阅读说明：本技术 全固体二次电池 (All-solid-state secondary battery ) 是由 田中一正 于 2020-03-16 设计创作，主要内容包括：一种全固体二次电池(100),其包括正极层(1)与负极层(2)隔着固体电解质层(3)叠层而成的叠层体(20)、第一外部端子(6)和第二外部端子(7),叠层体(20)具有与叠层方向平行的第一侧面(21、23)和与叠层方向平行且与上述第一侧面(21、23)正交的第二侧面(22、24),上述第一外部端子(6)和上述第二外部端子(7)分别与上述第一侧面(21、23)连接,上述叠层体(20)具有沿叠层方向翘起的满足式(1)和(2)的翘曲：0.5°≤((A1+A2)/2)≤5°…(1)A1≤8.0°…(2),在此,A1为从上述第一侧面(21、23)侧观察时上述叠层体(20)的翘曲的角度,A2为从上述第二侧面(22、24)侧观察时上述叠层体(20)的翘曲的角度。(An all-solid-state secondary battery (100) comprising a laminate (20) in which a positive electrode layer (1) and a negative electrode layer (2) are laminated with a solid electrolyte layer (3) therebetween, a first external terminal (6), and a second external terminal (7), wherein the laminate (20) has first side surfaces (21, 23) parallel to the lamination direction and second side surfaces (22, 24) parallel to the lamination direction and orthogonal to the first side surfaces (21, 23), the first external terminal (6) and the second external terminal (7) are connected to the first side surfaces (21, 23), respectively, and the laminate (20) has warpage satisfying the following formulae (1) and (2) that warps in the lamination direction: 0.5 DEG-5 DEG ((A1+ A2)/2) ≦ 5 DEG … (1) A1 ≦ 8.0 DEG … (2), where A1 is an angle of warpage of the laminate (20) when viewed from the first side surface (21, 23) side, and A2 is an angle of warpage of the laminate (20) when viewed from the second side surface (22, 24) side.)

1. An all-solid secondary battery characterized in that,

comprises a laminate of a positive electrode layer having a positive electrode collector layer and a positive electrode active material layer and a negative electrode layer having a negative electrode collector layer and a negative electrode active material layer,

the laminate has a first side surface parallel to the lamination direction and a second side surface parallel to the lamination direction and orthogonal to the first side surface,

the first external terminal and the second external terminal are connected to the first side surface respectively,

the laminated body has a warp satisfying formulas (1) and (2) which warps in the laminating direction,

0.5°≤((A1+A2)/2)≤5°…(1)

A1≤8.0°…(2)

Wherein A1 is the angle of warpage of the laminate when viewed from the first side surface side, and A2 is the angle of warpage of the laminate when viewed from the second side surface side.

2. The all-solid secondary battery according to claim 1,

satisfies the formula (3),

0.5°≤((A1+A2)/2)≤4°…(3)。

Technical Field

The present invention relates to an all-solid secondary battery.

The present application claims priority based on Japanese application No. 2019-048907, 3/15/2019, the contents of which are incorporated herein by reference.

Background

In recent years, the development of electronic technology has been remarkable, and the reduction in size, weight, thickness, and functionality of portable electronic devices has been achieved. Along with this, there is a strong demand for a battery as a power source of electronic equipment to be small and lightweight, thin, and have improved reliability. Conventionally, in general-purpose lithium ion secondary batteries, an electrolyte (electrolytic solution) such as an organic solvent has been used as a medium for moving ions. However, in the battery having the above structure, there is a risk of leakage of the electrolytic solution.

Since organic solvents and the like used for the electrolytic solution are combustible substances, it is necessary to further improve the safety of the battery. Therefore, as one of the strategies for improving the safety of the battery, a technique of using a solid electrolyte as an electrolyte instead of an electrolytic solution has been proposed. In addition, an all-solid-state battery has been developed in which an all-solid-state electrolyte is used as an electrolyte and other components are also made of a solid.

For example, patent document 1 proposes an all-solid-state lithium secondary battery using a non-combustible solid electrolyte, all components of which are made of a solid. The laminate for an all-solid lithium secondary battery includes an active material layer containing a crystalline first substance capable of releasing and occluding lithium ions, and a solid electrolyte layer sinter-bonded to the active material layer containing a crystalline second substance having lithium ion conductivity. Patent document 1 describes that the filling rate of the solid electrolyte layer is preferably more than 70%.

On the other hand, patent document 2 describes a lithium ion conductive solid electrolyte having a porosity of 10 vol% or less, which is formed by firing a molded body containing an inorganic powder.

As described in patent documents 1 and 2, it is considered that a solid electrolyte constituting an all-solid battery is preferably dense.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2007-5279

Patent document 2: japanese laid-open patent publication No. 2007-294429

Patent document 3: international publication No. 2013/175993

Disclosure of Invention

Problems to be solved by the invention

However, as described in patent documents 1 and 2, in an all-solid-state battery in which a solid electrolyte layer is densified, internal stress is concentrated on the solid electrolyte layer due to volume expansion and contraction of an electrode layer generated during charge and discharge of the all-solid-state battery, and cracks may occur in some cases. As a result, the internal resistance was increased, and the cycle characteristics were deteriorated.

In order to solve such a problem, patent document 3 describes a solid electrolyte layer in which a portion having a low porosity is formed in a region of the solid electrolyte layer close to an electrode layer and a portion having a high porosity is formed in a region of the solid electrolyte layer away from the electrode layer. However, according to the study of the inventors of the present invention, when a portion having a high porosity and a portion having a low porosity are formed in the solid electrolyte layer as in patent document 3, the internal resistance of the solid electrolyte layer is rather increased, and satisfactory cycle characteristics cannot be obtained.

The purpose of the present invention is to provide an all-solid-state secondary battery having good cycle characteristics due to warping at a predetermined angle.

Means for solving the problems

In order to solve the above problems, the present invention provides the following solutions.

(1) An all-solid secondary battery according to a first aspect of the present invention includes a laminate in which a positive electrode layer and a negative electrode layer are laminated with a solid electrolyte layer interposed therebetween, the positive electrode layer having a positive electrode collector layer and a positive electrode active material layer, the negative electrode layer having a negative electrode collector layer and a negative electrode active material layer, the laminate having a first side surface parallel to a lamination direction and a second side surface parallel to the lamination direction and orthogonal to the first side surface, the first external terminal and the second external terminal being connected to the first side surface, respectively, the laminate having warpage satisfying formulas (1) and (2) tilted in the lamination direction,

0.5°≤((A1+A2)/2)≤5°…(1)

A1≤8.0°…(2)

wherein A1 is an angle of warpage of the laminate when viewed from the first side surface side, and A2 is an angle of warpage of the laminate when viewed from the second side surface side.

(2) The all-solid-state secondary battery described in (1) above may satisfy formula (3).

0.5°≤((A1+A2)/2)≤4°…(3)

Effects of the invention

According to the present invention, it is possible to provide an all-solid-state secondary battery having good cycle characteristics due to warping at a predetermined angle.

Drawings

Fig. 1 is a schematic cross-sectional view of the all-solid secondary battery of the present embodiment.

Fig. 2 is a plan view of the laminate of the present embodiment.

Fig. 3 is a schematic diagram for explaining the definition of the warping angle a1, and is a diagram schematically showing the laminate when viewed from the first side surface side.

Fig. 4 is a schematic diagram for explaining the definition of the warping angle a2, and is a diagram schematically showing the laminate when viewed from the second side surface side.

Detailed Description

The present embodiment will be described in detail below with reference to the accompanying drawings as appropriate. For the sake of easy understanding of the features of the present embodiment, the drawings used in the following description may show the features in an enlarged scale, and the dimensional ratios of the components may be different from the actual ones. The materials, dimensions, and the like exemplified in the following description are only examples, and the present embodiment is not limited thereto, and may be modified as appropriate within a range in which the effects of the present invention can be obtained.

Examples of the all-solid-state secondary battery include an all-solid-state lithium ion secondary battery, an all-solid-state sodium ion secondary battery, and an all-solid-state magnesium ion secondary battery. In the following, an all-solid-state lithium-ion secondary battery will be described as an example, but the present invention is applicable to all-solid-state secondary batteries.

Fig. 1 is a schematic sectional view of an enlarged main portion of the all-solid lithium ion secondary battery according to the present embodiment.

The all-solid-state lithium-ion secondary battery shown in fig. 1 includes a laminate having a first electrode layer, a second electrode layer, and a solid electrolyte layer. Next, one of the first electrode layer and the second electrode layer functions as a positive electrode, and the other functions as a negative electrode. The positive and negative of the electrode layer change according to the polarity of connection to the external terminal. For ease of understanding, the first electrode layer will be described as a positive electrode layer and the second electrode layer as a negative electrode layer.

The all-solid lithium ion secondary battery 100 has a laminate 20, the laminate 20 having a positive electrode layer 1 including a positive electrode collector layer 1A and a positive electrode active material layer 1B, a negative electrode layer 2 including a negative electrode collector layer 2A and a negative electrode active material layer 2B, and a solid electrolyte layer 3 including a solid electrolyte, and the positive electrode layer 1 and the negative electrode layer 2 are alternately laminated with the solid electrolyte layer 3 interposed therebetween.

The positive electrode layers 1 are connected to first external terminals 6, respectively, and the negative electrode layers 2 are connected to second external terminals 7, respectively. The first external terminal 6 and the second external terminal 7 are electrical contacts with the outside.

(laminated body)

The laminate 20 has a positive electrode layer 1, a negative electrode layer 2, and a solid electrolyte layer 3.

In the laminate 20, the positive electrode layers 1 and the negative electrode layers 2 are alternately laminated with the solid electrolyte layers 3 (more specifically, interlayer solid electrolyte layers 3A) interposed therebetween. The all-solid-state lithium ion secondary battery 100 is charged and discharged by the transfer of lithium ions between the positive electrode layer 1 and the negative electrode layer 2 through the solid electrolyte layer 3.

The number of stacked positive electrode layers 1 and negative electrode layers 2 is not particularly limited, but the total number of positive electrode layers 1 and negative electrode layers 2 is generally in the range of 10 to 200 layers, and preferably in the range of 20 to 100 layers.

The laminate 20 is substantially a hexahedron and has four side surfaces (a first side surface 21, a second side surface 22, a first side surface 23, and a second side surface 24) formed as surfaces parallel to the lamination direction (Z direction in fig. 2), and an upper surface located above and a lower surface located below formed as surfaces substantially orthogonal to the lamination direction.

The first side surface is a surface where the electrode layer is exposed, and in the example shown in fig. 1 and 2, the positive electrode layer 1 is exposed at the first side surface 21, and the negative electrode layer 1 is exposed at the first side surface 23. The second side surface is a side surface where the electrode layer is not exposed. The second side surface 22 is a side surface whose upper surface is the right side as viewed from the first side surface 21 side, and is a side surface parallel to the stacking direction and substantially orthogonal to the first side surface 21 and the first side surface 23. The second side surface 24 is a side surface whose upper surface is the left side as viewed from the first side surface 21 side, and is a side surface parallel to the stacking direction and substantially orthogonal to the first side surface 21 and the first side surface 23.

Here, in the warpage of the laminate described below, either one of the first side surface 21 and the first side surface 23 may be selected as the first side surface, and either one of the second side surface 22 and the second side surface 24 may be selected as the second side surface.

(warping of the laminate)

The laminate 20 has a first side surface 21 (or a first side surface 23) parallel to the lamination direction and a second side surface 22 (or a second side surface 24) parallel to the lamination direction (z direction) and orthogonal to the first side surface 21, and has warpage satisfying formulas (1) and (2) which warps in the lamination direction.

0.5°≤((A1+A2)/2)≤5°…(1)

A1≤8.0°…(2)

Here, a1 is an angle of warpage of the laminate 20 when viewed from the first side surface 21 (or the first side surface 23) side, and a2 is an angle of warpage of the laminate 20 when viewed from the second side surface 22 (or the second side surface 24) side.

Fig. 3 is a schematic diagram for explaining the definition of the warping angle a1, and is a diagram schematically showing the laminate 20 when viewed from the first side surface 21 side.

The warping angle a1 of the laminate 20 when viewed from the first side surface 21 side will be described with reference to fig. 3. The laminated body 20 is left standing with the convex side in the Z direction facing the flat stage S side.

P1 is a point in contact with the surface Sa of the flat stage S in the first side 21 or a point closest to the surface Sa of the flat stage S in the first side 21, and P2 is a point closest to the surface Sa of the flat stage S in the side L1 common to the first side 21 and the second side 22.

The angle formed by the surface Sa of the flat stage S and the line segment connecting P1 and P2 is the angle a1 of warpage of the laminate 20.

Instead of P2, the point P3 closest to the surface Sa of the flat table S on the side L2 common to the first side surface 21 and the second side surface 24 may be used, and the angle formed by the surface Sa of the flat table S and the line segment connecting P1 and P3 may be used as the angle a1 of the warp of the laminate 20. In the case where the angle formed by the line segment connecting P1 and P2 and the angle formed by the line segment connecting P1 and P3 are different, the angle formed by the line segment having a larger angle is taken as the angle a1 of the warpage of the laminate 20.

Fig. 4 is a schematic diagram for explaining the definition of the warping angle a2, and is a diagram schematically showing the laminate 20 when viewed from the second side surface 22 side.

The warping angle a2 of the laminate 20 when viewed from the second side surface 22 side will be described with reference to fig. 4. The laminated body 20 is left standing with the convex side in the Z direction facing the flat stage S side.

Q1 is a point in the second side 22 that contacts the surface Sa of the flat stage S or a point in the second side 22 that is closest to the surface Sa of the flat stage S, and Q2 is a point in the side L3 common to the second side 22 and the first side 23 that is closest to the surface Sa of the flat stage S.

The angle formed by the surface Sa of the flat table and the line segment connecting Q1 and Q2 is the angle a2 of warpage of the laminate 20.

Instead of Q2, the point Q3 closest to the surface Sa of the flat table S on the side L1 common to the second side surface 22 and the first side surface 21 may be used, and the angle formed by the surface Sa of the flat table S and the line segment connecting Q1 and Q3 may be used as the angle a2 of the warp of the laminate 20. In the case where the angle formed by the line segment connecting Q1 and Q2 and the angle formed by the line segment connecting Q1 and Q3 are different, the angle formed by the line segment having a larger angle is taken as the angle a2 of the warpage of the laminate 20.

The inventors of the present invention have found that an all-solid-state battery having good cycle characteristics can be manufactured when the warpage of the laminate satisfies the above-described formulae (1) and (2). The mechanism of the structure in which the warpage of the laminate is within the predetermined range and the mechanism of the good cycle characteristics are not known at present, but if the laminate has warpage within the predetermined range in advance, the volume expansion and contraction of the electrode layers occurring during charge and discharge of the all-solid battery follows the direction of the warpage, and therefore the expansion and contraction stress of the volume is relaxed, and as a result, good cycle characteristics can be obtained.

The warpage of the laminate 20 preferably satisfies formula (3):

0.5°≤((A1+A2)/2)≤4°…(3)。

when the warpage of the laminate 20 satisfies the formula (3), a better cycle characteristic can be obtained.

The warpage of the laminate 20 more preferably satisfies formula (4):

A1≤4.5°…(4)

when the warpage of the laminate 20 satisfies the formula (4), a better cycle characteristic can be obtained.

(Positive electrode layer and negative electrode layer)

The positive electrode layer 1 includes a positive electrode collector layer 1A and a positive electrode active material layer 1B containing a positive electrode active material. The negative electrode layer 2 has a negative electrode current collector layer 2A and a negative electrode active material layer 2B containing a negative electrode active material.

The positive electrode collector layer 1A and the negative electrode collector layer 2A each contain a positive electrode collector or a negative electrode collector having high electrical conductivity. Examples of the positive electrode current collector and the negative electrode current collector having high conductivity include metals or alloys containing at least any one metal element of silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), and nickel (Ni), and non-metals such as carbon (C). Among these metal elements, copper and nickel are preferable in view of the high or low conductivity and the production cost. Moreover, copper is difficult to react with the positive electrode active material, the negative electrode active material, and the solid electrolyte. Therefore, when copper is used for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A, the internal resistance of the all-solid lithium ion secondary battery 100 can be reduced. The positive electrode collector layer 1A and the negative electrode collector layer 2A may be formed of the same material or different materials. The thicknesses of the positive electrode collector layer 1A and the negative electrode collector layer 2A are not limited, but may be in the range of 0.5 μm to 30 μm, if exemplified as a standard.

The positive electrode active material layer 1B is formed on one surface or both surfaces of the positive electrode current collector layer 1A. For example, the positive electrode layer 1 positioned at the uppermost layer in the stacking direction of the all-solid lithium ion secondary battery 100 does not have the opposite negative electrode layer 2 on the upper side in the stacking direction. Therefore, in the positive electrode layer 1 positioned at the uppermost layer in the all-solid lithium ion secondary battery 100, the positive electrode active material layer 1B may be positioned on only one side in the stacking direction, but there is no particular problem even when positioned on both sides. The negative electrode active material layer 2B is formed on one surface or both surfaces of the negative electrode current collector layer 2A, as in the positive electrode active material layer 1B. The thickness of the positive electrode active material layer 1B and the negative electrode active material layer 2B is preferably in the range of 0.5 μm to 5.0 μm. By setting the thickness of the positive electrode active material layer 1B and the negative electrode active material layer 2B to 0.5 μm or more, the capacity of the all-solid-state lithium ion secondary battery can be increased, and by setting the thickness to 5.0 μm or less, the diffusion distance of lithium ions is shortened, and therefore, the internal resistance of the all-solid-state lithium ion secondary battery can be further reduced.

The positive electrode active material layer 1B and the negative electrode active material layer 2B contain a positive electrode active material or a negative electrode active material that transfers lithium ions and electrons, respectively. Further, a conductive assistant and the like may be contained. The positive electrode active material and the negative electrode active material are preferably capable of efficiently inserting and extracting lithium ions.

The active materials constituting the positive electrode active material layer 1B or the negative electrode active material layer 2B are not clearly distinguished, and the potentials of the two compounds may be compared, and a compound showing a higher potential may be used as the positive electrode active material, and a compound showing a lower potential may be used as the negative electrode active material. Therefore, the active materials will be comprehensively described below.

As the active material, a transition metal oxide, a transition metal composite oxide, or the like can be used. For example, the transition metal oxide and the transition metal composite oxide include a lithium manganese composite oxide Li₂Mn_aMa_1－aO₃(0.8. ltoreq. a.ltoreq.1, Ma. Co, Ni), lithium cobaltate (LiCoO)₂) Lithium nickelate (LiNiO)₂) Lithium manganese spinel (LiMn)₂O₄) General formula (VII): LiNi_xCo_yMn_zO₂(x + y + z is 1, x is 0. ltoreq. 1, y is 0. ltoreq. 1, and z is 0. ltoreq. 1), and a lithium vanadium compound (LiV)₂O₅) Olivine-type LiM_bPO₄(wherein, M_bIs one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al and Zr), and lithium vanadium phosphate (Li)₃V₂(PO₄)₃Or LiVOPO₄)、Li₂MnO₃－LiM_cO₂(M_cLi-excess solid solution positive electrode represented by Mn, Co, and Ni), and lithium titanate (Li)₄Ti₅O₁₂)、Li_sNi_tCo_uAl_vO₂(s is more than 0.9 and less than 1.3, and t + u + v is more than 0.9 and less than 1.1).

The positive electrode collector layer 1A and the negative electrode collector layer 2A may contain a positive electrode active material and a negative electrode active material, respectively. The content ratio of the active material contained in each current collector layer is not particularly limited as long as the active material can function as a current collector. For example, the positive electrode collector/positive electrode active material or the negative electrode collector/negative electrode active material is preferably in a range of 90/10 to 70/30 in terms of volume ratio.

When the positive electrode collector layer 1A and the negative electrode collector layer 2A contain the positive electrode active material and the negative electrode active material, respectively, the adhesion between the positive electrode collector layer 1A and the positive electrode active material layer 1B and between the negative electrode collector layer 2A and the negative electrode active material layer 2B is improved.

(solid electrolyte layer)

As shown in fig. 1, the solid electrolyte layer 3 has an interlayer solid electrolyte layer 3A located between the cathode active material layer 1B and the anode active material layer 2B.

The solid electrolyte layer 3 may further include an outermost solid electrolyte layer 3B located outside one or both (both in fig. 1) of the positive electrode layer 1 (positive electrode collector layer 1A) and the negative electrode layer 2 (negative electrode collector layer 2A). Here, "outside" refers to the outside of the positive electrode layer 1 or the negative electrode layer 2 closest to the surfaces 5A, 5B of the laminate 20.

In addition, the solid electrolyte layer 3 may not have the outermost solid electrolyte layer 3B, and in this case, the surfaces 5A, 5B of the laminate 20 may be the positive electrode layer 1 and the negative electrode layer 2.

In the solid electrolyte layer 3, a material having low electron conductivity and high lithium ion conductivity is preferably used. The solid electrolyte layer 3 is preferably selected from, for example, La_0.5Li_0.5TiO₃Iso perovskite type compounds, or Li₁₄Zn(GeO₄)₄Isolisicon (lithium super ion) type compound, Li ₇La₃Zr₂O₁₂Isogarnet-type compound, LiZr₂(PO₄)₃、Li_1.3Al_0.3Ti_1.7(PO₄)₃Or Li_1.5Al_0.5Ge_1.5(PO₄)₃iso-NASICON (sodium super ion) type compound, Li_3.25Ge_0.25P_0.75S₄Or Li₃PS₄Equal THIO-LISICON (lithium sulfide super ion) type compound, Li₂S－P₂S₅Or Li₂O－V₂O₅－SiO₂Isoglass compound, Li₃PO₄Or Li_3.5Si_0.5P_0.5O₄Or Li_2.9PO_3.3N_0.46And the like.

The solid electrolyte layer 3 is preferably selected in accordance with the active material used for the positive electrode layer 1 and the negative electrode layer 2. For example, the solid electrolyte layer 3 more preferably contains the same element as the element constituting the active material. By the solid electrolyte layer 3 containing the same element as the element constituting the active material, the junction at the interface of the positive electrode active material layer 1B and the negative electrode active material layer 2B with the solid electrolyte layer 3 becomes strong. Further, the contact area at the interface between the positive electrode active material layer 1B and the negative electrode active material layer 2B and the solid electrolyte layer 3 can be increased.

The thickness of the interlayer solid electrolyte layer 3A is preferably in the range of 0.5 μm to 20.0 μm. By setting the thickness of the interlayer solid electrolyte layer 3A to 0.5 μm or more, short-circuiting between the positive electrode layer 1 and the negative electrode layer 2 can be reliably prevented, and by setting the thickness to 20.0 μm or less, the moving distance of lithium ions is shortened, and therefore, the internal resistance of the all-solid-state lithium ion secondary battery can be further reduced.

The thickness of the outermost solid electrolyte layer 3B is not particularly limited, and may be, for example, 1 to 40% relative to the thickness of the laminate 20. By providing the outermost solid electrolyte layer, the solid electrolyte layer 3 and each electrode layer can be physically and chemically protected, and durability and moisture resistance can be improved, as in the edge layer described later.

(edge layer)

As shown in fig. 1, the laminate 20 may include an edge layer 4 that includes a solid electrolyte and is disposed in parallel with each of the positive electrode layer 1 and the negative electrode layer 2. The solid electrolyte contained in the edge layer 4 may be the same as or different from the solid electrolyte contained in the solid electrolyte layer 3.

In order to eliminate the step difference between the interlayer solid electrolyte layer 3A and the positive electrode layer 1 and the step difference between the interlayer solid electrolyte layer 3A and the negative electrode layer 2, the edge layer 4 is preferably provided. Therefore, the edge layer 4 is formed on the main surface of the solid electrolyte layer 3 at a height substantially equal to that of the positive electrode layer 1 or the negative electrode layer 2 (that is, so as to be arranged side by side with each of the positive electrode layer 1 and the negative electrode layer 2) in a region other than the positive electrode layer 1 and the negative electrode layer 2. The presence of the edge layer 4 eliminates the step difference between the solid electrolyte layer 3 and the positive electrode layer 1 and between the solid electrolyte layer 3 and the negative electrode layer 2, and therefore, the density of the solid electrolyte layer 3 and each electrode layer is improved, and delamination (delamination) or warpage due to firing of the all-solid battery is less likely to occur.

The material constituting the edge layer 4 is preferably selected from, for example, La_0.5Li_0.5TiO₃Iso perovskite type compounds, or Li₁₄Zn(GeO₄)₄Isolisicon-type compound, Li₇La₃Zr₂O₁₂Isogarnet-type compound, LiZr₂(PO₄)₃、Li_1.3Al_0.3Ti_1.7(PO₄)₃Or Li_1.5Al_0.5Ge_1.5(PO₄)₃iso-NASICON type compound, Li_3.25Ge_0.25P_0.75S₄Or Li₃PS₄Iso THIO-LISICON type compound, Li₂S－P₂S₅Or Li₂O－V₂O₅－SiO₂Isoglass compound, Li₃PO₄Or Li_3.5Si_0.5P_0.5O₄Or Li_2.9PO_3.3N_0.46And the like.

(terminal)

The first external terminal 6 and the second external terminal 7 of the all-solid lithium ion secondary battery 100 preferably use a material having high electrical conductivity. For example, silver (Ag), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), tin (Sn), nickel (Ni), and chromium (Cr) can be used. The terminal may be a single layer or a plurality of layers.

(protective layer)

The all-solid lithium ion secondary battery 100 may have a protective layer (not shown) for electrically, physically, and chemically protecting the laminate 20 and the terminals on the outer periphery of the laminate 20. As a material constituting the protective layer, a material excellent in insulation, durability, and moisture resistance and safe from the environmental aspect is preferable. For example, glass or ceramic, a thermosetting resin, or a photocurable resin is preferably used. The material of the protective layer may be used alone or in combination of two or more. In addition, the protective layer may be a single layer, but preferably has a plurality of layers. Among these, an organic-inorganic blend in which a thermosetting resin and a ceramic powder are mixed is particularly preferable.

(method of manufacturing all-solid lithium ion Secondary Battery)

The method of manufacturing the all-solid lithium ion secondary battery 100 may use a simultaneous firing method. In this manufacturing method, the laminate is manufactured by firing different materials of the active material layer, the current collector layer, and the solid electrolyte layer that constitute the laminate 20 together. In the case of using the simultaneous firing method, the number of operation steps of the all-solid lithium ion secondary battery 100 can be reduced. And the laminate 20 obtained by the simultaneous firing method becomes dense. The following description will be given by taking a case of using the simultaneous firing method as an example.

The co-firing method includes a step of preparing a paste of each material constituting the laminate 20, a step of applying a paste for a solid electrolyte and drying the applied paste to prepare a solid electrolyte layer sheet, a step of forming a positive electrode layer and a negative electrode layer on the solid electrolyte sheet to prepare a positive electrode unit and a negative electrode unit, a step of alternately stacking the positive electrode unit and the negative electrode unit to prepare a laminate, and a step of co-firing the obtained laminate. Next, each step will be described in more detail.

First, the materials of the positive electrode collector layer 1A, the positive electrode active material layer 1B, the solid electrolyte layer 3, the negative electrode active material layer 2B, the negative electrode collector layer 2A, and the edge layer 4 constituting the laminate 20 are prepared into a paste.

The method for producing the paste is not particularly limited. For example, a paste can be obtained by mixing powders of the respective materials with a carrier. Herein, the carrier is a generic term of a liquid phase medium. The carrier comprises a solvent and a bonding agent. By this method, a paste for the positive electrode collector layer 1A, a paste for the positive electrode active material layer 1B, a paste for the solid electrolyte layer 3, a paste for the negative electrode active material layer 2B, a paste for the negative electrode collector layer 2A, and a paste for the edge layer 4 were prepared.

In producing the laminate 20, a positive electrode cell and a negative electrode cell described below are prepared, and a laminate is produced.

First, the solid electrolyte layer 3 was formed into a sheet shape from the paste on the PET film by the doctor blade method, and the sheet was dried to form a solid electrolyte layer sheet. The paste for the positive electrode active material layer 1B was printed on the obtained solid electrolyte layer sheet by screen printing and dried to form the positive electrode active material layer 1B.

Next, a paste for the positive electrode collector layer 1A was printed on the prepared positive electrode active material layer 1B by screen printing, and dried to form the positive electrode collector layer 1A. Then, the paste for the positive electrode active material layer 1B was printed again thereon by screen printing and dried. Then, an edge layer paste was screen-printed on the region of the solid electrolyte layer sheet other than the positive electrode layer, and was dried to form an edge layer having a height substantially equal to that of the positive electrode layer. Then, the PET film was peeled off, whereby a positive electrode unit was obtained in which the positive electrode layer 1 and the edge layer 4 were formed by sequentially laminating the positive electrode active material layer 1B/the positive electrode current collector layer 1A/the positive electrode active material layer 1B on the main surface of the solid electrolyte layer 3.

In the same manner, a negative electrode unit was obtained in which the negative electrode layer 2 and the edge layer 4 were formed by sequentially laminating the negative electrode active material layer 2B, the negative electrode current collector layer 2A, and the negative electrode active material layer 2B on the main surface of the solid electrolyte layer 3.

Then, the positive electrode cells and the negative electrode cells were alternately shifted so that their respective ends were not aligned, and stacked to produce a stacked body of an all-solid battery. Further, solid electrolyte layers may be provided at both ends of the laminate in the laminating direction. As for the disposed positive electrode unit or negative electrode unit, the outermost solid electrolyte layers 3B are used for the solid electrolyte layers 3, respectively, and as for the positive electrode unit or negative electrode unit disposed therebetween, the interlayer solid electrolyte layers 3A are used for the solid electrolyte layers 3, respectively.

The above-described manufacturing method is a method of manufacturing a parallel-type all-solid battery, and the manufacturing method of a series-type all-solid battery may be laminated so that one end of the positive electrode layer 1 and one end of the negative electrode layer 2 are aligned, that is, without being offset.

The obtained laminate is collectively pressed by die pressing, warm Water Isostatic Pressing (WIP), cold water isostatic pressing (CIP), isostatic pressing, or the like, whereby the adhesion can be improved. The pressing is preferably performed while heating, and may be performed at 40 to 95 ℃.

The obtained laminate may be cut into small pieces using a cutting device, followed by degumming and firing, thereby producing a laminate of all-solid batteries.

In the degumming step, the binder component contained in the laminate 20 is decomposed by heating in advance before firing, whereby the binder component can be prevented from being excessively and rapidly decomposed in the firing step. In the degumming step, the laminate 20 thus obtained is placed on a ceramic setter for a base, and may be subjected to a heating at 300 to 800 ℃ for 0.1 to 10 hours in a nitrogen atmosphere, for example. The degumming step may be performed in a reducing atmosphere, for example, an argon atmosphere or a mixed nitrogen-hydrogen atmosphere instead of a nitrogen atmosphere. In addition, if the metal collector layer is not oxidized, a reducing atmosphere containing a small amount of oxygen may be used.

In the firing, for example, a sintered body is obtained by performing a heat treatment in a nitrogen atmosphere at a temperature range of 600 to 1000 ℃. The firing time is, for example, 0.1 to 3 hours. As long as the atmosphere is a reducing atmosphere, for example, an argon atmosphere or a mixed nitrogen-hydrogen atmosphere may be used instead of the nitrogen atmosphere for firing.

Here, various methods can be employed to produce the laminate 20 having a desired warpage. For example, the following methods can be used: by utilizing the phenomenon that warpage is likely to occur when rapid firing is performed in the firing step, a ceramic positioner for a cover for controlling warpage is arranged so that the rise Δ h of the height corresponding to a desired warpage angle after firing is added to the height of the side surface of the laminate before firing (the height h from the ceramic positioner for a base to the side surface of the laminate) ₀) Height position h of₁The laminate is prevented from being warped to a greater extent. In this method, a gap for forming a desired warping angle is provided between the ceramic positioner for a lid and the laminate. Wherein the height position h of the ceramic positioner for the cover is configured₁In order to take into account the high position of shrinkage of the laminate after firing. The height position of the ceramic positioner for the cover can be easily adjusted by arranging the multilayer body for height adjustment at the four corners of the ceramic positioner for the base. For example, when the gap between the laminate before firing and the ceramic positioner for a lid is set to 10 μm, a height-adjusting laminate having a thickness 10 μm larger than that of the laminate before firing may be prepared. The rapid firing means firing at a temperature rise rate of 1000 ℃/hr or more, for example. In addition, in order to further control the warpage, the ceramic setter for the base and the ceramic setter for the cover are preferably smooth ceramic setters. For example, ceramics in which the main surface of the ceramic retainer is ground may be usedPorcelain locator. The ceramic positioner may be a dense substrate or a porous substrate having holes. The material is preferably a material having a sintering temperature higher than the firing temperature of the laminate, and is preferably zirconia, alumina, or the like, for example.

In addition, the thickness of the outermost solid electrolyte layer 3B of the laminate 20 is changed on the side surfaces 5A and 5B, so that the firing shrinkage ratios of the outermost solid electrolyte layers of the side surfaces 5A and 5B are different, whereby the laminate 20 having a desired warpage can be produced.

The sintered body may be put into a cylindrical container together with an abrasive such as alumina and barrel-polished. This enables chamfering of the corners of the laminate. As another method, the polishing may be performed by sandblasting.

(terminal formation)

The first external terminal 6 and the second external terminal 7 are mounted on the sintered laminate 20 (sintered body). The first external terminal 6 and the second external terminal 7 are formed in electrical contact with the positive electrode layer 1 and the negative electrode layer 2, respectively. For example, the positive electrode layer 1 and the negative electrode layer 2 exposed from the side surfaces of the sintered body are formed by a known method such as sputtering, dip coating, screen printing, or spray coating.

When the film is formed only in a predetermined portion, the film is formed by, for example, masking with a tape.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings, but the configurations of the embodiments and the combinations thereof are merely examples, and additions, omissions, substitutions, and other modifications of the configurations may be made without departing from the spirit of the present invention.

For example, although the electrode layer is not exposed on the second side surface in the laminate 20 shown in fig. 2, at least one of the positive electrode layer 1 and the negative electrode layer 2 may be exposed on the second side surface.

Examples

[ example 1]

(preparation of paste for solid electrolyte layer)

In Li_1.3Al_0.3Ti_1.7(PO₄)₃100 parts of ethanol and 200 parts of toluene as solvents were added to 100 parts of the powder of (1), and wet-mixed by a ball mill. Then, 16 parts of a binder and 4.8 parts of tolylbutyl phthalate as a plasticizer were further charged and mixed to prepare an outermost solid electrolyte layer paste.

This solid electrolyte layer paste was formed into a sheet by a doctor blade method using a PET film as a substrate, to obtain an outermost solid electrolyte layer sheet and an interlayer solid electrolyte layer sheet. The thickness of each of the outermost solid electrolyte layer sheet and the interlayer solid electrolyte layer sheet was 20 μm.

(preparation of paste for Positive electrode active Material layer and paste for negative electrode active Material layer)

The positive electrode active material layer paste and the negative electrode active material layer paste are mixed with Li at a predetermined weight ratio₃V₂(PO₄)₃Then, to 100 parts of the powder, 15 parts of a binder and 65 parts of dihydroterpineol as a solvent were added, and mixed and dispersed to prepare a positive electrode active material layer paste and a negative electrode active material layer paste.

(preparation of paste for Positive electrode collector layer and paste for negative electrode collector layer)

The paste for the positive electrode collector layer and the paste for the negative electrode collector layer were prepared by adding 100 parts of Cu as a collector, 10 parts of a binder, and 50 parts of dihydroterpineol as a solvent, mixing and dispersing them.

(preparation of electrode Unit)

The positive electrode cell and the negative electrode cell were produced as follows.

An active material paste was printed on the interlayer solid electrolyte layer sheet by screen printing to a thickness of 5 μm. Next, the printed paste for active material was dried, and a paste for collector was printed thereon by screen printing to a thickness of 5 μm. Subsequently, the printed paste for the collector was dried, and the paste for the active material was printed again thereon by screen printing to a thickness of 5 μm. The printed active material paste was dried, and then, the PET film was peeled off. As described above, the interlayer solid electrolyte sheet was printed with the active material paste, the collector paste, and the active material paste in this order, and dried to obtain a sheet of the electrode unit.

(preparation of a Stack)

The outermost solid electrolyte layer sheets were superposed, and electrode units 30 (positive electrode unit 15 sheets, negative electrode unit 15 sheets) were alternately stacked thereon via an interlayer solid electrolyte 3A. In this case, the cells are stacked in a staggered manner such that the collector paste layers of the odd-numbered electrode cells extend only on one end face and the collector paste layers of the even-numbered electrode cells extend only on the opposite end face. The outermost solid electrolyte layer 3B solid electrolyte layer sheet is stacked on the stacked unit. Thereafter, the laminate was formed by thermocompression bonding and cut to produce laminated chips. The chip size was 4.1mm × 6.0mm × 2.0mm, first side (W) × second side (L) × height (H). Thus, the aspect ratio of the platelets, W: L, is 1: 1.5.

Next, the small laminated pieces were set on a ceramic setter for a base, a ceramic setter for a cover was set at a height position where the average angle between the warpage a1 when viewed from the first side surface and the warpage a2 when viewed from the second side surface was 0.5 °, and then the small laminated pieces were simultaneously fired to obtain a laminated body 20. In addition, a height adjusting laminate having a thickness larger than the fired laminate piece by 14 μm was disposed at four corners of the ceramic setter for a base, and the ceramic setter for a cover was disposed thereon. In the co-firing, the temperature was raised to a firing temperature of 840 ℃ at a rate of 1000 ℃/hr in a nitrogen atmosphere, held at that temperature for 2 hours, and naturally cooled after firing.

(evaluation of amount of warpage)

The obtained laminate (sintered body) was placed on a flat table as shown in fig. 3, and a photograph was taken from the x direction, and the warpage angle a1 was obtained by image processing. Also, as described in fig. 4, a photograph is taken from the y direction, and the warping angle a2 is obtained by image processing.

(production and evaluation of all-solid-State Secondary Battery)

The first external terminal and the second external terminal were mounted on the sintered laminate (sintered body) by a known method to produce an all-solid secondary battery.

The first external terminal and the second external terminal were held between each other by a spring probe so as to face each other, and a charge-discharge test was performed to measure the initial discharge capacity and the capacity retention rate (cycle characteristic) after 1000 cycles of the all-solid secondary battery. Under the measurement conditions, the current during charge and discharge was 0.2C, and the end voltage during charge and discharge was 1.6V and 0V, respectively. The results are shown in table 1. Here, the capacity at the 1 st discharge was taken as the initial discharge capacity. The capacity retention rate was determined by dividing the discharge capacity at the 1000 th cycle by the initial discharge capacity.

The results are shown in Table 1.

[ Table 1]

[ examples 2 to 8]

In examples 2 to 8, an all-solid secondary battery was produced in the same manner as in example 1, except that the laminated small pieces were each left on a ceramic base, and that the height positions at which the average angles of the warpage a1 viewed from the first side surface and the warpage a2 viewed from the second side surface were 1.0 °, 1.8 °, 2.1 °, 2.5 °, 3.3 °, 3.5 °, and 4.0 °, respectively, were provided with a laminate for height adjustment and a ceramic positioner for a lid. The warpage a1 viewed from the first side face side and the warpage a2 viewed from the second side face side are shown in table 1.

[ examples 9 to 10]

An all-solid secondary battery was produced in the same manner as in example 1, except that in examples 9 to 10, small pieces having an aspect ratio W: L of 1: 3.5 and 1: 4.0 were used, respectively, and the stacked small pieces were placed on a ceramic table, and a height position where the average angle of the warpage a1 viewed from the first side surface and the warpage a2 viewed from the second side surface was 4.5 ° and 5.0 ° was set, and a ceramic positioner for a lid was provided. The warpage a1 viewed from the first side face side and the warpage a2 viewed from the second side face side are shown in table 1.

[ examples 11 to 13]

An all-solid secondary battery was produced in the same manner as in example 1 except that in each of examples 11 to 13, small pieces having an aspect ratio W: L of 1: 1 were used, and the stacked small pieces were each placed on a ceramic table, and a height adjusting laminate and a lid ceramic retainer were provided at height positions where the average angles of the warpage a1 viewed from the first side surface and the warpage a2 viewed from the second side surface were 1.5 °, 2.0 °, and 3.0 °. The warpage a1 viewed from the first side face side and the warpage a2 viewed from the second side face side are shown in table 1.

[ examples 14 to 18]

In each of examples 14 to 18, an all-solid secondary battery was produced in the same manner as in example 1 except that a chip-sized chip having a first side surface (W) × second side surface (L) × height (H) × 3.0mm × 4.4mm × 1.1mm (therefore, the aspect ratio W: L of the chip was 1: 1.5) was used, the laminated chip was placed on a ceramic table, and the height adjustment laminate and the lid ceramic setter were disposed at height positions at which the average angles of the warpage a1 viewed from the first side surface and the warpage a2 viewed from the second side surface were 1.0 °, 1.8 °, 2.3 °, 2.5 °, and 3.0 °. The warpage a1 viewed from the first side face side and the warpage a2 viewed from the second side face side are shown in table 1.

Comparative examples 1 to 2

In comparative examples 1 to 2, the procedure was carried out under the same conditions as in example 1 except that the laminated small pieces were each left on a ceramic table and the height adjustment laminate and the lid ceramic positioner were provided at height positions where the average angle between the warpage a1 when viewed from the first side surface and the warpage a2 when viewed from the second side surface was 0 ° and 0.2 °. The warpage a1 viewed from the first side face side and the warpage a2 viewed from the second side face side are shown in table 1.

Comparative examples 3 to 4

An all-solid secondary battery was produced in the same manner as in example 1, except that in comparative examples 3 to 4, small pieces having an aspect ratio W: L of 1: 1.2 and 1: 9.0 were used, respectively, and the laminated small pieces were left on a ceramic table, and a height position where the average angle of the warpage a1 viewed from the first side surface and the warpage a2 viewed from the second side surface was 6.5 ° and 5.0 ° was provided with a laminate for height adjustment and a ceramic positioner for a lid. The warpage a1 viewed from the first side face side and the warpage a2 viewed from the second side face side are shown in table 1.

Comparative example 5

An all-solid secondary battery was produced in the same manner as in example 11, except that in comparative example 5, the same small pieces as those used in examples 11 to 13 were used, the laminated small pieces were left on a ceramic table, and the height adjusting laminate and the lid ceramic anchor were provided at a height position at which the average angle between the warpage a1 when viewed from the first side surface and the warpage a2 when viewed from the second side surface was 6.0 °. The warpage a1 viewed from the first side face side and the warpage a2 viewed from the second side face side are shown in table 1.

Based on the results shown in table 1, cycle characteristics of 86% or more were obtained in examples 1 to 18 in which the average angle of the warpage a1 observed from the first side surface side and the warpage a2 observed from the second side surface side was 0.5 ° or more and 5.0 ° or less, and the angle of the warpage observed from the first side surface side was 8.0 ° or less.

In contrast, in the case where the average angle of the warpage a1 viewed from the first side surface side and the warpage a2 viewed from the second side surface side is less than 0.5 ° (comparative examples 1 and 2) or the case where the average angle exceeds 5.0 (comparative examples 3 and 5), the cycle characteristic is 82% or less.

In comparative example 4, in which the average angle was 5.0 ° and the angle of the warpage a1 as viewed from the first side surface side exceeded 8.0 °, the cycle characteristic was 72%.

In examples 1 to 8 and examples 11 to 18, in which the average angle between the warpage a1 when viewed from the first side surface side and the warpage a2 when viewed from the second side surface side is 0.5 ° to 4.0 °, cycle characteristics of 90% or more were obtained. Further, in these examples, the angle a1 of warpage as viewed from the first side face side is 4.5 ° or less.

It is understood that in examples 1 to 6, examples 11 to 13, and examples 14 to 18, the average angle of warpage is about the same, although the chip size and/or the aspect ratio are different from each other, and the same degree of cycle characteristics can be obtained.

Industrial applicability

According to the present invention, it is possible to provide an all-solid-state secondary battery having good cycle characteristics due to warping at a predetermined angle.

Description of the symbols

1: a positive electrode layer; 1A: a positive electrode collector layer; 1B: a positive electrode active material layer; 2: a negative electrode layer; 2A: a negative collector layer; 2B: a negative electrode active material layer; 3: a solid electrolyte layer; 6: a first external terminal; 7: a second external terminal; 20: a laminate; 100: an all-solid secondary battery.