JP2022022761A - battery - Google Patents

Abstract

To provide a battery capable of improving cycle characteristics.SOLUTION: A battery includes a positive electrode, a negative electrode, and a separator. The negative electrode forms a honeycomb core. The honeycomb core includes a first surface, a second surface, a partition wall 23, and an outer peripheral wall. The second surface faces the first surface. The partition wall 23 is formed between the first surface and the second surface. In a cross section parallel to the first surface, the partition wall 23 extends in a lattice shape to partition a plurality of hollow cells 25. The separator spatially separates the positive electrode and the negative electrode. The separator includes a first layer 31 and a second layer. The first layer 31 covers at least a part of the partition wall 23. The second layer covers at least a part of the first surface and the second surface. In the cross section parallel to the first surface, the first layer 31 in the hollow cell has a minimum thickness and a maximum thickness. A ratio of the maximum thickness to the minimum thickness is less than or equal to 1.45.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to batteries.

Japanese Unexamined Patent Publication No. 2012-064538 (Patent Document 1) discloses a negative electrode in which the active material layer has a network structure.

Japanese Unexamined Patent Publication No. 2012-064538

A three-dimensional electrode structure is being studied. For example, a structure in which the positive electrode and the negative electrode are fitted to each other can be considered. More specifically, for example, a structure in which the negative electrode is a honeycomb core and the positive electrode is a pillar can be considered. A plurality of hollow cells (through holes) are formed in the negative electrode (honeycomb core). The positive electrode (pillar) is inserted through the hollow cell.

In order to separate the positive electrode and the negative electrode, a separator covering the inner wall of the hollow cell is formed. For example, a separator paste is prepared by mixing an insulating material (for example, inorganic particles or the like), a binder, and a dispersion medium. For example, the separator paste is applied to the inner wall of the hollow cell by sucking the separator paste from one end surface of the honeycomb core. The separator paste is dried to form a separator.

The method for forming the separator has advantages such as being able to be processed in a short time, and is therefore considered to be industrially promising. However, the thickness of the separator may become non-uniform and the cycle characteristics may deteriorate.

An object of the present disclosure is to improve cycle characteristics.

Hereinafter, the technical configuration and the action and effect of the present disclosure will be described. However, the mechanism of action of the present disclosure includes estimation. The correctness of the mechanism of action does not limit the scope of claims.

[1] The battery includes a positive electrode, a negative electrode, and a separator.
The negative electrode forms a honeycomb core. The honeycomb core includes a first surface, a second surface, a partition wall, and an outer peripheral wall. The second surface faces the first surface. The partition wall is formed between the first surface and the second surface. In the cross section parallel to the first surface, the partition wall extends in a grid pattern to partition a plurality of hollow cells. In a cross section parallel to the first surface, the outer wall surrounds the partition wall. Each of the plurality of hollow cells penetrates the honeycomb core in the direction from the first surface to the second surface.
The separator spatially separates the positive electrode and the negative electrode. The separator includes a first layer and a second layer. The first layer covers at least a part of the partition wall. The second layer covers at least a part of the first surface and the second surface.
The positive electrode includes a first region and a second region. The first region is filled in a hollow cell. The second region extends outwardly from the second layer of the separator in a cross section perpendicular to the first plane.
In a cross section parallel to the first surface, the first layer in the hollow cell has a minimum thickness and a maximum thickness. The ratio of the maximum thickness to the minimum thickness is 1.45 or less.

Since the separator paste is a fluid, leveling may occur during application. For example, when the cross-sectional shape of the hollow cell is polygonal, the separator tends to be rounded near the apex of the polygon due to the leveling of the separator paste. As a result, the separator is formed thick near the apex of the polygon, and the separator is formed thin at the sides of the polygon. That is, the thickness of the separator becomes non-uniform. Due to the non-uniform thickness of the separator, ion permeation may be non-uniform during charging and discharging. As a result, the reaction may be concentrated on a part of the negative electrode (or the positive electrode), and cycle deterioration may be promoted.

In a cross section parallel to the first surface, the first layer (separator) in the hollow cell has a minimum thickness (T _min. ) And a maximum thickness (T _max. ). The ratio of the maximum thickness (T _{max .} / T _min. ) To the minimum thickness (T _min .) Is an index of thickness uniformity. It is considered that the smaller the ratio (T _max. / T _min. ), The more uniform the thickness of the first layer (separator). In the present disclosure, the ratio (T _max. / T _min. ) Is 1.45 or less. When the ratio (T _max. / T _min. ) Is 1.45 or less, the reaction concentration is suppressed and the cycle characteristics are expected to be improved.

[2] For example, in a cross section parallel to the first surface, the cross-sectional shape of the hollow cell may be a polygon having six or more vertices or a circle.

[3] For example, the method for manufacturing a battery may include forming the first layer by sucking the separator paste into the honeycomb core from the first surface or the second surface. The separator paste contains a first insulating material, a binder and a dispersion medium.

FIG. 1 is a schematic view showing an example of a battery in this embodiment. FIG. 2 is a schematic view showing an example of the negative electrode in the present embodiment. FIG. 3 is a schematic cross-sectional view showing an example of a cross section parallel to the xy plane of FIG. FIG. 4 is a schematic cross-sectional view showing an example of a partition wall in the present embodiment. FIG. 5 is a schematic cross-sectional view showing an example of a cross section parallel to the yz plane of FIG. FIG. 6 is a schematic cross-sectional view showing a first example of the first layer. FIG. 7 is a schematic cross-sectional view showing a second example of the first layer. FIG. 8 is a schematic view showing an example of a current collector structure. FIG. 9 shows No. 1, No. 3 and No. It is explanatory drawing of the 1st layer in 4.

Hereinafter, embodiments of the present disclosure (hereinafter, also referred to as “the present embodiments”) will be described. However, the following description does not limit the scope of claims.

Geometric terms (eg, "parallel", "vertical", "regular hexagon", etc.) in this embodiment indicate that the state may be substantially the same. Geometric terms in this embodiment should not be understood in a strict sense. For example, "parallel" indicates a state of being substantially parallel. That is, "parallel" may deviate slightly from the "parallel" state in the strict sense. The "substantially parallel state" can naturally include, for example, design and manufacturing tolerances, errors, and the like.

In the present embodiment, for example, the description such as "0.1 part by mass to 10 part by mass" indicates a range including the boundary value unless otherwise specified. For example, "0.1 parts by mass to 10 parts by mass" indicates a range of "0.1 parts by mass or more and 10 parts by mass or less".

In the present embodiment, the description "consisting of substantially ..." indicates that an additional component may be contained in addition to the essential component as long as the object of the present disclosure is not impaired. For example, components normally assumed in the field of the art (eg, unavoidable impurities, etc.) may naturally be included.

In the present embodiment, when the compound is represented by a stoichiometric composition formula such as "Li _2S ", the stoichiometric composition formula is only a representative example. For example, when lithium sulfide is expressed as "Li 2S", lithium sulfide is not limited to the composition ratio of "Li: S = ₂ : 1" and may contain Li and S in any composition ratio.

In this embodiment, a "lithium ion battery" will be described as an example of the battery. However, the battery can be any battery system. The battery of the present embodiment may be, for example, a "sodium ion battery", a "nickel hydrogen battery" or the like.

The battery of this embodiment can be applied to any application. The battery of the present embodiment may be used in, for example, a mobile terminal, a portable device, a stationary power storage device, an electric vehicle, a hybrid vehicle, or the like.

<Battery>
FIG. 1 is a schematic view showing an example of a battery in this embodiment.
The battery 100 includes a battery element 50. The battery element 50 has a three-dimensional electrode structure. The battery element 50 includes a positive electrode 10, a negative electrode 20, and a separator 30. That is, the battery 100 includes a positive electrode 10, a negative electrode 20, and a separator 30.

The battery 100 may include, for example, a battery case (not shown). The battery case may contain the battery element 50. The battery case may be sealed. The battery case may be, for example, a bag made of an aluminum (Al) laminated film or the like. The battery case may be, for example, a metal container or the like. The battery case can have any outer shape. The outer shape of the battery case may be, for example, a square shape, a cylindrical shape, a coin shape, a flat shape, a thin shape (sheet type), or the like.

《Negative electrode》
FIG. 2 is a schematic view showing an example of the negative electrode in the present embodiment.
The negative electrode 20 is an electrode having a lower potential than the positive electrode 10. The negative electrode 20 contains a negative electrode active material. The negative electrode 20 may be substantially made of, for example, a negative electrode active material. The negative electrode 20 forms a honeycomb core. The honeycomb core may also be referred to as, for example, a "honeycomb structure", a "honeycomb molded body" or the like. The honeycomb core of FIG. 2 has a columnar outer shape. However, the honeycomb core may have any outer shape. The outer shape of the honeycomb core may be, for example, a disk shape, a square plate shape, a prismatic shape, or the like.

The honeycomb core of the present embodiment may be, for example, a molded body of a negative electrode active material. The honeycomb core may be, for example, a molded body of a negative electrode mixture. The negative electrode mixture may further contain, for example, a conductive material, a binder, or the like, in addition to the negative electrode active material.

The negative electrode active material may be, for example, particles. The negative electrode active material may have, for example, a median diameter of 1 μm to 30 μm. The "median diameter" indicates a particle size in which the cumulative particle volume from the small particle size side is 50% of the total particle volume in the volume-based particle size distribution. The median diameter can be measured by a laser diffraction type particle size distribution measuring device.

The negative electrode active material may contain any component. The negative electrode active material may contain, for example, at least one selected from the group consisting of graphite, hard carbon, soft carbon, silicon, silicon oxide, tin, tin oxide, and lithium titanate. The conductive material may contain any component. The conductive material may contain, for example, at least one selected from the group consisting of carbon black (for example, acetylene black and the like), carbon fibers, metal particles, and metal fibers. The blending amount of the conductive material may be, for example, 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. The binder may contain any component. The binder may include, for example, at least one selected from the group consisting of carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), and polyacrylic acid (PAA). The blending amount of the binder may be, for example, 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

The negative electrode 20 (honeycomb core) includes a first surface 21, a second surface 22, a partition wall 23, and an outer peripheral wall 24. The second surface 22 faces the first surface 21. The partition wall 23 and the outer peripheral wall 24 are formed between the first surface 21 and the second surface 22. The partition wall 23 and the outer peripheral wall 24 connect the first surface 21 and the second surface 22.

Each of the first surface 21 and the second surface 22 may be, for example, a flat surface. Each of the first surface 21 and the second surface 22 does not have to be a flat surface, for example. Each of the first surface 21 and the second surface 22 may be, for example, a curved surface. The first surface 21 may be parallel to the second surface 22. The first surface 21 does not have to be parallel to the second surface 22.

In the present embodiment, the height (h) of the honeycomb core indicates the distance between the first surface 21 and the second surface 22. If the first surface 21 and the second surface 22 are not parallel, the shortest distance between the first surface 21 and the second surface 22 is considered to be the height (h). The honeycomb core may have a height (h) of, for example, 3 mm or more. When the honeycomb core has a height (h) of 3 mm or more, the strength of the honeycomb core can be significantly improved. Further, it is expected that the battery capacity will be increased by increasing the ratio of the electrode active material in the battery element 50. The height (h) of the honeycomb core may have any upper limit. The honeycomb core may have a height (h) of, for example, 1000 mm or less. The honeycomb core may have a height (h) of, for example, 500 mm or less. The honeycomb core may have a height (h) of 100 mm or less, for example. The honeycomb core may have a height (h) of, for example, 10 mm or less.

In the xy plane of FIG. 2, the honeycomb core has a diameter (d). The diameter (d) indicates the maximum diameter of the honeycomb core in the xy plane. The honeycomb core may have any diameter (d). The honeycomb core may have a diameter (d) of, for example, 1 mm to 1000 mm. The honeycomb core may have a diameter (d) of, for example, 10 mm to 100 mm.

In the present embodiment, the aspect ratio (h / d) of the honeycomb core indicates the ratio of the height (h) to the diameter (d). The honeycomb core may have, for example, an aspect ratio (h / d) of 0.1 to 10. The honeycomb core may have, for example, an aspect ratio (h / d) of 0.1 to 2. The honeycomb core may have, for example, an aspect ratio (h / d) of 0.1 to 1. The honeycomb core may have, for example, an aspect ratio (h / d) of 0.1 to 0.5. The honeycomb core may have, for example, an aspect ratio (h / d) of 0.15 to 0.5.

FIG. 3 is a schematic cross-sectional view showing an example of a cross section parallel to the xy plane of FIG. In the present embodiment, the "cross section parallel to the xy plane" indicates a "cross section parallel to the first surface 21 (or the second surface 22)".

In FIG. 3, the partition wall 23 extends in a grid pattern. The partition wall 23 partitions a plurality of hollow cells 25. The partition wall 23 may be referred to as, for example, a "rib" or the like. The outer peripheral wall 24 surrounds the periphery of the partition wall 23.

The hollow cell 25 is, so to speak, a “through hole”. Each of the plurality of hollow cells 25 penetrates the honeycomb core (negative electrode 20) in the direction from the first surface 21 to the second surface 22 (the z-axis direction of FIGS. 1 to 3). In the cross section parallel to the xy plane, a plurality of hollow cells 25 are integrated. The plurality of hollow cells 25 may be arranged at substantially equal intervals. The spacing between the hollow cells 25 may be random.

For example, 4 to 10000 hollow cells 25 may be formed in a cross section parallel to the xy plane. For example, 10 to 5000 hollow cells 25 may be formed in a cross section parallel to the xy plane. For example, 100 to 5000 hollow cells 25 may be formed in a cross section parallel to the xy plane. For example, 500 to 5000 hollow cells 25 may be formed in a cross section parallel to the xy plane. For example, 1000 to 3000 hollow cells 25 may be formed in a cross section parallel to the xy plane.

In a cross section parallel to the xy plane, the plurality of hollow cells 25 may have a number density of, for example, 1 piece / mm ² to 10 pieces / mm ² . The plurality of hollow cells 25 may have a number density of, for example, 2 cells / mm ² to 6 cells / mm ² .

The total cross-sectional area of the plurality of hollow cells 25 may have, for example, a surface integral of 50% to 99% with respect to the cross-sectional area of the honeycomb core. The total cross-sectional area of the plurality of hollow cells 25 may have, for example, a surface integral of 70% to 90% with respect to the cross-sectional area of the honeycomb core. In this embodiment, the cross-sectional area of the honeycomb core is substantially the same as the area of the first surface 21 or the second surface 22.

In a cross section parallel to the xy plane, each of the plurality of hollow cells 25 may have an arbitrary contour. Each of the plurality of hollow cells 25 may have contours such as polygons (hexagons, octagons, etc.), circles, and the like.

FIG. 4 is a schematic cross-sectional view showing an example of a partition wall in the present embodiment.
Each of the plurality of hollow cells 25 may have, for example, a hexagonal contour. Since the contour of the hollow cell 25 is hexagonal, for example, the integration rate of the hollow cell 25 in the honeycomb core can be improved. By improving the integration rate, for example, the facing area between the positive electrode 10 and the negative electrode 20 can be increased. As a result, for example, improvement in output is expected.

The contours of the plurality of hollow cells 25 may all be the same. The contours of the plurality of hollow cells 25 may be different from each other.

The partition wall 23 may have an arbitrary thickness (t). The thickness (t) of the partition wall 23 indicates the shortest distance between adjacent hollow cells 25 in a cross section parallel to the xy plane. The partition wall 23 may have a thickness (t) of, for example, 20 μm to 350 μm. When the thickness (t) of the partition wall 23 is 20 μm or more, for example, the strength of the honeycomb core is expected to be improved. When the thickness (t) of the partition wall 23 is 350 μm or less, for example, reduction of battery resistance is expected. The partition wall 23 may have a thickness (t) of, for example, 140 μm or more.

In the cross section parallel to the xy plane, each of the plurality of hollow cells 25 may have, for example, a cross-sectional area of 900 μm ² or more. When the cross-sectional area of the hollow cell 25 is 900 μm ² or more, for example, an increase in battery capacity is expected. Each of the plurality of hollow cells 25 may have, for example, a cross-sectional area of 67600 μm ² or more. The upper limit of the cross-sectional area is arbitrary. Each of the plurality of hollow cells 25 may have, for example, a cross-sectional area of 900 μm ² to 490000 μm ² . Each of the plurality of hollow cells 25 may have, for example, a cross-sectional area of 900 μm ² to 250,000 μm ² . By specifying the upper limit of the cross-sectional area, for example, reduction of battery resistance is expected.

《Separator》
FIG. 5 is a schematic cross-sectional view showing an example of a cross section parallel to the yz plane of FIG. In the present embodiment, the "cross section parallel to the yz plane" indicates a "cross section perpendicular to the first surface 21 (or the second surface 22)".

The separator 30 spatially separates the positive electrode 10 and the negative electrode 20. The "spatial separated state" indicates a state in which the positive electrode 10 and the negative electrode 20 are not in direct contact with each other. The separator 30 contains, for example, an insulating material. The separator 30 substantially blocks electron conduction between the positive electrode 10 and the negative electrode 20.

The separator 30 may form, for example, a conduction path for carrier ions. For example, the carrier ion in a lithium ion battery is lithium ion. The separator 30 may contain, for example, a solid electrolyte. When the separator 30 contains a solid electrolyte, the positive electrode 10 and the negative electrode 20 may also contain the solid electrolyte. The solid electrolyte may contain, for example, an oxide solid electrolyte. The solid electrolyte may contain, for example, a sulfide solid electrolyte. The sulfide solid electrolyte may contain, for example, lithium phosphorus sulfide ₍ Li 2SP _{2S 5 )} and the like.

The separator 30 may contain, for example, a gel polymer electrolyte. The gel polymer electrolyte may contain, for example, a host polymer and an electrolytic solution (described later). The host polymer is, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylonitrile (PAN), and polyethylene oxide (PEO). It may contain seeds.

The separator 30 includes a first layer 31 and a second layer 32. The first layer 31 covers at least a part of the partition wall 23. The first layer 31 may substantially cover the entire surface of the partition wall 23. However, as long as the positive electrode 10 and the negative electrode 20 are spatially separated, the first layer 31 may cover a part of the partition wall 23.

The second layer 32 may be connected to the first layer 31. The second layer 32 and the first layer 31 may be continuous. The second layer 32 may not be connected to the first layer 31. The second layer 32 may be discontinuous with the first layer 31. For example, there may be a gap between the second layer 32 and the first layer 31.

The second layer 32 covers at least a part of the first surface 21 and the second surface 22. The second layer 32 may cover both the first surface 21 and the second surface 22, for example. The second layer 32 may cover only the first surface 21, for example. The second layer 32 may cover substantially the entire surface of the first surface 21, for example. The second layer 32 may cover a part of the first surface 21, for example. The second layer 32 may cover only the second surface 22, for example. The second layer 32 may cover substantially the entire surface of the second surface 22, for example. The second layer 32 may cover a part of the second surface 22, for example.

(1st layer)
The first layer 31 separates the positive electrode 10 and the negative electrode 20 inside the hollow cell 25. The first layer 31 contains a first insulating material. The first layer 31 may be substantially made of the first insulating material. The first layer 31 may further contain, for example, a binder or the like in addition to the first insulating material. The first insulating material may be, for example, particles or the like. The first insulating material may have, for example, a median diameter of 10 nm to 1 μm. The first insulating material may contain any component. The first insulating material may contain, for example, at least one selected from the group consisting of alumina, boehmite, titania, magnesia, and zirconia. The binder may contain any component. The binder may contain, for example, at least one selected from the group consisting of PVDF, PVDF-HFP, and polytetrafluoroethylene (PTFE). The blending amount of the binder may be, for example, 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the first insulating material.

The first layer 31 can have any thickness. The thickness of the first layer 31 indicates the dimension in the y-axis direction of FIG. The first layer 31 may have a thickness of, for example, 1 μm to 100 μm. The first layer 31 may have a thickness of, for example, 10 μm to 30 μm.

FIG. 6 is a schematic cross-sectional view showing a first example of the first layer.
The first layer 31 covers the partition wall 23 in the hollow cell 25. In the cross section parallel to the xy plane, the surface integral of the first layer 31 with respect to the cross section of the hollow cell 25 may be, for example, 1% to 50%. The surface integral of the first layer 31 may be, for example, 1% to 20%. The surface integral of the first layer 31 may be, for example, 1% to 10%.

(Ratio of maximum thickness to minimum thickness)
In a cross section parallel to the xy plane, the first layer 31 in the hollow cell 25 has a minimum thickness (T _min. ) And a maximum thickness (T _max. ). When the cross-sectional shape of the hollow cell 25 is polygonal, the maximum thickness (T _max. ) Typically appears near the apex of the polygon. The minimum thickness (T _min. ) Typically appears on the sides of the polygon. In the present embodiment, the ratio of the maximum thickness to the minimum thickness (T _max. / T _min. ) Is 1.45 or less. When the ratio (T _max. / T _min. ) Is 1.45 or less, the reaction concentration is suppressed and the cycle characteristics are expected to be improved. The ratio (T _max. / T _min. ) May be, for example, 1.39 or less. The ratio (T _max. / T _min. ) May be, for example, 1.15 or less. The ratio (T _max. / T _min. ) May be, for example, 1 or more. The ratio (T _{max./T min.} ) May be, for example, 1.15 to 1.45.

The ratio (T _max. / T _min. ) In this embodiment is an arithmetic mean of the values measured in the plurality of hollow cells 25. For example, 30 hollow cells 25 are arbitrarily extracted from the honeycomb core. The ratio (T _max. / T _min. ) Is calculated by measuring the minimum thickness (T _min. ) And the maximum thickness (T _max. ) In each of the 30 hollow cells 25. Arithmetic mean of 30 ratios (T _{max./T min.} ) Is adopted. The ratio (T _{max./T min.} ) Is valid up to the second decimal place. Rounded to the third decimal place. When the total number of hollow cells 25 formed in the honeycomb core is less than 30, the ratio (T _max. / T _min. ) Is calculated for each of the hollow cells 25, and the arithmetic mean is further calculated. ..

The ratio (T _{max./T min.} ) Can be adjusted by any method. For example, the ratio (T _max. / T _min. ) May be adjusted by changing the cross-sectional shape (contour) of the hollow cell 25.

FIG. 7 is a schematic cross-sectional view showing a second example of the first layer.
The separator paste tends to be rounded near the apex of the polygon due to the leveling effect. As a result, the separator (first layer 31) tends to be thicker near the apex of the polygon. When the cross-sectional shape of the hollow cell 25 is hexagonal (FIG. 6) as compared with the case where the cross-sectional shape of the hollow cell 25 is quadrangular (FIG. 6), the first layer 31 becomes thinner and thicker near the apex. The uniformity of the quadrangle is high. Therefore, it is expected that the ratio (T _max. / T _min. ) Will be small because the cross-sectional shape of the hollow cell 25 is a polygon having six or more vertices. It is expected that the ratio (T _max. / T _min. ) Becomes smaller as the number of vertices increases. The polygon may be, for example, a regular polygon. As the number of vertices of a regular polygon increases, the regular polygon is considered to approximate a circle. Therefore, it is considered that the cross-sectional shape of the hollow cell 25 may be circular.

As long as the ratio (T _max. / T _min. ) Is 1.45 or less, the polygon may have less than 6 vertices. That is, the polygon may be a pentagon, a quadrangle, or a triangle as long as the ratio (T _max. / T _min. ) Is 1.45 or less.

For example, the ratio (T _max. / T _min. ) may be adjusted by adjusting the viscosity of the separator paste. The lower the viscosity, the smaller the ratio (T _max. / T _min. ) Tends to be. The viscosity of the separator paste can be adjusted, for example, by the solid content ratio, the binder blending amount, the binder type and the like. However, if the viscosity becomes too low, the separator may be defective.

(2nd layer)
The second layer 32 separates the positive electrode 10 and the negative electrode 20 outside the hollow cell 25. The second layer 32 contains a second insulating material. The second insulating material may be, for example, the same as the first insulating material. The second insulating material may be different from, for example, the first insulating material. Since the second insulating material is different from the first insulating material, for example, the degree of freedom in the method of forming the second layer 32 and the first layer 31 can be improved. For example, the second layer 32 may be formed by a method different from the method for forming the first layer 31.

The second layer 32 may be substantially made of the second insulating material. The second layer 32 may further contain other components in addition to the second insulating material. The second insulating material may be, for example, particles or the like. The second insulating material may have, for example, a median diameter of 10 nm to 1 μm. The second insulating material may contain any component. The second insulating material may contain, for example, at least one selected from the group consisting of polyimide (PI), polyamideimide (PAI), PTFE, polyethylene (PE), polypropylene (PP), and PAA.

The second layer 32 can have any thickness. The thickness of the second layer 32 indicates the dimension in the z-axis direction of FIG. The thickness of the second layer 32 may be substantially the same as the thickness of the first layer 31, for example. The thickness of the second layer 32 may be different from the thickness of the first layer 31, for example. For example, the thickness of the second layer 32 may be larger than the thickness of the first layer 31. The second layer 32 may have a thickness of, for example, 1 μm to 100 μm. The second layer 32 may have a thickness of, for example, 10 μm to 30 μm.

The permeability of the carrier ions in the second layer 32 may be substantially the same as the permeability of the carrier ions in the first layer 31. The permeability of carrier ions in the second layer 32 may be different from the permeability of carrier ions in the first layer 31. For example, the permeability of carrier ions in the second layer 32 may be lower than the permeability of carrier ions in the first layer 31. This is expected to alleviate structural changes associated with, for example, charge / discharge (expansion / contraction). The permeability of carrier ions can be adjusted, for example, by the porosity of each layer, the thickness of each layer, the constituent material (material, particle size, etc.) of each layer.

《Positive electrode》
The positive electrode 10 is an electrode having a higher potential than the negative electrode 20. As shown in FIG. 5, the positive electrode 10 includes a first region 11 and a second region 12. The first region 11 is filled in the hollow cell 25. The first region 11 may substantially fill the hollow cell 25. The first region 11 may be porous. For example, a through hole or the like may be formed in the first region 11.

For example, the first region 11 may have a similar shape to the contour of the hollow cell 25. For example, the contour of the hollow cell 25 may be hexagonal, and the first region 11 may also be hexagonal. The first region 11 may have a shape dissimilar to the contour of the hollow cell 25. For example, the contour of the hollow cell 25 may be polygonal and the first region 11 may be circular.

In the cross section parallel to the xy plane, the surface integral of the first region 11 with respect to the cross section of the hollow cell 25 may be, for example, 50% to 99%. The surface integral of the first region 11 may be, for example, 80% to 99%. The surface integral of the first region 11 may be, for example, 90% to 99%.

As shown in FIG. 5, the second region 12 extends so as to project outward from the second layer 32 of the separator 30 in a cross section parallel to the yz plane. That is, the second region 12 includes a portion protruding in the z-axis direction from the second layer 32. The second region 12 may cover the surface of the second layer 32. For example, the positive electrode current collector 41 may be connected to the second region 12. The second region 12 may also be porous.

The first region 11 may have the same composition as the second region 12. The first region 11 may have a composition different from that of the second region 12. Each of the first region 11 and the second region 12 contains a positive electrode active material. Each of the first region 11 and the second region 12 may be substantially composed of, for example, a positive electrode active material. Each of the first region 11 and the second region 12 may contain, for example, a positive electrode mixture. In addition to the positive electrode active material, the positive electrode mixture may further contain, for example, a conductive material, a binder, and the like.

The positive electrode active material may be, for example, particles. The positive electrode active material may have, for example, a median diameter of 1 μm to 30 μm. The positive electrode active material may contain any component. The positive electrode active material contains, for example, at least one selected from the group consisting of lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, and lithium iron phosphate. May be good. The conductive material may contain any component. The conductive material may contain, for example, at least one selected from the group consisting of carbon black, carbon fibers, metal particles, and metal fibers. The blending amount of the conductive material may be, for example, 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder may contain any component. The binder may include, for example, at least one selected from the group consisting of PVDF, PVDF-HFP, PTFE, CMC and PAA. The blending amount of the binder may be, for example, 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material.

《Electrolytic solution》
The battery 100 may further contain an electrolytic solution. The electrolytic solution contains a supporting electrolyte and a solvent. The supporting electrolyte is dissolved in the solvent. The supporting electrolyte may contain any component. The supporting electrolyte may include, for example, at least one selected from the group consisting of LiPF ₆ , LiBF ₄ , and Li ₍ FSO ₂ ) 2N. The concentration of the supporting electrolyte may be, for example, 0.5 mL / kg to 2 mL / kg.

The solvent is aprotic. The solvent may contain any component. The solvent is, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC) and diethyl carbonate (DEC). It may contain seeds.

The electrolytic solution may further contain various additives in addition to the supporting electrolyte and the solvent. Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesalton (PS), cyclohexylbenzene (CHB), tert-amylbenzene (TAB) and lithium bisoxalate boronate. It may contain at least one selected from the group consisting of (LiBOB).

《Current collector structure》
As shown in FIG. 5, the battery 100 may further include, for example, a positive electrode current collector 41 and a negative electrode current collector 42. The positive electrode current collector 41 electrically connects the positive electrode 10 and an external terminal (not shown). The positive electrode current collector 41 itself may also serve as an external terminal. The positive electrode current collector member 41 may include, for example, a metal mesh, a metal foil, a metal wire, or the like. The positive electrode current collector 41 may contain, for example, Al, nickel (Ni), stainless steel (SUS), or the like.

The negative electrode current collector 42 electrically connects the negative electrode 20 and the external terminal. The negative electrode current collector 42 itself may also serve as an external terminal. The negative electrode current collector 42 may include, for example, a metal mesh, a metal foil, a metal wire, or the like. The negative electrode current collector 42 may contain, for example, Ni, Cu, or the like.

FIG. 8 is a schematic view showing an example of a current collector structure.
The positive electrode current collecting member 41 may be arranged on both sides of the honeycomb core in the height direction (z-axis direction) of the honeycomb core. As shown in FIG. 5, the positive electrode current collecting member 41 is connected to the second region 12 of the positive electrode 10. For example, the positive electrode current collector 41 may be adhered to the second region 12. For example, the positive electrode current collector member 41 may be crimped to the second region 12. For example, the positive electrode current collector 41 may be welded to the second region 12.

The negative electrode current collector 42 may be connected to the outer peripheral wall 24 of the honeycomb core (negative electrode 20). The negative electrode current collector 42 may extend over the entire circumference of the outer peripheral wall 24. For example, the negative electrode current collector 42 may be adhered to the honeycomb core. For example, the negative electrode current collector 42 may be crimped to the honeycomb core. For example, the negative electrode current collector 42 may be welded to the honeycomb core. For example, the negative electrode current collector 42 may be welded to the honeycomb core.

In the current collecting structure of FIG. 8, the current collecting area of the positive electrode 10 can be large. This is expected to reduce the resistance component derived from the positive electrode.

Hereinafter, examples of the present disclosure (hereinafter, also referred to as “the present examples”) will be described. However, the following description does not limit the scope of claims.

<Manufacturing of test batteries>
From the following procedure, No. 1 to No. The test battery according to No. 7 was manufactured.

<< No. 1 >>
(1. Molding of honeycomb core)
The following materials were prepared.
Negative electrode active material: Graphite (median diameter 15 μm)
Binder: CMC
Dispersion medium: Ion-exchanged water

A negative electrode paste was prepared by mixing 100 parts by mass of the negative electrode active material, 10 parts by mass of the binder, and 60 parts by mass of the dispersion medium.

A mold for forming the honeycomb core was prepared. The negative electrode paste was compressed and extruded from the mold to form a wet molded body. The honeycomb core (negative electrode 20) was formed by drying the wet molded product. The drying temperature was 120 ° C. The drying time was 3 hours.

The dimensions of the honeycomb core are as follows. The hollow cells 25 were arranged at substantially equal intervals.
Height: 10 mm
Diameter: 20 mm
Thickness of partition wall 23: 250 μm
Cross-sectional shape of hollow cell 25: Regular hexagon (length of one side 350 μm)

(2. Formation of separator 1st layer)
The following materials were prepared.
First insulating material: boehmite (median diameter 100 nm)
Binder: PVDF (product name "KF polymer", grade "# 8500", manufactured by Kureha Corporation)
Dispersion medium: NMP

A separator paste was prepared by mixing 45 parts by mass of the first insulating material, 4 parts by mass of the binder, and 40 parts by mass of the dispersion medium. About 4 g to 5 g of a separator paste was placed on the first surface 21 of the honeycomb core. The separator paste was sucked into the honeycomb core from the second surface 22 side by a vacuum pump. As a result, the separator paste was applied to the partition wall 23. After suction, the separator paste was dried. As a result, the first layer 31 was formed. The drying temperature was 120 ° C. The drying time was 15 minutes. The target value for the thickness of the first layer 31 was 20 μm.

(3. Evaluation of uniformity of the first layer)
The first surface 21 and the second surface 22 were polished by sandpaper to expose the cross section of the partition wall 23. The cross section was observed with an optical microscope. Thirty hollow cells 25 were randomly sampled. In the 30 hollow cells 25, the minimum thickness (T _min. ) Of the first layer 31 and the maximum thickness (T _max. ) Of the first layer 31 were measured, respectively. Further, the ratio (T _max. / T _min. ) Was calculated. Those whose appearance of the first layer 31 was clearly irregular at the time of observation were excluded from the evaluation.

(4. Formation of the second layer of the separator)
Electrodeposition paint (product name "Elecoat PI", manufactured by Shimizu Co., Ltd.) was prepared. The electrodeposition paint contained a dispersoid and a dispersion medium. The dispersoid contained resin particles (polyimide). The dispersion medium contained water. The resin particles correspond to the second insulating material. A Ni flat wire (thickness 50 μm, width 3 mm) was prepared as the negative electrode current collector 42. The negative electrode current collector 42 was wound around the outer peripheral wall 24 of the honeycomb core over one circumference. The negative electrode current collector 42 was welded to the outer peripheral wall 24 by resistance welding. The negative electrode current collector 42 was connected to the power supply. The honeycomb core was immersed in the electrodeposition paint. A voltage of 30 V was applied so that the honeycomb core became the cathode. Electroplation was performed for 2 minutes. As a result, the second layer 32 was formed by depositing the second insulating material on the first surface 21 and the second surface 22. After electrodeposition, the honeycomb core was lightly washed with water to substantially remove excess electrodeposition paint. After cleaning, the honeycomb core was heat treated. The heat treatment temperature was 180 ° C. The heat treatment time was 1 hour.

(5. Formation of positive electrode)
The following materials were prepared.
Positive electrode active material: Lithium cobalt oxide (median diameter 10 μm)
Conductive material: Acetylene black binder: PVDF (Product name "KF polymer", Grade "# 1300", manufactured by Kureha Corporation)
Dispersion medium: NMP

A positive electrode paste was prepared by mixing 64 parts by mass of the positive electrode active material, 4 parts by mass of the conductive material, 2 parts by mass of the binder, and 30 parts by mass of the dispersion medium. A plastic syringe was prepared. A honeycomb core was fixed in the barrel of the syringe. In the barrel, about 3.5 g of positive electrode paste was placed between the honeycomb core and the plunger. The plunger pushed the positive electrode paste into the honeycomb core. That is, the positive electrode paste was filled in the hollow cell 25. When the positive electrode paste was discharged from the opening on the opposite side to the pushing side, the pushing of the plunger was stopped. After filling the positive electrode paste, the honeycomb core was removed from the barrel. The honeycomb core has been dried. The drying temperature was 120 ° C. The drying time was 30 minutes. From the above, the positive electrode 10 was formed.

(6. Battery assembly)
An Al foil (thickness 15 μm) was prepared as the positive electrode current collector 41. By punching, the positive electrode current collector 41 was processed into a circular shape (diameter 25 mm). Positive electrode current collectors 41 were arranged on both sides of the honeycomb core in the height direction of the honeycomb core. The positive electrode current collecting member 41 was adhered to the second region 12 (positive electrode 10) with about 0.5 g of the positive electrode paste.

As described above, in this embodiment, the negative electrode current collecting member 42 is connected to the outer peripheral wall 24 (negative electrode 20) at the time of forming the second layer 32 (during electrodeposition).

A SUS tab was prepared as an external terminal. A SUS tab was welded to each of the positive electrode current collector 41 and the negative electrode current collector 42.

The electrolyte was prepared. The composition of the electrolytic solution was as follows.
Supporting electrolyte: LiPF ₆ (concentration 1 mol / kg)
Solvent: EC / EMC / DMC = 1/1/1 (volume ratio)

As a battery case, a bag made of Al laminated film was prepared. The battery element 50 was housed in a battery case. 5 g of electrolyte was poured into the battery case. After injecting the electrolyte, the battery case was sealed with a vacuum sealer. From the above, No. The test battery according to No. 1 was manufactured. The design capacity of the test battery in this example was 400 mAh.

<< No. 2 >>
In the above "2. Formation of the first layer of the separator", a separator paste is prepared by mixing 45 parts by mass of the first insulating material, 10 parts by mass of the binder, and 90 parts by mass of the dispersion medium. Except for that, No. Similar to No. 1, the test battery was manufactured.

<< No. 3 >>
In the above "1. Honeycomb core molding", No. 1 except that a honeycomb core having the following dimensions is formed by changing the mold for honeycomb core molding. Similar to No. 1, the test battery was manufactured.

Height: 10 mm
Diameter: 20 mm
Thickness of partition wall 23: 250 μm (thickness of the thinnest part)
Cross-sectional shape of hollow cell 25: circular (inner diameter 500 μm)

<< No. 4 >>
In the above "1. Honeycomb core molding", No. 1 except that a honeycomb core having the following dimensions is formed by changing the mold for honeycomb core molding. Similar to No. 1, the test battery was manufactured.

Height: 10 mm
Diameter: 20 mm
Thickness of partition wall 23: 140 μm
Cross-sectional shape of hollow cell 25: square (length of one side 240 μm)

FIG. 9 shows No. 1, No. 3 and No. It is explanatory drawing of the 1st layer in 4. No. 1 and No. For 4, the actual light microscope image is also shown.

<< No. 5 >>
In the above "2. Formation of the first layer of the separator", a separator paste is prepared by mixing 45 parts by mass of the first insulating material, 4 parts by mass of the binder, and 55 parts by mass of the dispersion medium. Except for that, No. Similar to No. 4, the test battery was manufactured.

<< No. 6 >>
In the above "2. Formation of the first layer of the separator", a separator paste is prepared by mixing 45 parts by mass of the first insulating material, 4 parts by mass of the binder, and 60 parts by mass of the dispersion medium. Except for that, No. Similar to No. 4, the test battery was manufactured.

<< No. 7 >>
No. except that no separator is formed. Similar to No. 1, the test battery was manufactured.

<Cycle test>
A cycle test was conducted under the following conditions. The capacity retention rate (percentage) was calculated by dividing the discharge capacity of the 100th cycle by the discharge capacity of the first cycle. The capacity retention rate is shown in Table 1 below.

Charging: CCCV method, CC current 200mA, CV voltage 4.2V, termination current 10mV
Discharge: CCCV method, CC current 200mA, CV voltage 3V, termination current 10mA
Number of cycles: 100

The "CCCV method" indicates a constant current-constant voltage method. "CC current" indicates the current at the time of constant current charging. "CV voltage" indicates a voltage at the time of constant voltage charging. During constant voltage charge or constant voltage discharge, the current is attenuated. Charging or discharging is stopped when the current decays to the "termination current".

<Result>
As shown in Table 1 above, when the ratio (T _max. / T _min. ) Is 1.45 or less, the capacity retention rate in the cycle test tends to improve. That is, there is a tendency for the cycle characteristics to improve.

When the cross-sectional shape of the hollow cell is a regular hexagon or a circle, the ratio (T _max. / T _min. ) Tends to be small.

No. From the results of 4 and 5, there is a tendency that the ratio (T _max. / T _min. ) Decreases as the solid content ratio of the separator paste decreases (that is, the viscosity decreases). However, when the solid content ratio becomes excessively low, it becomes difficult for the separator paste to adhere to the surface of the honeycomb core, and it becomes difficult to form the separator (No. 6). In this embodiment, it is considered more effective to adjust the cross-sectional shape of the hollow cell than to adjust the solid content of the separator paste.

The present embodiment and the present embodiment are exemplary in all respects. The present embodiment and the present embodiment are not limiting. For example, it is planned from the beginning that arbitrary configurations are extracted from the present embodiment and the present embodiment and they are arbitrarily combined.

The technical scope defined based on the description of the scope of claims includes all changes in the sense equivalent to the description of the scope of claims. Furthermore, the technical scope defined based on the description of the scope of claims also includes all changes within the scope equivalent to the description of the scope of claims.

10 Positive electrode, 11 1st region, 12 2nd region, 20 Negative electrode, 21 1st surface, 22 2nd surface, 23 partition wall, 24 outer wall, 25 hollow cell, 30 separator, 31 1st layer, 32 2nd layer, 41 positive electrode current collector member, 42 negative electrode current collector member, 50 battery element, 100 battery.

Claims (1)

With the positive electrode
With the negative electrode
Separator and
Including
The negative electrode forms a honeycomb core and has a honeycomb core.
The honeycomb core includes a first surface, a second surface, a partition wall, and an outer peripheral wall.
The second surface faces the first surface and is opposed to the first surface.
The partition wall is formed between the first surface and the second surface.
In the cross section parallel to the first surface, the partition wall extends in a grid pattern to partition a plurality of hollow cells.
In the cross section parallel to the first surface, the outer peripheral wall surrounds the partition wall.
Each of the plurality of hollow cells penetrates the honeycomb core in the direction from the first surface to the second surface.
The separator spatially separates the positive electrode and the negative electrode.
The separator comprises a first layer and a second layer.
The first layer covers at least a part of the partition wall, and the first layer covers at least a part of the partition wall.
The second layer covers at least a part of the first surface and the second surface.
The positive electrode includes a first region and a second region.
The first region is filled in the hollow cell, and the first region is filled.
The second region extends so as to project outward from the second layer of the separator in a cross section perpendicular to the first surface.
In the cross section parallel to the first surface, the first layer in the hollow cell has a minimum thickness and a maximum thickness.
The ratio of the maximum thickness to the minimum thickness is 1.45 or less.
battery.

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