Secondary battery

Abstract

This secondary battery has: a solid electrolyte layer having a first main surface and a second main surface on the opposite side from the first main surface; a positive electrode current collector provided on the first main surface; a positive electrode active material layer provided on the positive electrode current collector; a negative electrode current collector provided on the second main surface; and a negative electrode active material layer provided on the negative electrode current collector, wherein the negative electrode active material layer, the negative electrode current collector, the solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer are laminated in this order in a direction perpendicular to the first main surface.

Description

secondary battery

[0001] This invention relates to a secondary battery.

[0002] Patent Document 1 describes an all-solid-state battery constructed by stacking a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer in that order.

[0003] Japanese Patent Publication No. 2019-121485

[0004] In the all-solid-state battery described in Patent Document 1, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are sandwiched between the positive electrode current collector layer and the negative electrode current collector layer, resulting in a longer diffusion distance for carrier ions. This may make it difficult to pass large currents. Furthermore, the charge and discharge characteristics at high current rates may deteriorate.

[0005] The present invention aims to provide a secondary battery that can improve charge and discharge characteristics.

[0006] A secondary battery according to one embodiment includes a solid electrolyte layer having a first main surface and a second main surface opposite to the first main surface, a positive electrode current collector provided on the first main surface, a positive electrode active material layer provided on the positive electrode current collector, a negative electrode current collector provided on the second main surface, and a negative electrode active material layer provided on the negative electrode current collector, and the negative electrode active material layer, the negative electrode active material layer, the negative electrode current collector, the solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer are stacked in the order of the negative electrode active material layer, the negative electrode current collector, the solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer in a direction perpendicular to the first main surface.

[0007] According to the secondary battery of the present invention, charge and discharge characteristics can be improved.

[0008] Figure 1 is an exploded perspective view showing an example of a secondary battery according to the first embodiment. Figure 2 is an enlarged cross-sectional view showing a part of the cross-section of the electrode body according to Figure 1. Figure 3 is an enlarged cross-sectional view showing the current collector assembly according to Figure 2. Figure 4 is an explanatory diagram illustrating an example of a method for manufacturing a secondary battery according to the first embodiment. Figure 5 is a cross-sectional view showing a current collector assembly according to the second embodiment. Figure 6 is a cross-sectional view showing a current collector assembly according to the third embodiment.

[0009] Embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure. Each embodiment described in this disclosure is illustrative, and partial substitution or combination of configurations is possible between different embodiments. In modifications and subsequent embodiments, descriptions of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects and benefits due to similar configurations will not be mentioned sequentially for each embodiment.

[0010] (First Embodiment) Figure 1 is an exploded perspective view showing an example of a secondary battery according to the first embodiment. The secondary battery 1 shown in Figure 1 is a laminate-type lithium-ion secondary battery. As shown in Figure 1, the secondary battery 1 comprises a battery element 20, an outer casing member 30, and an adhesive material 32.

[0011] The battery element 20 is provided inside the outer casing member 30. The battery element 20 comprises an electrode body 200, a positive electrode lead 21, and a negative electrode lead 22. The positive electrode lead 21 is a terminal drawn out from the positive electrode current collector 212 (described later) to the outside of the outer casing member 30. In other words, the positive electrode lead 21 is the terminal that becomes the positive electrode of the secondary battery 1. In Figure 1, the positive electrode lead 21 is provided on the end face of the electrode body 200. The negative electrode lead 22 is a terminal drawn out from the inside of the negative electrode current collector 213 (described later) to the outside of the outer casing member 30. In other words, the negative electrode lead 22 is the terminal that becomes the negative electrode of the secondary battery 1. In Figure 1, the negative electrode lead 22 is provided on the end face of the electrode body 200. Details of the electrode body 200 will be described later.

[0012] The exterior member 30 is a case in which the battery element 20 is housed. The exterior member 30 includes two exterior sheets 30a and 30b. The exterior sheets 30a and 30b comprise an insulating layer, a metal layer, and an outermost layer. In the example shown in Figure 1, the exterior sheet 30a is provided with a recess 31. By housing the battery element 20 in the recess 31 and bonding the peripheral edges of the exterior sheets 30a and 30b, the battery element 20 is housed within the exterior member 30.

[0013] The outer sheets 30a and 30b are constructed by laminating an insulating layer, a metal layer, and an outermost layer in that order, starting from the inside, i.e., the side where the battery element 20 is installed, and then bonding them together by lamination or the like. The insulating layer of the outer sheets 30a and 30b is made of a resin such as polyethylene, polypropylene, modified polyethylene, modified polypropylene, or a polyolefin resin containing ethylene or propylene as a monomer. This allows the outer sheets 30a and 30b to reduce the moisture permeability of the secondary battery 1 and improve airtightness. The metal layer of the outer sheets 30a and 30b is made of a metal sheet or foil such as aluminum, stainless steel, nickel, or iron. The outermost layer may be made of any material, but it is preferable to make it of a material with high strength against tearing and punctures, such as a resin similar to the insulating layer or nylon.

[0014] The adhesive material 32 is a component for making the outer casing member 30 airtight. The adhesive material 32 is provided between the outer casing member 30 and the positive electrode lead 21 and the negative electrode lead 22. The material of the adhesive material 32 preferably has good adhesion to the positive electrode lead 21 and the negative electrode lead 22. For example, if the positive electrode lead 21 and the negative electrode lead 22 are made of metal, the adhesive material 32 can be made of a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene. As a result, the adhesive material 32 can seal the gap between the outer casing member 30 and the positive electrode lead 21 and the negative electrode lead 22, thereby making the inside of the outer casing member 30 airtight.

[0015] Figure 2 is an enlarged cross-sectional view showing a portion of the cross-section of the electrode body according to Figure 1. Figure 3 is an enlarged cross-sectional view showing the current collector assembly according to Figure 2.

[0016] As shown in Figure 2, the electrode body 200 has three sets of unit solid-state batteries 10. Each unit solid-state battery 10 includes a negative electrode active material layer 230, a negative electrode current collector 213, a solid electrolyte layer 211, a positive electrode current collector 212, and a positive electrode active material layer 220. The unit solid-state batteries 10 are stacked in the following order: negative electrode active material layer 230, negative electrode current collector 213, solid electrolyte layer 211, positive electrode current collector 212, and positive electrode active material layer 220, in a direction perpendicular to the first main surface 211a of the solid electrolyte layer 211 (see Figure 3).

[0017] In this embodiment, the electrode body 200 is constructed by stacking three sets of unit solid batteries 10, with a solid electrolyte layer 211A positioned between the unit solid batteries 10 in a direction perpendicular to the first main surface 211a. The solid electrolyte layer 211A positioned between the unit solid batteries 10 is made of the same material as the solid electrolyte layer 211 of the unit solid battery 10. However, the solid electrolyte layer 211A positioned between the layers may be made of a different material than the solid electrolyte layer 211 of the unit solid battery 10.

[0018] The number of solid-state batteries 10 in the electrode body 200 is not limited to three sets; it is sufficient to have at least one set of solid-state batteries 10. The electrode body 200 may have one or two sets of solid-state batteries 10, or four or more sets of solid-state batteries 10 may be stacked.

[0019] The positive electrode active material layer 220 and the negative electrode active material layer 230 contained in the electrode body 200 are layered members for the charge-discharge reaction of the secondary battery 1 according to the first embodiment. In the following description, one of the thickness directions of the electrode body 200 may be described as the Z1 direction, and the other thickness direction of the electrode body 200 may be described as the Z2 direction. Note that the thickness direction is the same as the direction perpendicular to the first main surface 211a (see Figure 3) of the solid electrolyte layer 211.

[0020] Furthermore, as shown in Figures 2 and 3, the negative electrode current collector 213, solid electrolyte layer 211, and positive electrode current collector 212 of the unit solid-state battery 10 may be referred to as the current collector assembly 210. As shown in Figure 3, the current collector assembly 210 comprises the solid electrolyte layer 211, the positive electrode current collector 212, and the negative electrode current collector 213.

[0021] The solid electrolyte layer 211 has a first main surface 211a and a second main surface 211b opposite to the first main surface 211a, and is made of a lithium-ion conductive material. Specifically, the solid electrolyte layer 211 contains one or more types of materials, such as crystalline solid electrolytes and glass-ceramic solid electrolytes.

[0022] A crystalline solid electrolyte is a crystalline electrolyte. Specifically, the crystalline solid electrolyte is, for example, an inorganic material and a polymer material, etc. The inorganic material is, for example, a sulfide, a halide, an oxide or a phosphide, etc. The sulfide is, for example, Li １．７５ , ２ , ２ , ｘ , ３ , ４ , ２ , ２／３－ｘ , ６ , ０．２５ , ２－ｘ , ６ , １２ , ２ , ３ , ３ｘ , ｘ , ６．７５ , ４ , ３ , ７ , １２ , ２ , １２ , ｙ , ３ , ６ , ３ , １＋ｘ , １２ , ３ , ６ S-P ２ S ５ 、Li ２ S-SiS ２ -Li ３ PO ４ 、Li ６ PS ５ Cl、Li ４ SnS ４ 、Li ７ P ３ S １１ 、Li ３．２５ Ge ０．２５ P ０．７５ S ４ およびLi １０ GeP ２ S １２ などである。ハロゲン化物は、例えば、Li ３ InCl ６ 、Li<了 ３ YCl ６ 、Li ２ ZrCl ６ などである。酸化物またはリン酸化物は、例えば、Li ｘ M ｙ (PO ４ ) ３ (1≦x≦2、1≦y≦2、Mは、Ti、Ge、Al、GaおよびZrから成る群より選ばれた少なくとも一種である)、Li ７ La ３ Zr ２ O １２ 、Li ６．７５ La ３ Zr １．７５ Nb ０．２５ ]> O １２ 、Li ６ BaLa ２ Ta ２ O １２ 、Li １＋ｘ Al ｘ Ti ２－ｘ (PO ４ ) ３ 、La ２／３－ｘ Li ３ｘ TiO It should be noted that there seems to be some incorrect tags in the original text (such as "<了 ３ "), which may affect the accuracy of the translation. Please check and correct the original text for a more accurate translation result.３ Li １．２ Al ０．２ Ti １．８ (PO ４ ) ３ La ０．５５ Li ０．３５ TiO ３ and Li ７ La ３ Zr ２ O １２ These are examples of polymer materials, such as polyethylene oxide (PEO).

[0023] Glass-ceramic solid electrolytes are electrolytes in which amorphous and crystalline materials coexist. Examples of such glass-ceramic solid electrolytes include oxides containing lithium (Li), silicon (Si), and boron (B) as constituent elements, and more specifically, lithium oxide (Li) ２ O), silicon dioxide (SiO ２ ) and boron oxide (B ２ O ３ ) and others are included. The ratio of lithium oxide content to the total content of lithium oxide, silicon oxide, and boron oxide is not particularly limited, but for example, it is 40 mol% to 73 mol%. The ratio of silicon oxide content to the total content of lithium oxide, silicon oxide, and boron oxide is not particularly limited, but for example, it is 8 mol% to 40 mol%. The ratio of boron oxide content to the total content of lithium oxide, silicon oxide, and boron oxide is not particularly limited, but for example, it is 10 mol% to 50 mol%. In order to measure the respective content of lithium oxide, silicon oxide, and boron oxide, the glass-ceramic solid electrolyte is analyzed using, for example, inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0024] Furthermore, examples of solid electrolytes capable of conducting sodium ions include sodium-containing phosphate compounds having a nasicone structure, oxides having a perovskite structure, and oxides having a garnet-type or garnet-type similar structure. Examples of sodium-containing phosphate compounds having a nasicone structure include Na ｘ M ｙ (PO４ ) ３ Examples include (1 ≤ x ≤ 2, 1 ≤ y ≤ 2, and M is at least one selected from the group consisting of Ti, Ge, Al, Ga, and Zr).

[0025] The solid electrolyte layer 211 may contain at least one of a binder and a sintering aid. The binder and sintering aid contained in the solid electrolyte layer 211 may be selected from materials similar to those contained in the positive electrode active material layer 220 and the negative electrode active material layer 230, for example.

[0026] The thickness of the solid electrolyte layer 211 is not particularly limited and may be, for example, 1 μm or more and 15 μm or less, and more particularly 1 μm or more and 5 μm or less.

[0027] The positive electrode current collector 212 is laminated on the first main surface 211a, which is the Z1 direction surface of the solid electrolyte layer 211. The positive electrode current collector 212 has a positive electrode conductive layer 212a having a plurality of pores and a positive electrode side solid electrolyte 212b. The positive electrode side solid electrolyte 212b is filled inside the pores of the positive electrode conductive layer 212a.

[0028] The positive electrode conductive layer 212a is, for example, a carbon material and a metallic material. Specifically, the carbon material is, for example, graphite and carbon nanotubes. The metallic material is, for example, copper (Cu), magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), indium (In), gold (Au), platinum (Pt), silver (Ag), and palladium (Pd), and may also be an alloy of two or more of these.

[0029] The multiple pores in the positive electrode conductive layer 212a are gaps formed between fibers when a fibrous carbon material such as carbon nanotubes is used. The carbon nanotubes in question are, for example, single-wall carbon nanotubes (SWCNTs).

[0030] However, the positive electrode conductive layer 212a is not limited to carbon nanotubes, but may be a metal foil formed using at least one of the above-mentioned metal materials. In this case, the positive electrode conductive layer 212a has a number of through holes penetrating the metal foil in the Z direction, thereby forming a number of micropores. Alternatively, the positive electrode conductive layer 212a may be a mesh-like metal foil. The shape, diameter, spacing, arrangement, etc., of the multiple through holes in the positive electrode conductive layer 212a can be changed as appropriate. As an example, the positive electrode conductive layer 212a is provided with circular through holes with a diameter of 1 μm at intervals of 1 μm.

[0031] The positive electrode side solid electrolyte 212b of the positive electrode current collector 212 may be made of the same material as the solid electrolyte layer 211 described above. The positive electrode side solid electrolyte 212b is provided by filling the multiple pores of the positive electrode conductive layer 212a. Specifically, the positive electrode side solid electrolyte 212b is provided extending from the surface of the positive electrode conductive layer 212a on the solid electrolyte layer 211 side to the surface on the positive electrode current collector 212 side. Furthermore, the positive electrode side solid electrolyte 212b is in contact with the first main surface 211a of the solid electrolyte layer 211 and is also in contact with the positive electrode active material layer 220. This allows carrier ions such as lithium ions to pass through the positive electrode current collector 212 in the thickness direction.

[0032] The negative electrode current collector 213 is laminated on the second main surface 211b, which is the Z2 direction surface of the solid electrolyte layer 211. The negative electrode current collector 213 has a negative electrode conductive layer 213a having a plurality of pores and a negative electrode side solid electrolyte 213b. The negative electrode side solid electrolyte 213b is filled inside the pores of the negative electrode conductive layer 213a.

[0033] The negative electrode conductive layer 213a is, for example, a carbon material and a metallic material. Specifically, the carbon material is, for example, graphite and carbon nanotubes. The metallic material is, for example, copper (Cu), magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), indium (In), gold (Au), platinum (Pt), silver (Ag), and palladium (Pd), and may also be an alloy of two or more of these.

[0034] The multiple pores in the negative electrode conductive layer 213a are gaps formed between fibers when a fibrous carbon material such as carbon nanotubes is used. The carbon nanotubes are, for example, single-wall carbon nanotubes (SWCNTs).

[0035] However, the negative electrode conductive layer 213a is not limited to carbon nanotubes, but may be a metal foil formed using at least one of the above-mentioned metal materials. In this case, the negative electrode conductive layer 213a has a number of through holes penetrating the metal foil in the Z direction, thereby forming a number of pores. Alternatively, the negative electrode conductive layer 213a may be a mesh-like metal foil. The shape, diameter, spacing, arrangement, etc., of the multiple through holes in the negative electrode conductive layer 213a can be changed as appropriate. For example, the negative electrode conductive layer 213a may have circular through holes with a diameter of 1 μm spaced 1 μm apart.

[0036] The negative electrode side solid electrolyte 213b of the negative electrode current collector 213 may be made of the same material as the solid electrolyte layer 211 described above. The negative electrode side solid electrolyte 213b is provided by filling the multiple pores of the negative electrode conductive layer 213a. Specifically, the negative electrode side solid electrolyte 213b is provided extending from the surface of the negative electrode conductive layer 213a on the solid electrolyte layer 211 side to the surface on the negative electrode active material layer 230 side. Furthermore, the negative electrode side solid electrolyte 213b is in contact with the second main surface 211b of the solid electrolyte layer 211 and is also in contact with the negative electrode active material layer 230. This allows carrier ions such as lithium ions to pass through the negative electrode current collector 213 in the thickness direction.

[0037] With the above configuration, the negative electrode current collector 213, the solid electrolyte layer 211, and the positive electrode current collector 212 of the current collector assembly 210 are stacked in direct contact. The current collector assembly 210 has a continuous solid electrolyte (negative electrode side solid electrolyte 213b, solid electrolyte layer 211, and positive electrode side solid electrolyte 212b) extending across the negative electrode current collector 213, the solid electrolyte layer 211, and the positive electrode current collector 212. As a result, carrier ions such as lithium ions can pass through the current collector assembly 210 in the thickness direction.

[0038] As shown in FIG. 2, the positive electrode active material layer 220 contains one or more positive electrode active materials capable of occluding and releasing lithium. However, the positive electrode active material layer 220 may further contain one or more other materials such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 220 is not particularly limited, and specifically, it may be a coating method or the like.

[0039] The type of the positive electrode active material is not particularly limited, and specifically, it is a lithium-containing compound or the like. A lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements. The lithium-containing compound may further contain one or more other elements as constituent elements. The type of the other element is not particularly limited as long as it is an element other than each of the lithium and transition metal elements, and specific examples thereof are elements belonging to any one of Groups 2 to 15 in the long-period type periodic table.

[0040] The type of the lithium-containing compound is not particularly limited, and specific examples thereof include oxides, phosphate compounds, silicate compounds, and borate compounds. Specific examples of the oxide are LiNiO ２ , LiCoO ２ , LiCo ０．９８ Al ０．０１ Mg ０．０１ O ２ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ , Li １．２ Mn ０．５２ Co ０．１７５ Ni ０．１ O ２ , Li １．１５ Mn ０．６５ Ni ０．２２ Co ０．１３ O ２ and LiMnO ２ O ４ and the like. Specific examples of the phosphate compound are LiFePO４ LiMnPO ４ LiFe ０．５ Mn ０．５ PO ４ and LiFe ０．３ Mn ０．７ PO ４ And so on.

[0041] The positive electrode binder contains one or more types of synthetic rubber and polymer compounds. Specific examples of synthetic rubber include styrene-butadiene rubber, fluorine-based rubber, and ethylene-propylenediene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethylcellulose.

[0042] The positive electrode conductive agent contains one or more conductive materials, such as carbon materials. Specific examples of carbon materials include graphite, carbon black, acetylene black, and Ketjenblack. However, the conductive material may also be a metallic material or a polymer compound.

[0043] The negative electrode active material layer 230 contains one or more negative electrode active materials capable of intercalating and deintercalating lithium. However, the negative electrode active material layer 230 may further contain one or more other materials such as a negative electrode binder and a negative electrode conductive agent. The method for forming the negative electrode active material layer 230 is not particularly limited and may be a coating method, for example.

[0044] The type of negative electrode active material is not particularly limited, and specifically, it may be one or both of carbon materials and metallic materials. This allows for high energy density to be obtained. Specific examples of carbon materials include easily graphitizable carbon, poorly graphitizable carbon, and graphite such as natural graphite and artificial graphite. Metallic materials are materials that contain elements capable of forming alloys with lithium, and which are either metallic elements or metalloid elements, with specific examples being silicon and tin. Metallic materials may be one or more of elements, alloys, and compounds, or they may be mixtures or materials containing two or more phases. A specific example of a metallic material is TiSi ２ and SiO ｘ (e.g., 0 < x ≤ 2).

[0045] The negative electrode binder can be made from the same material as the positive electrode binder. Similarly, the negative electrode conductive agent can be made from the same material as the positive electrode conductive agent.

[0046] As described above, in this embodiment, the secondary battery 1 is stacked in the following order in a direction perpendicular to the first main surface 211a: negative electrode active material layer 230, negative electrode current collector 213, solid electrolyte layer 211, positive electrode current collector 212, and positive electrode active material layer 220. The positive electrode current collector 212 of the current collector assembly 210 includes a positive electrode conductive layer 212a having a plurality of pores and a positive electrode side solid electrolyte 212b filling the pores of the positive electrode conductive layer 212a. The negative electrode current collector 213 includes a negative electrode conductive layer 213a having a plurality of pores and a negative electrode side solid electrolyte 213b filling the pores of the negative electrode conductive layer 213a.

[0047] This allows carrier ions such as lithium ions to pass through the stacking direction of the current collector assembly 210. In other words, during charging and discharging of the secondary battery 1, carrier ions can move between the positive electrode active material layer 220 and the negative electrode active material layer 230 via a path through the current collector assembly 210 (negative electrode current collector 213, solid electrolyte layer 211, and positive electrode current collector 212). Furthermore, the secondary battery 1 allows carrier ions to move between adjacent unit solid batteries 10 separated by the solid electrolyte layer 211A.

[0048] Therefore, compared to a configuration in which the negative electrode current collector 213, negative electrode active material layer 230, solid electrolyte layer 211, positive electrode active material layer 220, and positive electrode current collector 212 are stacked in the order perpendicular to the first main surface 211a, the secondary battery 1 of this embodiment can shorten the diffusion distance of carrier ions in the charge-discharge reaction, and increase the current that can flow under diffusion resistance-limited rate. As a result, even when charging and discharging are performed at a high rate with a large current compared to an all-solid-state battery in which the positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer are sandwiched between the positive electrode current collector and the negative electrode current collector, it is possible to suppress the uneven distribution of lithium ion concentration between the positive and negative electrodes, and to suppress the generation of irreversible capacity due to the generation of metallic lithium, etc. Therefore, the secondary battery 1 having the current collector assembly 210 according to the first embodiment can improve the charge-discharge characteristics at high rates.

[0049] At least one of the solid electrolyte layers 211, 211A, the positive electrode solid electrolyte 212b, and the negative electrode solid electrolyte 213b may be a gel electrolyte in which an electrolyte solution is impregnated into the surface of a solid electrolyte made of the above-mentioned material. The electrolyte solution is a non-aqueous electrolyte solution containing an electrolyte salt and a solvent that dissolves this electrolyte salt.

[0050] Electrolyte salts include, for example, lithium perchlorate (LiClO2). ４ ), lithium hexafluoride phosphate (LiPF) ６ ), lithium tetrafluoroborate (LiBF ４ ), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO) ２ CF ３ ) ２ ), lithium bis(pentafluoroethanesulfonyl)imide (LiN(SO) ２ C ２ F ５ ) ２ ), lithium hexafluoroarsenate (LiAsF ６ Contains lithium salts such as ).

[0051] The solvents include, for example, lactone-based solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone; carbonate ester-based solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate; ether-based solvents such as 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2-diethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; nitrile-based solvents such as acetonitrile; sulforane-based solvents; phosphoric acids; phosphoric acid ester solvents; and non-aqueous solvents including pyrrolidones.

[0052] The electrolyte preferably contains at least one additive from among fluorinated carboxylic acid esters, sulfonic acid esters, sulfonic acid anhydrides, and carboxylic acid anhydrides. This promotes the formation of low-resistance SEI (Solid Electrolyte Interphase), thereby improving the charging load characteristics. Examples of fluorinated carboxylic acid esters include fluoroethylene carbonate (FEC). Examples of sulfonic acid anhydrides include propanedisulfonic acid anhydride (PSAH). Examples of sulfonic acid esters include 1,3-propanesultone. Examples of carboxylic acid anhydrides include 1,4-dioxan-2,6-dione.

[0053] (Method for Manufacturing a Secondary Battery) Figure 4 is an explanatory diagram illustrating an example of a method for manufacturing a secondary battery according to the first embodiment. As shown in Figure 4, a green sheet 260 is formed by coating solid electrolyte layers 211 and 211A onto a support substrate 250 (step ST1). In the example shown in Figure 4, the solid electrolyte layer 211 contained in the unit solid battery 10 and the solid electrolyte layer 211A placed between the unit solid batteries 10 are formed using the same material and in the same process.

[0054] The support substrate 250 is, for example, a release film with a release treatment applied to one surface. Specifically, a resin film made of a polymer material such as polyethylene terephthalate can be used.

[0055] The solid electrolyte layers 211 and 211A can be formed by coating using printing methods such as screen printing and gravure printing. In printing the solid electrolyte layers 211 and 211A, for example, a paste for solid electrolyte layers containing a solid electrolyte material, a binder, a sintering aid, an organic material, and a solvent can be used.

[0056] Next, the green sheet 260 is cut to separate it into a positive electrode green sheet 260A and a negative electrode green sheet 260B (step ST2).

[0057] The positive electrode current collector 212 and the positive electrode active material layer 220 are laminated in this order on the solid electrolyte layer 211 of the positive electrode green sheet 260A (step ST3). The positive electrode current collector 212 and the positive electrode active material layer 220 can be formed by printing in the same way as the solid electrolyte layer 211. For printing the positive electrode current collector 212, for example, a paste for the positive electrode current collector containing an electronically conductive material such as carbon nanotubes, a solid electrolyte material, a binder, a sintering aid, and a solvent can be used. For printing the positive electrode active material layer 220, for example, a paste for the positive electrode containing a positive electrode active material, an electronically conductive material, a solid electrolyte material, a binder, a sintering aid, and a solvent can be used.

[0058] The negative electrode active material layer 230 and the negative electrode current collector 213 are laminated in this order on the solid electrolyte layer 211A of the negative electrode green sheet 260B (step ST4). The negative electrode active material layer 230 and the negative electrode current collector 213 can be formed by printing in the same way as the solid electrolyte layer 211A. For printing the negative electrode active material layer 230, for example, a negative electrode paste containing a negative electrode active material, an electronically conductive material, a solid electrolyte material, a binder, a sintering aid, and a solvent can be used. For printing the negative electrode current collector 213, for example, a negative electrode current collector paste containing an electronically conductive material such as carbon nanotubes, a solid electrolyte material, a binder, a sintering aid, and a solvent can be used.

[0059] The pastes applied in steps ST3 and ST4 are dried on a hot plate heated to 30°C to 50°C. This forms a positive electrode green sheet 260A and a negative electrode green sheet 260B having a predetermined shape and thickness on the support substrate 250 (e.g., PET film).

[0060] Next, each green sheet is peeled off from the support substrate 250 to obtain a positive electrode green sheet 260A containing a solid electrolyte layer 211, a positive electrode current collector 212, and a positive electrode active material layer 220, and a negative electrode green sheet 260B containing a solid electrolyte layer 211A, a negative electrode active material layer 230, and a negative electrode current collector 213. In Figure 4, one positive electrode green sheet 260A and one negative electrode green sheet 260B are shown, but a large number of positive electrode green sheets 260A and negative electrode green sheets 260B are formed. By alternately stacking these positive electrode green sheets 260A and negative electrode green sheets 260B, a laminate containing multiple unit solid-state batteries 10 is obtained (step ST5).

[0061] A laminate containing multiple solid-state batteries 10 is press-molded at a predetermined pressure and then fired. In one example, the firing of the laminate is carried out by removing excess binder in a nitrogen gas atmosphere containing oxygen gas or in air at, for example, 500°C, and then heating in a nitrogen gas atmosphere or in air at, for example, between 500°C and 1500°C. The firing may be carried out while pressurizing the laminate.

[0062] The secondary battery 1 (electrode body 200) can be manufactured through the process described above. Note that the process shown in Figure 4 is merely an example and can be modified as appropriate.

[0063] (Second Embodiment) Figure 5 is a cross-sectional view showing a current collector assembly according to the second embodiment. As shown in Figure 5, the current collector assembly 210A according to the second embodiment differs from the first embodiment described above in that the solid electrolyte layer 211 includes a plurality of insulating materials 215.

[0064] The multiple insulating materials 215 can be, for example, aluminum oxide, titanium oxide, zirconium oxide, silicon oxide, magnesium oxide, barium titanate, glass fiber, zeolite, lithium nitride, aluminum nitride, lithium chloride, and metal halides such as lithium bromide. If the multiple insulating materials 215 are particles, the particle size is, for example, about 1 μm to 5 μm.

[0065] As a result, in the second embodiment, it is possible to suppress short circuits between the positive electrode current collector 212 and the negative electrode current collector 213.

[0066] (Third Embodiment) Figure 6 is a cross-sectional view showing a current collector assembly according to the third embodiment. As shown in Figure 6, the current collector assembly 210B according to the third embodiment differs from the first and second embodiments described above in that the solid electrolyte layer 211B includes a first solid electrolyte layer 216 and a second solid electrolyte layer 217 containing a material with a lower reduction potential than the first solid electrolyte layer 216.

[0067] In this embodiment, the first solid electrolyte layer 216 has a relatively high oxidation potential (for example, 2.0 V (vsLi / Li) ＋ It may be formed by including a material having an oxidation potential of ) or more. The negative electrode active material layer 230, negative electrode current collector 213, second solid electrolyte layer 217, first solid electrolyte layer 216, positive electrode current collector 212, and positive electrode active material layer 220 are stacked in the order of negative electrode active material layer 230, negative electrode current collector 213, second solid electrolyte layer 217, first solid electrolyte layer 216, positive electrode current collector 212, and positive electrode active material layer 220 in a direction perpendicular to the first main surface 211a of the solid electrolyte layer 211B. That is, the second solid electrolyte layer 217 is positioned on the negative electrode current collector 213 side, and the first solid electrolyte layer 216, which has an oxidation potential greater than or equal to that of the second solid electrolyte layer 217, is positioned on the positive electrode current collector 212 side.

[0068] A combination of materials for the first solid electrolyte layer 216 and the second solid electrolyte layer 217, which have relatively high oxidation potentials, is, for example, Li ３ BO ３ and Li ７ La ３ Zr ２ O １２、 Li ３ InCl ６ and Li ３ YCl ６ LiNbo ３ and Li ６ PS ５ Cl is used.

[0069] This suppresses the occurrence of side reactions caused by oxidation of the solid electrolyte on the positive electrode side. As a result, degradation of the solid electrolyte layer 211B can be suppressed during charging and discharging of the secondary battery 1. Consequently, the secondary battery 1, which is an all-solid-state battery, can be operated stably, improving its reliability.

[0070] Furthermore, the second solid electrolyte layer 217 has a relatively low reduction potential (for example, 2.0 V (vs Li / Li) ＋ The material may include the following: The first solid electrolyte layer 216 is located on the positive electrode current collector 212 side, and the second solid electrolyte layer 217, which has a reduction potential less than or equal to the reduction potential of the first solid electrolyte layer 216, is located on the negative electrode current collector 213 side.

[0071] This suppresses the occurrence of side reactions caused by the reduction of the solid electrolyte on the negative electrode side. As a result, degradation of the solid electrolyte layer 211B can be suppressed during charging and discharging of the secondary battery 1. Consequently, the secondary battery 1, which is an all-solid-state battery, can be operated stably, improving its reliability.

[0072] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention may be modified or improved without departing from its spirit, and equivalents thereof are also included.

[0073] 1 Secondary battery 10 Unit solid battery 20 Battery element 21 Positive electrode lead 22 Negative electrode lead 30 Outer material 30a, 30b Outer sheet 31 Recess 32 Adhesive material 200 Electrode body 210, 210A, 210B Current collector assembly 211, 211A, 211B Solid electrolyte layer 212 Positive electrode current collector 212a Positive electrode conductive layer 212b Positive electrode side solid electrolyte 213 Negative electrode current collector 213a Negative electrode conductive layer 213b Negative electrode side solid electrolyte 215 Insulating material 216 First solid electrolyte layer 217 Second solid electrolyte layer 220 Positive electrode active material layer 230 Negative electrode active material layer

Claims

1. A secondary battery comprising: a solid electrolyte layer having a first main surface and a second main surface opposite to the first main surface; a positive electrode current collector provided on the first main surface; a positive electrode active material layer provided on the positive electrode current collector; a negative electrode current collector provided on the second main surface; and a negative electrode active material layer provided on the negative electrode current collector, wherein the negative electrode active material layer, the negative electrode current collector, the solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer are stacked in the order of the negative electrode active material layer, the negative electrode current collector, the solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer in a direction perpendicular to the first main surface.

2. The secondary battery according to claim 1, wherein the positive electrode current collector comprises a positive electrode conductive layer having a plurality of pores and a positive electrode side solid electrolyte filled in the pores of the positive electrode conductive layer, and the negative electrode current collector comprises a negative electrode conductive layer having a plurality of pores and a negative electrode side solid electrolyte filled in the pores of the negative electrode conductive layer.

3. The secondary battery according to claim 1 or claim 2, wherein the solid electrolyte layer comprises a plurality of insulating materials.

4. The secondary battery according to any one of claims 1 to 3, wherein the solid electrolyte layer comprises a first solid electrolyte layer and a second solid electrolyte layer having a reduction potential less than or equal to the reduction potential of the first solid electrolyte layer, and is stacked in the order of the negative electrode active material layer, the negative electrode current collector, the second solid electrolyte layer, the first solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer in a direction perpendicular to the first main surface.

5. The secondary battery according to any one of claims 1 to 3, wherein the solid electrolyte layer comprises a second solid electrolyte layer and a first solid electrolyte layer having an oxidation potential equal to or greater than the oxidation potential of the second solid electrolyte layer, and the negative electrode active material layer, the negative electrode current collector, the second solid electrolyte layer, the first solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer are stacked in the order of the negative electrode active material layer, the negative electrode current collector, the second solid electrolyte layer, the first solid electrolyte layer, the positive electrode current collector, and the positive electrode active material layer in a direction perpendicular to the first main surface.

6. The secondary battery according to any one of claims 1 to 5, wherein the solid electrolyte layer has lithium ion conductivity.

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