] This disclosure relates to batteries and methods for manufacturing them. Background Technology

[0002] Japanese Patent Application Publication No. 2020-123484 discloses an electrode having multiple through holes and a diaphragm layer stacked on the inner wall of the through holes. Summary of the Invention

[0003] The battery comprises a first electrode and a second electrode. The polarity of the second electrode differs from that of the first electrode. To prevent contact between the first and second electrodes, a separator is placed between them. The separator is electrically insulating. The separator is porous and allows ion permeability. Generally, electrodes are sheet-like. Corresponding to sheet-like electrodes, membrane-like separators are used. For example, microporous membranes made of polyolefins are becoming increasingly popular as separators.

[0004] Electrodes with special structures are also under investigation. For example, a through-hole is formed on the first electrode. The inner wall of the through-hole is covered by a diaphragm. A second electrode is disposed within the through-hole, whose inner wall is covered by a diaphragm. Because the electrodes are not sheet-like, it is difficult to prevent contact between the first and second electrodes using a membrane-like diaphragm.

[0005] Therefore, for example, a coated diaphragm can be considered. That is, a coated diaphragm can be formed by coating the inner wall of the through-hole with a group of inorganic particles. However, according to the novel insights of this disclosure, there is a tendency for voids (bubbles) to remain in the coated diaphragm formed on the inner wall of the through-hole. At the location of voids, a local decrease in insulation strength may occur. For example, a short circuit path may be formed because a part of the electrode intrudes into the void. For example, pinholes may also be formed due to voids.

[0006] The purpose of this disclosure is to reduce voids in a coated diaphragm formed on the inner wall of a through hole.

[0007] The technical solution and effects of this disclosure are described below. However, the mechanism of action in this specification includes conjecture. The mechanism of action does not limit the technical scope of this disclosure.

[0008] 1. The battery includes a first electrode, a second electrode, and a separator. The first electrode includes a first main surface and a second main surface. The second main surface is the opposite side of the first main surface. A plurality of through holes are formed on the first electrode. The through holes extend from the first main surface through the first electrode to the second main surface.

[0009] A diaphragm covers the inner wall of the through-hole. The polarity of the second electrode is different from that of the first electrode. The second electrode is disposed within the through-hole. The second electrode extends along the axial direction of the through-hole.

[0010] The membrane comprises a first layer having a first thickness and a second layer having a second thickness. The first layer is disposed between the inner wall and the second layer. The first layer comprises a first group of inorganic particles having a first average particle size. The second layer comprises a second group of inorganic particles having a second average particle size. The second average particle size is smaller than the first average particle size.

[0011] In coated separators, the smaller the particle size of the inorganic particle clusters, the smaller the porosity tends to be. Therefore, by using inorganic particle clusters with small particle sizes, a reduction in porosity can be expected. However, the smaller the particle size of the inorganic particle clusters, the denser the coated separator becomes, which may decrease ion permeability. That is, the battery resistance will increase.

[0012] In the battery described in "1." above, the separator comprises a first layer and a second layer. The first layer (lower layer) is closer to the inner wall than the second layer (upper layer). The first layer is formed from a first group of inorganic particles (large particle group). The second layer is formed from a second group of inorganic particles (small particle group). When forming the second layer, a portion of the voids in the first layer can be filled with the small particle group. That is, it is believed that voids can be reduced. Furthermore, since the first layer is formed from large particle groups, the separator can be moderately sparse. Therefore, the increase in battery resistance can be reduced.

[0013] 2. The first electrode can also be formed into a honeycomb core material, for example.

[0014] That is, in the cross-section of the first electrode orthogonal to the axial direction, the through-holes can also be filled into a honeycomb pattern. As a special type of electrode, a honeycomb structure electrode is expected to be used. By giving the electrode a honeycomb structure, an increase in reaction area and an increase in active material density can be expected. That is, a combination of good input-output performance and high energy density can be expected.

[0015] It is believed that when the first electrode has a honeycomb structure, it is difficult to apply diaphragms other than coated diaphragms. It is also believed that when the first electrode has a honeycomb structure, it is difficult to detect defects in the coated diaphragm formed on the inner wall of the through-hole. Furthermore, it is considered difficult to remove defects in the coated diaphragm without damaging the honeycomb structure. It is believed that the diaphragm described in "1." above is effective for electrodes with a honeycomb structure.

[0016] 3. Voids can also be formed in the first layer. These voids can also be filled with a portion of the second inorganic particle group.

[0017] 4. The second average particle size may also be smaller than the first thickness.

[0018] Although the mechanism is not yet clear, the size of the voids depends on the thickness of the first layer (the first thickness). By making the particle size of the second inorganic particle group smaller than the first thickness, it is expected that the second inorganic particle group can easily fill the voids.

[0019] 5. The ratio of the second average particle size to the first thickness can, for example, be less than 1 / 300. This is because a reduction in voids can be expected.

[0020] 6. The first average particle size can also be, for example, 0.3 to 2 μm.

[0021] 7. The first thickness can also be, for example, 10 to 150 μm.

[0022] 8. The second thickness can also be less than 30 μm, for example.

[0023] 9. The ratio of the second thickness to the first thickness can also be, for example, 0.5 or less. This is because it can reduce the increase in battery resistance.

[0024] 10. The first layer may also contain a first adhesive. The second layer may also contain a second adhesive.

[0025] 11. The first inorganic particle group and the second inorganic particle group may, for example, each independently comprise at least one selected from alumina, alumina hydrate, aluminum hydroxide and titanium oxide.

[0026] 12. The first electrode may also be columnar, for example. The first main surface and the second main surface may also be located at opposite ends of the first electrode along its axial direction.

[0027] 13. Batteries may also contain electrolyte.

[0028] 14. A method for manufacturing a battery, comprising the following steps (a) to (c).

[0029] Process (a): Prepare to form the first electrode with multiple through holes.

[0030] Step (b): Forming a diaphragm covering the inner wall of the through hole.

[0031] Step (c): After step (b) above, a second electrode is placed inside the through hole.

[0032] The above process (b) includes the following steps (b1) and (b2).

[0033] Step (b1): The first layer is formed by applying the first paste to the inner wall of the through hole.

[0034] Step (b2): The second layer is formed by applying the second paste to the surface of the first layer.

[0035] The polarity of the second electrode is different from that of the first electrode. The first paste contains a first group of inorganic particles with a first average particle size. The second paste contains a second group of inorganic particles with a second average particle size. The second average particle size is smaller than the first average particle size.

[0036] The battery described in "1." can be manufactured using the manufacturing method described in "1." above.

[0037] 15. The first electrode comprises a first main surface and a second main surface. The second main surface is the opposite surface of the first main surface. A through hole extends from the first main surface through the first electrode to the second main surface.

[0038] The above step (b1) may also include: drawing the first paste from the first main surface or the second main surface.

[0039] The above step (b2) may also include: drawing the second paste from the first main surface or the second main surface.

[0040] The paste can be applied to the inner wall of the through hole by drawing paste into it.

[0041] 16. The first paste may also further comprise a first adhesive and a first dispersion medium. The second paste may also further comprise a second adhesive and a second dispersion medium.

[0042] 17. The battery manufacturing method may also include the following step (d).

[0043] Process (d): Allow the electrolyte to permeate the diaphragm.

[0044] The following describes embodiments of the present disclosure (hereinafter referred to as "the present embodiments") and examples of the present disclosure (hereinafter referred to as "the examples"). However, the present embodiments and examples do not limit the technical scope of the present disclosure. Attached Figure Description

[0045] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals denote like elements.

[0046] Figure 1 This is a schematic diagram showing an example of a battery in this embodiment.

[0047] Figure 2 This is a schematic diagram showing an example of the first electrode.

[0048] Figure 3 This is a schematic cross-sectional view showing the first example of a through hole.

[0049] Figure 4 This is a schematic cross-sectional view showing the second example of a through hole.

[0050] Figure 5 This is a schematic cross-sectional view of the battery element.

[0051] Figure 6 This is a rough cross-sectional view of the diaphragm.

[0052] Figure 7This is a schematic flowchart of the battery manufacturing method according to this embodiment.

[0053] Figure 8 Figure 1 shows the formation process of the diaphragm in this embodiment.

[0054] Figure 9 Figure 2 shows the membrane formation process of this embodiment. Detailed Implementation

[0055] <Definitions of terms, etc.>

[0056] In this specification, the terms "possessing," "comprises," "have," and variations thereof (e.g., "consisting of," etc.) are open-ended. An open-ended description may include additional requirements in addition to essential requirements, or it may not include additional requirements. The description "composed of," is closed-ended. However, even in a closed-ended description, impurities and additional requirements unrelated to the present disclosure are not excluded. The description "substantially composed of," is semi-closed-ended. In a semi-closed-ended description, it is permissible to add requirements that do not substantially affect the essential or novel characteristics of the present disclosure.

[0057] In this specification, expressions such as "may also" and "may" are not used in a sense of obligation ("must do so"), but rather in a sense of permission ("has this possibility").

[0058] In this specification, the order of execution of the various steps, actions, and operations involved in the methods is not limited to the order in which they are described, unless otherwise specified. For example, multiple steps may be performed simultaneously. For example, multiple steps may be performed sequentially.

[0059] Geometric terms used in this specification (such as "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted strictly. For example, "parallel" may deviate slightly from the strict meaning of "parallel." Geometric terms used in this specification may include tolerances and errors in design, operation, manufacturing, etc. Dimensional relationships in the drawings may sometimes differ from actual dimensional relationships. To aid in understanding the technology disclosed herein, dimensional relationships (length, width, thickness, etc.) in the drawings have sometimes been altered. Furthermore, parts of the structure may sometimes be omitted.

[0060] In this specification, numerical ranges such as "m~n%" include both upper and lower limits unless otherwise specified. That is, "m~n%" represents a numerical range of "m% and below n%". Furthermore, "m% and below n%" includes "more than m% and less than n%". Moreover, any value arbitrarily selected from the numerical range can be used as a new upper or lower limit. For example, a new numerical range can be set by arbitrarily combining values ​​within the numerical range with values ​​recorded in other parts of this specification, tables, figures, etc.

[0061] In this specification, all numerical values ​​are modified by the term "about". The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that vary depending on the application of the technology disclosed herein. All numerical values ​​may be expressed in significant figures. The measured value may be the average of multiple measurements. The number of measurements may be 3 or more, 5 or more, or 10 or more. Generally, the more measurements, the higher the reliability of the average value can be expected. The measured value may be rounded based on the number of significant figures. The measured value may include, for example, errors such as the detection limits of the accompanying measuring device.

[0062] In this specification, when a compound is represented by a stoichiometric formula (e.g., "LiCoO2"), the stoichiometric formula is merely a representative example of the compound. Compounds may have non-stoichiometric compositions. For example, when lithium cobalt oxide is represented as "LiCoO2," unless otherwise specified, lithium cobalt oxide is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2," and may contain Li, Co, and O in any composition ratio. Furthermore, trace element doping, substitution, etc., are also permitted.

[0063] In this specification, "fraction of solids" refers to the total mass fraction of solid components in a coating (e.g., paste). Furthermore, components dissolved in the dispersion medium are considered solid components.

[0064] In this specification, "average particle size" refers to the particle size at which the cumulative frequency from the smallest particle size side reaches 50% in a volume-based particle size distribution. The average particle size can be determined using laser diffraction.

[0065] The term "battery" in this specification can refer to any battery system. In this embodiment, as an example, a lithium-ion battery will be described. The polarity of the second electrode is different from that of the first electrode. The first electrode can be either a positive or a negative electrode. In this embodiment, as an example, a negative electrode will be described.

[0066] <Battery>

[0067] Figure 1This is a schematic diagram illustrating an example of the battery in this embodiment. Hereinafter, "the battery in this embodiment" may be simply referred to as "this battery". This battery 100 includes a battery element 50. This battery 100 may also include, for example, an electrolyte, an outer casing, etc. (none shown). The outer casing can house the battery element 50 and the electrolyte. The outer casing may be, for example, a metal container, or a small bag made of metal foil laminate. The electrolyte can be immersed in the battery element 50. The battery element 50 includes a first electrode 10, a second electrode 20, and a separator 30. The battery element 50 may also include a current collector, terminals, etc. (none shown).

[0068] Electrode 1

[0069] Figure 2 This is a schematic diagram showing an example of the first electrode. The first electrode 10 can have any shape. The first electrode 10 can be, for example, cylindrical or prismatic.

[0070] exist Figure 2 In this embodiment, the first electrode 10 extends along the Z-axis. The direction in which the first electrode 10 extends is also referred to as the "axial direction". In this embodiment, the cross section orthogonal to the axial direction is also referred to as the "XY plane". The cross section parallel to the axial direction is also referred to as the "YZ plane".

[0071] The first electrode 10 has a diameter d. Diameter d represents the maximum width in the XY plane. Diameter d can be, for example, 1–1000 mm, or 10–100 mm. The first electrode 10 has a height h. Height h represents the maximum width in the YZ plane. Height h can be, for example, 1–1000 mm, 5–500 mm, or 10–100 mm. The ratio of height h to diameter d can be, for example, 0.1–10, or 0.1–1.

[0072] In this battery 100, the first electrode 10 is the negative electrode. The first electrode 10 contains a negative electrode active material. The first electrode 10 may also contain a conductive material, a binder, etc. For example, the first electrode 10 may contain 1 to 10% binder, 0 to 10% conductive material, and the balance negative electrode active material by mass fraction.

[0073] The negative electrode active material may contain optional components. For example, it may contain at least one selected from graphite, soft carbon, hard carbon, silicon, silicon oxide, tin, tin oxide, and lithium titanate. The conductive material may contain, for example, acetylene black, carbon nanotubes, etc. The binder may contain, for example, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), etc.

[0074] The first electrode 10 includes a first principal surface 11 and a second principal surface 12. The first principal surface 11 and the second principal surface 12 are disposed at opposite ends in the axial direction. The second principal surface 12 is the opposite surface of the first principal surface 11. The first principal surface 11 and the second principal surface 12 may or may not be parallel to the XY plane. The first principal surface 11 and the second principal surface 12 may or may not be flat or curved.

[0075] A plurality of through holes 13 are formed in the first electrode 10. The plurality of through holes 13 can be arranged regularly or randomly. For example, the plurality of through holes 13 can be formed in a honeycomb pattern. That is, the first electrode 10 can also be formed as a honeycomb core material. In the XY plane, the density of the through holes 13 can, for example, be 0.1 to 10 holes / mm. 2 .

[0076] The through-hole 13 extends from the first main surface 11 through the first electrode 10 to the second main surface 12. That is, the through-hole 13 has openings on both the first main surface 11 and the second main surface 12. The extending direction (axial direction) of the plurality of through-holes 13 can also be parallel to the axial direction of the first electrode 10. In the XY plane, the through-hole 13 can have any cross-sectional shape. The cross-sectional shape of the through-hole 13 can be, for example, circular or polygonal. The polygon can be, for example, a 3- to 12-sided polygon. The polygon can be a regular polygon.

[0077] Figure 3 This is a schematic cross-sectional view showing the first example of a through hole. In the XY plane, the cross-sectional shape of the through hole 13 can also be, for example, a quadrilateral. "Diameter" indicates the maximum width of the through hole 13 in the XY plane. The diameter of the through hole 13 can be, for example, 0.1 to 10 mm, 0.5 to 5 mm, or 1 to 3 mm.

[0078] The walls that separate the through holes 13 are also called "ribs". In the XY plane, the ribs can extend, for example, in a mesh-like manner. The thickness of the ribs can be, for example, 50 to 500 μm, or 100 to 300 μm.

[0079] Figure 4 This is a schematic cross-sectional view showing the second example of a through-hole. In the XY plane, the planar shape of the through-hole 13 can also be, for example, hexagonal. By making the planar shape of the through-hole 13 hexagonal, for example, the tendency to mitigate deformation associated with charging and discharging is mitigated.

[0080] Diaphragm

[0081] Figure 5 This is a schematic cross-sectional view of the battery element. A separator 30 covers the inner wall of the through-hole 13. The separator 30 is located between the first electrode 10 and the second electrode 20. The separator 30 extends in a manner that separates the second electrode 20 from the first electrode 10.

[0082] Figure 6 It is a schematic cross-sectional view of the separator. The separator 30 includes a first layer 31 and a second layer 32. The first layer 31 is disposed between the inner wall of the through-hole 13 (the first electrode 10) and the second layer 32. The first layer 31 may be in direct contact with the inner wall. The second layer 32 may be in direct contact with the first layer 31. The second layer 32 may be in direct contact with the second electrode 20.

[0083] The first layer 31 has a first thickness T1. The second layer 32 has a second thickness T2. The second thickness T2 may be, for example, equal to or less than the first thickness T1. That is, the relationship of "T2 / T1≤1" may be satisfied, the relationship of "T2 / T1<1" may be satisfied, the relationship of "T2 / T1≤0.9" may be satisfied, the relationship of "T2 / T1≤0.6" may be satisfied, and the relationship of "T2 / T1≤0.5" may also be satisfied. By satisfying the relationship of "T2 / T1≤0.5", an increase in battery resistance can be alleviated. For example, the relationship of "0.3≤T2 / T1" may also be satisfied.

[0084] The first thickness T1 may be, for example, 10 to 150 μm, 30 to 100 μm, or 30 to 70 μm. The second thickness T2 may be, for example, 1 to 60 μm, 10 to 40 μm, or 10 to 30 μm.

[0085] The first layer 31 includes a first inorganic particle group 1. The first inorganic particle group 1 has a first average particle diameter D150. The second layer 32 includes a second inorganic particle group 2. The second inorganic particle group 2 has a second average particle diameter D250. The second average particle diameter D250 is smaller than the first average particle diameter D150. That is, the relationship of "D250<D150" is satisfied. For example, the relationship of "0<D250 / D150<1" may be satisfied, the relationship of "0.1<D250 / D150<1" may be satisfied, the relationship of "0.125≤D250 / D150≤0.5" may be satisfied, and the relationship of "0.125≤D250 / D150≤0.25" may also be satisfied.

[0086] The first average particle diameter D150 may be, for example, 0.3 to 2 μm, or 0.8 to 1.5 μm. The second average particle diameter D250 may be, for example, 0.05 to 0.3 μm, or 0.1 to 0.2 μm.

[0087] Void 3 may be formed in the first layer 31. Part of the second inorganic particle group 2 may also be filled in the void 3. By filling the void 3 with part of the second inorganic particle group 2, an improvement in short-circuit resistance can be expected. Table 1 below shows the relationship between the first thickness T1 and the average diameter of the void 3. The average diameter of the void 3 can be measured in the X-ray CT image.

[0088] Table 1

[0089]

[0090] As shown in Table 1 above, the size of the pore 3 tends to depend on the first thickness T1. For example, the second average particle size D250 of the second inorganic particle group 2 can be smaller than the first thickness T1. Therefore, it is expected that the second inorganic particle group 2 can easily enter the pore 3.

[0091] The average diameter of the void 3 can be 1 / 2 to 1 / 3 of the first thickness T1. The second average particle size D250 of the second inorganic particle group 2 can be, for example, less than 1 / 2 of the first thickness T1. That is, the relationship "D250 / T1≤1 / 2" can also be satisfied. For example, the relationship "D250 / T1≤1 / 3", "D250 / T1≤1 / 10", "D250 / T1≤1 / 100", and "D250 / T1≤1 / 300" can be satisfied. By satisfying the relationship "D250 / T1≤1 / 300", an improvement in short-circuit withstand capability can be expected.

[0092] The first inorganic particle group 1 and the second inorganic particle group 2 comprise electrically insulating inorganic compounds. The first inorganic particle group 1 and the second inorganic particle group 2 may have the same composition or different compositions. For example, the first inorganic particle group 1 and the second inorganic particle group 2 may each independently comprise at least one selected from alumina, alumina hydrate, aluminum hydroxide, and titanium dioxide. For example, the first inorganic particle group 1 and the second inorganic particle group 2 may each independently comprise at least one selected from alumina, boehmite, gibbsite, and titanium dioxide.

[0093] The first layer 31 may further include a first adhesive (not shown). The second layer 32 may further include a second adhesive (not shown). The first adhesive and the second adhesive may have the same composition or different compositions. The first adhesive and the second adhesive each independently include at least one selected from polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polytetrafluoroethylene (PTFE).

[0094] The first layer 31 may, for example, contain 1 to 20% by mass of a first adhesive and the balance of a first inorganic particle group 1. The second layer 32 may, for example, contain 1 to 20% by mass of a second adhesive and the balance of a second inorganic particle group 2.

[0095] The Second Electrode

[0096] The second electrode 20 is disposed within the through hole 13. The second electrode 20 may be pillar-shaped. The second electrode 20 extends along the axial direction of the through hole 13. The second electrode 20 may also extend to the outside of the through hole 13.

[0097] In this battery 100, the second electrode 20 is the positive electrode. The second electrode 20 contains a positive electrode active material. The second electrode 20 may also contain conductive materials, binders, etc. For example, the second electrode 20 may contain 1 to 10% binder, 1 to 10% conductive material, and the balance positive electrode active material by mass fraction.

[0098] The positive electrode active material may contain optional components. For example, the positive electrode active material may contain at least one selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium iron phosphate. The conductive material may contain, for example, acetylene black. The binder may contain, for example, PVDF.

[0099] Electrolyte

[0100] This battery 100 may also contain an electrolyte. The electrolyte comprises a supporting electrolyte and a solvent. The supporting electrolyte is dissolved in the solvent. The supporting electrolyte may contain optional components. For example, the supporting electrolyte may contain at least one selected from LiPF6, LiBF4, and Li(FSO2)2N. The concentration of the supporting electrolyte may be, for example, 0.5 to 2 mol / kg.

[0101] The solvent is aprotic. The solvent may contain optional components. For example, the solvent may be at least one selected from ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). In addition to the supporting electrolyte and solvent, the electrolyte may also contain optional additives.

[0102] <Battery Manufacturing Methods>

[0103] Figure 7 This is a schematic flowchart of the battery manufacturing method according to this embodiment. Hereinafter, "the battery manufacturing method according to this embodiment" may be simply referred to as "this manufacturing method". This manufacturing method includes "(a) preparation of the first electrode", "(b) formation of the separator" and "(c) arrangement of the second electrode". This manufacturing method may further include, for example, "(d) impregnation of electrolyte".

[0104] (a) Preparation of the first electrode

[0105] This manufacturing method includes the preparation of a first electrode 10. A plurality of through holes 13 are formed on the first electrode 10. The first electrode 10 can be prepared by any method. For example, the first electrode 10 can be prepared by extrusion molding.

[0106] For example, a negative electrode paste is prepared by mixing a negative electrode active material, a binder, and a dispersion medium. For example, a suitable dispersion medium can be selected depending on the type of binder. The dispersion medium may contain, for example, water. A mold is prepared. The mold has an extrusion orifice (die). The shape of the extrusion orifice corresponds to that of the first electrode 10. A shaped body is formed by extruding the negative electrode paste from the extrusion orifice. The shaped body is formed to have a plurality of through holes 13. The first electrode 10 can be prepared by drying the shaped body.

[0107] (b) Formation of the diaphragm

[0108] This manufacturing method includes the formation of a diaphragm 30. The diaphragm 30 covers the inner wall of the through hole 13. That is, this manufacturing method includes "(b1) formation of the first layer" and "(b2) formation of the second layer".

[0109] (b1) Formation of the first layer

[0110] This manufacturing method involves forming a first layer 31 by applying a first paste to the inner wall of the through hole 13. The first paste contains a first inorganic particle group 1. The first paste may also contain a first binder and a first dispersion medium. For example, the first paste can be prepared by mixing the first inorganic particle group 1, the first binder, and the first dispersion medium. For example, an appropriate material can be selected as the first dispersion medium depending on the type of the first binder, etc. The first dispersion medium may also contain, for example, N-methyl-2-pyrrolidone (NMP), etc.

[0111] The coating method is arbitrary. For example, the first paste can be drawn from either the first main surface 11 or the second main surface 12. For example, the first paste can be placed on the first main surface 11. For example, the first paste can also be drawn from the second main surface 12 side using a vacuum pump or the like. Thus, the first paste can adhere to the inner wall of the through hole 13. Hereinafter, this method is also referred to as the "drawing method". The drawing method is suitable as a method for coating paste on the inner wall of the through hole 13. On the other hand, if the drawing method is used, gas (bubbles) may easily be mixed into the paste. The gas mixed into the paste may form voids 3. In this manufacturing method, voids 3 can be reduced by sequentially forming the first layer 31 and the second layer 32.

[0112] A first layer 31 can be formed by drying the first paste adhering to the inner wall. The first thickness T1 of the first layer 31 can be adjusted, for example, by the solid content fraction of the first paste. There is a tendency that the lower the solid content fraction, the thinner the first thickness T1. The solid content fraction of the first paste can be, for example, 45-65%, or 55-65%.

[0113] (b2) Formation of the second layer

[0114] This manufacturing method involves forming a second layer 32 by coating a second paste onto the surface of the first layer 31. The second paste contains a second group of inorganic particles 2. The second paste may also contain a second binder and a second dispersion medium. For example, the second paste can be prepared by mixing the second group of inorganic particles 2, the second binder, and the second dispersion medium. For example, an appropriate material can be selected as the second dispersion medium depending on the type of the second binder, etc. The second dispersion medium may also contain, for example, NMP, etc.

[0115] The second paste can also be applied using an attraction method. That is, the second paste can be attracted from either the first main surface 11 or the second main surface 12. Thus, the second paste can adhere to the surface of the first layer 31. The second layer 32 can be formed by drying the second paste adhered to the first layer 31. The second thickness T2 of the second layer 32 can be adjusted, for example, by the solid content fraction of the second paste. The solid content fraction of the second paste can be, for example, 45–65%, or 45–55%.

[0116] (c) Configuration of the second electrode

[0117] This manufacturing method includes, after forming the diaphragm 30, arranging the second electrode 20 within the through hole 13.

[0118] For example, the ends (first main surface 11 and second main surface 12) can be insulated before the second electrode 20 is disposed. For example, resin particle groups can be attached to the ends by electrodeposition or the like. This forms an insulating film (not shown). When the second electrode 20 is inserted into the through hole, the insulating film prevents contact between the second electrode 20 and the first electrode 10. The resin particle groups may, for example, contain polyimide.

[0119] The second electrode 20 can be configured using any method. For example, a positive electrode paste can be prepared by mixing a positive electrode active material, a conductive material, a binder, and a dispersion medium. Alternatively, the positive electrode paste can be pressed into the through-hole 13. This allows the through-hole 13 to be filled with the positive electrode paste. The second electrode 20 can be formed by drying the positive electrode paste.

[0120] As described above, a battery element 50 can be formed. Current collectors can also be mounted on the battery element 50. For example, a metal wire can be wound around the side of the first electrode 10. The metal wire can function as a current collector for the first electrode 10. For example, a metal foil can also be pasted onto at least one of the first main surface 11 and the second main surface 12. The metal foil is in contact with the second electrode 20. The metal foil can function as a current collector for the second electrode 20. Furthermore, terminals can be connected to each current collector.

[0121] (d) Electrolyte Impregnation

[0122] This manufacturing method may also include impregnating the separator 30 with an electrolyte. For example, an outer casing is prepared. The battery element 50 is housed in the outer casing. An electrolyte is injected into the outer casing. After injecting the electrolyte, the outer casing is sealed. The electrolyte can then impregnate the separator 30. As described above, the battery 100 can be manufactured.

[0123] <Manufacturing of the Experimental Battery>

[0124] As described below, test batteries No.1 to No.9 were manufactured. Hereinafter, for example, "test battery No.1" may be simply referred to as "No.1".

[0125] No.1

[0126] (a) Preparation of the first electrode

[0127] The following materials have been prepared.

[0128] Negative electrode active material: Natural graphite (D50: 15μm)

[0129] Adhesive: CMC

[0130] Dispersion medium: ion-exchanged water

[0131] A negative electrode paste is prepared by mixing 100 parts by mass of a negative electrode active material, 10 parts by mass of a binder, and 60 parts by mass of a dispersion medium. The negative electrode paste is then extruded from a mold to form a molded body. The molded body is then dried at 120°C for 3 hours to form the first electrode. The first electrode has the following structure.

[0132] Shape: Cylindrical (diameter: 20mm, height: 10mm)

[0133] Through-hole configuration: Regular (honeycomb pattern)

[0134] Through hole: regular hexagon (length of one side: 700μm, thickness of rib: 200μm)

[0135] (b) Formation of the diaphragm

[0136] (b1) Formation of the first layer

[0137] The following materials have been prepared.

[0138] First inorganic particle group: Boehmite (D150: 0.5 μm)

[0139] Adhesive #1: PVDF (Product name "KF Polymer", Grade "#8500", manufactured by Kreha Corporation)

[0140] Dispersion medium 1: NMP

[0141] A first paste was prepared by mixing 57 parts by mass of a first inorganic particle group, 5 parts by mass of a first binder, and 38 parts by mass of a first dispersion medium. 3–5 g of the first paste was placed on the first main surface of the first electrode. The first paste was drawn into the through-holes from the second main surface side using a vacuum pump. Thus, the first paste adhered to the inner wall of the through-holes. The first electrode (honeycomb electrode) with the first paste attached was dried at 120°C for 15 minutes. This formed the first layer. The average thickness of the first layer (first thickness) was measured using an optical microscope. The first thickness was 65 μm.

[0142] (b2) Formation of the second layer

[0143] The following materials have been prepared.

[0144] Group 2 of inorganic particles: aluminum oxide (D250: 0.1 μm)

[0145] Second adhesive: PVDF (product name "KF polymer", grade "#8500", manufactured by Kreha Corporation)

[0146] Second dispersion medium: NMP

[0147] A second paste was prepared by mixing 45 parts by mass of a second inorganic particle group, 7 parts by mass of a second binder, and 48 parts by mass of a second dispersion medium. 3–5 g of the second paste was placed on the first main surface of the first electrode. Using a vacuum pump, the second paste was drawn into the through-hole from the second main surface side. Thus, the second paste adhered to the surface of the first layer. The first electrode with the second paste attached was dried at 120°C for 15 minutes. This formed the second layer. The overall thickness of the diaphragm (the combined thickness of the first and second layers) was measured using an optical microscope. The overall thickness of the diaphragm was 87 μm. That is, the thickness of the second layer (the second thickness) was 22 μm.

[0148] Figure 8 Figure 1 shows the formation process of the diaphragm in this embodiment. Figure 8 The image shown is an X-ray CT image after the formation of the first layer 31. Multiple through holes 13 are formed on the first electrode 10 (cellular electrode). The inner walls of the through holes 13 are covered by the first layer 31.

[0149] Figure 9 Figure 2 shows the formation process of the diaphragm in this embodiment. Figure 9 The images show X-ray CT images after the formation of layer 1 31 and layer 2 32. After the formation of layer 1 31, spherical voids 3 are visible within it. After the formation of layer 2 32 (after the formation of membrane 30), the voids 3 become smaller. This is believed to be due to some of the second inorganic particle group 2 filling the voids 3.

[0150] (c) Configuration of the second electrode

[0151] Prepare the electrodeposition coating (product name "ELECOAT PI", manufactured by Simiz Co., Ltd.). The electrodeposition coating contains a dispersion phase and a dispersion medium. The dispersion phase contains resin particle clusters (polyimide). The dispersion medium contains water. Prepare Ni flat wire (thickness: 50 μm, width: 3 mm). The Ni flat wire is wound around the side of the first electrode. The Ni flat wire is connected to a power source. Immerse the first electrode in the electrodeposition coating. Using the first electrode as the cathode and the working electrode as the anode, apply a 30V voltage for 2 minutes. As a result, the first and second main surfaces are covered with an insulating film. After the insulating film is formed, remove excess electrodeposition coating by gently washing the first electrode with water. After washing, heat-treat the first electrode at 180°C for 1 hour.

[0152] The following materials have been prepared.

[0153] Positive electrode active material: Lithium cobalt oxide (D50: 10μm)

[0154] Conductive material: Acetylene black

[0155] Adhesive: PVDF (Product name "KF Polymer", grade "#1300", manufactured by Kreha Corporation)

[0156] Dispersion medium: NMP

[0157] A positive electrode paste was prepared by mixing 64 parts by mass of positive electrode active material, 4 parts by mass of conductive material, 2 parts by mass of binder, and 30 parts by mass of dispersion medium. A plastic syringe was prepared. A first electrode (honeycomb electrode) was fixed inside the syringe barrel. 3.5g of positive electrode paste was placed between the first electrode and a plunger inside the barrel. The positive electrode paste was pressed into the first electrode through the plunger. That is, the positive electrode paste was pressed into the through hole. The pressing of the plunger was stopped when the positive electrode paste was ejected from the opening on the opposite side of the pressing side. After the positive electrode paste was pressed in, the first electrode was dried at 120°C for 3 hours. Thus, a second electrode was formed inside the through hole. A battery element was formed through the above process.

[0158] In the battery element, the DC resistance between the first and second electrodes is measured using a tester. In Table 2 below, "OK" indicates a DC resistance of 1 MΩ or higher. "NG" indicates a DC resistance of less than 1 MΩ. Furthermore, in samples with a result of "OK", the DC resistance exceeds the measurement limit.

[0159] 0.5g of positive electrode paste was applied to both the first and second main surfaces. Using the positive electrode paste as an adhesive, aluminum (Al) foil was adhered to both the first and second main surfaces. The Al foil served as the current collector for the first electrode (positive electrode). The Al foil was 15μm thick. The battery element was dried at 120°C for 15 minutes. A Ni flat wire (thickness: 50μm, width: 3mm) was wound once around the side (outer peripheral surface) of the second electrode. The Ni flat wire served as the current collector for the second electrode (negative electrode). Stainless steel leads (terminals) were soldered onto both the Al foil and the Ni flat wire.

[0160] (d) Electrolyte infiltration

[0161] An aluminum laminated film pouch was prepared as the outer casing. The battery components were housed within the outer casing. 5g of electrolyte was injected into the outer casing. After injection, the outer casing was vacuum-sealed. The electrolyte had the following composition.

[0162] Electrolyte composition

[0163] Supported electrolyte: LiPF6 (concentration: 1 mol / kg)

[0164] Solvent: EC / EMC / DMC = 1 / 1 / 1 (volume ratio)

[0165] As described above, a test battery was manufactured. The test battery was designed to have a capacity of 400 mAh.

[0166] Initial charge and discharge

[0167] The following conditions are applied sequentially for charging, stopping, and discharging.

[0168] Charging: CCCV, CC current = 40mA, CV voltage = 4.2V, termination current = 10mA, stop: 10 minutes

[0169] Discharge: CCCV, CC current = 40mA, CV voltage = 3V, termination current = 10mA

[0170] Furthermore, "CC" indicates constant current mode, "CV" indicates constant voltage mode, and "CCCV" indicates constant current-constant voltage mode.

[0171] After the initial charge and discharge, adjust the voltage of the test battery according to the following conditions.

[0172] Charging: CCCV, CC current = 40mA, CV voltage = 3.85V, termination current = 10mA

[0173] After adjusting the voltage, the test battery was discharged for 5 seconds with a 200mA CC current. The voltage drop after 5 seconds was measured. The battery resistance was calculated based on the voltage drop and the discharge current. The battery resistance is shown in Table 2 below.

[0174] No. 2-9

[0175] Test cells with separators as shown in Table 2 were manufactured. The first and second thicknesses were adjusted by the solid content fractions of the first and second pastes.

[0176] In No. 6, titanium oxide was used instead of boehmite as the first inorganic particle group.

[0177] In No. 9, a second layer was not formed. That is, in No. 9, the separator consists of only the first layer. Due to insufficient insulation, the battery resistance of No. 9 was not measured.

[0178]

[0179] <Results>

[0180] In No. 1 to No. 8, sufficient insulation is achieved. In No. 1 to No. 8, the membrane has a first layer and a second layer, with the second average particle size being smaller than the first average particle size. In No. 1 to No. 8, it is believed that the porosity is reduced.

[0181] In No. 9, the insulation is insufficient. In No. 9, the diaphragm has a single-layer structure. In No. 9, it is believed that large voids remain.

[0182] Compared to No.7-8, batteries No.1-6 have lower resistance. Among No.1-6, the relationship "T2 / T1≤0.5" is satisfied.

[0183] This embodiment and these examples are illustrative in all respects. This embodiment and these examples are not restrictive. The scope of this disclosure includes all modifications within the same meaning and scope as described in the patent claim. For example, arbitrary structures can be extracted from this embodiment and these examples, and they can be arbitrarily combined from the outset.

Claims

1. A battery comprising a first electrode, a second electrode, and a separator, The first electrode includes a first main surface and a second main surface. The second principal surface is the opposite of the first principal surface. Multiple through holes are formed in the first electrode. The through hole extends from the first main surface through the first electrode to the second main surface. The diaphragm covers the inner wall of the through hole. The polarity of the second electrode is different from that of the first electrode. The second electrode is disposed within the through hole. The second electrode extends along the axial direction of the through hole. The diaphragm comprises a first layer having a first thickness and a second layer having a second thickness. The first layer is disposed between the inner wall and the second layer. The first layer contains a first group of inorganic particles with a first average particle size. The second layer contains a second group of inorganic particles with a second average particle size. The first average particle size is 0.8~1.5μm. The second average particle size is 0.1~0.2μm. The ratio of the second average particle size to the first average particle size is 0.125 to 0.

25. The first thickness is 30~70μm. The second thickness is 10~30μm. The ratio of the second average particle size to the first thickness is 1 / 350 to 1 / 300. The ratio of the second thickness to the first thickness is 0.3 to 0.

5.

2. The battery according to claim 1, The first electrode forms a honeycomb core material.

3. The battery according to claim 1 or 2, A void is formed in the first layer. The voids are filled with a portion of the second group of inorganic particles.

4. The battery according to claim 1 or 2, The first layer also contains a first adhesive. The second layer also contains a second adhesive.

5. The battery according to claim 1 or 2, The first inorganic particle group and the second inorganic particle group each independently contain at least one selected from alumina, alumina hydrate, aluminum hydroxide and titanium oxide.

6. The battery according to claim 1 or 2, The first electrode is columnar. The first main surface and the second main surface are located at opposite ends of the axial direction of the first electrode.

7. The battery according to claim 1 or 2, It also contains electrolyte.

8. A method for manufacturing a battery, comprising: Process (a): Prepare to form the first electrode with multiple through holes; Step (b): forming a diaphragm covering the inner wall of the through hole; and Step (c): After step (b), a second electrode is disposed within the through hole. The process (b) includes: Step (b1): A first layer is formed by applying a first paste to the inner wall of the through hole; and Step (b2): A second layer is formed by applying a second paste to the surface of the first layer. The polarity of the second electrode is different from that of the first electrode. The first paste contains a first group of inorganic particles having a first average particle size. The second paste contains a second group of inorganic particles having a second average particle size. The first average particle size is 0.8~1.5μm. The second average particle size is 0.1~0.2μm. The ratio of the second average particle size to the first average particle size is 0.125 to 0.

25. The first layer has a first thickness of 30~70μm. The second layer has a second thickness of 10~30μm. The ratio of the second average particle size to the first thickness is 1 / 350 to 1 / 300. The ratio of the second thickness to the first thickness is 0.3 to 0.

5.

9. The method for manufacturing a battery according to claim 8, The first electrode includes a first main surface and a second main surface. The second principal surface is the opposite of the first principal surface. The through hole extends from the first main surface through the first electrode to the second main surface. Step (b1) includes: drawing the first paste from the first main surface or the second main surface. Step (b2) includes: drawing the second paste from the first main surface or the second main surface.

10. The method for manufacturing a battery according to claim 8 or 9, The first paste further comprises a first binder and a first dispersion medium. The second paste also includes a second binder and a second dispersion medium.

11. The method of manufacturing a battery according to claim 8 or 9, further comprising: Step (d): Impregnate the diaphragm with electrolyte.

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